Phase transition and optoelectronic properties of MgH2

In this article, structural and electronic properties of MgH₂ have been studied. The aim behind this study was to find out the ground state crystal structure of MgH₂. For the purpose, density functional theory (DFT)-based full-potential linearized augmented plane wave (FP-LAPW) calculations have been performed in three different space groups: P4₂/mnm (α-MgH₂), Pa3 (β-MgH₂) and Pbcn (γ-MgH₂). It has been found that the ground state structure of MgH₂ is α-MgH₂. The present study shows that α-MgH₂ transforms into γ-MgH₂ at a pressure of 0.41 GPa. After further increase in pressure, γ-MgH₂ transforms into β-MgH₂ at a pressure of 3.67 GPa. The obtained results are in good agreement with previously reported experimental data. In all the studied phases, the behavior of MgH₂ is insulating and its optical conductivity is around 6.0 eV. The α-MgH₂ and γ-MgH₂ are anisotropic materials while β-MgH₂ is isotropic in nature.