First-principles study of structural stability and elastic properties of MgPd_(3) and its hydride

Theoretical study of structural stability and elastic properties ofα-andβ-MgPd_(3)intermetallic compounds as well as their hydrides have been carried out based on density functional theory.The results indicateα-MgPd_(3)is more stable thanβphase with increased stability in their hydrides.The calculated elastic constants ofα-MgPd_(3)are overall larger thanβphase.After hydrogenation,the elastic constants are enlarged.And the elastic moduli exhibit similar tendency.The anisotropy ofα-MgPd_(3)is larger thanβphase,and the hydrides demonstrate larger anisotropy.Their ductility follows the order ofα-MgPd_(3)H_(0.5)<α-MgPd_(3)<β-MgPd_(3)H<β-MgPd_(3).Compared withβphase,higher Debye temperature ofα-MgPd_(3)implies stronger covalent interaction,and the Debye temperature of hydrides increases slightly.The electronic structures demonstrate that the Pd-Pd interaction is stronger than Pd-Mg,and Pd-H bonds play a significant role in the phase stability and elastic properties of hydrides.