Linear response and the exchange-correlation hole within a screened-exchange density functional theory

Justification is provided for a hybrid density functional for electronic systems [Seidl ct al., Phys. Rev. B 53, 3764 (1996)] combining a screened-exchange term with a local approximation to the remaining exchange-correlation energy. It is argued that this functional correctly models an important part of the exchange-correlation hole. With an appropriate and explicitly specified choice of interaction, it accurately reproduces the exact linear density response function of the homogeneous electron gas. These results imply significant improvements over the usual local density approximation (LDA).