Cluster-assembled materials based on M12N12 (M = Al, Ga) fullerene-like clusters

Abstract

We report the results of density functional theory calculations on cluster-assembled materials based on M₁₂N₁₂ (M = Al, Ga) fullerene-like clusters. Our results show that the M₁₂N₁₂ fullerene-like structure with six isolated four-membered rings (4NRs) and eight six-membered rings (6NRs) has a T_h symmetry and a large HOMO–LUMO gap, indicating that the M₁₂N₁₂ cluster would be ideal building blocks for the synthesis of cluster-assembled materials. Via the coalescence of M₁₂N₁₂ building blocks, we find that the M₁₂N₁₂ clusters can bind into stable assemblies by either 6NR or 4NR face coalescence, which enables the construction of rhombohedral or cubic nanoporous framework of varying porosity. The rhombohedral-MN phase is energetically more favorable than the cubic-MN phase. The M₁₂N₁₂ fullerene-like structures in both phases are maintained and the M-N bond lengths between M₁₂N₁₂ monomers are slightly larger than that in isolated M₁₂N₁₂ clusters and the bulk wurtzite phases. The band analysis of both phases reveals that they are all wide-gap semiconductors. Because of the nanoporous character of these phases, they could be used for gas storage, heterogeneous catalysis, filtration and so on.