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We revisit the Hartree-Fock (HF) calculation for the uniform electron gas, orjellium model, whose predictions -- divergent derivative of the energydispersion relation and vanishing density of states (DOS) at the Fermi level --are in qualitative disagreement with experimental evidence for simple metals.Currently, this qualitative failure is attributed to the lack of screening inthe HF equations. Employing Slater's hyper-Hartree-Fock (HHF) equations,derived variationally, to study the ground state and the excited states ofjellium, we find that the divergent derivative of the energy dispersionrelation and the zero in the DOS are still present, but shifted from the Fermiwavevector and energy of jellium to the boundary between the set ofvariationally optimised and unoptimised HHF orbitals. The location of thisboundary is not fixed, but it can be chosen to lie at arbitrarily high valuesof wavevector and energy, well clear from the Fermi level of jellium. Weconclude that, rather than the lack of screening in the HF equations, thewell-known qualitative failure of the ground-state HF approximation is anartifact of its nonlocal exchange operator. Other similar artifacts of the HFnonlocal exchange operator, not associated with the lack of electroniccorrelation, are known in the literature.

A correction for the Hartree-Fock Density of States for Jellium without Screening