Core reconstruction of the 90 degrees partial dislocation in nonpolar semiconductors

We investigate the energetics of the single-period and double-period core r econstructions of the 90 degrees partial dislocation in the homopolar semic onductors C, Si, and Ge. The double-period geometry is found to be lower in energy in all three materials, and the energy difference between the two g eometries is shown to follow the same trends as the energy gap and the stif fness. Both structures are fully reconstructed, consisting entirely of four fold coordinated atoms. They differ primarily in the detail of the local st rains introduced by the two reconstructions in the core region. The double- period structure is shown to introduce smaller average bond-length deviatio ns, at the expense of slightly larger average bond-angle bending distortion s, with respect to the single-period core. The balance between these two st rain components leads to the lower energy of the double-period reconstructi on. [S0163-1829(98)04944-3].