Stability, thermal and mechanical properties of PtxAly compounds

The stability, thermal and mechanical properties of PtxAly intermetallic compounds are investigated by density functional theory (DFT). The cohesive energy and formation enthalpy of PtxAly phases show that they are thermodynamically stable structures and these are in good agreement with the experiments. The heat capacity of the compounds is calculated by quasi-harmonic approximation (QHA) method. The thermal expansion coefficient as a function of temperature for each compound is also discussed. The elastic properties such as bulk modulus, Young’s modulus are evaluated by Viogt–Reuss–Hill approximation. The anisotropic properties of sound velocities for the PtxAly compounds are explored. The calculated Poisson’s ratio varies from 0.26 to 0.39 for PtxAly phases and the bonds in the compounds are mainly metallic and covalent types.