The same n=2, 16 atom, 64 electron system of diamond-structure
silicon that was used in the Coulomb finite size calculations
described in section 
was used to calculate a series
of energy gaps using the prescription given in Eq.()
within the VMC framework by the method of addition and subtraction of
electrons. Calculations were performed using the new
electron-electron interaction designed to remove the effects of the
periodic images of the additional (removed) electrons as described in
Eq.().