Showing 1–15 of 15 results for author: Nepal, N

A Precision Emulation Approach to the GPU Acceleration of Ab Initio Electronic Structure Calculations

Authors: Hang Liu, Junjie Li, Yinzhi Wang, Niraj K. Nepal, Yang Wang

Abstract: This study explores the use of INT8-based emulation for accelerating traditional FP64-based HPC workloads on modern GPU architectures. Through SCILIB-Accel automatic BLAS offload tool for cache-coherent Unified Memory Architecture, we emulate FP64 matrix multiplications in the LSMS CPU application in the MuST suite without code changes. We find that accuracy depends on both arithmetic precision an… ▽ More This study explores the use of INT8-based emulation for accelerating traditional FP64-based HPC workloads on modern GPU architectures. Through SCILIB-Accel automatic BLAS offload tool for cache-coherent Unified Memory Architecture, we emulate FP64 matrix multiplications in the LSMS CPU application in the MuST suite without code changes. We find that accuracy depends on both arithmetic precision and the properties of the operator, which can be dealt with through tunable precision emulation. Unlike traditional mixed-precision approaches, this method preserves original algorithms while optimizing hardware utilization. We showcase the potential of improving accuracy and performance at the same time. This work highlights the potential of AI-driven hardware to transform HPC, advocating for adaptive precision strategies in future scientific computing. △ Less

Submitted 31 March, 2026; originally announced March 2026.

HTESP (High-throughput electronic structure package): a Package for the high-throughput $ab$ $initio$ calculations

Authors: Niraj K. Nepal, Paul C. Canfield, Lin-Lin Wang

Abstract: High-throughput $ab$ $initio$ calculations are the indispensable parts of data-driven discovery of new materials with desirable properties, as reflected in the establishment of several online material databases. The accumulation of extensive theoretical data through computations enables data-driven discovery by constructing machine learning and artificial intelligence models to predict novel compo… ▽ More High-throughput $ab$ $initio$ calculations are the indispensable parts of data-driven discovery of new materials with desirable properties, as reflected in the establishment of several online material databases. The accumulation of extensive theoretical data through computations enables data-driven discovery by constructing machine learning and artificial intelligence models to predict novel compounds and forecast their properties. Efficient usage and extraction of data from these existing online material databases can accelerate the next stage materials discovery that targets different and more advanced properties, such as electron-phonon coupling for phonon-mediated superconductivity. However, extracting data from these databases, generating tailored input files for different $ab$ $initio$ calculations, performing such calculations, and analyzing new results can be demanding tasks. Here, we introduce a software package named "HTESP" (High-Throughput Electronic Structure Package) written in Python and Bash languages, which automates the entire workflow including data extraction, input file generation, calculation submission, result collection and plotting. Our HTESP will help speed up future computational materials discovery processes. △ Less

Submitted 18 July, 2024; v1 submitted 6 June, 2024; originally announced June 2024.

Journal ref: Computational Materials Science, 244, 113247 (2024)

Measurements and Numerical Calculations of Thermal Conductivity to Evaluate the Quality of β-Gallium Oxide Thin Films Grown on Sapphire and Silicon Carbide by Molecular Beam Epitaxy

Authors: Diego Vaca, Matthew Barry, Luke Yates, Neeraj Nepal, D. Scott Katzer, Brian P. Downey, Virginia Wheeler, Luke Nyakiti, David J. Meyer, Samuel Graham, Satish Kumar

Abstract: We report a method to obtain insights into lower thermal conductivity of β-Ga2O3 thin films grown by molecular beam epitaxy (MBE) on c-plane sapphire and 4H-SiC substrates. We compare experimental values against the numerical predictions to decipher the effect of boundary scattering and defects in thin-films. We used time domain thermoreflectance (TDTR) to perform the experiments, density function… ▽ More We report a method to obtain insights into lower thermal conductivity of β-Ga2O3 thin films grown by molecular beam epitaxy (MBE) on c-plane sapphire and 4H-SiC substrates. We compare experimental values against the numerical predictions to decipher the effect of boundary scattering and defects in thin-films. We used time domain thermoreflectance (TDTR) to perform the experiments, density functional theory and the Boltzmann transport equation for thermal conductivity calculations, and the diffuse mismatch model for TBC predictions. The experimental thermal conductivities were approximately 3 times smaller than those calculated for perfect Ga2O3 crystals of similar size. When considering the presence of grain boundaries, gallium and oxygen vacancies, and stacking faults in the calculations, the crystals that present around 1% of gallium vacancies and a density of stacking faults of 106 faults/cm were the ones whose thermal conductivities were closer to the experimental results. Our analysis suggests the level of different types of defects present in the Ga2O3 crystal that could be used to improve the quality of MBE-grown samples by reducing these defects and thereby produce materials with higher thermal conductivities. △ Less

Submitted 4 May, 2022; originally announced May 2022.

Comments: 11 pages. Includes supplementary Information. The following article has been submitted to Applied Physics Letters. After it is published, it will be found at https://publishing.aip.org/resources/librarians/products/journals/

Tunable band gaps and optical absorption properties of bent MoS$_2$ nanoribbons

Authors: Hong Tang, Bimal Neupane, Santosh Neupane, Shiqi Ruan, Niraj K. Nepal, Adrienn Ruzsinszky

Abstract: The large tunability of band gaps and optical absorptions of armchair MoS$_2$ nanoribbons of different widths under bending is studied using density functional theory and many-body perturbation GW and Bethe-Salpeter equation approaches. We find that there are two critical bending curvatures, and the non-edge and edge band gaps generally show a non-monotonic trend with bending. The non-degenerate e… ▽ More The large tunability of band gaps and optical absorptions of armchair MoS$_2$ nanoribbons of different widths under bending is studied using density functional theory and many-body perturbation GW and Bethe-Salpeter equation approaches. We find that there are two critical bending curvatures, and the non-edge and edge band gaps generally show a non-monotonic trend with bending. The non-degenerate edge gap splits show an oscillating feature with ribbon width n, with a period delta_n=3, due to quantum confinement effects. The complex strain patterns on the bent nanoribbons control the varying features of band structures and band gaps that result in varying exciton formations and optical properties. The binding energy and the spin singlet-triplet split of the exciton forming the lowest absorption peak generally decrease with bending curvatures. The large tunability of optical properties of bent MoS$_2$ nanoribbons is promising and will find applications in tunable optoelectronic nanodevices. △ Less

Submitted 31 October, 2022; v1 submitted 9 September, 2021; originally announced September 2021.

First-principles wavevector- and frequency-dependent exchange-correlation kernel for jellium at all densities

Authors: Aaron D. Kaplan, Niraj K. Nepal, Adrienn Ruzsinszky, Pietro Ballone, John P. Perdew

Abstract: We propose a spatially and temporally nonlocal exchange-correlation (xc) kernel for the spin-unpolarized fluid phase of ground-state jellium, for use in time-dependent density functional and linear response calculations. The kernel is constructed to satisfy known properties of the exact xc kernel, to accurately describe the correlation energies of bulk jellium, and to satisfy frequency-moment sum… ▽ More We propose a spatially and temporally nonlocal exchange-correlation (xc) kernel for the spin-unpolarized fluid phase of ground-state jellium, for use in time-dependent density functional and linear response calculations. The kernel is constructed to satisfy known properties of the exact xc kernel, to accurately describe the correlation energies of bulk jellium, and to satisfy frequency-moment sum rules at a wide range of bulk jellium densities, including those low densities that display strong correlation and symmetry breaking. These effects are easier to understand in the simple jellium model than in real systems. All exact constraints satisfied by the recent MCP07 kernel [A. Ruzsinszky, et al., Phys. Rev. B 101, 245135 (2020)] are maintained in the new revised MCP07 (rMCP07) kernel, while others are added. The revision $f_\mathrm{xc}^\mathrm{rMCP07}(q,ω)$ differs from MCP07 only for non-zero frequencies $ω$. Only at densities much lower than those of real bulk metals is the frequency dependence of the kernel important for the correlation energy of jellium. As the wavevector $q$ tends to zero, the kernel has a $-4πα(ω)/q^2$ divergence whose frequency-dependent ultranonlocality coefficient $α(ω)$ vanishes in jellium, and is predicted by rMCP07 to be extremely small for the real metals Al and Na.} △ Less

Submitted 22 November, 2021; v1 submitted 5 July, 2021; originally announced July 2021.

Comments: (1st revision) Changes to the TC21 model, new App. F discussing numerical methods. (2nd revision) Revisions in response to peer comments. Refocused discussion around building a kernel for jellium, rather than for metals/materials. (3rd revision) Name change of kernel, TC21 --> rMCP07; added details of QMC calculations; added CP07 and Richardson-Ashcroft correlation energies

Progress towards understanding ultranonlocality through the wavevector and frequency dependence of approximate exchange-correlation kernels

Authors: Niraj K. Nepal, Aaron D. Kaplan, J. M. Pitarke, Adrienn Ruzsinszky

Abstract: In the framework of time-dependent density functional theory (TDDFT), the exact exchange-correlation (xc) kernel $f_{xc}(n,q,ω)$ determines the ground-state energy, excited-state energies, lifetimes, and the time-dependent linear density response of any many-electron system. The recently developed MCP07 xc kernel $f_{xc}(n,q,ω)$ of A. Ruzsinszky et al. [Phys. Rev. B 101, 245135 (2020)] yields exce… ▽ More In the framework of time-dependent density functional theory (TDDFT), the exact exchange-correlation (xc) kernel $f_{xc}(n,q,ω)$ determines the ground-state energy, excited-state energies, lifetimes, and the time-dependent linear density response of any many-electron system. The recently developed MCP07 xc kernel $f_{xc}(n,q,ω)$ of A. Ruzsinszky et al. [Phys. Rev. B 101, 245135 (2020)] yields excellent uniform electron gas (UEG) ground-state energies and plausible plasmon lifetimes. As MCP07 is constructed to describe $f_{xc}$ of the UEG, it cannot capture optical properties of real materials. To verify this claim, we follow Nazarov et al. [Phys. Rev. Lett. 102, 113001 (2009)] to construct the long-range, dynamic xc kernel, $\lim_{q\to 0}f_{xc}(n,q,ω) = -α(ω)e^2/q^2$, of a weakly inhomogeneous electron gas, using MCP07 and other common xc kernels. The strong wavevector and frequency dependence of the "ultranonlocality" coefficient $α(ω)$ is demonstrated for a variety of simple metals and semiconductors. We examine how imposing exact constraints on an approximate kernel shapes $α(ω)$. Comparisons to kernels derived from correlated-wavefunction calculations are drawn. △ Less

Submitted 30 July, 2021; v1 submitted 24 May, 2021; originally announced May 2021.

Comments: Includes new kernels: a novel QV-MCP07 hybrid kernel that better estimates ultranonlocality, and the LRC and 2p2h kernels as better references for ultranonlocality. Miscellaneous typographical/syntactic changes

Journal ref: Phys. Rev. B 104, 125112 (2021)

Nickel Foam as a Substrate for III-nitride Nanowire Growth

Authors: Michael A. Mastro, Neeraj Nepal, Fritz Kub, Jennifer K. Hite, J. Kim, Charles R. Eddy Jr

Abstract: This article presents the use of flexible metal foam substrates for the growth of III-nitride nanowire light emitters to tackle the inherent limitations of thin-film light emitting diodes as well as fabrication and application issues of traditional substrates. A dense packing of gallium nitride nanowires were grown on a nickel foam substrate. The nanowires grew predominantly along the a-plane dire… ▽ More This article presents the use of flexible metal foam substrates for the growth of III-nitride nanowire light emitters to tackle the inherent limitations of thin-film light emitting diodes as well as fabrication and application issues of traditional substrates. A dense packing of gallium nitride nanowires were grown on a nickel foam substrate. The nanowires grew predominantly along the a-plane direction, normal to the local surface of the nickel foam. Strong luminescence was observed from undoped GaN and InGaN quantum well light emitting diode nanowires. △ Less

Submitted 2 September, 2020; originally announced September 2020.

Journal ref: MRS Online Proceeding Library Archive 1538:311-316, 2012

The Fermi-Löwdin self-interaction correction for ionization energies of organic molecules

Authors: Santosh Adhikari, Biswajit Santra, Shiqi Ruan, Puskar Bhattarai, Niraj K. Nepal, Koblar A. Jackson, Adrienn Ruzsinszky

Abstract: (Semi)-local density functional approximations (DFAs) suffer from self-interaction error (SIE). When the first ionization energy (IE) is computed as the negative of the highest-occupied orbital (HO) eigenvalue, DFAs notoriously underestimate them compared to quasi-particle calculations. The inaccuracy for the HO is attributed to SIE inherent in DFAs. We assessed the IE based on Perdew-Zunger self-… ▽ More (Semi)-local density functional approximations (DFAs) suffer from self-interaction error (SIE). When the first ionization energy (IE) is computed as the negative of the highest-occupied orbital (HO) eigenvalue, DFAs notoriously underestimate them compared to quasi-particle calculations. The inaccuracy for the HO is attributed to SIE inherent in DFAs. We assessed the IE based on Perdew-Zunger self-interaction corrections on 14 small to moderate-sized organic molecules relevant in organic electronics and polymer donor materials. Though self-interaction corrected DFAs were found to significantly improve the IE relative to the uncorrected DFAs, they overestimate. However, when the self-interaction correction is interiorly scaled using a function of the iso-orbital indicator zσ, only the regions where SIE is significant get a correction. We discuss these approaches and show how these methods significantly improve the description of the HO eigenvalue for the organic molecules. △ Less

Submitted 11 August, 2020; originally announced August 2020.

Interpretations of ground-state symmetry breaking and strong correlation in wavefunction and density functional theories

Authors: John P. Perdew, Adrienn Ruzsinszky, Jianwei Sun, Niraj K. Nepal, Aaron D. Kaplan

Abstract: Strong correlations within a symmetry-unbroken ground-state wavefunction can show up in approximate density functional theory as symmetry-broken spin-densities or total densities, which are sometimes observable. They can arise from soft modes of fluctuations (sometimes collective excitations) such as spin-density or charge-density waves at non-zero wavevector. In this sense, an approximate density… ▽ More Strong correlations within a symmetry-unbroken ground-state wavefunction can show up in approximate density functional theory as symmetry-broken spin-densities or total densities, which are sometimes observable. They can arise from soft modes of fluctuations (sometimes collective excitations) such as spin-density or charge-density waves at non-zero wavevector. In this sense, an approximate density functional for exchange and correlation that breaks symmetry can be more revealing (albeit less accurate) than an exact functional that does not. The examples discussed here include the stretched H$_2$ molecule, antiferromagnetic solids, and the static charge-density wave/Wigner crystal phase of a low-density jellium. It is shown that (and in what sense) the static charge density wave is a soft plasmon. △ Less

Submitted 23 July, 2020; originally announced July 2020.

Plastic Scintillation Detectors for Time-of-Flight Mass Measurements

Authors: Kailong Wang, Alfredo Estrade, Shree Neupane, Miles Barber, Michael Famiano, Tom Ginter, David McClain, Neerajan Nepal, Jorge Pereira, Hendrik Schatz, George Zimba

Abstract: Fast timing detectors are an essential element in the experimental setup for time-of-flight (ToF) mass measurements of unstable nuclei. We have upgraded the scintillator detectors used in experiments at the National Superconducting Cyclotron Laboratory (NSCL) by increasing the number of photomultiplier tubes that read out their light signals to four per detector, and characterized them in a test e… ▽ More Fast timing detectors are an essential element in the experimental setup for time-of-flight (ToF) mass measurements of unstable nuclei. We have upgraded the scintillator detectors used in experiments at the National Superconducting Cyclotron Laboratory (NSCL) by increasing the number of photomultiplier tubes that read out their light signals to four per detector, and characterized them in a test experiment with $^{48}$Ca beam at the NSCL. The new detectors achieved a time resolution ($σ$) of 7.5 ps. We systematically investigated different factors that affect their timing performance. In addition, we evaluated the ability of positioning the hitting points on the scintillator using the timing information and obtained a resolution ($σ$) below 1 mm for well-defined beam spots. △ Less

Submitted 3 May, 2020; originally announced May 2020.

Comments: 11 pages, 10 figures, submitted to NIMA

Constraint-based Wavevector- and Frequency-dependent Exchange-Correlation Kernel of the Uniform Electron Gas

Authors: Adrienn Ruzsinszky, Niraj K. Nepal, J. M. Pitarke, John P. Perdew

Abstract: According to time-dependent density functional theory, the exact exchange-correlation kernel f$_{xc}$(n, q, $ω$) determines not only the ground-state energy but also the excited-state energies/lifetimes and time-dependent linear density response of an electron gas of uniform density n $=$ 3/(4$π$r$^3_s$). Here we propose a parametrization of this function based upon the satisfaction of exact const… ▽ More According to time-dependent density functional theory, the exact exchange-correlation kernel f$_{xc}$(n, q, $ω$) determines not only the ground-state energy but also the excited-state energies/lifetimes and time-dependent linear density response of an electron gas of uniform density n $=$ 3/(4$π$r$^3_s$). Here we propose a parametrization of this function based upon the satisfaction of exact constraints. For the static ($ω$ = 0) limit, we modify the model of Constantin and Pitarke at small wavevector q to recover the known second-order gradient expansion, plus other changes. For all frequencies $ω$ at q $=$ 0, we use the model of Gross, Kohn, and Iwamoto. A Cauchy integral extends this model to complex $ω$ and implies the standard Kramers-Kronig relations. A scaling relation permits closed forms for not only the imaginary but also the real part of f$_{xc}$ for real $ω$. We then combine these ingredients by damping out the $ω$ dependence at large q in the same way that the q dependence is damped. Away from q $=$ 0 and $ω$ $=$ 0, the correlation contribution to the kernel becomes dominant over exchange, even at r$_s$ $=$ 4, the valence electron density of metallic sodium. The resulting correlation energy from integration over imaginary $ω$ is essentially exact. The plasmon pole of the density response function is found by analytic continuation of f$_{xc}$ to $ω$ just below the real axis, and the resulting plasmon lifetime first decreases from infinity and then increases as q grows from 0 toward the electron-hole continuum. A static charge-density wave is found for r$_s$ $>$ 69, and shown to be associated with softening of the plasmon mode. The exchange-only version of our static kernel confirms Overhauser's 1968 prediction that correlation enhances the charge-density wave. △ Less

Submitted 20 April, 2020; originally announced April 2020.

Comments: 20 pages including 11 figures

Journal ref: Phys. Rev. B 101, 245135 (2020)

Epitaxial bulk acoustic wave resonators as highly coherent multi-phonon sources for quantum acoustodynamics

Authors: Vikrant J. Gokhale, Brian P. Downey, D. Scott Katzer, Neeraj Nepal, Andrew C. Lang, Rhonda M. Stroud, David J. Meyer

Abstract: Solid-state quantum acoustodynamic (QAD) systems provide a compact platform for quantum information storage and processing by coupling acoustic phonon sources with superconducting or spin qubits. The multi-mode composite high-overtone bulk acoustic wave resonator (HBAR) is a popular phonon source well suited for QAD. However, scattering from defects, grain boundaries, and interfacial/surface rough… ▽ More Solid-state quantum acoustodynamic (QAD) systems provide a compact platform for quantum information storage and processing by coupling acoustic phonon sources with superconducting or spin qubits. The multi-mode composite high-overtone bulk acoustic wave resonator (HBAR) is a popular phonon source well suited for QAD. However, scattering from defects, grain boundaries, and interfacial/surface roughness in the composite transducer severely limits the phonon relaxation time in sputter-deposited devices. Here, we grow an epitaxial-HBAR, consisting of a metallic NbN bottom electrode and a piezoelectric GaN film on a SiC substrate. The acoustic impedance-matched epi-HBAR has a power injection efficiency > 99% from transducer to phonon cavity. The smooth interfaces and low defect density reduce phonon losses, yielding fxQ products and phonon lifetimes up to 1.36 x 10^17 Hz and 500 microseconds respectively. The GaN/NbN/SiC epi-HBAR is an electrically actuated, multi-mode phonon source that can be directly interfaced with NbN-based superconducting qubits or SiC-based spin qubits. △ Less

Submitted 24 March, 2020; originally announced March 2020.

Journal ref: Nat Commun 11, 2314 (2020)

Stretched or noded orbital densities and self-interaction correction in density functional theory

Authors: Chandra Shahi, Puskar Bhattarai, Kamal Wagle, Biswajit Santra, Sebastian Schwalbe, Torsten Hahn, Jens Kortus, Koblar A. Jackson, Juan E. Peralta, Kai Trepte, Susi Lehtola, Niraj K. Nepal, Hemanadhan Myneni, Bimal Neupane, Santosh Adhikari, Adrienn Ruzsinszky, Yoh Yamamoto, Tunna Baruah, Rajendra R. Zope, John P. Perdew

Abstract: Semi-local approximations to the density functional for the exchange-correlation energy of a many-electron system necessarily fail for lobed one-electron densities, including not only the familiar stretched densities but also the less familiar but closely-related noded ones. The Perdew-Zunger (PZ) self-interaction correction (SIC) to a semi-local approximation makes that approximation exact for al… ▽ More Semi-local approximations to the density functional for the exchange-correlation energy of a many-electron system necessarily fail for lobed one-electron densities, including not only the familiar stretched densities but also the less familiar but closely-related noded ones. The Perdew-Zunger (PZ) self-interaction correction (SIC) to a semi-local approximation makes that approximation exact for all one-electron ground- or excited-state densities and accurate for stretched bonds. When the minimization of the PZ total energy is made over real localized orbitals, the orbital densities can be noded, leading to energy errors in many-electron systems. Minimization over complex localized orbitals yields nodeless orbital densities, which reduce but typically do not eliminate the SIC errors of atomization energies. Other errors of PZ SIC remain, attributable to the loss of the exact constraints and appropriate norms that the semi-local approximations satisfy, and suggesting the need for a generalized SIC. These conclusions are supported by calculations for one-electron densities, and for many-electron molecules. While PZ SIC raises and improves the energy barriers of standard generalized gradient approximations (GGA's) and meta-GGA's, it reduces and often worsens the atomization energies of molecules. Thus PZ SIC raises the energy more as the nodality of the valence localized orbitals increases from atoms to molecules to transition states. PZ SIC is applied here in particular to the SCAN meta-GGA, for which the correlation part is already self-interaction-free. That property makes SCAN a natural first candidate for a generalized SIC. △ Less

Submitted 2 April, 2019; v1 submitted 1 March, 2019; originally announced March 2019.

Journal ref: J. Chem. Phys. 150, 174102 (2019)

Commissioning of the BRIKEN detector for the measurement of very exotic beta-delayed neutron emitters

Authors: A. Tolosa-Delgado, J. Agramunt, J. L. Tain, A. Algora, C. Domingo-Pardo, A. I. Morales, B. Rubio, A. Tarifeno-Saldivia, F. Calvino, G. Cortes, N. T. Brewer, B. C. Rasco, K. P. Rykaczewski, D. W. Stracener, J. M. Allmond, R. Grzywacz, R. Yokoyama, M. Singh, T. King, M. Madurga, S. Nishimura, V. H. Phong, S. Go, J. Liu, K. Matsui , et al. (41 additional authors not shown)

Abstract: A new detection system has been installed at the RIKEN Nishina Center (Japan) to investigate decay properties of very neutron-rich nuclei. The setup consists of three main parts: a moderated neutron counter, a detection system sensitive to the implantation and decay of radioactive ions, and gamma-ray detectors. We describe here the setup, the commissioning experiment and some selected results demo… ▽ More A new detection system has been installed at the RIKEN Nishina Center (Japan) to investigate decay properties of very neutron-rich nuclei. The setup consists of three main parts: a moderated neutron counter, a detection system sensitive to the implantation and decay of radioactive ions, and gamma-ray detectors. We describe here the setup, the commissioning experiment and some selected results demonstrating its performance for the measurement of half-lives and beta-delayed neutron emission probabilities. The methodology followed in the analysis of the data is described in detail. Particular emphasis is placed on the correction of the accidental neutron background. △ Less

Submitted 2 August, 2018; originally announced August 2018.

The ORNL Analysis Technique for Extracting $β$-Delayed Multi-Neutron Branching Ratios with BRIKEN

Authors: B. C. Rasco, N. T. Brewer, R. Yokoyama, R. Grzywacz, K. P. Rykaczewski, A. Tolosa-Delgado, J. Agramunt, J. L. Tain, A. Algora, O. Hall, C. Griffin, T. Davinson, V. H. Phong, J. Liu, S. Nishimura, G. G. Kiss, N. Nepal, A. Estrade

Abstract: Many choices are available in order to evaluate large radioactive decay networks. %multi-particle decay data. There are many parameters that influence the calculated $β$-decay delayed single and multi-neutron emission branching fractions. We describe assumptions about the decay model, background, and other parameters and their influence on $β$-decay delayed multi-neutron emission analysis. An anal… ▽ More Many choices are available in order to evaluate large radioactive decay networks. %multi-particle decay data. There are many parameters that influence the calculated $β$-decay delayed single and multi-neutron emission branching fractions. We describe assumptions about the decay model, background, and other parameters and their influence on $β$-decay delayed multi-neutron emission analysis. An analysis technique, the ORNL BRIKEN analysis procedure, for determining $β$-delayed multi-neutron branching ratios in $β$-neutron precursors produced by means of heavy-ion fragmentation is presented. The technique is based on estimating the initial activities of zero, one, and two neutrons occurring in coincidence with an ion-implant and $β$ trigger. The technique allows one to extract $β$-delayed multi-neutron decay branching ratios measured with the hybrid \textsuperscript{3}He BRIKEN neutron counter. As an example, two analyses of the $β$-neutron emitter \textsuperscript{77}Cu based on different {\it a priori} assumptions are presented along with comparisons to literature values. △ Less

Submitted 13 June, 2018; originally announced June 2018.

Comments: 21 pages, 10 figures