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arXiv · 2507.15354

High pressure and temperature thermoelasticity of hcp osmium from ab initio quasi-harmonic theory

Xuejun Gong·Andrea Dal Corso
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Abstract

We present a systematic ab initio study of the thermoelastic properties of hcp osmium as functions of temperature and pressure within the quasi-harmonic approximation (QHA). The precision of the Zero Static Internal Stress Approximation (ZSISA) and of the volume-constrained ZSISA (V-ZSISA) are rigorously assessed. For osmium, we find negligible deviations between ZSISA and a full free energy minimization (FFEM) approach. Also, the V-ZSISA approximation influences the results very little, as we found already in beryllium, despite the markedly different behavior of the c/a ratio with temperature in the two metals. Our QHA-derived ECs show excellent agreement with available experimental data in the temperature range of 5-301 K, outperforming the results obtained from the quasi-static approximation (QSA). Additionally, we report the pressure-dependent QHA ECs at 5 K, 301 K, and 1000 K, spanning pressures from 0 to 150 kbar.

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Xuejun Gong, Andrea Dal Corso. 2025-07-21. High pressure and temperature thermoelasticity of hcp osmium from ab initio quasi-harmonic theory. https://doi.org/10.1103/j1sn-dqbl

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