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Title: Density cumulant functional theory from a unitary transformation: N-representability, three-particle correlation effects, and application to O{sub 4}{sup +}

A new approach to density cumulant functional theory is developed that derives density cumulant N-representability conditions from an approximate Fock space unitary transformation. We present explicit equations for the third- and fourth-order two-particle cumulant N-representability, as well as the second-order contributions that depend on the connected three-particle density cumulant. These conditions are used to formulate the ODC-13 method and the non-iterative (λ{sub 3}) correction that employ an incomplete description of the fourth-order two-particle cumulant N-representability and the second-order three-particle correlation effects, respectively. We perform an analysis of the ODC-13 N-representability description for the dissociation of H{sub 2} and apply the ODC-13 method and the (λ{sub 3}) correction to diatomic molecules with multiple bond character and the symmetry-breaking tetraoxygen cation (O{sub 4}{sup +}). For the O{sub 4}{sup +} molecule, the vibrational frequencies of the ODC-13(λ{sub 3}) method do not exhibit spatial symmetry breaking and are in a good agreement with the recent infrared photodissociation experiment. We report the O{sub 4}{sup +} equilibrium structure, harmonic frequencies, and dissociation energy computed using ODC-13(λ{sub 3}) with a diffuse, core-correlated aug-cc-pCVTZ basis set.
Authors:
;  [1] ;  [2]
  1. Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia 30602 (United States)
  2. Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, D-44780 Bochum (Germany)
Publication Date:
OSTI Identifier:
22419793
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 141; Journal Issue: 7; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; APPROXIMATIONS; CATIONS; CORRELATIONS; DENSITY; DISSOCIATION; DISSOCIATION ENERGY; HYDROGEN; ITERATIVE METHODS; MOLECULES; PARTICLES; PHOTOLYSIS; TRANSFORMATIONS