Dual site-bond description of heterogeneous surfaces

A dual description based on ``sites'' and ``bonds'' is developed for characterization of the adsorptive energy of a heterogeneous surface, and it is shown how to use the description in order to study the adsorption and the surface diffusion of gases. The joint site-bond energy distribution is determined through a correlation function in such a way as to allow for the maximum degree of randomness in the network permitted by the ``construction principle.'' This function contains valuable information about the topology of the energy surface and strongly affects adsorption isotherms and surface diffusion coefficients.