Direct coupling of first-principles calculations with replica exchange Monte Carlo sampling of ion disorder in solids

TL;DR

This paper presents a method to perform configurational sampling of disordered oxides directly from first principles using replica exchange Monte Carlo coupled with density functional theory, avoiding fitted models.

Contribution

It demonstrates the feasibility of direct first-principles sampling of disordered solids, bypassing the need for cluster expansion models, enabling study of complex disordered systems.

Findings

Successful calculation of temperature-dependent inversion in MgAl₂O₄

Shows potential for studying systems with large lattice deformation

Enables investigation of systems with dominant long-range interactions

Abstract

We demonstrate the feasibility of performing sufficient configurational sampling of disordered oxides directly from first principles without resorting to the use of fitted models such as cluster expansion. This is achieved by harnessing the power of modern-day cluster supercomputers using the replica exchange Monte Carlo method coupled directly with structural relaxation and energy calculation performed by density functional codes. The idea is applied successfully to the calculation of the temperature-dependence of the degree of inversion in the cation sublattice of MgAl$_2$O$_4$ spinel oxide. The possibility of bypassing fitting models will lead to investigation of disordered systems where cluster expansion is known to perform badly: for example, systems with large lattice deformation due to defects, or systems where long-range interactions dominate such as electrochemical interfaces.