Vibrational corrections to linear and nonlinear static electric propertiesof polyatomic molecules at non-optimum reference geometry

We show how vibrational contributions to the static electric properties of polyatomic molecules may be computed with respect to arbitrary reference ge ometries. The derived geometry corrective term that compensates for the eff ect of using a non-optimum geometry, is a simple function of the energy gra dient and first-order nuclear derivative of the electric property, summed o ver the number of normal vibrational modes of the molecule. We illustrate t he possible orders of magnitude of the geometry correction for the major el ectric properties of the water molecule, computed at different levels of el ectronic structure theory: SCF, MP2, CCSD and CCSD(T). (C) 2000 Elsevier Sc ience B.V. All rights reserved.