Thermodynamic modeling of the Si-Sr system

Thermodynamic modeling of the Si-Sr system was carried out using the CALPHAD method. In this system, three of the intermetallic compounds, Sr₂Si,Sr₅Si₃,SrSi, were considered to be stoichiometric and SrSi₂ was modeled as a non-stoichiometric phase. For the liquid phase, two different models were used. In one case, Sr and Si were assumed to constitute a random solution, with its excess Gibbs energy being described through the Redlich-Kister polynomial. In the second case, the liquid phase was described through the associate model, considering the species Si, Sr and SrSi. The terminal solid solutions, (β Sr), (α Sr) and (Si), are treated with negligible solubilities. A set of self-consistent thermodynamic parameters is obtained by considering experimental phase equilibria, measurements of the mixing enthalpy in the liquid phase, as well as measured and calculated-via first-principles methods based on density functional theory-formation enthalpies of the intermetallic compounds.