Coupled‐perturbed Hartree–Fock theory for quasi–one‐dimensional periodic systems: Calculation of static and dynamic nonlinear optical properties of model systems

Abstract

AbstractAn alternative method to solve the coupled‐perturbed Hartree–Fock (CPHF) equations for infinite quasi–one‐dimensional systems is presented. The new procedure follows a proposal made by Langhoff, Epstein, and Karplus to obtain perturbed wavefunctions free from arbitrary phase factors in each order of perturbation. It is based on the intermediate orthonormalization of the perturbed wavefunctions (which is different from the usual one) and a corresponding selection of the Lagrangian multipliers. In this way it is possible to incorporate the orthonormalization conditions into the set of CPHF equations. Moreover, a new, advantageous procedure to determine the derivatives of the wavefunction with respect to the quasimomentum k is presented. We report calculations of the dipole moment, the polarizability α, and the first hyperpolarizability β for different polymers (poly‐HF, poly‐H2O, trans‐polyacetylene, polyyne, and polycarbonitrile) for different frequencies. These results are extensively compared with oligomer calculations. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 94: 251–268, 2003