Structural dynamics on the μs scale in molecular-dynamics simulated, deeply undercooled, glass-forming Ni0.5Zr0.5

Results are reported from molecular dynamics (MD) simulations on the structural dynamics in a Ni0.5Zr0.5 metallic-glass model. Presented are, in particular, the mean squares displacements (MSD) for Ni and Zr atoms over a time window of 0.7 μs at 700 K. They indicate a change of the system between temporarily arrested and dynamical transient phases. The former extend up to 0.3 μs. From the data, diffusion coefficients are estimated and related to those from earlier simulations for higher temperatures. Atomic chain transitions in two-centre configurations are identified as the basic mechanisms of the dynamics. For some cases, the barrier heights of the centres are calculated and the pressure effect deduced. The latter indicates an activation volume of 7×10−30 m3, a value comparable to the experimental activation volume of diffusion in NiZr.