Importance of intersite Hubbard interactions in $\beta$-MnO$_2$: A first-principles DFT+$U$+$V$ study

TL;DR

This study uses advanced first-principles DFT methods to analyze the importance of intersite Hubbard interactions in accurately modeling the properties of $eta$-MnO$_2$, emphasizing the role of both onsite and intersite parameters.

Contribution

It introduces a comprehensive DFT+$U$+$V$ approach with computed Hubbard parameters, highlighting the significance of intersite interactions and the choice of Hubbard projectors for transition-metal oxides.

Findings

Intersite $V$ is crucial for capturing Mn-O hybridization.

Orthogonalized Hubbard manifolds yield more accurate results.

The method stabilizes antiferromagnetic ordering consistent with experiments.

Abstract

We present a first-principles investigation of the structural, electronic, and magnetic properties of pyrolusite ($\beta$-MnO$_2$) using conventional and extended Hubbard-corrected density-functional theory (DFT+$U$ and DFT+$U$+$V$). The onsite $U$ and intersite $V$ Hubbard parameters are computed using linear-response theory in the framework of density-functional perturbation theory. We show that while the inclusion of the onsite $U$ is crucial to describe the localized nature of the Mn($3d$) states, the intersite $V$ is key to capture accurately the strong hybridization between neighboring Mn($3d$) and O($2p$) states. In this framework, we stabilize the simplified collinear antiferromagnetic (AFM) ordering (suggested by the Goodenough-Kanamori rule) that is commonly used as an approximation to the experimentally-observed noncollinear screw-type spiral magnetic ordering. A detailed investigation of the ferromagnetic and of other three collinear AFM spin configurations is also presented. The findings from Hubbard-corrected DFT are discussed using two kinds of Hubbard manifolds - nonorthogonalized and orthogonalized atomic orbitals - showing that special attention must be given to the choice of the Hubbard projectors, with orthogonalized manifolds providing more accurate results than nonorthogonalized ones within DFT+$U$+$V$. This work paves the way for future studies of complex transition-metal compounds containing strongly localized electrons in the presence of pronounced covalent interactions.