Low-Symmetry Diffusion Barriers in Homoepitaxial Growth of Al(111)

From fractals to compact islands, epitaxial growth offers an exotic variety of surface morphologies that emanate from a handful of elementary atomic diffusion processes. Adsorption calculations have hitherto been limited to high-symmetry configurations, or to semiquantitative methods. Using extensive density-functional calculations on parallel computers we map out barriers for self-diffusion at steps, kinks, and corners on Al(111). The results reveal an unexpected exchange diffusion mechanism at kinks and a large anisotropy at corners, and are used to predict various growth modes.