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 examined. Using a combination of ab initio total energy calculations with finite temperature free-energy calculations based on an interatomic potential, we obtained free energies for the relevant vacancy-type core defects. Generally, the free energy of vacancy formation in the core of a 30 degrees glide partial dislocation is considerably lower (by more than 1 eV) than in the bulk. However, even at high temperatures, the predicted thermal concentration 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 position.