Developments in excited-state density functional theory

This article discusses the reasons behind the apparent lack of success of d ensity functional theory (DFT), during the past three decades, with excited states of many-electron systems. It describes various variational and non- variational approaches developed so far for dealing with this problem. Thos e include Theophilou's equiensemble approach, extended to unequally weighte d ensembles by Gross et al., Fritsche's wavefunction partitioning approach, local scaling transformation theory by Kryachko et al., the work-function formalism developed by Harbola and Sahni, etc. Through intimate connections between time-dependence and excited states, under a perturbation, various time-dependent (TD) DFT approaches to excited states, e.g., a quantum fluid dynamical approach, a TD density-functional response theory and a TD optim ized effective potential approach, are also reviewed. (C) 1999 Elsevier Sci ence B.V. All rights reserved.