-
High-pressure phase stability and superconductivity in La-Zr-H hydrides
Authors:
Ijaz shahid,
Maxim A. Grebeniuk,
Jinbin Zhao,
Ergen Bao,
Tianye Yu,
Xiangyang Liu,
Yi-Chi Zhang,
Artem R. Oganov,
Yan Sun,
Peitao Liu,
Xing-Qiu Chen
Abstract:
Hydrogen-rich ternary hydrides are promising candidates for high-Tc superconductivity at megabar pressures, yet their chemical space is vast and largely unexplored. Combining evolutionary structure searches with first-principles calculations, we comprehensively investigate the La-Zr-H ternary system in the 150-300 GPa pressure range. Zero-point energy-corrected convex hull analysis identifies mult…
▽ More
Hydrogen-rich ternary hydrides are promising candidates for high-Tc superconductivity at megabar pressures, yet their chemical space is vast and largely unexplored. Combining evolutionary structure searches with first-principles calculations, we comprehensively investigate the La-Zr-H ternary system in the 150-300 GPa pressure range. Zero-point energy-corrected convex hull analysis identifies multiple stable superconducting phases, including R3m-Zr2H17 at 300 GPa and P6/mmm-LaZr2H24 at 200 GPa, both of which are thermodynamically and dynamically stable and exhibit strong electron-phonon coupling. Solution of the Eliashberg equations predicts high superconducting transition temperatures of Tc = 209 K for R3m-Zr2H17 at 300 GPa and Tc = 202 K for P6/mmm-LaZr2H24 at 200 GPa. In addition to these stable phases, we identify a high-symmetry metastable compound, P6m2-LaZrH18, which lies just 0.027 eV/atom above the convex hull yet remains dynamically stable and exhibits a high predicted Tc of 206 K at 300 GPa. We find that, across all phases, the elevated Tc correlates with the high-symmetry structure with dense hydrogen cages, favorable electron counts per hydrogen, and a large hydrogen-derived density of states at the Fermi level. Finally, a random- forest machine learning model, trained on diverse hydrides superconductivity data, reproduces these structure-property trends across predicted structures, enabling to identify potential hydrides with high predicted Tc for targeted follow-up calculations and future high-pressure experiments.
△ Less
Submitted 12 March, 2026;
originally announced March 2026.
-
Unveiling potential candidates for rare-earth-free permanent magnet and magnetocaloric effect applications: a high throughput screening in Fe-N alloys
Authors:
Qiang Gao,
Ergen Bao,
Ijaz Shahid,
Hui Ma,
Xing-Qiu Chen
Abstract:
Based on high-throughput density functional theory calculations, we have found 49 ferromag-netic cases in FexN1-x (0<x<1) compounds, focusing especially on permanent magnet and giant magnetocaloric effect applications. It is found that 15 compounds are potential permanent mag-nets with a magneto-crystalline anisotropy energy more than 1 MJ/m3, filling in the gap of appli-cation spectrum between hi…
▽ More
Based on high-throughput density functional theory calculations, we have found 49 ferromag-netic cases in FexN1-x (0<x<1) compounds, focusing especially on permanent magnet and giant magnetocaloric effect applications. It is found that 15 compounds are potential permanent mag-nets with a magneto-crystalline anisotropy energy more than 1 MJ/m3, filling in the gap of appli-cation spectrum between high-performance and widely used permanents. Among the potential permanent magnets, Fe2N can be classified as a hard magnet while the other 14 compounds can be classified as semi-hard magnets. According to the calculations of magnetic deformation proxy, 40 compounds are identified as potential giant magnetocaloric effect candidates. We suspect that Fe-N compounds provide fine opportunities for applications in both rare-earth free permanent magnets and magnetocaloric effect.
△ Less
Submitted 2 January, 2025;
originally announced January 2025.
-
Néel vector-dependent anomalous transport in altermagnetic metal CrSb
Authors:
Tianye Yu,
Ijaz Shahid,
Peitao Liu,
Ding-Fu Shao,
Xing-Qiu Chen,
Yan Sun
Abstract:
Altermagnets are predicted to exhibit anomalous transport phenomena, such as the anomalous Hall and Nernst effects, as observed in ferromagnets but with a vanishing net magnetic moment, akin to antiferromagnets. Despite their potential, progress has been limited due to the scarcity of metallic altermagnets. Motivated by the recent discovery of the altermagnetic metal CrSb, we conducted a systemati…
▽ More
Altermagnets are predicted to exhibit anomalous transport phenomena, such as the anomalous Hall and Nernst effects, as observed in ferromagnets but with a vanishing net magnetic moment, akin to antiferromagnets. Despite their potential, progress has been limited due to the scarcity of metallic altermagnets. Motivated by the recent discovery of the altermagnetic metal CrSb, we conducted a systematic study of its electrical and thermoelectric transport properties, using first-principles calculations. CrSb exhibits low magnetocrystalline anisotropy energy, enabling the manipulation of the Néel vector in CrSb films through a suitable ferromagnetic substrate. The anomalous Hall and Nernst conductivities reach their maximum when the Néel vector is aligned along $\frac{1}{2}$\textbf{\textit{a}}+\textbf{\textit{b}}. The origins of both conductivities were analyzed in terms of Berry curvature distribution. Our results demonstrate that CrSb provides a good platform for investigating the Néel vector-dependent anomalous transport in altermagnetic metals.
△ Less
Submitted 6 May, 2025; v1 submitted 17 December, 2024;
originally announced December 2024.
-
The Fe-N system: crystal structure prediction, phase stability, and mechanical properties
Authors:
Ergen Bao,
Jinbin Zhao,
Qiang Gao,
Ijaz Shahid,
Hui Ma,
Yixiu Luo,
Peitao Liu,
Yan Sun,
Xing-Qiu Chen
Abstract:
Nitriding introduces nitrides into the surface of steels, significantly enhancing the surface me-chanical properties. By combining the variable composition evolutionary algorithm and first-principles calculations based on density functional theory, 50 thermodynamically stable or metastable Fe-N compounds with various stoichiometric ratios were identified, exhibiting also dynamic and mechanical sta…
▽ More
Nitriding introduces nitrides into the surface of steels, significantly enhancing the surface me-chanical properties. By combining the variable composition evolutionary algorithm and first-principles calculations based on density functional theory, 50 thermodynamically stable or metastable Fe-N compounds with various stoichiometric ratios were identified, exhibiting also dynamic and mechanical stability. The mechanical properties of these structures were systemati-cally studied, including the bulk modulus, shear modulus, Young's modulus, Poisson's ratio, Pugh's ratio, Cauchy pressure, Klemen parameters, universal elastic anisotropy, Debye tempera-ture, and Vickers hardness. All identified stable and metastable Fe-N compounds were found in the ductile region, with most exhibiting homogeneous elastic properties and isotropic metallic bonding. As the nitrogen concentration increases, their bulk moduli generally increase as well. The Vickers hardness values of Fe-N compounds range from 3.5 to 10.5 GPa, which are signifi-cantly higher than that of pure Fe (2.0 GPa), due to the stronger Fe-N bonds strength. This study provides insights into optimizing and designing Fe-N alloys with tailored mechanical properties.
△ Less
Submitted 26 November, 2024;
originally announced November 2024.