Structural transition region of liquid Mg–Li alloys

Abstract

The local structural, dynamical, and thermodynamic properties of liquid Mg–Li alloys at 973K have been investigated using ab initio molecular dynamics simulation. The calculated pair-correlation functions agree well with the experimental results for pure Mg and Li. The local atomic structures have been characterized by the coordination number, bonded pair, and Voronoi polyhedron analysis. A structural transition region is found in the composition range from 12.5at.% Li to 31.25at.% Li: the close packing local atomic structures begin to transform to bcc type, which are dominated by the structural changes around Mg atoms on the effect of Li addition. The inflection point of calculated mixing enthalpy curve is also located in this region, supporting the transition of local atomic structures. Owing to the structural transition, the self-diffusion coefficients of Mg and Li change with different tendencies as Li content increasing. In addition, the interaction between Mg and Li atoms is evaluated by the quantity of charge transfer in liquid Mg–Li alloys. According to the quasi-chemical approximation model, charge transfer is confirmed as the key-factor of interaction energy.