Full structure determination of an alkali-metal/CO coadsorption phase for Co{101¯0}-<i>c</i>(2×2)-(K+CO)

Abstract

A structural analysis of a c(2\ifmmode\times\else\texttimes\fi{}2)-(K+CO) coadsorption phase on Co{101\ifmmode\bar\else\textasciimacron\fi{}0} by low-energy electron diffraction has yielded a full picture of the geometry of a model alkali-metal CO coadsorption system. Potassium atoms are located in fourfold hollow sites above second-layer Co atoms, and CO molecules are displaced by 0.5\ifmmode\pm\else\textpm\fi{}0.2 \AA{} from the high-symmetry Co short bridge sites near the center of gravity of the three neighboring K adatoms. The CO causes a substantial increase, by 0.4 \AA{}, in the K-Co nearest-neighbor bond length, and K adatoms are located with their centers above the O atoms in the neighboring CO. This has important implications for the bonding interactions within the adlayer.