Real-space density-functional calculations for Si divacancies with large size supercell models

First-principles density-functional calculations of divacancies in crystalline silicon are performed with large size super-cell models which correspond to the unit cell of 64-1000 Si atoms. The calculations are performed by the newly developed real-space finite-difference pseudopotential code in parallel computation. It is found that the model size is large enough to provide a converged divacancy structures. A structure which is predicted by the early experiment and the recent cluster model calculation, is not found. Our own cluster calculation also corroborate the finding.