Role of lateral interactions in adsorption kinetics: CO/Rh{100}

The coverage-dependent heats of adsorption and sticking probabilities for C O on Rh{100} were measured. The initial heat is 118 +/- 4 kJ mol(-1), with an initial sticking probability of similar to 0.87; the saturation coverage is similar to 0.8 monolayer: By means of a Kisliuk fit to the sticking pro bability data, the transition between the two main adsorbate phases (c(2 x 2) structure at 0.5 monolayer and p(4 root 2x root 2)R45 degrees structure at 0.75 monolayer) could be detected, allowing the determination of two ind ependent Kisliuk parameters for the first (K = 0.3) and second (K = 1) regi me; The differential heat data was successfully reproduced by means of a Mo nte Carlo simulation. A discrete CO-CO interaction potential was implemente d and optimized, giving CO-CO interaction energies of E-nn = 9 +/- 1 kJ mol (-1) (nearest neighbor), E-nnn = 1 +/- 0.5 kJ mol(-1) (next-nearest neighbo r) and E-nnnn = -1 +/- 0.5 kJ mol(-1) (next-next-nearest neighbor). These e nergies agree well with the experimentally determined vm and nnn interactio n energies and with a calculated CO-CO interaction potential (DFT) for CO o n Pt{111}.