Anisotropic thermal expansion of bismuth from first principles

TL;DR

This study uses first-principles calculations to analyze the anisotropic thermal expansion of bismuth, revealing how directional properties influence its thermal behavior with good experimental agreement.

Contribution

The paper presents a first-principles approach to compute anisotropic thermal expansion and elastic properties of bismuth, highlighting the origin of anisotropy from directional compressibilities and Grüneisen functions.

Findings

Good agreement with experimental elastic constants

Anisotropy in thermal expansion linked to directional properties

Quantitative analysis of directional Grüneisen functions

Abstract

Some anisotropy in both mechanical and thermodynamical properties of bismuth is expected. A combination of density functional theory total energy calculations and density functional perturbation theory in the local density approximation is used to compute the elastic constants at 0 K using a finite strain approach and the thermal expansion tensor in the quasiharmonic approximation. The overall agreement with experiment is good. Furthermore, the anisotropy in the thermal expansion is found to arise from the anisotropy in both the directional compressibilities and the directional Gr\"uneisen functions.