Sensitivity of point defect characteristics to the interatomic potential range

Abstract

Point defect characteristics, including configuration and relaxation energies of vacancies and interstitials, migration energies of vacancies, and binding energies of divacancies, are determined by computer simulation using models representing copper and α-iron. The sensitivity of these characteristics to small variations in the range of the interatomic potential is studied using potentials of the Morse type modified to include third or fourth neighbors. Vacancy relaxation energies were found to increase and migration energies decrease with increased range. Divacancy binding energies were generally insensitive to range, but were appreciably higher than found with first and second neighbor potentials. The energies of interstitial configurations varied markedly with range, but retained their relative order with one minor exception. The lowest energy configuration for copper was the (100) split, in agreement with previous work. The lowest energy configurations for α-iron, however, were the crowdions, rather than the (110) split configuration found in previous work using shallower second neighbor potentials. The significance of arbitrary potential cutoffs and small discontinuities is discussed.