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 ${\mathrm{Ga}}_n{\mathrm{As}}_n$. We relied on purpose-oriented, carefully optimized basis sets of Gaussian-type functions. We have calculated both the mean dipole polarizability $\left(\overline{\alpha }\right)$ and the anisotropy $\left(\mathrm{\Delta }\alpha \right)$. 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 ${\overline{\alpha }}_{\mathrm{diff}}∕\mathrm{atom}$ 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, ${\overline{\alpha }}_{\mathrm{diff}}∕\mathrm{atom}$ $\left({\mathrm{Ga}}_2{\mathrm{As}}_2\right)>0$.

• Received 31 October 2007

DOI:https://doi.org/10.1103/PhysRevA.77.013201