Oxidation State Dynamics and Emerging Patterns in Magnetite

TL;DR

This paper introduces a hybrid Monte Carlo/Molecular Dynamics method to accurately model ion dynamics and oxidation state patterns in magnetite, capturing complex behaviors at relevant scales beyond traditional electronic structure calculations.

Contribution

A novel hybrid MC/MD approach based on iron oxidation state exchange for detailed atomistic modeling of magnetite and related materials.

Findings

Confirmed accuracy through comparison with density functional theory

Observed lattice distortions stabilizing excess charges

Identified critical surface thickness for oxidation state transition

Abstract

Magnetite is an important mineral with many interesting applications related to its magnetic, electrical and thermal properties. Typically studied by electronic structure calculations, these methods are unable to capture the complex ion dynamics at relevant temperatures, time and length scales. We present a hybrid Monte Carlo/Molecular Dynamics (MC/MD) method based on iron oxidation state exchange for accurate atomistic modelling of bulk magnetite, magnetite surfaces and nanoparticles that captures the complex ionic dynamics. By comparing oxidation state patterns with those obtained from density functional theory, we confirmed the accuracy of our approach. Lattice distortions leading to the stabilisation of excess charges and a critical surface thickness at which the oxidation states transition from ordered to disordered were observed. This simple yet efficient approach paves the way for elucidating aspects of oxidation state ordering of inverse spinel structures in general and battery materials in particular.