Generator coordinates: a new road towards dynamics and excitations in DFT

The generator-coordinate method is a flexible and powerful reformulation of the variational principle. Here we show that by introducing a generator coordinate in the Kohn-Sham equation of density-functional theory, excitation energies can be obtained from ground-state density functionals. Similarly, by introducing a generator coordinate in the equations of time-dependent DFT, memory effects can be built into any existing adiabatic exchange-correlation potential.(See J. Chem. Phys. 127, p. 124101 (2007) and J. Chem. Phys. 119, p. 1285 (2003).)