  MD simulations were conducted to study the self-interstitial migration in
zirconium. By defining the crystal lattice point, at which more than one atom
fall in the Wigner-Seitz cell of the lattice point, for the location of
interstitial atoms (LSIA), three types of events were identified for LSIA
migration: the jump remaining in one <112_0> direction (ILJ), the jump from one
<112_0> to another <112_0> direction in the same basal plane (OLJ) and the jump
from one basal plane to an adjacent basal plane (OPJ). The occurrence
frequencies of the three types were calculated. ILJ was found to be the
dominant event in the temperature range (300K to 1200K), but the occurrence
frequencies of OLJ and OPJ increased with increasing temperature. Although the
three types of jumps may not follow Brownian and Arrhenius behavior, on the
whole, the migration of the LSIAs tend to be Brownian-like. Moreover, the
migration trajectories of LSAs in the hcp basal-plane are not what are observed
if only conventional one- or two-dimensional migrations exist; rather, they
exhibit the feature we call fraction-dimensional. Namely, the trajectories are
composed of line segments in <112_0> directions with the average length of the
line segments varying with the temperature. Using MC simulations, the potential
kinetic impacts of the fraction-dimensional migration, measured by the average
number of lattice sites visited per jump event n_SPE was analyzed. The
significant differences between the n_SPE value of the fraction-dimensional
migration and those of the conventional one- and two-dimensional migrations
suggest that the conventional diffusion coefficient, which cannot reflect the
feature of fraction-dimensional migration, cannot give an accurate description
of the underlying kinetics of SIAs in Zr.
