Effect of Atomic Complexes Formation in Grain Boundaries on Grain Boundary Diffusion

Abstract

The peculiarities of grain boundary diffusion in Cu connected with the effect of atomic pairs formation in grain boundaries (GB) were studied using the molecular dynamics (MD) simulation. In present study Cu GB selfdiffusion was simulated with the use of semi-empirical potential. Besides, the ‘heterodiffusion’ simulation was performed with the artificially addеd energy of interaction (E) between identical atoms in arbitrary chosen pairs. To obtain reliable data on the mean square displacements (MSD) the simulation cell, consisted about three hundreds thousands atoms and two symmetrical GBs Σ5 (001)(012), was used. 70 pairs of identical Cu atoms in GBs, bonded into pairs, were chosen as initial state. Energy of interaction was varied between 0 and - 0.5eV/atomThe results obtained for selfdiffusion are in a good agreement with experimental results and other results of computer simulation. Two main effects for heterodiffusion are under discussion. The first is atomic exchange between GB zone and adjacent lattice zone, where the mobility of the atoms decreases significantly. As a result, the MSD decrease. Another effect is connected with attraction between the “marked” atoms, which leads to formation of relatively stable complexes and the MSD also decreases. The results obtained involve also dependence the number of the stable pairs on time and temperature and show the possibility of pairs to condense into ternary, quarterly and more numerous complexes.