  Atomic-scale calculations for the dynamics of the 90$^0$ partial glide
dislocation in silicon are made using the effective-medium tight-binding
theory. Kink formation and migration energies for the reconstructed partial
dislocation are compared with experimental results for the mobility of this
dislocation. The results confirm the theory that the partial moves in the
dissociated state via the formation of stable kinks. The correlation between
glide activation energy and band gap in semiconducting systems is discussed.
