title: Spurious interactions, and their correction, in the ensemble-Kohn-Sham scheme for excited States.
abstract: We observe that the direct Coulomb (Hartree) term appearing in the ensemble-density-functional theory for excited states contains an unphysical ("ghost") interaction which has to be corrected by the ensemble exchange and correlation functional. We propose a simple additive correction to the conventional ensemble exchange energy in the form of an orbital functional. By treating this corrected exchange energy functional self-consistently within the optimized effective potential method one finds a significant improvement of atomic excitation energies.
authors.affiliation: Rutherford Appleton Laboratory, Isis Facility, Chilton, Didcot, Oxfordshire, OX11 0QX, United Kingdom.
authors.forename: N I
authors.initials: NI
authors.lastname: Gidopoulos
authors.forename: P G
authors.initials: PG
authors.lastname: Papaconstantinou
authors.forename: E K U
authors.initials: EK
authors.lastname: Gross