The Experts below are selected from a list of 39948 Experts worldwide ranked by ideXlab platform
R L C Vink - One of the best experts on this subject based on the ideXlab platform.
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fluid phase separation inside a static periodic field an effectively two dimensional critical phenomenon
Journal of Chemical Physics, 2011Co-Authors: R L C Vink, Tim Neuhaus, Hartmut LowenAbstract:When a fluid with a bulk liquid-vapor critical point is placed inside a static external field with spatial periodic oscillations in one direction, a new phase arises. This new phase—the so-called “zebra” phase—is characterized by an average density roughly between that of the liquid and vapor phases. The presence of the zebra phase gives rise to two new phase transitions: one from the vapor to the zebra phase, and one from the zebra to the liquid phase. At appropriate values of the temperature and chemical potential, the latter two transitions become critical. This phenomenon is called laser-induced condensation [I. O. Gotze, J. M. Brader, M. Schmidt, and H. Lowen, Mol. Phys. 101, 1651 (2003)]. The purpose of this paper is to elucidate the nature of the critical points, using density functional theory and computer simulation of a colloid-Polymer Mixture. The main finding is that critical correlations develop in two-dimensional sheets perpendicular to the field direction, but not in the direction along the...
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capillary waves in a colloid Polymer interface
Journal of Chemical Physics, 2005Co-Authors: R L C Vink, Jurgen Horbach, K BinderAbstract:The structure and the statistical fluctuations of interfaces between coexisting phases in the Asakura–Oosawa model [J. Chem. Phys. 22, 1255 (1954)] for a colloid-Polymer Mixture are analyzed by extensive Monte Carlo simulations. We make use of a recently developed grand canonical cluster move with an additional constraint stabilizing the existence of two interfaces in the (rectangular) box that is simulated. Choosing very large systems, of size L×L×D with L=60 and D=120, measured in units of the colloid radius, the spectrum of capillary wave-type interfacial excitations is analyzed in detail. The local position of the interface is defined in terms of a (local) Gibbs surface concept. For small wave vectors capillary wave theory is verified quantitatively, while for larger wave vectors pronounced deviations show up. When one analyzes the data in terms of the concept of a wave vector–dependent interfacial tension, a monotonous decrease of this quantity with increasing wave vector is found. Limitations of our...
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capillary waves in a colloid Polymer interface
arXiv: Soft Condensed Matter, 2004Co-Authors: R L C Vink, Jurgen Horbach, K BinderAbstract:The structure and the statistical fluctuations of interfaces between coexisting phases in the Asakura-Oosawa (AO) model for a colloid--Polymer Mixture are analyzed by extensive Monte Carlo simulations. We make use of a recently developed grand canonical cluster move with an additional constraint stabilizing the existence of two interfaces in the (rectangular) box that is simulated. Choosing very large systems, of size LxLxD with L=60 and D=120, measured in units of the colloid radius, the spectrum of capillary wave-type interfacial excitations is analyzed in detail. The local position of the interface is defined in terms of a (local) Gibbs surface concept. For small wavevectors capillary wave theory is verified quantitatively, while for larger wavevectors pronounced deviations show up. For wavevectors that correspond to the typical distance between colloids in the colloid-rich phase, the interfacial fluctuations exhibit the same structure as observed in the bulk structure factor. When one analyzes the data in terms of the concept of a wavevector-dependent interfacial tension, a monotonous decrease of this quantity with increasing wavevector is found. Limitations of our analysis are critically discussed.
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grand canonical monte carlo simulation of a model colloid Polymer Mixture coexistence line critical behavior and interfacial tension
Journal of Chemical Physics, 2004Co-Authors: R L C Vink, Jurgen HorbachAbstract:Grand canonical Monte Carlo simulations are used to study phase separation in a simple colloid–Polymer model, the so-called Asakura–Oosawa model. To overcome the problem of small acceptance rates of the grand-canonical moves, cluster moves are introduced. Successive umbrella sampling, recently introduced by Virnau and Muller [J. Chem. Phys. 120, 10925 (2004)], is used to access the phase-separated regime. The unmixing binodal and the interfacial tension are measured and compared to theoretical predictions. By means of finite-size scaling, the behavior close to the critical point is also investigated. Close to criticality, we observe substantial deviations from mean-field behavior.
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the fluid fluid interface in a model colloid Polymer Mixture application of grand canonical monte carlo to asymmetric binary Mixtures
arXiv: Soft Condensed Matter, 2003Co-Authors: R L C Vink, Jurgen Horbach, Staudinger WegAbstract:We present a Monte Carlo method to simulate asymmetric binary Mixtures in the grand canonical ensemble. The method is used to study the colloid–Polymer model of Asakura and Oosawa. We determine the phase diagram of the fluid–fluid unmixing transition and the interfacial tension, both at high Polymer density and close to the critical point. We also present density profiles in the two–phase region. The results are compared to predictions of a recent density functional theory.
Osamu Terasaki - One of the best experts on this subject based on the ideXlab platform.
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tailoring the pore structure of sba 16 silica molecular sieve through the use of coPolymer blends and control of synthesis temperature and time
Journal of Physical Chemistry B, 2004Co-Authors: Taewan Kim, Ryong Ryoo, Michal Kruk, Kamil P Gierszal, Mietek Jaroniec, And Satoshi Kamiya, Osamu TerasakiAbstract:SBA-16 mesoporous silicas with cubic Im3m structure were synthesized using Pluronic F127 poly(ethylene oxide)−poly(propylene oxide)−poly(ethylene oxide) triblock coPolymer (EO106PO70EO106) and its blends with Pluronic P123 triblock coPolymer (EO20PO70EO20) as supramolecular templates. The resulting materials were characterized using X-ray diffraction, transmission electron microscopy, and argon and nitrogen adsorption. Selected samples were also modified with series of organosilanes of gradually increasing sizes and the accessibility of the pore structure after the modification was assessed using argon adsorption, which allowed us to determine the diameter of entrances to the ordered mesopores. It was shown that the pore cage diameter in SBA-16 can be enlarged in a wide range not only by increasing the synthesis temperature and time, as previously known, but also by increasing the content of P123 coPolymer in the Polymer Mixture. These three ways allowed us to synthesize SBA-16 with nominal mesopore diame...
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tailoring the pore structure of sba 16 silica molecular sieve through the use of coPolymer blends and control of synthesis temperature and time
Journal of Physical Chemistry B, 2004Co-Authors: Taewa Kim, Ryong Ryoo, Michal Kruk, Kamil P Gierszal, Mietek Jaroniec, And Satoshi Kamiya, Osamu TerasakiAbstract:SBA-16 mesoporous silicas with cubic Im3m structure were synthesized using Pluronic F127 poly(ethylene oxide)−poly(propylene oxide)−poly(ethylene oxide) triblock coPolymer (EO106PO70EO106) and its blends with Pluronic P123 triblock coPolymer (EO20PO70EO20) as supramolecular templates. The resulting materials were characterized using X-ray diffraction, transmission electron microscopy, and argon and nitrogen adsorption. Selected samples were also modified with series of organosilanes of gradually increasing sizes and the accessibility of the pore structure after the modification was assessed using argon adsorption, which allowed us to determine the diameter of entrances to the ordered mesopores. It was shown that the pore cage diameter in SBA-16 can be enlarged in a wide range not only by increasing the synthesis temperature and time, as previously known, but also by increasing the content of P123 coPolymer in the Polymer Mixture. These three ways allowed us to synthesize SBA-16 with nominal mesopore diame...
Jurgen Horbach - One of the best experts on this subject based on the ideXlab platform.
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capillary waves in a colloid Polymer interface
Journal of Chemical Physics, 2005Co-Authors: R L C Vink, Jurgen Horbach, K BinderAbstract:The structure and the statistical fluctuations of interfaces between coexisting phases in the Asakura–Oosawa model [J. Chem. Phys. 22, 1255 (1954)] for a colloid-Polymer Mixture are analyzed by extensive Monte Carlo simulations. We make use of a recently developed grand canonical cluster move with an additional constraint stabilizing the existence of two interfaces in the (rectangular) box that is simulated. Choosing very large systems, of size L×L×D with L=60 and D=120, measured in units of the colloid radius, the spectrum of capillary wave-type interfacial excitations is analyzed in detail. The local position of the interface is defined in terms of a (local) Gibbs surface concept. For small wave vectors capillary wave theory is verified quantitatively, while for larger wave vectors pronounced deviations show up. When one analyzes the data in terms of the concept of a wave vector–dependent interfacial tension, a monotonous decrease of this quantity with increasing wave vector is found. Limitations of our...
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capillary waves in a colloid Polymer interface
arXiv: Soft Condensed Matter, 2004Co-Authors: R L C Vink, Jurgen Horbach, K BinderAbstract:The structure and the statistical fluctuations of interfaces between coexisting phases in the Asakura-Oosawa (AO) model for a colloid--Polymer Mixture are analyzed by extensive Monte Carlo simulations. We make use of a recently developed grand canonical cluster move with an additional constraint stabilizing the existence of two interfaces in the (rectangular) box that is simulated. Choosing very large systems, of size LxLxD with L=60 and D=120, measured in units of the colloid radius, the spectrum of capillary wave-type interfacial excitations is analyzed in detail. The local position of the interface is defined in terms of a (local) Gibbs surface concept. For small wavevectors capillary wave theory is verified quantitatively, while for larger wavevectors pronounced deviations show up. For wavevectors that correspond to the typical distance between colloids in the colloid-rich phase, the interfacial fluctuations exhibit the same structure as observed in the bulk structure factor. When one analyzes the data in terms of the concept of a wavevector-dependent interfacial tension, a monotonous decrease of this quantity with increasing wavevector is found. Limitations of our analysis are critically discussed.
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grand canonical monte carlo simulation of a model colloid Polymer Mixture coexistence line critical behavior and interfacial tension
Journal of Chemical Physics, 2004Co-Authors: R L C Vink, Jurgen HorbachAbstract:Grand canonical Monte Carlo simulations are used to study phase separation in a simple colloid–Polymer model, the so-called Asakura–Oosawa model. To overcome the problem of small acceptance rates of the grand-canonical moves, cluster moves are introduced. Successive umbrella sampling, recently introduced by Virnau and Muller [J. Chem. Phys. 120, 10925 (2004)], is used to access the phase-separated regime. The unmixing binodal and the interfacial tension are measured and compared to theoretical predictions. By means of finite-size scaling, the behavior close to the critical point is also investigated. Close to criticality, we observe substantial deviations from mean-field behavior.
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the fluid fluid interface in a model colloid Polymer Mixture application of grand canonical monte carlo to asymmetric binary Mixtures
arXiv: Soft Condensed Matter, 2003Co-Authors: R L C Vink, Jurgen Horbach, Staudinger WegAbstract:We present a Monte Carlo method to simulate asymmetric binary Mixtures in the grand canonical ensemble. The method is used to study the colloid–Polymer model of Asakura and Oosawa. We determine the phase diagram of the fluid–fluid unmixing transition and the interfacial tension, both at high Polymer density and close to the critical point. We also present density profiles in the two–phase region. The results are compared to predictions of a recent density functional theory.
Omar K Farha - One of the best experts on this subject based on the ideXlab platform.
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toward base heterogenization a zirconium metal organic framework dendrimer or Polymer Mixture for rapid hydrolysis of a nerve agent simulant
ACS Applied Nano Materials, 2019Co-Authors: Zhijie Chen, Timur Islamoglu, Omar K FarhaAbstract:The base heterogenization is crucial for the practical applications of metal–organic frameworks (MOFs) as catalytic filters, such as masks or protective suits, for the deconstruction of chemical wa...
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detoxification of chemical warfare agents using a zr6 based metal organic framework Polymer Mixture
Chemistry: A European Journal, 2016Co-Authors: Suyoung Moon, Emmanuel Proussaloglou, Gregory W Peterson, Jared B Decoste, Morgan G Hall, Ashlee J Howarth, Joseph T Hupp, Omar K FarhaAbstract:Owing to their high surface area, periodic distribution of metal sites, and water stability, zirconium-based metal–organic frameworks (Zr6-MOFs) have shown promising activity for the hydrolysis of nerve agents GD and VX, as well as the simulant, dimethyl 4-nitrophenylphosphate (DMNP), in buffered solutions. A hurdle to using MOFs for this application is the current need for a buffer solution. Here the destruction of the simulant DMNP, as well as the chemical warfare agents (GD and VX) through hydrolysis using a MOF catalyst mixed with a non-volatile, water-insoluble, heterogeneous buffer is reported. The hydrolysis of the simulant and nerve agents in the presence of the heterogeneous buffer was fast and effective.
Hartmut Lowen - One of the best experts on this subject based on the ideXlab platform.
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fluid phase separation inside a static periodic field an effectively two dimensional critical phenomenon
Journal of Chemical Physics, 2011Co-Authors: R L C Vink, Tim Neuhaus, Hartmut LowenAbstract:When a fluid with a bulk liquid-vapor critical point is placed inside a static external field with spatial periodic oscillations in one direction, a new phase arises. This new phase—the so-called “zebra” phase—is characterized by an average density roughly between that of the liquid and vapor phases. The presence of the zebra phase gives rise to two new phase transitions: one from the vapor to the zebra phase, and one from the zebra to the liquid phase. At appropriate values of the temperature and chemical potential, the latter two transitions become critical. This phenomenon is called laser-induced condensation [I. O. Gotze, J. M. Brader, M. Schmidt, and H. Lowen, Mol. Phys. 101, 1651 (2003)]. The purpose of this paper is to elucidate the nature of the critical points, using density functional theory and computer simulation of a colloid-Polymer Mixture. The main finding is that critical correlations develop in two-dimensional sheets perpendicular to the field direction, but not in the direction along the...
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density functional theory for a model colloid Polymer Mixture bulk fluid phases
Journal of Physics: Condensed Matter, 2002Co-Authors: Matthias Schmidt, Joseph M Brader, Hartmut Lowen, Robert EvansAbstract:We describe a density functional theory for Mixtures of hard sphere (HS) colloids and ideal Polymers, the Asakura–Oosawa model. The geometrybased fundamental measures approach which is used to construct the functional ensures the correct behaviour in the limit of low density of both species and in the zero-dimensional limit of a cavity which can contain at most one HS. Dimensional crossover is discussed in detail. Emphasis is placed on the properties of homogeneous (bulk) fluid phases. We show that the present functional yields the same free energy and, therefore, the same fluid–fluid demixing transition as that given by a different approach, namely the freevolume theory. The pair direct correlation functions c (2) ij (r ) of the bul km ixture are given analytically. We investigate the partial structure factors S ij (k) and the asymptotic decay, r →∞ ,o f the to tal pair correlation functions h ij (r ) obtained from the Ornstein–Zernike route. The locus in the phase diagram of the crossover from monotonic to oscillatory decay of correlations is calculated for several size ratios q = R p/Rc ,w hereR p is the radius o ft hePolymer sphere and Rc that of the colloid. We determine the (mean-field) behaviour of the partial structure factors on approaching the fluid–fluid critical (consolute) point.
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entropic wetting and the fluid fluid interface of a model colloid Polymer Mixture
Journal of Physics: Condensed Matter, 2002Co-Authors: Joseph M Brader, Robert Evans, Matthias Schmidt, Hartmut LowenAbstract:A recent density functional theory is used to investigate the free interface between demixed fluid phases in a model colloid-Polymer Mixture. Both the colloid and Polymer density profiles oscillate on the colloid-rich side of the interface, provided the Polymer reservoir packing fraction ηpr is sufficiently high. Results for the surface tension are in reasonable agreement with experiment. When the Mixture is adsorbed against a hard wall, entropic depletion effects give rise to a wetting transition whereby the colloid-rich phase wets completely. Prior to complete wetting we find three layering transitions, the first of which extends far into the single-phase region. This pattern of surface phase transitions is very different from that observed for simple one-component fluids at planar substrates.