Quasiparticle band structure and optical spectrum of LiF(001)

We present the quasiparticle band structure and the optical excitation spectrum of bulk LiF and the LiF(001)-(1×{}1) surface. First, we calculate the ground-state geometry of the bulk and the surface using density-functional theory within the local-density approximation. Next, applying the GW approximation for the self-energy, we evaluate the corresponding quasiparticle band structure. Finally, we calculate the electron-hole interaction, solve the Bethe-Salpeter equation for the two-particle Green function, and investigate the optical-absorption spectrum. The obtained spectrum of bulk LiF, which is dominated by a strong exciton peak at 12.7 eV, is in good agreement with experiment. At the LiF(001)-(1×{}1) surface, the excitonic effects are strongly modified with respect to the bulk. In particular, we observe a surface exciton at 12.3 eV, i.e., 0.4 eV below the bulk exciton.