Phase transitions, elastic and electronic properties of hydrogen storage Na2PdH4

Abstract

Hydrogen can be absorbed by some materials at specific pressures and temperatures. This is extremely important in terms of creating carbon-free and sustainable society. In this work hydrides are good candidates to fulfill these aims. Electronic and magnetic properties of hydrides are investigated. This study considers Na2PdH4 as solid storage of hydrogen material. Hydrogen is highly soluble in palladium and can be stored in large amounts at ambient conditions. The structural evolution, electronic and elastic properties of Na2PdH4 has been investigated by means of density functional theory. The SIESTA software package is used with the generalized gradient approximation for the exchange-correlation functional and norm-conserving Troullier-Martins pseudopotentials. High-pressure computations have been carried out to reveal phase transitions. Na2PdH4 is transformed from I4/mmm tetragonal structure to Immm orthorhombic structure at 100 GPa. The electronic band structures and density of states are obtained for both phases. Mechanical stability is analyzed using the elastic constants. Moreover, several parameters such as Young's modulus, shear modulus, and their ratios are obtained and discussed. © 2021 Author(s).