Low-dimension self-interstitial diffusion in α-Zr

The mobility of self-interstitials in α-zirconium (α-Zr) is studied with molecular dynamic (MD) and molecular static (MS) simulations, using Ackland's many-body inter-atomic potential. The basal crowdion configuration is found to be the ground state. Four types of diffusion jumps can be identified via MS, in-plane in-line, in-plane off-line, out-of-plane in-line and out-of-plane off-line. The in-plane migration is dominated by one-dimensional crowdion motion along the [11 anti 20] directions, interrupted from time to time by off-line or out-of-plane jumps. Based on the MS results, the activation energies and pre-exponentials for the diffusion processes are determined by fits to the Arrhenius plots of Dc and Da. The diffusional anisotropy factor Dc/Da is also obtained, and compares well with experimental results. The mean frequency of each type of jumps is then found using Monte Carlo simulation, and is reported as a function of temperature. The mean lifetime and mean free path of the one-dimensional mobility are then obtained. The 1-D mean free path is found to be unimportant for sink separations involved under the usual irradiation damage conditions. (orig.)