Oxygen-induced surface(2×2)p4greconstruction of Rh(001)

The room-temperature oxygen-induced $(2\mathrm{}\times 2)p4g$ clock reconstruction of Rh(001) has been investigated by low-energy alkali ion scattering, recoiling spectrometry, low-energy electron diffraction (LEED), and three-dimensional classical scattering simulations. The oxygen atoms are confirmed to be in the fourfold hollow sites to produce the glide plane symmetry of the substrate observed in the LEED pattern. Quantitative values for the geometrical parameters were obtained by using a reliability $R$-factor analysis to compare the experimental and simulated azimuthal scans. The lateral clockwise-counterclockwise displacement of the surface rhodium atoms is $\Delta x=0.2\mathrm{}\pm 0.1$ Å and the oxygen height above the substrate is $\Delta h=0.6\mathrm{}\pm 0.1$ Å. The driving force for this clock reconstruction is discussed and compared with previous results on the $\mathrm{Ni}\mathrm{}\left(001\right)-(2\mathrm{}\times 2)p4g-\mathrm{C}$ surface.