The Experts below are selected from a list of 255 Experts worldwide ranked by ideXlab platform
Patrick Charbonneau - One of the best experts on this subject based on the ideXlab platform.
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n pt monte carlo simulations of the cluster crystal forming penetrable Sphere Model
Journal of Chemical Physics, 2012Co-Authors: Kai Zhang, Patrick CharbonneauAbstract:Certain Models with purely repulsive pair interactions can form cluster crystals with multiply-occupied lattice sites. Simulating these Models' equilibrium properties is, however, quite challenging. Here, we develop an expanded isothermal-isobaric [N]pT ensemble that surmounts this problem by allowing both particle number and lattice spacing to fluctuate. It is particularly efficient at high T, where particle insertion is facile. Using this expanded ensemble and thermodynamic integration, we solve the phase diagram of a prototypical cluster-crystal former, the penetrable Sphere Model, and compare the results with earlier theoretical predictions. At high temperatures and densities, the equilibrium occupancy n(c)(eq) of face-centered cubic crystal increases linearly. At low temperatures, although n(c)(eq) plateaus at integer values, the crystal behavior changes continuously with density. The previously ambiguous crossover around T ~ 0.1 is resolved.
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n pt monte carlo simulations of the cluster crystal forming penetrable Sphere Model
arXiv: Soft Condensed Matter, 2012Co-Authors: Kai Zhang, Patrick CharbonneauAbstract:Certain Models with purely repulsive pair interactions can form cluster crystals with multiply-occupied lattice sites. Simulating these Models' equilibrium properties is, however, quite challenging. Here, we develop an expanded isothermal-isobaric $[N]pT$ ensemble that surmounts this problem by allowing both particle number and lattice spacing to fluctuate. We apply the method with a Monte Carlo simulation scheme to solve the phase diagram of a prototypical cluster-crystal former, the penetrable Sphere Model (PSM), and compare the results with earlier theoretical predictions. At high temperatures and densities, the equilibrium occupancy $n_{\mathrm{c}}^{\mathrm{eq}}$ of face-centered cubic (FCC) crystal increases linearly. At low temperatures, although $n_{\mathrm{c}}^{\mathrm{eq}}$ plateaus at integer values, the crystal behavior changes continuously with density. The previously ambiguous crossover around $T\sim0.1$ is resolved.
Jing Fan - One of the best experts on this subject based on the ideXlab platform.
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a generalized soft Sphere Model for monte carlo simulation
Physics of Fluids, 2002Co-Authors: Jing FanAbstract:A new collision Model, called the generalized soft-Sphere (GSS) Model, is introduced. It has the same total cross section as the generalized hard-Sphere Model [Phys. Fluids A 5, 738 (1993)], whereas the deflection angle is calculated by the soft-Sphere scattering Model [Phys. Fluids A 3, 2459 (1991)]. In virtue of a two-term formula given to fit the numerical solutions of the collision integrals for the Lennard-Jones (6-12) potential and for the Stockmayer potential, the parameters involved in the GSS Model are determined explicitly that may fully reproduce the transport coefficients under these potentials. Coefficients of viscosity, self-diffusion and diffusion for both polar and nonpolar molecules given by the GSS Model and experiment are in excellent agreement over a wide range of temperature from low to high.
Zhen-gang Wang - One of the best experts on this subject based on the ideXlab platform.
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Intrinsic Viscosity of Polymers: General Theory Based on a Partially Permeable Sphere Model
Macromolecules, 2013Co-Authors: Zhen-gang WangAbstract:We present a general theory for the intrinsic viscosity of flexible polymers of arbitrary architecture. The theory is based on a partially permeable Sphere Model for which we introduce two phenomenological functions, the drag function ξ and the drainage function κ, that are determined by the density profile of the polymer. At the mean-field level, these functions capture the long-range, multibody, accumulative hydrodynamic interactions, that are responsible for the frictional dissipation in and around a polymer. The density profiles for a diversity of chain architectures are obtained by Monte Carlo simulation. Predictions from our theory are in good agreement with experimental data on all the polymer structures examined, ranging from linear, ring, and stars to hyperbranched and dendrimers. The concepts and methods we introduce in this work should be useful for studying other dilute solution frictional properties, such as the self-diffusivity, and provide a convenient framework for understanding the relationship between the molecular architecture and their dilute solution properties.
Velisa Vesovic - One of the best experts on this subject based on the ideXlab platform.
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Extended hard-Sphere Model for predicting the viscosity of long-chain n-alkanes
Fluid Phase Equilibria, 2016Co-Authors: Nicolas Riesco, Velisa VesovicAbstract:Abstract An extended hard-Sphere Model is presented that can accurately and reliably predict the viscosity of long chain n -alkanes. The method is based on the hard-Sphere Model of Dymond and Assael, that makes use of an universal function relating reduced viscosity to reduced volume. The existing expression for the molar core volume is extrapolated to long chain n -alkanes, while the roughness factor is determined from experimental data. A new correlation for roughness factor is developed that allows the extended Model to reproduce the available experimental viscosity data on long chain n -alkanes up to tetracontane ( n -C 40 H 82 ) within ±5%, at pressure up to 30 MPa. In the dilute gas limit a physically realistic Model, based on Lennard-Jones effective potential, is proposed and used to evaluate the zero-density viscosity of n -alkanes to within ±2.4%, that is better than currently available.
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Extended hard-Sphere Model for the viscosity of dense fluids
Fluid Phase Equilibria, 2014Co-Authors: Fausto Ciotta, J. P. Martin Trusler, Velisa VesovicAbstract:Abstract An extended hard-Sphere Model is reported that may be applied to correlate and predict the viscosity of gases, liquids and supercritical fluids. The method is based on the hard-Sphere Model of Dymond and Assael and uses their roughness factors and molar core volumes to relate reduced viscosity to a universal function of reduced volume. The extended Model behaves correctly in the limit of low densities and offers improved accuracy at high densities. The new universal reference function was determined from a large database of experimental viscosities for alkanes extending up to reduced densities of 0.84. It has been tested by correlating the viscosity of two high-viscosity liquids not used in the development of the universal function and has shown to perform satisfactorily up to reduced densities of approximately 0.9.
Kai Zhang - One of the best experts on this subject based on the ideXlab platform.
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n pt monte carlo simulations of the cluster crystal forming penetrable Sphere Model
Journal of Chemical Physics, 2012Co-Authors: Kai Zhang, Patrick CharbonneauAbstract:Certain Models with purely repulsive pair interactions can form cluster crystals with multiply-occupied lattice sites. Simulating these Models' equilibrium properties is, however, quite challenging. Here, we develop an expanded isothermal-isobaric [N]pT ensemble that surmounts this problem by allowing both particle number and lattice spacing to fluctuate. It is particularly efficient at high T, where particle insertion is facile. Using this expanded ensemble and thermodynamic integration, we solve the phase diagram of a prototypical cluster-crystal former, the penetrable Sphere Model, and compare the results with earlier theoretical predictions. At high temperatures and densities, the equilibrium occupancy n(c)(eq) of face-centered cubic crystal increases linearly. At low temperatures, although n(c)(eq) plateaus at integer values, the crystal behavior changes continuously with density. The previously ambiguous crossover around T ~ 0.1 is resolved.
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n pt monte carlo simulations of the cluster crystal forming penetrable Sphere Model
arXiv: Soft Condensed Matter, 2012Co-Authors: Kai Zhang, Patrick CharbonneauAbstract:Certain Models with purely repulsive pair interactions can form cluster crystals with multiply-occupied lattice sites. Simulating these Models' equilibrium properties is, however, quite challenging. Here, we develop an expanded isothermal-isobaric $[N]pT$ ensemble that surmounts this problem by allowing both particle number and lattice spacing to fluctuate. We apply the method with a Monte Carlo simulation scheme to solve the phase diagram of a prototypical cluster-crystal former, the penetrable Sphere Model (PSM), and compare the results with earlier theoretical predictions. At high temperatures and densities, the equilibrium occupancy $n_{\mathrm{c}}^{\mathrm{eq}}$ of face-centered cubic (FCC) crystal increases linearly. At low temperatures, although $n_{\mathrm{c}}^{\mathrm{eq}}$ plateaus at integer values, the crystal behavior changes continuously with density. The previously ambiguous crossover around $T\sim0.1$ is resolved.
