Lattice dynamics and thermophysical properties of h.c.p. Os and Ru from the quasi-harmonic approximation

TL;DR

This paper uses first-principles calculations within the quasi-harmonic approximation to study phonon frequencies and thermophysical properties of h.c.p. Os and Ru, comparing anisotropic and simplified models with experimental data.

Contribution

It provides a detailed first-principles analysis of phonon and thermodynamic properties of Os and Ru, including anisotropic effects, within the quasi-harmonic approximation.

Findings

Good agreement with experimental thermophysical data

Anisotropic treatment improves accuracy over simplified models

Temperature-dependent lattice parameters and thermal expansion calculated

Abstract

We report first-principles phonon frequencies and anharmonic thermodynamic properties of h.c.p. Os and Ru calculated within the quasi-harmonic approximation, including Gruneisen parameters, temperature-dependent lattice parameters, thermal expansion, and isobaric heat capacity. We discuss the differences between a full treatment of anisotropy and a simplified approach with a constant c/a ratio. The results are systematically compared with the available experimental data and an overall satisfactory agreement is obtained.