  Quantum confinement increases the spacing between energy levels as the
nanocrystallite size is decreased. Its qualitative features hold both for
states localized near the center of a nanocrystallite and those near the
surface, such as states due primarily to dangling bonds. However, different
quantitative features are expected because of the different size constraints on
each of these states. Since the majority of atoms in a typical nanocrystallite
are on the surface, contrasting confinement effects between these two types may
prove useful in predicting how surface state dependent properties, such as
optical absorption, change with the size of the nanocrystallite. By applying
first principles pseudopotential methods to indium doped, uncapped CdSe
nanocrystallites containing 17 and 34 atoms, we identify center and surface
localized states. Using the lowest occupied energy state as a reference, the
energy of a state localized near the center is found to increase 24 mRy from
the 34 to 17 atom nanocrystallite. An equivalent surface state within the two
cases studied is not found, but the energy level spacing is speculated to
increase on the order of 100 mRy between the 34 and 17 atom cases based on
states that are highly local to the surface, but not equivalent. Furthermore,
we find it's necessary for the impurity to sit at the center of the
nanocrystallite in order for the impurity states to be electrically active.
