First-principles study on thermodynamical stability of metal borohydrides: Aluminum borohydride Al(BH4)3

摘要

The thermodynamical stability of ${m Al(BH_4)_3}$ has been investigatedusing first-principles calculations based on density functional theory. Theheats of formation are obtained to be -132 and $-131 {m kJ/mol}$ without thezero-point energy corrections for $lpha$- and $eta$-${m Al(BH_4)_3}$,respectively, which are made up of discrete molecular ${m Al(BH_4)_3}$ units.It is predicted correctly that the $lpha$ phase is more stable than the$eta$ phase. The energy difference between the solid phases and the isolatedmolecule is only about 10 kJ/mol. An analysis of the electronic structure alsosuggests the weak interaction between ${m Al(BH_4)_3}$ molecules in the solidphases. It is confirmed that ${m Al(BH_4)_3}$ obeys the linear relationshipbetween the heat of formation and the Pauling electronegativity of the cation,which has been proposed in our previous study [Nakamori {it et al.}, Phys.Rev. B {f 74}, 045126 (2006)].