Thermodynamic assessment of the As-X (X=Si, Ge, Sn) binary systems

Abstract In the literature, there are no thermodynamic assessments of the As-Si and As-Sn binary systems, and the existing thermodynamic description for the As-Ge system is not reliable. Based on the critical evaluation of literature data including both phase equilibria and thermodynamic data, thermodynamic optimizations for the three binary systems were carried out by means of CALPHAD (CALculation of PHAse Diagrams) approach. The substitution solution model was used to describe the Gibbs energies of the solutions phases including liquid, (As), (βSn), (Ge) and (Si). All of the intermetallic compounds, i.e., AsSn, As3Sn4, AsGe, As2Ge, AsSi and As2Si, were modeled as stoichiometric compounds. In the present work, the enthalpies of formation for the intermetallic compounds in the As-Sn system were re-calculated through the first-principles method in view of the inconsistency for the enthalpies of formation reported in the literature. A set of self-consistent thermodynamic parameters for each binary system was obtained by means of Thermo-Calc software. A regularity for the melting points, enthalpies of melting and enthalpies of formation of the AsSi, AsGe, and AsSn is observed. The calculated results were in good agreement with the experimental data.