Theoretica chimica acta

, Volume 78, Issue 3, pp 175–187

A comparison of variational and non-variational internally contracted multiconfiguration-reference configuration interaction calculations

  • Hans-Joachim Werner
  • Peter J. Knowles

DOI: 10.1007/BF01112867

Cite this article as:
Werner, HJ. & Knowles, P.J. Theoret. Chim. Acta (1990) 78: 175. doi:10.1007/BF01112867


The internally contracted multiconfiguration-reference configuration interaction (CMRCI) method and several non-variational variants of this method (averaged coupled pair approximation (ACPF), quasidegenerate variational perturbation theory (QD-VPT), linearized coupled pair many electron theory (LCPMET)) have been employed to compute potential energy functions and other properties for a number of diatomic molecules (F2, O2, N2, CN, CO) using large basis sets and full valence CASSCF reference wavefunctions. In most cases the variational CMRCI wavefunctions yield more accurate spectroscopic constants than any of the employed non-variational methods. Several basis sets are compared for the N2 molecule. It is found that atomic natural orbital (ANO) contractions led to significant errors in the computedre, ωe, andDe values.

Key words

Variational Non-variational Configuration interaction Diatomic molecules 

Copyright information

© Springer-Verlag 1990

Authors and Affiliations

  • Hans-Joachim Werner
    • 1
  • Peter J. Knowles
    • 2
  1. 1.Fakultät für ChemieUniversität BielefeldBielefeldFederal Republic of Germany
  2. 2.School of Chemistry and Molecular SciencesUniversity of SussexFalmer, BrightonUK

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