  We formulate the theory of the perturbation caused by an adsorbate upon the
substrate lattice in terms of a local modification of the interatomic potential
energy around the adsorption site, which leads to the relaxation of substrate
atoms. We apply the approach to CO chemisorption on close-packed metal
surfaces, and show that the adsorbate-adsorbate interaction and a variety of
other properties can be well described by a simple model.
