Crystal structure optimisation using an auxiliary equation of state

TL;DR

This paper introduces a new efficient method for crystal structure optimization that predicts equilibrium volume from a single calculation using an auxiliary equation of state, reducing computational effort especially for complex structures.

Contribution

The authors propose a simple, single-point calculation-based approach for crystal structure optimization leveraging a known auxiliary equation of state, improving efficiency over traditional methods.

Findings

Validated on multiple materials with various density functionals.

Achieved accurate equilibrium volume predictions from single calculations.

Demonstrated applicability to complex materials like quaternary semiconductors and MOFs.

Abstract

Standard procedures for local crystal-structure optimisation involve numerous energy and force calculations. It is common to calculate an energy-volume curve, fitting an equation of state around the equilibrium cell volume. This is a computationally intensive process, in particular for low-symmetry crystal structures where each isochoric optimisation involves energy minimisation over many degrees of freedom. Such procedures can be prohibitive for non-local exchange-correlation functionals or other 'beyond' density functional theory electronic structure techniques, particularly where analytical gradients are not available. We present a simple approach for efficient optimisation of crystal structures based on a known equation of state. The equilibrium volume can be predicted from one single-point calculation, and refined with successive calculations if required. The approach is validated for PbS, PbTe, ZnS and ZnTe using nine density functionals, and applied to the quaternary semiconductor Cu$_{2}$ZnSnS$_{4}$ and the magnetic metal-organic framework HKUST-1.