First-principles calculations to investigate structural, electronic, elastic, and optical properties of orthorhombic LiBH2 for hydrogen storage and optoelectronic devices

Abstract

In the current investigation, we have implemented first-principles calculations to examine the structural, elastic, electrical, and optical characteristics of LiBH₂. All of the calculations were performed using first-principles density functional theory (DFT). The space group Pnma (62) has been used. The obtained results regarding the lattice parameters of the material of interest are found to be within 2% slighter than those of the experiment. The dispersion curve shows that LiBH₂ is a semiconductor with an indirect band gap of 0.978 eV along the Y–Γ direction. The optical parameters like dielectric function ε(ω), reflectivity R(ω), index of refraction n(ω), coefficients of extinction k(ω), and absorption α(ω) are determined and explained. In this regard, LiBH₂ has shown promise on hydrogen storage applications in account of its high hydrogen volume density of 94.85 g/L (more than that of liquid hydrogen), and a gravimetric hydrogen density of 10.12 wt.%, fulfilling the standard set by US-DOE for 2025.