Change of dynamical cooperativity in the glass-transition regime: computer modelling results for Ni0.5Zr0.5

Abstract

Results are reported of molecular dynamics simulations for an amorphous Ni0.5Zr0.5 model. Presented are the mean squares displacements of the atoms on the mus-scale at 700, 785 and 900 K, well below the dynamical glass temperature T-c = 1120 K. According to the data, the dynamical cooperativity characteristic for dense melts around T, that is irreversible motion of individual chains of atoms, becomes ineffective at low temperatures. Here a new type of higher organised dynamical cooperativity seems to take over, characterised by the occurrence of avalanches of mutually triggered transitions of chain of atoms separated by periods of calmness. (C) 2002 Elsevier Science B.V. All rights reserved.