Stress in densely packed adsorbate layers and stress at the solid-liquid interface - is the stress due to repulsive interactions between the adsorbedspecies?

The contribution of repulsive interactions between adsorbed molecules to th e surface stress is explored using a uniform compression model. The model p redicts relations between the surface stress, the surface coverage and the chemical potential of the gas phase which are tested with the help of exper imental data on the surface stress for CO on Ni(100) in the high coverage r egime. It is shown that the data are inconsistent with the assumption that the measured stress is due to repulsive interactions. The experimental data can be accounted for by assuming that the stress is caused by a modificati on of the electronic structure of the surface linear in the CO-coverage. Ex perimental data on the interface stress of Au(111) and Au(100) electrodes i n 0.1 M HClO4 as a function of the electrode potential are analyzed. For Au (111) the stress is a linear function of the interface charge for potential s E-SCE between -0.2 and +0.5 V, consistent with earlier reports. For Au(10 0), however, the dependence of the interface stress on the charge is non-li near. For higher anodic potentials, corresponding to a higher density of ad sorbed anions, the stress depends linear on the potential. It is argued tha t the stress at the solid-liquid interface is likewise due to an electronic effect and not caused by repulsive interactions. (C) 1999 Elsevier Science Ltd. All rights reserved.