Showing papers on "Phase transition published in 1986"
TL;DR: In this paper, an irreversible kinetic surface-reaction model based on the reaction of carbon monoxide and oxygen on a catalyst surface was presented, and it was found by computer simulation that the adsorbed molecules on the surface undergo both first-and second-order kinetic phase transitions.
Abstract: An irreversible kinetic surface-reaction model, based upon the reaction of carbon monoxide and oxygen on a catalyst surface, is presented. It is found by computer simulation that the adsorbed molecules on the surface undergo both first- and second-order kinetic phase transitions. These transitions correspond to the "poisoning" phenomenon seen on catalysts. Interesting transient and periodic behavior is also seen.
784 citations
TL;DR: A general survey of glass transition phenomena and concepts is presented in an introductory section as discussed by the authors, and the physical significance of computer simulations of glass transitions in simple liquids and the question of a hidden phase transition underlying an observed glass transition are examined critically.
Abstract: The different physical aspects of glass transitions are reviewed and models aiming at their explanation are described. The following three main aspects are distinguished: the degree of stability of supercooled liquids with respect to crystallisation; the variation of physical properties of supercooled liquids in metastable equilibrium above the glass transition; the arrest of structural relaxation at the glass transition. The physical significance of computer simulations of glass transitions in simple liquids and the question of a hidden phase transition underlying an observed glass transition are examined critically. In relation to the stability problem, the geometrical constraints operative in typical disordered structures, such as random sphere packings and random covalent networks, are also discussed. A general survey of glass transition phenomena and concepts is presented in an introductory section.
777 citations
TL;DR: In this paper, a mathematical analysis of a new approach to solidification problems is presented, where a free boundary arising from a phase transition is assumed to have finite thickness, and the physics leads to a system of nonlinear parabolic differential equations.
Abstract: A mathematical analysis of a new approach to solidification problems is presented. A free boundary arising from a phase transition is assumed to have finite thickness. The physics leads to a system of nonlinear parabolic differential equations. Existence and regularity of solutions are proved. Invariant regions of the solution space lead to physical interpretations of the interface. A rigorous asymptotic analysis leads to the Gibbs-Thompson condition which relates the temperature at the interface to the surface tension and curvature.
740 citations
TL;DR: In this paper, sound velocities determined in liquid iron, shock compressed to pressures between 77 GPa and 400 GPa, indicate that two phase transitions exist on the Hugoniot.
Abstract: Sound velocities determined in iron, shock compressed to pressures between 77 GPa and 400 GPa, indicate that two phase transitions exist on the Hugoniot A discontinuity in sound velocities at 200 ± 2 GPa may mark the transition of e iron to γ iron A second discontinuity at 243 ± 2 GPa is believed to indicate the onset of melting The calculated temperature at melting lies between 5000 K and 5700 K When extrapolated from the Hugoniot melting point, the Lindemann criterion yields an estimate of 5800 ± 500 K for the melting of pure iron at the inner core boundary pressure of 330 GPa The product of density times the thermodynamic Gruneisen parameter in liquid iron, calculated from the present data, is 196 ± 08 Mg m−3 A temperature profile ranging from 3800 K at the core-mantle boundary to 5000 K at the earth's center is calculated using the present data Sound velocities for e iron provide a better match to seismic velocities for the earth's inner core than do those of γ iron A comparison between liquid iron velocities and the velocity profile through the outer core provides further evidence for alloying of iron with “lighter elements” in the core
652 citations
TL;DR: In this paper, an analytical result for a large population of limit-cycle oscillators modelled by a set of deterministic equations is obtained for a particular macroscopic solution of steady rotation, which branches off the trivial solution at some positive K. The present work is a generalization of the previous one where the study was limited to the case of vanishing a and symmetric distribution of Wi.
Abstract: Some analytical results are obtained for a large population of limit·cycle oscillators modelled by a set of deterministic equations 1>i = WiNK'2;/j~lsin(
476 citations
TL;DR: In this paper, the phase equilibria of a simple fluid confined by two adsorbing walls have been investigated as a function of wall separation H and chemical potential μ for temperature T corresponding to both partial and complete wetting situations.
Abstract: By means of a density functional approach the phase equilibria of a simple fluid confined by two adsorbing walls have been investigated as a function of wall separation H and chemical potential μ for temperature T corresponding to both partial and complete wetting situations. For large values of H and small undersaturations Δμ ≡ μsat−μ, we recover the macroscopic formulas for the undersaturation at which a first‐ order phase transition (capillary condensation) from dilute ‘‘gas’’ to a dense ‘‘liquid’’ occurs in a single, infinitely long slit. For smaller H we compute the lines of coexistence between gas and liquid in the (Δμ, 1/H) plane at fixed values of T. The adsorption Γ(Δμ), at fixed T and H, is characterized by a loop. At the first order transition Γ jumps discontinuously by a finite amount; however metastable states exist and these could give rise to hysteresis of the adsorption isotherms obtained for the single slit. The loop disappears at a capillary critical point (Δμc, 1/Hc) at each T. For H
464 citations
TL;DR: In this paper, the authors report the results of experiments on biological motion demonstrating the presence of critical order parameter fluctuations as the system evolves from one coordinated state to another at a critical control parameter value.
461 citations
TL;DR: The Ising model on a collection of all planar lattices with coordination number 4 is shown to be equivalent to the exactly solvable two-matrix model in the large N limit.
443 citations
TL;DR: The theory of a truly microscopic maser consisting of a single-mode high-Q resonator in which a monoenergetic beam of excited two-level atoms is injected at such a low flux that at most one atom at a time is present inside the cavity is presented.
Abstract: We present the theory of a truly microscopic maser consisting of a single-mode high-Q resonator in which a monoenergetic beam of excited two-level atoms is injected at such a low flux that at most one atom at a time is present inside the cavity. Both a microscopic theory and a heuristic Fokker-Planck approach are presented. We show that the micromaser exhibits a number of novel features that are averaged out in usual masers and lasers. First, the field is in general sub-Poissonian, which reflects the quantization of both the field and its sources. Second, the onset of maser oscillations may be followed by a succession of abrupt transitions in the state of the field. Finally, as the atomic flux through the resonator is increased, the maser threshold acquires characteristics of a continuous phase transition, whereas the subsequent changes in the field distribution become analogous to first-order phase transitions.
367 citations
TL;DR: In this article, a density functional approach is used to investigate the adsorption of simple fluids confined in model pores, and the authors show that at a given pore size, the adaption exhibits a loop and jumps discontinuously at the first-order phase transition, but the accompanying metastable portions of the loop could produce hysteresis.
Abstract: The nature of adsorption of simple fluids confined in model pores is investigated by means of a density functional approach. For temperatures T corresponding to a partial wetting situation a first-order phase transition (capillary condensation) from dilute ‘gas’ to dense ‘liquid’ occurs at relative pressures p/psat close to those predicted by the macroscopic Kelvin equation, even for radii Rc or wall separations H as small as 10 molecular diameters. In a complete wetting situation, where thick films develop, the Kelvin equation is, in general, not accurate. At fixed T the adsorption Γm(p) exhibits a loop; Γm jumps discontinuously at the first-order transition, but the accompanying metastable portions of the loop could produce hysteresis similar to that observed in adsorption measurements on mesoporous solids. Metastable thick films persist to larger p/psat in slits than in cylinders and this has repercussions for the shape of hysteresis loops. For a given pore size the loop in Γm shrinks with increasing T and disappears at a capillary critical temperature Tcapc( Tcapc condensation no longer occurs and hysteresis of Γm will not be observed. Such behaviour is found in experiments. A prewetting (thick–thin film) transition can occur for confined fluids. The transition is shifted to a smaller value of p/psat than that appropriate to prewetting at a single planar wall. Whereas the magnitude of the shift is very small for slits, it is substantial for cylinders and this leads to the possibility of finding a triple point, where ‘liquid’ and thick and thin films coexist, in cylindrical pores whose radii may not be too large for investigation by experiment or computer simulation. Adsorption of supercritical fluids (T > Tc, the bulk critical temperature) in cylinders is mentioned briefly.
361 citations
TL;DR: In this paper, the state-of-the-art in the observation and analytical description of localized electrostatic phase space structures is reviewed, and the controlling function of these nonlinearly excited d.c. states in the dynamical evolution of bounded plasmas exhibiting transient phenomena is discussed.
TL;DR: In this article, it is shown that properties of the theory at nonzero fermion density can be deduced from its behavior at finite imaginary chemical potential, and Monte Carlo simulations are proposed which would check these ideas.
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31 Jan 1986
TL;DR: In this article, the scaling properties of random fractuals were studied in the context of particle aggregation and scaling in a model of Cement Gels, and the results showed that the scaling of a model can be described as a function of the number of particles in the model.
Abstract: Random Fractuals: Characterization and Measurement.- to Scaling Concepts.- Growth by Particle Aggregation.- Fractal Concepts for Disordered Systems: The Interplay of Physics and Geometry.- Scaling Properties of Cluster and Particle Aggregation.- A Fractal Model for Charge Diffusion Across a Rough Interface.- Applications of Scaling and Disorderly Growth Phenomena to Oil Recovery.- A Reversible Reaction Limiting Step in Irreversible Immunoglobulin Aggregation.- Neutron and X-Ray Scattering from Aggregates.- Neutron and X-Ray Studies of Interfaces.- Light Scattering Experiments in a Gel Saturated with a Liquid Mixture.- Binary Fluid Phase Separation in Gels: A Neutron Scattering Study.- Metastability and Landau Theory for Random Fields and Demixing in Porous Media.- Scaling in Colloid Aggregation.- Possible Fractal Structure of Cement Gels.- Diffraction on Fractals.- Icosahedral Incommensurate Crystals.- Growth of Domains and Scaling in the Late Stages of Phase Separation and Diffusion-Controlled Ordering Phenomena.- First Order Phase Transformations: Scaling Relations for Grain Self-Correlation Functions.- Dynamical Scaling in a Model Structural Glass.- A Stochastic Model of Spin Glass Dynamics.- Cellular Automata and Condensed Matter Physics.- Fractal Geometry of Percolation in Thin Gold Films.- Anomalous Diffusion on Percolating Clusters.- Magnetic Properties near Percolation.- Fractal Properties of "Disordered Surfaces" and the Termite Problem.- Excitations of/on Fractal Networks.- Low Frequency Dynamics of Dilute Antiferromagnets at Percolation.- Phonon-Fracton Crossover on Fractal Lattices.- Grassmann Path Integral Approach to Two-Dimensional Percolation Near the Critical Point.- Geometry and Dynamics of Fractal Systems.- Quantum Percolation.- Nonlinear Resitor Fractal Networks.- Elastic Properties of Random Systems.- Elasticity and Percolation.- Scaling Concepts in Porous Media.- The Random Field Ising Model.- Metastability and a Temporal Phase Transition in the Random Field Ising Model.- Magnetic Excitation in K2CoxFe1?xF4: A Mixed Magnetic System withxCompeting Spin Anisotropies.- Spin Dynamics on Percolating Networks.- Dilution-Induced Critical Dynamics.- Scaling in Polymer Physics.- Dynamical Scaling in Polymer Solutions.- Scaling Description of Polymerization Kinetics.- Swelling of Branched Polymers.- Simulations of Polymers in Confined Geometries.- The Dimensions of Strange Attractors: A Survey of Experimental Studies.- Ergodic Renormalization and Universal Strange Attractors.- Computable Chaotic Orbits of Ergodic Dynamical Systems.- Fractal Structure of Subharmonic Steps in Dissipative Systems Described by a Driven Damped Pendulum Equation.- Participants.
TL;DR: In this paper, an effet peut etre caracterise par deux parametres, l'un decrivant l'augmentation du diametre effectif et l'autre l'action twistante.
Abstract: Cet effet peut etre caracterise par deux parametres, l'un decrivant l'augmentation du diametre effectif et l'autre, l'action twistante
TL;DR: In this article, the electrical resistivity, susceptibility, dc-Meissner effect and specific heat of the tetragonal U-compound URu2Si2 were measured.
Abstract: Measurements are reported on the electrical resistivity, susceptibility, dc-Meissner effect and specific heat of the tetragonal U-compound URu2Si2. At T N ≃17 K, an antiferromagnetic phase transition is observed. This magnetically ordered state appears to coexist with superconductivity, which is found below T c ≃1.5 K. An analysis of the upper critical field data reveals rather unusual properties of both the normal-and the superconducting state. The effective mass of the quasiparticles at low temperatures is substantially enhanced (m*≃50 m 0), though the measured low-temperature specific heat coefficient γ does not exceed 65 mJ/K2mol.
TL;DR: A review of the wide variety of predictions that results from a Landau-type of description of the nematic-isotropic phase transition is given in this paper, which includes a discussion of the nature of the order parameter and of the various types of possible phases.
TL;DR: In this paper, the authors discuss some of the experimental puzzles that prompted a development of new analytic approaches to chemisorption based on general principles such as perturbation theory (PT) and bond-order conservation (BOC).
TL;DR: In this article, a review of analytical and numerical work on confinement phase transitions in finite-temperature Abelian and non-Abelian gauge theories is presented, and the role of matter fields as symmetry-breaking perturbations is noted as important to the eventual unraveling of the phase structure of quantum chromodynamics.
TL;DR: Mesure de reflectivite RX a la surface libre du 12CB a la transition isotrope-smectique A a the-sauveur de 9.10°C au dessus de la transition.
Abstract: We report x-ray reflectivity measurements on the free surface of dodecylcyanobiphenyl (12CB) at the isotropic to smectic-A phase transition. At about 10?deC above ${\mathrm{T}}_{\mathrm{IA}}$, smectic-A-like ordering develops at the surface while the bulk phase remains isotropic. The angular dependence of the specular reflectivity is consistent with a sinusoidal density modulation, starting at the surface and terminating abruptly, after an integral number of bilayers. As the transition is approached the number of layers increases in quantized steps from zero to five before the bulk undergoes a first-order transition to the smectic-A phase.
TL;DR: At pressures higher than the isothermal liquid-crystalline to gel transition pressure, a new pressure-induced phase transition was observed for DPPC and DSPC in which the hydrocarbon chains from apposing monolayers become interdigitated with the chains occupying a cross-sectional area approximately equal to 5% less than in the gel phase.
Abstract: By use of neutron diffraction for structural analysis, the temperature-pressure phase diagrams of several fully hydrated single-component phospholipid bilayers have been explored up to hydrostatic pressures of 2 kbars. The gel to liquid-crystalline phase transition temperature Tm increases linearly with pressure over a 10(-3)-2 kbar range in accordance with the Clausius-Clapeyron relationship giving dTm/dP values of 23.0 degrees C/kbar for 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) and 28.0 degrees C/kbar for 1,2-distearoyl-sn-glycero-3-phosphatidylcholine (DSPC). The so-called pretransition was not observed in the isothermal pressure experiments, suggesting that no appreciable volume change occurs at this transition. These results are in good agreement with those reported using other techniques. In addition, at pressures higher than the isothermal liquid-crystalline to gel transition pressure, a new pressure-induced phase transition was observed for DPPC and DSPC in which the hydrocarbon chains from apposing monolayers become interdigitated with the chains occupying a cross-sectional area approximately equal to 5% less than in the gel phase. The temperature-pressure phase diagrams show the gel-interdigitated phase boundaries to be highly curved and the minimum pressure at which interdigitation occurs to decrease with increasing hydrocarbon chain length.
TL;DR: In this article, the authors compared the accuracies of the computed temperatures of a liquid in a corner region under freezing conditions with various fixed-grid finite element techniques using the analytical solution for this problem as a reference.
Abstract: The accuracies of the computed temperatures of a liquid in a corner region under freezing conditions are compared for various fixed-grid finite element techniques using the analytical solution for this problem as a reference.
In the finite element formulation of the problem different time-stepping schemes are compared: the implicit Euler-backward algorithm combined with an iterative scheme and two three-time-level methods—the Lees algorithm and a Dupont algorithm, which are both applied as non-iterative schemes.
Furthermore, different methods for handling the evolution of latent heat are examined: an approximation method suggested by Lemmon and one suggested by Del Giudice, both using the enthalpy formulation as well as a fictitious heat-flow method presented by Rolph and Bathe.
Results of calculations performed with the consistent heat-capacity matrix are compared with those performed with a lumped heat-capacity matrix.
TL;DR: It is shown that membrane fusion probably occurs via structures that form from these inverted micellar intermediates, and that fusion should occur in only a sub-set of lipid systems that can adopt the HII phase, and in lipid systems with L alpha----HII transitions driven by cation binding, fusion should be more frequent than in thermotropic systems.
TL;DR: In this article, the Lebwohl-Lasher model of nematogens has been investigated using Monte Carlo simulations with periodic boundary conditions on a 30 × 30 × × 30 lattice.
Abstract: The Lebwohl-Lasher model of nematogens consists of a system of particles placed at the sites of a cubic lattice and interacting with a pair potential U i,j = -ϵ ij P 2(cos β ij ), where ϵ ij is a positive constant, ϵ, for nearest neighbours particles i and j and β ij is the angle between the axis of these two molecules. We have investigated this model using Monte Carlo simulations with periodic boundary conditions on a 30 × 30 × 30 lattice while the largest system previously studied was 20 × 20 × 20. The number of simulation runs near the transition is also significantly higher than in previous simulations to allow a more precise determination of the orientational transition temperature T * NI. The transition temperature has been placed at kT/ϵ = 1·1232 ± 0·0006, refining previous estimates. Orientational order parameters , have been calculated and a new algorithm is proposed for the computation of . Particular attention has been devoted to pretransitional properties. Pair correlations G 2...
TL;DR: It is shown that there is a phase transition between the semimetal and metallic phases followed by a localization transition and the symmetry breaking associated with this transition is related to the nonsymmorphic character of the space group.
Abstract: A model that describes the qualitative properties of the electronic states of a disordered degenerate semiconductor with a finite number of degeneracy points is proposed. I introduce an effective Hamiltonian of the form of a Dirac operator coupled to randomly distributed fields. It is shown that there is a phase transition between the semimetal and metallic phases followed by a localization transition. The symmetry breaking associated with this transition is related to the nonsymmorphic character of the space group. The density of states plays the role of the order parameter and the elastic mean free path is the correlation length. A path-integral representation is introduced and used to characterize the universality class of this transition. The lower critical dimension is 2. A mapping of the two-dimensional case to one-dimensional self-interacting Fermi systems is presented. Applications to zero-gap semiconductors and other systems are discussed.
TL;DR: The emission of dileptons from a matter distribution undergoing longitudinal hydrodynamic expansion as might be produced in ultrarelativistic nuclear collisions is computed and it is found that the signals from quark-gluon plasma and pion gas probably exceed such background for sufficiently high initial temperature.
Abstract: The emission of dileptons from a matter distribution undergoing longitudinal hydrodynamic expansion as might be produced in ultrarelativistic nuclear collisions is computed. Contributions come from quark-gluon plasma, from pion gas, and from a mixed phase while the matter undergoes a first-order confinement phase transition. This yield is compared with that expected from other sources. It is found that the signals from quark-gluon plasma and pion gas probably exceed such background for sufficiently high initial temperature. The ratio of dilepton rapidity density to the square of the pion rapidity density may provide a measurement of the phase transition temperature. The dilepton mass distribution for various values of transverse energy may provide a measure of vector-meson masses as a function of temperature, and a mass shift due to the restoration of chiral symmetry might be seen.
TL;DR: A model for the thermotropic transitions between lamellar (L alpha) and inverted hexagonal (HII) phases is developed and it is shown that if only RMI form, L alpha in equilibrium HII transitions cannot occur on observed time scales (faster than seconds).
01 Jan 1986
TL;DR: In this article, an experimental study of phase transitions induced in polystyrene latices by hydroxyethylcellulose was conducted and the results were interpreted by applying perturbation theory from statistical mechanics to an interaction potential derived from the volume exclusion mechanism of Akasura and Oosawa.
Abstract: We present an experimental study of phase transitions induced in polystyrene latices by hydroxyethylcellulose and interpret the results by applying perturbation theory from statistical mechanics to an interaction potential derived from the volume exclusion mechanism of Akasura and Oosawa. The predictions agree semiquantitatively with the measured colloidal phase densities and the critical polymer concentration above which flocculation occurs for a wide range of ionic strengths. The theory also predicts the type of phase transition, i.e., fluid-solid or fluid-fluid, observed by Sperry. The agreement between experiment and theory demonstrates the predictive capability of the perturbation theory for weakly aggregating colloidal suspensions.
TL;DR: In this paper, the behaviour of a Lennard-Jones fluid confined within a straight cylindrical pore has been studied using mean-field theory, and the effect of varying the pore radius, pressure, temperature, and strength of the wall-fluid forces on these properties was examined.
Abstract: The behaviour of a Lennard-Jones fluid confined within a straight cylindrical pore has been studied using mean-field theory. The fluid potential parameters were chosen to model argon, and a range of wall–fluid parameters, including values approximating carbon dioxide and graphite walls, was investigated. We calculated the density profile and grand potential of the fluid, and examined the effect of varying the pore radius, pressure, temperature, and strength of the wall–fluid forces on these properties, and especially on the gas–liquid phase transitions that occur. We found that the gas–liquid transition occurs at pressures below the bulk fluid vapour pressure in all cases studied. For a fixed temperature, when the pore radius is decreased the gas–liquid coexistence curve ends in a critical point, as has been observed for fluids between parallel plates. The strength of the wall–fluid forces had a dramatic effect on the phase diagram, changing both the range of pore sizes in which phase transitions occur, and the effect of temperature on them.