Localized relaxations in glasses

Using molecular dynamics the relaxations in a soft sphere glass and in Se-glass are studied at temperatures up to 30% of the glass temperature. A large number of jumps localized on typically more than 10 atoms are observed. Both jump length and number of participating atoms increases with temperature. Subsequent jumps are strongly correlated to each other and to the localized soft vibrations. The latter correlation is in qualitative agreement with the soft potential model but is much weaker than anticipated.