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.

 

CDFT_level_scheme

 

FAAQ
Total Charge Difference of the Charge-Localized State of the FAAQ Molecule

 

Cu-Ox
Spin Charge of the  Charge-localized State  of the Cu-Ox Molecule

 

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.
CDFT-CI-1
CDFT-CI-2