Ab initio investigation of carbon-related defects in silicon

Ab initio total-energy calculations based on the local-density-functional, pseudopotential, and supercell approximations are performed to investigate carbon defects in silicon. The geometry and the formation energy of substitutional and impurity-vacancy defects are studied including the relaxation of nearest and next-nearest neighbors. Results for substitutional carbon appear to be consistent with a recently suggested reinterpretation of the available experimental formation energy data. Results for the interaction energy between a carbon atom and a silicon vacancy predict a small binding energy of 0.19 eV.