Pressure-induced lattice-dynamical stability and superconductivity of ternary pentahydride MgNiH5

Abstract

We predict the existence of ternary pentahydride MgNiH5, adopting a hexagonal structure with a space group P63/mmc, at high pressure. Typically, the clarity of structural-phase stability could be demonstrated by thermodynamical and dynamical stabilities. Herein, we introduce a critical temperature (Tc) superconductivity of the ternary pentahydride, based on the isotropic Éliashberg equation. The Tc is estimated by directly solving the Allen-Dynes equation, with a remarkable value of Tc at 25.6 K. Under the compressing pressure from 100 to 300 GPa, the Tc of MgNiH5 is determined by means of the phonon-mediated superconductivity, arising particularly from a magnitude of partial electron-phonon coupling. Our calculation paves the way for achieving a ratio and a Tc superconductivity in the family of ternary polyhydride.