The first principle research of CaO and MgO particulate heterogeneous nucleation in Mg alloys

Based on first-principles density functional theory, the adhesion, stability and bonding properties of the interfaces between (0001) plane of Mg and (1 1 1) plane of oxide (MgO and CaO) were investigated systematically. Meanwhile, the heterogeneous nucleation ability of these oxide particles in Mg melt were elucidated. The results demonstrated that the stability of the O-terminated surface was higher than that of the X-termination of XO(1 1 1) surface under high oxidation potential, and the stability of the X-terminated surface gradually increased with decreasing the oxidation potential. The interfacial adhesion work of Mg/XO-O was higher than that of Mg/XO-X in the same stacking order, indicating that the interface stability of Mg/XO-O was higher than Mg/XO-X. In addition, the results of interface local charge function and Bader charge showed that the atomic charges on the Mg(0001) surface would transfer to the oxygen atoms on the o-termination of XO(1 1 1) surface to form ionic bond. The ionic bond strength at the Mg/MgO-O interface was higher than ionic bond strength in Mg/CaO-O interface. Therefore, MgO can be used as a more effective nucleation substrate in Mg melt than CaO.