ELECTRIC-DIPOLE HYPERPOLARIZABILITY AND QUADRUPOLE POLARIZABILITY OF METHANE FROM FINITE-FIELD COUPLED-CLUSTER AND 4TH-ORDER MANY-BODY PERTURBATION-THEORY CALCULATIONS

We rely on a finite-field approach to calculate the static dipole (alpha) and quadrupole (C) polarizability and the first (beta) and second (gamma) dipole hyperpolarizability of methane. Our best, CCSD(T) values for alpha,beta and the mean value of gamma and C, obtained at R(e)=2.052 a0 with a (11s7p4d2f/6s2p1d) [6s4p4d2f/4s2p1d] basis set, are alpha=16.39 e2 a0(2) E(h)-1, beta=-8.31 e3 a0(3) E(h)-2, gammaBAR=2312 e4 a0(4) E(h)-3 and CBAR=60.45 e2 a0(4) E(h)-1. The derivatives of alpha, beta and gamma (symmetric stretch) at R(e) were calculated at the SDQ-MP4 level of theory with a (11s7p4d1f/6s2p1d)[6s4p4d1f/4s2p1d] basis set: (dalpha/dR)e=15.7 e2 a0 E(h)-1, (dbeta/dR)e=-25.3 e3 a0(2)E(h)-2 and (dgammaBAR/dR)e=37.4 x 10(2) e4 a0(3)E(h)-3.