Theoretical study of small Al–Ga–N ternary clusters

Abstract

Density-functional theory with generalized gradient approximation for the exchange–correlation potential has been used to calculate the geometric structures, stabilities, and electronic properties of Al x Ga y N z ( x, y, z = 1–3) clusters. The lowest-energy structures of different-sized Al x Ga y N z clusters are given based on the extensive search of the local minima of the potential energy surface. The results indicate that the Al x Ga y N z clusters prefer planar structures except AlGaN 4. The lowest-lying structures of the clusters keep the analogous framework as small Ga m N n clusters by replacing Ga atom(s) with Al. The strong Al–N bond is a dominant factor in the building-up principle of each Al x Ga y N z clusters. The calculated dissociation energies of the Al x Ga y N z ( x, y, z = 1–3) clusters manifest that all of the clusters are stable with respect to dissociation into smaller clusters or atoms except for AlGaN 3. On the basis of the lowest-energy geometries obtained, the electronic properties of the clusters such as HOMO–LUMO gap, Mulliken charge, ionization potential and electron affinity, etc., have been computed and analyzed.