The Experts below are selected from a list of 300 Experts worldwide ranked by ideXlab platform
Ruslan L Davidchack - One of the best experts on this subject based on the ideXlab platform.
-
Erratum: "Surface free energy of a hard-Sphere Fluid at curved walls: Deviations from morphometric thermodynamics" [J. Chem. Phys. 149, 174706 (2018)].
2019Co-Authors: Ruslan L Davidchack, Brian B LairdAbstract:Original article: The Journal of Chemical Physics 149 (17), 174706 (2018) In the original published article,1 there is an error in Fig. 7. That is, the solid blue line showing the third virial coefficient for the surface free energy of a hard-Sphere Fluid at a spherical wall is too large by a factor of π. The corrected figure is shown below. figure FIG. 7. The cubic curvature coefficient, γsph3, for the hard-Sphere Fluid at a spherical wall as a function of packing fraction η. The solid circles represent the results for the current simulations. The blue line shows the exact virial expansion up to third order in η [Eq. (23)]. The inset shows the same data at low packing fraction. PPT|High-resolution The corrected figure does not change the discussion or conclusions significantly. The only change is that the penultimate sentence of paragraph 7 of Sec. IV should read “As can be seen in Fig. 7, the simulation data are consistent with the virial expansion results, except for the region between η ≈ 0.08 and 0.1, where small deviations outside the statistical error bars appear.
-
surface free energy of a hard Sphere Fluid at curved walls deviations from morphometric thermodynamics
Journal of Chemical Physics, 2018Co-Authors: Ruslan L Davidchack, Brian B LairdAbstract:We report molecular-dynamics (MD) simulation results for the surface free energy of a hard-Sphere Fluid at cylindrical and spherical hard walls of different radii. The precision of the results is much higher than that in our previous study [B. B. Laird et al., Phys. Rev. E 86, 060602 (2012)], allowing us to estimate the size of deviations from the predictions of Morphometric Thermodynamics (MT). We compare our results to the analytical expressions for the surface energy as a function of wall radius R and Fluid density derived from the White Bear II variant of the density functional theory, as well as to the leading terms of the virial expansion. For the cylindrical wall, we observe deviations from MT proportional to R−2 and R−3, which are consistent with the available virial expressions. For the spherical wall, while the precision is not sufficient to detect statistically significant deviations from MT, the MD results indicate the range of densities for which the truncated virial expansions are applicable.We report molecular-dynamics (MD) simulation results for the surface free energy of a hard-Sphere Fluid at cylindrical and spherical hard walls of different radii. The precision of the results is much higher than that in our previous study [B. B. Laird et al., Phys. Rev. E 86, 060602 (2012)], allowing us to estimate the size of deviations from the predictions of Morphometric Thermodynamics (MT). We compare our results to the analytical expressions for the surface energy as a function of wall radius R and Fluid density derived from the White Bear II variant of the density functional theory, as well as to the leading terms of the virial expansion. For the cylindrical wall, we observe deviations from MT proportional to R−2 and R−3, which are consistent with the available virial expressions. For the spherical wall, while the precision is not sufficient to detect statistically significant deviations from MT, the MD results indicate the range of densities for which the truncated virial expansions are applicable.
-
properties of the hard Sphere Fluid at a planar wall using virial series and molecular dynamics simulation
Journal of Chemical Physics, 2018Co-Authors: Ivan Paganini, Ruslan L Davidchack, Brian B Laird, Ignacio UrrutiaAbstract:We study the hard-Sphere Fluid in contact with a planar hard wall. By combining the inhomogeneous virial series with simulation results, we achieve a new benchmark of accuracy for the calculation of surface thermodynamics properties such as surface adsorption Γ and the surface free energy (or surface tension), γ. We briefly introduce the problem of choosing a position for the dividing surface and avoid it by proposing the use of alternative functions to Γ and γ that are independent of the adopted frame of reference. Finally, we present analytic expressions for the dependence of system surface thermodynamic properties on packing fraction, ensuring the high accuracy of the parameterized functions for any frame of reference. The proposed parametric expressions for both, Γ and γ, fit the accurate simulation results within the statistical error.
-
hard Spheres at a planar hard wall simulations and density functional theory
arXiv: Statistical Mechanics, 2016Co-Authors: Ruslan L Davidchack, Brian B Laird, Roland RothAbstract:Hard Spheres are a central and important model reference system for both homogeneous and inhomogeneous Fluid systems. In this paper we present new high-precision molecular-dynamics computer simulations for a hard Sphere Fluid at a planar hard wall. For this system we present benchmark data for the density profile $\rho(z)$ at various bulk densities, the wall surface free energy $\gamma$, the excess adsorption $\Gamma$, and the excess volume $v_{ex}$, which is closely related to $\Gamma$. We compare all benchmark quantities with predictions from state-of-the-art classical density functional theory calculations within the framework of fundamental measure theory. While we find overall good agreement between computer simulations and theory, significant deviations appear at sufficiently high bulk densities.
-
parameterising the surface free energy and excess adsorption of a hard Sphere Fluid at a planar hard wall
Molecular Physics, 2015Co-Authors: Ruslan L Davidchack, Brian B Laird, Roland RothAbstract:The inhomogeneous structure of a Fluid at a wall can be characterised in several ways. Within a thermodynamic description, the surface free energy γ and the excess adsorption Γ are of central importance. For theoretical studies, closed expression of γ and Γ can be very valuable; however, even for a well-studied model system such as a hard-Sphere Fluid at a planar hard wall, the accuracy of existing expressions for γ and Γ, compared to precise computer simulation data, can still be improved. Here, we compare several known expressions for γ and Γ to the most precise computer simulation data. While good agreement is generally found at low to intermediate Fluid densities, the existing parameterisations show significant deviation at high density. In this work, we propose new parameterisations for γ and Γ that agree with the simulation data within statistical error over the entire Fluid density range.
Brian B Laird - One of the best experts on this subject based on the ideXlab platform.
-
Erratum: "Surface free energy of a hard-Sphere Fluid at curved walls: Deviations from morphometric thermodynamics" [J. Chem. Phys. 149, 174706 (2018)].
2019Co-Authors: Ruslan L Davidchack, Brian B LairdAbstract:Original article: The Journal of Chemical Physics 149 (17), 174706 (2018) In the original published article,1 there is an error in Fig. 7. That is, the solid blue line showing the third virial coefficient for the surface free energy of a hard-Sphere Fluid at a spherical wall is too large by a factor of π. The corrected figure is shown below. figure FIG. 7. The cubic curvature coefficient, γsph3, for the hard-Sphere Fluid at a spherical wall as a function of packing fraction η. The solid circles represent the results for the current simulations. The blue line shows the exact virial expansion up to third order in η [Eq. (23)]. The inset shows the same data at low packing fraction. PPT|High-resolution The corrected figure does not change the discussion or conclusions significantly. The only change is that the penultimate sentence of paragraph 7 of Sec. IV should read “As can be seen in Fig. 7, the simulation data are consistent with the virial expansion results, except for the region between η ≈ 0.08 and 0.1, where small deviations outside the statistical error bars appear.
-
surface free energy of a hard Sphere Fluid at curved walls deviations from morphometric thermodynamics
Journal of Chemical Physics, 2018Co-Authors: Ruslan L Davidchack, Brian B LairdAbstract:We report molecular-dynamics (MD) simulation results for the surface free energy of a hard-Sphere Fluid at cylindrical and spherical hard walls of different radii. The precision of the results is much higher than that in our previous study [B. B. Laird et al., Phys. Rev. E 86, 060602 (2012)], allowing us to estimate the size of deviations from the predictions of Morphometric Thermodynamics (MT). We compare our results to the analytical expressions for the surface energy as a function of wall radius R and Fluid density derived from the White Bear II variant of the density functional theory, as well as to the leading terms of the virial expansion. For the cylindrical wall, we observe deviations from MT proportional to R−2 and R−3, which are consistent with the available virial expressions. For the spherical wall, while the precision is not sufficient to detect statistically significant deviations from MT, the MD results indicate the range of densities for which the truncated virial expansions are applicable.We report molecular-dynamics (MD) simulation results for the surface free energy of a hard-Sphere Fluid at cylindrical and spherical hard walls of different radii. The precision of the results is much higher than that in our previous study [B. B. Laird et al., Phys. Rev. E 86, 060602 (2012)], allowing us to estimate the size of deviations from the predictions of Morphometric Thermodynamics (MT). We compare our results to the analytical expressions for the surface energy as a function of wall radius R and Fluid density derived from the White Bear II variant of the density functional theory, as well as to the leading terms of the virial expansion. For the cylindrical wall, we observe deviations from MT proportional to R−2 and R−3, which are consistent with the available virial expressions. For the spherical wall, while the precision is not sufficient to detect statistically significant deviations from MT, the MD results indicate the range of densities for which the truncated virial expansions are applicable.
-
properties of the hard Sphere Fluid at a planar wall using virial series and molecular dynamics simulation
Journal of Chemical Physics, 2018Co-Authors: Ivan Paganini, Ruslan L Davidchack, Brian B Laird, Ignacio UrrutiaAbstract:We study the hard-Sphere Fluid in contact with a planar hard wall. By combining the inhomogeneous virial series with simulation results, we achieve a new benchmark of accuracy for the calculation of surface thermodynamics properties such as surface adsorption Γ and the surface free energy (or surface tension), γ. We briefly introduce the problem of choosing a position for the dividing surface and avoid it by proposing the use of alternative functions to Γ and γ that are independent of the adopted frame of reference. Finally, we present analytic expressions for the dependence of system surface thermodynamic properties on packing fraction, ensuring the high accuracy of the parameterized functions for any frame of reference. The proposed parametric expressions for both, Γ and γ, fit the accurate simulation results within the statistical error.
-
hard Spheres at a planar hard wall simulations and density functional theory
arXiv: Statistical Mechanics, 2016Co-Authors: Ruslan L Davidchack, Brian B Laird, Roland RothAbstract:Hard Spheres are a central and important model reference system for both homogeneous and inhomogeneous Fluid systems. In this paper we present new high-precision molecular-dynamics computer simulations for a hard Sphere Fluid at a planar hard wall. For this system we present benchmark data for the density profile $\rho(z)$ at various bulk densities, the wall surface free energy $\gamma$, the excess adsorption $\Gamma$, and the excess volume $v_{ex}$, which is closely related to $\Gamma$. We compare all benchmark quantities with predictions from state-of-the-art classical density functional theory calculations within the framework of fundamental measure theory. While we find overall good agreement between computer simulations and theory, significant deviations appear at sufficiently high bulk densities.
-
parameterising the surface free energy and excess adsorption of a hard Sphere Fluid at a planar hard wall
Molecular Physics, 2015Co-Authors: Ruslan L Davidchack, Brian B Laird, Roland RothAbstract:The inhomogeneous structure of a Fluid at a wall can be characterised in several ways. Within a thermodynamic description, the surface free energy γ and the excess adsorption Γ are of central importance. For theoretical studies, closed expression of γ and Γ can be very valuable; however, even for a well-studied model system such as a hard-Sphere Fluid at a planar hard wall, the accuracy of existing expressions for γ and Γ, compared to precise computer simulation data, can still be improved. Here, we compare several known expressions for γ and Γ to the most precise computer simulation data. While good agreement is generally found at low to intermediate Fluid densities, the existing parameterisations show significant deviation at high density. In this work, we propose new parameterisations for γ and Γ that agree with the simulation data within statistical error over the entire Fluid density range.
Thomas M Truskett - One of the best experts on this subject based on the ideXlab platform.
-
communication from close packed to topologically close packed formation of laves phases in moderately polydisperse hard Sphere mixtures
Journal of Chemical Physics, 2018Co-Authors: Beth A Lindquist, Ryan B Jadrich, Thomas M TruskettAbstract:Particle size polydispersity can help to inhibit crystallization of the hard-Sphere Fluid into close-packed structures at high packing fractions and thus is often employed to create model glass-forming systems. Nonetheless, it is known that hard-Sphere mixtures with modest polydispersity still have ordered ground states. Here, we demonstrate by computer simulation that hard-Sphere mixtures with increased polydispersity fractionate on the basis of particle size and a bimodal subpopulation favors the formation of topologically close-packed C14 and C15 Laves phases in coexistence with a disordered phase. The generality of this result is supported by simulations of hard-Sphere mixtures with particle-size distributions of four different forms.
-
from close packed to topologically close packed formation of laves phases in moderately polydisperse hard Sphere mixtures
arXiv: Soft Condensed Matter, 2018Co-Authors: Beth A Lindquist, Ryan B Jadrich, Thomas M TruskettAbstract:Particle size polydispersity can help to inhibit crystallization of the hard-Sphere Fluid into close-packed structures at high packing fractions and thus is often employed to create model glass-forming systems. Nonetheless, it is known that hard-Sphere mixtures with modest polydispersity still have ordered ground states. Here, we demonstrate by computer simulation that hard-Sphere mixtures with increased polydispersity fractionate on the basis of particle size, and a bimodal subpopulation favors formation of topologically close-packed C14 and C15 Laves phases in coexistence with a disordered phase. The generality of this result is supported by simulations of hard-Sphere mixtures with particle-size distributions of four different forms.
-
does confining the hard Sphere Fluid between hard walls change its average properties
Journal of Chemical Physics, 2007Co-Authors: Jeetain Mittal, Jeffrey R Errington, Thomas M TruskettAbstract:We use grand canonical transition-matrix Monte Carlo and discontinuous molecular dynamics simulations to generate precise thermodynamic and kinetic data for the equilibrium hard-Sphere Fluid confined between smooth hard walls. These simulations show that the pronounced inhomogeneous structuring of the Fluid normal to the confining walls, often the primary focus of density functional theory studies, has a negligible effect on many of its average properties over a surprisingly broad range of conditions. We present one consequence of this insensitivity to confinement: a simple analytical equation relating the average density of the confined Fluid to that of the bulk Fluid with equal activity. Nontrivial implications of confinement for average Fluid properties do emerge in this system, but only when the Fluid is both (i) dense and (ii) confined to a gap smaller than approximately three particle diameters. For this limited set of conditions, we find that “in-phase” oscillatory deviations in excess entropy and ...
-
does confining the hard Sphere Fluid between hard walls change its average properties
arXiv: Soft Condensed Matter, 2007Co-Authors: Jeetain Mittal, Jeffrey R Errington, Thomas M TruskettAbstract:We use grand canonical transition-matrix Monte Carlo and discontinuous molecular dynamics simulations to generate precise thermodynamic and kinetic data for the equilibrium hard-Sphere Fluid confined between smooth hard walls. These simulations show that the pronounced inhomogeneous structuring of the Fluid normal to the confining walls, often the primary focus of density functional theory studies, has a negligible effect on many of its average properties over a surprisingly broad range of conditions. We present one consequence of this insensitivity to confinement: a simple analytical equation relating the average density of the confined Fluid to that of the bulk Fluid with equal activity. Nontrivial implications of confinement for average Fluid properties do emerge in this system, but only when the Fluid is both (i) dense and (ii) confined to a gap smaller than approximately three particle diameters. For this limited set of conditions, we find that "in-phase" oscillatory deviations in excess entropy and self-diffusivity (relative to the behavior of the bulk Fluid at the same average density) occur as a function of gap size. These paired thermodynamic/kinetic deviations from bulk behavior appear to reflect the geometric packing frustration that arises when the confined space cannot naturally accommodate an integer number of particle layers.
-
thermodynamics predicts how confinement modifies the dynamics of the equilibrium hard Sphere Fluid
Physical Review Letters, 2006Co-Authors: Jeetain Mittal, Jeffrey R Errington, Thomas M TruskettAbstract:We study how confining the equilibrium hard-Sphere Fluid to restrictive one- and two-dimensional channels with smooth interacting walls modifies its structure, dynamics, and entropy using molecular dynamics and transition-matrix Monte Carlo simulations. Although confinement strongly affects local structuring, the relationships between self-diffusivity, excess entropy, and average Fluid density are, to an excellent approximation, independent of channel width or particle-wall interactions. Thus, thermodynamics can be used to predict how confinement impacts dynamics. PACS numbers: The molecular dynamics of Fluids confined to small spaces can differ significantly from the bulk. These differences have generated wide interest because confined Fluids feature prominantly in both nature and technology. Examples include dynamics of water near proteins or in concentrated cellular environments, transport processes across biological membranes, and Fluid flows encountered in micro- or nanoFluidic devices, to mention a few. Given that a significant fraction of the molecules in these systems populate highly inhomogeneous interfacial environments, it is easy to appreciate why confinement has nontrivial consequences for their transport coefficients (e.g., diffusivity and viscosity). Nonetheless, a theoretical framework that can reliably predict these consequences has been slow to develop.
Ignacio Urrutia - One of the best experts on this subject based on the ideXlab platform.
-
properties of the hard Sphere Fluid at a planar wall using virial series and molecular dynamics simulation
Journal of Chemical Physics, 2018Co-Authors: Ivan Paganini, Ruslan L Davidchack, Brian B Laird, Ignacio UrrutiaAbstract:We study the hard-Sphere Fluid in contact with a planar hard wall. By combining the inhomogeneous virial series with simulation results, we achieve a new benchmark of accuracy for the calculation of surface thermodynamics properties such as surface adsorption Γ and the surface free energy (or surface tension), γ. We briefly introduce the problem of choosing a position for the dividing surface and avoid it by proposing the use of alternative functions to Γ and γ that are independent of the adopted frame of reference. Finally, we present analytic expressions for the dependence of system surface thermodynamic properties on packing fraction, ensuring the high accuracy of the parameterized functions for any frame of reference. The proposed parametric expressions for both, Γ and γ, fit the accurate simulation results within the statistical error.
-
bending rigidity and higher order curvature terms for the hard Sphere Fluid near a curved wall
Physical Review E, 2014Co-Authors: Ignacio UrrutiaAbstract:In this work I derive analytic expressions for the curvature-dependent Fluid-substrate surface tension of a hard-Sphere Fluid on a hard curved wall. In the first step, the curvature thermodynamic properties are found as truncated power series in the activity in terms of the exactly known second- and third-order cluster integrals of the hard-Sphere Fluid near spherical and cylindrical walls. These results are then expressed as packing fraction power series and transformed to different reference regions, which is equivalent to considering different positions of the dividing surface. Based on the truncated series it is shown that the bending rigidity of the system is non-null and that higher-order terms in the curvature also exist. In the second step, approximate analytic expressions for the surface tension, the Tolman length, the bending rigidity, and the Gaussian rigidity as functions of the packing fraction are found by considering the known terms of the series expansion complemented with a simple fitting approach. It is found that the obtained formulas accurately describe the curvature thermodynamic properties of the system; further, they are more accurate than any previously published expressions.
J R Solana - One of the best experts on this subject based on the ideXlab platform.
-
a simplified analytical expression for the first shell of the hard Sphere Fluid radial distribution function
Fluid Phase Equilibria, 2000Co-Authors: J Largo, J R SolanaAbstract:Abstract An analytical expression for the first coordination cell of the radial distribution function (RDF) of the hard-Sphere Fluid is derived. It is based on a series expansion of the analytical expression of the Percus–Yevick solution of the RDF of the hard-Sphere Fluid derived by Chang and Sandler [J. Chang, S.I. Sandler, Mol. Phys. 81 (1994) 745.]. The expansion is carried out both in terms of the packing fraction and in terms of the radial distance. Expressions are also obtained for the coordination number and its first and second derivatives as functions of radial distance and packing fraction. These expressions, which are useful in perturbation theory, are simpler to use than those obtained from the starting equation, while giving nearly the same results. They also provide close agreement with simulation data.
-
an accurate equation of state for hard gaussian overlap Fluids from a generalized carnahan starling method
Molecular Physics, 1993Co-Authors: M J Maeso, J R SolanaAbstract:The Carnahan-Starling method for obtaining the equation of state of the hard-Sphere Fluid is generalized and used to derive an equation of state for hard Gaussian overlap Fluids. The results are in excellent agreement with existing simulation data.
-
equation of state for the soft Sphere Fluid from a direct summation of the virial series
Journal of Chemical Physics, 1993Co-Authors: M J Maeso, J R SolanaAbstract:An equation of state for the inverse‐twelfth‐power soft‐Sphere Fluid is obtained by direct summation of the virial series. To do so, a generalization of the Carnahan–Starling method for obtaining the equation of state of the hard‐Sphere Fluid is used. The equation of state obtained in this way reproduces accurately the simulation data for both the stable and metastable Fluid regions. Agreement remains good up to the neighborhood of the glass transition where the equation of state predicts that the soft‐Sphere Fluid becomes unstable.