A comparison of orthogonal sp-based tight-binding models for silicon

Three common sp-based orthogonal tight-binding models of silicon (Goodwin–Skinner–Pettifor (GSP), Kwon et al., and Sawada) have been compared for their suitability for use in atomic-scale semiconductor simulation. We found that increased complexity of the functional form does not necessarily translate into improved results. For most of the static and dynamic properties we studied, no one form was clearly superior to the others. There is, however, a distinct correlation between the properties used in the parameterization and the strengths of a given model, e.g. the KWON model is particularly effective in predicting defect properties (for which it was designed). We provide the first comprehensive review of tight-binding predictions of the nature of the structure around a vacancy. Both GSP and KWON tight-binding models give seven vacancy structures of comparable formation energies (except the tetrahedral for GSP and C2v for KWON). A new “asymmetric” distortion was found for the GSP model which proved to be comparably stable to the tetragonal structure favored by LDA. In comparison, the KWON model predicts the split vacancy as the most stable vacancy structure, though it too provides a low energy tetragonal structure. Web access is provided to a tight-binding MD code which incorporates all three models.