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Journal ArticleDOI

Effect of the fluid-wall interaction on freezing of confined fluids: Toward the development of a global phase diagram

14 Jun 2000-Journal of Chemical Physics (American Institute of PhysicsAIP)-Vol. 112, Iss: 24, pp 11048-11057
TL;DR: In this article, the effect of the fluid-wall interaction energy on the shift of the freezing temperature and on the fluid structure is considered, using a novel approach to calculate the free energy surface based on Landau theory and order parameter formulation.
Abstract: We report molecular simulation studies of the freezing behavior of fluids in nano-porous media. The effect of confinement is to induce spatial constraints as well as energetic heterogeneity on the confined fluid, thereby altering the bulk phase behavior drastically. We consider the effect of the fluid-wall interaction energy on the shift of the freezing temperature and on the fluid structure, using a novel approach to calculate the free energy surface based on Landau theory and order parameter formulation. Corresponding states theory is then used to map out the global freezing behavior of a Lennard-Jones (LJ) fluid in model slit-shaped pores of varying fluid-wall interaction strengths. Using LJ parameters fitted to thermophysical property behavior, we predict the qualitative freezing behavior for a variety of fluids and nano-porous materials, based on a global freezing diagram. We have attempted to verify these predictions by comparing with experimental data for several systems, and show that in these cases, the experimental observations and the predictions are in agreement.

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Citations
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Journal ArticleDOI
TL;DR: In this paper, both experimental measurements and molecular simulations of the melting and freezing behavior of fluids in nanoporous media are reported. But the experimental studies are for nitrobenzene in the silica-based pores of controlled pore glass, Vycor and MCM-41.
Abstract: We report both experimental measurements and molecular simulations of the melting and freezing behavior of fluids in nanoporous media. The experimental studies are for nitrobenzene in the silica-based pores of controlled pore glass, Vycor, and MCM-41. Dielectric relaxation spectroscopy is used to determine melting points and the orientational relaxation times of the nitrobenzene molecules in the bulk and the confined phase. Monte Carlo simulations, together with a bond orientational order parameter method, are used to determine the melting point and fluid structure inside cylindrical pores modeled on silica. Qualitative comparison between experiment and simulation are made for the shift in the freezing temperatures and the structure of confined phases. From both the experiments and the simulations, it is found that the confined fluid freezes into a single crystalline structure for average pore diameters greater than 20σ, where σ is the diameter of the fluid molecule. For average pore sizes between 20σ and...

116 citations

Journal ArticleDOI
TL;DR: In this paper, a series of porous samples has been obtained by using an off-lattice 3D reconstruction method recently introduced to reproduce topological and morphological properties of correlated disordered porous materials such as Vycor.
Abstract: The adsorption of rare gases in a disordered mesoporous silica glass has been studied by means of grand canonical Monte Carlo (GCMC) simulation. A series of porous samples has been obtained by using an off-lattice 3D reconstruction method recently introduced to reproduce topological and morphological properties of correlated disordered porous materials such as Vycor. The off-lattice functional of 115m2g−1 Vycor is applied to a simulation box containing silicon and oxygen atoms of cubic cristoballite with a homothetic reduction in order to obtain porous samples with mean pore size around 35 A and specific surface around 220 m2 g−1. A realistic surface chemistry is then obtained by saturating all the dangling oxygen bonds with hydrogen. Some topological properties of the different 3D reconstructions of the Vycor-like material are analysed using chord length distributions and small angle scattering data. The GCMC Ar, Kr and Xe adsorption/desorption isotherms are calculated at different temperatures. At suffi...

105 citations

Journal ArticleDOI
TL;DR: In this paper, the melting and freezing behavior of nano-porous fluids in controlled pore glass (CPG), Vycor and MCM-41 has been investigated using dielectric relaxation spectroscopy, and it was found that the confined fluid freezes into a single crystalline structure for average pore diameters greater than 20, where is the diameter of the fluid molecule.

103 citations

Journal ArticleDOI
TL;DR: In this paper, a phase of nano-scale dimensions (the adsorbate) is confined within a porous material, and in thermal, chemical and mechanical equilibrium with a bulk phase of fixed temperature, pressure and composition.

102 citations

Journal ArticleDOI
TL;DR: Standard shapematching techniques are reviewed and how they might be used to create highly flexible structural metrics for diverse systems such as self-assembled matter to identify local and global structures and tracking structural transitions in complex assembled systems.
Abstract: Structural quantities such as order parameters and correlation functions are often employed to gain insight into the physical behavior and properties of condensed matter systems. Although standard quantities for characterizing structure exist, often they are insufficient for treating problems in the emerging field of nano- and microscale self-assembly, wherein the structures encountered may be complex and unusual. The computer science field of shape matching offers a robust solution to this problem by defining diverse methods for quantifying the similarity between arbitrarily complex shapes. Most order parameters and correlation functions used in condensed matter apply a specific measure of structural similarity within the context of a broader scheme. By substituting shape matching quantities for traditional quantities, we retain the essence of the broader scheme, but extend its applicability to more complex structures. Here we review some standard shapematching techniques and discuss how they might be used to create highly flexible structural metrics for diverse systems such as self-assembled matter. We provide three proof-of-concept example problems applying shape-matching methods to identifying local and global structures and tracking structural transitions in complex assembled systems. The shape-matching methods reviewed here are applicable to a wide range of condensed matter systems, both simulated and experimental, provided particle positions are known or can be accurately imaged.

79 citations

References
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Book
01 Jan 1954
TL;DR: Molecular theory of gases and liquids as mentioned in this paper, molecular theory of gas and liquids, Molecular theory of liquid and gas, molecular theories of gases, and liquid theory of liquids, مرکز
Abstract: Molecular theory of gases and liquids , Molecular theory of gases and liquids , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

11,807 citations

Book
01 Jan 1995
TL;DR: In this article, the authors present a generalization of the renormalization group of mean field theories, critical phenomena, and topological defects, including walls, kinks and solitons.
Abstract: Preface 1. Overview 2. Structure and scattering 3. Thermodynamics and statistical mechanics 4. Mean-field theory 5. Field theories, critical phenomena, and the renormalization group 6. Generalized elasticity 7. Dynamics: correlation and response 8. Hydrodynamics 9. Topological defects 10. Walls, kinks and solitons Glossary Index.

3,223 citations

Journal ArticleDOI
TL;DR: In this paper, the potential energy of a gas atom interacting with a solid having a surface made up of single type of exposed lattice plane can be expressed as a Fourier series in the position variables in the plane parallel to the surface.

1,379 citations

Journal ArticleDOI
TL;DR: In this paper, the free energy of a Lennard-Jones fluid in the liquid-vapour coexistence region was estimated by relating it to that of the inverse-twelve (soft sphere) fluid, which itself shows no condensation.

1,179 citations