Symmetry and degeneracy in density functional theory

The superhamiltonian formalism is used to construct a totally symmetric sup erdensity for a system whose ground state corresponds to a multidimensional irreducible representation of the symmetry group of the Hamiltonian. A Hoh enberg-Kohn theorem is proven and the Levy constrained-search procedure is adapted. An appropriate generalization allows the application of this proce dure to degenerate excited states. (C) 2001 John Wiley & Sons, Inc.