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C Rascón

Publications and source records attributed to C Rascón.

10 recordsLinked to original sources
PubMed2006

Signatures of non locality for short-ranged wetting at curved substrates.

The binding potential for wetting near planes, spheres, and cylinders in systems with short-ranged forces is shown to have a universal geometrical structure. This arises from the nonlocal nature of the interfacial interactions and is exactly described by a recently proposed binding potential functional, which provides a systematic framework for studying wetting at arbitrarily shaped substrates. The corrections to the equilibrium wetting layer thickness induced by nonlocality are comparable to those arising from a Tolman length and lead to diverging terms in the total mass adsorption.

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PubMed2005

Extended wedge covariance for wetting and filling transitions.

Fluid adsorption on nonplanar and heterogeneous substrates is studied using a simple interfacial model. For systems with short-ranged forces, we find that, by tuning the local strength of the substrate potential, it is possible to find the exact equilibrium interfacial profile as a functional of the wall shape psi x. The tuning of the local substrate potential takes the form of a gauge condition theta x=+/-psi x, where theta x can be interpreted as a local effective contact angle. For wedgelike geometries with asymptotic tilt angle alpha, the midpoint interfacial height and roughness satisfy the same covariance relations previously found for simple linear wedges. For troughlike geometries satisfying the gauge condition, covariance is also found for the two-point correlation function. Predictions for more microscopic Landau and Ising models are also discussed.

Journal Article↗
PubMed2005

Covariance for cone and wedge complete filling.

Interfacial phenomena associated with fluid adsorption in two dimensional systems have recently been shown to exhibit hidden symmetries, or covariances, which precisely relate local adsorption properties in different confining geometries. We show that covariance also occurs in three-dimensional systems and is likely to be verifiable experimentally and in Ising model simulations studies. Specifically, we study complete wetting in wedge (W) and cone (C) geometries as bulk coexistence is approached and show that the equilibrium midpoint heights satisfy l(c)(h,alpha)=l(w)(h / 2,alpha), where h measures the partial pressure and alpha is the tilt angle. This covariance is valid for both short-ranged and long-ranged intermolecular forces and identifies both leading and next-to-leading-order critical exponents and amplitudes in the confining geometries.

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PubMed2000

Local functional models of critical correlations in thin films.

Recent work on local functional theories of critical inhomogeneous fluids and Ising-like magnets has shown them to be a potentially exact, or near exact, description of universal finite-size effects associated with the excess free energy and scaling of one-point functions in critical thin films. This approach is extended to predict the two-point correlation function G in critical thin films with symmetric surface fields in arbitrary dimension d. In d = 2 we show there is exact agreement with the predictions of conformal invariance for the complete spectrum of correlation lengths xi((n)) as well as the detailed position dependence of the asymptotic decay of G. In d = 3 and d>/=4 we present new numerical predictions for the universal finite-size correlation length and scaling functions determining the structure of G across the thin film. Highly accurate analytical closed form expressions for these universal properties are derived in arbitrary dimension.

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PubMed2000

Geometry-dominated fluid adsorption on sculpted solid substrates.

The shape and chemical composition of solid surfaces can be controlled at a mesoscopic scale. Exposing such structured substrates to a gas that is close to coexistence with its liquid phase can produce quite distinct adsorption characteristics compared to those of planar systems, which may be important for technologies such as super-repellent surfaces or micro-fluidics. Recent studies have concentrated on the adsorption of liquids on rough and heterogeneous substrates, and the characterization of nanoscopic liquid films. But the fundamental effect of geometry on the adsorption of a fluid from the gas phase has hardly been addressed. Here we present a simple theoretical model which shows that varying the shape of the substrate can exert a profound influence on the adsorption isotherms of liquids. The model smoothly connects wetting and capillary condensation through a number of examples of fluid interfacial phenomena, and opens the possibility of tailoring the adsorption properties of solid substrates by sculpting their surface shape.

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PubMed1999

Wetting at nonplanar substrates: unbending and unbinding.

We consider fluid wetting on a corrugated substrate using effective interfacial Hamiltonian theory and show that breaking the translational invariance along the wall can induce an unbending phase transition in addition to unbinding. Both first-order and second-order unbending transitions can occur at and out of coexistence. Results for systems with short-ranged and long-ranged forces establish that the unbending critical point is characterized by hyperuniversal scaling behavior. We show that, at bulk coexistence, the adsorption at the unbending critical point is a universal multiple of the adsorption for the correspondent planar system.

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