The relation between the strain-dependence of the heat of adsorption and the coverage dependence of the adsorbate induced surface stress

A Maxwell-relation exists between the strain dependence of the chemical potential of an adsorbate and the coverage dependence of the surface stress induced by the same adsorbate. To a good approximation the strain dependence of the chemical potential is equal to the strain dependence of the heat of adsorption. Recent studies on the heat of adsorption of CO on strained Pt(1 1 1) films are discussed in this context and the results are compared to the likewise measured CO-induced surface stress on Pt(1 1 1). It is shown, that the variation of the heat of adsorption with strain depends significantly on the coverage with CO. With reference to the available data on adsorbate induced surface stresses general arguments are presented concerning the sign of the shift in the heat of adsorption with strain and on the general trends in the coverage dependence of the effect.