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 Be 2 XH 6 (X = Co, Ni, Cu) double hydride perovskites. The lattice constants of Be 2 CoH 6 , Be 2 NiH 6 and Be 2 CuH 6 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 Be 2 CuH 6 . 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 Be 2 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 ω t % of Be 2 CoH 6 , Be 2 NiH 6 and Be 2 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. • Hydrogen storage capacity of Be 2 XH 6 (X = Co, Ni, Cu) have been examined. • Highest value of gravimetric hydrogen storage of 6.82 % recorded for Be 2 NiH 6 . • The metallic nature of all transition metal hydrides is noted. • Phonon dispersion curve verify the dynamic stability.