The exchange energy of a uniform electron gas experiencing a new, flexible range separation

The exchange energy of a uniform electron gas which experiences a two-parameter separation of the Coulomb interaction is derived as a local functional of the electron density. The two parameter range separator allows separate control of where and how rapidly the Coulomb interaction is switched off. The usefulness of the functional is briefly assessed by combination with a recently published pair of exchange and correlation functionals. The self-interaction error of noble-gas dimer cation dissociation is found to be reduced while thermochemistry is relatively unperturbed. These results suggest that changes in attenuator shape can improve range-separated functionals.