Thermodynamic description of the Ge-Na and Ge-K systems using the CALPHAD approach supported by first-principles calculations

摘要

Thermodynamic optimization of the Ge-Na and Ge-K systems has been performed by means of the CALPHAD method combined with first-principles calculations. The enthalpies of formation of GeNa and GeK obtained via first-principles calculations are -16.88 and -20.90 kJ/mol atom, respectively. The liquid phase was modeled with the Redlich-Kister polynomial. The six intermetallic compounds (Ge _4Na, GeNa, GeNa _3, Ge _4K, GeK and GeK _3) were described as stoichiometric compounds. The Gibbs energy functions for individual phases in the Ge-Na and Ge-K systems were evaluated by considering both the first-principles computed enthalpies of formation and the experimental phase equilibrium data. A set of self-consistent thermodynamic parameters for the Ge-Na and Ge-K systems has been obtained, and the calculated results show a good agreement with the corresponding experimental data.