  We have theoretically examined the size dependence of the equilibrium lattice
constant of nanocrystals of Si, GaAs and CdSe. While deviations from the bulk
lattice constant are as large as 1-2% for unpassivated nanocrystals of Si, the
deviations drop to ~ 0.3%-0.4% once the surfaces are passivated. Inspite of the
fact that the average equilibrium bond-lengths are bulk-like, we find that the
nearest-neighbor bond-length exhibits an unusual strain profile with bulk like
bond-lengths in the core and shorter (~ 1%) bonds at the surface.
