Dislocation Kink Motion in Silicon

Ductility is controlled at the atomic level by dislocation kink motion. The migration energy for kinks on the 30\ifmmode^\circ\else\textdegree\fi{} partial dislocation in silicon has been computed ab initio in agreement with experiment. The electronic structure changes from semiconducting to metallic at the saddle-point configuration. Band structure energy controls kink motion, so valence electrons control shearing motions involved with ductility, whereas tensile forces involved in fracture depend on both ion-ion and valence forces. Doping effects on dislocation mobility are explained.