Theoretical studies of the thermodynamic and mechanical properties of Mg-Pt system. An insight into phase equilibria

The Mg-Pt system is considered as a promising hydrogen storage material. Surprisingly, its phase diagram is unknown hence application of this alloy very limited due to undetermined phases stabilities. In this work ab initio calculations were utilized to determine constant pressure heat capacities and Gibbs energy changes in the temperature range between 0 and 1000 K, and mechanical properties. As a result of this calculation, a first, rough phase diagram of the Mg-Pt system was proposed. Moreover, a crystal structure for the MgPt phase was refined based on the mechanical and dynamical stability. The formation free energy changes determined for phases of the Mg-Pt system showed that the MgPt phase exhibited the most negative value. The elastic stiffness matrix elements C-ij were determined, as were mechanical properties such as Young's, bulk, shear moduli, Vicker's hardness, Poisson's ratio or the Debye temperatures of intermetallic phases from the Mg-Pt system.