Lattice-gas model of nonadditive interacting particles on nanotube bundles

Abstract

In the present paper, the adsorption thermodynamics of a lattice-gas model which mimics a nanoporous environment is studied by considering nonadditive interactions between the adsorbed particles. It is assumed that the energy linking a certain atom with any of its nearest neighbors strongly depends on the state of occupancy in the first coordination sphere of such an adatom. By means of Monte Carlo (MC) simulations in the grand canonical ensemble, adsorption isotherms and differential heats of adsorption were calculated. Their striking behaviors were analyzed and discussed in terms of the low temperature phases formed in the system. Finally, the results obtained from MC simulations were compared with the corresponding ones from Bragg-Williams approximation.

Statistical thermodynamics of straight rigid rods with nonadditive lateral interactions: Theory and Monte Carlo simulations

“…These discontinuities correspond to first-order phase transitions between surface phases at low and high densities. This phenomenon, which has also been reported in the adsorption of nonadditive monomers [39][40][41], can be explained by considering W m (P ) as it is shown in the upper-left inset of the figure. For P > 1 (and W > 0), W 6 < W i (i = 1,2,3,4,5) and the system prefers to condensate in such a way that each adsorbed dimer possesses six nearest-neighbor occupied sites in contrast with a sequential adsorption increasing the number of nearest-neighbor occupied sites upon raising the chemical potential, as occurs for P < 1.…”

“…From a theoretical point of view, the consequences of considering nonadditive interactions in the adsorption thermodynamics have been studied for a long time. In fact, statistical mechanics of adsorbed monolayers has been the subject of analytical treatment by means of the Bragg-Williams approximation (BWA) [35][36][37], the quasichemical approximation (QCA) [38], and Monte Carlo simulations [39][40][41]. In all cases, one fundamental feature is preserved.…”

The adsorption of a mixture of particles with non-additive interactions: a Monte Carlo study

“…However, the case of repulsive interactions is also of interest mainly because (a) experimental phase diagrams corresponding to many systems in the presence of surface restructuring are explained in terms of those interactions; 45-47 (b) the tendency to dimer formation, which seems to be relevant in several systems mentioned above, can be predicted on the basis of such kind of coupling; and (c) a rich variety of non-symmetrical phase diagrams (around half coverage) can be described. Some efforts in this direction include the study of adsorption of monomers [34][35]48 and linear k-mers 49 with repulsive non-additive lateral interactions on substrates of different connectivity.…”

“…Similar results have been found in adsorption studies on nanotube bundles. 48 In this context, the main aim of this manuscript is to extend earlier work on adsorption with non-additive interactions to include more than one adsorbed species. The present paper is a natural extension of previous studies in which non-additive interactions have been included in the context of the lattice theory.…”

“…The present paper is a natural extension of previous studies in which non-additive interactions have been included in the context of the lattice theory. [31][32][33][34][35]48,49 The observed occupation by adsorbed particles of preferred sites of a lattice, commensurate with the substrate surface, is a justification for the use of the lattice theory. 33 It is clear that a complete analysis of this field is a quiet difficult subject.…”