Theoretical study of aluminum arsenide clusters: Equilibrium geometries and electronic structures of AlnAsn (n = 1-4)

The geometry, electronic configurations, harmonic vibrational frequencies and stability of the structural isomers of AlnAsn clusters (n = 1-4) have been investigated using density functional theory. For dimers and trimers, the lowest energy structures are planar cumulenic rings (IIs, VIs) with Dnh symmetry. The caged structure with Td symmetry (IXs) lie lowest in energy among the tetramers. The AlAs bond dominates the structures for many isomers so that one preferred dissociation channel is loss of the AlAs monomer. The atomic charges, hybridization and chemical bonding in the different structures are also discussed. Comparisons with valence-isoelectronic Si2n, AlnPn and GanAsn clusters of same size, the properties of the aluminum arsenide clusters are analogous to those of their corresponding AlnPn, Si2n counterparts. The results can explain the modification and refinement of Si phase in AlSi alloy in the molecular level.