Interaction electric hyperpolarizability effects in weakly bound H(2)O...Rg (Rg = He, Ne, Ar, Kr and Xe) complexes

We report an extensive high-level ab initio theoretical investigation of the interaction electric properties of the weakly bound complexes of water with rare gases, H(2)O...Rg (Rg = He, Ne, Ar, Kr and Xe). Our approach relies on finite-field many-body perturbation theory (MP) and coupled-cluster (CC) calculations with flexible, carefully designed basis sets of Gaussian-type functions (GTFs). We have obtained estimates of the electron correlation effects on the reference self-consistent field (SCF) values at all levels of theory employed in this work. For the planar equilibrium configuration (C(s) symmetry) of the complexes, at the CCSD(T) level of theory, the interaction mean first hyperpolarizability is positive (SCF values in parentheses): beta(int)/e(3)a(0)(3)E(h)(-2)(H(2)O-Rg) = 0.72 (0.56), 1.20 (0.79), 7.04 (4.28), 9.88 (5.34), and 15.52 (6.68) for Rg = He, Ne, Ar, Kr, and Xe, respectively. For the interaction mean second hyperpolarizability, we have obtained (SCF values in parentheses): gamma(int)/e(4)a(0)(4)E(h)(-3)(H(2)O-Rg) = -18.93 (-14.19), -37.78 (-24.35), -83.16 (-72.42), -102.92 (-125.70), and -206.45 (-286.83) for Rg = He, Ne, Ar, Kr, and Xe. In addition to the equilibrium values of the interaction electric properties, we have also extracted information for their dependence on the variation of the distance of the rare gas atom from the center of mass of the water molecule (without changing direction). The gradient of the interaction mean second hyperpolarizability at the equilibrium configuration is determined as (dgamma(int)/dR)(e)/e(4)a(0)(3)E(h)(-3)(H(2)O-Rg) = 9.89 (He), 25.42 (Ne), 73.71 (Ar), 144.71 (Kr), and 324.68 (Xe).