Interatomic force fields for the structure of intrinsic point defects in silicon

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Abstract
We present calculations for the energy and structure of vacancies and intrinsic interstitials in crystalline silicon using a recently developed interatomic force field. Our classical potential explicitly includes quantum effects such as the strengthening of back bonds produced by broken bonds. Although the parameters in our force field are fit to bulk crystalline and microcluster properties of silicon, the structure of these defects as determined from our potential is in good agreement with the structure obtained from fully quantum-mechanical calculations. Our estimates for the defect formation energies generally exceed somewhat the values obtained from quantum calculations. We attribute these differences to Jahn-Teller distortions, which are not included in classical potentials, and to a small overestimate of the ‘‘stiffness’’ of the crystalline lattice.