Quasidiabatic states described by coupled-cluster theory.
In an attempt to expand the utility of the model Hamiltonian technique developed by Koppel, Domcke, and Cederbaum (KDC) [Adv. Chem. Phys. 57, 59 (1984)], an ansatz for quasidiabatic wave functions is introduced in the framework of equation-of-motion coupled-cluster (EOM-CC) theory. Based on the ansatz, the theory for the analytic first derivative of the off-diagonal element of the quasidiabatic potential matrix is developed by extending the theory for the analytic gradient of the EOM-CC energy. This analytic derivative is implemented for EOM-CCSD (singles and doubles approximation) calculations of radicals subject to pseudo-Jahn-Teller and Jahn-Teller interactions. Its applicability in construction of the KDC quasidiabatic model potential is discussed.
Department of Chemistry and Biochemistry, Institute for Theoretical Chemistry, The University of Texas at Austin, Austin, Texas 78712, USA.
Takatoshi
T
Ichino
Jürgen
J
Gauss
John F
JF
Stanton