The formulation of a constricted variational density functional theory for double excitations

Abstract

We have recently introduced a new version of the constricted nth-order variational density functional method (CV(n)-DFT) in which the occupied excited-state orbitals are allowed to relax in response to the change of both the Coulomb and exchange–correlation potential in going from the ground state to the excited state. The new scheme is termed the relaxed self-consistent field nth-order constricted variational density functional (RSCF-CV(n)-DFT) method. We demonstrate in the current study that it is possible to extend RSCF-CV(∞)-DFT to double excitations. It is further shown that it is possible within certain limitations to derive a second-order CV(2)-DFT theory that can be considered as an extension of adiabatic time-dependent density functional theory (TDDFT) to double excitations within the Tamm–Dancoff approximation.

Keywords:

• density functional theory
• time-dependent density functional theory
• excited states
• constricted density functional theory

Acknowledgements

T. Ziegler would like to thank the Canadian government for a Canada research chair in theoretical inorganic chemistry.

Additional information

Funding

T. Ziegler would like to thank Natural Science and Engineering Research Council of Canada (NSERC) for financial support.