Structural, vibrational, mechanical, and optoelectronic properties of LiBH4 for hydrogen storage and optoelectronic devices: First‐principles study

Abstract

AbstractIn order to cope with the energy crisis and global warming issues, researchers are rendering their efforts and paying attention to analyzing and fabricating hydrogen storage devices. That is why comprehensive investigations are made to unfold the structural, vibrational, mechanical, and optoelectronic properties of lithium borohydride (LiBH4), a hydrogen storage material. For this purpose, calculations of the structural properties were performed using local, nonlocal, and hybrid functionals within the framework of density functional theory. For the determination of lattice constants in the orthorhombic phase, local density approximation (LDA), Perdew‐Burke‐Ernzerhof (PBE), and Heyd‐Scuseria‐Ernzerhof (HSE06) density functionals were chosen, and their results were compared with available experimental and theoretical studies. In order to determine infrared (IR) and Raman active modes of vibrations, vibrational spectroscopy was utilized through density functional perturbation theory. Li, B, and H atoms are noted to contribute in different modes of vibrations among various ranges of frequencies, that is, 0 to 400 cm−1, 1100 to 1300 cm−1, and 2250 to 2400 cm−1. Values of the energy band gap are found to be 6.35, 6.81, and 7.58 eV for LDA, PBE, and HSE06 functionals, respectively, indicating the insulating nature of LiBH4. Such fascinating properties make these compounds promising candidates for future applications in optoelectronic devices. Mechanical analysis revealed that LiBH4 is a brittle and stiffer material. Other optical properties, such as dielectric constant, refractive index, reflectivity, absorptivity, conductivity, and loss function, were also calculated with the assistance of the well‐recognized Kramer‐Kronig relation. The energy loss function depicted a plasma frequency of 13.7 eV, noted from the highest loss peak. It can be concluded that this material is not only suitable for hydrogen storage but also for optoelectronic devices.