Adiabatic potential-energy surface of O2/Al(111): rare entrance-channel barriers but molecularly chemisorbed state apt for abstraction

Extensive density-functional calculations of the adiabatic potential-energy hypersurface for O2 adsorption on the Al(111) surface present (i) an entrance-channel barrier only under some very rare conditions and (ii) a molecularly chemisorbed intermediate state for a non-parallel molecule. The predicted metastable molecular state is stabilized by a Hundʹs rule spin effect on the very inequivalent oxygen atoms of the non-parallel O2 in the strong Al-surface field. It provides a source for abstraction, i.e. dissociative decay by emission of one oxygen atom.