Abstract
The Cu(4 1 0)–O surface, involving a 0.5 monolayer (ML) coverage of
oxygen, is known to be extremely stable and a range of Cu(1 0 0) vicinal
surfaces facet to (4 1 0) in the presence of adsorbed oxygen. A new surface
X-ray diffraction investigation of this surface has been conducted to determine
its structure, and the detailed structural parameter values obtained are
compared with the results of a density functional theory (DFT) calculation.
The results show that the metal structure is unreconstructed, with the
oxygen forming an overlayer with 0.25 ML O atoms at near-colinear step-edge
sites and 0.25 ML O atoms at mid-terrace hollow sites, approximately 0.6
Å above the terraces. The large number of independent structural
parameters potentially relevant to this vicinal surface presents a significant
challenge for unique structural optimisation, but various missing row reconstruction
models can be clearly excluded. Two detailed structural solutions are identified
which give equally acceptable fits to the X-ray diffraction data after
imposition of a Lennard-Jones penalty factor. These models differ especially
in the O positions, but one is found to be more favoured by comparison
with the results of the DFT calculations, and by considerations based on
bond lengths and valence. Substantial relaxations from the bulk metal positions
occur for the outermost Cu atoms; the ability of the vicinal surface to
relax in this way may help to account for its stability compared with the
missing row reconstruction induced by oxygen chemisorption on the Cu(1
0 0) surface.