Thermodynamic modeling of the Si-Y system aided by first-principles and phonon calculations

Abstract

Thermodynamic modeling of the Si-Y binary system has been performed by the CALPHAD (CALculation of PHAse Diagram) method based on phase diagram and thermochemical data in the literature combined with Gibbs energies of end-members of compounds predicted by first-principles phonon calculations. In particular, non-stoichiometric compounds Si2Y and Si3Y5 are modelled to accommodate their homogeneity ranges in terms of two-sublattice models (Si,Y)2(Si,Y) and (Si)3(Si,Y)5, respectively. Formation of SiY is treated as a peritectic reaction according to experimental results, instead of an eutectic one as described in the previous models. The calculated phase equilibriums and thermodynamic properties are in a satisfactory agreement with available experimental data.