A new orbital optimization for the multiconfiguration self-consistent field method is presented. This method combines a second-order (SO) algorithm for the optimization of the active orbitals with the first-order super configuration interaction (SCI) optimization of the remaining closed-virtual rotations and is denoted as the SO–SCI method. The SO–SCI method significantly improves the convergence as compared to the conventional SCI method. In combination with density fitting, the intermediates from the gradient calculation can be reused to evaluate the two-electron integrals required for the active Hessian without introducing a large computational overhead. The orbitals and CI coefficients are optimized alternately, but the CI-orbital coupling is accounted for by the limited memory Broyden–Fletcher–Goldfarb–Shanno quasi-Newton method. This further improves the speed of convergence. The method is applicable to large molecules. The efficiency and robustness of the presented method is demonstrated in benchmark calculations for 21 aromatic molecules as well as for various transition metal complexes with up to 826 electrons and 5154 basis functions.
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21 February 2020
Research Article|
February 19 2020
MCSCF optimization revisited. II. Combined first- and second-order orbital optimization for large molecules
David A. Kreplin
;
David A. Kreplin
a)
1
Institut für Theoretische Chemie, Universität Stuttgart
, Pfaffenwaldring 55, D-70569 Stuttgart, Germany
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Peter J. Knowles
;
Peter J. Knowles
b)
2
School of Chemistry, Cardiff University
, Main Building, Park Place, Cardiff CF10 3AT, United Kingdom
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Hans-Joachim Werner
Hans-Joachim Werner
c)
1
Institut für Theoretische Chemie, Universität Stuttgart
, Pfaffenwaldring 55, D-70569 Stuttgart, Germany
c)Author to whom correspondence should be addressed: werner@theochem.uni-stuttgart.de
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a)
Electronic mail: kreplin@theochem.uni-stuttgart.de
b)
Electronic mail: knowlespj@cardiff.ac.uk
c)Author to whom correspondence should be addressed: werner@theochem.uni-stuttgart.de
J. Chem. Phys. 152, 074102 (2020)
Article history
Received:
December 11 2019
Accepted:
January 29 2020
Citation
David A. Kreplin, Peter J. Knowles, Hans-Joachim Werner; MCSCF optimization revisited. II. Combined first- and second-order orbital optimization for large molecules. J. Chem. Phys. 21 February 2020; 152 (7): 074102. https://doi.org/10.1063/1.5142241
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