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  A perturbation-based super-CI approach for the orbital optimization of a CASSCF wave function

Kollmar, C., Sivalingam, K., Helmich-Paris, B., Angeli, C., & Neese, F. (2019). A perturbation-based super-CI approach for the orbital optimization of a CASSCF wave function. Journal of Computational Chemistry, 40(14), 1463-1470. doi:10.1002/jcc.25801.

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 Creators:
Kollmar, Christian1, Author           
Sivalingam, Kantharuban2, Author           
Helmich-Paris, Benjamin3, Author           
Angeli, Celestino4, Author
Neese, Frank1, Author           
Affiliations:
1Research Department Neese, Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_2541710              
2Research Group Wennmohs, Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_2541706              
3Research Group Helmich-Paris, Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_2541712              
4Dipartimento di Scienze Chimiche e Farmaceutiche, Università di Ferrara, Via Borsari 46, I‐44100 Ferrara, Italy, ou_persistent22              

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Free keywords: CASSCF; orbital optimization; configuration interaction; Dyall Hamiltonian
 Abstract: A perturbation theory‐based algorithm for the iterative orbital update in complete active space self‐consistent‐field (CASSCF) calculations is presented. Following Angeli et al. (J. Chem. Phys. 2002, 117, 10525), the first‐order contribution of singly excited configurations to the CASSCF wave function is evaluated using the Dyall Hamiltonian for the determination of a zeroth‐order Hamiltonian. These authors employ an iterative diagonalization of the first‐order density matrix including the first‐order correction arising from single excitations, whereas the present approach uses the single‐excitation amplitudes directly for the construction of the exponential of an anti‐Hermitian matrix resulting in a unitary matrix which can be used for the orbital update. At convergence, the single‐excitation amplitudes vanish as a consequence of the generalized Brillouin's theorem. It is shown that this approach in combination with direct inversion of the iterative subspace (DIIS) leads to very rapid convergence of the CASSCF iteration procedure.

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Language(s): eng - English
 Dates: 2018-11-212019-01-292019-02-232019-05-30
 Publication Status: Published in print
 Pages: 8
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1002/jcc.25801
 Degree: -

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Title: Journal of Computational Chemistry
  Abbreviation : J. Comput. Chem.
Source Genre: Journal
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Publ. Info: New York : Wiley
Pages: - Volume / Issue: 40 (14) Sequence Number: - Start / End Page: 1463 - 1470 Identifier: ISSN: 0192-8651
CoNE: https://pure.mpg.de/cone/journals/resource/954925489848