Temperature dependence of migration features of self-interstitials in zirconium

摘要

Molecular dynamics simulations are conducted to study self-interstitial migration in zirconium.By defining crystal lattice points where more than one atom is present in corresponding Wigner-Seitz cells,as the locations of self-interstitial atoms (LSIAs),three types of events are identified as LSIA migrations:the jump remaining in one <11-20> direction (ILJ),the jump from one <11-20> to another <11-20> 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 are calculated.ILJ is found to be a dominant event in a temperature range from 300 K to 1200 K,but the occurrence frequencies of OLJ and OPJ increase with temperature increasing.The total occurrence frequency of all jump types has a good linear dependence on temperature.Moreover,the migration trajectories of LSIAs in the hcp basal-plane is not what is observed if only conventional one-or two-dimensional migrations exists;rather,they exhibit the feature that we call fraction-dimensional.Using Monte Carlo simulations,the potential kinetic effects of fraction-dimensional migration,which is measured by the average number of lattice sites visited per jump event (denoted by nSPE),are analysed.The significant differences between the nspE value of the fraction-dimensional migration and those of conventional one-and two-dimensional migrations suggest that the conventional diffusion coefficient cannot give an accurate description of the underlying kinetics of SIAs in Zr.This conclusion could be generally meaningful for the cases where the low-dimensional migration of defects are observed.