The temperature dependence of the atomic diffusion and the distribution of interatomic voids in Ni81B19 was studied by molecular-dynamics simulations, at temperatures less than and greater than the glass transition temperature. The voids could be classified according to the number of surrounding atoms and, for each class, the void volumes were log-normally distributed. This type of distribution was also observed in crystalline face-centered cubic Ni and Ni3B models at room temperature. With increasing temperature, the number of larger voids increased, because of the thermal expansion and as a result of the coalescence of smaller voids. Voids with a volume larger than the activation volume for diffusion were considered to be defects. The defect concentration at room temperature was ≈10-5 and exhibited an Arrhenius temperature dependence. This classification of the interatomic empty space led to a plausible identification of sites in the structure that acted as diffusion catalysts.

Temperature Dependence of Diffusion and Structural Defects in a Molecular-Dynamics Model of Amorphous Ni81B19. Van Ee, L.D., Thijsse, B.J., Sietsma, J.: Journal of Non-Crystalline Solids, 1998, 232-234, 212-8