Alloy decomposition during growth due to mobility differences

During growth of an alloy, any evolution of the surface morphology can lead to nonuniform composition. This occurs because there is always some difference in the mobility of the respective atoms. We examine in particular the much-studied case of a surface under stress. In this case there are two mechanisms driving decomposition---the different atomic sizes and the different mobilities. Depending on the system, the effect of mobility difference can dominate or even cancel the well-known effect of atomic size difference.