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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TL;DR: It is found that growth and quality of the resulting microstructure also depends on the magnitude of liquid deuterium-wall interaction strength, as the interaction with the confining wall changes from perfect wetting to non-wetting.
Abstract: We have performed a computational study to determine how the wetting of liquid deuterium to the walls of the material influences nucleation. We present the development of a pair-wise interatomic potential that includes zero-point motion of molecular deuterium. Deuterium is used in this study because of its importance to inertial confinement fusion and the potential to generate a superfluid state if the solidification can be suppressed. Our simulations show that wetting dominates undercooling compared to the pore geometries. We observe a transition from heterogeneous nucleation at the confining wall to homogeneous nucleation at the bulk of the liquid (and intermediate cases) as the interaction with the confining wall changes from perfect wetting to non-wetting. When nucleation is heterogeneous, the temperature needed for solidification changes by 4 K with decreasing deuterium-wall interaction, but it remains independent (and equal to the one from bulk samples) when homogeneous nucleation dominates. We find that growth and quality of the resulting microstructure also depends on the magnitude of liquid deuterium-wall interaction strength.
5 citations
01 Jan 2007
TL;DR: A review of the role of molecular simulations in enhancing our understanding of systems ranging from the nanoscale to mesoscale can be found in this paper, where the structure and dynamics of nanoscopically confined films, fluids confined in carbon nanotubes, self assembled monolayers and mesoscales simulations of a variety of complex fluid systems using dissipative particle dynamics, are covered.
Abstract: The review is concerned with the role that molecular simulations have played in enhancing our understanding of systems ranging from the nanoscale to mesoscale. The structure and dynamics of nanoscopically confined films, fluids confined in carbon nanotubes, self assembled monolayers and mesoscale simulations of a variety of complex fluid systems using dissipative particle dynamics, are covered in this review. Molecular simulations have significantly enhanced our understanding of confined fluid behaviour and self assembled monolayers, aiding in the interpretation of experimental findings on these systems. The science of these systems influences our evaluation of interfacial processes such as freezing, adsorption, wetting, adhesion, friction and lubrication, impacting a wide range of technologies ranging from fluid separations, sensors, microelectromechanical (MEMS) devices to nanofluidic systems. The last part of the review concerns the study of mesoscale systems, where length and time scales of the processes are typically greater than those sampled in conventional molecular simulations (1-10 nm, 1-10 ns). The emphasis is on a relatively new technique called dissipative particle dynamics and its potential in studying complex fluid phenomenon, from self assembly in oil-water-surfactant mixtures, polymer structure and rheology to continuum fluid mechanics.
5 citations
TL;DR: It is demonstrated that the reentrant first-order pore filling transition, associated with the condensation of the middle layer, appears only when the height of the potential barrier between adjacent sites, VD, fulfills a condition VD∈[VD,min,VD,max].
Abstract: The reentrant first-order pore filling transition in a Lennard-Jones (LJ) fluid confined between the parallel (100) planes of the face centered cubic (fcc) crystal is studied by means of Monte Carlo simulations in the canonical as well as grand canonical ensembles. Slit-like pores of the width allowing for the formation of only three adsorbate layers are used. It is demonstrated that the reentrant first-order pore filling transition, associated with the condensation of the middle layer, appears only when the height of the potential barrier between adjacent sites, VD, fulfills a condition VD∈[VD,min,VD,max]. The lower limit of VD (VD,min) is primarily determined by the stability of commensurate monolayers formed at both pore walls during the first step of adsorbate condensation, while the upper limit of VD (VD,max) depends on the stability of the commensurate three-layer structure. It is also shown that both the misfit between the size of adsorbed atom and the surface lattice as well as the pore width have a great influence on the phase behavior of confined fluids. Moreover, the effects of the phase shift between the confining lattices on the reentrant first-order filling transition are discussed.
5 citations
Posted Content•
TL;DR: This work demonstrates how shape matching techniques can be applied to identify unknown structures and create highly-specialized order parameters, and investigates the special symmetry properties of harmonic descriptors, and demonstrates how they can be exploited to provide optimal solutions to certain classes of problems.
Abstract: Order parameters based on spherical harmonics and Fourier coefficients already play a significant role in condensed matter research in the context of systems of spherical or point particles Here, we extend these types of order parameter to more complex shapes, such as those encountered in nanoscale self-assembly applications To do so, we build on a powerful set of techniques that originate in the computer science field of "shape matching" We demonstrate how shape matching techniques can be applied to identify unknown structures and create highly-specialized \textit{ad hoc} order parameters Additionally, we investigate the special symmetry properties of harmonic descriptors, and demonstrate how they can be exploited to provide optimal solutions to certain classes of problems Our techniques can be applied to particle systems in general, both simulated and experimental, provided the particle positions are known
4 citations
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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
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01 Jan 1995TL;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
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
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