Computer simulation of thermodynamic factors in Ni-Al and Cu-Ag liquid alloys

In this paper, thermodynamic factors of two liquid alloys, Ni-Al and Cu-Ag, are studied by means of molecular dynamics simulation (with the most reliable embedded-atom method potentials)over both wide composition and temperature ranges. For the first time, a comparison is possible between Ni-Al (with a strong ordering tendency)and Cu-Ag (with a strong phase separation tendency). The calculations were performed based on the evaluation of pair correlation functions and mean square thermal fluctuations in composition (the thermodynamic limit of one of the Bhatia-Thornton partial structure factors, S_CC). A novel but straightforward computational approach is developed and successfully applied to these calculations. In order to ensure reliability of the employed model description of Ni-Al liquid alloys, the calculated partial and total structure factors are verified by data from neutron scattering experimental measurements (performed as part of this work as well as also being available in the literature). Good agreement is observed for the structure factor S_CC for all values of q including the thermodynamic limit q→0. On the other hand, for the total and Faber-Ziman partial structure factors, good agreement is observed only for q values outside the limit q→0. In addition, a similarity between the shapes of the thermodynamic factor composition dependence and the shape of the liquidus lines in both Ni-Al and Cu-Ag liquid alloys is noted. We highlight the significance of the presented computational and experimental study for developing and testing various models and frameworks.