The effect of double counting, spin density, and Hund interaction in the different DFT+$U$ functionals

TL;DR

This paper systematically compares various DFT+U methods, analyzing how choices of double counting and exchange-correlation functionals affect electronic structure calculations, with implications for modeling magnetic and insulating materials.

Contribution

It provides a comprehensive analysis of different DFT+U formalisms, highlighting the impact of functional choices on electronic and magnetic properties, and offers practical guidelines for their use.

Findings

Different DFT+U formalisms exhibit distinct energy distributions and potential profiles.

Spin-dependent exchange-correlation functionals may lead to undesirable magnetic solutions.

The study includes real material examples, demonstrating practical implications.

Abstract

A systematic comparative study has been performed to better understand DFT$+U$ (density functional theory + $U$) method. We examine the effect of choosing different double counting and exchange-correlation functionals. The calculated energy distribution and the Hund-$J$ dependence of potential profile for representative configurations clearly show the different behaviors of each DFT$+U$ formalism. In particular, adopting spin-dependent exchange-correlation functionals likely leads to undesirable magnetic solution. Our analyses are further highlighted by real material examples ranging from insulating oxides (MnO and NiO) to metallic magnetic systems (SrRuO$_3$ and BaFe$_2$As$_2$). The current work sheds new light on understanding DFT$+U$ and provides a guideline to use the related methods.