A Comprehensive Computational Study of Adatom Diffusion on the Aluminum (1 0 0) Surface*

The complexity of adatom diffusion on the Al (100) surface is reflected by the existence of several low-energy non-trivial atomic exchange or vacancy formation mechanisms. Interestingly, these mechanisms have energy barriers lower than or comparable to that of the simple (and intuitive) hopping mechanism. While prior studies mainly used classical potentials to understand diffusion processes active on Al (100) surface, here we use accurate (and expensive) density functional theory (DFT) computations to estimate barriers associated with nine low-energy adatom diffusion mechanisms. We find that there exist several exchange mechanisms with energy barriers less than or equal to that of the trivial hop mechanism, thereby highlighting mechanisms that can be relevant during surface/crystal growth. Our results paint a highly complex picture of the diffusion landscape on Al (100) and provide insights into how such mechanisms may contribute toward large length- and time-scale surface phenomena. Further, we show that some of the commonly used interatomic potentials fail to accurately capture the details of adatom diffusion on Al (100).