Electronic and elastic properties of edge dislocations in Si

Ab initio, tight-binding, and classical calculations have been done for (a/2)( 110) edge dislocation dipoles in Si at separations of 7.5-22.9 A in unit cells comprising 32-288 atoms. These calculations show states associated with the cores relatively deep in the band gap (~ 0.2 eV) despite the absence of dangling bonds. The shifts in the electronic states depend significantly on separation d and are correlated with a concentration of strain in the cores as the dislocations become more isolated. The strain energies exhibit a logarithmic dependence on d consistent with linear elasticity for all system sizes.