Study of point defects diffusion in nickel using kinetic activation-relaxation technique

Kinetic Monte Carlo Simulations of Irradiation Effects

“…This allowed to demonstrate that in bcc Fe, suppressing long-range interactions mainly influences kinetics in the first 0.3 ms, slowing down quick energy release cascades seen more frequently in full simulations, whereas long-term behavior and final state are not significantly affected (Brommer et al 2014). Similar studies were performed in Si (Trochet et al 2015) and Ni (Mahmoud et al 2018), with the identification of previously unreported multistep diffusion mechanisms that are as fast or even faster than those used generally. For example, while the barrier for the single Ni self interstitial is only 0.15 eV, Ni tetra-self-interstitials ( Figure 2) diffuse with almost zero energy barrier (0.004 eV) through a three-step process involving a rotation and a jump mechanisms (Mahmoud et al 2018).…”

“…Similar studies were performed in Si (Trochet et al 2015) and Ni (Mahmoud et al 2018), with the identification of previously unreported multistep diffusion mechanisms that are as fast or even faster than those used generally. For example, while the barrier for the single Ni self interstitial is only 0.15 eV, Ni tetra-self-interstitials ( Figure 2) diffuse with almost zero energy barrier (0.004 eV) through a three-step process involving a rotation and a jump mechanisms (Mahmoud et al 2018).…”

“…a), b), c), d) and e) present the structure with one, two, three, four and five mono-self-defects for each case. From (Mahmoud 2018) Off-lattice KMC methods are even more important when strain and randomness play an important role, such as for characterizing the 100-interstitial loop formation in Fe (Xu et al 2013), following the relaxation of ion-bombarded silicon over long-time (more than 1 s) (Béland et al 2013) (Béland et al 2013) or understanding C diffusion at an Fe grain boundary, where pathways are strongly influenced by the local deformation (Restrepo et al 2018).…”

Interaction of impurity atoms of light elements with self-interstitials in fcc metals

“…The migration energy of self-interstitial atoms in pure metals is very low, which causes their high diffusion mobility. For comparison, in works [6,19,27], the following data, mainly by computer simulation, were obtained: 0.04 -0.15 eV in Ni, 0.05 -0.12 eV in Ag and 0.03 -0.1 eV in Al.…”

“…Self-interstitial atoms have unique diffusion mobility. The activation energy of self-interstitials migration is significantly lower than the migration energy of other point defects [5,6]. The mechanism of self-interstitial migration is ambiguous and even in a pure crystal it has at least two variants: dumbbell and crowdion mechanisms [7,8].…”