CI effects on one-electron properties: the case of the electric quadrupole moment of OCS

Abstract

One-electron properties of the OCS molecule have been obtained from SCF and CI wavefunctions using extended Gaussian basis sets. While most properties are in good agreement with experiment, the electric quadrupole moment is an exception. The effect of additional diffuse s-, p- and d-type functions is examined. By an appropriate choice of d exponents it has been possible to obtain improved agreement with experiment for the quadrupole moment at the CI level. In particular, for the quadrupole moment of OCS: theta SCF=-5.27*10-40 Cm2 theta CI=-3.58*10-40 Cm2 as compared with theta EXP=(-2.93+or-0.50)*10-40 Cm2 experimentally.