Direct diabatization of electronic states by the fourfold-way: Including dynamical correlation by multi-configuration quasidegenerate perturbation theory with complete active space self-consistent-field diabatic molecular orbitals.

Highlights: [•] Simplification of fourfold-way diabatization procedure. [•] Improved algorithm for diabatic states for simulating photochemical dynamics. [•] Complete active space SCF diabatic MOs for excited states with inclusion of dynamical correlation. [Copyright &y& Elsevier]