Application of explicitly correlated coupled-cluster methods to molecules containing post-3d main group elements |
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Authors: | Kirk A Peterson Christine Krause Hermann Stoll J Grant Hill |
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Institution: | 1. Department of Chemistry , Washington State University , Pullman , Washington 99164-4630 , USA;2. Institut für Theoretische Chemie, Universit?t Stuttgart , Pfaffenwaldring 55, D-70569 Stuttgart , Germany |
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Abstract: | A benchmark of explicitly correlated CCSD(T)-F12 methods for the dimers Ga2, As2, Br2 and diatomic molecules AsN, BrO, HBr, GaF, GaCl, GaBr, AsF, AsCl, BrF, and BrCl is presented. Equilibrium distances, harmonic vibrational frequencies, and dissociation energies are compared with extensive conventional CCSD(T) calculations using a variety of orbital basis sets and different ansätze for the explicitly correlated wavefunctions. Correlation of the 3d electrons has a strong effect, in particular on the equilibrium distances, and it is shown that this can be recovered very efficiently by the explicit correlation treatment. It is found that CCSD(T)-F12 calculations with new F12-specific cc-pVnZ-F12 basis sets give comparable accuracy to standard CCSD(T) calculations with very much larger aug-cc-pwCV(n+2)Z basis sets. The effects of higher order valence electron correlation (up to CCSDTQP) are also investigated in conventional calculations and are found to be significant in some cases. |
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Keywords: | CCSD(T)-F12 explicit correlation core–valence correlation heavy elements |
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