Period-doubled structure for the 90 degrees partial dislocation in silicon

We suggest that the commonly accepted core structure of the 90 degrees partial dislocation in Si may not be correct, and propose instead a period-doubled structure. We present local-density approximation, tight-binding, and classical Keating-model calculations, all of which indicate that the period-doubled structure is lower in energy. The new structure displays a broken mirror symmetry in addition to the period doubling, leading to a wide variety of possible solitonlike defects and kinks.