Modified Becke-Johnson potential investigation of half-metallic Heusler compounds

TL;DR

This study evaluates the effectiveness of the Tran-Blaha modified Becke-Johnson potential in predicting electronic structures of half-metallic Heusler compounds, finding it enhances certain gaps but worsens agreement with experimental densities of states.

Contribution

The paper provides a comprehensive assessment of mBJLDA's performance for half-metallic Heusler compounds, highlighting its limitations compared to PBE.

Findings

mBJLDA significantly increases half-metallic gaps.

mBJLDA worsens agreement with experimental densities of states.

PBE better predicts ground state properties like hyperfine fields.

Abstract

We have investigated the electronic structures of various potentially half-metallic Heusler compounds with the Tran-Blaha modified Becke-Johnson (TB-mBJLDA) potential within the density functional theory. The half-metallic gaps are considerably enhanced with respect to values from the Perdew-Burke-Ernzerhof (PBE) functional. In particular the unoccupied densities of states are modified by mBJLDA, and agreement with experiment is considerably worse than for PBE. The agreement of the densities of states can be improved by reducing the Tran-Blaha parameter c. However, ground state properties such as the hyperfine fields are more accurately described by PBE than by mBJLDA. Despite its success for ionic and covalent semiconductors and insulators, we conclude that mBJLDA is not a suitable approximation for half-metallic Heusler compounds.