Dispersion coefficients for polarizabilities, and first and second hyperpolarizabilities using full configuration interaction theory

Helena Larsen*, Jeppe Olsen, Christof Hättig
Department of Chemistry, Århus University, DK-8000 Århus C, Denmark

Chem. Phys. Lett. 307, 235-243 (1999).
Received 24 March 1999; in final form 28 April 1999

Dispersion coefficients for frequency-dependent properties can efficiently be calculated from the derivatives of the properties with respect to their frequency arguments. We have derived and implemented analytic expressions for the second-order dispersion coefficients of second-, third-, and fourth-order properties in full configuration interaction (FCI) linear, quadratic, and cubic response theory. The accuracy of the second-order dispersion expansion is investigated for BH and Ne for CCSD and FCI. Padé approximants are found to improve the results. The deviation from the analytic results is in most cases less than that between CCSD and FCI. The sensitivity of the dispersion coefficients to the choice of wave function model and one-electron basis set is investigated and found to be significant.

*Corresponding autho. E-mail: helena@kemi.aau.dk

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