6533b7d1fe1ef96bd125d571

RESEARCH PRODUCT

On the mechanism of the interaction between oxygen and close-packed single-crystal aluminum surfaces

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Abstract Using periodic first principles simulations we investigate the interaction of oxygen molecules with both regular Al(111) and Al(001) surfaces as well as a stepped Al(111) substrate. The limitation of this approach is the use of thin metallic slabs with a limited range for their coverage by adsorbed oxygen. The advantage is the detailed modeling that is possible at an atomic level. On the regular Al(111) surface, we have been able to follow the oxidation process from the approach of O 2 molecules to the surface, through the chemisorption and absorption of O atoms, up to the formation of first Al 2 O 3 formula units. An energetically feasible mechanism for the formation of these Al 2 O 3 ‘molecules’ is proposed but their aggregation to Al 2 O 3 growth nuclei can only be surmised. On the Al(001) surface, absorption of oxygen atoms occurs more readily without any restrictions on the density of their surface overlayer, in agreement with the failure to observe a distinct chemisorption stage for O on Al(001) experimentally. The stepped Al(111) surface contains both {111} and {001} microfacets: the latter are obviously preferred for penetration of the oxygen adatoms into the subsurface space of the substrate. Before considering the O/Al interfaces the computational method is tested thoroughly by simulations on bulk Al and close-packed aluminum surfaces.