We study the role of electronic structure (band gaps) and long-range van der Waals interactions on the stability and mobility of point defects in silicon and heavier semiconductors. Density functional theory calculations with hybrid functionals that contain part of Hartree-Fock exchange energy are essential to achieve reasonable description of defect electronic levels, leading to accurate defect formation energies. However, these functionals signicantly overestimate the experimental migration barriers. The inclusion of screened vdW interactions further improves the description of defect formation energies, signicantly changes the barrier geometries, and brings migration barrier heights into close agreement with experimental values. These results suggest that hybrid functionals with vdW interactions can be successfully used for predictions in broad range of materials where the correct description of both the electronic structure and the long-range electron correlation is essential.
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