  Within the framework of ab initio time-dependent density-functional theory
(TD-DFT), we propose a static approximation to the exchange-correlation kernel
based on the jellium-with-gap model. This kernel accounts for electron-hole
interactions and it is able to address both strongly bound excitons and weak
excitonic effects. TD-DFT absorption spectra of several bulk materials (both
semiconductor and insulators) are reproduced in very good agreement with the
experiments and with a low computational cost.
