Showing 1–48 of 48 results for author: Samal, P

Physically motivated iso-orbital indicator for meta-GGA exchange functionals

Authors: Jeet Sharma, Abhishek Bhattacharjee, Bikash Patra, Prasanjit Samal

Abstract: The iso-orbital indicator $α= (τ- τ^\mathrm{vW})/τ^\mathrm{UEG}$ is a key ingredient of meta-generalized gradient approximation (meta-GGA) functionals, but diverges in low-density tails , causing unphysical exchange potentials and systematic band gap errors as noted in [J. Chem. Phys. 150, 161101 (2019)]. We replace the denominator of $α$ with a physically motivated Pauli KED drawn from the orbita… ▽ More The iso-orbital indicator $α= (τ- τ^\mathrm{vW})/τ^\mathrm{UEG}$ is a key ingredient of meta-generalized gradient approximation (meta-GGA) functionals, but diverges in low-density tails , causing unphysical exchange potentials and systematic band gap errors as noted in [J. Chem. Phys. 150, 161101 (2019)]. We replace the denominator of $α$ with a physically motivated Pauli KED drawn from the orbital-free DFT literature, eliminating the divergence in the low density atomic tail without any empirical regularization parameter. Testing two such enhancement factors: LKT and PGS, within the r$^2$SCAN and MS2 exchange functionals, we find that the modified indicators suppress spurious oscillations in the semilocal exchange potential and restore correct electron localization in atomic tails. For a ten-member cubic semiconductor benchmark, the band gap mean absolute error is reduced by 41.1 % for r$^2$SCAN@PGS and 48.8 % for MS2@PGS, while cohesive energy accuracy is largely preserved. The consistent improvement across two functionals with distinct constructions confirms a physical rather than functional specific origin, and motivates further development of meta-GGA functionals with constraint satisfying iso-orbital indicators. △ Less

Submitted 20 July, 2026; originally announced July 2026.

Comments: 11 pages, 9 Figures

Symmetry-Engineered Nonlinear Hall Response and Optical Response in Strained Monolayer Janus AsTeBr

Authors: Dimple Rani, Ritesh Ranjan Badhai, Gayatri Panda, Subrata Jana, Prasanjit Samal

Abstract: The nonlinear Hall effect (NLHE) enables the generation of a transverse charge current in nonmagnetic materials with broken inversion symmetry while preserving time-reversal symmetry through the Berry curvature dipole (BCD). However, in crystals with $C_{3v}$ symmetry, the threefold rotational symmetry forces the BCD to vanish, thereby suppressing the intrinsic NLHE despite the presence of finite… ▽ More The nonlinear Hall effect (NLHE) enables the generation of a transverse charge current in nonmagnetic materials with broken inversion symmetry while preserving time-reversal symmetry through the Berry curvature dipole (BCD). However, in crystals with $C_{3v}$ symmetry, the threefold rotational symmetry forces the BCD to vanish, thereby suppressing the intrinsic NLHE despite the presence of finite local Berry curvature. Here, using first-principles density functional theory combined with Wannier-based transport calculations, we demonstrate that uniaxial strain induces the NLHE in monolayer Janus AsTeBr by lowering the crystal symmetry from $C_{3v}$ to $C_{1}$ and generating a finite BCD. The resulting anisotropic redistribution of Berry-curvature hotspots produces pronounced nonlinear Hall conductivity and nonlinear Hall current, with the maximum response obtained at 2\% tensile strain. To elucidate the accompanying electronic-structure evolution, we further investigate the strain-dependent optical properties through the joint density of states, dielectric function, optical absorption, and reflectance. The optical spectra exhibit a systematic red shift and enhanced low-energy interband transitions, consistent with the strain-induced reconstruction of the electronic structure. Our results establish a microscopic connection between symmetry breaking, Berry-phase geometry, nonlinear Hall transport, and optical response, demonstrating that uniaxial strain provides an effective strategy for tailoring multiple functional properties in Janus two-dimensional materials. △ Less

Submitted 19 July, 2026; originally announced July 2026.

Comments: 11 pages, 13 figures

A Unified Dielectric-Dependent Hybrid Functional for Accurate Band Gaps across Dimensions

Authors: Subrata Jana, Manoar Hossain, Arghya Ghosh, Gabriel Chirchir, Prasanjit Samal, Szymon Smiga

Abstract: Predicting fundamental band gaps across material classes and dimensionalities remains a central challenge in electronic-structure theory. Here, we show that intrinsic dielectric screening provides a unified control parameter for nonlocal exchange from bulk to low-dimensional and heterogeneous materials. We introduce a geometry-independent dielectric response and incorporate it self-consistently in… ▽ More Predicting fundamental band gaps across material classes and dimensionalities remains a central challenge in electronic-structure theory. Here, we show that intrinsic dielectric screening provides a unified control parameter for nonlocal exchange from bulk to low-dimensional and heterogeneous materials. We introduce a geometry-independent dielectric response and incorporate it self-consistently into a nonempirical screened-dielectric-dependent hybrid functional. Benchmarks for 100 materials spanning bulk, two-dimensional, one-dimensional, and mixed-dimensional systems show near-GW accuracy at the computational cost of generalized Kohn-Sham theory. These results reveal a screening-exchange-gap relation in which reduced dimensionality weakens intrinsic dielectric screening, strengthens nonlocal exchange, and drives the opening of fundamental gaps. △ Less

Submitted 13 June, 2026; originally announced June 2026.

Comments: 6 pages, 2 figures

Nonlocal Orbital-Free Kinetic Energy Functional from the Jellium-with-Gap Model for Finite Systems

Authors: Abhishek Bhattacharjee, Subrata Jana, Szymon Smiga, Prasanjit Samal

Abstract: The quasi-linear scaling of orbital-free density functional theory (OF-DFT) with system size makes it a computationally efficient alternative to conventional Kohn--Sham density functional theory for many condensed-matter applications. However, its applicability remains limited, particularly for finite systems such as molecular clusters, due to the lack of accurate kinetic energy density functional… ▽ More The quasi-linear scaling of orbital-free density functional theory (OF-DFT) with system size makes it a computationally efficient alternative to conventional Kohn--Sham density functional theory for many condensed-matter applications. However, its applicability remains limited, particularly for finite systems such as molecular clusters, due to the lack of accurate kinetic energy density functionals. In this context, the development of nonlocal kinetic energy density functionals (NL-KEDFs) has significantly advanced the practical utility of OF-DFT. Here, following an alternative formulation based on the linear-response kernel derived from the jellium-with-gap model (JGM), we develop an NL-KEDF capable of accurately describing the diverse density regimes characteristic of finite systems, including molecular clusters. Benchmark calculations, together with an analysis of the corresponding Pauli potentials, demonstrate that the proposed functional achieves higher accuracy than state-of-the-art orbital-free approaches for finite systems. Furthermore, the optical properties computed using the present method show good agreement with reference results, highlighting its reliability. These results indicate that the proposed NL-KEDF provides a robust and efficient framework for extending OF-DFT to finite systems, with potential implications for nanomaterial design and a deeper understanding of nanoscale phenomena. △ Less

Submitted 13 June, 2026; originally announced June 2026.

Comments: Accepted in J. Chem. Theory Comput. (2026)

Supercurrent spin Hall effect enabled nanopillar Josephson diodes

Authors: Debashree Nayak, Dimple Rani, Prasanjit Samal, Kartik Senapati

Abstract: In the recent years it has been possible to achieve diode-like, non-reciprocal current-voltage response in Josephson junctions, despite the intrinsic symmetry of the Josephson effect itself. This is typically achieved by incorporating Rashba spin-orbit coupling into the Josephson junction as a strong inversion symmetry breaking component, and external magnetic field as a tuneable time-reversal sym… ▽ More In the recent years it has been possible to achieve diode-like, non-reciprocal current-voltage response in Josephson junctions, despite the intrinsic symmetry of the Josephson effect itself. This is typically achieved by incorporating Rashba spin-orbit coupling into the Josephson junction as a strong inversion symmetry breaking component, and external magnetic field as a tuneable time-reversal symmetry breaking component. However, the efficiencies of the external field tuneable Josephson-diodes have remained limited to less than 10 \%, often measured below 100 mK temperature. In this work we take a new approach where non-reciprocity is induced by intrinsic SOC in a heavy metal Josephson barrier via the predicted supercurrent spin-Hall effect. By measuring a series of Nb-Pt-Nb nanopillar junctions we demonstrated field tuneable Josephson diode efficiencies as high as 17\%, measured above liquid Helium temperature. This was possible by the realization of a net non-equilibrium spin segregation in the Pt barrier, due to the supercurrent spin-Hall effect in the Pt barrier, analogous to the normal spin-Hall effect. As the direction of the induced spin moment is determined by the bias current, an external magnetic field causes the associated phases to add with opposite signs for opposite current directions, resulting in a nonreciprocal supercurrent across the junction. △ Less

Submitted 16 May, 2026; originally announced May 2026.

Competition between clustering and dispersion of cobalt atoms on perovskite surfaces: SrTiO3(001) and KTaO3(001)

Authors: Aji Alexander, Pankaj Kumar Samal, Llorenc Albons, Jesus Redondo, Jan Skvara, Igor Pis, Lukas Fusek, Josef Myslivecek, Viktor Johanek, Dominik Wrana, Martin Setvin

Abstract: Perovskite oxides are attractive for reactions in photo/electrocatalytic schemes, and extrinsic doping is a common strategy for tuning their properties. It is widely known that extrinsic dopants impact the structure and stability of perovskite surfaces, but an atomic-scale view is missing. Here, noncontact atomic force microscopy (ncAFM) and photoelectron spectroscopy (XPS/PES) are used to combine… ▽ More Perovskite oxides are attractive for reactions in photo/electrocatalytic schemes, and extrinsic doping is a common strategy for tuning their properties. It is widely known that extrinsic dopants impact the structure and stability of perovskite surfaces, but an atomic-scale view is missing. Here, noncontact atomic force microscopy (ncAFM) and photoelectron spectroscopy (XPS/PES) are used to combine microscopic and spectroscopic evidence of cobalt adsorption, incorporation, and clustering at surfaces of two prototypical perovskites SrTiO3 and KTaO3. A number of different sub-ML coverages and temperatures of annealing were investigated. Several common features are observed: cobalt shows a strong preference for ionic nature (+2 and +3 charge states), and remains dispersed as single atoms to a certain extent in both perovskites. Two competing mechanisms are observed upon annealing: coalescence into clusters with a mixed metallic/ionic character, and incorporation into the surface and subsurface regions. The latter is more pronounced in SrTiO3, where a cobalt-stabilized surface reconstruction is identified, whereas for KTaO3 cobalt likely incorporates in the near-surface region. △ Less

Submitted 21 January, 2026; originally announced January 2026.

Kinetic energy constructed from exact gradient expansion of second order in uniform gas limit

Authors: Abhishek Bhattacharjee, Hemanadhan Myneni, Manoj K. Harbola, Prasanjit Samal

Abstract: Orbital-Free Density Functional Theory (OFDFT) has re-emerged as a viable alternative to Kohn-Sham DFT, driven by recent advances in kinetic energy density functionals (KEDFs). Nonlocal (NL) KEDFs have significantly extended OFDFT's applicability, particularly for bulk solids, but their high computational cost and dependence of system-specific parameters limit their universality. In this work, we… ▽ More Orbital-Free Density Functional Theory (OFDFT) has re-emerged as a viable alternative to Kohn-Sham DFT, driven by recent advances in kinetic energy density functionals (KEDFs). Nonlocal (NL) KEDFs have significantly extended OFDFT's applicability, particularly for bulk solids, but their high computational cost and dependence of system-specific parameters limit their universality. In this work, we propose a semilocal KEDF at the Generalized Gradient Approximation (GGA) level that achieves accuracy comparable to state-of-the-art NL and meta-GGA functionals, while remaining entirely parameter-free. Our construction revives the Thomas-Fermi-von Weizsacker (TFvW) framework by modulating the relative contributions of TF and vW terms through physically motivated constraints and preserving the exact second-order gradient expansion. Despite its simple form, the proposed functional (KGE2) performs remarkably well across both extended systems (metals and semiconductors) and finite systems (clusters), without any need for parameter tuning. These results mark a step toward a transferable, computationally efficient, and general-purpose KEDF suitable for large-scale OFDFT simulations. △ Less

Submitted 23 December, 2025; originally announced December 2025.

Comments: 15 pages, 9 figures

Electric-Field and Doping-Induced Non collinear Magnetic Interactions in Monolayer Ti$_2$Si

Authors: Dimple Rani, Gayatri Panda, Subrata Jana, Prasanjit Samal

Abstract: Two-dimensional (2D) silicides are an emerging class of materials whose magnetic and relativistic properties remain largely unexplored. Using first-principles calculations, we investigate how electric-field modulation and transition-metal doping influence the magnetic exchange, magnetocrystalline anisotropy, and antisymmetric Dzyaloshinskii-Moriya interaction (DMI) in monolayer Ti2Si. Pristine Ti2… ▽ More Two-dimensional (2D) silicides are an emerging class of materials whose magnetic and relativistic properties remain largely unexplored. Using first-principles calculations, we investigate how electric-field modulation and transition-metal doping influence the magnetic exchange, magnetocrystalline anisotropy, and antisymmetric Dzyaloshinskii-Moriya interaction (DMI) in monolayer Ti2Si. Pristine Ti2Si is a dynamically stable ferromagnetic metal with in-plane anisotropy and centrosymmetric bonding, which suppresses DMI even under strong perpendicular electric fields. To overcome this symmetry constraint, we introduce Pt and Co substitution at Ti sites. Co enhances the magnetic exchange, whereas Pt provides strong spin orbit coupling (SOC), and the combined chemical asymmetry breaks inversion symmetry sufficiently to induce a sizable DMI. A Wannier-based tight-binding model captures the orbital-resolved superexchange pathways and reveals a clear hierarchy between a weak Si-mediated channel and a dominant Pt-mediated interlayer channel. First-principles calculations confirm that the Pt-assisted pathway governs the magnitude and sign of the total DMI. Among all configurations, Pt0.5CoTi0.5Si exhibits the strongest chiral interaction, with its intralayer and interlayer contributions favoring opposite rotation senses, namely counterclockwise (CCW) and clockwise (CW). Our results establish chemically engineered Ti2Si monolayers as a promising platform for realizing and tuning chiral magnetic textures in 2D silicides. △ Less

Submitted 2 December, 2025; originally announced December 2025.

First Principles study of Photocatalytic Water Splitting in BO Monolayer: Effect of Strain and Surface Functionalization

Authors: Soumendra Kumar Das, Smruti Ranjan Parida, Prasanjit Samal, Brahmananda Chakraborty, Sridhar Sahu

Abstract: Light element based two dimensional (2D) materials are promising photocatalysts for hydrogen production via water splitting. Boron oxide (BO) is a recently synthesized 2D monolayer which has yet to be thoroughly explored for its potential applications. In this article, using first principles calculations, we report, for the first time, the visible-light photocatalytic activity of a BO monolayer fo… ▽ More Light element based two dimensional (2D) materials are promising photocatalysts for hydrogen production via water splitting. Boron oxide (BO) is a recently synthesized 2D monolayer which has yet to be thoroughly explored for its potential applications. In this article, using first principles calculations, we report, for the first time, the visible-light photocatalytic activity of a BO monolayer for water splitting under mechanical strain and surface modification with single- and double-atom decorations (C, N, Si, Ge, P, As). The pristine BO monolayer exhibits an indirect band gap of 3.8 eV with band edges spanning the water redox potentials, but its optical absorption lies in the UV region (~ 4.5 eV). Strain engineering tunes the band gap and band alignment with a minimal shifting in the optical absorption (~0.5 eV). Single atom decoration produces a metallic state for elements like N, P, As, and an insulating state for single C, Si, Ge with a partial shifting in optical absorption. In contrast, double atom decoration produces substantial band gap reduction, improved band alignment, a pronounced red-shift in optical absorption into the visible range (1.6 to 3.2 eV) thus satisfying the criteria for water splitting. The stability of all the adsorbed configurations was confirmed by negative formation energy and ab-initio molecular dynamics simulations. These findings suggest BO monolayer functionalization can improve photocatalytic efficiency, providing hydrogen generation insights. △ Less

Submitted 17 November, 2025; originally announced November 2025.

Unraveling the Surface Stability and Chemical Reactivity of Aza-Triphenylene Monolayer under O$_2$ and H$_2$O Exposure

Authors: Soumendra Kumar Das, Prasanjit Samal, Brahmananda Chakraborty, Sridhar Sahu

Abstract: Environmental oxidation has a great impact in tuning the physical, chemical and electronic properties of two-dimensional (2D) monolayers which can affect their practical applications in nanoscale engineering devices under ambient conditions. aza-triphenylene is a recently synthesized 2D materials whose practcal applications have not been systematically studied yet. In this study, we report for the… ▽ More Environmental oxidation has a great impact in tuning the physical, chemical and electronic properties of two-dimensional (2D) monolayers which can affect their practical applications in nanoscale engineering devices under ambient conditions. aza-triphenylene is a recently synthesized 2D materials whose practcal applications have not been systematically studied yet. In this study, we report for the first time, the adsorption and dissociation of O$_2$ and H$_2$O molecules on the surface of 2D aza-triphenylene monolayer through first principles calculations in combination with climbing image nudged elastic band (CINEB) method. The results indicates that both the O$_2$ and H$_2$O molecules weakly interact over the monolayer surface with an adsorption energy -0.16 eV and -0.37 eV respectively. In contrast, both the molecules exhibit resistance for dissociation due to the formation of energy barriers. The transition path indicates that molecular oxygen experience two energy barriers (0.16 ev and 1.22 eV) before getting dissociated atomic oxygen. However, the dissociation of H$_2$O requires larger energy barrier (2.3 eV and 0.86 eV) due to breaking of covalent bonds and transfer of hydrogen. The strong chemical adsorption of atomic oxygen and H$^+$/OH$^-$ ions is due to the significant charge transfer from monolayer to the adsorbate as evidenced from the charge density difference and Bader charge analysis. Moreover, the dissociated configuration exhibit a larger band gap as compared to the pristine aza-triphenylene due to the strong hybridization between the p states of carbon and oxygen. our work predicts the robustness of azatriphylene monolayer against oxygen/water exposer thus ensuring their stability for device applications using these materials. △ Less

Submitted 16 November, 2025; originally announced November 2025.

Strain and Correlation Modulated Magnetic Anisotropy and Dzyaloshinskii--Moriya Interaction in 2D H-FeTe$_2$

Authors: Dimple Rani, B. R. K. Nanda, Prasanjit Samal

Abstract: In the ongoing research on two-dimensional (2D) ferromagnetic materials with strong intrinsic Dzyaloshinskii--Moriya interaction (DMI), most efforts have focused on doping, Janus engineering, or heterostructure formation to break inversion symmetry and enhance spin--orbit coupling (SOC). Here, we demonstrate that a pristine 2D material, monolayer H-FeTe$_2$, can naturally host robust DMI and magne… ▽ More In the ongoing research on two-dimensional (2D) ferromagnetic materials with strong intrinsic Dzyaloshinskii--Moriya interaction (DMI), most efforts have focused on doping, Janus engineering, or heterostructure formation to break inversion symmetry and enhance spin--orbit coupling (SOC). Here, we demonstrate that a pristine 2D material, monolayer H-FeTe$_2$, can naturally host robust DMI and magnetic anisotropy due to its intrinsic broken inversion symmetry and the strong SOC of Te atoms. We explore the effect of biaxial strain and electron correlation on H-FeTe$_2$ using first-principles DFT+$U$ calculations. We systematically investigate the Heisenberg exchange interaction, magnetic anisotropy, and DMI in the space spanned by strain and correlation. Our results reveal a distinct, non-monotonic strain dependence of both magnetic anisotropy energy (MAE) and DMI, including a strain-tunable crossover between in-plane and out-of-plane magnetic easy axes. A remarkable enhancement of the in-plane DMI is observed under the combined influence of strain and strong correlations, which is unusual for pristine 2D materials and suggests a favorable regime for spintronic applications.Notably, even in the absence of strain, H-FeTe$_2$ exhibits finite DMI and considerable anisotropy, which is rare for a pure 2D material. Through these findings, we present H-FeTe$_2$ as a unique pristine 2D system with robust and tunable spin interactions for exploring fundamental spin--orbit-driven magnetic phenomena. △ Less

Submitted 14 July, 2025; originally announced July 2025.

Advancing excited-state properties of two-dimensional materials using a dielectric-dependent hybrid functional

Authors: Arghya Ghosh, Subrata Jana, Manoar Hossain, Dimple Rani, Szymon Śmiga, Prasanjit Samal

Abstract: Predicting accurate band gaps and optical properties of lower-dimensional materials, including two-dimensional van der Waals (vdW) materials and their heterostructures, remains a challenge within density functional theory (DFT) due to their unique screening compared to their bulk counterparts. Additionally, accurate treatment of the dielectric response is crucial for developing and applying screen… ▽ More Predicting accurate band gaps and optical properties of lower-dimensional materials, including two-dimensional van der Waals (vdW) materials and their heterostructures, remains a challenge within density functional theory (DFT) due to their unique screening compared to their bulk counterparts. Additionally, accurate treatment of the dielectric response is crucial for developing and applying screened-exchange dielectric-dependent range-separated hybrid functionals (SE-DD-RSH) for vdW materials. In this work, we introduce a SE-DD-RSH functional to the 2D vdW materials like MoS2, WS2, hBN, black phosphorus (BP), and \b{eta}-InSe. By accounting for in-plane and out-of-plane dielectric responses, our method achieves accuracy comparable to advanced many-body techniques like G0 W0 and BSE@G0 W0 at a lower computational cost. We demonstrate improved band gap predictions and optical absorption spectra for both bulk and layered structures, including some heterostructures like MoS2/WS2 . This approach offers a practical and precise tool for exploring electronic and optical phenomena in 2D materials, paving the way for efficient computational studies of layered systems. △ Less

Submitted 23 July, 2025; v1 submitted 22 May, 2025; originally announced May 2025.

Comments: 21 pages 7 Figures

Journal ref: Phys. Rev. B 112, 045128 (2025)

Meta-GGA dielectric-dependent and range-separated screened hybrid functional for reliable prediction of material properties

Authors: Subrata Jana, Abhishek Bhattacharjee, Suman Mahakal, Szymon Smiga, Prasanjit Samal

Abstract: We propose a range-separated hybrid exchange-correlation functional to calculate solid-state material properties. The functional mixes Hartree-Fock exchange with the semilocal exchange of the meta-generalized gradient approximation (meta-GGA) and the fraction of Hartree-Fock exchange is determined from the dielectric function. First-principles calculations and comparison with other meta-GGA approx… ▽ More We propose a range-separated hybrid exchange-correlation functional to calculate solid-state material properties. The functional mixes Hartree-Fock exchange with the semilocal exchange of the meta-generalized gradient approximation (meta-GGA) and the fraction of Hartree-Fock exchange is determined from the dielectric function. First-principles calculations and comparison with other meta-GGA approximations show that the functional leads to reasonably good performance for the band gap and optical properties. We also show that the present functional also successfully resolves the well-known ``band gap problem'' of narrow gap Cu-based semiconductors, such as Cu3SbSe4 and Cu3AsSe4, where, in general, a considerably large band inversion energy leads to a ``false'' negative or metallic band gap for all other methods. Furthermore, reasonable accuracy for the occupied d-bands and transition energies is also obtained for bulk solids. Thus, overall, our results demonstrate the predictive power of range-separated meta-GGA hybrid functionals for quantum materials simulations. △ Less

Submitted 25 February, 2025; originally announced February 2025.

Journal ref: Physical Review B (2025)

An Investigation into the Thermoelectric Characteristics of Silver-based Chalcopyrites Utilizing a Non-empirical Range-separated Dielectric-dependent Hybrid Approach

Authors: Dimple Rani, Subarata Jana, Manish Kumar Niranjan, Prasanjit Samal

Abstract: Our investigation explores the intricate domain of thermoelectric phenomena within silver (Ag)-infused chalcopyrites, focusing on compositions such as AgXTe$_2$ (where X=Ga, In) and the complex quaternary system Ag$_2$ZnSn/GeY$_2$ (with Y=S, Se). Using a sophisticated combination of methodologies, we integrate a non-empirical screened dielectric-dependent hybrid (DDH) functional with semiclassical… ▽ More Our investigation explores the intricate domain of thermoelectric phenomena within silver (Ag)-infused chalcopyrites, focusing on compositions such as AgXTe$_2$ (where X=Ga, In) and the complex quaternary system Ag$_2$ZnSn/GeY$_2$ (with Y=S, Se). Using a sophisticated combination of methodologies, we integrate a non-empirical screened dielectric-dependent hybrid (DDH) functional with semiclassical Boltzmann transport theory. This approach allows us to conduct a detailed analysis of critical thermoelectric properties, including electrical conductivity, Seebeck coefficient, and power factor. Our methodology goes beyond superficial assessments, delving into the intricate interplay of material properties to reveal their true thermoelectric potential. Additionally, we investigate the often-overlooked phenomena of phonon scattering by leveraging both the elastic constant tensor and the deformation potential method. This enables a rigorous examination of electron relaxation time and lattice thermal conductivity, enhancing the robustness of our predictions and demonstrating our commitment to thorough exploration.Through our rigorous investigation, we identify materials with a thermoelectric figure of merit (ZT = $σS^{2}T/ κ$) exceeding the critical threshold of unity. This significant achievement signals the discovery of materials capable of revolutionizing efficient thermoelectric systems. Our findings delineate a promising trajectory, laying the groundwork for the emergence of a new class of Ag-based chalcopyrites distinguished by their exceptional thermoelectric characteristics. This research not only contributes to the understanding of materials science principles but also catalyzes transformative advancements in thermoelectric technology. △ Less

Submitted 6 June, 2025; v1 submitted 19 May, 2024; originally announced May 2024.

Unveiling the Reactivity of Oxygen and Ozone on C2N Monolayer: A First-Principles Study

Authors: Soumendra Kumar Das, Lokanath Patra, Prasanjit Samal, Pratap Kumar Sahoo

Abstract: The process of environmental oxidation is pivotal in determining the physical and chemical properties of two-dimensional (2D) materials. Its impact holds great significance for the practical application of these materials in nanoscale devices functioning under ambient conditions. This study delves into the influence of O2 and O3 exposure on the structural and electronic characteristics of the C2N… ▽ More The process of environmental oxidation is pivotal in determining the physical and chemical properties of two-dimensional (2D) materials. Its impact holds great significance for the practical application of these materials in nanoscale devices functioning under ambient conditions. This study delves into the influence of O2 and O3 exposure on the structural and electronic characteristics of the C2N monolayer, focusing on the kinetics of adsorption and dissociation reactions. Employing first-principles density functional theory calculations alongside climbing image nudged elastic band calculations, we observe that the C2N monolayer exhibits resistance to oxidation and ozonation, evidenced by energy barriers of 0.05 eV and 0.56 eV, respectively. These processes are accompanied by the formation of epoxide (C-O-C) groups. Furthermore, the dissociation mechanism involves charge transfers from the monolayer to the molecules. Notably, the dissociated configurations demonstrate higher bandgaps compared to the pristine C2N monolayer, attributed to robust C-O hybridization. These findings suggest the robustness of C2N monolayers against oxygen/ozone exposures, ensuring stability for devices incorporating these materials. △ Less

Submitted 19 March, 2024; originally announced March 2024.

Spin-Phonon interaction in quasi 2D- Cr$_2Te_3$

Authors: Gurupada Ghorai, Kalyan Ghosh, Abhilash Patra, Prasanjit Samal, Kartik Senapati, Pratap K. Sahoo

Abstract: Spin-phonon interaction plays an important role in 2D magnetic materials and motivates the development of next-generation spin- and charge-dependent microelectronic devices. Understanding the spin-phonon interaction by tuning the growth parameter of single crystal Cr$_2Te_3$, a robust quasi-2D room temperature magnetic material, is crucial for spintronic devices. The synthesis of single crystal 2D… ▽ More Spin-phonon interaction plays an important role in 2D magnetic materials and motivates the development of next-generation spin- and charge-dependent microelectronic devices. Understanding the spin-phonon interaction by tuning the growth parameter of single crystal Cr$_2Te_3$, a robust quasi-2D room temperature magnetic material, is crucial for spintronic devices. The synthesis of single crystal 2D Cr$_2Te_3$ flakes on a Si substrate from co-deposited thin film by plasma annealing techniques is a significant achievement. The temperature dependence and polarization-resolved Raman spectroscopy with support of density functional theory classified lattice symmetry operations were used to identify the phonon modes to investigate the spin/electron-phonon interactions in Cr$_2Te_3$. The mean-field theory model in single crystal Cr$_2Te_3$ is employed to quantify the spin-phonon interaction and correlate with in-plane and out-of-plane magnetic behavior. The observation of a positive correlation between phonon mode frequency and spin-phonon interaction strength in single crystal Cr$_2Te_3$ can be a potential candidate for spintronic applications. △ Less

Submitted 7 March, 2024; originally announced March 2024.

Accurate and efficient prediction of the band gaps and optical spectra of chalcopyrite semiconductors from a non-empirical range-separated dielectric-dependent hybrid: Comparison with many-body perturbation theory

Authors: Arghya Ghosh, Subrata Jana, Dimple Rani, Manoar Hossain, Manish K Niranjan, Prasanjit Samal

Abstract: The accurate prediction of electronic and optical properties in chalcopyrite semiconductors has been a persistent challenge for density functional theory (DFT) based approaches. Addressing this issue, we demonstrate that very accurate results can be obtained using a non-empirical screened dielectric-dependent hybrid (DDH) functional. This novel approach showcases its impressive capability to accur… ▽ More The accurate prediction of electronic and optical properties in chalcopyrite semiconductors has been a persistent challenge for density functional theory (DFT) based approaches. Addressing this issue, we demonstrate that very accurate results can be obtained using a non-empirical screened dielectric-dependent hybrid (DDH) functional. This novel approach showcases its impressive capability to accurately determine band gaps, optical bowing parameters, and optical absorption spectra for chalcopyrite systems. What sets the screened DDH functional apart is its adeptness in capturing the many-body physics associated with highly localized $d$ electrons. Notably, the accuracy is comparable to the many-body perturbation based methods (such as $G_0W_0$ or its various approximations for band gaps and Bethe-Salpeter equation (BSE) on the top of the $G_0W_0$ or its various approximations for optical spectra) with less computational cost, ensuring a more accessible application across various research domains. The present results show the predictive power of the screened DDH functional, pointing toward promising applications where computational efficiency and predictive accuracy are crucial considerations. Overall, the screened DDH functional offers a compelling balance between cost-effectiveness and precision, making it a valuable tool for future endeavors in exploring chalcopyrite semiconductors and beyond. △ Less

Submitted 30 January, 2024; originally announced January 2024.

Comments: 15 pages, 11 figures

Journal ref: Phys. Rev. B 109, 045133 (2024)

Simple and accurate screening parameters for dielectric-dependent hybrids

Authors: Subrata Jana, Arghya Ghosh, Lucian A. Constantin, Prasanjit Samal

Abstract: A simple effective screening parameter for screened range-separated hybrid is constructed from the compressibility sum rule in the context of linear-response time-dependent Density Functional Theory. When applied to the dielectric-dependent hybrid (DDH), it becomes remarkably accurate for bulk solids compared to those obtained from fitting with the model dielectric function or depending on the val… ▽ More A simple effective screening parameter for screened range-separated hybrid is constructed from the compressibility sum rule in the context of linear-response time-dependent Density Functional Theory. When applied to the dielectric-dependent hybrid (DDH), it becomes remarkably accurate for bulk solids compared to those obtained from fitting with the model dielectric function or depending on the valence electron density of materials. The present construction of the screening parameter is simple and realistic. The screening parameter developed in this way is physically appealing and practically useful as it is straightforward to obtain using the average over the unit cell volume of the bulk solid, bypassing high-level calculations of the dielectric function depending on random-phase approximation. Furthermore, we have obtained a very good accuracy for energy band gaps, positions of the occupied d-bands, ionization potentials, optical properties of semiconductors and insulators, and geometries of bulk solids (equilibrium lattice constants and bulk moduli) from the constructed DDH. △ Less

Submitted 9 March, 2023; originally announced March 2023.

Comments: 13 pages

Strain Induced Enhanced Photocatalytic Activities in Layered Two Dimensional C2N/MoS2 Heterostructure: A Meta-GGA Study

Authors: Soumendra Kumar Das, Lokanath Patra, Prasanjit Samal, Pratap K Sahoo

Abstract: The improved photocatalytic water splitting using 2D materials has technological importance for economically viable renewable energy. The present study focuses on the effect of uniaxial, biaxial, and vertical strain on the energy gap and band edge positions of C2N/MoS2 van der Waals heterostructures through first-principles density functional theory using PBE and SCAN functionals. The calculations… ▽ More The improved photocatalytic water splitting using 2D materials has technological importance for economically viable renewable energy. The present study focuses on the effect of uniaxial, biaxial, and vertical strain on the energy gap and band edge positions of C2N/MoS2 van der Waals heterostructures through first-principles density functional theory using PBE and SCAN functionals. The calculations establish that SCAN functional provides comparatively much better results as compared to the PBE for the band gap and band alignment study. The heterostructure exhibits a type- II band alignment which is beneficial for the efficient separation of charge carriers. For a good photocatalyst, the band edge positions should straddle the water redox potentials. It is observed that for both compressive and tensile vertical strain, the water redox potential values lie within the valence band maximum (VBM) and conduction band minimum (CBM) of the heterostructure. On the other hand, for uniaxial and biaxial strain, the system can be used as a useful photocatalyst only for larger compressive strain, whereas for tensile strain, the energy gap between VBM and CBM keeps on decreasing and lie within the water oxidation/reduction potential. Our study also establishes that the meta-GGA SCAN functional shows similar results as compared to the computationally expensive hybrid HSE functionals. The present work can be extremely useful for experimentalists to design artificial heterostructure devices for better performance in photocatalytic water splitting. △ Less

Submitted 10 January, 2023; originally announced January 2023.

Semilocal Meta-GGA Exchange-Correlation Approximation From Adiabatic Connection Formalism: Extent and Limitations

Authors: Subrata Jana, Szymon Smiga, Lucian A. Constantin, Prasanjit Samal

Abstract: The incorporation of a strong interaction regime within the approximate, semilocal exchange-correlation functionals still remains a very challenging task for density functional theory. One of the promising attempts in this direction is the recently proposed adiabatic connection semilocal correlation (ACSC) approach [Phys. Rev. B 2019, 99, 085117] allowing to construct the correlation energy functi… ▽ More The incorporation of a strong interaction regime within the approximate, semilocal exchange-correlation functionals still remains a very challenging task for density functional theory. One of the promising attempts in this direction is the recently proposed adiabatic connection semilocal correlation (ACSC) approach [Phys. Rev. B 2019, 99, 085117] allowing to construct the correlation energy functionals by interpolation of the high and low-density limits for the given semi-local approximation. The current study extends the ACSC method to the meta-GGA level of theory, providing some new insights. As an example, we construct the correlation energy functional base on the high and low-density limits of the Tao-Perdew-Starverov-Scuseria (TPSS) functional. Arose in this way TPSS-ACSC functional is one electron self-interaction free, accurate for the strictly correlated, and quasi-two-dimensional regimes. Based on simple examples, we show the advantages and disadvantages of ACSC semi-local functionals and provide some new guidelines for future developments in this context. △ Less

Submitted 19 September, 2023; v1 submitted 8 December, 2022; originally announced December 2022.

Comments: 13 pages

Journal ref: Journal of Physical Chemistry A (2023)

Efficient and improved prediction of the band offsets at semiconductor heterojunctions from meta-GGA density functionals

Authors: Arghya Ghosh, Subrata Jana, Tomáš Rauch, Fabien Tran, Miguel A. L. Marques, Silvana Botti, Lucian A. Constantin, Manish K. Niranjan, Prasanjit Samal

Abstract: Accurate theoretical prediction of the band offsets at interfaces of semiconductor heterostructures can often be quite challenging. Although density functional theory has been reasonably successful to carry out such calculations and efficient and accurate semilocal functionals are desirable to reduce the computational cost. In general, the semilocal functionals based on the generalized gradient ap… ▽ More Accurate theoretical prediction of the band offsets at interfaces of semiconductor heterostructures can often be quite challenging. Although density functional theory has been reasonably successful to carry out such calculations and efficient and accurate semilocal functionals are desirable to reduce the computational cost. In general, the semilocal functionals based on the generalized gradient approximation (GGA) significantly underestimate the bulk band gaps. This, in turn, results in inaccurate estimates of the band offsets at the heterointerfaces. In this paper, we investigate the performance of several advanced meta-GGA functionals in the computational prediction of band offsets at semiconductor heterojunctions. In particular, we investigate the performance of r2SCAN (revised strongly-constrained and appropriately-normed functional), rMGGAC (revised semilocal functional based on cuspless hydrogen model and Pauli kinetic energy density functional), mTASK (modified Aschebrock and Kümmel meta-GGA functional), and LMBJ (local modified Becke-Johnson) exchange-correlation functionals. Our results strongly suggest that these meta-GGA functionals for supercell calculations perform quite well, especially, when compared to computationally more demanding GW calculations. We also present band offsets calculated using ionization potentials and electron affinities, as well as band alignment via the branch point energies. Overall, our study shows that the aforementioned meta-GGA functionals can be used within the DFT framework to estimate the band offsets in semiconductor heterostructures with predictive accuracy. △ Less

Submitted 27 July, 2022; originally announced July 2022.

Correct and accurate polymorphic energy ordering of transition-metal monoxides obtained from semilocal and onsite-hybrid exchange-correlation approximations

Authors: Arghya Ghosh, Subrata Jana, Manish K Niranjan, Fabien Tran, David Wimberger, Peter Blaha, Lucian A. Constantin, Prasanjit Samal

Abstract: The relative energetic stability of the structural phases of common antiferromagnetic transition-metal oxides (MnO, FeO, CoO, and NiO) within the semilocal and hybrid density functionals are fraught with difficulties. In particular, MnO is known to be the most difficult case for almost all common semilocal and hybrid density approximations. Here, we show that the meta-generalized gradient approxim… ▽ More The relative energetic stability of the structural phases of common antiferromagnetic transition-metal oxides (MnO, FeO, CoO, and NiO) within the semilocal and hybrid density functionals are fraught with difficulties. In particular, MnO is known to be the most difficult case for almost all common semilocal and hybrid density approximations. Here, we show that the meta-generalized gradient approximation (meta-GGA) constructed from the cuspless hydrogen model and Pauli kinetic energy density (MGGAC) can lead to the correct ground state of MnO. The relative energy differences of zinc-blende (zb) and rock-salt (rs) structures as computed using MGGAC are found to be in nice agreement with those obtained from high-level correlation methods like the random phase approximation or quantum Monte Carlo techniques. Besides, we have also applied the onsite hybrid functionals (closely related to DFT+U ) based on GGA and meta-GGA functionals, and it is shown that a relatively high amount of Hartree-Fock exchange is necessary to obtain the correct ground-state structure. Our present investigation suggests that the semilocal MGGAC and onsite hybrids, both being computationally cheap, as methods of choice for the calculation of the relative stability of antiferromagnetic transition-metal oxides having potential applications in solid-state physics and structural chemistry. △ Less

Submitted 16 December, 2021; originally announced December 2021.

Bandgap of two-dimensional materials: Thorough assessment of modern exchange-correlation functionals

Authors: Fabien Tran, Jan Doumont, Leila Kalantari, Peter Blaha, Tomáš Rauch, Pedro Borlido, Silvana Botti, Miguel A. L. Marques, Abhilash Patra, Subrata Jana, Prasanjit Samal

Abstract: The density functional theory (DFT) approximations that are the most accurate for the calculation of band gap of bulk materials are hybrid functionals like HSE06, the MBJ potential, and the GLLB-SC potential. More recently, generalized gradient approximations (GGA), like HLE16, or meta-GGAs, like (m)TASK, have proven to be also quite accurate for the band gap. Here, the focus is on 2D materials an… ▽ More The density functional theory (DFT) approximations that are the most accurate for the calculation of band gap of bulk materials are hybrid functionals like HSE06, the MBJ potential, and the GLLB-SC potential. More recently, generalized gradient approximations (GGA), like HLE16, or meta-GGAs, like (m)TASK, have proven to be also quite accurate for the band gap. Here, the focus is on 2D materials and the goal is to provide a broad overview of the performance of DFT functionals by considering a large test set of 298 2D systems. The present work is an extension of our recent studies [Rauch et al., Phys. Rev. B 101, 245163 (2020) and Patra et al., J. Phys. Chem. C 125, 11206 (2021)]. Due to the lack of experimental results for the band gap of 2D systems, $G_{0}W_{0}$ results were taken as reference. It is shown that the GLLB-SC potential and mTASK functional provide the band gaps that are the closest to $G_{0}W_{0}$. Following closely, the local MBJ potential has a pretty good accuracy that is similar to the accuracy of the more expensive hybrid functional HSE06. △ Less

Submitted 3 January, 2022; v1 submitted 25 May, 2021; originally announced May 2021.

Journal ref: J. Chem. Phys. 155, 104103 (2021)

Improved electronic structure prediction of chalcopyrite semiconductors from a semilocal density functional based on Pauli kinetic energy enhancement factor

Authors: Arghya Ghosh, Subrata Jana, Manish K Niranjan, Sushant Kumar Behera, Lucian A. Constantin, Prasanjit Samal

Abstract: The correct treatment of d electrons is of prime importance in order to predict the electronic properties of the prototype chalcopyrite semiconductors. The effect of d states is linked with the anion displacement parameter u, which in turn influences the bandgap of these systems. Semilocal exchange-correlation functionals which yield good structural properties of semiconductors and insulators ofte… ▽ More The correct treatment of d electrons is of prime importance in order to predict the electronic properties of the prototype chalcopyrite semiconductors. The effect of d states is linked with the anion displacement parameter u, which in turn influences the bandgap of these systems. Semilocal exchange-correlation functionals which yield good structural properties of semiconductors and insulators often fail to predict reasonable u because of the underestimation of the bandgaps arising from the strong interplay between d electrons. In the present study, we show that the meta-generalized gradient approximation (meta-GGA) obtained from the cuspless hydrogen density (MGGAC) [Phys. Rev. B 100, 155140 (2019)] performs in an improved manner in apprehending the key features of the electronic properties of chalcopyrites, and its bandgaps are comparative to that obtained using state-of-art hybrid methods. Moreover, the present assessment also shows the importance of the Pauli kinetic energy enhancement factor, $α=(τ-τ^W)/τ^{unif}$ in describing the d electrons in chalcopyrites. The present study strongly suggests that the MGGAC functional within semilocal approximations can be a better and preferred choice to study the chalcopyrites and other solid-state systems due to its superior performance and significantly low computational cost. △ Less

Submitted 24 May, 2021; originally announced May 2021.

Comments: 12 pages, 8 figures

Improving the applicability of the Pauli kinetic energy density based semilocal functional for solids

Authors: Subrata Jana, Sushant Kumar Behera, Szymon Smiga, Lucian A. Constantin, Prasanjit Samal

Abstract: The Pauli kinetic energy enhancement factor $α=(τ-τ^W)/τ^{unif}$ is an important density ingredient, used to construct many meta-generalized gradient approximations (meta-GGA) exchange-correlation (XC) energy functionals, including the very successful strongly constrained and appropriately normed (SCAN) semilocal functional. Another meta-GGA functional, known as MGGAC [Phys. Rev. B 100, 155140 (20… ▽ More The Pauli kinetic energy enhancement factor $α=(τ-τ^W)/τ^{unif}$ is an important density ingredient, used to construct many meta-generalized gradient approximations (meta-GGA) exchange-correlation (XC) energy functionals, including the very successful strongly constrained and appropriately normed (SCAN) semilocal functional. Another meta-GGA functional, known as MGGAC [Phys. Rev. B 100, 155140 (2019)], is also proposed in recent time depending only on the $α$ ingredient and based on the generalization of the Becke-Roussel approach with the cuspless hydrogen exchange hole density. The MGGAC functional is proved to be a very useful and competitive meta-GGA semilocal functional for electronic structure properties of solids and molecules. Based on the successful implication of the ingredient $α$, which is also useful to construct the one-electron self-interaction free correlation energy functional, here we propose revised correlation energy for MGGAC exchange functional which is more accurate and robust, especially for the high and low-density limits of the uniform density scaling. The present XC functional, named as revised MGGAC (rMGGAC), shows an impressive improvement for the structural and energetic properties of solids compared to its previous version. Moreover, the assessment of the present constructed functional shows to be quite useful in solid-state physics in terms of addressing several current challenging solid-state problems. △ Less

Submitted 22 April, 2021; originally announced April 2021.

A way of resolving the order-of-limit problem of Tao-Mo semilocal functional

Authors: Abhilash Patra, Subrata Jana, Prasanjit Samal

Abstract: It is highlighted recently that the Tao-Mo (TM) [Phys. Rev. Lett. 117, 073001 (2016)] semilocal exchange-correlation energy functional suffers from the order-of-limit problem, which affects the functional performance for phase transition pressures [J. Chem. Phys. 152, 244112 (2020)]. The root of the order-of-limit problem of the TM functional inherent within the interpolation function, which switc… ▽ More It is highlighted recently that the Tao-Mo (TM) [Phys. Rev. Lett. 117, 073001 (2016)] semilocal exchange-correlation energy functional suffers from the order-of-limit problem, which affects the functional performance for phase transition pressures [J. Chem. Phys. 152, 244112 (2020)]. The root of the order-of-limit problem of the TM functional inherent within the interpolation function, which switches between the compact density and the slowly varying density. In this paper, we propose a different switch function that avoids the order-of-limit problem and interpolates correctly between the compact density and the slowly varying fourth-order density correction. By circumventing the order-of-limit problem, the proposed form enhances the applicability of the original TM functional on the diverse nature of the solid-state properties. Our conclusion is ensured by examining the functional in predicting properties related to the general-purpose solids, quantum chemistry, and phase transition pressure. Besides, we reasonably discuss the connection between the order-of-limit problem, phase transition pressure, and band gap of solids. △ Less

Submitted 13 August, 2020; originally announced August 2020.

Comments: 11 pages, 8 figures

Accurate water properties from an efficient ab-initio method

Authors: Subrata Jana, Lucian A. Constantin, Prasanjit Samal

Abstract: Accurate prediction of the water properties from a low-cost ab-initio method still a foremost problem for chemists and physicist. Though density functional approaches starting from semilocal to hybrid functionals are tested, those are not efficiently performed for all the properties together, especially, considering energies, conformal ranking, structural and dynamics of water. Also, the inclusion… ▽ More Accurate prediction of the water properties from a low-cost ab-initio method still a foremost problem for chemists and physicist. Though density functional approaches starting from semilocal to hybrid functionals are tested, those are not efficiently performed for all the properties together, especially, considering energies, conformal ranking, structural and dynamics of water. Also, the inclusion of the long-range van der Waals (vdW) interaction does not improve the ordering stability of isomer. However, relying on the simple revision of the Tao-Mo (revTM) semilocal meta-generalized gradient approximations, we demonstrate that all properties of the water can be accurately predicted. A consistent improvement over several popular ab-initio methods is achieved, indicating the accuracy of this method for describing hydrogen bonding of water. △ Less

Submitted 29 September, 2019; originally announced September 2019.

Improving the performance of Tao-Mo non-empirical density functional with broader applicability in quantum chemistry and material sciences

Authors: Subrata Jana, Kedar Sharma, Prasanjit Samal

Abstract: A revised version of the semilocal exchange-correlation functional [Phys. Rev. Lett. 117, 073001 (2016)] (TM) is proposed by incorporating the modifications to its correlation content obtained from the full high-density second-order gradient expansion as proposed in the case of revised Tao-Perdew-Staroverov-Scuseria (revTPSS) [Phys. Rev. Lett. 103, 026403 (2009)] functional. The present constructi… ▽ More A revised version of the semilocal exchange-correlation functional [Phys. Rev. Lett. 117, 073001 (2016)] (TM) is proposed by incorporating the modifications to its correlation content obtained from the full high-density second-order gradient expansion as proposed in the case of revised Tao-Perdew-Staroverov-Scuseria (revTPSS) [Phys. Rev. Lett. 103, 026403 (2009)] functional. The present construction improves the performance of TM functional over a wide range of quantum chemical and solid-state properties (thermochemistry and structural). More specifically, the cohesive energies, jellium surface exchange-correlation energies, and real metallic surface energies are improved by preserving the accuracy of the solid-state lattice constants and bulk moduli. The present proposition is not only physically motivated but also enhances the applicability of the TM functional. New physical insights with proper exemplification of the present modification which is presented here can further serve for more realistic non-empirical density functional construction. △ Less

Submitted 2 December, 2018; v1 submitted 29 August, 2018; originally announced August 2018.

Renormalization group analysis of weakly interacting van der Waals Fermi system

Authors: Sushant Kumar Behera, Madhavi Ahalawat, Subrata Jana, Prasanjit Samal, Pritam Deb

Abstract: Weak-coupling phenomena of the two-dimensional Hubbard model is gaining momentum as a new interesting research field due to its extraordinarily rich behavior as a function of the carrier density and model parameters. Salmhofer [{\it Commun. Math. Phys}. \textbf{194}, 249 (1998);{\it Phys. Rev. Lett}. {\bf 87}, 187004 (2001)] developed a new renormalization-group method for interacting Fermi system… ▽ More Weak-coupling phenomena of the two-dimensional Hubbard model is gaining momentum as a new interesting research field due to its extraordinarily rich behavior as a function of the carrier density and model parameters. Salmhofer [{\it Commun. Math. Phys}. \textbf{194}, 249 (1998);{\it Phys. Rev. Lett}. {\bf 87}, 187004 (2001)] developed a new renormalization-group method for interacting Fermi systems and Metzner [{\it Phys. Rev. B} {\bf 61}, 7364 (2000);{\it Phys. Rev. Lett}. {\bf 85}, 5162 (2000)] implemented this renormalization group analysis of the two-dimensional Hubbard model. In this work, we demonstrate the spin-wave dependent susceptibility behavior of model graphene-phosphorene van der Waals heterostructure in the framework of renormalization group approach. We implement signlet vertex response function for the weakly interacting van der Waals Fermi system with nearest-neighbor hopping amplitudes. This analytical approach is further correlated with {\it ab initio} simulation results and extended for spin-wave dependent susceptibility behavior with possible experimental protocols. We present the resulting compressibility and phase diagram in the vicinity of half-filling, and also results for the density dependence of the critical energy scale. △ Less

Submitted 9 June, 2021; v1 submitted 9 August, 2018; originally announced August 2018.

Comments: 11 pages, 8 figures

Journal ref: Journal of Physics: Condensed Matter (2021)

Assessing the performance of the recent non-empirical semilocal density functionals on describing the lattice constants, bulk moduli and cohesive energies of alkali, alkaline-earth, and transition metals

Authors: Subrata Jana, Kedar Sharma, Prasanjit Samal

Abstract: The bulk properties (lattice constants, bulk moduli, and cohesive energies) of alkali, alkaline-earth, and transition metals are studied within the framework of the recently developed meta-GGA (meta-Generalized Gradient Approximation) semilocal exchange-correlation functionals. To establish the applicability, broadness and accuracy of meta-GGA functionals we also put the results of PBE (Perdew-Bur… ▽ More The bulk properties (lattice constants, bulk moduli, and cohesive energies) of alkali, alkaline-earth, and transition metals are studied within the framework of the recently developed meta-GGA (meta-Generalized Gradient Approximation) semilocal exchange-correlation functionals. To establish the applicability, broadness and accuracy of meta-GGA functionals we also put the results of PBE (Perdew-Burke-Ernzerhof) and PBEsol (PBE reparametrized for solids) functionals. The interesting feature of the present paper is that it measures the accuracy of the recently developed TM (Tao-Mo) and TMTPSS (TM exchange with Tao-Perdew-Staroverov-Scuseria (TPSS) correlation) and SCAN (Strongly Constrained and Appropriately Normed) functionals on describing aforementioned properties. The present systematic investigation shows that the TM is accurate in describing the lattice constants while for cohesive energies and bulk moduli the accuracy is biased towards the PBE and TPSS functionals. △ Less

Submitted 8 July, 2018; v1 submitted 1 July, 2018; originally announced July 2018.

Comments: 12 pages, 3 figures

Efficient lattice constants and energy band gaps for condensed systems from a meta-GGA level screened range separated hybrid functional

Authors: Subrata Jana, Abhilash Patra, Prasanjit Samal

Abstract: A meta generalized gradient level screened range-separated hybrid functional is developed for solid-state electronic structure theory. Assessment of the present range-separated hybrid functional for solid-state lattice constants and band gaps indicate that the present functional can be used for describing those properties efficiently in meta-GGA level. Specifically, the performance of the present… ▽ More A meta generalized gradient level screened range-separated hybrid functional is developed for solid-state electronic structure theory. Assessment of the present range-separated hybrid functional for solid-state lattice constants and band gaps indicate that the present functional can be used for describing those properties efficiently in meta-GGA level. Specifically, the performance of the present functional for band gap of solids indicates that the present meta-GGA level screened hybrids functional is quite productive beyond the GGA level. The most appealing feature of the present formalism is that a method has been suggested which is based upon an accurate semilocal functional. △ Less

Submitted 10 March, 2018; originally announced March 2018.

Comments: 9 pages, 2 figures

Performance of Tao-Mo semilocal density functional in projector-augmented-wave method

Authors: Subrata Jana, Abhilash Patra, Prasanjit Samal

Abstract: We assess the performance of Tao-Mo semilocal exchange correlation (TM) functional [J. Tao and Y. Mo, Phys. Rev. Lett. 117, 073001 (2016)] using projector-augmented-wave method with the plane wave basis set in Vienna ab initio simulation package (VASP). The meta-GGA level semilocal functional TM is an all purpose exchange-correlation functional which performs accurately for the wide range of molec… ▽ More We assess the performance of Tao-Mo semilocal exchange correlation (TM) functional [J. Tao and Y. Mo, Phys. Rev. Lett. 117, 073001 (2016)] using projector-augmented-wave method with the plane wave basis set in Vienna ab initio simulation package (VASP). The meta-GGA level semilocal functional TM is an all purpose exchange-correlation functional which performs accurately for the wide range of molecular and solid state properties. The exchange functional part of TM is designed from the density matrix expansion (DME) technique together with the slowly varying fourth order gradient expansion. The correlation functional of the corresponding exchange is based on Tao-Perdew-Staroverov-Scuseria (TPSS) functional. We assess the performance of TM for solid state lattice constants, bulk moduli, band gaps, cohesive energies and magnetic moments of solids. It has been established that in plane wave basis the TM functional performs accurately in predicting all the solid state properties in semilocal level. △ Less

Submitted 14 February, 2018; originally announced February 2018.

Comments: 9 pages

Inhomogeneity Induced and Appropriately Parameterized Semilocal Exchange and Correlation Energy Functionals in Two-Dimensions

Authors: Abhilash Patra, Subrata Jana, Prasanjit Samal

Abstract: The construction of meta generalized gradient approximations based on the density matrix expansion (DME) is considered as one of the most accurate technique to design semilocal exchange energy functionals in two-dimensional density functional formalism. The exchange holes modeled using DME possess unique features that make it a superior entity. Parameterized semilocal exchange energy functionals b… ▽ More The construction of meta generalized gradient approximations based on the density matrix expansion (DME) is considered as one of the most accurate technique to design semilocal exchange energy functionals in two-dimensional density functional formalism. The exchange holes modeled using DME possess unique features that make it a superior entity. Parameterized semilocal exchange energy functionals based on the DME are proposed. The use of different forms of the momentum and flexible parameters is to subsume the non-uniform effects of the density in the newly constructed semilocal functionals. In addition to the exchange functionals, a suitable correlation functional is also constructed by working upon the local correlation functional developed for 2D homogeneous electron gas (2D-HEG). The non-local effects are induced into the correlation functional by a parametric form of one of the newly constructed exchange energy functionals. The proposed functionals are applied to the parabolic quantum dots with a varying number of confined electrons and the confinement strength. The results obtained with the aforementioned functionals are quite satisfactory which indicates why these are suitable for two-dimensional quantum systems. △ Less

Submitted 15 December, 2017; originally announced December 2017.

Comments: 8 pages, 1 figure

Employing semilocal exchange hole with an application to meta-GGA level screened range separated hybrid functional: A conventional wisdom method

Authors: Subrata Jana, Prasanjit Samal

Abstract: Range separated hybrid density functionals are very successful in describing a wide range of molecular and solid state properties accurately. Range separated hybrid functionals are designed from spherically averaged or system averaged reversed engineered exchange hole. In the present attempt, we employ screened range separated hybrid functional scheme to the meta-GGA rung by using Tao-Mo semilocal… ▽ More Range separated hybrid density functionals are very successful in describing a wide range of molecular and solid state properties accurately. Range separated hybrid functionals are designed from spherically averaged or system averaged reversed engineered exchange hole. In the present attempt, we employ screened range separated hybrid functional scheme to the meta-GGA rung by using Tao-Mo semilocal exchange hole (or functional). The hybrid functional proposed here utilizes the spherically averaged density matrix expansion based exchange hole in range separation scheme. For slowly varying density correction, we employ range separation scheme only through the local density approximation (LDA) based exchange hole coupled with the slowly varying Tao-Mo enhancement factor through the conventional wisdom technique. Comprehensive performance and testing of the present functional shows, it accurately describes several molecular properties. The most appealing feature of this present screened hybrid functional is that it will be practically very useful in describing solid state properties in meta-GGA level. △ Less

Submitted 14 December, 2017; originally announced December 2017.

Comments: 6 pages, 2 figures

Density matrix expansion based semi-local exchange hole applied to range separated density functional theory

Authors: Bikash Patra, Subrata Jana, Prasanjit Samal

Abstract: Exchange hole is the principle constituent in density functional theory, which can be used to accurately design exchange energy functional and range separated hybrid functionals coupled with some appropriate correlation. Recently, density matrix expansion (DME) based semi-local exchange hole proposed by Tao-Mo gained attention due to its fulfillment of some exact constraints. We propose a new long… ▽ More Exchange hole is the principle constituent in density functional theory, which can be used to accurately design exchange energy functional and range separated hybrid functionals coupled with some appropriate correlation. Recently, density matrix expansion (DME) based semi-local exchange hole proposed by Tao-Mo gained attention due to its fulfillment of some exact constraints. We propose a new long-range corrected (LC) scheme that combines meta-generalized gradient approximation (meta-GGA) exchange functionals designed from DME exchange hole coupled with the ab-initio Hartree-Fock (HF) exchange integral by separating the Coulomb interaction operator using standard error function. Associate with Lee-Yang-Parr (LYP) correlation functional, assessment and benchmarking of our functional using well-known test set shows that it performs remarkably well for a broad range of molecular properties, such as thermochemistry, noncovalent interaction and barrier height of chemical reactions. △ Less

Submitted 13 September, 2017; originally announced September 2017.

Comments: 9 pages, 3 figures

Performance of Range Separated Hybrids: Study within BECKE88 family and Semilocal Exchange Hole based Range Separated Hybrid

Authors: Subrata Jana, Bikash Patra, Hemanadhan Myneni, Prasanjit Samal

Abstract: A long range corrected range separated hybrid functional is developed based on the density matrix expansion (DME) based semilocal exchange hole with Lee-Yang-Parr (LYP) correlation. An extensive study involving the proposed range separated hybrid for thermodynamic as well as properties related to the fractional occupation number is compared with different BECKE88 family semilocal, hybrid and range… ▽ More A long range corrected range separated hybrid functional is developed based on the density matrix expansion (DME) based semilocal exchange hole with Lee-Yang-Parr (LYP) correlation. An extensive study involving the proposed range separated hybrid for thermodynamic as well as properties related to the fractional occupation number is compared with different BECKE88 family semilocal, hybrid and range separated hybrids. It has been observed that using Kohn-Sham kinetic energy dependent exchange hole several properties related to the fractional occupation number can be improved without hindering the thermochemical accuracy. The newly constructed range separated hybrid accurately describe the hydrogen and non-hydrogen reaction barrier heights. The present range separated functional has been constructed using full semilocal meta-GGA type exchange hole having exact properties related to exchange hole therefore, it has a strong physical basis. △ Less

Submitted 1 September, 2017; originally announced September 2017.

Comments: 12 pages, 16 figures

Assessing The Band Gap Problem By Improving Upon The Semilocal Exchange Hole Potential

Authors: Subrata Jana, Hemanadhan Myneni, Prasanjit Samal

Abstract: An asymptotic corrected exchange hole potential analogous to Becke-Roussel [A. D. Becke and M. R. Roussel, Phys. Rev. A 39, 3761 (1989)] is constructed by modeling the exchange hole using the generalized coordinate transformation based on density matrix expansion. The model potential is Laplacian free and the inhomogeneity present in the system is included in the momentum vector without affecting… ▽ More An asymptotic corrected exchange hole potential analogous to Becke-Roussel [A. D. Becke and M. R. Roussel, Phys. Rev. A 39, 3761 (1989)] is constructed by modeling the exchange hole using the generalized coordinate transformation based on density matrix expansion. The model potential is Laplacian free and the inhomogeneity present in the system is included in the momentum vector without affecting the uniform density limit. The parameters associated with the model exchange hole are fitted with the spherical atoms. The newly constructed potential along with Tran-Blaha modified Becke-Johnson (TBMBJ) [F. Tran and P. Blaha, Phys. Rev. Lett. 102, 226401 (2009)] potential quite accurately produces the band gap of various materials ranging from semiconductor through insulators. The results for band gap are improved compared to the TBMBJ and other standard semilocal exchange functionals. △ Less

Submitted 4 July, 2017; originally announced July 2017.

Comments: 11 pages, 14 figures

Semilocal Exchange Functionals With Improved Performances: The Modified Enhancement Factor For Two Dimensional Quantum Systems

Authors: Subrata Jana, Prasanjit samal

Abstract: Semilocal exchange-correlation functionals are the most accurate, realistic and widely used ones to describe the complex many-electron effects of two-dimensional quantum systems. Beyond local density approximation, the generalized gradient approximations(GGAs) are designed using reduced density gradient as main ingredient. An enhancement factor is constructed using the inhomogeneity parameter of G… ▽ More Semilocal exchange-correlation functionals are the most accurate, realistic and widely used ones to describe the complex many-electron effects of two-dimensional quantum systems. Beyond local density approximation, the generalized gradient approximations(GGAs) are designed using reduced density gradient as main ingredient. An enhancement factor is constructed using the inhomogeneity parameter of GGAs by taking care of the low and high density behaviors of it. Thus, the exchange energy functional proposed by making use of the aforementioned enhancement factor, significantly reduces the error compare to the previously proposed gradient approximations. Another enhancement factor and corresponding energy functional is also constructed using the inhomogeneity parameter originally introduced by Becke [J. Chem. Phys. 109, 2092 (1998)]. Comprehensive testing and performance of both the functionals are demonstrated with respect to the exact exchange formalism by considering two-dimensional parabolically confined quantum dots with varying particle number and confinement strength as a test case. △ Less

Submitted 11 April, 2017; originally announced April 2017.

Role of Kohn-Sham Kinetic Energy Density in Designing Asymptotically Correct Semilocal Exchange-Correlation Functionals in Two Dimensions

Authors: Subrata Jana, Prasanjit Samal

Abstract: The positive definite Kohn-Sham kinetic energy(KS-KE) density plays crucial role in designing semilocal meta generalized gradient approximations(meta-GGAs) for low dimensional quantum systems. It has been rigorously shown that near nucleus and at the asymptotic region, the KE-KS differ from its von Weizsäcker(VW) counterpart as contributions from different orbitals (i.e., s and p orbitals) play im… ▽ More The positive definite Kohn-Sham kinetic energy(KS-KE) density plays crucial role in designing semilocal meta generalized gradient approximations(meta-GGAs) for low dimensional quantum systems. It has been rigorously shown that near nucleus and at the asymptotic region, the KE-KS differ from its von Weizsäcker(VW) counterpart as contributions from different orbitals (i.e., s and p orbitals) play important role. This has been explored using two dimensional isotropic quantum harmonic oscillator as a test case. Several meta-GGA ingredients with different physical behaviors are also constructed and further used to design an accurate semilocal functionals at meta-GGA level. In the asymptotic region, a new exchange energy functional is constructed using the meta-GGA ingredients with formally exact properties of the enhancement factor. Also, it has been shown that exact asymptotic behavior of the exchange energy density and potential can be attained by choosing accurately the enhancement factor as a functional of meta-GGA ingredients. △ Less

Submitted 15 March, 2017; originally announced March 2017.

Comments: 9 pages, 5 figures

Semi-local Exchange Energy Functional For Two-Dimensional Quantum Systems: A Step Beyond Generalized Gradient Approximations

Authors: Subrata Jana, Prasanjit Samal

Abstract: Semi-local density functionals for the exchange-correlation energy of electrons are extensively used as it produce realistic and accurate results for finite and extended systems. The choice of techniques play crucial role in constructing such functionals of improved accuracy and efficiency. An accurate and efficient semi-local exchange energy functional in two dimensions is constructed by making u… ▽ More Semi-local density functionals for the exchange-correlation energy of electrons are extensively used as it produce realistic and accurate results for finite and extended systems. The choice of techniques play crucial role in constructing such functionals of improved accuracy and efficiency. An accurate and efficient semi-local exchange energy functional in two dimensions is constructed by making use of the corresponding hole based on the density matrix expansion. The exchange hole involved is localized under the generalized coordinate transformation and satisfies all the relevant constraints. Comprehensive testing and excellent performance of the functional is demonstrated versus exact exchange results. The functional also achieves remarkable accuracy by substantially reducing the errors present in the local and non-empirical density functionals proposed so far for two dimensional systems. The underlying principles involved in the functional construction are physically appealing and practically useful for developing range separated and non-local functionals in two dimensions. △ Less

Submitted 6 March, 2017; originally announced March 2017.

Comments: 6 pages, 3 figures

Excited-State Density-Functional Theory Revisited: on the Uniqueness, Existence, and Construction of the Density-to-Potential Mapping

Authors: Prasanjit Samal, Subrata Jana, Sourabh S. Chauhan

Abstract: The generalized constrained search formalism is used to address the issues concerning density-to-potential mapping for excited states in time-independent density-functional theory. The multiplicity of potentials for any given density and the uniqueness in density-to-potential mapping are explained within the framework of unified constrained search formalism for excited-states due to Görling, Levy-… ▽ More The generalized constrained search formalism is used to address the issues concerning density-to-potential mapping for excited states in time-independent density-functional theory. The multiplicity of potentials for any given density and the uniqueness in density-to-potential mapping are explained within the framework of unified constrained search formalism for excited-states due to Görling, Levy-Nagy, Samal-Harbola and Ayers-Levy. The extensions of Samal-Harbola criteria and it's link to the generalized constrained search formalism are revealed in the context of existence and unique construction of the density-to-potential mapping. The close connections between the proposed criteria and the generalized adiabatic connection are further elaborated so as to keep the desired mapping intact at the strictly correlated regime. Exemplification of the unified constrained search formalism is done through model systems in order to demonstrate that the seemingly contradictory results reported so far are neither the true confirmation of lack of Hohenberg-Kohn theorem nor valid representation of violation of Gunnarsson-Lundqvist theorem for excited states. Hence the misleading interpretation of subtle differences between the ground and excited state density functional formalism are exemplified. △ Less

Submitted 7 June, 2015; v1 submitted 8 July, 2014; originally announced July 2014.

Comments: 19 pages, 22 figures

A local-density approximation for the exchange energy functional for excited states : the band gap problem

Authors: Moshiour Rahaman, Shreemoyee Ganguly, Prasanjit Samal, Manoj Kumar Harbola, Tanusri Saha-Dasgupta, Abhijit Mookerjee

Abstract: We present excited states density functional theory (DFT) to calculate band gap for semiconductors and insulators. For the excited states exchange-correlation functional, we use a simple local density approximation (LDA) like functional and it gives the result which is very closed to experimental results. The linear muffin-tin potential is used to solve the self consistent Kohn-Sham equation We present excited states density functional theory (DFT) to calculate band gap for semiconductors and insulators. For the excited states exchange-correlation functional, we use a simple local density approximation (LDA) like functional and it gives the result which is very closed to experimental results. The linear muffin-tin potential is used to solve the self consistent Kohn-Sham equation △ Less

Submitted 29 October, 2008; originally announced October 2008.

Comments: 15 pages, 3 figures

Analysis of Floquet formulation of time-dependent density-functional theory

Authors: Prasanjit Samal, Manoj K. Harbola

Abstract: Floquet formulation of time-dependent density-functional theory is revisited in light of its recent criticism [Maitra and Burke, Chem. Phys. Lett. 359 (2002), 237]. It is shown that Floquet theory is well founded and its criticism has overlooked important points of both the Runge-Gross formalism and Floquet formulation itself. We substantiate our analysis by examples similar to that considered b… ▽ More Floquet formulation of time-dependent density-functional theory is revisited in light of its recent criticism [Maitra and Burke, Chem. Phys. Lett. 359 (2002), 237]. It is shown that Floquet theory is well founded and its criticism has overlooked important points of both the Runge-Gross formalism and Floquet formulation itself. We substantiate our analysis by examples similar to that considered by Maitra and Burke. △ Less

Submitted 16 November, 2006; originally announced November 2006.

Comments: 17 pages, 2 figures. accepted for publication in "Chemical Physics Letters"

Exploring Foundations of Time-Independent Density Functional Theory for Excited-States

Authors: Prasanjit Samal, Manoj K. Harbola

Abstract: Based on the work of Gorling and that of Levy and Nagy, density-functional formalism for many Fermionic excited-states is explored through a careful and rigorous analysis of the excited-state density to external potential mapping. It is shown that the knowledge of the ground-state density is a must to fix the mapping from an excited-state density to the external potential. This is the excited-st… ▽ More Based on the work of Gorling and that of Levy and Nagy, density-functional formalism for many Fermionic excited-states is explored through a careful and rigorous analysis of the excited-state density to external potential mapping. It is shown that the knowledge of the ground-state density is a must to fix the mapping from an excited-state density to the external potential. This is the excited-state counterpart of the Hohenberg-Kohn theorem, where instead of the ground-state density the density of the excited-state gives the true many-body wavefunctions of the system. Further, the excited-state Kohn-Sham system is defined by comparing it's non-interacting kinetic energy with the true kinetic energy. The theory is demonstrated by studying a large number of atomic systems. △ Less

Submitted 2 February, 2006; originally announced February 2006.

Comments: submitted to J. Chem. Phys

Density-to-potential map in time-independent excited-state density-functional theory

Authors: Prasanjit Samal, Manoj K. Harbola, A. Holas

Abstract: In light of the recent work by Sahni et al., Harbola, and Gaudoin and Burke, the question of mapping from an excited-state density of a many-electron interacting system to the potential of the related non-interacting system is analyzed. To do so, we investigate the Levy-Nagy criterion quantitatively for several excited-states. Our work indicates that Levy-Nagy criterion may fix the density to po… ▽ More In light of the recent work by Sahni et al., Harbola, and Gaudoin and Burke, the question of mapping from an excited-state density of a many-electron interacting system to the potential of the related non-interacting system is analyzed. To do so, we investigate the Levy-Nagy criterion quantitatively for several excited-states. Our work indicates that Levy-Nagy criterion may fix the density to potential map uniquely. △ Less

Submitted 2 February, 2006; originally announced February 2006.

Journal ref: Chem. Phys. Lett. 419 (2006) 217 - 222

Local-density approximation for exchange energy functional in excited-state density functional theory

Authors: Prasanjit Samal, Manoj K. Harbola

Abstract: An exchange energy functional is proposed and tested for obtaining a class of excited-state energies using density functional formalism. The functional is the excited-state counterpart of the local-density approximation functional for the ground state. It takes care of the state dependence of the energy functional and leads to highly accurate excitation energies. An exchange energy functional is proposed and tested for obtaining a class of excited-state energies using density functional formalism. The functional is the excited-state counterpart of the local-density approximation functional for the ground state. It takes care of the state dependence of the energy functional and leads to highly accurate excitation energies. △ Less

Submitted 2 February, 2006; originally announced February 2006.

Journal ref: J. Phys. B: At. Mol. Opt. Phys. 38 (2005) 3765 - 3777

An accurate exchange energy functional in excited-state density functional theory

Authors: Prasanjit Samal, Manoj K. Harbola

Abstract: An exchange energy functional is proposed and tested for obtaining a class of excited-state energies using density-functional formalism. The functional is the excited-state counterpart of the local-density approximation functional for the ground-state. It takes care of the state-dependence of the energy functional and leads to highly accurate excitation energies. An exchange energy functional is proposed and tested for obtaining a class of excited-state energies using density-functional formalism. The functional is the excited-state counterpart of the local-density approximation functional for the ground-state. It takes care of the state-dependence of the energy functional and leads to highly accurate excitation energies. △ Less

Submitted 14 October, 2004; originally announced October 2004.

Comments: 19 pages. 2 figures. Submitted to PRA

Local density approximation for exchange in excited-state density functional theory

Authors: Manoj K. Harbola, Prasanjit Samal

Abstract: Local density approximation for the exchange energy is made for treatment of excited-states in density-functional theory. It is shown that taking care of the state-dependence of the LDA exchange energy functional leads to accurate excitation energies. Local density approximation for the exchange energy is made for treatment of excited-states in density-functional theory. It is shown that taking care of the state-dependence of the LDA exchange energy functional leads to accurate excitation energies. △ Less

Submitted 5 July, 2004; originally announced July 2004.