  We present a framework for obtaining reliable solid-state charge and optical
excitations and spectra from optimally-tuned range-separated hybrid density
functional theory. The approach, which is fully couched within the formal
framework of generalized Kohn-Sham theory, allows for accurate prediction of
exciton binding energies. We demonstrate our approach through first principles
calculations of one- and two-particle excitations in pentacene, a molecular
semiconducting crystal, where our work is in excellent agreement with
experiments and prior computations. We further show that with one adjustable
parameter, set to produce an accurate bandgap, this method accurately predicts
band structures and optical spectra of silicon and lithium flouride,
prototypical covalent and ionic solids. Our findings indicate that for a broad
range of extended bulk systems, this method may provide a computationally
inexpensive alternative to many-body perturbation theory, opening the door to
studies of materials of increasing size and complexity.
