Tight-binding study of structure and vibrations of amorphous silicon

TL;DR

This paper employs a tight-binding approach to accurately model the structural, vibrational, and elastic properties of amorphous silicon, revealing insights into force constants, radial distribution function asymmetry, and zero-point effects.

Contribution

It introduces a novel tight-binding calculation that accurately describes amorphous silicon's properties and identifies limitations of the Stillinger-Weber potential.

Findings

Identifies unphysical features in the Stillinger-Weber potential.

Finds the first peak of the radial distribution function is asymmetric.

Quantifies zero-point broadening effects on the radial distribution function.

Abstract

We present a tight-binding calculation that, for the first time, accurately describes the structural, vibrational and elastic properties of amorphous silicon. We compute the interatomic force constants and find an unphysical feature of the Stillinger-Weber empirical potential that correlates with a much noted error in the radial distribution function associated with that potential. We also find that the intrinsic first peak of the radial distribution function is asymmetric, contrary to usual assumptions made in the analysis of diffraction data. We use our results for the normal mode frequencies and polarization vectors to obtain the zero-point broadening effect on the radial distribution function, enabling us to directly compare theory and a high resolution x-ray diffraction experiment.