Quantum atomic delocalization vs. structural disorder in amorphous silicon

TL;DR

This study uses path-integral Monte Carlo simulations to explore how quantum effects influence atom delocalization and vibrational properties in amorphous silicon across a wide temperature range.

Contribution

It provides the first detailed analysis of quantum delocalization effects in amorphous silicon, highlighting their significance compared to structural disorder.

Findings

Quantum delocalization increases RDF peak width by 50% at low temperatures.

Anharmonic vibrations are more pronounced in amorphous silicon than in crystalline form.

Low-energy vibrational modes are localized on coordination defects.

Abstract

Quantum effects on the atom delocalization in amorphous silicon have been studied by path-integral Monte Carlo simulations from 30 to 800 K. The quantum delocalization is appreciable vs. topological disorder, as seen from structural observables such as the radial distribution function (RDF). At low temperatures, the width of the first peak in the RDF increases by a factor of 1.5 due to quantum effects. The overall anharmonicity of the solid vibrations at finite temperatures in amorphous silicon is clearly larger than in the crystalline material. Low-energy vibrational modes are mainly located on coordination defects in the amorphous material.