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

Journal Article · Thu Jan 07 04:00:00 EST 2016 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.4939585· OSTI ID:22493609

Tsuchimochi, Takashi; Ten-no, Seiichiro ^[1]

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1. Graduate School of System Informatics, Kobe University, Kobe 657-8501 (Japan)

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.

• OSTI ID: 22493609
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 1 Vol. 144; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

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