Special quasirandom structure in heterovalent ionic systems

TL;DR

This paper explores the application of special quasirandom structures (SQS) to heterovalent ionic systems, revealing limitations in property convergence and proposing a linear extrapolation method for accurate property estimation.

Contribution

It demonstrates that SQS can be adapted for heterovalent ionic systems and introduces a linear extrapolation technique to estimate properties of disordered structures.

Findings

Physical properties do not converge with supercell size in heterovalent ionic systems.

Correlation functions of long-range clusters are not optimized in SQS.

Linear extrapolation using inverse supercell size estimates properties accurately.

Abstract

The use of a special quasirandom structure (SQS) is a rational and efficient way to approximate random alloys. A wide variety of physical properties of metallic and semiconductor random alloys have been successfully estimated by a combination of an SQS and density functional theory (DFT) calculation. Here, we investigate the application of an SQS to the ionic multicomponent systems with configurations of heterovalent ions, including point-charge lattices, MgAl$_2$O$_4$ and ZnSnP$_2$. It is found that the physical properties do not converge with the supercell size of the SQS. This is ascribed to the fact that the correlation functions of long-range clusters larger than the period of the supercell are not optimized in the SQS. However, we demonstrate that the physical properties of the perfectly disordered structure can be estimated by linear extrapolation using the inverse of the supercell size.