Abstract
Quasiparticle gaps and exciton Coulomb energies of H-passivated spherical Si nanoshells are
computed using rst principles SCF and GW methods. We nd that the quasiparticle gap of
a nanoshell depends on both its inner radius R1 (weakly) and outer radius R2 (strongly). These
dependences on R1 and R2 are mostly consistent with electrostatics of a metallic shell. We also
nd that the unscreened Coulomb energy ECoul in Si nanoshells has a somewhat unexpected size
dependence at xed outer radius R2: ECoul decreases as the nanoshell becomes more con ning,
contrary to what one would expect from quantum con nement e ects. We show that this is a
consequence of an increase in the average electron-hole distance, giving rise to reduced exciton
Coulomb energies in spite of the reduction in the con ning nanoshell volume.
