Comprehensive Insights into the hydrogen storage, mechanical, structural, thermodynamics, electronic and optical attributes of (Li/Na/K)PH 6 for renewable energies

Abstract

The increasing interest in perovskite hydrides is attributed to their promise as efficient high-capacity hydrogen storage materials. This study present a detailed investigation of the physical characteristics of XPH 6 (X = Li, Na, and K) is performed utilizing the FP-LAPW method inside the framework of the Wien2K code. The structural and thermodynamic stability is evaluated using several factors. The GGA potential is used to evaluate the hydrides' structural and mechanical characteristics, whereas the mBJ is used to investigate the electrical and optical properties of XPH 6 (X = Li, Na, K). The Young's modulus is computed from the three independent elastic constants reveal a declining trend as the atomic sizes of the hydrides elevate.Furthermore, the brittle nature of these hydrides is confirmed via Pugh's ratio, Cauchy's pressure, and Poisson's ratio. The electronic study indicates indirect bandgaps of 4.66 eV, 5.54 eV, and 6.55 eV for LiPH 6 , NaPH 6 , and KPH 6 , respectively, demonstrating that these hydrides have wide bandgaps. The elastic anisotropy is measured via ELATE software for XPH 6 (X = Li, Na, K). An in-depth examination of the optical characteristics indicated that these perovskite hydrides have significant UV absorption, indicating their potential use in optoelectronic devices. Furthermore, their hydrogen storage capabilities for LiPH 6 , NaPH 6 , and KPH 6 are calculated as 12.01 wt% (50.22 gH 2 /L), 9.08 wt% (47.89 gH 2 /L), and 7.31 wt% (43.96 gH 2 /L) for LiPH 6 , NaPH 6 , and KPH 6 , respectively, making them appropriate for hydrogen storage purposes.