Thermodynamic modeling of the Mg–Si system with the Kaptay equation for the excess Gibbs energy of the liquid phase

The Mg–Si system was re-modeled using the Kaptay equation Li=hi⋅exp(−T/ti)(i=0,1,2,…) to describe the excess Gibbs energy of the liquid phase. Compared with the previous assessments using a linear temperature dependence: Li=ai+bi⋅T(i=0,1,2,…) to describe this excess Gibbs energy, the artificial inverted miscibility gap at high temperature is removed. In order to clarify the discrepancies among the literature data concerning the enthalpy of formation for Mg2Si, a first-principles calculation was performed to compute this thermodynamic quantity. The calculated phase diagram and thermodynamic properties using the obtained thermodynamic parameters agree well with the experimental data.