title: Model space diabatization for quantum photochemistry.
abstract: Diabatization is a procedure that transforms multiple adiabatic electronic states to a new representation in which the potential energy surfaces and the couplings between states due to the electronic Hamiltonian operator are smooth, and the couplings due to nuclear momentum are negligible. In this work, we propose a simple and general diabatization strategy, called model space diabatization, that is applicable to multi-configuration quasidegenerate perturbation theory (MC-QDPT) or its extended version (XMC-QDPT). An advantage over previous diabatization schemes is that dynamical correlation calculations are based on standard post-multi-configurational self-consistent field (MCSCF) multi-state methods even though the diabatization is based on state-averaged MCSCF results. The strategy is illustrated here by applications to LiH, LiF, and thioanisole, with the fourfold-way diabatization and XMC-QDPT, and the results illustrate its validity.
authors: Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455, USA.
authors: Shaohong L
authors: SL
authors: Li
authors: Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455, USA.
authors: Donald G
authors: DG
authors: Truhlar
authors: Department of Chemistry, Iowa State University, Ames, Iowa 50011, USA.
authors: Michael W
authors: MW
authors: Schmidt
authors: Department of Chemistry, Iowa State University, Ames, Iowa 50011, USA.
authors: Mark S
authors: MS
authors: Gordon