It was recalled that this metallic glass attained a temperature-dependent metastable equilibrium state before crystallization, and that a consistent picture of its properties in terms of a free-volume model has been obtained. The pressure dependence of the free volume of the glass was considered here. After bringing it to equilibrium at 563K under ambient pressures, annealing (12h) at the same temperature was carried out under hydrostatic pressures of up to 0.75GPa. The structural state of the glass after these treatments was monitored by means of differential scanning calorimetry, thus revealing that the glass-transition peak was clearly dependent upon the pressure which was applied during annealing. Interpretation of the glass-transition peak in terms of the free-volume model yielded a linear pressure dependence of the reduced free volume, with a values of 0.0025/GPa. By using this result, the activation volume for diffusion (0.011nm3) which had previously been deduced from the pressure dependence of Au diffusion in the same glass could be separated into a formation volume (0.005nm3), which reflected the pressure dependence of the concentration of diffusion carriers, and a migration volume (0.005nm3), which reflected the effect of the pressure upon diffusion itself. These values supported a cooperative mechanism for Au diffusion in this material; contrary to conclusions which were based only upon the activation volume.

G.Ruitenberg, P.De Hey, F.Sommer, J.Sietsma: Materials Science and Engineering A, 1997, 226-228, 397-400