  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.
