Determination of the energetic topography of bivariate heterogeneous surfaces from adsorption isotherms
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Determination of the energetic topography of bivariate heterogeneous surfaces from adsorption isotherms P.M. Centres · F. Bulnes · G. Zgrablich · A.J. Ramirez-Pastor
Received: 28 April 2010 / Accepted: 16 February 2011 / Published online: 1 March 2011 © Springer Science+Business Media, LLC 2011
Abstract The reversible adsorption process occurring on patchwise heterogeneous bivariate surfaces is studied by Monte Carlo simulation and mean-field approximation. These surfaces are characterized by a collection of deep and shallow adsorbing patches with a typical length scale l. Patches can be either arranged in a deterministic chessboard structure or in a random way. Previous studies showed that the topography of a given surface can be obtained from the knowledge of the corresponding adsorption isotherm and a reference curve. In the present work, we discuss the advantages and disadvantages of using different reference curves. One of the main consequences of this analysis is to provide an improved method for the determination of the energetic topography of the surface from adsorption measurements. Keywords Lattice-gas models · Adsorption thermodynamics · Heterogeneous surfaces · Monte Carlo simulations
1 Introduction The adsorption of gases on solid surfaces is a topic of fundamental interest for various applications (Tóth 2002; Keller and Staudt 2005). Most materials possess complex heterogeneous surface where elementary surface processes such as adsorption, desorption, surface diffusion, and surface reactions are strongly affected by structural and/or energetic disorder (Ross and Olivier 1964; Rudzinski et al. 1997; P.M. Centres · F. Bulnes · G. Zgrablich · A.J. Ramirez-Pastor () Departamento de Física, Instituto de Física Aplicada, Universidad Nacional de San Luis-CONICET, Chacabuco 917, 5700 San Luis, Argentina e-mail: [email protected]
Jaroniec and Madey 1988; Rudzinski and Everett 1992). It is well known that, in addition to the adsorption energy distribution function, the surface topography is also a very important factor in those processes. The patchwise heterogeneous surface, introduced by Ross and Olivier (1964), and the random heterogeneous surface are two examples of disordered surfaces with different topographies, which have been extensively used in the analysis of surface processes (Rudzinski et al. 1997). When correlation between the energies of the adsorption sites is present, the appropriate description of the heterogeneous surface is through the use of an intermediate adsorption site topography (Ross and Olivier 1964; Ripa and Zgrablich 1975; Riccardo et al. 1992, 1993; Ramirez-Pastor et al. 1995, 2000). The adsorption of gases has been used to obtain information about the energetic characteristics of heterogeneous surfaces as well as the adsorption energy distribution (Steele 1974; Ross and Olivier 1964; Rudzinski et al. 1997; Jaroniec and Madey 1988; Rudzinski and Everett 1992; House 1983; Jaroniec and Braüer 1986; Sircar and Myers 1988; Mamleev and Bekturov 1996a, 1996b). In this sense, a metho
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