Three fully variational formulations of the complete-active space coupled-cluster method are derived. The formulations include the ability to approximate the model vectors by smooth manifolds, thereby opening up the possibility for overcoming the exponential wall of scaling for model spaces of complete-active space type. In particular, model vectors of matrix-product states are considered, and it is argued that the present variational formulation allows not only favorably scaling multireference coupled-cluster calculations but also systematic correction of tailored coupled-cluster calculations and of quantum chemical density-matrix renormalization group methods, which are fast and polynomial scaling but lack the ability to properly resolve dynamical correlation at chemical accuracy. The extension of the variational formulations to the time domain is also discussed, with derivations of abstract evolution equations.
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28 June 2023
Research Article|
June 26 2023
Three Lagrangians for the complete-active space coupled-cluster method Available to Purchase
Simen Kvaal
Simen Kvaal
a)
(Conceptualization, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Validation, Writing – original draft, Writing – review & editing)
Hylleraas Centre for Quantum Molecular Sciences, Department of Chemistry, University of Oslo
, P.O. Box 1033 Blindern, N-0315 Oslo, Norway
a)Author to whom correspondence should be addressed: [email protected]
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Simen Kvaal
a)
Hylleraas Centre for Quantum Molecular Sciences, Department of Chemistry, University of Oslo
, P.O. Box 1033 Blindern, N-0315 Oslo, Norway
a)Author to whom correspondence should be addressed: [email protected]
J. Chem. Phys. 158, 244113 (2023)
Article history
Received:
March 03 2023
Accepted:
June 08 2023
Citation
Simen Kvaal; Three Lagrangians for the complete-active space coupled-cluster method. J. Chem. Phys. 28 June 2023; 158 (24): 244113. https://doi.org/10.1063/5.0148988
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