We have studied the static dipole polarizability of stoichiometric gallium phosphide clusters (Ga_nP_n with n=2–5) by employing various ab initio wave function based methods as well as density functional theory/time dependent density functional theory (DFT/TDDFT). The calculation of polarizability within DFT/TDDFT has been carried out by employing different exchange-correlation functionals, ranging from simple local density approximation to an asymptotically correct model
potential-statistical average of orbital potential (SAOP) in order to study their influences. The values obtained by using the model potential-SAOP are lower than those obtained by local density approximation and generalized gradient approximation. A systematic analysis of our results obtained using the DFT/TDDFT with several exchange-correlation functionals shows that the values of polarizability obtained within generalized gradient approximation by using Perdew-Burke- Ernzerhof exchange with Lee–Yang–Parr correlation functional and Perdew– Burke–Ernzerhof exchange-correlation functionals are the closest to the corresponding results from Møller–Plesset perturbation theory. We have found that the value of average static dipole polarizability per atom reaches the bulk limit from the above as the size of the clusters increases.