Excitons and optical properties of α-quartz

We present an ail initio study of the optical properties of ru-quartz. The absorption spectrum is calculated by solving the Bethe-Salpeter equation for the interacting electron-hole system and found to be in excellent agreement with the measured spectrum up to 10 eV above the absorption threshold. We find that excitonic effects are crucial in understanding the sharp features in the absorption spectrum in this energy range. They are also crucial in the nb initio computation of the static dielectric constant, significantly enhancing its value.