Molecules in static electric fields: Linear and nonlinear polarizability of [Formula Presented] and [Formula Presented]

Abstract

Accurate linear and nonlinear polarizabilities were obtained from finite-field self-consistent field, fourth-order many-body perturbation theory and coupled-cluster calculations for the triply bonded linear molecules [Formula Presented] and [Formula Presented] The mean dipole polarizability and the anisotropy of HCN at the CCSD(T) level of theory is [Formula Presented] and [Formula Presented] For HCP the respective values are 35.47 and 16.24 [Formula Presented] Electron correlation reduces significantly the magnitude of the first dipole hyperpolarizability [Formula Presented] of both molecules. The CCSD(T) values of the mean [Formula Presented] are [self-consistent-field (SCF) values in parentheses] [Formula Presented] [Formula Presented] for HCN and 28.5 (36.7) [Formula Presented] for HCP. Electron correlation modifies mainly the longitudinal component of the second hyperpolarizability tensor [Formula Presented] for both HCN and HCP. The CCSD(T) mean value for HCN is [Formula Presented] 17.4% higher than the SCF value of [Formula Presented] For HCP [Formula Presented] at the CCSD(T) level, only 2.2% above the SCF result of [Formula Presented] For the quadrupole polarizability, fourth-order many-body perturbation theory yields [Formula Presented] [Formula Presented] [Formula Presented] [Formula Presented] for HCN, and [Formula Presented] [Formula Presented] [Formula Presented] [Formula Presented] for HCP, with [Formula Presented] as the molecular axis. © 1998 The American Physical Society.