Interatomic potentials in semiconductors and their validity for defect calculations

We discuss the validation of interatomic forces for defect calculations in semiconductors like silicon. Our tests include estimates of lattice response functions, defect steric energies, and relaxed atomic positions near defects. We find the variation from one potential to another to be substantial, notably because of the dominance of the bond-angle terms in the energy. Differences are less serious in the predicted geometries than in the predicted energies; which indicates preferred strategies for finding relaxed geometries.