Excess Vibrational Modes and the Boson Peak in Model Glasses

TL;DR

This paper investigates excess vibrational modes and the Boson peak in model glasses, showing that anomalous mode onset frequencies align with variational predictions based on excess contacts, despite high coordination numbers.

Contribution

It demonstrates that the onset of anomalous vibrational modes in glasses can be predicted by analyzing excess contacts, providing insight into vibrational anomalies in disordered solids.

Findings

Onset frequencies match variational predictions.

Excess contacts are mostly weak despite high coordination.

Vibrational energy analysis explains the Boson peak phenomena.

Abstract

The excess low-frequency normal modes for two widely-used models of glasses were studied at zero temperature. The onset frequencies for the anomalous modes for both systems agree well with predictions of a variational argument, which is based on analyzing the vibrational energy originating from the excess contacts per particle over the minimum number needed for mechanical stability. Even though both glasses studied have a high coordination number, most of the additional contacts can be considered to be weak.