  The theory of statistical-mechanical lattice-gas modeling of adsorption is
reviewed and shown to be applicable to a range of electrochemical problems
dominated by effective, lateral adsorbate--adsorbate interactions. A general
strategy for applying the method to specific systems is outlined, which
includes microscopic model formulation, calculation of zero-temperature phase
diagrams, numerical calculation of thermodynamical and structural quantities at
nonzero temperatures, and estimation of effective, lateral interaction energies
that cannot be obtained by first-principles methods. Phenomena that are
discussed include poisoning and enhanced adsorption, and illustrative
applications to specific systems are reviewed. Particular problems considered
are: the poisoning by sulfur of hydrogen adsorption on platinum (111), the
electrochemical adsorption of naphthalene on polycrystalline copper and of urea
on single-crystal platinum (100), and the underpotential deposition of copper
on single-crystal gold (111).
