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J. Phys. Chem. C 2007, 111, 8136
Reply to “Comment on ‘The Origin of Surface Stress Induced by Adsorption of Iodine on Gold’” Vincent S. J. Craig and Drew R. Evans Department of Applied Mathematics, Research School of Physical Sciences and Engineering, Australian National UniVersity, Canberra Australian Capital Territory 0200, Australia ReceiVed: April 12, 2007 The theoretical calculations of Wang1 and others that address the lateral potential between halide ions adsorbed to a gold surface were not known to us at the time of publication, and they indeed appear not to be known to other experimentalists in this area. It is apparent that the adatom-adatom interaction for halide atoms adsorbed to gold is repulsive whereas we had assumed it would be attractive. Therefore, we accept that our simple model for the origin of the film stress is incorrect, and the good agreement found with the measured film stress must be due to coincidence. So how does the measured film stress compare to the theoretical calculations of Wang? The calculated surface pressure at complete surface coverage is 5.51 × 10-2
eV‚Å-2 or 0.887 N‚m-1. In comparison, the measured film stress we reported was 0.75 ( 0.08 N‚m-1. The agreement is reasonable, but the value of the theoretical surface pressure predicted by Wang is higher than that found experimentally. We believe this may be explained by the nature of the surface employed in our study. Gold typically has a root mean square (rms) surface roughness of ∼3 nm, and the crystalline nature of the surface is not known, although the calculation is made for gold (111). We note that the substrate-mediated interaction dominates the lateral interaction energy and that the calculation of this component is achieved by using an empirical expression, and therefore, the theoretical calculation of the lateral pressure may have a significant error. Wang has also calculated the surface pressure for bromide and chloride systems, which are amenable to future experimental investigation. We thank Tkatchenko for highlighting the work of Wang and others and for making it clear that our simple theoretical model for describing the film stress proposed in section 5.3.1. of our manuscript is invalid. References and Notes (1) Wang, X.; Chen, R.; Wang, Y.; He, T.; Liu, F.-C. J. Phys. Chem. B 1998, 102, 7568-7576.
10.1021/jp072844b CCC: $37.00 © 2007 American Chemical Society Published on Web 05/12/2007
