Evaluation of Reverse Monte Carlo Models based on Molecular Dynamics Simulations: A Case Study of Ion Conducting Network Glasses

TL;DR

This study assesses the accuracy of Reverse Monte Carlo models in representing the structure of ion-conducting glasses by comparing them with molecular dynamics simulations, highlighting strengths in short-range order and limitations in medium-range features.

Contribution

It provides a systematic evaluation of RMC models against MD simulations for amorphous glasses, emphasizing the importance of initial configurations and medium-range order accuracy.

Findings

RMC models accurately reproduce short-range order features.

Medium-range order features are poorly captured by RMC.

Starting configurations influence medium-range structural features.

Abstract

We investigate the quality of structural models generated by the Reverse Monte Carlo (RMC) method in a typical application to amorphous systems. To this end we calculate surrogate diffraction data from a Li2O-SiO2 molecular dynamics (MD) simulation and use the total scattering function, in addition to minimal pair distances and coordination numbers of silicon (oxygen) to oxygen (silicon) ions, as input for the RMC modeling. Then we compare partial radial distribution functions, coordination numbers, bond angles, and ring sizes predicted by the RMC models with those of the MD system. It is found that partial distributions functions and properties on small lengths scales, as distributions of coordination numbers and bond angles, are well reproduced by the RMC modeling. Properties in the medium-range order regime are, however, not well captured, as is demonstrated by comparison of ring size distributions. Due care therefore has to be exercised when extracting structural features from RMC models in this medium-range order regime. In particular we show that the occurrence of such features can be a mere consequence of the chosen starting configuration.