Atomic structure and diffusion in Cu60Zr40 metallic liquid and glass: molecular dynamics simulations
YL Sun and J Shen and AA Valladares, JOURNAL OF APPLIED PHYSICS, 106, 073520 (2009).
Temperature effects on the structural evolution and diffusivity of Cu60Zr40 in the liquid and glassy states were studied by molecular dynamics simulations using the Finnis-Sinclair potential. The pair distribution functions and common-neighbor analysis were used to investigate the structural variations. It is found that the amount of pentagonal bipyramids increases sharply in a short temperature range of about 200 K above the glass transition temperature T-g, leading to the increasing of the icosahedral cluster centered by Cu atom and larger Kasper polyhedral cluster centered by Zr atom. The mean square displacement and the self part of the van Hove function were calculated to evaluate the relaxation and transport properties. The cage effect is found to appear at 1100 K. The mode-coupling theory equation is more suitable than the Vogel-Fulcher-Tammann equation to describe the change in diffusivity in the liquid state. The critical temperature T-c, a predicted glass transition temperature in mode-coupling theory, for Cu60Zr40 glass former is 1008.2 K. At temperatures near T-c, there is a dynamic crossover. In supercooled liquid state, the dynamic heterogeneity is detected. The comparison of the activation enthalpies of the two components shows that the small atoms transport faster obeying the size effect. (C) 2009 American Institute of Physics. doi:10.1063/1.3245324
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