The Experts below are selected from a list of 252 Experts worldwide ranked by ideXlab platform
Gyorgy Tegze - One of the best experts on this subject based on the ideXlab platform.
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Hydrodynamic Theory of freezing: Nucleation and polycrystalline growth
Physical Review E, 2017Co-Authors: Frigyes Podmaniczky, Gyula Toth, Gyorgy Tegze, Laszlo GranasyAbstract:Structural aspects of crystal nucleation in undercooled liquids are explored using a nonlinear Hydrodynamic Theory of crystallization proposed recently [G. I. Toth et al., J. Phys.: Condens. Matter 26, 055001 (2014)], which is based on combining fluctuating Hydrodynamics with the phase-field crystal Theory. We show that in this Hydrodynamic approach not only homogeneous and heterogeneous nucleation processes are accessible, but also growth front nucleation, which leads to the formation of new (differently oriented) grains at the solid-liquid front in highly undercooled systems. Formation of dislocations at the solid-liquid interface and interference of density waves ahead of the crystallization front are responsible for the appearance of the new orientations at the growth front that lead to spherulite-like nanostructures.
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nonlinear Hydrodynamic Theory of crystallization
Journal of Physics: Condensed Matter, 2014Co-Authors: Gyula Toth, Laszlo Granasy, Gyorgy TegzeAbstract:We present an isothermal fluctuating nonlinear Hydrodynamic Theory of crystallization in molecular liquids. A dynamic coarse-graining technique is used to derive the velocity field, a phenomenology which allows a direct coupling between the free energy functional of the classical density functional Theory and the Navier‐Stokes equation. In contrast to the Ginzburg‐Landau type amplitude theories, the dynamic response to elastic deformations is described by parameter-free kinetic equations. Employing our approach to the free energy functional of the phase-field crystal model, we recover the classical spectrum for the phonons and the steady-state growth fronts. The capillary wave spectrum of the equilibrium crystal‐liquid interface is in good qualitative agreement with the molecular dynamics simulations. (Some figures may appear in colour only in the online journal)
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nonlinear Hydrodynamic Theory of crystallization
arXiv: Materials Science, 2013Co-Authors: Gyula Toth, Laszlo Granasy, Gyorgy TegzeAbstract:We present an isothermal fluctuating nonlinear Hydrodynamic Theory of crystallization in molecular liquids. A dynamic coarse-graining technique is used to derive the velocity field, a phenomenology, which allows a direct coupling between the free energy functional of the classical Density Functional Theory and the Navier-Stokes equation. Contrary to the Ginzburg-Landau type amplitude theories, the dynamic response to elastic deformations is described by parameter-free kinetic equations. Employing our approach to the free energy functional of the Phase-Field Crystal model, we recover the classical spectrum for the phonons and the steady-state growth fronts. The capillary wave spectrum of the equilibrium crystal-liquid interface is in a good qualitative agreement with the molecular dynamics simulations.
Sebastian Heidenreich - One of the best experts on this subject based on the ideXlab platform.
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Derivation of a Hydrodynamic Theory for mesoscale dynamics in microswimmer suspensions.
Physical review. E, 2020Co-Authors: Henning Reinken, Sabine H L Klapp, Sebastian HeidenreichAbstract:In this paper, we systematically derive a fourth-order continuum Theory capable of reproducing mesoscale turbulence in a three-dimensional suspension of microswimmers. We start from overdamped Langevin equations for a generic microscopic model (pushers or pullers), which include Hydrodynamic interactions on both small length scales (polar alignment of neighboring swimmers) and large length scales, where the solvent flow interacts with the order parameter field. The flow field is determined via the Stokes equation supplemented by an ansatz for the stress tensor. In addition to Hydrodynamic interactions, we allow for nematic pair interactions stemming from excluded-volume effects. The results here substantially extend and generalize earlier findings [S. Heidenreich et al., Phys. Rev. E 94, 020601 (2016)2470-004510.1103/PhysRevE.94.020601], in which we derived a two-dimensional Hydrodynamic Theory. From the corresponding mean-field Fokker-Planck equation combined with a self-consistent closure scheme, we derive nonlinear field equations for the polar and the nematic order parameter, involving gradient terms of up to fourth order. We find that the effective microswimmer dynamics depends on the coupling between solvent flow and orientational order. For very weak coupling corresponding to a high viscosity of the suspension, the dynamics of mesoscale turbulence can be described by a simplified model containing only an effective microswimmer velocity.
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derivation of a Hydrodynamic Theory for mesoscale dynamics in microswimmer suspensions
Physical Review E, 2018Co-Authors: Henning Reinken, Sabine H L Klapp, Sebastian HeidenreichAbstract:In this paper we systematically derive a fourth-order continuum Theory capable of reproducing mesoscale turbulence in a three-dimensional suspension of microswimmers. We start from overdamped Langevin equations for a generic microscopic model (pushers or pullers), which include Hydrodynamic interactions on both, small length scales (polar alignment of neighboring swimmers) and large length scales, where the solvent flow interacts with the order parameter field. The flow field is determined via the Stokes equation supplemented by an ansatz for the stress tensor. In addition to Hydrodynamic interactions, we allow for nematic pair interactions stemming from excluded-volume effects. The results here substantially extend and generalize earlier findings [Phys. Rev. E 94, 020601(R) (2016)], in which we derived a two-dimensional Hydrodynamic Theory. From the corresponding mean-field Fokker-Planck equation combined with a self-consistent closure scheme, we derive nonlinear field equations for the polar and the nematic order parameter, involving gradient terms of up to fourth order. We find that the effective microswimmer dynamics depends on the coupling between solvent flow and orientational order. For very weak coupling corresponding to a high viscosity of the suspension, the dynamics of mesoscale turbulence can be described by a simplified model containing only an effective microswimmer velocity.
Cristian Ciraci - One of the best experts on this subject based on the ideXlab platform.
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current dependent exchange correlation potential for non local absorption in quantum Hydrodynamic Theory
Physical Review B, 2017Co-Authors: Cristian CiraciAbstract:The quantum Hydrodynamic Theory is a promising method for describing microscopic details of macroscopic systems. The Hydrodynamic equation can be directly obtained from a single particle Kohn-Sham equation that includes the contribution of an external vector potential. This derivation allows to straightforwardly incorporate in the Hydrodynamic equation an exchange-correlation viscoelastic term, so that broadening of collective excitation can be taken into account, as well as a correction to the plasmon dispersion. The result is an accurate self-consistent and computationally efficient Hydrodynamic description of the free electron gas. A very accurate agreement with full quantum calculations is shown.
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quantum Hydrodynamic Theory for plasmonics impact of the electron density tail
Physical Review B, 2016Co-Authors: Cristian Ciraci, Fabio Della SalaAbstract:Multiscale plasmonic systems e.g. extended metallic nanostructures with sub-nanometer inter-distances) play a key role in the development of next-generation nano-photonic devices. An accurate modeling of the optical interactions in these systems requires an accurate description of both quantum effects and far-field properties. Classical electromagnetism can only describe the latter, while Time-Dependent Density Functional Theory (TD-DFT) can provide a full first-principles quantum treatment. However, TD-DFT becomes computationally prohibitive for sizes that exceed few nanometers, which are irrelevant for practical applications. In this article, we introduce a method based on the quantum Hydrodynamic Theory (QHT), which includes non-local contributions of the kinetic energy and the correct asymptotic description of the electron density. We show that our QHT method can predict both plasmon energy and spill-out effects in metal nanoparticles in excellent agreement with TD-DFT predictions, thus allowing a reliable and efficient calculations of both quantum and far-field properties in multiscale plasmonic systems.
Gyula Toth - One of the best experts on this subject based on the ideXlab platform.
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Hydrodynamic Theory of freezing: Nucleation and polycrystalline growth
Physical Review E, 2017Co-Authors: Frigyes Podmaniczky, Gyula Toth, Gyorgy Tegze, Laszlo GranasyAbstract:Structural aspects of crystal nucleation in undercooled liquids are explored using a nonlinear Hydrodynamic Theory of crystallization proposed recently [G. I. Toth et al., J. Phys.: Condens. Matter 26, 055001 (2014)], which is based on combining fluctuating Hydrodynamics with the phase-field crystal Theory. We show that in this Hydrodynamic approach not only homogeneous and heterogeneous nucleation processes are accessible, but also growth front nucleation, which leads to the formation of new (differently oriented) grains at the solid-liquid front in highly undercooled systems. Formation of dislocations at the solid-liquid interface and interference of density waves ahead of the crystallization front are responsible for the appearance of the new orientations at the growth front that lead to spherulite-like nanostructures.
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nonlinear Hydrodynamic Theory of crystallization
Journal of Physics: Condensed Matter, 2014Co-Authors: Gyula Toth, Laszlo Granasy, Gyorgy TegzeAbstract:We present an isothermal fluctuating nonlinear Hydrodynamic Theory of crystallization in molecular liquids. A dynamic coarse-graining technique is used to derive the velocity field, a phenomenology which allows a direct coupling between the free energy functional of the classical density functional Theory and the Navier‐Stokes equation. In contrast to the Ginzburg‐Landau type amplitude theories, the dynamic response to elastic deformations is described by parameter-free kinetic equations. Employing our approach to the free energy functional of the phase-field crystal model, we recover the classical spectrum for the phonons and the steady-state growth fronts. The capillary wave spectrum of the equilibrium crystal‐liquid interface is in good qualitative agreement with the molecular dynamics simulations. (Some figures may appear in colour only in the online journal)
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nonlinear Hydrodynamic Theory of crystallization
arXiv: Materials Science, 2013Co-Authors: Gyula Toth, Laszlo Granasy, Gyorgy TegzeAbstract:We present an isothermal fluctuating nonlinear Hydrodynamic Theory of crystallization in molecular liquids. A dynamic coarse-graining technique is used to derive the velocity field, a phenomenology, which allows a direct coupling between the free energy functional of the classical Density Functional Theory and the Navier-Stokes equation. Contrary to the Ginzburg-Landau type amplitude theories, the dynamic response to elastic deformations is described by parameter-free kinetic equations. Employing our approach to the free energy functional of the Phase-Field Crystal model, we recover the classical spectrum for the phonons and the steady-state growth fronts. The capillary wave spectrum of the equilibrium crystal-liquid interface is in a good qualitative agreement with the molecular dynamics simulations.
Qi Wang - One of the best experts on this subject based on the ideXlab platform.
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A Hydrodynamic Theory for solutions of nonhomogeneous nematic liquid crystalline polymers of different configurations
Journal of Chemical Physics, 2002Co-Authors: Qi WangAbstract:A Hydrodynamic Theory is developed for solutions of nonhomogeneous nematic liquid crystalline polymers (LCPs) of a variety of molecular configurations in proximity of spheroids, extending the Doi kinetic Theory for rodlike molecules. The new Theory accounts for the molecular aspect ratio as well as the finite range molecular interaction so that it is applicable to liquid crystals ranging from the rodlike liquid crystal at large aspect ratios to the discotic one at small aspect ratios. It also exhibits enhanced shape effects in the viscous stress and warrants a positive entropy production, thereby, the second law of thermodynamics. When restricted to uniaxial symmetry in the weak flow limit, the Theory recovers the director equation of the Leslie–Eriksen (LE) Theory, but the stress tensor contains excessive gradient terms in addition to the LE stress tensor. The Theory predicts that the elastic moduli K1, K2, and K3 obey the ordering K3
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a Hydrodynamic Theory for solutions of nonhomogeneous nematic liquid crystalline polymers of different configurations
Journal of Chemical Physics, 2002Co-Authors: Qi WangAbstract:A Hydrodynamic Theory is developed for solutions of nonhomogeneous nematic liquid crystalline polymers (LCPs) of a variety of molecular configurations in proximity of spheroids, extending the Doi kinetic Theory for rodlike molecules. The new Theory accounts for the molecular aspect ratio as well as the finite range molecular interaction so that it is applicable to liquid crystals ranging from the rodlike liquid crystal at large aspect ratios to the discotic one at small aspect ratios. It also exhibits enhanced shape effects in the viscous stress and warrants a positive entropy production, thereby, the second law of thermodynamics. When restricted to uniaxial symmetry in the weak flow limit, the Theory recovers the director equation of the Leslie–Eriksen (LE) Theory, but the stress tensor contains excessive gradient terms in addition to the LE stress tensor. The Theory predicts that the elastic moduli K1, K2, and K3 obey the ordering K3
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A Hydrodynamic Theory for solutions of nonhomogeneous nematic liquid crystalline polymers with density variations
Fluids Engineering, 2002Co-Authors: Qi Wang, M. Gregory Forest, Ruihai ZhouAbstract:The Hydrodynamic Theory developed in [31] for solutions of nonhomogeneous nematic liquid crystalline polymers (LCPs) of spheroidal molecular configurations is extended to account for translational diffusion and the related spatial density variation. The new Theory augments the added effect of the density variation to the Smoluchowski equation and the elastic stress. It accounts for the molecular aspect ratio as well as the finite range molecular interaction so that it is applicable to liquid crystals ranging from the rodlike liquid crystal at large aspect ratios to the discotic one at small aspect ratios. It also exhibits enhanced shape effects in the viscous stress and warrants a positive entropy production, thereby, the second law of thermodynamics. Moment averaged, approximate, mesoscopic theories for complex flow simulations are obtained via closure approximations.© 2002 ASME
