Abstract
In this work, first-principles calculations using the density functional theory are performed to study the structure, stability and electronic properties of lithium borohydrides (boranes) and lithium aluminohydrides (alanates). With the attachment of BH4 and AlH4 complexes to the Li atom, the electron affinity increases to 5.22 eV and 4.34 eV, in the clusters Li(BH4)2 and Li(AlH4)2, respectively, which indicate superhalogen behaviour. For the alanates, by decorating the Li atom with the superhalogen moiety, the electron affinity increases to 4.64 eV, in the large-sized cluster Li[Li(AlH4)2]2. The substitution of Al for B leads to larger NBO charges on the H atoms, as a result of the electron- donating character of the Al atom. The results show that, besides larger gravimetrical storage capacities, the boranes also have higher electron affinities than the alanates in the large-sized clusters. The significant HOMO-LUMO differences indicate that the new moieties, which are highly reactive, are chemically very stable species.
Acknowledgements
This research was supported by grants from the Conselho Nacional de Desenvolvimento Cientifico e Tecnológico (CNPq, Brazil).