Comparative classical and ab initio Molecular Dynamics study of molten and glassy germanium dioxide

TL;DR

This study compares classical and ab initio molecular dynamics simulations of germanium dioxide to evaluate structural and dynamic properties, finding good agreement with experimental data and confirming the validity of classical potentials.

Contribution

It provides a direct comparison between classical pair potential and ab initio methods for molten and glassy GeO2, validating classical MD results against experiments.

Findings

Classical MD with OE potential closely matches experimental structure.

Ab initio CPMD shows slightly softer structures but similar accuracy.

High-temperature dynamics align with mode coupling theory.

Abstract

A Molecular Dynamics (MD) study of static and dynamic properties of molten and glassy germanium dioxide is presented. The interactions between the atoms are modelled by the classical pair potential proposed by Oeffner and Elliott (OE) [Oeffner R D and Elliott S R 1998, Phys. Rev. B, 58, 14791]. We compare our results to experiments and previous simulations. In addition, an ab initio method, the so-called Car-Parrinello Molecular Dynamics (CPMD), is applied to check the accuracy of the structural properties, as obtained by the classical MD simulations with the OE potential. As in a similar study for SiO2, the structure predicted by CPMD is only slightly softer than that resulting from the classical MD. In contrast to earlier simulations, both the static structure and dynamic properties are in very good agreement with pertinent experimental data. MD simulations with the OE potential are also used to study the relaxation dynamics. As previously found for SiO2, for high temperatures the dynamics of molten GeO2 is compatible with a description in terms of mode coupling theory.