A semiempirical approach to nonlinear optical properties of large molecules at the MNDO and MNDO/d level

The analytical evaluation of polarizabilities (alpha) and hyperpolarizabilities (beta, gamma) has been implemented for semiempirical wavefunctions using the coupled Hartree-Fock technique. For molecules with second-row and heavier atoms, the results from MNDO/d are superior to those from MNDO. The basis set at hydrogen has been extended to include 2p functions, and the corresponding additional parameters have been optimized with respect to experimental polarizabilities and hyperpolarizabilities. The resulting specialized MNDO and MNDO/d treatments provide reasonable values for alpha and reproduce trends in gamma, but are not useful for beta. Perspectives for future work are outlined.