(Hyper)polarizabilities of GaN, GaP, and GaAs Clusters: An Ab Initio Time-Dependent Hartree−Fock Study

Abstract

The (hyper)polarizabilities of GaN, GaP, and GaAs clusters have been calculated using an ab initio time-dependent Hartree−Fock method and an even-tempered Gaussian basis set. The geometries of the clusters used in the study were optimized by ab initio Hartree−Fock calculations using the same basis set. The clusters used in this calculation are of the type GamXn (m = 1, 3, 4 and n = 1, 3, 4) where X = N, P, or As. The GamXn clusters are in a charge neutral (q = 0) state for m = n and in an appropriately charged state for m ≠ n. All of the clusters studied are stable in a nearly tetrahedral geometry. The magnitude of the calculated (hyper)polarizabilities appears to depend on the size of the cluster. The cluster-size dependence of calculated (hyper)polarizabilities is more pronounced for the first hyperpolarizability, β, than for the polarizability, α. The calculated frequency-dependent polarizability, α(ω), exhibits a small but finite dispersion with the frequency of the optical field. The magnitude of the...