High temperature diffusion in a NiO tilt grain boundary: A molecular dynamics study

The high temperature behaviour of a Sigma = 5 (310) symmetric tilt Grain Boundary (GB) has been investigated by molecular dynamics simulation using a rigid ion potential fitted for NiO. The diffusion of cation vacancies has been studied in a temperature range T = 2250-2650 K. A graphical analysis of the atomic trajectories has been used to characterise the defect jumps. The diffusion coefficient of the nickel vacancies has been calculated via the computation of the: defect jump frequencies. The corresponding activation energy for the vacancy migration is found to be smaller than the bulk value obtained with a similar approach. The ratio between GB and bulk atomic self diffusion constants for nickel has also been evaluated and compared to the experimental results.