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Bin Chen - One of the best experts on this subject based on the ideXlab platform.
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surface induced Nucleation of a lennard jones system on an implicit surface at sub freezing temperatures a comparison with the Classical Nucleation Theory
Journal of Chemical Physics, 2013Co-Authors: Troy D Loeffler, Bin ChenAbstract:The aggregation-volume-bias Monte Carlo method was employed to study surface-induced Nucleation of Lennard-Jonesium on an implicit surface below the melting point. It was found that surfaces catalyze not only the formation of the droplets (where the Nucleation free energy barriers were shown to decrease with increasing surface interaction strength), but also the transition of these droplets into crystal structures due to the surface-induced layering effects. However, this only occurs under suitable interaction strength. When surface attraction is too strong, crystallization is actually inhibited due to the spread of the particles across the surface and corresponding formation of two-dimensional clusters. The simulation results were also used to examine the bulk-droplet based Classical Nucleation Theory for surface-induced Nucleation, particularly the additional contact angle term used to describe both the Nucleation free energy barrier heights and the critical cluster sizes compared to its homogeneous nuc...
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an aggregation volume bias monte carlo investigation on the condensation of a lennard jones vapor below the triple point and crystal Nucleation in cluster systems an in depth evaluation of the Classical Nucleation Theory
Journal of Physical Chemistry B, 2008Co-Authors: Bin Chen, Samuel J Keasler, Ricky B NellasAbstract:The aggregation-volume-bias Monte Carlo based simulation technique, which has led to our recent success in vapor−liquid Nucleation research, was extended to the study of crystal Nucleation processes. In contrast to conventional bulk-phase techniques, this method deals with crystal Nucleation events in cluster systems. This approach was applied to the crystal Nucleation of Lennard-Jonesium under a wide range of undercooling conditions from 35% to 13% below the triple point. It was found that crystal Nucleation in these model clusters proceeds initially via a vapor−liquid like aggregation followed by the formation of crystals inside the aggregates. The separation of these two stages of Nucleation is distinct except at deeper undercooling conditions where the crystal Nucleation barrier was found to diminish. The simulation results obtained for these two Nucleation steps are separately compared to the Classical Nucleation Theory (CNT). For the vapor−liquid Nucleation step, the CNT was shown to provide a reaso...
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an aggregation volume bias monte carlo investigation on the condensation of a lennard jones vapor below the triple point and crystal Nucleation in cluster systems an in depth evaluation of the Classical Nucleation Theory
Journal of Physical Chemistry B, 2008Co-Authors: Bin Chen, Samuel J Keasler, Hyunmi Kim, Ricky B NellasAbstract:The aggregation-volume-bias Monte Carlo based simulation technique, which has led to our recent success in vapor-liquid Nucleation research, was extended to the study of crystal Nucleation processes. In contrast to conventional bulk-phase techniques, this method deals with crystal Nucleation events in cluster systems. This approach was applied to the crystal Nucleation of Lennard-Jonesium under a wide range of undercooling conditions from 35% to 13% below the triple point. It was found that crystal Nucleation in these model clusters proceeds initially via a vapor-liquid like aggregation followed by the formation of crystals inside the aggregates. The separation of these two stages of Nucleation is distinct except at deeper undercooling conditions where the crystal Nucleation barrier was found to diminish. The simulation results obtained for these two Nucleation steps are separately compared to the Classical Nucleation Theory (CNT). For the vapor-liquid Nucleation step, the CNT was shown to provide a reasonable description of the critical cluster size but overestimate the barrier heights, consistent with previous simulation studies. On the contrary, for the crystal Nucleation step, nearly perfect agreement with the barrier heights was found between the simulations and the CNT. For the critical cluster size, the comparison is more difficult as the simulation data were found to be sensitive to the definition of the solid cluster, but a stringent criterion and lower undercooling conditions generally lead to results closer with the CNT. Additional simulations at undercooling conditions of 40% or above indicate a nearly barrierless transition from the liquid to crystalline-like structure for sufficiently large clusters, which leads to further departure of the barrier height predicted by the CNT from the simulation data for the aggregation step. This is consistent with the latest experimental results on argon that show an unusually large underestimation of the Nucleation rate by the CNT toward deep undercooling conditions.
Daan Frenkel - One of the best experts on this subject based on the ideXlab platform.
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homogeneous bubble Nucleation driven by local hot spots a molecular dynamics study
arXiv: Chemical Physics, 2009Co-Authors: Zunjing Wang, Chantal Valeriani, Daan FrenkelAbstract:We report a Molecular Dynamics study of homogenous bubble Nucleation in a Lennard-Jones fluid. The rate of bubble Nucleation is estimated using forward-flux sampling (FFS). We find that cavitation starts with compact bubbles rather than with ramified structures as had been suggested by Shen and Debenedetti (J. Chem. Phys. 111:3581, 1999). Our estimate of the bubble-Nucleation rate is higher than predicted on the basis of Classical Nucleation Theory (CNT). Our simulations show that local temperature fluctuations correlate strongly with subsequent bubble formation - this mechanism is not taken into account in CNT.
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homogeneous bubble Nucleation driven by local hot spots a molecular dynamics study
Journal of Physical Chemistry B, 2009Co-Authors: Zunjing Wang, Chantal Valeriani, Daan FrenkelAbstract:We report a molecular dynamics study of homogeneous bubble Nucleation in a Lennard-Jones fluid. The rate of bubble Nucleation is estimated using forward-flux sampling (FFS). We find that cavitation starts with compact bubbles rather than with ramified structures, as had been suggested by Shen and Debenedetti (J. Chem. Phys. 1999, 111, 3581). Our estimate of the bubble-Nucleation rate is higher than predicted on the basis of Classical Nucleation Theory (CNT). Our simulations show that local temperature fluctuations correlate strongly with subsequent bubble formation; this mechanism is not taken into account in CNT.
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numerical prediction of absolute crystallization rates in hard sphere colloids
Journal of Chemical Physics, 2004Co-Authors: Stefan Auer, Daan FrenkelAbstract:Special computational techniques are required to compute absolute crystal Nucleation rates of colloidal suspensions. Using crystal Nucleation of hard-sphere colloids as an example, we describe in some detail the novel computational tools that are needed to perform such calculations. In particular, we focus on the definition of appropriate order parameters that distinguish liquid from crystal, and on techniques to compute the kinetic prefactor that enters in the expression for the Nucleation rate. In addition, we discuss the relation between simulation results and theoretical predictions based on Classical Nucleation Theory.
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numerical calculation of the rate of homogeneous gas liquid Nucleation in a lennard jones system
Journal of Chemical Physics, 1999Co-Authors: P Ten R Wolde, M J Ruizmontero, Daan FrenkelAbstract:We report a computer-simulation study of the absolute rate of homogeneous gas–liquid Nucleation in a Lennard-Jones system. The height of the barrier has been computed using umbrella sampling, whereas the kinetic prefactor is calculated using molecular dynamics simulations. The simulations show that the Nucleation process is highly diffusive. We find that the kinetic prefactor is a factor of 10 larger than predicted by Classical Nucleation Theory.
Ricky B Nellas - One of the best experts on this subject based on the ideXlab platform.
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an aggregation volume bias monte carlo investigation on the condensation of a lennard jones vapor below the triple point and crystal Nucleation in cluster systems an in depth evaluation of the Classical Nucleation Theory
Journal of Physical Chemistry B, 2008Co-Authors: Bin Chen, Samuel J Keasler, Ricky B NellasAbstract:The aggregation-volume-bias Monte Carlo based simulation technique, which has led to our recent success in vapor−liquid Nucleation research, was extended to the study of crystal Nucleation processes. In contrast to conventional bulk-phase techniques, this method deals with crystal Nucleation events in cluster systems. This approach was applied to the crystal Nucleation of Lennard-Jonesium under a wide range of undercooling conditions from 35% to 13% below the triple point. It was found that crystal Nucleation in these model clusters proceeds initially via a vapor−liquid like aggregation followed by the formation of crystals inside the aggregates. The separation of these two stages of Nucleation is distinct except at deeper undercooling conditions where the crystal Nucleation barrier was found to diminish. The simulation results obtained for these two Nucleation steps are separately compared to the Classical Nucleation Theory (CNT). For the vapor−liquid Nucleation step, the CNT was shown to provide a reaso...
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an aggregation volume bias monte carlo investigation on the condensation of a lennard jones vapor below the triple point and crystal Nucleation in cluster systems an in depth evaluation of the Classical Nucleation Theory
Journal of Physical Chemistry B, 2008Co-Authors: Bin Chen, Samuel J Keasler, Hyunmi Kim, Ricky B NellasAbstract:The aggregation-volume-bias Monte Carlo based simulation technique, which has led to our recent success in vapor-liquid Nucleation research, was extended to the study of crystal Nucleation processes. In contrast to conventional bulk-phase techniques, this method deals with crystal Nucleation events in cluster systems. This approach was applied to the crystal Nucleation of Lennard-Jonesium under a wide range of undercooling conditions from 35% to 13% below the triple point. It was found that crystal Nucleation in these model clusters proceeds initially via a vapor-liquid like aggregation followed by the formation of crystals inside the aggregates. The separation of these two stages of Nucleation is distinct except at deeper undercooling conditions where the crystal Nucleation barrier was found to diminish. The simulation results obtained for these two Nucleation steps are separately compared to the Classical Nucleation Theory (CNT). For the vapor-liquid Nucleation step, the CNT was shown to provide a reasonable description of the critical cluster size but overestimate the barrier heights, consistent with previous simulation studies. On the contrary, for the crystal Nucleation step, nearly perfect agreement with the barrier heights was found between the simulations and the CNT. For the critical cluster size, the comparison is more difficult as the simulation data were found to be sensitive to the definition of the solid cluster, but a stringent criterion and lower undercooling conditions generally lead to results closer with the CNT. Additional simulations at undercooling conditions of 40% or above indicate a nearly barrierless transition from the liquid to crystalline-like structure for sufficiently large clusters, which leads to further departure of the barrier height predicted by the CNT from the simulation data for the aggregation step. This is consistent with the latest experimental results on argon that show an unusually large underestimation of the Nucleation rate by the CNT toward deep undercooling conditions.
Caizhuang Wang - One of the best experts on this subject based on the ideXlab platform.
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competitive b2 and b33 Nucleation during solidification of ni50zr50 alloy molecular dynamics simulation and Classical Nucleation Theory
Journal of Physical Chemistry C, 2019Co-Authors: Yang Sun, Feng Zhang, Huajing Song, Mikhail I Mendelev, Caizhuang WangAbstract:We investigated the homogenous Nucleation of the stoichiometric B2 and B33 phases in the Ni50Zr50 alloy using the persistent embryo method and the Classical Nucleation Theory. The two phases become very close competitors at large supercoolings, which is consistent with the experimental observations. In the case of the B2 phase, the linear temperature dependence of the solid–liquid interface (SLI) free energy extrapolated to the melting temperature leads to the same value as the one obtained from the capillarity fluctuation method (CFM). In the case of the B33 phases, the SLI free energy is also a linear function of temperature at large supercoolings, but the extrapolation to the melting temperature leads to a value which is considerably different from the CFM value. This is consistent with the large anisotropy of the SLI properties of the B33 phase nearby the melting temperature observed in the simulation of the nominally flat interface migration.
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temperature dependence of the solid liquid interface free energy of ni and al from molecular dynamics simulation of Nucleation
Journal of Chemical Physics, 2018Co-Authors: Yang Sun, Feng Zhang, Huajing Song, Mikhail I Mendelev, Caizhuang WangAbstract:The temperature dependence of the solid-liquid interfacial free energy, γ, is investigated for Al and Ni at the undercooled temperature regime based on a recently developed persistent-embryo method. The atomistic description of the nucleus shape is obtained from molecular dynamics simulations. The computed γ shows a linear dependence on the temperature. The values of γ extrapolated to the melting temperature agree well with previous data obtained by the capillary fluctuation method. Using the temperature dependence of γ, we estimate the Nucleation free energy barrier in a wide temperature range from the Classical Nucleation Theory. The obtained data agree very well with the results from the brute-force molecular dynamics simulations.The temperature dependence of the solid-liquid interfacial free energy, γ, is investigated for Al and Ni at the undercooled temperature regime based on a recently developed persistent-embryo method. The atomistic description of the nucleus shape is obtained from molecular dynamics simulations. The computed γ shows a linear dependence on the temperature. The values of γ extrapolated to the melting temperature agree well with previous data obtained by the capillary fluctuation method. Using the temperature dependence of γ, we estimate the Nucleation free energy barrier in a wide temperature range from the Classical Nucleation Theory. The obtained data agree very well with the results from the brute-force molecular dynamics simulations.
Zhengang Wang - One of the best experts on this subject based on the ideXlab platform.
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minimum energy path to membrane pore formation and rupture
Physical Review Letters, 2011Co-Authors: Christina L Ting, Daniel Appelo, Zhengang WangAbstract:We combine dynamic self-consistent field Theory with the string method to calculate the minimum energy path to membrane pore formation and rupture. In the regime where Nucleation can occur on experimentally relevant time scales, the structure of the critical nucleus is between a solvophilic stalk and a locally thinned membrane. Classical Nucleation Theory fails to capture these molecular details and significantly overestimates the free energy barrier. Our results suggest that thermally nucleated rupture may be an important factor for the low rupture strains observed in lipid membranes.
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Nucleation of stable cylinders from a metastable lamellar phase in a diblock copolymer melt
Journal of Chemical Physics, 2003Co-Authors: Robert A Wickham, Anchang Shi, Zhengang WangAbstract:The Nucleation of a droplet of stable cylinder phase from a metastable lamellar phase is examined within the single-mode approximation to the mean-field Landau–Brazovskii model for diblock copolymer melts. By employing a variational ansatz for the droplet interfacial profile, an analytic expression for the interfacial free energy of an interface of arbitrary orientation between cylinders and lamellae is found. The interfacial free energy is anisotropic and is lower when the cylinder axis is perpendicular to the interface than when the cylinders lie along the interface. Consequently, the droplet shape computed via the Wulff construction is lens like, being flattened along the axis of the cylinders. The size of the critical droplet and the Nucleation barrier are determined within Classical Nucleation Theory. Near the lamellar–cylinder phase boundary, where Classical Nucleation Theory is applicable, critical droplets of size 30–400 cylinders across with aspect ratios of 4–10 and Nucleation barriers of (30–40)kBT are typically found. The general trend is to larger critical droplets, higher aspect ratios, and smaller Nucleation barriers as the mean-field critical point is approached.
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Nucleation of stable cylinders from a metastable lamellar phase in a diblock copolymer melt
arXiv: Soft Condensed Matter, 2003Co-Authors: Robert A Wickham, Anchang Shi, Zhengang WangAbstract:The Nucleation of a droplet of stable cylinder phase from a metastable lamellar phase is examined within the single-mode approximation to the Brazovskii model for diblock copolymer melts. By employing a variational ansatz for the droplet interfacial profile, an analytic expression for the interfacial free-energy of an interface of arbitrary orientation between cylinders and lamellae is found. The interfacial free-energy is anisotropic, and is lower when the cylinder axis is perpendicular to the interface than when the cylinders lie along the interface. Consequently, the droplet shape computed via the Wulff construction is lens-like, being flattened along the axis of the cylinders. The size of the critical droplet and the Nucleation barrier are determined within Classical Nucleation Theory. Near the lamellar/cylinder phase boundary, where Classical Nucleation Theory is applicable, critical droplets of size 30--400 cylinders across with aspect ratios of 4--10 and Nucleation barriers of 30--40 k_B T are typically found. The general trend is to larger critical droplets, higher aspect ratios and smaller Nucleation barriers as the mean-field critical point is approached.