Effect of the double-counting functional on the electronic and magnetic properties of half-metallic magnets using the GGA+U method

TL;DR

This study compares the effects of different double-counting functionals in GGA+U calculations on the electronic and magnetic properties of half-metallic magnets, highlighting the importance of choosing the appropriate functional.

Contribution

It systematically evaluates the impact of AL and AMF double-counting functionals on GGA+U results for half-metallic magnets, revealing the significance of functional choice.

Findings

AMF yields results similar to GGA

AL often leads to unphysical magnetic properties

Choice of double-counting functional is crucial

Abstract

Methods based on the combination of the usual density functional theory (DFT) codes with the Hubbard models are widely used to investigate the properties of strongly correlated materials. Using first-principle calculations we study the electronic and magnetic properties of 20 half-metallic magnets performing self-consistent GGA+U calculations using both the atomic-limit (AL) and around-mean-field (AMF) functionals for the double counting term, used to subtract the correlation part from the DFT total energy, and compare these results to the usual generalized-gradient-approximation (GGA) calculations. Overall the use of AMF produces results similar to the GGA calculations. On the other hand the effect of AL is diversified depending on the studied material. In general the AL functional produces a stronger tendency towards magnetism leading in some cases to unphysical electronic and magnetic properties. Thus the choice of the adequate double-counting functional is crucial for the results obtained using the GGA+U method.