The maximal excess charge in M\"uller density-matrix-functional theory
  We consider an atom described by M\"uller theory, which is similar to Hartree-Fock theory, but with a modified exchange term. We prove that a nucleus of charge Z can bind at most Z+C electrons, where C is a universal constant. Our proof proceeds by comparison with Thomas-Fermi theory and a key ingredient is a novel bound on the number of electrons far from the nucleus. 
Rupert L. Frank, Phan Th\`anh Nam, Hanne Van Den Bosch
math-ph math.AP math.MP