Elastemp — A workflow to compute the quasi-harmonic temperature dependent elastic constants of materials

Abstract

Elastic constants characterize the stiffness of a material. A linear relationship between the stress and strain tensors in the limit of infinitesimal deformation is used to define and compute the elastic constants. Typically, this is computed at zero temperature by deforming the simulation box in one of the six directions and computing the stress tensor. Calculating elastic constants at finite temperature is more challenging owing to large fluctuations and thermal noise. Here, we introduce a semi-automated workflow — Elastemp, to obtain the quasi-harmonic elastic constants of materials as a function of temperature. The workflow integrates with electronic structure packages such as VASP and PHONOPY to get the quasi-harmonic energies. The workflow is capable of estimating the zero temperature elastic constants, thermal expansion coefficients of materials and temperature dependent elastic constants. The predictions for a set of representative test cases with different crystal symmetries (Al, Diamond, Titanium nitride (TiN) and α-Ti) are compared with experiments and used to demonstrate the efficacy of our workflow.