First-principles insights into structural, mechanical, and thermodynamic properties of Be2MgTMH8 (TM = Ni, Cu and Zn) hydrides for hydrogen storage

초록

Efficient hydrogen storage is vital for advancing hydrogen-based energy technologies. Among various approaches, solid-state storage offers promising potential but demands material enhancement. This study employs first-principles calculations using density functional theory within the WIEN2k framework to investigate MgH2-based hydrides modified with beryllium and transition metals (Ni, Cu and Zn). The calculated hydrogen storage capacities reach 7.39 wt%, 7.08 wt%, and 6.97 wt% for Be2MgNiH8, Be2MgCuH8, and Be2MgZnH8, respectively, while the predicted desorption temperatures are 321.41 K, 238.51 K, and 475.39 K. Mechanical stability is confirmed by elastic constants meeting Born criteria, supported by evaluations of bulk and shear moduli, Cauchy pressure, and hardness. Electronic analysis reveals semiconducting behavior in Be2MgZnH8, while charge density mapping provides insights into bonding characteristics. Thermodynamic properties, including heat capacity, entropy, Debye temperature, and Gibbs free energy are comprehensively explored. The findings confirm the effectiveness of beryllium and transition metal co-doping in improving the structural and thermodynamic performance of MgH2-based hydrides.

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