TIME-DEPENDENT HARTREE-FOCK 2ND-ORDER MOLECULAR-PROPERTIES WITH A MODERATELY SIZED BASIS SET .2. DISPERSION COEFFICIENTS

Time-dependent coupled Hartree-Fock frequency-dependent polarizabilities are used to obtain ab initio dipole-dipole C6, dipole-quadrupole C8, and triple-dipole nu, dispersion coefficients. The moderately sized 6-31G (+ sd + sp) basis set optimized for calculation of molecular static dipole polarizabilities has enabled the computation of dispersion coefficients for a wide variety of molecules containing atoms up to chlorine. Results are presented for 48 molecules including benzene, cyclohexane, SF6, and CCl4. Appropriate scaling of 6-31G (+ sd + sp) results for C6 and nu enables the prediction of these coefficients to within 3% of experimental estimates that are based on dipole oscillator strength distributions. Results for the mean static quadrupole polarizability CBAR(0) and C8 dispersion coefficient are presented for nondipolar molecules and the origin dependence of C8 is investigated.