Comparison of metal additives and Boron atom on MgH2 absorbing-desorbing characteristics using calculated NQCCs

Abstract

Using ab initio calculations, the hydrogen desorption from Magnesium hydride (MgH₂) was studied. We presented the calculated nuclear quadrupole coupling constants (NQCCs) of hydrogen atom in various systems of MgH₂. The effect of interactions of some metal atoms as well as Boron atom with MgH₂ host matrix; (MgH₂+M) nanostructures (M=Al, Ti, V, Fe, Ni and B); were studied and ²H-NQCCs were calculated. From results, introduction of B decreased ²H-NQCC and consequently trend of decrease of charge density in the presence of B was observed. In the other hands introduction of B destabilized initial structure of MgH₂, But in (MgH₂+M) nanostructures(M=Al, Ti, V, Fe and Ni) the ²H- NQCCs were larger than those of pure MgH₂ and consequently more difficult condition for hydrogen desorption were created. However at sufficiently low B concentration (Mg₁₅BH₃₂); the calculation predicted existence of stable dopant system with greater ²H-NQCC.The electric field gradient (EFG) at the site of quadrupolar nuclei were calculated to obtain NQCC parameters at HF/3-21G level of theory.