Basis set limit CCSD(T) harmonic vibrational frequencies

David P. Tew, Wim Klopper*, Miriam Heckert, Juergen Gauss

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

75 Citations (Scopus)

Abstract

Benchmark, frozen-core CCSD(T) equilibrium harmonic vibrational frequencies of 12 closed-shell and five open-shell molecules are computed to within 1 cm(-1) of the basis set limit using the explicitly correlated CCSD(T)-R12 method. The convergence of the standard CCSD(T) method with the one-particle basis sets of Dunning and co-workers is examined and found to be slow, with mean and maximum absolute errors of 1.3 and 3.5 cm(-1) remaining at the cc-pV6Z level. Finite basis set effects do not appear to introduce systematic errors in equilibrium harmonic frequencies, and mean absolute errors reduce by a factor of 2 for each basis set cardinal number increment. The convergence of individual equilibrium harmonic frequencies is not guaranteed to be monotonic due to the associated shift in the equilibrium structure. The inclusion of computed scalar relativistic effects and previously available corrections for core-valence correlation and higher-order excitations in the cluster operator results in an agreement with experimentally derived harmonic frequencies of 0.1, 0.3, and -0.4 cm(-1) for HF, N-2, and CO, respectively. F-2 continues to present a challenge to computational chemistry with error of 3.2 cm(-1), primarily resulting from the high basis set dependence of the quadruples contribution.

Original languageEnglish
Pages (from-to)11242-11248
Number of pages7
JournalJournal of Physical Chemistry A
Volume111
Issue number44
DOIs
Publication statusPublished - 8 Nov 2007

Keywords

  • COUPLED-CLUSTER THEORY
  • CORRELATED MOLECULAR CALCULATIONS
  • GAUSSIAN-BASIS SETS
  • 1ST-ORDER RELATIVISTIC CORRECTIONS
  • CONFIGURATION-INTERACTION MODELS
  • CONNECTED QUADRUPLE EXCITATIONS
  • AB-INITIO THERMOCHEMISTRY
  • COMPUTATIONAL THERMOCHEMISTRY
  • SPECTROSCOPIC CONSTANTS
  • CORRELATION ENERGIES

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