To perform a similar type of analysis, consider the following hints and recommendations:
Use large time steps in a transient analysis. For example, in this problem time steps of 1x106 seconds and larger are used. Small steps are unnecessary and may contribute to spatially varying concentration oscillations. A steady-state (static) analysis is also possible.
Due to very low atomic diffusivity, materials such as copper may show spatially varying concentration oscillations. In such cases, a tetrahedral mesh of these regions may be preferred.