  We present chronocoulometry experiments and equilibrium Monte Carlo
simulations for the electrosorption of Br and Cl on Ag(100) single-crystal
electrode surfaces. Two different methods are used to calculate the long-range
part of the adsorbate-adsorbate interactions. The first method is a
truncated-sum approach, while the second is a mean-field-enhanced truncated-sum
approach. To compare the two methods, the resulting isotherms are fit to
experimental adsorption isotherms, assuming both a constant electrosorption
valency &gamma and also a coverage-dependent &gamma. While a constant &gamma
fits the Br/Ag(100) well, a coverage-dependent or potential-dependent &gamma is
needed for Cl/Ag(100).
