Welcome to the Gamess+DF Homepage
Gamess+DF
A package that incorporates dual functional—Tamm Dancoff approximation,
and the MN12-L, MN15-L, MN15 density functionals into GAMESS
A Quick Introduction to Dual Functional-Tamm Dancoff Approximation (DF-TDA)
The potential energy surfaces (PESs) computed by KS-TDA are known to have incorrect topology near conical intersection (CI) geometries. This is due to the lack of coupling between the ground-state KS determinant and TDA singly excited determinants. DF-TDA employs two different functionals: F1 for orbital optimization and F2 for TDA Hamiltonian construction, and hence the coupling is introduced. In many cases, DF-TDA is as accurate as KS-TDA with F2, with 0.1 eV higher excitation energies in a typical case we examined. In addition, DF-TDA predicts the correct dimensionality of PESs near CI seams. Therefore DF-TDA can be used in understanding and modeling electronically nonadiabatic processes involving ground and excited states.
The potential energy surfaces (PESs) computed by KS-TDA are known to have incorrect topology near conical intersection (CI) geometries. This is due to the lack of coupling between the ground-state KS determinant and TDA singly excited determinants. DF-TDA employs two different functionals: F1 for orbital optimization and F2 for TDA Hamiltonian construction, and hence the coupling is introduced. In many cases, DF-TDA is as accurate as KS-TDA with F2, with 0.1 eV higher excitation energies in a typical case we examined. In addition, DF-TDA predicts the correct dimensionality of PESs near CI seams. Therefore DF-TDA can be used in understanding and modeling electronically nonadiabatic processes involving ground and excited states.