Charge-transfer in time-dependent density-functional theory via spin-symmetry-breaking

Long-range charge-transfer excitations pose a major challenge for time-dependent density-functional approximations. We show that spin-symmetry breaking offers a simple solution for molecules composed of open-shell fragments, yielding accurate excitations at large separations when the acceptor effectively contains one active electron. Unrestricted exact-exchange and self-interaction-corrected functionals are performed on one-dimensional models and on the real LiH molecule within the pseudopotential approximation to demonstrate our results.
We acknowledge support from MEC (Grant No. FIS2007-65702-C02-01), ACI promociona (Grant No. ACI2009-1036), Grupos Consolidados UPV/EHU del Gobierno Vasco (Grant No. IT-319-07), the e-I3 ETSF project (Contract No. 211956), the National Science Foundation (Grant No. CHE-0647913), and the Cottrell Scholar Program of the Research Corporation for Science Advancement, as well as a grant of computer time from the CUNY High Performance Computing Center under NSF Grants No. CNS-0855217 and No. CNS-0958379.