  Using atomistic pseudopotential wave functions we calculate the electron and
hole charging energies of InAs quantum dots. We find that the charging energies
depend strongly on the dielectric constant epsilon_out of the surrounding
material, and that when the latter is smaller than the dielectric constant of
the dot the electron-electron and hole-hole interactions are dominated by
surface-polarization effects. We predict the addition energies and the
quasi-particle gap as a function of size and epsilon_out. We find excellent
agreement with recent single-dot tunneling spectroscopy data for epsilon_out=6.
