Modeling of disordered materials: radial distribution function vs. vibrational spectra as a protocol for validation

TL;DR

This paper demonstrates that vibrational spectra are a more reliable validation protocol than radial distribution functions for molecular dynamics models of disordered materials, exemplified by hydrogenated amorphous silicon.

Contribution

It introduces vibrational spectra as a superior validation method over RDF for non-crystalline material models, supported by extensive ab-initio simulations.

Findings

RDF agreement alone is insufficient for model validation

Vibrational spectra better reproduce experimental features

Ab-initio simulations confirm the protocol's effectiveness

Abstract

As molecular dynamics is increasingly used to characterize non-crystalline materials, it is crucial to verify that the numerical model is accurate enough, consistent with experimental data and can be used to extract various characteristics of disordered systems. In most cases the only derived property used to test the "realism" of the models has been the radial distribution function. We report extensive ab-initio simulation of hydrogenated amorphous silicon that demonstrates that although agreement with the RDF is a necessary requirement, this protocol is insufficient for the validation of a model. We prove that the derivation of vibrational spectra is a more efficient and valid protocol to ensure the reproducibility of macroscopic experimental features.