Density profiles of Ar adsorbed in slits of CO_2: spontaneous symmetry breaking

A recently reported symmetry breaking of density profiles of fluid argon confined by two parallel solid walls of carbon dioxide is studied. The calculations are performed in the framework of a nonlocal density functional theory. It is shown that the existence of such asymmetrical solutions is restricted to a special choice for the adsorption potential, where the attraction of the solid-fluid interaction is reduced by the introduction of a hard-wall repulsion. The behavior as a function of the slit's width is also discussed. All the results are placed in the context of the current knowledge on this matter.Comment: Text plus 8 figure

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Full correspondence between asymmetric filling of slits and first-order phase transition lines

Adsorption on single planar walls and filling of slits with identical planar walls are investigated in the frame of the density functional theory. In this sort of slits the external potential is symmetric with respect to its central plane. Calculations were carried out by applying both the canonical and grand canonical ensembles (CE and GCE, respectively). The behavior is analyzed by varying the strength of the adsorbate-substrate attraction, the temperature T, and the coverage Γℓ. Results obtained for physisorption of Xe on alkaline surfaces are reported in the present work. Prewetting (PW) lines and wetting temperatures, Tw, are determined from the analysis of adsorption on single walls. The filling of slits is analyzed for temperatures T > Tw. It is found that whenever for a given Xe-substrate combination the adsorption on a single wall exhibits a first-order wetting transition then asymmetric profiles that break the left-right symmetry of the external potential appear in the filling of an equivalent slit. These spontaneously symmetry breaking (SSB) solutions occur in a restricted range of Γℓ with a T-dependent width. In the case of closed slits analyzed in the CE scheme, the obtained asymmetric profiles exhibit lower Helmholtz free energies than the symmetric species and, therefore, could be stabilized in this geometry. For open slits, the GCE scheme yields all the symmetric and SSB states in the corresponding convex regimes of the free energy. It is shown that both the CE and the GCE frames yield three coexistent states, two symmetric and one asymmetric twofold degenerate. Both a PW line and the related SSB effect terminate at the same temperature. For rather strongly attractive surfaces reentrant SSB states are found at a fixed value of T

Adsorption of Ne on a planar solid Mg surface revisited

In this study, we reexamined the wetting behavior of Ne adsorbed on a solid Mg surface. In a recent study, Zhou and Zhang (J. Phys. Chem. Solids, 2017, 103, 123) reported an investigation of this system. They proposed an adsorption potential, ϕ ext (z), and studied this system based on augmented density functional theory (DFT) to determine the wetting temperature T w and critical prewetting temperature T cpw . The value obtained for T cpw differed greatly from that produced by Grand Canonical Monte Carlo simulations (Phys. Rev. E, 1999, 59, 864) and previous DFT calculations (Phys. Rev. E, 2009, 79, 011603). In the present study, we calculated the adsorption isotherms with the Kierlik–Rosinberg DFT for two different external potentials, i.e., the aforementioned ϕ ext (z) and the proposed ab initio Chizmeshya–Cole–Zaremba (CCZ) potential. This study had two main aims. First, we aimed to identify the main sources of the discrepancies between the results obtained by Zhou and Zhang and those produced in other studies. Second, we analyzed the new data computed with the CCZ potential by applying the so-called arc-length continuation method. The new results supported the old ones, yielding more accurate values for both characteristic temperatures and indicating interesting new features of the system. We developed a novel alternative procedure for determining an appropriate value of T cpw for moderately strong adsorbers. Assuming that Ne is liquid in the range of T w ≤ T < Tt, then the DFT calculations were extended into this region. We showed that close to Tt and after the prewetting jump, the growth of the films exhibited a sequence of layering transitions, which originated coalescent prewetting lines.Fil: Szybisz, Leszek. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; ArgentinaFil: Sartarelli, Salvador A.. Universidad Nacional de General Sarmiento. Instituto del Desarrollo Humano; ArgentinaFil: Urrutia, Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentin

Density profiles of Ar adsorbed in slits of CO2: Spontaneous symmetry breaking revisited

A recently reported symmetry breaking of density profiles of fluid argon confined by two parallel solid walls of carbon dioxide is studied. The calculations are performed in the framework of a nonlocal density functional theory. It is shown that the existence of such asymmetrical solutions is restricted to a special choice for the adsorption potential, where the attraction of the solid-fluid interaction is reduced by the introduction of a hard-wall repulsion. The behavior as a function of the slit's width is also discussed. All the results are placed in the context of the current knowledge on this matter. © 2008 American Institute of Physics.Fil:Szybisz, L. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Sartarelli, S.A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina