Density profiles of Ar adsorbed in slits of CO(2): Spontaneous symmetry breaking revisited

Laboratorio TANDAR, Departamento de Física, Comisión Nacional de Energía Atómica, Av. del Libertador 8250, RA-1429 Buenos Aires, Argentina.
The Journal of Chemical Physics (Impact Factor: 2.95). 04/2008; 128(12):124702. DOI: 10.1063/1.2895747
Source: PubMed


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.

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Available from: Leszek Szybisz, May 18, 2015
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    • "The symmetric solutions account for a complete (two wall) wetting . These different situations can be interpreted in terms of the balance of γ sl , γ sv and γ lv surface tensions, carefully discussed in previous works [2] [3] [7]. Here we shall restrict ourselves to briefly outline the main features. "
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    ABSTRACT: The adsorption of Ar on substrates of Li is investigated within the framework of a density functional theory which includes an effective pair potential recently proposed. This approach yields good results for the surface tension of the liquid-vapor interface. The behavior of the adsorbate in the cases of a single planar wall and a slit geometry is analyzed as a function of temperature. Asymmetric density profiles are found for fluid confined in a slit built up of two identical planar walls leading to the spontaneous symmetry breaking (SSB) effect. We found that the asymmetric solutions occur even above the wetting temperature $T_w$ in a range of average densities $ho^*_{ssb1} le ho^*_{av} le ho^*_{ssb2}$, which diminishes with increasing temperatures until its disappearance at the critical prewetting point $T_{m cpw}$. In this way a correlation between the disappearance of the SSB effect and the end of prewetting lines observed in the adsorption on a one-wall planar substrate is established. In addition, it is shown that a value for $T_{m cpw}$ can be precisely determined by analyzing the asymmetry coefficients.
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    ABSTRACT: The phenomenon of symmetry breaking (SB) of the fluid density distribution in a slit between parallel identical solid walls examined previously for a classical fluid (argon) [G. O. Berim and E. Ruckenstein, J. Chem. Phys. 126, 124503 (2007)] is examined for a quantum fluid ((4)He) on the basis of a nonlocal density functional theory. The Lennard-Jones potential was employed for the fluid-fluid and fluid-solid interactions. Regarding the latter interaction potential, it was supposed that each wall generates a hard core repulsion at some distance h(r) from the wall. In addition, the Chizmeshya-Cole-Zaremba (CCZ) potential was considered for the fluid-solid interactions. SB was found at all considered temperatures (0 K < or = T < or = 3.0 K) in ranges of average densities of the fluid which decreased, as for classical fluids, with increasing temperature. It was concluded that the existence of SB does not depend on the value of the parameter h(r), whereas, for classical fluids, SB did not occur when h(r) became smaller than a critical value, h(r,c). For the CCZ potential, the asymmetric (symmetry breaking) density profile can be metastable, whereas for the Lennard-Jones potential when an asymmetric density profile occurred it was always stable (had a smaller free energy than the symmetric profile). No effect of the (4)He transition from nonsuperfluid to superfluid state was detected.
    The Journal of Chemical Physics 11/2009; 131(18):184707. DOI:10.1063/1.3259563 · 2.95 Impact Factor
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