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The influence of orbital rotation on the energy of closed-shell wavefunctions

(2014) MOLECULAR PHYSICS. 112(5-6). p.853-862
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Abstract
The orbital dependence of closed-shell wavefunction energies is investigated by performing doubly-occupied configuration interaction (DOCI) calculations, representing the most general class of these wavefunctions. Different local minima are examined for planar hydrogen clusters containing two, four, and six electrons applying (spin) symmetry-broken restricted, unrestricted, and generalised orbitals with real and complex coefficients. Contrary to Hartree-Fock (HF), restricted DOCI is found to properly break bonds and thus unrestricted orbitals, while providing a quantitative improvement of the energy, are not needed to enforce a qualitatively correct bond dissociation. For the beryllium atom and the BH diatomic, the lowest possible HF energy requests symmetry-broken generalised orbitals, whereas accurate results for DOCI can be obtained within a restricted formalism. Complex orbital coefficients are shown to increase the accuracy of HF and DOCI results in certain cases. The computationally inexpensive AP1roG geminal wavefunction is proven to agree very well with all DOCI results of this study.
Keywords
MODEL, static electron correlation, closed-shell wavefunction, doubly-occupied configuration interaction, orbital optimisation, MOLECULES, MATRIX, NONORTHOGONAL GEMINALS, SYSTEMS, MCSCF METHODS, BERYLLIUM ATOM, EQUATIONS, EXCITED-STATES

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Chicago
Limacher, Peter A, Taewon D Kim, Paul W Ayers, Paul Johnson, Stijn De Baerdemacker, Dimitri Van Neck, and Patrick Bultinck. 2014. “The Influence of Orbital Rotation on the Energy of Closed-shell Wavefunctions.” Molecular Physics 112 (5-6): 853–862.
APA
Limacher, P. A., Kim, T. D., Ayers, P. W., Johnson, P., De Baerdemacker, S., Van Neck, D., & Bultinck, P. (2014). The influence of orbital rotation on the energy of closed-shell wavefunctions. MOLECULAR PHYSICS, 112(5-6), 853–862.
Vancouver
1.
Limacher PA, Kim TD, Ayers PW, Johnson P, De Baerdemacker S, Van Neck D, et al. The influence of orbital rotation on the energy of closed-shell wavefunctions. MOLECULAR PHYSICS. 2014;112(5-6):853–62.
MLA
Limacher, Peter A, Taewon D Kim, Paul W Ayers, et al. “The Influence of Orbital Rotation on the Energy of Closed-shell Wavefunctions.” MOLECULAR PHYSICS 112.5-6 (2014): 853–862. Print.
@article{4397928,
  abstract     = {The orbital dependence of closed-shell wavefunction energies is investigated by performing doubly-occupied configuration interaction (DOCI) calculations, representing the most general class of these wavefunctions. Different local minima are examined for planar hydrogen clusters containing two, four, and six electrons applying (spin) symmetry-broken restricted, unrestricted, and generalised orbitals with real and complex coefficients. Contrary to Hartree-Fock (HF), restricted DOCI is found to properly break bonds and thus unrestricted orbitals, while providing a quantitative improvement of the energy, are not needed to enforce a qualitatively correct bond dissociation. For the beryllium atom and the BH diatomic, the lowest possible HF energy requests symmetry-broken generalised orbitals, whereas accurate results for DOCI can be obtained within a restricted formalism. Complex orbital coefficients are shown to increase the accuracy of HF and DOCI results in certain cases. The computationally inexpensive AP1roG geminal wavefunction is proven to agree very well with all DOCI results of this study.},
  author       = {Limacher, Peter A and Kim, Taewon D and Ayers, Paul W and Johnson, Paul and De Baerdemacker, Stijn and Van Neck, Dimitri and Bultinck, Patrick},
  issn         = {0026-8976},
  journal      = {MOLECULAR PHYSICS},
  keyword      = {MODEL,static electron correlation,closed-shell wavefunction,doubly-occupied configuration interaction,orbital optimisation,MOLECULES,MATRIX,NONORTHOGONAL GEMINALS,SYSTEMS,MCSCF METHODS,BERYLLIUM ATOM,EQUATIONS,EXCITED-STATES},
  language     = {eng},
  number       = {5-6},
  pages        = {853--862},
  title        = {The influence of orbital rotation on the energy of closed-shell wavefunctions},
  url          = {http://dx.doi.org/10.1080/00268976.2013.874600},
  volume       = {112},
  year         = {2014},
}

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