Vacancy interaction with dislocations in silicon: The shuffle-glide competition

Competition between the two alternative positions (shuffle and glide {111} plane subsets) for the core of a 30 degrees partial dislocation in Si is ex amined. Using a combination of nb initio total energy calculations with fin ite temperature free-energy calculations based on an interatomic potential, we obtained free energies for the relevant vacancy-type core defects. Gene rally, the free energy of vacancy formation in the core of a 30 degrees gli de partial dislocation is considerably lower (by more than 1 eV) than in th e bulk. However, even at high temperatures, the predicted thermal concentra tion of the shuffle segments comprised of a row of vacancies in the core is low, placing the 30 degrees partial dislocation in the glide subset positi on.