High-order correlation effects on dynamic hyperpolarizabilities and their geometric derivatives: a comparison with density functional results

Magdalena Pecul1, Filip Pawlowski2, Poul Jørgensen3, Andreas Köhn3, Christof Hättig4
1Department of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warszawa, Poland
2Department of Chemistry, University of Oslo, Box 1033 Blindern, N-0315 Oslo, Norway and
3Department of Chemistry, University of Aarhus, Langelandsgade 140, DK-8000 Aarhus C, Denmark
4Forschungszentrum Karlsruhe, Institute of Nanotechnology, P.O. Box 3640, D-76021 Karlsruhe, Germany

J. Chem. Phys. 124, 114101 (2006).
(Received 14 November 2005; accepted 17 January 2006; published online 15 March 2006)

Second harmonic generation hyperpolarizabilities and their geometric derivatives have been calculated for HF, HCl, CO, and LiF, using the coupled cluster hierarchies, CCS, CC2, CCSD, CC3, and large correlation-consistent basis sets. The full configuration interaction results have been used to test the accuracy of the coupled cluster results. The CCS and CC2 methods do not improve on the Hartree-Fock results while CCSD is robust and gives significant improvements compared to CCS and CC2. The effects of triples in CC3 are in some cases substantial. Higher order correlation effects are significant for LiF. Including core-valence correlation effects is required only if high accuracy is desired. The coupled cluster results have been used as benchmarks for the results obtained by means of density functional theory using various exchange-correlation functionals. For the hyperpolarizability B3LYP was found to perform best, i.e., to give the results closest to the CC3 ones, while for the geometric derivatives none of the considered functionals was able to give a consistent description for all the considered molecules. (c) 2006 American Institute of Physics.

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