Theoretical study of small Al-Ga-N ternary clusters

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 AlxGayNz (x,y,z = 1-3) clusters. The lowest-energy structures of different-sized AlxGayNz clusters are given based on the extensive search of the local minima of the potential energy surface. The results indicate that the AlxGayNz clusters prefer planar structures except AlGaN4. The lowest-lying structures of the clusters keep the analogous framework as small GamNn clusters by replacing Ga atom(s) with Al. The strong Al-N bond is a dominant factor in the building-up principle of each AlxGayNz clusters. The calculated dissociation energies of the AlxGayNz (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 AlGaN3. 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.