Nuclear relaxation and vibrational contributions to the static electrical properties of polyatomic molecules: beyond the Hartree-Fock approximation

Abstract

Electronic and nuclear contributions to the static molecular electrical properties, along with the Stark tuning rate ( δ νE ) and the infrared cross section changes ( δ SE) have been calculated at the SCF level and at different correlated levels of theory, using a TZ2P basis set and finite field techniques. Nuclear contributions to these molecular properties have also been calculated using a recent analytical approach that allow both to check the accuracy of the finite field values, and to evaluate the importance of higher-order derivatives. The HF, CO, H 2O, H 2CO, and CH 4 molecules have been studied and the results compared to experimental date when available. The paper shows that nuclear relaxation and vibrational contributions must be included in order to obtain accurate values of the static electrical properties. Two different, combined approaches are proposed to predict experimental values of the electrical properties to an error smaller than 5%.