Structure, stability, dipole polarizability and differential polarizability in small gallium arsenide clusters from all-electron ab initio and density-functional-theory calculations

We have employed conventional ab initio and density-functional-theory (DFT) methods to study the structure, stability and electric polarizability of small gallium arsenide clusters Ga_nAs_n. We relied on purpose-oriented, carefully optimized basis sets of Gaussian-type functions. We have calculated both the mean dipole polarizability (α̅ ) and the anisotropy (Δα). Our results show that the differential-per-atom polarizability of the most stable isomers decreases rapidly with cluster size. Compared to the ab initio results, the widely used Becke’s three-parameter exchange DFT functional with the Lee, Yang, and Parr correlation functional and Becke’s three-parameter exchange DFT functional with Perdew and Wang’s 1991 gradient-corrected correlation functional density-functional-theory methods follow clearly the trend of the differential-per-atom polarizability α̅ _diff∕atom for the most stable isomers and predict values closer to the self-consistent field method but distinctly lower than second-order Møller-Plesset perturbation theory. All methods predict a positive value for the dimer, α̅ _diff∕atom (Ga₂As₂)>0.