First-principles calculations of Mg2FeH6 under high pressures and hydrogen storage properties.

Abstract

We report on structural properties, elastic constants, mechanical and dynamical stabilities, electronic band structure, and hydrogen storage applications of Mg2FeH6 at zero and high-pressure effects. The work has been realized within the full-potential linearized augmented plane wave method. At zero pressure, the material under study is stable and has a ductile nature. The electronic structure of the material of interest is determined to be X-X wide direct band gap semiconductor with an energy of 1.88eV. The hydrogen storage capacity wt (%) and the hydrogen desorption temperature are reported as 5.473 and 625.47K respectively. The Debye temperature ϴD is recorded as 698K using the elastic constants and about 775K using the Gibbs calculations. Under high-pressure effect up to 80GPa, the semiconductor still be an X-X semiconductor with an energy gap of 3.91eV. The Debye temperature ϴD increases monotonically up to about 1120K at 80GPa when using the calculated elastic constants whereas the desorption temperature decreases from 650 to 0K by increasing pressure from 0 to about 87GPa.