TRENDS IN LATERAL INTERACTIONS BETWEEN CO CHEMISORBED ON LOW-INDEX COPPER SURFACES

We present a transfer matrix analysis of existing coverage-dependent d esorption data for CO adsorbed onto Cu(001), (011), and (111). We dete rmine the ranges of the second and third lattice gas interaction energ ies which are consistent with these data. A systematic trend is observ ed in the attractive component of the lateral potential: it is substan tial for the loosely packed (011) surface, it is very small for the (0 01) surface, and it is nonexistent for the close-packed (111) surface. We hypothesize that this trend is associated with the way in which su rface tensile stress can be relieved upon chemisorption of neighboring molecules. We discuss the relation between our desorption results and previous adsorption isotherm measurements for CO/Cu(001).