Methods Based on Constrained Density Functional Theory
- In DFT calculations, additional potentials can be added to the Hamiltonian to obtain charge-localized states, approximating diabatic states in electron transfer reactions.
- CDFT enables construct diabatic states, which may not be accessible with standard SCF calculations, and calculations of electronic couplings and other electron transfer parameters.
- Q-Chem offers two types of constraints: total charge or spin charge constraints on different molecular fragments.
Predict Reaction Barrier Heights with Constrained DFT based Configuration Interaction (CDFT-CI)
- Transition state energies are searched in the configuration space spanned by two diabatic-like configurations: reactant and product.
- The reactant and product configurations are obtained by applying charge- and spin-density constraints in DFT calculations, in order to maximally retain the reactant and product electronic character.
- CDFT-CI significantly improves the calculated reaction barrier heights compared to traditional DFT.