Interactions between Al atoms on Al(110) from first-principles calculations

Abstract

We quantified pair and trio interactions between Al adatoms on the Al(110) surface using first-principles, density-functional theory, total-energy calculations. We find that the pair interaction is the strongest for the nearest in-channel $[1\overline{1}0]$ neighbor and is attractive due to the formation of direct chemical bonds between the adatoms. Beyond the nearest neighbor, the pair interaction is repulsive and is mediated by elastic distortion of the substrate atoms. The pair interaction is negligible for adatom separations beyond $\ensuremath{\sim}8.00\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$. Interactions between atoms in a collinear trio chain along the in-channel $[1\overline{1}0]$ direction have both electronic and elastic characters. All other trio interactions are elastic in origin. The long-ranged trio interaction is significant and exhibits damped oscillations between attraction and repulsion. We find several trios that enhance cross-channel [001] attraction. This trio attraction facilitates the formation of two-dimensional islands in Al(110) homoepitaxy, which are not favored by repulsive cross-channel pair interactions. These observations demand a refined approach to study thin-film growth, in which many-body interactions are taken into account.