Molecular Dynamics Study of Interaction of Carbon, Nitrogen, and Oxygen Impurity Atoms with Self-Interstitial Atoms in Nickel, Silver and Aluminum

Abstract

The interaction of impurity atoms of carbon, nitrogen, and oxygen with self-interstitial atoms in FCC metals like nickel, silver, and aluminum is studied using the molecular dynamics method. It is found that the self-interstitial atom migration in the crystal lattice follows two mechanisms: dumbbell and crowdion. In this case, the first mechanism that includes one interatomic distance displacement and the rotation of the <001> dumbbell is characterized by broken paths of atomic migration. The second mechanism is described by straight paths along the close-packed directions <011> in the crystal.
 The binding energies between impurity atoms and selfinterstitial atoms in Ni, Ag, and Al are calculated in the paper. It is shown that impurity atoms are effective “traps” for interstitial atoms that migrate relatively quickly in a crystal. During the interaction of an interstitial and an impurity atom, the interstitial atom forms a dumbbell configuration with an axis along the <001> direction, and the impurity atom is located in the nearest octahedral pore. It is found that the mobility of interstitial atoms is significantly reduced due to the presence of impurities in the metal. The introduction of 10 % impurity atoms leads to a severalfold increase in the migration energy of interstitial atoms. At the same time, the contribution of the crowdion mechanism is noticeably reduced while the dumbbell mechanism contribution is increased.