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Title: Communication: Configuration interaction combined with spin-projection for strongly correlated molecular electronic structures

We present single and double particle-hole excitations in the recently revived spin-projected Hartree-Fock. Our motivation is to treat static correlation with spin-projection and recover the residual correlation, mostly dynamic in nature, with simple configuration interaction (CI). To this end, we introduce the Wick theorem for nonorthogonal determinants, which enables an efficient implementation in conjunction with the direct CI scheme. The proposed approach, termed spin-extended CI with singles and doubles, achieves a balanced treatment between dynamic and static correlations. To approximately account for the quadruple excitations, we also modify the well-known Davidson correction. We report that our approaches yield surprisingly accurate potential curves for HF, H{sub 2}O, N{sub 2}, and a hydrogen lattice, compared to traditional single reference wave function methods at the same computational scaling as regular CI.
Authors:
;  [1]
  1. Graduate School of System Informatics, Kobe University, Kobe 657-8501 (Japan)
Publication Date:
OSTI Identifier:
22493609
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 144; Journal Issue: 1; Other Information: (c) 2016 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; COMPARATIVE EVALUATIONS; CONFIGURATION INTERACTION; CORRECTIONS; CORRELATIONS; ELECTRONIC STRUCTURE; EXCITATION; HARTREE-FOCK METHOD; HOLES; HYDROFLUORIC ACID; HYDROGEN; POTENTIALS; SPIN; WATER; WAVE FUNCTIONS; WICK THEOREM