The size dependence of the energy band gap for hydrogen saturated sili
con clusters, wires and slabs are calculated using all electron densit
y functional theory. The hydrogen saturation is considered as a model
for a wider band gap insulator enclosing the silicon structures. With
this perspective in mind, an effective mass model with finite barriers
for both valence and conduction band is found to semiquantatively acc
ount for the numerical findings. (C) 1995 American Institute of Physic
s.