Density functional analysis of structural, mechanical, electronic, and hydrogen storage properties of thermodynamically stable lead-free hydrides [formula omitted](X = Cs, Fr): A perspective of clean energy and fuel

Abstract

A density functional theory based calculations are performed to investigate structural, hydrogen storage, mechanical, electronic and thermodynamical properties of lead-free hydride perovskites XGeH3 (X=Cs, Fr). The optimized lattice constant and hence volume against the minimum energy is obtained and found to be 4.176 Å and 4.184 Å for CsGeH3 and FrGeH3 respectively. The gravimetric and volumetric hydrogen storage capacity of 1.43% and 1.00%, 72.81(g.H2/L) and 73.21(g.H2/L) for CsGeH3 and FrGeH3 respectively. The density of states and electronic band structure predicted the metallic nature of both hydrides which was affirmed by the Fermi Surfaces. The calculation of Poisson’s, Pugh’s ratio and Cauchy’s pressure suggested their brittle nature. The Debye temperature decreases with the increase of temperature while volume and entropy increase by increasing applied temperature. The present study shows the potential of lead-free hydride perovskites in hydrogen storage applications due to rather suitable gravimetric hydrogen capacity and high stability.