Ab initio and thermodynamic investigation on the Ca–H system

The thermodynamic properties of the Ca–H system are evaluated by combining the CALPHAD approach with ab initio predictions. The Gibbs free energies of the individual phases are thermodynamically modeled, where the model parameters are obtained from best-fit optimizations to combined experimental data and ab initio thermodynamic predictions. The ab initio thermodynamic predictions are based upon density functional theory ground state minimizations and finite displacement lattice dynamics. The predictions are proved effective in the assessments whenever experimental measurements are lacking or not feasible. It is demonstrated that the obtained phase equilibria and thermodynamic properties have shown satisfactory agreement with the experimental data in the literature as well as the ab initio calculations from the present work.

► The first thermodynamic investigation on the Ca–H system.
► The first determination on the crystal structure of βCaH2 with FM-3M symmetry.
► A set of self-consistent thermodynamic parameters was derived for the Ca–H system.