In this paper, we study the nuclear gradients of heat bath configuration interaction self-consistent field (HCISCF) wave functions and use them to optimize molecular geometries for various molecules. We show that HCISCF nuclear gradients are fairly insensitive to the size of the “selected” variational space, which allows us to reduce the computational cost without introducing significant errors. The ability of the HCISCF to treat larger active spaces combined with the flexibility for users to control the computational cost makes the method very attractive for studying strongly correlated systems, which require a larger active space than possible with a complete active space self-consistent field. Finally, we study the realistic catalyst, Fe(PDI), and highlight some of the challenges this system poses for density functional theory (DFT). We demonstrate how HCISCF can clarify the energetic stability of geometries obtained from DFT when the results are strongly dependent on the functional. We also use the HCISCF gradients to optimize geometries for this species and study the adiabatic singlet–triplet gap. During geometry optimization, we find that multiple near-degenerate local minima exist on the triplet potential energy surface.
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7 September 2022
Research Article|
September 01 2022
Near-exact nuclear gradients of complete active space self-consistent field wave functions Available to Purchase
James E. T. Smith
;
James E. T. Smith
a)
(Investigation, Software, Writing – original draft, Writing – review & editing)
1
Center for Computational Quantum Physics, Flatiron Institute
, New York, New York 10010, USA
2
Department of Chemistry, University of Colorado Boulder
, Boulder, Colorado 80309, USA
a)Author to whom correspondence should be addressed: [email protected]
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Joonho Lee
;
Joonho Lee
b)
(Investigation, Supervision)
3
Department of Chemistry, Columbia University
, New York, New York 10027, USA
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Sandeep Sharma
Sandeep Sharma
(Supervision, Writing – original draft, Writing – review & editing)
2
Department of Chemistry, University of Colorado Boulder
, Boulder, Colorado 80309, USA
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James E. T. Smith
1,2,a)
Joonho Lee
3,b)
Sandeep Sharma
2
1
Center for Computational Quantum Physics, Flatiron Institute
, New York, New York 10010, USA
2
Department of Chemistry, University of Colorado Boulder
, Boulder, Colorado 80309, USA
3
Department of Chemistry, Columbia University
, New York, New York 10027, USA
a)Author to whom correspondence should be addressed: [email protected]
b)
Electronic mail: [email protected]
J. Chem. Phys. 157, 094104 (2022)
Article history
Received:
January 17 2022
accepted-manuscript-online:
June 24 2022
Accepted:
June 24 2022
Citation
James E. T. Smith, Joonho Lee, Sandeep Sharma; Near-exact nuclear gradients of complete active space self-consistent field wave functions. J. Chem. Phys. 7 September 2022; 157 (9): 094104. https://doi.org/10.1063/5.0085515
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