The polarizabilities of small stoichiometric aluminum phosphide clusters AlnPn (n = 2–9). Ab initio and density functional investigation

The mean dipole polarizabilities and the polarizability anisotropies of stoichiometric AlnPn (n = 2–9) clusters are investigated and presented for the first time. Basis set augmentation effects on the 6-31+G substrate are studied and discussed. The electron correlation contributions to the polarizability were studied for clusters up to 12 atoms at MP2 and CCSD(T) levels of theory, and the performance of the widely used B3LYP, B3PW91, mPW1PW91 functionals are assessed. From the methodological standpoint, our results show that for clusters where the ionic contribution to the bonding is strong the MP2 method yields polarizability values in very good agreement with the more accurate CCSD(T) approximation.