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 01, p, and y have been analyzed in terms of the u and n-molecular orbital contributions, the contribution of the individual n-molecular orbitals, and the contribution of the highest occupied and the lowest unoccupied molecular orbitals. Within the SO0 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.