Three Lagrangians for the complete-active space coupled-cluster method

Abstract

Three fully variational formulations of the complete-active space coupled-cluster (CASCC) 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 CAS 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 calculation and of quantum chemical density-matrix renormalization group methods, which are fast and polynomial scaling, but lacks 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.

References in corpus (4)

• The density matrix renormalization group for ab initio quantum chemistry
• Time-dependent multiconfiguration self-consistent-field method based on occupation restricted multiple active space model for multielectron dynamics in intense laser fields
• Tailored Coupled Cluster Theory in Varying Correlation Regimes
• Ultrafast ab-initio Quantum Chemistry Using Matrix Product States

Cited by in corpus (2)

• Sub-system self-consistency in coupled cluster theory
• Complete Active Space Iterative Coupled Cluster Theory