Theoretical Study On Calcium Borohydride Cluster And M?GaH₄?₂?M=Be,Mg,Ca? Complex

Calcium borohydride is investigated widely as a hydrogen storage material.However,investigations on calcium borohydride from a cluster perspective are seldom found.The geometric structures and binding energies of [Ca?BH₄?₂]_n?n=1-4?clusters are determined using density function theory?DFT?.For the most stable structures,vibration frequency,natural bond orbital?NBO?are calculated and discussed.The charges transfer from?BH₄?to Ca.Meanwhile,we also study their LUMO-HOMO gap?Eg?and the B-H bond dissociation energies?BDEs?.[Ca?BH₄?₂]3owns higher Eg,revealing that trimer is more stable than the others.Structures don't change during optimization when remove a hydrogen radical showing possibility that Calcium borohydride could be used as a reversible hydrogen storage material.[Ca?BH₄?₂]4has the smallest dissociation energy suggesting it releases hydrogen more easily than others.First-principles calculations were done examine the substitution effect to hydrogen releasing in Be?GaH₄?₂,Mg?GaH₄?₂and Ca?GaH₄?₂.Using density functional theory?DFT?,we have systematically calculated the equilibrium geometries,nature bond orbital?NBO?analysis,bond dissociation energies.Calculationresults showed that substation by by F,Cl,Br and NH₂ motivate H releasing in Be?GaH₄?₂and Mg?GaH₄?₂.Br substitution makes the corresponding structure more stable.N-H dissociation energy is higher than that of Ga-H.Boron hydride and aluminium hydride and gallium hydride compounds due to its good hydrogen storage property,have attracted many people's attention and research.The article mainly calculated and analyzed the M?GaH4?₂?M=Be,Mg,Ca?geometric structure,the vibration properties,the charge analysis and Ga-H dissociation.At the same time,M?GaH4?₂?M = Be,Mg,Ca?structures after doping Ti are optimized and the corresponding electronic properties are also analysed,finding that the incorporation of Ti atom,makes Ga-H in these compounds weaker.Hence bond dissociation energies?BDEs?decrease,which means that the release of hydrogen become more easily.From a theoretical point of view that coping in these compounds can promote the release of hydrogen.Natural Bond Orbital?NBO?analysis showed that the positive charge is concentrated on the Be,Mg,Ca,and Ga atom,all negative charge distribution on the H atoms.This suggests that The charges transfer from H to to Mg,Ca,and Ga.Ater doping of the Ti atom,Ti is generally positive.However,When H and Ti bond forming tetrahedral configuration,Ti is negative.