Paramagnetic Structure of the Soliton of the 30° Partial Dislocation in Silicon

Based on ab initio calculations, we propose a new structure for the fundamental excitation of the reconstructed 30° partial dislocation in silicon. This soliton has a rare structure involving a fivefold coordinated atom near the dislocation core. The unique electronic structure of this defect is consistent with the electron spin resonance signature of the hitherto enigmatic thermally stable $R$ center of plastically deformed silicon. This identification suggests the possibility of an experimental determination of the density of solitons, a key defect in understanding the plastic flow of the material.