Assessment of the ΔSCF density functional theory approach for electronic excitations in organic dyes

This paper assesses the accuracy of the Delta SCF method for computing low-lying HOMO -> LUMO transitions in organic dye molecules. For a test set of vertical excitation energies of 16 chromophores, surprisingly similar accuracy is observed for time-dependent density functional theory and for Delta SCF density functional theory. In light of this performance, we reconsider the ad hoc Delta SCF prescription and demonstrate that it formally obtains the exact stationary density within the adiabatic approximation, partially justifying its use. The relative merits and future prospects of Delta SCF for simulating individual excited states are discussed. (C) 2011 American Institute of Physics. [doi:10.1063/1.3530801]