Quantum atomic delocalization vs. structural disorder in amorphous silicon

Instituto de Ciencia de Materiales, CSIC, Campus de Cantoblanco, 28049 Madrid, Spain Institut für Theoretische Festkörperphysik, Universität Karlsruhe D-76128 Karlsruhe, Germany

Received: 4 December 1998
Accepted: 26 October 1998

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.