A prospective DFT study for assembling highly reactive clusters based on lithium boranes and alanates

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.

Keywords:

• density functional theory
• clusters
• electron affinity
• halogens
• superhalogens

Acknowledgements

This research was supported by grants from the Conselho Nacional de Desenvolvimento Cientifico e Tecnológico (CNPq, Brazil).