UNCOUPLED HARTREE-FOCK CALCULATIONS OF THE POLARIZABILITY AND HYPERPOLARIZABILITIES OF NITROPHENOLS

The polarizability and hyperpolarizabilities of nitrophenols as model compounds for studying nonlinear optics have been investigated at the Hartree-Fock level of approximation by means of the Dalgarno Uncoupled Hartree-Fock (DUHF) or Sum Over Orbitals (SOO) method. The additive character and the charge transfer effects in alpha, beta, and gamma have been analyzed in terms of the sigma and pi molecular orbital contributions, the contribution of the individual pi molecular orbitals, and the contribution of the highest occupied and the lowest unoccupied molecular orbitals. Within the SOO approach, the reliability of the Two-Level Model has been tested and the influence of the rotation of the nitro group and of the presence of the intramolecular hydrogen bonding in ortho-nitrophenol have been studied. The results show that the present method is a reliable and efficient tool for the prediction of trends in the molecular polarizability and hyperpolarizabilities of large molecules. (C) 1995 by John Wiley and Sons, Inc.