Study of Structural and Electronic Behavior of BeH2 as Hydrogen Storage Compound: An Ab Initio Approach

The quantum mechanical calculations based on density functional theory (DFT) have been performed to study ground state structural and electronic properties of BeH2 and along with doping of two (BeH2 + 2H) and four (BeH2 + 4H) hydrogen atoms. The generalized gradient approximation (GGA) has been employed for the exchange correlation energy. The most stable space group of BeH2 is Ibam. Its optimized equilibrium unit cell volume, bulk modulus and its first-order pressure derivative, and electronic properties have been obtained. Our predicted unit cell parameters for BeH2？？ ？？, ？？, and ？？ are in very good agreement with the earlier reported experimental and theoretical results. The electronic band structure of BeH2 shows its behavior as an insulator. The stability of BeH2 along with doped hydrogen atoms increases, while the energy band gap decreases with the increase in number of doped hydrogen atoms. On these bases, we predict that BeH2 is a promising material for hydrogen storage. 1. Introduction Energy storage for the future is a great concern for the researchers and scientists. We need materials like metal hydrides for various potential applications, that is, for hydrogen storage, in fuel cells and internal combustion engines, as electrodes for rechargeable batteries, and in energy conversion devices. The metal hydrides for hydrogen storage need to be able to form hydrides with a high hydrogen-to-metal mass ratio, but they should not be too stable, so that the hydrogen can easily be released without excessive heating. Beryllium and magnesium and beryllium-magnesium-based hydrides contain a relatively high fraction of hydrogen by weight but need to be heated ~250 to 300°C in order to release the hydrogen. The alkali-metal and alkaline-earth-metal hydrides represent series with largely ionic bonding. The high pressure behavior of the alkali-metal monohydrides is expected to parallel of the alkali-metal halides [1]. However, there is no systematic high-pressure study on the alkaline-earth-metal hydrides. If becomes metallic when subjected to high pressures, one can entertain the possibility that its properties could resemble those of metallic hydrogen. is commonly considered as a covalent hydride with a postulated polymeric crystal structure made up of H-bridged chains. However, mainly owing to experimental difficulties in the synthesis of the material, the structure has long remained unknown [2]. Crystalline has been synthesized and the structure has been established as body centered orthorhombic by synchrotron-radiation-based powder X-ray diffraction