Effects of refractory elements on the structure and dynamics of molten Ni: An ab initio molecular dynamics study

The effects of minor refractory elements (Re, W and Ta) on the structure and dynamics of molten Ni are studied by ab initio molecular dynamics simulations. The results show that minor additions of refractory elements would not significantly change the structure of liquid Ni. However, the local structure around Ta is quite different from that around Re or W. In the liquid Ni alloys, the 15lm-type bond pairs dominate. As temperature increases, the numbers of 16lm- and 15lm-type bond pairs would decrease while those of 14lm- and 13lm-type bond pairs would increase. The Ni self-diffusion coefficient of pure Ni shows a temperature dependence described by the Arrhenius law. With the addition of Re and W, the Ni self-diffusion coefficients still exhibit an Arrhenius relationship. However, the self-diffusion of Ni deviates from the Arrhenius law with the addition of Ta.