Characterization of Energetic Surface Heterogeneity by a Dual Site-Bond Model

RICCARDO, J.L.; PEREYRA, V.; ZGRABLICH, G.; ROJAS, F.; MAYAGOITIA, V.; KORNHAUSER, I.

LANGMUIR

AMER CHEMICAL SOC

Año: 1993 vol. 9 p. 2730 - 2736

0743-7463

A dual site-bond model for the description of correlated heterogeneous surfaces is presented. This model assumes the surface as a network of adsorptive “sites” connected by “bonds” (saddle point energies). Site and bond energies are statistically described by their energy distribution functions and the adsorptive energy surface by the joint site-bond energy distribution which is expressed in terms of a correlation function. The latter is determined by allowing the maximum randomness degree admitted by the “construction principle”. This principle states that the potential at an adsorptive site must be deeper than that of any bond connected to that site. Energy correlations naturally arise when site-bond distributions overlap. A topological characterization of these correlations through an energy correlation length is proposed. This correlation length appears as a meaningful physical parameter. A transition between two well-differentiated morphologies of correlated elements upon variation of the overlapping degree of site-bond energy distribution is found. This fact is analyzed in terms of cluster morphology and percolation theory. A simulation procedure to simulate adequately a site-bond heterogeneous surface is developed. © 1993, American Chemical Society. All rights reserved.