Determination of a (2√2×√2)R45° structure formed by coadsorption of Li and Mg on a Cu(0 0 1) surface

The coadsorption of Li and Mg on Cu(0 0 1) at room temperature was studied by low-energy electron diffraction (LEED). A (2√2×√2)R45° structure was observed and determined by a tensor LEED analysis. It is an ordered mixed phase, in which Mg atoms are located on fourfold substitutional sites, while Li atoms occupy surface hollow sites, instead of the separation into c(2×2)-Mg and (2×1)-Li phases formed in the individual adsorption. The (2√2×√2)R45° structure is comprised of alternative atomic-rows of substitutional Mg atoms and hollow-site Li atoms aligned along the [0 1 0] direction. The stability of this structure is discussed in terms of adsorption energy of Li and Mg atoms and the displacement of surface Cu atoms.