LOW-FREQUENCY VIBRATIONS AND RELAXATIONS IN GLASSES

Using molecular dynamics a glass of soft spheres, quenched to zero temperature, is produced and its vibrational behaviour investigated by an analysis of the normal modes. In addition to localized modes with high frequencies, one finds (quasi)localized modes with low frequencies which are centred around structural anomalies of the glass. The glass is then heated in stages to 12.5% of the glass temperature and is allowed to relax. In the relaxed glasses, again (quasi)localized low-frequency modes are found, with effective masses ranging upward from about 10 atomic masses as in the original glasses. The observed relaxations have similar effective masses and are closely related to the (quasi)localized vibrations.