Analysis of ab-initio total energies obtained by different DFT implementations

TL;DR

This study compares total energy calculations from three different DFT software packages and methods to assess their consistency and guide their use in crystal structure prediction.

Contribution

It evaluates the consistency of three DFT codes using different approaches for binary alloys, analyzing the impact of computational choices on energy results.

Findings

Different alloy systems show varying sensitivity to computational parameters.

The study explains energy differences through angular variation of potentials.

Results guide the application of KKR methods in structure prediction.

Abstract

Ab-initio crystal structure prediction depends on accurate calculation of the energies of competing structures. Many DFT codes are available that utilize different approaches to solve the Kohn-Sham equation. We evaluate the consistency of three software packages (WIEN2k, VASP and MuST) that utilize three different methods (FL-APW, plane-wave pseudopotential and the KKR-Green's Function methods) by comparing the relative total energies obtained for a set of BCC and FCC binary metallic alloys. We focus on the impact of choices such as muffin-tin $vs.$ full-potential, angular momentum cutoff and other important KKR parameters. Different alloy systems prove more or less sensitive to these choices, and we explain the differences through study of the angular variation of their potentials. Our results can provide guidance in the application of KKR as a total energy method for structure prediction.