Density functional theory study on (Mg(BH4))n (n = 1–4) clusters as a material for hydrogen storage

Geometrical structures and relative stabilities of (Mg(BH4)2)n (n = 1–4) clusters were investigated by B3LYP/6-31G** method. For the most stable isomers, the geometrical structures, vibrational spectra and B–H bond dissociation energies (BDEs) were further analyzed. Natural bond orbital (NBO) analysis was also performed. The structural analysis shows the average binding energies of (Mg(BH4)2)n (n = 1–4) clusters are affected drastically by the structures of isomers and c3 structure is very close to the crystal structure. The spectroscopic analysis shows that the stretching vibrations of B–H bond close gradually with the augment of n value. In addition, the B–H bonds for singlet clusters are more stable that those for triplet clusters, which is proved by the analysis of gap energy (Eg) and high occupied orbital energy (EHOMO).