Influence of polarizability on metal oxide properties studied by molecular dynamics simulations

TL;DR

This study investigates how including oxygen ion polarizability in molecular dynamics simulations affects the accuracy of modeling metal oxide properties, showing its importance varies with temperature.

Contribution

It introduces and compares force fields with and without oxygen polarizability for silica, magnesia, and alumina, highlighting the impact on structural and thermodynamic properties.

Findings

Polarizable force fields improve bond angle and equation of state predictions.

Non-polarizable models suffice for radial distribution and lattice constants.

The significance of polarizability diminishes at higher temperatures.

Abstract

We have studied the dependence of metal oxide properties in molecular dynamics (MD) simulations on the polarizability of oxygen ions. We present studies of both liquid and crystalline structures of silica (SiO2), magnesia (MgO) and alumina (Al2O3). For each of the three oxides, two separately optimized sets of force fields were used: (i) Long-range Coulomb interactions between oxide and metal ions combined with a short-range pair potential. (ii) Extension of force field (i) by adding polarizability to the oxygen ions. We show that while an effective potential of type (i) without polarizable oxygen ions can describe radial distributions and lattice constants reasonably well, potentials of type (ii) are required to obtain correct values for bond angles and the equation of state. The importance of polarizability for metal oxide properties decreases with increasing temperature.