  Density Functional Resonance Theory (DFRT) is a complex-scaled version of
ground-state Density Functional Theory (DFT) that allows one to calculate the
resonance energies and lifetimes of metastable anions. In this formalism, the
exact energy and lifetime of the lowest-energy resonance of unbound systems is
encoded into a complex "density" that can be obtained via complex-coordinate
scaling. This complex density is used as the primary variable in a DFRT
calculation just as the ground-state density would be used as the primary
variable in DFT. As in DFT, there exists a mapping of the N-electron
interacting system to a Kohn-Sham system of N non-interacting particles in
DFRT. This mapping facilitates self consistent calculations with an initial
guess for the complex density, as illustrated with an exactly-solvable model
system. Whereas DFRT yields in principle the exact resonance energy and
lifetime of the interacting system, we find that neglecting the
complex-correlation contribution leads to errors of similar magnitude to those
of standard scattering close-coupling calculations under the bound-state
approximation.
