Excess Vibrational Modes and the Boson Peak in Model Glasses

The excess low-frequency normal modes for two widely used models of glasses are 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. Our understanding of liquids is based on the idea that liquid structure is largely determined by strong shortranged repulsions and that the longer-ranged attractions can be treated as a perturbation [1]. Similar considerations were used to study jamming at zero temperature as a function of density � [2,3]. When potentials are repulsive and have a finite range, there is a sharp jamming transition