Energetic topography

The results suggest a method to solve the problem of the characterization of the energetic topography of heterogeneous substrates which can be approximated by bivariate... 

Bulnes F., Ramirez-Pastor A.J. and Zgrablich G., Scaling Behavior in Adsorption on Bivariate Surfaces and the Determination of Energetic Topography. J. Chem. Phys. 115 (2001) 1513 Power Laws in Adsorption and the Characterization of Heterogeneous Substrates. Adsorption Sci. and Tech. 19 (2001) 229 Scaling Laws in Adsorption on Bivariate Surfaces Pf s. Rev. E, 65 (2002) 31603. 

It is then of great importance to develop simple models capable of describing the energetic topography on the basis of a few parameters and to study the effects of these parameters on several surface processes, with the hope that, in such a process, methods to obtain the relevant parameters from experimental data will be envisaged. These models can be of two kinds continuum models or lattice-gas models. The former are more suited to mobile adsorption, generally physisorption, and then more closely related to the surface energetic characterization problem, whereas the latter are more suited to locaHzed adsorption (e.g., chemisorption). 

In order to study how the first few virial coefficients depend on the energetic topography, we assume an interparticle interaction given by a LJ potential ... 

These findings provide for the first time a method to characterize the energetic topography (i.e., obtain the parameters from experimental measurements) of a class of heterogeneous surfaces that can be approximately represented as bivariate surfaces. 

Bulnes, F., Pereyra, V., Bdccardo, J.L., and Zgrablich, G. (1999). Effects of the heterogeneous energetic topography on the collective motion of adsorbed particles. J. Chem. Phys., Ill, 1. 

Gargiulo, V., Sales, J.L., Ciacera, M., and Zgrabhch, G. (2002). Characterization of energetic topography of heterogeneous surfaces through the analysis of thermal desorption spectra. Surf. Sci., 501, 282. 

Nazzarro, M. and Zgrablich, G. (2003). Energetic topography effects on mobile adsorption on heterogeneous surfaces at low coverage. Langmuir, 19, 6737. 

A considerable element of the model is the assumption connected with the possibility of the kinetic motion of adsorbed molecules. When the motion of molecules in the z direction is restricted but molecules are able to move freely in the (x,y) plane, the process is classified as mobile adsorption. However, if the lateral translation is also hindered, the process is classified as localized adsorption. The motion of admolecules is controlled by the energetic topography of the surface, molecular interactions, and thermal energies. The adsorbed molecule is considered as localized on a surface when it is held at the bottom of a potential well with a depth that is much greater than its thermal energy. Except for extreme cases, adsorption is neither frilly localized nor frilly mobile and can be termed partially mobile [8]. Because temperature strongly affects the behavior of the system, adsorption may be localized at low temperatures and become mobile at high temperatures. 

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