Phase Stability and Properties of Manganese Oxide Polymorphs: Assessment and Insights from Diffusion Monte Carlo

TL;DR

This paper uses diffusion Monte Carlo to accurately determine the energy ordering and properties of manganese oxide polymorphs, providing insights into their electronic structure and correcting limitations of other computational methods.

Contribution

It demonstrates that fixed node diffusion Monte Carlo correctly predicts the stable manganese oxide structure and offers detailed analysis of electronic properties missing in other theories.

Findings

DMC finds rock salt more stable than zincblende

DMC band gaps align with the lower gap of zincblende

Calculated gaps overestimate experimental values

Abstract

We present an analysis of the polymorphic energy ordering and properties of the rock salt and zincblende structures of manganese oxide using fixed node diffusion Monte Carlo (DMC). Manganese oxide is a correlated, antiferromagnetic material that has proven to be challenging to model from first principles across a variety of approaches. Unlike conventional density functional theory and some hybrid functionals, fixed node diffusion Monte Carlo finds the rock salt structure to be more stable than the zincblende structure, and thus recovers the correct energy ordering. Analysis of the site-resolved charge fluctuations of the wave functions according to DMC and other electronic structure descriptions give insights into elements that are missing in other theories. While the calculated band gaps within DMC are in agreement with predictions that the zincblende polymorph has a lower band gap, the gaps themselves overestimate reported experimental values.