DFT study of structural, electronic, optical, thermodynamic and hydrogen storage properties of Be2XH6 (X = Co, Ni, Cu)

First principles calculations are performed to explore structural, electronic, optical, thermodynamical and hydrogen storage properties of Be₂XH₆ (X = Co, Ni, Cu) double hydride perovskites. The lattice constants of Be₂CoH₆, Be₂NiH₆ and Be₂CuH₆ are optimized from energy volume curve and noted 5.90 (Å), 5.98 (Å) and 6.14 (Å) respectively. The phonon dispersion curve confirms the dynamic stability of under study double perovskites except Be₂CuH₆. The stability is further tested at higher finite temperatures via ab-initio molecular dynamic calculations. The energy band structure shows the existence of no energy difference between valance and conduction band which reflects the metallic nature of double hydride perovskites. The highest static dielectric constant noted for ${\mathrm{Be}}_2{\mathrm{NiH}}_6$. The under pressure thermodynamic properties reflect that the Debye temperature is reduced with increasing the applied temperature. However, an increase in entropy and specific heat capacities can be noted with the increase of applied temperature. The gravimetric hydrogen storage capacity $C_{\omega t}\text{\%}$ of ${\mathrm{Be}}_2{\mathrm{CoH}}_6$, ${\mathrm{Be}}_2{\mathrm{NiH}}_6$ and ${\mathrm{Be}}_2{\mathrm{CuH}}_6$ are 6.80%, 6.82% and 6.47% respectively. High stability and large value of gravimetric hydrogen storage capacity makes these materials prominent for utilization in hydrogen storage applications.