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Sample records for temperature phase transition

  1. The Wilson flow and the finite temperature phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Wandelt, M. [Department of Mathematics, School of Mathematics and Natural Sciences,Bergische Universität Wuppertal, Gaußstr. 20, 42119 Wuppertal (Germany); Knechtli, F. [Department of Physics, School of Mathematics and Natural Sciences,Bergische Universität Wuppertal, Gaußstr. 20, 42119 Wuppertal (Germany); Günther, M. [Department of Mathematics, School of Mathematics and Natural Sciences,Bergische Universität Wuppertal, Gaußstr. 20, 42119 Wuppertal (Germany)

    2016-10-12

    We consider the determination of the finite temperature phase transition in the Yang-Mills SU(3) gauge theory. We compute the difference of the spatial and temporal energy density at a physical Wilson flow time. This difference is zero in the confined phase and becomes non zero in the deconfined phase. We locate the phase transition by using a new technique based on an exponential smoothing spline. This method is an alternative to the determination of the phase transition based on the Polyakov loop susceptibility and can also be used with dynamical fermions.

  2. luminous transmittance and phase transition temperature of vo2:ce ...

    African Journals Online (AJOL)

    nb

    A two-step increase in transmittance observed in the cooling loop in pure VO2 was found to be suppressed by cerium inclusion. Keywords: vanadium dioxide, luminous transmittance, phase transition temperature. INTRODUCTION. Discovery of novel behavior of vanadium dioxide to undergo a metal-to-insulator phase.

  3. Luminous transmittance and phase transition temperature of VO 2 ...

    African Journals Online (AJOL)

    The phase transition temperature (τc) of the films was obtained from both the transmittance and sheet resistance against temperature curves. A change in sheet resistance of 2 to 3 orders of magnitude was observed for both undoped and Ce-doped VO2 films. Comparison between undoped and doped VO2 films revealed ...

  4. luminous transmittance and phase transition temperature of vo2:ce ...

    African Journals Online (AJOL)

    nb

    68 oC accompanied by dramatic changes in electrical and optical properties has attracted intensive research in this thermochromic material. The phase transition in VO2 has been tailored to suit various applications in devices such as smart.

  5. Low-temperature structural phase transition in deuterated and protonated lithium acetate dihydrate

    Energy Technology Data Exchange (ETDEWEB)

    Schroeder, F., E-mail: schroeder@kristall.uni-frankfurt.d [Goethe-Universitaet Frankfurt am Main, Institut fuer Geowissenschaften, Abt. Kristallographie, Altenhoeferallee 1, 60438 Frankfurt am Main (Germany); Winkler, B.; Haussuehl, E. [Goethe-Universitaet Frankfurt am Main, Institut fuer Geowissenschaften, Abt. Kristallographie, Altenhoeferallee 1, 60438 Frankfurt am Main (Germany); Cong, P.T.; Wolf, B. [Goethe-Universitaet Frankfurt am Main, Physikalisches Institut, Max-von-Laue-Strasse 1, 60438 Frankfurt am Main (Germany); Avalos-Borja, M. [Instituto Potosino de Investigacion Cientifica y Tecnologica, A.C. Camino a la Presa San Jose 2055, Col. Lomas 4 seccion CP 78216, San Luis Potosi (Mexico); Quilichini, M.; Hennion, B. [Laboratoire Leon Brillouin, CEN Saclay, 91191 Gif-sur-Yvette (France)

    2010-08-15

    Heat capacity measurements of protonated lithium acetate dihydrate show a structural phase transition at T = 12 K. This finding is in contrast to earlier work, where it was thought that only the deuterated compound undergoes a low temperature structural phase transition. This finding is confirmed by low temperature ultrasound spectroscopy, where the structural phase transition is associated with a velocity decrease of the ultrasonic waves, i.e. with an elastic softening. We compare the thermodynamic properties of the protonated and deuterated compounds and discuss two alternatives for the mechanism of the phase transition based on the thermal expansion measurements.

  6. Determining magnetic phase transitions temperatures in working magnetocaloric coolers bodies and gas cryorefrigerators regenerators

    Science.gov (United States)

    Karagusov, V. I.; Mayankov, I. V.

    2017-08-01

    Due to magnetic phase transitions rare-earth materials possess unique properties near the Curie and Neel temperatures, such as the magneto-caloric effect, the abnormally high heat capacity, the magnetic susceptibility and permeability extremes. Using rare earth materials in gas cryogenic refrigerators regenerators increases the efficiency, reduces the power consumption and allows reaching helium temperatures. The magneto-caloric effect has also extreme values near the Curie and Neel temperatures. The paper presents theoretical and experimental methods allowing to determine magnetic phase transitions temperatures in a wide range of low temperature materials with a various rare-earth components content and expected thermophysical properties of a certain rare-earth materials composition at the temperatures based on starting pure metals characteristics. The results analysis has shown that magnetic phase transitions temperatures are a linear function of the components concentration. Moreover, heat capacity values and MCE also depend linearly on the starting components concentration, which simplifies calculations significantly.

  7. A phase transition close to room temperature in BiFeO3 thin films.

    Science.gov (United States)

    Kreisel, J; Jadhav, P; Chaix-Pluchery, O; Varela, M; Dix, N; Sánchez, F; Fontcuberta, J

    2011-08-31

    BiFeO3 (BFO) multiferroic oxide has a complex phase diagram that can be mapped by using appropriately substrate-induced strain in epitaxial films. By using Raman spectroscopy, we conclusively show that films of the so-called supertetragonal T-BFO phase, stabilized under compressive strain, display a reversible temperature-induced phase transition at about 100 °C, and thus close to room temperature.

  8. A phase transition close to room temperature in BiFeO{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kreisel, J; Jadhav, P; Chaix-Pluchery, O [Laboratoire des Materiaux et du Genie Physique, Grenoble INP, CNRS, Minatec, 3, parvis Louis Neel, 38016 Grenoble (France); Varela, M [Departamento Fisica Aplicada i Optica, Universitat de Barcelona, Carrer MartI i Franques 1. 08028 Campus UAB, Bellaterra 08193 (Spain); Dix, N; Sanchez, F; Fontcuberta, J, E-mail: jens.kreisel@grenoble-inp.fr [Institut de Ciencia de Materials de Barcelona (ICMAB-CSIC), Campus UAB, Bellaterra 08193 (Spain)

    2011-08-31

    BiFeO{sub 3} (BFO) multiferroic oxide has a complex phase diagram that can be mapped by using appropriately substrate-induced strain in epitaxial films. By using Raman spectroscopy, we conclusively show that films of the so-called supertetragonal T-BFO phase, stabilized under compressive strain, display a reversible temperature-induced phase transition at about 100 deg. C, and thus close to room temperature. (fast track communication)

  9. Quantum phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Sachdev, S. [Yale University, New Haven, CT (United States)

    1999-04-01

    Phase transitions are normally associated with changes of temperature but a new type of transition - caused by quantum fluctuations near absolute zero - is possible, and can tell us more about the properties of a wide range of systems in condensed-matter physics. Nature abounds with phase transitions. The boiling and freezing of water are everyday examples of phase transitions, as are more exotic processes such as superconductivity and superfluidity. The universe itself is thought to have passed through several phase transitions as the high-temperature plasma formed by the big bang cooled to form the world as we know it today. Phase transitions are traditionally classified as first or second order. In first-order transitions the two phases co-exist at the transition temperature - e.g. ice and water at 0 deg., or water and steam at 100 deg. In second-order transitions the two phases do not co-exist. In the last decade, attention has focused on phase transitions that are qualitatively different from the examples noted above: these are quantum phase transitions and they occur only at the absolute zero of temperature. The transition takes place atthe ''quantum critical'' value of some other parameter such as pressure, composition or magnetic field strength. A quantum phase transition takes place when co-operative ordering of the system disappears, but this loss of order is driven solely by the quantum fluctuations demanded by Heisenberg's uncertainty principle. The physical properties of these quantum fluctuations are quite distinct from those of the thermal fluctuations responsible for traditional, finite-temperature phase transitions. In particular, the quantum system is described by a complex-valued wavefunction, and the dynamics of its phase near the quantum critical point requires novel theories that have no analogue in the traditional framework of phase transitions. In this article the author describes the history of quantum phase

  10. Magnetic and Structural Phase Transitions in Thulium under High Pressures and Low Temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Vohra, Yogesh K.; Tsoi, Georgiy M.; Samudrala, Gopi K. [UAB

    2017-10-01

    The nature of 4f electrons in many rare earth metals and compounds may be broadly characterized as being either "localized" or "itinerant", and is held responsible for a wide range of physical and chemical properties. The pressure variable has a very dramatic effect on the electronic structure of rare earth metals which in turn drives a sequence of structural and magnetic transitions. We have carried out four-probe electrical resistance measurements on rare earth metal Thulium (Tm) under high pressures to 33 GPa and low temperatures to 10 K to monitor the magnetic ordering transition. These studies are complemented by angle dispersive x-ray diffraction studies to monitor crystallographic phase transitions at high pressures and low temperatures. We observe an abrupt increase in magnetic ordering temperature in Tm at a pressure of 17 GPa on phase transition from ambient pressure hcp-phase to α-Sm phase transition. In addition, measured equation of state (EOS) at low temperatures show anomalously low thermal expansion coefficients likely linked to magnetic transitions.

  11. Magnetic and Structural Phase Transitions in Thulium under High Pressures and Low Temperatures

    Science.gov (United States)

    Vohra, Yogesh K.; Tsoi, Georgiy M.; Samudrala, Gopi K.

    2017-10-01

    The nature of 4f electrons in many rare earth metals and compounds may be broadly characterized as being either “localized” or “itinerant”, and is held responsible for a wide range of physical and chemical properties. The pressure variable has a very dramatic effect on the electronic structure of rare earth metals which in turn drives a sequence of structural and magnetic transitions. We have carried out four-probe electrical resistance measurements on rare earth metal Thulium (Tm) under high pressures to 33 GPa and low temperatures to 10 K to monitor the magnetic ordering transition. These studies are complemented by angle dispersive x-ray diffraction studies to monitor crystallographic phase transitions at high pressures and low temperatures. We observe an abrupt increase in magnetic ordering temperature in Tm at a pressure of 17 GPa on phase transition from ambient pressure hcp-phase to α-Sm phase transition. In addition, measured equation of state (EOS) at low temperatures show anomalously low thermal expansion coefficients likely linked to magnetic transitions.

  12. Structural stability and phase transition of Bi 2 Te 3 under high pressure and low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, J. L.; Zhang, S. J.; Zhu, J. L.; Liu, Q. Q.; Wang, X. C.; Jin, C. Q.; Yu, J. C.

    2017-09-01

    Structural stability and phase transition of topological insulator Bi2Te3 were studied via angle-dispersive synchrotron radiation X-ray diffraction under high pressure and low temperature condition. The results manifest that the R-3m phase (phase I) is stable at 8 K over the pressure range up to 10 GPa and phase transition occurs between 8 K and 45 K at 8 GPa. According to the Birch-Murnaghan equation of state, the bulk modulus at ambient pressure B0 was estimated to be 45 ± 3 GPa with the assumption of B0' = 4. The structural robustness of phase I at 8 K suggests that the superconductivity below 10 GPa is related to phase I. Topological properties of superconducting Bi2Te3 phase under pressure were discussed.

  13. Finite temperature spin-dynamics and phase transitions in spin-orbital models

    Energy Technology Data Exchange (ETDEWEB)

    Chen, C.-C.

    2010-04-29

    We study finite temperature properties of a generic spin-orbital model relevant to transition metal compounds, having coupled quantum Heisenberg-spin and Ising-orbital degrees of freedom. The model system undergoes a phase transition, consistent with that of a 2D Ising model, to an orbitally ordered state at a temperature set by short-range magnetic order. At low temperatures the orbital degrees of freedom freeze-out and the model maps onto a quantum Heisenberg model. The onset of orbital excitations causes a rapid scrambling of the spin spectral weight away from coherent spin-waves, which leads to a sharp increase in uniform magnetic susceptibility just below the phase transition, reminiscent of the observed behavior in the Fe-pnictide materials.

  14. Optical nonlinearities of nanostructured VO{sub 2} thin films with low phase transition temperature

    Energy Technology Data Exchange (ETDEWEB)

    Wang Boqing [Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074 (China); Chen Sihai, E-mail: cshai99@163.com [Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074 (China); Huang Zhangli; Fu Ming [Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2012-05-01

    Vanadium dioxides (VO{sub 2}) thin films which change from a monoclinic semiconductor phase to a tetragonal metallic structure at the temperature of 29 Degree-Sign C have been fabricated by reactive ion beam sputtering. Micrograph of scanning electron microscope (SEM) shows that the grain size of VO{sub 2} crystallite ranges from 20 nm to 50 nm. Regeneratively amplified Ti:sapphire laser pulses were applied to induce the phase transition, which was accompanying with the third-order optical nonlinearities in VO{sub 2} thin films. Open-aperture and closed-aperture measurements of Z-scan were used to study the optical absorptive and refractive nonlinearities. Nanostructured VO{sub 2} thin films exhibit two-photon absorption and a negative nonlinear index of refraction when phase transition is induced. The optical nonlinearities are due to excitation of electronic subsystem only and without involving of the structural semiconductor-to-metal phase transition.

  15. Holographic s+p insulator/superconductor phase transition at zero temperature

    Directory of Open Access Journals (Sweden)

    Ran Li

    2017-03-01

    Full Text Available We study the holographic s+p insulator/superconductor phase transition at zero temperature by using the model with a scalar triplet charged under an SU(2 gauge field in anti-de Sitter (AdS soliton background. In this model, besides the insulator phase, s-wave condensate phase and p-wave condensate phase, the s+p coexisting condensate phase is found numerically when operator dimension Δ is greater than a critical value Δc. We also construct the complete phase diagram in Δ−μ plane, which shows the s+p coexisting region is very narrow. Furthermore, we calculate the corresponding conductivities for different phases. The delta function support for the real part of conductivity of the spontaneous breaking phases is also revealed numerically as expected for the superconducting phases.

  16. Low temperature electroweak phase transition in the Standard Model with hidden scale invariance

    Directory of Open Access Journals (Sweden)

    Suntharan Arunasalam

    2018-01-01

    Full Text Available We discuss a cosmological phase transition within the Standard Model which incorporates spontaneously broken scale invariance as a low-energy theory. In addition to the Standard Model fields, the minimal model involves a light dilaton, which acquires a large vacuum expectation value (VEV through the mechanism of dimensional transmutation. Under the assumption of the cancellation of the vacuum energy, the dilaton develops a very small mass at 2-loop order. As a result, a flat direction is present in the classical dilaton-Higgs potential at zero temperature while the quantum potential admits two (almost degenerate local minima with unbroken and broken electroweak symmetry. We found that the cosmological electroweak phase transition in this model can only be triggered by a QCD chiral symmetry breaking phase transition at low temperatures, T≲132 MeV. Furthermore, unlike the standard case, the universe settles into the chiral symmetry breaking vacuum via a first-order phase transition which gives rise to a stochastic gravitational background with a peak frequency ∼10−8 Hz as well as triggers the production of approximately solar mass primordial black holes. The observation of these signatures of cosmological phase transitions together with the detection of a light dilaton would provide a strong hint of the fundamental role of scale invariance in particle physics.

  17. Low temperature electroweak phase transition in the Standard Model with hidden scale invariance

    Science.gov (United States)

    Arunasalam, Suntharan; Kobakhidze, Archil; Lagger, Cyril; Liang, Shelley; Zhou, Albert

    2018-01-01

    We discuss a cosmological phase transition within the Standard Model which incorporates spontaneously broken scale invariance as a low-energy theory. In addition to the Standard Model fields, the minimal model involves a light dilaton, which acquires a large vacuum expectation value (VEV) through the mechanism of dimensional transmutation. Under the assumption of the cancellation of the vacuum energy, the dilaton develops a very small mass at 2-loop order. As a result, a flat direction is present in the classical dilaton-Higgs potential at zero temperature while the quantum potential admits two (almost) degenerate local minima with unbroken and broken electroweak symmetry. We found that the cosmological electroweak phase transition in this model can only be triggered by a QCD chiral symmetry breaking phase transition at low temperatures, T ≲ 132 MeV. Furthermore, unlike the standard case, the universe settles into the chiral symmetry breaking vacuum via a first-order phase transition which gives rise to a stochastic gravitational background with a peak frequency ∼10-8 Hz as well as triggers the production of approximately solar mass primordial black holes. The observation of these signatures of cosmological phase transitions together with the detection of a light dilaton would provide a strong hint of the fundamental role of scale invariance in particle physics.

  18. Time evolution of chiral phase transition at finite temperature and density in the linear sigma model

    Energy Technology Data Exchange (ETDEWEB)

    Sato, K.; Koide, Tomoi; Maruyama, Masahiro [Tohoku Univ., Faculty of Science, Sendai, Miyagi (Japan)

    1999-08-01

    There are various approaches to nonequilibrium system. We use the projection operator method investigated by F. Shibata and N. Hashitsume on the linear sigma model at finite temperature and density. We derive a differential equation of the time evolution for the order parameter and pion number density in chiral phase transition. (author)

  19. Interplay between quantum phase transitions and the behavior of quantum correlations at finite temperatures

    OpenAIRE

    Werlang, T.; Ribeiro, G. A. P.; Rigolin, Gustavo

    2012-01-01

    We review the main results and ideas showing that quantum correlations at finite temperatures (T), in particular quantum discord, are useful tools in characterizing quantum phase transitions that only occur, in principle, at the unattainable absolute zero temperature. We first review some interesting results about the behavior of thermal quantum discord for small spin-1/2 chains and show that they already give us important hints of the infinite chain behavior. We then study in detail and in t...

  20. Low-temperature structure anomalies in CuNCN. Manifestations of RVB phase transitions?

    Science.gov (United States)

    Tchougréeff, A L; Dronskowski, R

    2013-10-30

    We propose a new frustrated Heisenberg antiferromagnetic model with spatially anisotropic exchange parameters Jc, Ja, and Jac, extending along the c, a, and a ± c (c-a-ca model) lattice directions, and apply it to describe the fascinating physics of copper carbodiimide, CuNCN, assuming the resonating valence bond (RVB) type of its phases. This explains within a unified picture the intriguing absence of magnetic order in CuNCN. We further present a parameters-temperature phase diagram of the c-a-ca-RVB model in the high-temperature approximation. Eight different phases including Curie and Pauli paramagnets (respectively, in disordered and 1D- or Q1D-RVB phases) and (pseudo)gapped (quasi-Arrhenius) paramagnets (2D-RVB phases) are possible. By adding magnetostriction and elastic terms to the model, we derive possible structural manifestations of RVB phase transitions. Assuming a sequence of RVB phase transitions to occur in CuNCN with decreasing temperature, several anomalies observed in the temperature course of the lattice constants are explained.

  1. Martensitic phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Petry, W.; Neuhaus, J. [Techn. Universitaet Muenchen, Physik Department E13, Munich (Germany)

    1996-11-01

    Many elements transform from a high temperature bcc phase to a more dense packed temperature phase. The great majority of these transitions are of 1st order, displacive and reconstructive. The lattice potentials which govern these martensitic transitions can be probed by inelastic neutron scattering, thereby answering fundamental questions like : Will the transition be announced by dynamical or static fluctuations? What are the trajectories for the displacements needed for the transformation? Does the vibrational entropy stabilize the high temperature phase? Are the unusual transport properties in these materials related to their ability to transform? (author) 17 figs., 1 tab., 46 refs.

  2. Structural phase transitions in ionic conductor Bi2O3 by temperature dependent XPD and XAS

    Science.gov (United States)

    Zhu, Yingcai; An, Pengfei; Yu, Meijuan; Marcelli, Augusto; Liu, Yong; Hu, Tiandou; Xu, Wei

    2016-05-01

    The superionic behavior of cubic δ-phase Bi2O3, a metastable phase at high temperature, is of great interests from both scientific and technological perspectives. With the highest ionic conductivity among all known compounds, the δ-phase Bi2O3 possesses promising applications in solid-oxide fuel cells. Previous investigations pointed out the α to δ- phase transition occurs during the heating process, as supported by the X-ray and Neutron diffraction experiments. Through in situ measurements of the long-range order structure and the local structure by X-ray powder diffraction and X-ray absorption spectroscopy, we investigated the evolution of the structures under different temperatures. Both techniques provided ample evidence that the existence of meta-stable β-phase are crucial for forming the defective fluorite cubic δ phase. Our finding suggested that the phase transition from tetragonal β-phase to δ-phase is an influencing factor for the generation of the oxygen-ion pathways.

  3. Relaxation theory of spin-3/2 Ising system near phase transition temperatures

    Science.gov (United States)

    Osman, Canko; Mustafa, Keskin

    2010-08-01

    Dynamics of a spin-3/2 Ising system Hamiltonian with bilinear and biquadratic nearest-neighbour exchange interactions is studied by a simple method in which the statistical equilibrium theory is combined with the Onsager's theory of irreversible thermodynamics. First, the equilibrium behaviour of the model in the molecular-field approximation is given briefly in order to obtain the phase transition temperatures, i.e. the first- and second-order and the tricritical points. Then, the Onsager theory is applied to the model and the kinetic or rate equations are obtained. By solving these equations three relaxation times are calculated and their behaviours are examined for temperatures near the phase transition points. Moreover, the z dynamic critical exponent is calculated and compared with the z values obtained for different systems experimentally and theoretically, and they are found to be in good agrement.

  4. Temperature-driven topological quantum phase transitions in a phase-change material Ge2Sb2Te5.

    Science.gov (United States)

    Eremeev, S V; Rusinov, I P; Echenique, P M; Chulkov, E V

    2016-12-13

    The Ge2Sb2Te5 is a phase-change material widely used in optical memory devices and is a leading candidate for next generation non-volatile random access memory devices which are key elements of various electronics and portable systems. Despite the compound is under intense investigation its electronic structure is currently not fully understood. The present work sheds new light on the electronic structure of the Ge2Sb2Te5 crystalline phases. We demonstrate by predicting from first-principles calculations that stable crystal structures of Ge2Sb2Te5 possess different topological quantum phases: a topological insulator phase is realized in low-temperature structure and Weyl semimetal phase is a characteristic of the high-temperature structure. Since the structural phase transitions are caused by the temperature the switching between different topologically non-trivial phases can be driven by variation of the temperature. The obtained results reveal the rich physics of the Ge2Sb2Te5 compound and open previously unexplored possibility for spintronics applications of this material, substantially expanding its application potential.

  5. Spatially resolved quantitative mapping of thermomechanical properties and phase transition temperatures using scanning probe microscopy

    Science.gov (United States)

    Jesse, Stephen; Kalinin, Sergei V; Nikiforov, Maxim P

    2013-07-09

    An approach for the thermomechanical characterization of phase transitions in polymeric materials (polyethyleneterephthalate) by band excitation acoustic force microscopy is developed. This methodology allows the independent measurement of resonance frequency, Q factor, and oscillation amplitude of a tip-surface contact area as a function of tip temperature, from which the thermal evolution of tip-surface spring constant and mechanical dissipation can be extracted. A heating protocol maintained a constant tip-surface contact area and constant contact force, thereby allowing for reproducible measurements and quantitative extraction of material properties including temperature dependence of indentation-based elastic and loss moduli.

  6. Circulatory osmotic desalination driven by a mild temperature gradient based on lower critical solution temperature (LCST) phase transition materials.

    Science.gov (United States)

    Mok, Yeongbong; Nakayama, Daichi; Noh, Minwoo; Jang, Sangmok; Kim, Taeho; Lee, Yan

    2013-11-28

    Abrupt changes in effective concentration and osmotic pressure of lower critical solution temperature (LCST) mixtures facilitate the design of a continuous desalination method driven by a mild temperature gradient. We propose a prototype desalination system by circulating LCST mixtures between low and high temperature (low T and high T) units. Water molecules could be drawn from a high-salt solution to the LCST mixture through a semipermeable membrane at a temperature lower than the phase transition temperature, at which the effective osmotic pressure of the LCST mixture is higher than the high-salt solution. After transfer of water to the high T unit where the LCST mixture is phase-separated, the water-rich phase could release the drawn water into a well-diluted solution through the second membrane due to the significant decrease in effective concentration. The solute-rich phase could be recovered in the low T unit via a circulation process. The molar mass, phase transition temperature, and aqueous solubility of the LCST solute could be tuneable for the circulatory osmotic desalination system in which drawing, transfer, release of water, and the separation and recovery of the solutes could proceed simultaneously. Development of a practical desalination system that draws water molecules directly from seawater and produces low-salt water with high purity by mild temperature gradients, possibly induced by sunlight or waste heat, could be attainable by a careful design of the molecular structure and combination of the circulatory desalination systems based on low- and high-molar-mass LCST draw solutes.

  7. Quasi-dynamic pressure and temperature initiated βδ solid phase transitions in HMX

    Science.gov (United States)

    Zaug, Joseph M.; Farber, Daniel L.; Craig, Ian M.; Blosch, Laura L.; Shuh, David K.; Hansen, Donald W.; Aracne-Ruddle, Chantel M.

    2000-04-01

    The phase transformation of β-HMX (>0.5% RDX) to δ phase has been studied for over twenty years and more recently with an high-contrast optical second harmonic generation technique. Shock studies of the plastic binder composites of HMX have indicated that the transition is perhaps irreversible, a result that concurs with the static pressure results published by F. Goetz et al. [1] in 1978. However, the stability field favors the β polymorph over δ as pressure is increased (up to 5.4 GPa) along any thermodynamically reasonable isotherm. In this experiment, strict control of pressure and temperature is maintained while x-ray and optical diagnostics are applied to monitor the conformational dynamics of HMX. Unlike the temperature induced β→δ transition, the pressure induced is heterogeneous in nature. The 1 bar 25 °C δ→β transition is not immediate, occuring over tens of hours. Transition points and kinetics are path dependent and consequently this paper describes our work in progress.

  8. THE SEMICONDUCTOR THERMOELECTRIC DEVICE FOR TEMPERATURE CONTROL OF COMPUTER PROCESSOR WITH USE OF MATERIALS IN THE CONDITION OF PHASE TRANSITION

    Directory of Open Access Journals (Sweden)

    H. M. Gadjiyev

    2015-01-01

    Full Text Available The article deals with the cooling system computer processor on the based sublimation phase transitions, allowing to provide temperature control mode in a transient thermal load, which will prevent the failure of the VLSI processor. 

  9. Phase transitions modern applications

    CERN Document Server

    Gitterman, Moshe

    2014-01-01

    This book provides a comprehensive review of the theory of phase transitions and its modern applications, based on the five pillars of the modern theory of phase transitions i.e. the Ising model, mean field, scaling, renormalization group and universality. This expanded second edition includes, along with a description of vortices and high temperature superconductivity, a discussion of phase transitions in chemical reaction and moving systems. The book covers a close connection between phase transitions and small world phenomena as well as scale-free systems such as the stock market and the Internet. Readership: Scientists working in different fields of physics, chemistry, biology and economics as well as teaching material for undergraduate and graduate courses.

  10. Dynamics of phase transitions at finite temperatures in the early universe.

    Science.gov (United States)

    Patzelt, H.

    1991-12-01

    A statistical description of phase transitions on a macroscopic, phenomenological level is used to treat the dynamics of phase transitions and the dynamics of an expanding universe simultaneously. The author considers phase transitions with non-vanishing background densities. The ratio of the typical interaction time to the typical expansion time suggests two scenarios that are discussed concerning their influence on the evolution of the universe.

  11. Low Temperature Phase Transitions in Single Crystal Magnetoelectric GdMnO3

    Science.gov (United States)

    Williamsen, Mark; Ray, Shishir; Sen, Somaditya; Zou, Ying; Guptasarma, Prasenjit

    2009-03-01

    GdMnO3 is proposed to have a magnetic phase transition from paramagnet to incommensurate antiferromagnet at 43K, further ordering to canted antiferromagnetism around 23K, followed by Gd magnetic ordering at 6.5K[1]. We present further studies of a large single crystal of orthorhombic GdMnO3 grown by us from a floating zone, revealing additional features at lower temperature. Dielectric spectroscopy measurements confirm these new features. We also report dc-magnetization, frequency dependent ac-magnetization 2-300K, and specific heat 0.4-300K in a variable magnetic field 0-9T, and propose additional features in the magnetoelectric phase diagram. [1]T. Kimura,Phys.Rev.B 71,224425(2005)

  12. Temperature dependence of the magneto-controllable first-order phase transition in dilute magnetic fluids

    Science.gov (United States)

    Ivanov, A. S.

    2017-11-01

    Experimental study was carried out to investigate the influence of particle size distribution function on the temperature dependent magneto-controllable first-order phase transition of the ;gas-liquid; type in magnetic fluids. The study resolves one crisis situation in ferrohydrodynamic experiment made by several research groups in the 1980-1990s. It is shown that due to polydispersity magnetic fluids exhibit phase diagrams which are divided into three regions by vaporus and liquidus curves. Granulometric data states the primary role of the width of the particle size distribution function in the process of spinodal decomposition. New modified Langevin parameter is introduced for unification of liquidus curves of different ferrofluids despite the significant difference between the curves (one order of magnitude) in (H, T) coordinates.

  13. High-temperature nuclear magnetic resonance study of phase transition kinetics in LiNaSO{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Shakhovoy, R. A., E-mail: roman.shakhovoy@cnrs-orleans.fr, E-mail: r.a.shakhovoy@gmail.com; Sarou-Kanian, V.; Rakhmatullin, A.; Véron, E.; Bessada, C. [CNRS, CEMHTI UPR 3079, Univ. Orléans, F-45071 Orléans (France)

    2015-12-28

    A new high-temperature NMR technique for measurements of the phase transition kinetics in solids has been developed. The technique allows measuring the time evolution of the volume of the appearing phase at controlled cooling rates. Developed method was applied to study the phase transition kinetics in the superionic conductor LiNaSO{sub 4}. It was revealed that the phase transition in LiNaSO{sub 4} is governed by the diffusion-controlled growth of nuclei (“germs”). An effect of the crystallite rearrangement in the LiNaSO{sub 4} powder after cooling through the phase transition was also revealed. This effect was studied by means of high-temperature XRD and NMR.

  14. Size Dependence of a Temperature-Induced Solid-Solid Phase Transition in Copper(I) Sulfide

    Energy Technology Data Exchange (ETDEWEB)

    Rivest, Jessy B; Fong, Lam-Kiu; Jain, Prashant K; Toney, Michael F; Alivisatos, A Paul

    2011-07-24

    Determination of the phase diagrams for the nanocrystalline forms of materials is crucial for our understanding of nanostructures and the design of functional materials using nanoscale building blocks. The ability to study such transformations in nanomaterials with controlled shape offers further insight into transition mechanisms and the influence of particular facets. Here we present an investigation of the size-dependent, temperature-induced solid-solid phase transition in copper sulfide nanorods from low- to high-chalcocite. We find the transition temperature to be substantially reduced, with the high chalcocite phase appearing in the smallest nanocrystals at temperatures so low that they are typical of photovoltaic operation. Size dependence in phase trans- formations suggests the possibility of accessing morphologies that are not found in bulk solids at ambient conditions. These other- wise-inaccessible crystal phases could enable higher-performing materials in a range of applications, including sensing, switching, lighting, and photovoltaics.

  15. Electroweak phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Gregory W. [Univ. of California, Berkeley, CA (United States)

    1991-09-16

    An analytic treatment of the one Higgs doublet, electroweak phase transition is given. The phase transition is first order, occurs by the nucleation of thin walled bubbles and completes at a temperature where the order parameter, <Φ>T is significantly smaller than it is when the origin becomes absolutely unstable. The rate of anomalous baryon number violation is an exponentially function of <Φ>T. In very minimal extensions of the standard model it is quite easy to increase <Φ>T so that anomalous baryon number violation is suppressed after completion of the phase transition. Hence baryogenesis at the electroweak phase transition is tenable in minimal of the standard model. In some cases additional phase transitions are possible. For a light Higgs boson, when the top quark mass is sufficiently large, the state where the Higgs field has a vacuum expectation value <Φ> = 246 GeV is not the true minimum of the Higgs potential. When this is the case, and when the top quark mass exceeds some critical value, thermal fluctuations in the early universe would have rendered the state <Φ> = 246 GeV unstable. The requirement that the state <Φ> = 246 GeV is sufficiently long lived constrains the masses of the Higgs boson and the top quark. Finally, we consider whether local phase transitions can be induced by heavy particles which act as seeds for deformations in the scalar field.

  16. Substrate effects on photoluminescence and low temperature phase transition of methylammonium lead iodide hybrid perovskite thin films

    Science.gov (United States)

    Shojaee, S. A.; Harriman, T. A.; Han, G. S.; Lee, J.-K.; Lucca, D. A.

    2017-07-01

    We examine the effects of substrates on the low temperature photoluminescence (PL) spectra and phase transition in methylammonium lead iodide hybrid perovskite (CH3NH3PbI3) thin films. Structural characterization at room temperature with X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy indicated that while the chemical structure of films deposited on glass and quartz was similar, the glass substrate induced strain in the perovskite films and suppressed the grain growth. The luminescence response and phase transition of the perovskite thin films were studied by PL spectroscopy. The induced strain was found to affect both the room temperature and low temperature PL spectra of the hybrid perovskite films. In addition, it was found that the effects of the glass substrate inhibited a tetragonal to orthorhombic phase transition such that it occurred at lower temperatures.

  17. Phase transitions and steady-state microstructures in a two-temperature lattice-gas model with mobile active impurities

    DEFF Research Database (Denmark)

    Henriksen, Jonas Rosager; Sabra, Mads Christian; Mouritsen, Ole G.

    2000-01-01

    The nonequilibrium, steady-state phase transitions and the structure of the different phases of a two-dimensional system with two thermodynamic temperatures are studied via a simple lattice-gas model with mobile active impurities ("hot/cold spots'') whose activity is controlled by an external drive....... The properties of the model are calculated by Monte Carlo computer-simulation techniques. The two temperatures and the external drive on the system lead to a rich phase diagram including regions of microstructured phases in addition to macroscopically ordered (phase-separated) and disordered phases. Depending...

  18. Summation of all petal-shaped diagrams in O(N) model near the phase transition temperature

    CERN Document Server

    Bordag, M

    2002-01-01

    The temperature phase transition in the theory of the N-component scalar field is studied. The weak phase transition of the first order is obtained in the approximation of summation of all petal-shaped diagrams. By the N -> infinity it becomes the phase transition of the second order. The comparison with other approaches is carried out. The necessary data on the Legendre transformation of the second order and Schwinger-Dyson equations are presented. The gap equations are solved in the approximation of summation of all petal-shaped diagrams for the arbitrary N

  19. Transition metal doping of GaSe implemented with low temperature liquid phase growth

    Science.gov (United States)

    Lei, Nuo; Sato, Youhei; Tanabe, Tadao; Maeda, Kensaku; Oyama, Yutaka

    2017-02-01

    Our group works on improving the conversion efficiencies of terahertz (THz) wave generation using GaSe crystals. The operating principle is based on difference frequency generation (DFG) which has the advantages such as high output power, a single tunable frequency, and room temperature operation. In this study, GaSe crystals were grown by the temperature difference method under controlled vapor pressure (TDM-CVP). It is a liquid phase growth method with temperature 300 °C lower than that of the Bridgman method. Using this method, the point defects concentration is decreased and the polytype can be controlled. The transition metal Ti was used to dope the GaSe in order to suppress free carrier absorption in the low frequency THz region. As a result, a deep acceptor level of 38 meV was confirmed as being formed in GaSe with 1.4 at% Ti doping. Compared with undoped GaSe, a decrease in carrier concentration ( 1014 cm-3) at room temperature was also confirmed. THz wave transmittance measurements reveal the tendency for the absorption coefficient to increase as the amount of dopant is increased. It is expected that there is an optimum amount of dopant.

  20. Live cell plasma membranes do not exhibit a miscibility phase transition over a wide range of temperatures.

    Science.gov (United States)

    Lee, Il-Hyung; Saha, Suvrajit; Polley, Anirban; Huang, Hector; Mayor, Satyajit; Rao, Madan; Groves, Jay T

    2015-03-26

    Lipid/cholesterol mixtures derived from cell membranes as well as their synthetic reconstitutions exhibit well-defined miscibility phase transitions and critical phenomena near physiological temperatures. This suggests that lipid/cholesterol-mediated phase separation plays a role in the organization of live cell membranes. However, macroscopic lipid-phase separation is not generally observed in cell membranes, and the degree to which properties of isolated lipid mixtures are preserved in the cell membrane remain unknown. A fundamental property of phase transitions is that the variation of tagged particle diffusion with temperature exhibits an abrupt change as the system passes through the transition, even when the two phases are distributed in a nanometer-scale emulsion. We support this using a variety of Monte Carlo and atomistic simulations on model lipid membrane systems. However, temperature-dependent fluorescence correlation spectroscopy of labeled lipids and membrane-anchored proteins in live cell membranes shows a consistently smooth increase in the diffusion coefficient as a function of temperature. We find no evidence of a discrete miscibility phase transition throughout a wide range of temperatures: 14-37 °C. This contrasts the behavior of giant plasma membrane vesicles (GPMVs) blebbed from the same cells, which do exhibit phase transitions and macroscopic phase separation. Fluorescence lifetime analysis of a DiI probe in both cases reveals a significant environmental difference between the live cell and the GPMV. Taken together, these data suggest the live cell membrane may avoid the miscibility phase transition inherent to its lipid constituents by actively regulating physical parameters, such as tension, in the membrane.

  1. High temperature phase transition of mixed (PuO2 + ThO2) investigated by laser melting

    NARCIS (Netherlands)

    Böhler, R.; Cakir, P.; Benes, O.; Hein, H.; Konings, R.J.M.; Manara, D.

    2014-01-01

    A laser heating approach combined with fast pyrometry in a thermal arrest method was used to provide new data for the melting/solidification phase transition in mixed (PuO2 + ThO2) at high temperature. At low concentration of ThO2 in PuO2 a minimum in the solidification temperature in the pseudo

  2. Renormalization group theory for temperature-driven first-order phase transitions in scalar models

    Science.gov (United States)

    Liang, Ning; Zhong, Fan

    2017-12-01

    We study the scaling and universal behavior of temperature-driven first-order phase transitions in scalar models. These transitions are found to exhibit rich phenomena, though they are controlled by a single complex-conjugate pair of imaginary fixed points of ϕ 3 theory. Scaling theories and renormalization group theories are developed to account for the phenomena, and three universality classes with their own hysteresis exponents are found: a field-like thermal class, a partly thermal class, and a purely thermal class, designated, respectively, as Thermal Classes I, II, and III. The first two classes arise from the opposite limits of the scaling forms proposed and may cross over to each other depending on the temperature sweep rate. They are both described by a massless model and a purely massive model, both of which are equivalent and are derived from ϕ 3 theory via symmetry. Thermal Class III characterizes the cooling transitions in the absence of applied external fields and is described by purely thermal models, which include cases in which the order parameters possess different symmetries and thus exhibit different universality classes. For the purely thermal models whose free energies contain odd-symmetry terms, Thermal Class III emerges only at the mean-field level and is identical to Thermal Class II. Fluctuations change the model into the other two models. Using the extant three- and two-loop results for the static and dynamic exponents for the Yang-Lee edge singularity, respectively, which falls into the same universality class as ϕ 3 theory, we estimate the thermal hysteresis exponents of the various classes to the same precision. Comparisons with numerical results and experiments are briefly discussed.

  3. Understanding quantum phase transitions

    CERN Document Server

    Carr, Lincoln

    2010-01-01

    Quantum phase transitions (QPTs) offer wonderful examples of the radical macroscopic effects inherent in quantum physics: phase changes between different forms of matter driven by quantum rather than thermal fluctuations, typically at very low temperatures. QPTs provide new insight into outstanding problems such as high-temperature superconductivity and display fundamental aspects of quantum theory, such as strong correlations and entanglement. Over the last two decades, our understanding of QPTs has increased tremendously due to a plethora of experimental examples, powerful new numerical meth

  4. Non-equilibrium phase transitions in the two-temperature Ising model with Kawasaki dynamics. Phase diagram from position space renormalization group transformation

    Science.gov (United States)

    Renklioglu, B.; Yalabik, M. C.

    2012-12-01

    Phase transitions of the two-finite temperature Ising model on a square lattice are investigated by using a position space renormalization group (PSRG) transformation. Different finite temperatures, T x and T y , and also different time-scale constants, α x and α y for spin exchanges in the x and y directions define the dynamics of the non-equilibrium system. The critical surface of the system is determined by RG flows as a function of these exchange parameters. The Onsager critical point (when the two temperatures are equal) and the critical temperature for the limit when the other temperature is infinite, previously studied by the Monte Carlo method, are obtained. In addition, two steady-state fixed points which correspond to the non-equilibrium phase transition are presented. These fixed points yield the different universality class properties of the non-equilibrium phase transitions.

  5. Electroweak phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, G.W.

    1991-09-16

    An analytic treatment of the one Higgs doublet, electroweak phase transition is given. The phase transition is first order, occurs by the nucleation of thin walled bubbles and completes at a temperature where the order parameter, {l angle}{phi}{r angle}{sub T} is significantly smaller than it is when the origin becomes absolutely unstable. The rate of anomalous baryon number violation is an exponentially function of {l angle}{phi}{r angle}{sub T}. In very minimal extensions of the standard model it is quite easy to increase {l angle}{phi}{r angle}{sub T} so that anomalous baryon number violation is suppressed after completion of the phase transition. Hence baryogenesis at the electroweak phase transition is tenable in minimal of the standard model. In some cases additional phase transitions are possible. For a light Higgs boson, when the top quark mass is sufficiently large, the state where the Higgs field has a vacuum expectation value {l angle}{phi}{r angle} = 246 GeV is not the true minimum of the Higgs potential. When this is the case, and when the top quark mass exceeds some critical value, thermal fluctuations in the early universe would have rendered the state {l angle}{phi}{r angle} = 246 GeV unstable. The requirement that the state {l angle}{phi}{r angle} = 246 GeV is sufficiently long lived constrains the masses of the Higgs boson and the top quark. Finally, we consider whether local phase transitions can be induced by heavy particles which act as seeds for deformations in the scalar field.

  6. High-temperature phase transitions, spectroscopic properties, and dimensionality reduction in rubidium thorium molybdate family.

    Science.gov (United States)

    Xiao, Bin; Gesing, Thorsten M; Kegler, Philip; Modolo, Giuseppe; Bosbach, Dirk; Schlenz, Hartmut; Suleimanov, Evgeny V; Alekseev, Evgeny V

    2014-03-17

    Four new rubidium thorium molybdates have been synthesized by high-temperature solid-state reactions. The crystal structures of Rb8Th(MoO4)6, Rb2Th(MoO4)3, Rb4Th(MoO4)4, and Rb4Th5(MoO4)12 were determined using single-crystal X-ray diffraction. All these compounds construct from MoO4 tetrahedra and ThO8 square antiprisms. The studied compounds adopt the whole range of possible structure dimensionalities from zero-dimensional (0D) to three-dimensional (3D): finite clusters, chains, sheets, and frameworks. Rb8Th(MoO4)6 crystallizes in 0D containing clusters of [Th(MoO4)6](8-). The crystal structure of Rb2Th(MoO4)3 is based upon one-dimensional chains with configuration units of [Th(MoO4)3](2-). Two-dimensional sheets occur in compound Rb4Th(MoO4)4, and a 3D framework with channels formed by thorium and molybdate polyhedra has been observed in Rb4Th5(MoO4)12. The Raman and IR spectroscopic properties of these compounds are reported. Temperature-depended phase transition effects were observed in Rb2Th(MoO4)3 and Rb4Th(MoO4)4 using thermogravimetry-differential scanning calorimetry analysis and high-temperature powder diffraction methods.

  7. A room temperature reversible phase transition containing dielectric switching of a host-guest supramolecular metal-halide compound.

    Science.gov (United States)

    Lu, Yang; Hua, Xiu-Ni; Liao, Wei-Qiang; Gao, Ji-Xing; Yin, Zi

    2017-10-03

    Following our recent findings on dielectric materials, we synthesized a new host-guest supramolecular metal-halide compound, [(2-AMPD)(18-crown-6)]CuCl4 (1, 2-AMPD = 2-aminomethylpiperidinium). Systematic characterization techniques such as variable-temperature crystal structure analyses, differential scanning calorimetry (DSC) measurements, temperature-dependent dielectric measurements and powder X-ray diffraction (PXRD) measurements demonstrate that 1 undergoes a reversible phase transition at room temperature, accompanied by switchable dielectric responses and remarkable anisotropy along three different crystallographic axes. The structural phase transition mechanism is triggered by the order-disorder transition of the 18-crown-6 molecules. We believe that these findings might further promote the application of a host-guest inclusion compound in the field of switchable dielectric materials.

  8. The finite temperature phase transition in the lattice SU(2)-Higgs model

    CERN Document Server

    Farakos, K; Rummukainen, K; Shaposhnikov, Mikhail E

    1994-01-01

    We study the finite temperature transition of SU(2)-Higgs model with lattice Monte Carlo techniques. We use dimensional reduction to transform the original 4-dimensional SU(2)-gauge + fundamental Higgs theory to an effective 3-dimensional SU(2) + adjoint Higgs + fundamental Higgs model. The simulations were performed with Higgs masses of 35 and 80 GeV; in both cases we observe a stronger first order transition than the perturbation theory predicts, indicating that the dynamics of the transition strongly depend on non-perturbative effects.

  9. Terbium-Doped VO2 Thin Films: Reduced Phase Transition Temperature and Largely Enhanced Luminous Transmittance.

    Science.gov (United States)

    Wang, Ning; Duchamp, Martial; Dunin-Borkowski, Rafal E; Liu, Shiyu; Zeng, XianTing; Cao, Xun; Long, Yi

    2016-01-26

    Vanadium dioxide (VO2) is a well-known thermochromic material with large IR modulating ability, promising for energy-saving smart windows. The main drawbacks of VO2 are its high phase transition temperature (τ(c) = 68°C), low luminous transmission (T(lum)), and weak solar modulating ability (ΔT(sol)). In this paper, the terbium cation (Tb(3+)) doping was first reported to reduce τ(c) and increase T(lum) of VO2 thin films. Compared with pristine VO2, 2 at. % doping level gives both enhanced T(lum) and ΔT(sol) from 45.8% to 54.0% and 7.7% to 8.3%, respectively. The T(lum) increases with continuous Tb(3+) doping and reaches 79.4% at 6 at. % doping level, representing ∼73.4% relative increment compared with pure VO2. This has surpassed the best reported doped VO2 thin films. The enhanced thermochromic properties is meaningful for smart window applications of VO2 materials.

  10. Vanadium dioxide thin film with low phase transition temperature deposited on borosilicate glass substrate

    Energy Technology Data Exchange (ETDEWEB)

    Huang Zhangli; Chen Sihai, E-mail: cshai99@mail.hust.edu.cn; Wang Boqing; Huang Ying; Liu Nengfu; Xu Jin; Lai Jianjun

    2011-04-29

    A nanostructured vanadium dioxide (VO{sub 2}) thin film showing a low metal-insulator transition temperature of 30 {sup o}C has been fabricated through reactive ion beam sputtering followed by thermal annealing. The thin film was grown on borosilicate glass substrate at the temperature of 280 {sup o}C with a Si{sub 3}N{sub 4} buffer layer. Both scanning electron microscopy and atomic force microscopy images have been taken to investigate the configuration of VO{sub 2} thin film. The average height of the crystallite is 20 nm and the grain size ranges from 40 nm to 100 nm. The transmittance measured from low to high temperatures also reveals that the film possesses excellent switching property in infrared light at critical transition temperature, with switching efficiency of 52% at 2600 nm. This experiment paves the way of VO{sub 2} thin film's application in smart windows.

  11. Phase transitions in Cd3P2 at high pressures and high temperatures

    DEFF Research Database (Denmark)

    Yel'kin, F.S.; Sidorov, V.A.; Waskowska, A.

    2008-01-01

    The high-pressure, high-temperature structural behaviour of Cd3P2 has been studied using electrical resistance measurements, differential thermal analysis, thermo baric analysis and X-ray diffraction. At room temperature, a phase transformation is observed at 4.0 GPa in compression....... The experimental zero-pressure bulk modulus of the low-pressure phase is 64.7(7) GPa, which agrees quite well with the calculated value of 66.3 GPa using the tight-binding linear muffin-tin orbital method within the local density approximation. Tentatively, the high-pressure phase has an orthorhombic crystal...

  12. Bismuth doping strategies in GeTe nanowires to promote high-temperature phase transition from rhombohedral to face-centered cubic structure

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jie; Huang, Rong; Wei, Fenfen; Cheng, Guosheng, E-mail: gscheng2006@sinano.ac.cn [Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, 398 Ruoshui Road, Suzhou Industrial Park, Jiangsu 215123 (China); University of Chinese Academy of Sciences, No.19A Yuquan Road, Beijing 100049 (China); Kong, Tao [Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, 398 Ruoshui Road, Suzhou Industrial Park, Jiangsu 215123 (China)

    2014-11-17

    The phase transition of Bi-doped (∼3 at. %) GeTe nanowires from a rhombohedral (R) to a face-centered cubic (C) structure was observed in in situ high-temperature X-ray diffraction. The promotion of high-temperature R-C phase transition by a doping approach was revealed. Ab initio energy calculations of doped GeTe at various Bi doping concentrations were performed to interpret the promoted temperature-induced phase transitions. Those results indicated that the total energy differences between R and C structures of doped GeTe decreased as Bi doping concentrations increased, which facilitated R-C phase transitions.

  13. Cosmological phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Kolb, E.W. [Fermi National Accelerator Lab., Batavia, IL (United States)]|[Chicago Univ., IL (United States)

    1993-10-01

    If modern ideas about the role of spontaneous symmetry breaking in fundamental physics are correct, then the Universe should have undergone a series of phase transitions early in its history. The study of cosmological phase transitions has become an important aspect of early-Universe cosmology. In this lecture I review some very recent work on three aspects of phase transitions: the electroweak transition, texture, and axions.

  14. Mechanism of dehydroxylation temperature decrease and high temperature phase transition of coal-bearing strata kaolinite intercalated by potassium acetate.

    Science.gov (United States)

    Cheng, Hongfei; Liu, Qinfu; Cui, Xiaonan; Zhang, Qian; Zhang, Zhiliang; Frost, Ray L

    2012-06-15

    The thermal decomposition and dehydroxylation process of coal-bearing strata kaolinite-potassium acetate intercalation complex (CSKK) has been studied using X-ray diffraction (XRD), infrared spectroscopy (IR), thermal analysis, mass spectrometric analysis and infrared emission spectroscopy. The XRD results showed that the potassium acetate (KAc) have been successfully intercalated into coal-bearing strata kaolinite with an obvious basal distance increase of the first basal peak, and the positive correlation was found between the concentration of intercalation regent KAc and the degree of intercalation. As the temperature of the system is raised, the formation of KHCO(3), KCO(3) and KAlSiO(4), which is derived from the thermal decomposition or phase transition of CSKK, is observed in sequence. The IR results showed that new bands appeared, the position and intensities shift can also be found when the concentration of intercalation agent is raised. The thermal analysis and mass spectrometric analysis results revealed that CSKK is stable below 300°C, and the thermal decomposition products (H(2)O and CO(2)) were further proved by the mass spectrometric analysis. A comparison of thermal analysis results of original coal-bearing strata kaolinite and its intercalation complex gives new discovery that not only a new mass loss peak is observed at 285 °C, but also the temperature of dehydroxylation and dehydration of coal bearing strata kaolinite is decreased about 100 °C. This is explained on the basis of the interlayer space of the kaolinite increased obviously after being intercalated by KAc, which led to the interlayer hydrogen bonds weakened, enables the dehydroxylation from kaolinite surface more easily. Furthermore, the possible structural model for CSKK has been proposed, with further analysis required in order to prove the most possible structures. Copyright © 2012 Elsevier Inc. All rights reserved.

  15. From a Single-Band Metal to a High-Temperature Superconductor via Two Thermal Phase Transitions

    Energy Technology Data Exchange (ETDEWEB)

    He, R.-H.; Hashimoto, M.; Karapetyan, H.; Koralek, J.D.; Hinton, J.P.; Testaud, J.P.; Nathan, V.; Yoshida, Y.; Yao, H.; Tanaka, K.; Meevasana, W.; Moore, R.G.; Lu, D.H.; Mo, S.-K.; Ishikado, M.; Eisaki, H.; Hussain, Z.; Devereaux, T.P.; Kivelson, S.A.; Orenstein, J.; Kapitulnik, A.

    2011-11-08

    The nature of the pseudogap phase of cuprate high-temperature superconductors is one of the most important unsolved problems in condensed matter physics. We studied the commencement of the pseudogap state at temperature T* using three different techniques (angle-resolved photoemission spectroscopy, polar Kerr effect, and time-resolved reflectivity) on the same optimally-doped Bi2201 crystals. We observe the coincident onset at T* of a particle-hole asymmetric antinodal gap, a non-zero Kerr rotation, and a change in the relaxational dynamics, consistent with a phase transition. Upon further cooling, spectroscopic signatures of superconductivity begin to grow close to the superconducting transition temperature (T{sub c}), entangled in an energy-momentum dependent fashion with the pre-existing pseudogap features.

  16. Magnetic Phase Transition in Rare Earth Metal Holmium at Low Temperatures and High Pressures

    Science.gov (United States)

    Thomas, Sarah; Uhoya, Walter; Wenger, Lowell; Vohra, Yogesh

    2012-02-01

    The heavy rare earth metal Holmium has been studied under high pressures and low temperatures using a designer diamond anvil cell and neutron diffraction using a Paris-Edinburgh Cell at the Spallation Neutrons and Pressure (SNAP) Diffractometer. The electrical resistance measurement using designer diamond shows a change in slope at the Neel temperature as the temperature is lowered at high pressures. At atmospheric pressure TN=120 K and decreases with a slope of -4.7 K/GPa as pressure is increased, until reaching 9 GPa, at which pressure the magnetic ordering is lost. This correlates to the pressure at which there is a structural change from an hcp phase to an α-Sm structure. Neutron diffraction measurements made above and below the Neel temperature at increasing pressures show the reversibility of the change between the paramagnetic and antiferromagnetic states. The parameters of the low temperature incommensurate magnetic phase will be reported at various pressures.

  17. Observation of reduced phase transition temperature in N-doped thermochromic film of monoclinic VO2

    Science.gov (United States)

    Wan, Meinan; Xiong, Mo; Li, Neng; Liu, Baoshun; Wang, Shuo; Ching, Wai-Yim; Zhao, Xiujian

    2017-07-01

    Research on monoclinic (M1) phase of VO2 has attracted a great of interest for smart coating applications due to its exceptional thermochromic property. Herein, we report the results using a novel approach to synthesize N-doped VO2(M1) thin films with high purity by heat treatment in NH3 atmosphere. The N dopant in the film can be regulated by varying NH3 concentration during the annealing process. We find that the N atoms are located at the interstitial sites or substitute oxygen atoms, and the V-N bonds in the VO2 thin films increase with NH3 concentration. The metal to insulator transition (MIT) temperature (τc,h) of the VO2 thin film is effectively reduced from 80.0 to 62.9 °C, while the solar modulation efficiency (ΔTsol) and the modulation efficiency at 2000 nm (ΔT2000nm) are 7.36% and 55.6% respectively. The band gap of N-doped VO2 thin films related to MIT (Eg1) is estimated to be as low as 0.18-0.25 eV whereas the band gap associated with the visible transparency (Eg2) is about 1.50-1.58 eV. Based on the highly accurate first-principles calculations, the Eg1 of VO2 (M1) is reduced after substituted or interstitial N-doping, while the Eg2 alters with the mode of N-doping, which is excellent agreement with experimental measurement.

  18. Phase stabilization of magnetite (Fe3O4) nanoparticles with B2O3 addition: A significant enhancement on the phase transition temperature

    Science.gov (United States)

    Topal, Uğur; Aksan, Mehmet Ali

    2016-05-01

    Magnetite nanoparticles (MNPs) are extensively investigated for biomedical applications, particularly as contrast agents for Magnetic Resonance Imaging and as drug delivery agent and heat mediators for cancer therapy. Tuning the magnetic properties of the magnetite nanoparticles with doping of foreign atoms has a crucial importance for determining the application areas of these materials and so attracts much interests. On the other hand the doping with foreign atoms requires high temperature annealing, and it causes a phase transition to the hematite phase above 400 °C. In this work the phase transition temperature from the magnetite to the hematite phase has been increased by 200 °C, which is the highest enhancement reported in literature. It was achieved by addition of the appropriate amounts of B2O3. Our experiments indicates that the 5.0 wt% of B2O3 addition stabilizes and keeps the existence of single phase magnetite up to 600 °C.

  19. Phase transition analysis of V-shaped liquid crystal: Combined temperature-dependent FTIR and density functional theory approach.

    Science.gov (United States)

    Singh, Swapnil; Singh, Harshita; Karthick, T; Tandon, Poonam; Prasad, Veena

    2018-01-05

    Temperature-dependent Fourier transform infrared spectroscopy (FTIR) combined with density functional theory (DFT) is employed to study the mechanism of phase transitions of V-shaped bent-core liquid crystal. Since it has a large number of flexible bonds, one-dimensional potential energy scan (PES) was performed on the flexible bonds and predicted the most stable conformer I. A detailed analysis of vibrational normal modes of conformer I have been done on the basis of potential energy distribution. The good agreement between the calculated spectrum of conformer I and observed FTIR spectrum at room temperature validates our theoretical structure model. Furthermore, the prominent changes observed in the stretching vibrational bands of CH3/CH2, CO, ring CC, ring CO, ring CH in-plane bending, and ring CH out-of-plane bending at Iso→nematic phase transition (at 155°C) have been illustrated. However, the minor changes in the spectral features observed for the other phase transitions might be due to the shape or bulkiness of molecules. Combined FTIR and PES study beautifully explained the dynamics of the molecules, molecular realignment, H-bonding, and conformational changes at the phase transitions. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Phase transition analysis of V-shaped liquid crystal: Combined temperature-dependent FTIR and density functional theory approach

    Science.gov (United States)

    Singh, Swapnil; Singh, Harshita; Karthick, T.; Tandon, Poonam; Prasad, Veena

    2018-01-01

    Temperature-dependent Fourier transform infrared spectroscopy (FTIR) combined with density functional theory (DFT) is employed to study the mechanism of phase transitions of V-shaped bent-core liquid crystal. Since it has a large number of flexible bonds, one-dimensional potential energy scan (PES) was performed on the flexible bonds and predicted the most stable conformer I. A detailed analysis of vibrational normal modes of conformer I have been done on the basis of potential energy distribution. The good agreement between the calculated spectrum of conformer I and observed FTIR spectrum at room temperature validates our theoretical structure model. Furthermore, the prominent changes observed in the stretching vibrational bands of CH3/CH2, Cdbnd O, ring CC, ring CO, ring CH in-plane bending, and ring CH out-of-plane bending at Iso → nematic phase transition (at 155 °C) have been illustrated. However, the minor changes in the spectral features observed for the other phase transitions might be due to the shape or bulkiness of molecules. Combined FTIR and PES study beautifully explained the dynamics of the molecules, molecular realignment, H-bonding, and conformational changes at the phase transitions.

  1. Temperature-dependent Raman and ultraviolet photoelectron spectroscopy studies on phase transition behavior of VO{sub 2} films with M1 and M2 phases

    Energy Technology Data Exchange (ETDEWEB)

    Okimura, Kunio, E-mail: okifn@keyaki.cc.u-tokai.ac.jp; Hanis Azhan, Nurul [Graduate School of Engineering, Tokai University, Hiratsuka 259-1292 (Japan); Hajiri, Tetsuya [UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585 (Japan); Graduate School of Engineering, Nagoya University, Nagoya 464-8603 (Japan); Kimura, Shin-ichi [UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585 (Japan); Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871 (Japan); Zaghrioui, Mustapha; Sakai, Joe [GREMAN, UMR 7347 CNRS, Université François Rabelais de Tours, Parc de Grandmont, 37200 Tours (France)

    2014-04-21

    Structural and electronic phase transitions behavior of two polycrystalline VO{sub 2} films, one with pure M1 phase and the other with pure M2 phase at room temperature, were investigated by temperature-controlled Raman spectroscopy and ultraviolet photoelectron spectroscopy (UPS). We observed characteristic transient dynamics in which the Raman modes at 195 cm{sup −1} (V-V vibration) and 616 cm{sup −1} (V-O vibration) showed remarkable hardening along the temperature in M1 phase film, indicating the rearrangements of V-V pairs and VO{sub 6} octahedra. It was also shown that the M1 Raman mode frequency approached those of invariant M2 peaks before entering rutile phase. In UPS spectra with high energy resolution of 0.03 eV for the M2 phase film, narrower V{sub 3d} band was observed together with smaller gap compared to those of M1 phase film, supporting the nature of Mott insulator of M2 phase even in the polycrystalline film. Cooperative behavior of lattice rearrangements and electronic phase transition was suggested for M1 phase film.

  2. The influence of temperature induced phase transition on the energy storage density of anti-ferroelectric ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Yi, Jinqiao; Zhang, Ling; Xie, Bing; Jiang, Shenglin, E-mail: nanx1013@163.com [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2015-09-28

    Anti-ferroelectric (AFE) composite ceramics of (Pb{sub 0.858}Ba{sub 0.1}La{sub 0.02}Y{sub 0.008})(Zr{sub 0.65}Sn{sub 0.3}Ti{sub 0.05})O{sub 3}-(Pb{sub 0.97}La{sub 0.02})(Zr{sub 0.9}Sn{sub 0.05} Ti{sub 0.05})O{sub 3} (PBLYZST-PLZST) were fabricated by the conventional solid-state sintering process (CS), the glass-aided sintering (GAS), and the spark plasma sintering (SPS), respectively. The influence of the temperature induced phase transition on the phase structure, hysteresis loops, and energy storage properties of the composite ceramics were investigated in detail. The measured results of X-ray diffraction demonstrate that the composite ceramics exhibit the perovskite phases and small amounts of non-functional pyrochlore phases. Compared with the CS process, the GAS and SPS processes are proven more helpful to suppress the diffusion behaviors between the PBLYZST and PLZST phases according to the field emission scanning electron microscopy, thereby being able to improve the contribution of PBLYZST phase to the temperature stability of the orthogonal AFE phase. When the ambient temperature rises from 25 °C to 125 °C, CS and GAS samples have undergone a phase transition from orthorhombic AFE phase to tetragonal AFE phase, which results in a sharp decline in the energy storage density. However, the phase transition temperature of SPS samples is higher than 125 °C, and the energy storage density only slightly decreases due to the disorder of material microstructure caused by the high temperature. As a result, the SPS composite ceramics obtain a recoverable high energy storage density of 6.46 J/cm{sup 3} and the excellent temperature stability of the energy storage density of 1.16 × 10{sup −2} J/°C·cm{sup 3}, which is 1.29 × 10{sup −2} J/°C·cm{sup 3} lower than that of CS samples and about 0.43 times as that of GAS samples.

  3. Synthesis, crystal structure, and high-temperature phase transition of the novel plumbide Na2MgPb.

    Science.gov (United States)

    Yamada, Takahiro; Ikeda, Takuji; Stoffel, Ralf P; Deringer, Volker L; Dronskowski, Richard; Yamane, Hisanori

    2014-05-19

    A hitherto unknown sodium magnesium plumbide, Na2MgPb, was synthesized by heating the constituent elements. Na2MgPb crystallizes in a hexagonal unit cell with the Li2CuAs-type structure (P63/mmc, Z = 2, a = 5.110(2) Å, c = 10.171(4) Å at 293 K). The compound furthermore displays polymorphism: high-temperature powder XRD measurements revealed that hexagonal Na2MgPb (dubbed the "α" phase) transforms to another hexagonal phase (β) which is existent at 493-553 K, and the β phase changes to a cubic structure (γ) at 533-633 K further. The molar volume of γ-Na2MgPb is approximately 9% and 13% smaller than the molar volumes of the α phase and the β phase, respectively (at 543 K). The electrical resistivity of Na2MgPb is 0.39 mΩ at 300 K; it rises with increasing temperature from 300 to 491 K, and then drops at 491 and 523 K. These abrupt changes in resistivity may be attributed to the α → β and β → γ phase transitions, respectively. To gain further insight into the structure of cubic γ-Na2MgPb, putative models with regular Heusler-type (Cu2MnAl-type) and inverse Heusler-type (Li2AgSb-type) arrangements were probed using first-principles computations based on density functional theory (DFT). These computations indicate that, for the cubic γ phase, an inverse Heusler-type structure is distinctly more stable than the alternative regular Heusler type (at 0 K); beyond that, ab initio thermochemistry was successfully used to verify the stability ordering (α-Na2MgPb being favorable at low temperature, γ-Na2MgPb at high temperature), albeit the theoretically predicted transition temperature of 900 K which is higher than observed in experiment.

  4. Theory of relaxation phenomena in a spin-3/2 Ising system near the second-order phase transition temperature

    Energy Technology Data Exchange (ETDEWEB)

    Keskin, Mustafa [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)]. E-mail: keskin@erciyes.edu.tr; Canko, Osman [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2005-12-19

    The relaxation behavior of the spin-3/2 Ising model Hamiltonian with bilinear and biquadratic interactions near the second-order phase transition temperature or critical temperature is studied by means of the Onsager's theory of irreversible thermodynamics or the Onsager reciprocity theorem (ORT). First, we give the equilibrium case briefly within the molecular-field approximation in order to study the relaxation behavior by using the ORT. Then, the ORT is applied to the model and the kinetic equations are obtained. By solving these equations, three relaxation times are calculated and examined for temperatures near the second-order phase transition temperature. It is found that one of the relaxation times goes to infinity near the critical temperature on either side, the second relaxation time makes a cusp at the critical temperature and third one behaves very differently in which it terminates at the critical temperature while approaching it, then showing a 'flatness' property and then decreases. We also study the influences of the Onsager rate coefficients on the relaxation times. The behavior of these relaxation times is discussed and compared with the spin-1/2 and spin-1 Ising systems.

  5. Theory of relaxation phenomena in a spin-3/2 Ising system near the second-order phase transition temperature

    Science.gov (United States)

    Keskin, Mustafa; Canko, Osman

    2005-12-01

    The relaxation behavior of the spin-3/2 Ising model Hamiltonian with bilinear and biquadratic interactions near the second-order phase transition temperature or critical temperature is studied by means of the Onsager's theory of irreversible thermodynamics or the Onsager reciprocity theorem (ORT). First, we give the equilibrium case briefly within the molecular-field approximation in order to study the relaxation behavior by using the ORT. Then, the ORT is applied to the model and the kinetic equations are obtained. By solving these equations, three relaxation times are calculated and examined for temperatures near the second-order phase transition temperature. It is found that one of the relaxation times goes to infinity near the critical temperature on either side, the second relaxation time makes a cusp at the critical temperature and third one behaves very differently in which it terminates at the critical temperature while approaching it, then showing a “flatness” property and then decreases. We also study the influences of the Onsager rate coefficients on the relaxation times. The behavior of these relaxation times is discussed and compared with the spin-1/2 and spin-1 Ising systems.

  6. Orientation relations during the α-ω phase transition of zirconium: in situ texture observations at high pressure and temperature.

    Science.gov (United States)

    Wenk, H-R; Kaercher, P; Kanitpanyacharoen, W; Zepeda-Alarcon, E; Wang, Y

    2013-11-08

    Transition metals Ti, Zr, and Hf have a hexagonal close-packed structure (α) at ambient conditions, but undergo phase transformations with increasing temperature and pressure. Of particular significance is the high-pressure hexagonal ω phase which is brittle compared to the α phase. There has been a long debate about transformation mechanisms and orientation relations between the two crystal structures. Here we present the first high pressure experiments with in situ synchrotron x-ray diffraction texture studies on polycrystalline aggregates. We follow crystal orientation changes in Zr, confirming the original suggestion by Silcock for an α→ω martensitic transition for Ti, with (0001)(α)||(1120)(ω), and a remarkable orientation memory when ω reverts back to α.

  7. On the critical temperature discontinuity at the theoretical bcc-fcc phase transition in compressed selenium and tellurium superconductors

    Science.gov (United States)

    Szczęśniak, D.; Wrona, I. A.; Drzazga, E. A.; Kaczmarek, A. Z.; Szewczyk, K. A.

    2017-11-01

    Recent hydrides-driven advent in the high-pressure phonon-mediated superconductivity motivates research on chemical elements which compound with hydrogen. It is desired that such elements should allow chemical pre-compression of hydrogen to assure the induction of the superconducting phase with the high transition temperature (T C). Herein, we present detailed theoretical insight into the properties of the superconducting state induced under pressure (p) in two of such component elements, namely selenium (Se) and tellurium (Te) at p=250 GPa and p=70 GPa, respectively. The assumed external pressure conditions allow us to conduct our analysis just above previously theoretically predicted bcc-fcc structural phase transition of Se and Te, and identify the possible associated discontinuity effect of the critical temperature. In particular, our numerical analysis is conducted within Migdal-Eliashberg formalism, due to the confirmed electron-phonon pairing mechanism and relatively high electron-phonon coupling constant in the materials of interest. We predict that T C values in Se and Te equal 8.13 K and 5.96 K, respectively, and mark the highest critical temperature values for these elements within the postulated fcc phase. Additionally, we supplement these results by the estimated maximum values of the superconducting energy band gap and the effective mass of electrons. We predict that all these parameters can be used as a guidelines for experimental observation of the critical temperature discontinuity and the corresponding bcc-fcc phase transition in Se and Te superconductors. Moreover, we show that the thermodynamics of superconducting phase in both elements may exhibit deviations from the conventional estimates of the Bardeen-Cooper-Schrieffer theory, and suggest existence of the strong-coupling and retardation effects. Finally, we note that our results can be also instructive for future screening of chemical elements for applications in superconducting hydrides.

  8. Finite-temperature phase transition to a Kitaev spin liquid phase on a hyperoctagon lattice: A large-scale quantum Monte Carlo study

    Science.gov (United States)

    Mishchenko, Petr A.; Kato, Yasuyuki; Motome, Yukitoshi

    2017-09-01

    The quantum spin liquid is an enigmatic quantum state in insulating magnets, in which conventional long-range order is suppressed by strong quantum fluctuations. Recently, an unconventional phase transition was reported between the low-temperature quantum spin liquid and the high-temperature paramagnet in the Kitaev model on a three-dimensional hyperhoneycomb lattice. Here, we show that a similar "liquid-gas" transition takes place in another three-dimensional lattice, the hyperoctagon lattice. We investigate the critical phenomena by adopting the Green-function based Monte Carlo technique with the kernel polynomial method, which enables systematic analysis of up to 2048 sites. The critical temperature is lower than that in the hyperhoneycomb case, reflecting the smaller flux gap. We also discuss the transition on the basis of an effective model in the anisotropic limit.

  9. Hydrogen-doping induced reduction in the phase transition temperature of VO2: a first-principles study.

    Science.gov (United States)

    Cui, Yuanyuan; Shi, Siqi; Chen, Lanli; Luo, Hongjie; Gao, Yanfeng

    2015-08-28

    VO2 is a promising thermochromic material that can intelligently control the transmittance of sunlight in the near-infrared region in response to temperature change, although the high phase transition temperature (Tc) of 340 K restricts its wide application. Our first-principles calculations show that hydrogen is an efficient dopant which can stabilize the metallic VO2 phase at ambient temperature through reducing Tc by 38 K/at% H. The reduction in Tc is coupled with the changes in atomic and electronic structures, i.e., the V-V chains feature the dimerization characteristics in H-doped VO2(R) and the V-O bonds become less ionic due to the formation of a typical H-O covalent bond. In addition, hydrogen-doped VO2 is more sensitive to external strain as compared with pure VO2, implying that Tc can be further regulated through a combination of H-doping and strain.

  10. TRANSITION AND DECOMPOSITION TEMPERATURES OF CEMENT PHASES - A COLLECTION OF THERMAL ANALYSIS DATA

    Directory of Open Access Journals (Sweden)

    Nick C. Collier

    2016-10-01

    Full Text Available Thermal analysis techniques provide the cement chemist with valuable tools to qualify and quantify the products formed during the hydration of cementitious materials. These techniques are commonly used alongside complimentary techniques such as X-ray diffraction and electron microscopy/energy dispersive spectroscopy to confirm the composition of phases present and identify amorphous material unidentified by other techniques. The most common thermal analysis techniques used by cement chemists are thermogravimetry, differential thermal analysis and differential scanning calorimetry. In order to provide a useful reference tool to the cement chemist, this paper provides a brief summary of the temperatures at which phase changes occur in the most common cement hydrates in the range 0-800°C in order to aid phase identification.

  11. Ligand partitioning into lipid bilayer membranes under high pressure: Implication of variation in phase-transition temperatures.

    Science.gov (United States)

    Matsuki, Hitoshi; Kato, Kentaro; Okamoto, Hirotsugu; Yoshida, Shuntaro; Goto, Masaki; Tamai, Nobutake; Kaneshina, Shoji

    2017-12-01

    The variation in phase-transition temperatures of dipalmitoylphosphatidylcholine (DPPC) bilayer membrane by adding two membrane-active ligands, a long-chain fatty acid (palmitic acid (PA)) and an inhalation anesthetic (halothane (HAL)), was investigated by light-transmittance measurements and fluorometry. By assuming the thermodynamic colligative property for the bilayer membrane at low ligand concentrations, the partitioning behavior of these ligands into the DPPC bilayer membrane was considered. It was proved from the differential partition coefficients between two phases that PA has strong affinity with the gel (lamellar gel) phase in a micro-molal concentration range and makes the bilayer membrane more ordered, while HAL has strong affinity with the liquid crystalline phase in a milli-molal concentration range and does the bilayer membrane more disordered. The transfer volumes of both ligands from the aqueous solution to each phase of the DPPC bilayer membrane showed that the preferential partitioning of the PA molecule into the gel (lamellar gel) produces about 20% decrease in transfer volume as compared with the liquid crystalline phase, whereas that of the HAL molecule into the liquid crystalline phase does about twice increase in transfer volume as compared with the gel (ripple gel) phase. Furthermore, changes in thermotropic and barotropic phase behavior of the DPPC bilayer membrane by adding the ligand was discussed from the viewpoint of the ligand partitioning. Reflecting the contrastive partitioning of PA and HAL into the pressure-induced interdigitated gel phase among the gel phases, it was revealed that PA suppresses the formation of the interdigitated gel phase under high pressure while HAL promotes it. These results clearly indicate that each phase of the DPPC bilayer membrane has a potential to recognize various ligand molecules. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Composition dependence of the phase transition temperature in Sr{sub x}Ba{sub 1-x}Nb{sub 2}O{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    David, C.; Tunyagi, A.; Woehlecke, M.; Betzler, K.; Ulex, M.; Imlau, M.; Pankrath, R. [Fachbereich Physik, Universitaet Osnabrueck, Barbarastr. 7, 49069 Osnabrueck (Germany); Granzow, T.; Woike, Th. [Institut fuer Mineralogie, Zuelpicher Str. 49b, 50674 Koeln (Germany)

    2004-06-01

    The temperature dependence of the spontaneous polarization in strontium-barium-niobate single crystals with varying Sr/Ba ratio is presented. The temperature of the relaxor phase-transition is determined from the inflexion point of the curve of the ferroelectric polarization versus temperature. The influence of the Sr/Ba ratio in the crystal on the transition temperature is discussed within an effective field approach. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. Effect of borojo (Borojoa patinoi Cuatrecasas) three-phase composition and gum arabic on the glass transition temperature.

    Science.gov (United States)

    Rodríguez-Bernal, Jenny M; Tello, Edisson; Flores-Andrade, Enrique; Perea-Flores, Maria de Jesús; Vallejo-Cardona, Alba A; Gutiérrez-López, Gustavo F; Quintanilla-Carvajal, Maria X

    2016-02-01

    The search for natural, novel, high-quality, stable food ingredients is an ongoing practice in the food industry. Pulp of borojo (Borojoa patinoi Cuatrecasas), which is a fruit of the Colombian Pacific region, can be separated into three phases: liquid (LP), medium (MP) and solid (SP) phases. The objective of this work was to evaluate the effect of the three-phase composition and gum arabic on their glass transitions temperatures (T(g)). The best mixture, LP-MP, MP-SP and LP-SP and gum arabic (GA) was identified by response surface methodology. When adding GA to SP borojo phase in a 1:1 proportion, the resulting T(g) of the mixture was 132.27 °C whereas Tg for GA and SP-phase were 154.89 °C and 79.86 °C respectively, which supported this combination as attractive from a processing perspective and supports an industrial advantage of using borojo as food ingredient. Phases were characterized by high-performance liquid chromatography, Fourier transform infrared spectroscopy, confocal laser scanning microscopy and mass spectrometry. Low molecular weight compounds such as fructose for MP lowered T(g) whereas the presence of lignin increased T(g) of the mixtures as with the SP. The addition of GA significantly increased T(g) of borojo phases so leading to propose them as novel food processing materials. © 2015 Society of Chemical Industry.

  14. Temperature phase transitions associated with local minima of energy in continous unbounded spins

    CERN Document Server

    Dobrovolny, B

    2004-01-01

    {\\footnotesize In this work we develop an alternative version of the theory of contour models adapted to continuous spins, $\\omega_{x}\\in {\\large{\\bf {R}}}$, located in sites, $x$ of a $d\\geq 2$ dimensional lattice ${\\large{\\bf Z^{d}}}$. \\\\ The spins interacting via nearest neighbors ferromagnetic interactions are embedded in a single spin potential $V$ similar to that, already, introduced by Dobrushin and Shlosman.\\\\ The potential $V$, has an ordered sequence $\\left( \\omega_{1}m_{q^{^{\\prime }}}$, $q< q^{^{\\prime }}$. \\item The distance between two successive minima is sufficiently great and the they are separated by a sufficiently heigh energy barrier. \\end{itemize} For all finite reciprocal temperature $\\beta$, satisfying $1\\leq \\beta <\\infty$, and for the mass $m_{n}$ ( corresponding to the $n^{th}$ minimum) large enough, we prove the Peierls condition, and we derive the phase diagram by proving that there exist sequences ($\\beta_{1},... ,\\beta_{N(n)}$) , $N(n)phase transitio...

  15. Dynamic approach to finite-temperature magnetic phase transitions in the extended J1-J2 model with vacancy order.

    Science.gov (United States)

    Zhou, N J; Zheng, B; Dai, J H

    2013-02-01

    The recently discovered iron-based superconductors A(y)Fe(2-x)Se(2) (A=K, Rb, Cs, Tl) show a long-range antiferromagnetic order with an unexpectedly high transition temperature T(N)~550 K and a unique √5×√5 vacancy order. Taking the extended J(1)-J(2) model as a minimal model, we investigate the finite-temperature magnetic phase transitions in a square lattice with a √5×√5 vacancy superstructure by using large-scale Monte Carlo simulations. By the parallel tempering technique, the block spin checkerboard and stripe antiferromagnetic states are detected to be the ground states for three representative sets of model parameters. The short-time dynamic approach is applied to accurately determine the critical temperature as well as the static and dynamic exponents. Our results indicate that the dramatic enhancement of the critical temperature as observed in experiments should be mainly due to a combination of the vacancy order and the block lattice contraction.

  16. Symmetry structure and phase transitions

    Indian Academy of Sciences (India)

    ... symmetry structure at finite density and temperature in the presence of external magnetic field and gravity, a situation relevant in the early Universe and in the core of compact stars. We then investigate the dynamical evolution of phase transition in the expanding early Universe and possible formation of quark nuggets and ...

  17. Drastic lowering of the order-disorder phase transition temperatures in Zr1-xMxW2O8-y(M=Sc,Y,In) solid solutions

    Science.gov (United States)

    Yamamura, Yasuhisa; Nakajima, Noriyuki; Tsuji, Toshihide; Kojima, Ayumi; Kuroiwa, Yoshihiro; Sawada, Akikatsu; Aoyagi, Shinobu; Kasatani, Hirofumi

    2004-09-01

    ZrW2O8 undergoes an order-disorder phase transition associated with the orientational disordering of the WO4 tetrahedra at 440K . We have showed previously that the phase transition temperatures of Zr1-xMxW2O8-y(M=Sc,Y,In) solid solutions are decreased by a maximum of 80K with only 4% trivalent Sc content. In order to understand the drastic composition dependence on the transition temperature, precise x-ray diffraction experiments on the solid solutions were performed by using a synchrotron radiation. The results provided the evidence of the strong correlation between the phase transition temperature and the number of WO4 units with the ordered orientation. A model was proposed to interpret the drastic composition dependence on the transition temperature, by considering the existence of a local region including the WO4 pairs with the orientational disorder in Zr1-xMxW2O8-y(M=Sc,Y,In) . The local region has the crystal structure of the high-temperature phase in a nonequilibrium state, and spreads out around the substituted trivalent cations. The size of the local region was estimated to be a few unit cells. The local regions play just like nonmagnetic impurities in a site-diluted magnetic system, leading to drastic lowering of the phase transition temperatures in Zr1-xMxW2O8-y solid solutions.

  18. Room-temperature electrically driven phase transition of two-dimensional 1T-TaS2 layers.

    Science.gov (United States)

    Zheng, Shoujun; Liu, Fucai; Zhu, Chao; Liu, Zheng; Fan, Hong Jin

    2017-02-16

    Due to the strong electron-electron and electron-phonon interactions, the transition metal dichalcogenide 1T-TaS2 exhibits temperature dependent as well as electric field driven charge density wave (CDW) phase transitions (PTs). In this work, we investigate the thickness dependence of the electric field driven PT in 1T-TaS2 two-dimensional (2D) flakes. Electrically driven PT between high- and low-resistance states occurs at temperatures in the range of 60-300 K. For a thin 1T-TaS2 (≤8.8 nm) sample, only one PT is triggered, whereas thick films experience double PTs (13-17 nm) and multiple PTs (≥17.5 nm) until reaching the final low-resistance state. The multiple PTs may imply the existence of hidden nearly-commensurate charge density wave (NCCDW) states. In addition, a threshold electric field is observed, in which the low-resistance state is unable to resume the high-resistance state. Finally, we fabricate a 1T-TaS2/graphene hybrid field effect transistor to achieve a gate-tunable PT at room temperature. Such a hybrid device might provide a new avenue for the construction of CDW-based memories based on 2D materials.

  19. Phase transition in nanomagnetite

    Science.gov (United States)

    Dézsi, I.; Fetzer, Cs.; Gombkötő, Á.; Szűcs, I.; Gubicza, J.; Ungár, T.

    2008-05-01

    Recently, the application of nanosized magnetite particles became an area of growing interest for their potential practical applications. Nanosized magnetite samples of 36 and 9nm sizes were synthesized. Special care was taken on the right stoichiometry of the magnetite particles. Mössbauer spectroscopy measurements were made in 4.2-300K temperature range. The temperature dependence of the intensities of the spectral components indicated size dependent transition taking place in a broad temperature range. For nanosized samples, the hyperfine interaction values and their relative intensities changed above the Verwey transition temperature value of bulk megnetite. The continuous transition indicated the formation of dendritelike granular assemblies formed during the preparation of the samples.

  20. High-temperature order-disorder phase transition in nacaphite, Na2CaPO4F

    Science.gov (United States)

    Avdontceva, Margarita S.; Krzhizhanovskaya, Maria G.; Krivovichev, Sergey V.; Yakovenchuk, Viktor N.

    2015-09-01

    The thermal behavior of nacaphite, Na2CaPO4F, was studied by the powder high-temperature X-ray diffraction method. A monoclinic-to-orthorhombic phase transition has been observed at 330 °C associated with the appearance of the Ca/Na disorder at one of the two crystallographically inequivalent Na sites. At room temperature, nacaphite is monoclinic, P21 /c, a = 13.3185(14), b = 7.0964(8), c = 10.6490(11) Å, β = 113.526(1)°, V = 922.81(17) Å3. The structure is based upon one-dimensional antiperovskite units consisting of face-sharing [FNa4Ca2]7+ anion-centered octahedra running parallel to the c axis. The structure is fully ordered and contains two Ca and four Na sites. The crystal structure of the high-temperature modification [refined by Rietveld method ( R B 0.025) at 400 °C from the powder X-ray diffraction data] is orthorhombic, Pnma, a = 5.4123(1), b = 7.1196(1), c = 12.3171(1) Å, V = 474.62(1) Å3. The structure has one fully occupied Na1 site and one mixed occupied Na2 site, the latter being equally occupied by Na and Ca. The Na1 and Na2 sites are coordinated by two F- and four O2- anions each. The phase transition has an order-disorder character and is associated with the decrease of structural complexity measured as an information content per unit cell (300.235 bits for the low- and 98.117 bits for the high-temperature modifications). Thermal expansion of both modifications has an anisotropic character with the degree of anisotropy increasing from the low- to the high-temperature phase. The direction of the strongest thermal expansion is parallel to the direction of chains of face-sharing anion-centered octahedra that can be explained by the temperature-induced expansion of the F-Na/Ca bonds.

  1. Electronic phase transitions

    CERN Document Server

    Kopaev, YuV

    1992-01-01

    Electronic Phase Transitions deals with topics, which are presently at the forefront of scientific research in modern solid-state theory. Anderson localization, which has fundamental implications in many areas of solid-state physics as well as spin glasses, with its influence on quite different research activities such as neural networks, are two examples that are reviewed in this book. The ab initio statistical mechanics of structural phase transitions is another prime example, where the interplay and connection of two unrelated disciplines of solid-state theory - first principle ele

  2. Soy Sauce Residue Oil Extracted by a Novel Continuous Phase Transition Extraction under Low Temperature and Its Refining Process.

    Science.gov (United States)

    Zhao, Lichao; Zhang, Yong; He, Liping; Dai, Weijie; Lai, Yingyi; Yao, Xueyi; Cao, Yong

    2014-04-09

    On the basis of previous single-factor experiments, extraction parameters of soy sauce residue (SSR) oil extracted using a self-developed continuous phase transition extraction method at low temperature was optimized using the response surface methodology. The established optimal conditions for maximum oil yield were n-butane solvent, 0.5 MPa extraction pressure, 45 °C temperature, 62 min extraction time, and 45 mesh raw material granularity. Under these conditions, the actual yield was 28.43% ± 0.17%, which is relatively close to the predicted yield. Meanwhile, isoflavone was extracted from defatted SSR using the same method, but the parameters and solvent used were altered. The new solvent was 95% (v/v) ethanol, and extraction was performed under 1.0 MPa at 60 °C for 90 min. The extracted isoflavones, with 0.18% ± 0.012% yield, mainly comprised daidzein and genistein, two kinds of aglycones. The novel continuous phase transition extraction under low temperature could provide favorable conditions for the extraction of nonpolar or strongly polar substances. The oil physicochemical properties and fatty acids compositions were analyzed. Results showed that the main drawback of the crude oil was the excess of acid value (AV, 63.9 ± 0.1 mg KOH/g) and peroxide value (POV, 9.05 ± 0.3 mmol/kg), compared with that of normal soybean oil. However, through molecular distillation, AV and POV dropped to 1.78 ± 0.12 mg KOH/g and 5.9 ± 0.08 mmol/kg, respectively. This refined oil may be used as feedstuff oil.

  3. Phase transitions and melting on the Hugoniot of Mg2SiO4 forsterite: new diffraction and temperature results

    Science.gov (United States)

    Asimow, P. D.; Akin, M. C.; Homel, M.; Crum, R. S.; Pagan, D.; Lind, J.; Bernier, J.; Mosenfelder, J. L.; Dillman, A. M.; Lavina, B.; Lee, S.; Fat'yanov, O. V.; Newman, M. G.

    2017-06-01

    The phase transitions of forsterite under shock were studied by x-ray diffraction and pyrometry. Samples of 2 mm thick, near-full density (>98% TMD) polycrystalline forsterite were characterized by EBSD and computed tomography and shock compressed to 50 and 75 GPa by two-stage gas gun at the Dynamic Compression Sector, Advanced Photon Source, with diffraction imaged during compression and release. Changes in diffraction confirm a phase transition by 75 GPa. In parallel, single-crystal forsterite shock temperatures were taken from 120 to 210 GPa with improved absolute calibration procedures on the Caltech 6-channel pyrometer and two-stage gun and used to examine the interpretation of superheating and P-T slope of the liquid Hugoniot. This work performed under the auspices of the U.S. Department of Energy (DOE) by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344, supported in part by LLNL's LDRD program under Grants 15-ERD-012 and 16-ERD-010. The Dynamic Compression Sector (35) is supported by DOE / National Nuclear Security Administration under Award Number DE-NA0002442. This research used resources of the Advanced Photon Source, a U.S. DOE Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. Caltech lab supported by NSF EAR-1426526.

  4. High-temperature phase transformations in YBa/sub 2/Cu/sub 3/O(7+delta) and their effect on the superconducting transition

    Energy Technology Data Exchange (ETDEWEB)

    Sukharevskii, B.IA.; Shatalova, G.E.; Khokhlova, S.I.; Mikheenko, P.N.; Ksenofontov, V.G.

    1987-09-01

    Low-temperature (700 K or less), intermediate equilibrium (700-900 K), and hardened metastable phases, as well as a high-temperature (900 K and above) tetragonal phase, have been identified in polycrystalline YBa/sub 2/Cu/sub 3/O(7+delta). The transition between the first two phases is associated with the loss (during heating) or addition (during cooling) of one oxygen ion per formula unit. Superconductivity is realized in the low-temperature phase, in which the copper ions of two middle copper-oxygen planes are octahedrally coordinated by oxygen ions.

  5. Photoinduced phase transitions

    CERN Document Server

    Nasu, K

    2004-01-01

    A new class of insulating solids was recently discovered. Whenirradiated by a few visible photons, these solids give rise to amacroscopic excited domain that has new structural and electronicorders quite different from the starting ground state. This occurrenceis called "photoinduced phase transition", and this multi-authoredbook reviews recent theoretical and experimental studies of this newphenomenon.

  6. Phase transitions in the hard-core Bose-Fermi-Hubbard model at non-zero temperatures in the heavy-fermion limit

    Energy Technology Data Exchange (ETDEWEB)

    Stasyuk, I.V.; Krasnov, V.O., E-mail: krasnoff@icmp.lviv.ua

    2017-04-15

    Phase transitions at non-zero temperatures in ultracold Bose- and Fermi-particles mixture in optical lattices using the Bose-Fermi-Hubbard model in the mean field and hard-core boson approximations are investigated. The case of infinitely small fermion transfer and the repulsive on-site boson-fermion interaction is considered. The possibility of change of order (from the 2nd to the 1st one) of the phase transition to the superfluid phase in the regime of fixed values of the chemical potentials of Bose- and Fermi-particles is established. The relevant phase diagrams determining the conditions at which such a change takes place, are built.

  7. Finite-Temperature Phase Transition in the Montorsi-Rasetti Model

    NARCIS (Netherlands)

    Michielsen, K.; Raedt, H. De; Schneider, T.; de Vries, Pedro

    1994-01-01

    Exact diagonalization and quantum Monte Carlo methods are used to compute the specific heat and the charge and spin correlation functions for a two-dimensional system of correlated electrons, described by the Montorsi-Rasetti model. Our results strongly suggest the occurrence of an unusual phase

  8. Ferroelectric InMnO{sub 3}: Growth of single crystals, structure and high-temperature phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Bekheet, Maged F., E-mail: maged.bekheet@ceramics.tu-berlin.de [Fachbereich Material‐ und Geowissenschaften, Technische Universität Darmstadt, Alarich-Weiss-Straße 2, 64287 Darmstadt (Germany); Fachgebiet Keramische Werkstoffe / Chair of Advanced Ceramic Materials, Institut für Werkstoffwissenschaften und -technologien, Technische Universität Berlin, Hardenbergstraße 40, 10623 Berlin (Germany); Svoboda, Ingrid; Liu, Na [Fachbereich Material‐ und Geowissenschaften, Technische Universität Darmstadt, Alarich-Weiss-Straße 2, 64287 Darmstadt (Germany); Bayarjargal, Lkhamsuren [Institut für Geowissenschaften, Goethe-Universität, Altenhöferallee 1, d-60438 Frankfurt a.M. (Germany); Irran, Elisabeth [Institut für Chemie, Technische Universität Berlin, Straße des 17, Juni 135, 10623 Berlin (Germany); Dietz, Christian; Stark, Robert W.; Riedel, Ralf [Fachbereich Material‐ und Geowissenschaften, Technische Universität Darmstadt, Alarich-Weiss-Straße 2, 64287 Darmstadt (Germany); Gurlo, Aleksander [Fachgebiet Keramische Werkstoffe / Chair of Advanced Ceramic Materials, Institut für Werkstoffwissenschaften und -technologien, Technische Universität Berlin, Hardenbergstraße 40, 10623 Berlin (Germany)

    2016-09-15

    To understand the origin of the ferroelectricity in InMnO{sub 3}, single crystals with average size of 1 mm were grown in PbF{sub 2} flux at 950 °C. The results of single crystal X-ray diffraction, second harmonic generation and piezoresponse force microscopy studies of high-quality InMnO{sub 3} single crystals reveal that the room-temperature state in this material is ferroelectric with P6{sub 3}cm symmetry. The polar InMnO{sub 3} specimen undergoes a reversible phase transition from non-centrosymmetric P6{sub 3}cm structure to a centrosymmetric P6{sub 3}/mmc structure at 700 °C as confirmed by the in situ high-temperature Raman spectroscopic and synchrotron X-ray diffraction experiments. - Graphical abstract: Piezoresponse fore microscopy (PFM) studies of high quality InMnO{sub 3} single crystal revealed that the room-temperature state of this material is ferroelectric with a clear cloverleaf pattern corresponding to six antiphase ferroelectric domains with alternating polarization ±P{sub z}. Display Omitted - Highlights: • InMnO{sub 3} single crystals with average size of 1 mm were grown in PbF{sub 2} flux at 950 °C. • The room-temperature state of InMnO{sub 3} is ferroelectric with polar P6{sub 3}cm structure. • PolarInMnO{sub 3} reversibly transforms to a centrosymmetric P6{sub 3}/mmc structure above 700 °C.

  9. Effects of Phase Fraction on Temperature Dependency of Fracture Toughness in Transition Temperature Region in SA508 Gr. 4N Ni-Mo-Cr Low Alloy Steels

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ki Hyoung; Wee, Dang Moon [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Kim, Min Chul; Lee, Bong Sang [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2010-10-15

    The Reactor Pressure Vessel (RPV) is the main component in determining the lifetime of nuclear power plants because it is subject to the aging phenomenon of irradiation embrittlement and there is no practical method for replacing that component. For materials used for the RPV, sufficient strength and toughness are required to prevent failure against the severe operating conditions and the aging degradation of materials. SA508 Gr.4N Ni-Mo-Cr low alloy steel, in which Ni and Cr contents are higher than in conventional RPV steels, may be a promising RPV material with the improved strength and toughness from its tempered martensitic microstructure. Wallin observed that the temperature dependency of fracture toughness is not sensitive to the chemical composition, heat treatment, and irradiation for ferritic steels. This result led to the concept of a universal shape in the median toughness-temperature curve for all 'ferritic steels'. However, there are some doubts about the universal shape in the ASTM master curve for the tempered martensitic steels, such as Eurofer97. It was also reported that the fracture toughness increased discontinuously when the phase fraction of the tempered martensite was over a critical fraction in the heat affected zones of SA508 Gr.3. Therefore, it may be necessary to evaluate the changes of transition behavior with microstructures of steel. In this study, the effects phase fraction of tempered martensite controlled by a cooling rate on the transition behavior of SA508 Gr.4N low alloy steels was evaluated. Additionally, the relationship between the variations of yield strength with the temperature and fracture stress in a local approach was discussed

  10. Phase transition in nonlinear viscous cosmology

    Science.gov (United States)

    Novello, M.; Duque, S. L. S.; Triay, R.; Fliche, H. H.

    1993-04-01

    A simple example of a phase transition process describing the isotropization of a universe of Bianchi type is outlined. Such a mechanism is induced by a self-gravitating fluid, and it operates as described by Landau's phase transition. The expansion factor (the Hubble constant) plays the part of the control parameter as the temperature does for ordinary matter.

  11. The Structural Phase Transition in Solid DCN

    DEFF Research Database (Denmark)

    Dietrich, O. W.; Mackenzie, Gordon A.; Pawley, G. S.

    1975-01-01

    Neutron scattering measurements on deuterated hydrogen cyanide have shown that the structural phase change from a tetragonal to an orthorhombic form at 160K is a first-order transition. A transverse acoustic phonon mode, which has the symmetry of the phase change, was observed at very low energies...... and showed 'softening' as the transition temperature was approached from above....

  12. Polarization induced water molecule dissociation below the first-order electronic-phase transition temperature

    CERN Document Server

    Arulsamy, Andrew Das; Elersic, Kristina; Modic, Martina; Subramani, Uma Shankar

    2011-01-01

    Hydrogen produced from the photocatalytic splitting of water is one of the reliable alternatives to replace the polluting fossil and the radioactive nuclear fuels. Here, we provide unequivocal evidence for the existence of blue- and red-shifting O$-$H covalent bonds within a single water molecule adsorbed on MgO surface as a result of asymmetric displacement polarizabilities. The adsorbed H-O-H on MgO gives rise to one weaker H-O bond, while the other O-H covalent bond from the same adsorbed water molecule compensates this effect with a stronger bond. The weaker bond (nearest to the surface), the interlayer tunneling electrons and the silver substrate are shown to be the causes for the smallest dissociative activation energy on MgO monolayer. The origin that is responsible to initiate the splitting mechanism is proven to be due to the changes in the polarizability of an adsorbed water molecule, which are further supported by the temperature-dependent static dielectric constant measurements for water below the...

  13. A High-Temperature Order-Disorder Phase Transition Coupled With Conformational Change in the Hybrid Material [C6 H13 NH]2 ⋅ZnBr4.

    Science.gov (United States)

    Khan, Tariq; Asghar, Muhammad Adnan; Sun, Zhihua; Zeb, Aurang; Li, Lina; Sijie, Liu; Zhao, Sangen; Ji, Chengmin; Luo, Junhua

    2016-10-20

    A new high-temperature, hybrid, phase-transition material, 1-methylpiperidinium tetrabromozincate (1), that shows a reversible transition at 345 K was synthesized. Differential scanning calorimetry and specific heat capacity measurements confirmed this reversible transformation with a large heat hysteresis of 25 K, which describes a typical first-order phase transition in 1. The dielectric constant exhibited a steplike anomaly and showed high and low dielectric states in the high- and room-temperature phases, respectively, and therefore, this hybrid might be considered as a potential switchable dielectric material. The variable-temperature powder X-ray diffraction patterns displayed remarkable shifts between the experimental patterns at the two different phases. Single-crystal X-ray diffraction analyses at various temperatures revealed that the origin of this transformation could be attributed to disordering of the bromine atoms in the anion and the nitrogen atom of the cation. The cation also assumed a conformational change, which was likely induced by the disordered nitrogen atom. The conformational onset of the transformation of the cation from a planar conformer into a relaxed chair also occurred upon decreasing the temperature below transition point; thus, the combined order-disorder and conformational change induced the structural transformation and the change in symmetry. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Phase transition to QGP matter : confined vs deconfined matter

    CERN Multimedia

    Maire, Antonin

    2015-01-01

    Simplified phase diagram of the nuclear phase transition, from the regular hadronic matter to the QGP phase. The sketch is meant to describe the transition foreseen along the temperature axis, at low baryochemical potential, µB.

  15. Selecting polymers for two-phase partitioning bioreactors (TPPBs): Consideration of thermodynamic affinity, crystallinity, and glass transition temperature.

    Science.gov (United States)

    Bacon, Stuart L; Peterson, Eric C; Daugulis, Andrew J; Parent, J Scott

    2015-01-01

    Two-phase partitioning bioreactor technology involves the use of a secondary immiscible phase to lower the concentration of cytotoxic solutes in the fermentation broth to subinhibitory levels. Although polymeric absorbents have attracted recent interest due to their low cost and biocompatibility, material selection requires the consideration of properties beyond those of small molecule absorbents (i.e., immiscible organic solvents). These include a polymer's (1) thermodynamic affinity for the target compound, (2) degree of crystallinity (wc ), and (3) glass transition temperature (Tg ). We have examined the capability of three thermodynamic models to predict the partition coefficient (PC) for n-butyric acid, a fermentation product, in 15 polymers. Whereas PC predictions for amorphous materials had an average absolute deviation (AAD) of ≥16%, predictions for semicrystalline polymers were less accurate (AAD ≥ 30%). Prediction errors were associated with uncertainties in determining the degree of crystallinity within a polymer and the effect of absorbed water on n-butyric acid partitioning. Further complications were found to arise for semicrystalline polymers, wherein strongly interacting solutes increased the polymer's absorptive capacity by actually dissolving the crystalline fraction. Finally, we determined that diffusion limitations may occur for polymers operating near their Tg , and that the Tg can be reduced by plasticization by water and/or solute. This study has demonstrated the impact of basic material properties that affects the performance of polymers as sequestering phases in TPPBs, and reflects the additional complexity of polymers that must be taken into account in material selection. © 2015 American Institute of Chemical Engineers.

  16. Relationship between Covalence and Displacive Phase Transition Temperature in RAO 4 and Li AO 3 ( R = Rare-Earth Element and A = Nb and Ta)

    Science.gov (United States)

    Tsunekawa, S.; Kamiyama, T.; Asano, H.; Fukuda, T.

    1995-04-01

    Crystal structure analyses by TOF neutron powder diffraction are performed for RTaO4 (R = rare-earth element) and the Ta-O interatomic distances are determined. The relationship between the covalency of A -O bonds (A = Nb and Ta), which show the most shortening upon phase transition, and the transition temperature is discussed for RA O4 and LiAO3, and the parameters of Ta-O covalence are determined.

  17. Effect of the polymer chain length of poly(N-isopropylacrylamide) on the temperature-responsive phase transition behavior of its conjugates with [60]fullerene.

    Science.gov (United States)

    Uchida, Katsumi; Tamura, Atsushi; Yajima, Hirofumi

    2010-03-01

    In order to develop biomedical materials with specific functionalities, thermoresponsive conjugates [poly(N-isopropylacrylamide)-C(60) (PIPAAm-C(60)) ]of [60]fullerene (C(60)) and PIPAAm with two different polymer chain lengths (4 and 20 kDa) were synthesized by atom transfer radical polymerization. The effects of the polymer chain length on the temperature-responsive phase transition behavior of the synthetic PIPAAm-C(60) conjugates were probed by means of various physicochemical techniques. The coexistence of unimers and molecular assemblies of PIPAAm-C(60) was observed by gel permeation chromatography and dynamic light scattering studies in two PIPAAm-C(60) aqueous solutions below their lower critical solution temperatures (LCSTs). Additionally, below their LCSTs, differences in PIPAAm chain length gave rise to changes in the composition of the unimers and molecular assemblies. In response to temperature, the absorbance of the PIPAAm-C(60) aqueous solution changed according to a two-step behavior profile. Increasing temperature during the primary stage, where a change in the absorbance of the PIPAAm-C(60) aqueous solution took place, did not change the transition temperature, regardless of the solution concentration of PIPAAm-C(60). This absorbance change was associated with the phase transition of the molecular assemblies of PIPAAm-C(60). However, at the second stage, the transition temperature shifted to a higher value with the decrease in the concentration of PIPAAm-C(60), in the same manner as free PIPAAm chains. The second change was associated with the phase transition of the unimeric PIPAAm-C(60). Differences in PIPAAm chain length gave rise to the change in the phase transition behavior of PIPAAm-C(60) aqueous solution. Therefore, the chain length of PIPAAm was found to be a predominant factor involved in the solution characteristics of PIPAAm-C(60). Consequently, the PIPAAm-C(60) is expected to be an intelligent biomaterial possessing heat

  18. Electroweak phase transition recent results

    CERN Document Server

    Csikor, Ferenc

    2000-01-01

    Recent results of four-dimensional (4d) lattice simulations on the finite temperature electroweak phase transition (EWPT) are discussed. The phase transition is of first order in the SU(2)-Higgs model below the end point Higgs mass 66.5$\\pm$1.4 GeV. For larger masses a rapid cross-over appears. This result completely agrees with the results of the dimensional reduction approach. Including the full Standard Model (SM) perturbatively the end point is at 72.1$\\pm$1.4 GeV. Combined with recent LEP Higgs mass lower bounds, this excludes any EWPT in the SM. A one-loop calculation of the static potential makes possible a precise comparison of the lattice and perturbative results. Recent 4d lattice studies of the Minimal Supersymmetric SM (MSSM) are also mentioned.

  19. Photoluminescent-dielectric duple switch in a perovskite-type high-temperature phase transition compound: [(CH3)3PCH2OCH3][PbBr3].

    Science.gov (United States)

    Geng, Fu-Juan; Wu, De-Hong; Zhou, Lin; Shi, Ping-Ping; Li, Peng-Fei; Gao, Ji-Xing; Zheng, Xuan; Fu, Da-Wei; Ye, Qiong

    2017-07-25

    A bistable optical-electrical duple switch belongs to a class of highly satisfying intelligent materials that can transform optical and electrical responses simultaneously in one device. A perovskite-type high-temperature phase transition compound with one-dimensional chain-like crystal structure, ([(CH3)3PCH2OCH3][PbBr3], 1), displays remarkable bistable photoluminescent-dielectric duple switching behaviors. The noteworthy order-disorder transition of the phosphonium cation and the motions of anions contribute to the phase transition, leading to the space group P21/c at a low temperature phase to C2/c at a high temperature phase. 1 exhibits a prominent step-like dielectric anomaly at 401.0 K and demonstrates novel optical properties with a band gap of 3.54 eV. The photoluminescence intensity suddenly declines from 398 K to 408 K, which may be attributed to the occurrence of phase transition. The electron cloud distributions of the frontier orbital in compound 1 have been calculated using a DFT program.

  20. First Order Temperature Dependent Phase Transition in a Monoclinic Polymorph Crystal of 1,6-Hexanedioic Acid: An Interpretation Based on the Landau Theory Approach

    Directory of Open Access Journals (Sweden)

    Hoong-Kun Fun

    2014-07-01

    Full Text Available Crystals of 1,6-hexanedioic acid (I undergo a temperature-dependent reversible phase transition from monoclinic P21/c at a temperature higher than the critical temperature (Tc 130 K to another monoclinic P21/c at temperature lower than Tc. The phase transition is of first order, involving a discontinuity and a tripling of the b-axis at Tc whereas the other unit cell parameters vary continuously. The transition is described by the phenomenological Landau theory. The crystal structure analyses for data collected at 297(2 K and 120.0(1 K show that there is half of a molecule of (I in the asymmetric unit at 297(2 K whereas there are one and a half molecules of (I in the asymmetric unit at 120.0(1 K. At both temperatures, 297(2 and 120.0(1 K, intermolecular O-H···O hydrogen bonds link the molecules of I into infinite 1D chains along [101] direction. However there are significantly more O-H···O hydrogen bonds presented in the 120.0(1 K polymorph, thereby indicating this phase transition is negotiated via hydrogen bonds. The relationship of the conformational changes and hydrogen bonding for these two polymorphs are explained in detail.

  1. Study of negative thermal expansion and shift in phase transition temperature in Ti4+- and Sn4+-substituted ZrW2O8 materials.

    Science.gov (United States)

    Buysser, Klaartje De; Driessche, Isabel Van; Putte, Bart Vande; Vanhee, Paul; Schaubroeck, Joseph; Hoste, Serge

    2008-01-21

    The negative-thermal-expansion material ZrW(2)O(8) is known to undergo an order-disorder phase transition which affects its expansion behavior. In this study, Ti(4+) and Sn(4+) are examined as possible substituting ions for the Zr(4+) position in ZrW(2)O(8). This substitution leads to a decrease in cell parameters, as the ionic radii of the substituents are smaller than the Zr(4+) ionic radius. A remarkable decrease in transition temperature is noticed. DSC is used to quantify the enthalpy and entropy changes during the phase transition in order to reveal the mechanisms behind this decrease. It is shown that the strength of the M-O bond plays an important role, as it is a partner in the rigid unit mode motion and the order-disorder transition mechanism.

  2. Percolation Phase Transition of Surface Air Temperature Networks under Attacks of El Niño/La Niña.

    Science.gov (United States)

    Lu, Zhenghui; Yuan, Naiming; Fu, Zuntao

    2016-05-26

    In this study, sea surface air temperature over the Pacific is constructed as a network, and the influences of sea surface temperature anomaly in the tropical central eastern Pacific (El Niño/La Niña) are regarded as a kind of natural attack on the network. The results show that El Niño/La Niña leads an abrupt percolation phase transition on the climate networks from stable to unstable or metastable phase state, corresponding to the fact that the climate condition changes from normal to abnormal significantly during El Niño/La Niña. By simulating three different forms of attacks on an idealized network, including Most connected Attack (MA), Localized Attack (LA) and Random Attack (RA), we found that both MA and LA lead to stepwise phase transitions, while RA leads to a second-order phase transition. It is found that most attacks due to El Niño/La Niña are close to the combination of MA and LA, and a percolation critical threshold Pc can be estimated to determine whether the percolation phase transition happens. Therefore, the findings in this study may renew our understandings of the influence of El Niño/La Niña on climate, and further help us in better predicting the subsequent events triggered by El Niño/La Niña.

  3. The Strongly Interacting Electroweak Phase Transition

    OpenAIRE

    Bergerhoff, B.; Wetterich, C

    1994-01-01

    A quantitative discussion of nonperturbative effects for the high temperature electroweak phase transition is presented. We propose a method for the computation of the temperature dependent effective scalar potential that takes into account the running of the effective gauge coupling. Compared to perturbation theory we find a moderate decrease of the critical temperature and an important change in the strength of the first order transition. We conclude that perturbation theory gives a mislead...

  4. Observation of reduced phase transition temperature in N-doped thermochromic film of monoclinic VO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Wan, Meinan; Xiong, Mo [State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070 (China); Li, Neng, E-mail: lineng@whut.edu.cn [State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070 (China); Liu, Baoshun; Wang, Shuo [State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070 (China); Ching, Wai-Yim [Department of Physics and Astronomy, University of Missouri-Kansas City, Kansas City, MO 64110 (United States); Zhao, Xiujian, E-mail: opluse@whut.edu.cn [State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070 (China)

    2017-07-15

    Highlights: • N-doped VO{sub 2}(M1) thin films have been synthesized by annealing in NH{sub 3} atmosphere. • The phase purity, microstructure and optical property of VO{sub 2} thin film can be regulated by NH{sub 3} concentration. • First-principles calculations have been carried out to study the mechanism of N-doping on energy band structures of VO{sub 2}(M1). • The energy band gaps of VO{sub 2}(M1) are tuned by substitution N-doping or interstitial N-doping. - Abstract: Research on monoclinic (M1) phase of VO{sub 2} has attracted a great of interest for smart coating applications due to its exceptional thermochromic property. Herein, we report the results using a novel approach to synthesize N-doped VO{sub 2}(M1) thin films with high purity by heat treatment in NH{sub 3} atmosphere. The N dopant in the film can be regulated by varying NH{sub 3} concentration during the annealing process. We find that the N atoms are located at the interstitial sites or substitute oxygen atoms, and the V-N bonds in the VO{sub 2} thin films increase with NH{sub 3} concentration. The metal to insulator transition (MIT) temperature (τ{sub c,h}) of the VO{sub 2} thin film is effectively reduced from 80.0 to 62.9 °C, while the solar modulation efficiency (ΔT{sub sol}) and the modulation efficiency at 2000 nm (ΔT{sub 2000nm}) are 7.36% and 55.6% respectively. The band gap of N-doped VO{sub 2} thin films related to MIT (E{sub g1}) is estimated to be as low as 0.18–0.25 eV whereas the band gap associated with the visible transparency (E{sub g2}) is about 1.50–1.58 eV. Based on the highly accurate first-principles calculations, the E{sub g1} of VO{sub 2} (M1) is reduced after substituted or interstitial N-doping, while the E{sub g2} alters with the mode of N-doping, which is excellent agreement with experimental measurement.

  5. Influence of the spin quantum number $s$ on the zero-temperature phase transition in the square lattice $J$-$J'$ model

    OpenAIRE

    Darradi, R.; Richter, J.; Farnell, D. J. J.

    2004-01-01

    We investigate the phase diagram of the Heisenberg antiferromagnet on the square lattice with two different nearest-neighbor bonds $J$ and $J'$ ($J$-$J'$ model) at zero temperature. The model exhibits a quantum phase transition at a critical value $J'_c > J$ between a semi-classically ordered N\\'eel and a magnetically disordered quantum paramagnetic phase of valence-bond type, which is driven by local singlet formation on $J'$ bonds. We study the influence of spin quantum number $s$ on this p...

  6. Effect of heat-treatment on phase transition temperatures of a superelastic NiTi alloy for medical use

    Energy Technology Data Exchange (ETDEWEB)

    Yeung, K.W.K.; Cheung, K.M.C.; Lu, W.W.; Luk, K.D.K. [Univ. of Hong Kong (China). Dept. of Orthopaedic Surgery; Chung, C.Y. [City Univ. of Hong Kong, Kowloon (China). Dept. of Physics and Materials Science

    2002-07-01

    Surgical correction of scoliosis typically uses stainless steel or titanium alloy spinal instrumentation to straighten the scoliotic spine by 70% only. Our aim is to develop a method to overcome this by using an implantable superelastic (SE) nickel-titanium (NiTi) alloy rod, which will impose a continuous gradual correction force to the spine after the surgery so as to achieve a superior correction. More than 75 specimens made of a Ti-50.0 at% Ni alloy were treated by different heat treatment routes. The Austenitic transition temperature of the NiTi alloy can be adjusted to be available at 37.5 C by altering the heat treatment parameters: time and temperature of heat treatment. The experimental results showed that the heat treatment temperature should set between 400-500 C and the heat treatment time should be less than 60 minutes for the alloy. (orig.)

  7. Temperature-induced phase transitions for stuffed tridymites SrGa2O4 and CaGa2O4

    Science.gov (United States)

    Jiang, Fuwei; Jiang, Pengfei; Yue, Mufei; Gao, Wenliang; Cong, Rihong; Yang, Tao

    2017-10-01

    Temperature-induced phase transitions for stuffed tridymite AGa2O4 (A = Sr, Ca) were investigated by experimental and theoretical calculations. A simple annealing of SrCO3 and Ga2O3 led to the formation of γ-SrGa2O4 (P21/n) below 1200 °C, and transform to β-SrGa2O4 (P21/c) when heated at 1200 °C. A similar phenomenon was found for CaGa2O4, and the temperature boundary between α-CaGa2O4 (Pna21) and the high temperature polymorph β-CaGa2O4 (P21/c) was about 1350 °C. Rietveld refinements provided detailed structural information for these polymorphs and suggest that the driving force of these phase transitions is the under-bonded nature of the alkaline earth cations. In other words, the need of larger space for Sr2+/Ca2+ in the high temperature β-phase forces the 6-membered-ring channel expand through increasing the Ga-O-Ga angles. Density functional theory calculations proved the formation energies for γ-SrGa2O4 and α-CaGa2O4 were both lower than their high temperature β-polymorphs, in accordance with the experimental observations.

  8. Lowering of L1{sub 0} phase transition temperature of FePt thin films by single shot H{sup +} ion exposure using plasma focus device

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Z.Y.; Lin, J.J. [NSSE, National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616 (Singapore); Zhang, T. [School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798 (Singapore); Karamat, S.; Tan, T.L.; Lee, P.; Springham, S.V. [NSSE, National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616 (Singapore); Ramanujan, R.V. [School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798 (Singapore); Rawat, R.S. [NSSE, National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616 (Singapore)], E-mail: rajdeep.rawat@nie.edu.sg

    2009-02-27

    FePt thin films are exposed to pulsed energetic H{sup +} ion beam from plasma focus. In irradiated films, the phase transition from the low K{sub u} disordered face-centered-cubic structure to high K{sub u} ordered face-centered-tetragonal phase was achieved at 400 deg. C with the order parameter S ranging from 0.73 to 0.83, high coercivity of about 5356 kA/m, high negative nucleation field of about 7700 kA/m and high squareness ratio ranging from 0.73 to 0.79. The advantage of using plasma focus device is that it can lower phase transition temperature and significantly enhance the magnetic properties by a pulsed single shot exposure.

  9. Phase transitions of ε-HNIW in compound systems

    Directory of Open Access Journals (Sweden)

    Jing-yuan Zhang

    2016-05-01

    Full Text Available The heat-induced phase transitions of ε-HNIW, both neat and coated with various additives used in plastic bonded explosives, were investigated using powder X-ray diffraction and differential scanning calorimetry. It was found that ε-HNIW, after being held at 70°C for 60h, remained in the ε-phase. Applying other conditions, various phase transition parameters were determined, including Tc (the critical phase transition temperature, T50 (the temperature at which 50% of the phase transition is complete and T180 (the percentage of γ-HNIW present in samples heated to 180°C. According to the above three parameters, additives were divided into three categories: those that delay phase transition, those that raise the critical temperature and the transition rate, and those that promote the phase transition. Based on the above data, a phase transition mechanism is proposed.

  10. The Structural Phase Transition in Octaflournaphtalene

    DEFF Research Database (Denmark)

    Mackenzie, Gordon A.; Arthur, J. W.; Pawley, G. S.

    1977-01-01

    The phase transition in octafluoronaphthalene has been investigated by Raman scattering and neutron powder diffraction. The weight of the experimental evidence points to a unit cell doubling in the a direction, but with no change in space group symmetry. Lattice dynamics calculations support...... this evidence and indicate that the mechanism of the phase transition may well be the instability of a zone boundary acoustic mode of librational character. The structure of the low-temperature phase has been refined and the Raman spectra of the upper and lower phases are reported....

  11. Non-equilibrium phase transitions

    CERN Document Server

    Henkel, Malte; Lübeck, Sven

    2009-01-01

    This book describes two main classes of non-equilibrium phase-transitions: (a) static and dynamics of transitions into an absorbing state, and (b) dynamical scaling in far-from-equilibrium relaxation behaviour and ageing. The first volume begins with an introductory chapter which recalls the main concepts of phase-transitions, set for the convenience of the reader in an equilibrium context. The extension to non-equilibrium systems is made by using directed percolation as the main paradigm of absorbing phase transitions and in view of the richness of the known results an entire chapter is devoted to it, including a discussion of recent experimental results. Scaling theories and a large set of both numerical and analytical methods for the study of non-equilibrium phase transitions are thoroughly discussed. The techniques used for directed percolation are then extended to other universality classes and many important results on model parameters are provided for easy reference.

  12. Multiobjective Optimization and Phase Transitions

    CERN Document Server

    Seoane, Luís F

    2015-01-01

    Many complex systems obey to optimality conditions that are usually not simple. Conflicting traits often interact making a Multi Objective Optimization (MOO) approach necessary. Recent MOO research on complex systems report about the Pareto front (optimal designs implementing the best trade-off) in a qualitative manner. Meanwhile, research on traditional Simple Objective Optimization (SOO) often finds phase transitions and critical points. We summarize a robust framework that accounts for phase transitions located through SOO techniques and indicates what MOO features resolutely lead to phase transitions. These appear determined by the shape of the Pareto front, which at the same time is deeply related to the thermodynamic Gibbs surface. Indeed, thermodynamics can be written as an MOO from where its phase transitions can be parsimoniously derived; suggesting that the similarities between transitions in MOO-SOO and Statistical Mechanics go beyond mere coincidence.

  13. Structural evolution versus temperature of the β0 phase of the {n- eicosane}/{n- docosane} system: rotator transitions

    Science.gov (United States)

    Dirand, M.; Achour-Boudjema, Z.

    1996-02-01

    The orthorhombic phase {β 0[n- C20H42}/{n- C22H46] } (Fmmm) determined by Gerson and Nyburg is isostructural with the orthorhombic Rotator phase β-RI (Fmmm), observed in n-tricosane( n-C 23H 48) and n-pentacosane( n-C 25H 52) and in the two binary systems: [ {n- C22H46}/{n- C24H50}] and [ {n- C24H50}/{n- C26H54}]. When the temperature increases, its {b}/{a} ratio changes progressively from 1.51 at 293 K to 1.73 at 309 K; it then transforms into the rhombohedral Rotator phase α-RII (R 3¯ m) just below the solidus curve. These observations allow generalization of structural behaviour of two n-alkane mixtures (19 < n < 27), whose difference between carbon numbers is equal to 1 or 2.

  14. X-ray diffraction and Raman spectroscopy studies of temperature and composition induced phase transitions in Ba{sub 2-x}Sr{sub x}ZnWO{sub 6} (0 {<=} x {<=} 2) double perovskite oxides

    Energy Technology Data Exchange (ETDEWEB)

    Manoun, Bouchaib, E-mail: manounb@gmail.com [Equipe Materiaux et environnement, Laboratoire des Procedes de Valorisation des Ressources Naturelles, des Materiaux et Environnement, FST Settat, Universite Hassan 1er, (Morocco); Ezzahi, A. [Equipe Materiaux et environnement, Laboratoire des Procedes de Valorisation des Ressources Naturelles, des Materiaux et Environnement, FST Settat, Universite Hassan 1er, (Morocco); Benmokhtar, S. [LRCPGM, Laboratoire de Recherche de Chimie-Physique Generale des Materiaux, Department of Chemistry, Faculty of Sciences Ben M' Sik, Casablanca (Morocco); Ider, A. [Equipe Materiaux et environnement, Laboratoire des Procedes de Valorisation des Ressources Naturelles, des Materiaux et Environnement, FST Settat, Universite Hassan 1er, (Morocco); Lazor, P. [Department of Earth Sciences, Uppsala University, SE-752 36, Uppsala (Sweden); Bih, L. [Laboratoire de Physico-Chimie des Materiaux, Departement de Chimie, FST Errachidia (Morocco); Igartua, J.M. [Fisika Aplikatua II, Zientzia eta Teknologia Fak., UPV/EHU, PB 644, Bilbao 48080 (Spain)

    2012-08-25

    Highlights: Black-Right-Pointing-Pointer Synthesis and characterization of new double perovskites. Black-Right-Pointing-Pointer High temperature studies of double perovskite using Raman spectroscopy. Black-Right-Pointing-Pointer Temperature and compositions induced phase transitions in these materials. Black-Right-Pointing-Pointer Structural determination/refinement of these compounds as a function of composition. - Abstract: X-ray diffraction and Raman spectroscopy studies of Sr doped double perovskites compound Ba{sub 2-x}Sr{sub x}ZnWO{sub 6} with (0 {<=} x {<=} 2) were investigated. As a function of composition while increasing strontium amount, the samples show two phase transitions from cubic to tetragonal phase and from tetragonal to monoclinic structure. Both Rietveld refinements and Raman studies showed that the first phase transition occurs between x = 1 and 1.2; the second phase transition is observed around x = 2. Furthermore, increasing the temperature for the compositions (1.2 {<=} x < 2), manifests the tetragonal to cubic phase transition. For x = 2 two phase transitions were observed as a function of temperature. For this series, the phase transitions are illustrated by considerable changes in the composition and temperature dependence of the modes. All the Raman modes show a linear behavior when the composition or temperature is increased, then the slope change indicating the symmetry change.

  15. Silicon nanocrystals at elevated temperatures: retention of photoluminescence and diamond silicon to β-silicon carbide phase transition.

    Science.gov (United States)

    Rowland, Clare E; Hannah, Daniel C; Demortière, Arnaud; Yang, Jihua; Cook, Russell E; Prakapenka, Vitali B; Kortshagen, Uwe; Schaller, Richard D

    2014-09-23

    We report the photoluminescence (PL) properties of colloidal Si nanocrystals (NCs) up to 800 K and observe PL retention on par with core/shell structures of other compositions. These alkane-terminated Si NCs even emit at temperatures well above previously reported melting points for oxide-embedded particles. Using selected area electron diffraction (SAED), powder X-ray diffraction (XRD), liquid drop theory, and molecular dynamics (MD) simulations, we show that melting does not play a role at the temperatures explored experimentally in PL, and we observe a phase change to β-SiC in the presence of an electron beam. Loss of diffraction peaks (melting) with recovery of diamond-phase silicon upon cooling is observed under inert atmosphere by XRD. We further show that surface passivation by covalently bound ligands endures the experimental temperatures. These findings point to covalently bound organic ligands as a route to the development of NCs for use in high temperature applications, including concentrated solar cells and electrical lighting.

  16. Investigation of the Influence of Sucrose and Cholesterol on the Phase Transition Temperature of nanoliposomal formulation besides using particle size Reduction Techniques (Ultrasonication/High Pressure Homogenization

    Directory of Open Access Journals (Sweden)

    Z Malaei-Balasi

    2017-05-01

    Full Text Available Introduction: The successful application of nanoliposoms as an effective drug delivery system depends on their stability in the medium. In this article, influence of additive materials such as cholesterol and sucrose besides two natural and synthesized phospholipids have been investigated. Methods: In the present study, designing and synthesis of nanoliposomal formulations were prepared using thin film method. This liposomal suspension was downsized by two methods, the high-pressure homogenizer and ultrasound to form small unilamellar vesicles. The size distributions, zeta potentials and phase transition temperature of formulations were all determined by a zetasizer and differential scanning calorimetry(DSC. In addition, the contribution of nanoliposomal formulation has been investigated by HPLC and FTIR methods. Results: Results of the DSC measurments indicated that incorporation of unsaturated phospholipid (SOY PC may cause phase separation with partial miscibility in the liposome bilayer containing of DPPG. The optimal nanoliposomal formulation was composed of (DPPC: CHOL: mPEG2000-DSPE with the mole percents equal to (83:15:2, respectively. In addition, sucrose has been used in the formulation with a total amounts six times greater than that of the lipids. The properties of optimized nanoliposome have been shown as the size average 104nm, zeta potential 8.04mv and phase transition temperature of lipid less than 37°C which were stable enough to be utilized for loading and releasing bioactives in body temperature. Conclusion: Finally the produced nanoliposomes were stable vesicles in the proper size, phase transition temperature and surface charge without any aggregation and fusion.

  17. Phase Transitions in Quantum Pattern Recognition

    CERN Document Server

    Trugenberger, Carlo Andrea

    2002-01-01

    With the help of quantum mechanics one can formulate a model of associative memory with optimal storage capacity. I generalize this model by introducing a parameter playing the role of an effective temperature. The corresponding thermodynamics provides criteria to tune the efficiency of quantum pattern recognition. I show that the associative memory undergoes a phase transition from a disordered high-temperature phase with no correlation between input and output to an ordered, low-temperature phase with minimal input-output Hamming distance.

  18. The determination of the phase transition temperatures of a semifluorinated liquid crystalline biphenyl ester by impedance spectroscopy as an alternative method

    Energy Technology Data Exchange (ETDEWEB)

    Yıldız, Alptekin [Istanbul Technical University, Department of Physics Engineering, Maslak, 34469 Istanbul (Turkey); Yildiz Technical University, Department of Physics, 34220 Istanbul (Turkey); Canli, Nimet Yilmaz, E-mail: niyilmaz@yahoo.com [Yildiz Technical University, Department of Physics, 34220 Istanbul (Turkey); Karanlık, Gürkan; Ocak, Hale [Yildiz Technical University, Department of Chemistry, 34220 Istanbul (Turkey); Okutan, Mustafa [Yildiz Technical University, Department of Physics, 34220 Istanbul (Turkey); Eran, Belkız Bilgin [Yildiz Technical University, Department of Chemistry, 34220 Istanbul (Turkey)

    2016-12-15

    Dielectric spectroscopy (DS) is a very powerful and important for better understanding of the molecular dynamics and relaxation phenomena in liquid crystals. The dielectric and impedance characteristics Ethyl 4-(7,7,8,8,9,9,10,10,10-nonafluorodecyloxy)biphenyl-4′-carboxylate (ENBC) liquid crystal have been analyzed over the frequency range of 100 Hz to MHz in the temperature region from room temperature to 180 °C. The compound ENBC shows enantiotropic a smectic mesophase in a wide temperature range. The phase transition temperatures T (°C) of the liquid crystal ENBC, which were characterized by Differential Scanning Calorimetry (DSC), have been verified by the dielectric measurements and conductivity mechanisms of the ENBC. The activation energies for some selected angular frequencies have also been calculated.

  19. Phase stabilization of magnetite (Fe{sub 3}O{sub 4}) nanoparticles with B{sub 2}O{sub 3} addition: A significant enhancement on the phase transition temperature

    Energy Technology Data Exchange (ETDEWEB)

    Topal, Uğur, E-mail: ugur.topal@tubitak.gov.tr [TUBITAK-UME, National Metrology Institute, PK 54, 41470 Gebze-Kocaeli (Turkey); Aksan, Mehmet Ali [Inonu Universitesi, Fen Edebiyat Fakultesi, Fizik Bolumu 44280, Malatya (Turkey)

    2016-05-15

    Magnetite nanoparticles (MNPs) are extensively investigated for biomedical applications, particularly as contrast agents for Magnetic Resonance Imaging and as drug delivery agent and heat mediators for cancer therapy. Tuning the magnetic properties of the magnetite nanoparticles with doping of foreign atoms has a crucial importance for determining the application areas of these materials and so attracts much interests. On the other hand the doping with foreign atoms requires high temperature annealing, and it causes a phase transition to the hematite phase above 400 °C. In this work the phase transition temperature from the magnetite to the hematite phase has been increased by 200 °C, which is the highest enhancement reported in literature. It was achieved by addition of the appropriate amounts of B{sub 2}O{sub 3.} Our experiments indicates that the 5.0 wt% of B{sub 2}O{sub 3} addition stabilizes and keeps the existence of single phase magnetite up to 600 °C. - Highlights: • B{sub 2}O{sub 3} addition to magnetite nanoparticles enhances the superparamagnetism. • The phase transition temperature of magnetite to hematite increases by 200 °C. • B{sub 2}O{sub 3} addition increases the activation energy of magnetite.

  20. Measurement of the dynamic behavior of thin poly(N-isopropylacrylamide) hydrogels and their phase transition temperatures measured using reflectometric interference spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Okada, Fuminori [Konica Minolta, INC. (Japan); Akiyama, Yoshikatsu, E-mail: akiyama.yoshikatsu@twmu.ac.jp, E-mail: akiyama.yoshikatsu@abmes.twmu.ac.jp; Kobayashi, Jun [Tokyo Women’s Medical University (TWIns), Institute of Advanced Biomedical Engineering and Science (Japan); Ninomiya, Hidetaka [Konica Minolta, INC. (Japan); Kanazawa, Hideko [Keio University, Faculty of Pharmacy (Japan); Yamato, Masayuki; Okano, Teruo [Tokyo Women’s Medical University (TWIns), Institute of Advanced Biomedical Engineering and Science (Japan)

    2015-03-15

    Temperature-responsive cell culture surfaces prepared by modifying tissue-culture polystyrene with nanoscale poly(N-isopropylacrylamide) (PIPAAm) hydrogels are widely used as intelligent surfaces for the fabrication of various cell sheets that change with temperature. In this work, the characteristics of nanoscale PIPAAm hydrogels were phenomenologically elucidated on the basis of time-dependent surface evaluations under conditions of changing temperature. Because the dynamic characteristics of the nanoscale hydrogel did not exhibit good performance, the nanoscale PIPAAm hydrogel was analyzed by monitoring its temperature-dependent dynamic swelling/deswelling changes using reflectometric interference spectroscopy (RIfS) on an instrument equipped with a microfluidic system. RIfS measurements under ambient atmosphere provided the precise physical thickness of the dry PIPAAm hydrogel (6.7 nm), which agreed with the atomic force microscopy results (6.6 nm). Simulations of the reflectance spectra revealed that changes in the wavelength of the minimum reflectance (Δλ) were attributable to the changes in the refractive index of the thin PIPAAm hydrogel induced by a temperature-dependent volume phase transition. The temperature-dependent Δλ change was used to monitor the swelling/deswelling behavior of the nanoscale PIPAAm hydrogel. In addition, the phase transition temperature of the thin PIPAAm hydrogel under aqueous conditions was also determined to be the inflection point of the plot of the change in Δλ as a function of temperature. The dynamic behavior of a thin PIPAAm hydrogel chemically deposited on a surface was readily analyzed using a new analytical system with RIfS and microfluidic devices.

  1. A crystalline-to-crystalline phase transition in Ca(OH)2 at 8 GPa and room temperature

    Science.gov (United States)

    Catalli, K.; Shim, S.-H.; Prakapenka, V. B.

    2008-03-01

    X-ray diffraction and Raman spectroscopy measurements reveal that Ca(OH)2-portlandite transforms to a crystalline phase with an ordered OH sublattice between 8 and 14 GPa at room temperature under quasi-hydrostatic stress conditions in an Ar pressure medium. The amorphization previously reported at 11 GPa under no pressure medium was not observed up to 26 GPa. The width and separation of the fluorescence peaks from the ruby chips embedded in Ca(OH)2 without a medium suggest that deviatoric stress is responsible for the previously observed amorphization. Our study demonstrates that the behavior of hydrous phases in the subducting slab could be sensitive to local deviatoric stresses. Together with similar reports on quartz, our observation on Ca(OH)2 indicates that deviatoric stress is an important factor to consider for P-induced amorphization reported in a wide range of materials.

  2. A crystalline-to-crystalline phase transition in Ca(OH)[subscript 2] at 8 GPa and room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Catalli, K.; Shim, S.-H.; Prakapenka, V.B. (MIT); (UC)

    2008-07-02

    X-ray diffraction and Raman spectroscopy measurements reveal that Ca(OH){sub 2}-portlandite transforms to a crystalline phase with an ordered OH sublattice between 8 and 14 GPa at room temperature under quasi-hydrostatic stress conditions in an Ar pressure medium. The amorphization previously reported at 11 GPa under no pressure medium was not observed up to 26 GPa. The width and separation of the fluorescence peaks from the ruby chips embedded in Ca(OH){sub 2} without a medium suggest that deviatoric stress is responsible for the previously observed amorphization. Our study demonstrates that the behavior of hydrous phases in the subducting slab could be sensitive to local deviatoric stresses. Together with similar reports on quartz, our observation on Ca(OH){sub 2} indicates that deviatoric stress is an important factor to consider for P-induced amorphization reported in a wide range of materials.

  3. Composite hydrogels with temperature sensitive heterogeneities: influence of gel matrix on the volume phase transition of embedded poly-(N-isopropylacrylamide) microgels.

    Science.gov (United States)

    Meid, Judith; Friedrich, Tatjana; Tieke, Bernd; Lindner, Peter; Richtering, Walter

    2011-02-28

    The thermo-responsive behaviour of poly-(N-isopropylacrylamide) (PNiPAM) microgels embedded in covalently cross-linked non-temperature-sensitive polyacrylamide (PAam) hydrogel matrixes with different compositions was investigated by using small angle neutron scattering (SANS). The composition of the composite hydrogel was varied by (a) increasing the cross-linker and acrylamide concentration leading to strong hydrogel matrixes and (b) by increasing the microgel concentration to obtain composite gels with an internal structure. Additionally we synthesized composite hydrogels by using γ-irradiation as initiation for the polymerisation. This leads to the formation of chemical bonds between the PNiPAM microgels and the surrounding polyacrylamide matrix. Thus it is possible to synthesize hydrogels without an additional cross-linker, as well as pure particle networks. Some samples were prepared at two different temperatures, below and above the volume phase transition temperature of PNiPAM, resulting in highly swollen or totally collapsed microgels during the incorporation step. The volume phase transition of microgels is not influenced by a hydrogel matrix with high acrylamide concentration independent of the preparation temperature. However, an increased cross-linker concentration leads to a corset like constraint on microgel swelling. Microgels, which are embedded in the collapsed state (at 50 °C), are not able to swell upon cooling, whereas microgels embedded in the swollen state can collapse upon heating. For samples with an increased microgel concentration, the close microgel packing was disturbed by the formation of the polyacrylamide matrix. The hydrogel matrix squeezes the microgels together and leads to partial aggregation. The experiments demonstrate how composite hydrogels with stimuli-sensitive heterogeneities can be prepared such that the full responsiveness of the embedded microgels is retained while the macroscopic dimensions of the gel are not affected

  4. Sudden transition from finite temperature spin environments

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Zheng-Da; He, Qi-Liang; Xu, Hang-Shi [Zhejiang Institute of Modern Physics and Physics Department, Zhejiang University, Hangzhou 310027 (China); Xu, Jing-Bo, E-mail: xujb@zju.edu.cn [Zhejiang Institute of Modern Physics and Physics Department, Zhejiang University, Hangzhou 310027 (China)

    2012-10-01

    We investigate the phenomenon of sudden transition from finite temperature critical environments in the study of quantum correlations of a two-qubit system coupled to independent thermal Ising baths. The influence of the temperature and external field of bath on the critical time of sudden transition is also explored. It is found that the phenomenon of sudden transition can be used to detect the critical points of thermal spin environments. How to protect quantum correlations of the system is also examined by applying a series of π-phase pulses. -- Highlights: ► The sudden transition phenomenon from thermal critical environments is studied. ► How to detect quantum critical points of thermal Ising baths is explored. ► The quantum discord can be protected against thermal bath by π-phase pulses.

  5. Theory of phase transitions rigorous results

    CERN Document Server

    Sinai, Ya G

    1982-01-01

    Theory of Phase Transitions: Rigorous Results is inspired by lectures on mathematical problems of statistical physics presented in the Mathematical Institute of the Hungarian Academy of Sciences, Budapest. The aim of the book is to expound a series of rigorous results about the theory of phase transitions. The book consists of four chapters, wherein the first chapter discusses the Hamiltonian, its symmetry group, and the limit Gibbs distributions corresponding to a given Hamiltonian. The second chapter studies the phase diagrams of lattice models that are considered at low temperatures. The no

  6. Simple Fermionic Model of Deconfined Phases and Phase Transitions

    Science.gov (United States)

    Assaad, F. F.; Grover, Tarun

    2016-10-01

    Using quantum Monte Carlo simulations, we study a series of models of fermions coupled to quantum Ising spins on a square lattice with N flavors of fermions per site for N =1 , 2, and 3. The models have an extensive number of conserved quantities but are not integrable, and they have rather rich phase diagrams consisting of several exotic phases and phase transitions that lie beyond the Landau-Ginzburg paradigm. In particular, one of the prominent phases for N >1 corresponds to 2 N gapless Dirac fermions coupled to an emergent Z2 gauge field in its deconfined phase. However, unlike a conventional Z2 gauge theory, we do not impose "Gauss's Law" by hand; instead, it emerges because of spontaneous symmetry breaking. Correspondingly, unlike a conventional Z2 gauge theory in two spatial dimensions, our models have a finite-temperature phase transition associated with the melting of the order parameter that dynamically imposes the Gauss's law constraint at zero temperature. By tuning a parameter, the deconfined phase undergoes a transition into a short-range entangled phase, which corresponds to Néel antiferromagnet or superconductor for N =2 and a valence-bond solid for N =3 . Furthermore, for N =3 , the valence-bond solid further undergoes a transition to a Néel phase consistent with the deconfined quantum critical phenomenon studied earlier in the context of quantum magnets.

  7. Simple Fermionic Model of Deconfined Phases and Phase Transitions

    Directory of Open Access Journals (Sweden)

    F. F. Assaad

    2016-12-01

    Full Text Available Using quantum Monte Carlo simulations, we study a series of models of fermions coupled to quantum Ising spins on a square lattice with N flavors of fermions per site for N=1, 2, and 3. The models have an extensive number of conserved quantities but are not integrable, and they have rather rich phase diagrams consisting of several exotic phases and phase transitions that lie beyond the Landau-Ginzburg paradigm. In particular, one of the prominent phases for N>1 corresponds to 2N gapless Dirac fermions coupled to an emergent Z_{2} gauge field in its deconfined phase. However, unlike a conventional Z_{2} gauge theory, we do not impose “Gauss’s Law” by hand; instead, it emerges because of spontaneous symmetry breaking. Correspondingly, unlike a conventional Z_{2} gauge theory in two spatial dimensions, our models have a finite-temperature phase transition associated with the melting of the order parameter that dynamically imposes the Gauss’s law constraint at zero temperature. By tuning a parameter, the deconfined phase undergoes a transition into a short-range entangled phase, which corresponds to Néel antiferromagnet or superconductor for N=2 and a valence-bond solid for N=3. Furthermore, for N=3, the valence-bond solid further undergoes a transition to a Néel phase consistent with the deconfined quantum critical phenomenon studied earlier in the context of quantum magnets.

  8. Learning phase transitions by confusion

    Science.gov (United States)

    van Nieuwenburg, Evert P. L.; Liu, Ye-Hua; Huber, Sebastian D.

    2017-02-01

    Classifying phases of matter is key to our understanding of many problems in physics. For quantum-mechanical systems in particular, the task can be daunting due to the exponentially large Hilbert space. With modern computing power and access to ever-larger data sets, classification problems are now routinely solved using machine-learning techniques. Here, we propose a neural-network approach to finding phase transitions, based on the performance of a neural network after it is trained with data that are deliberately labelled incorrectly. We demonstrate the success of this method on the topological phase transition in the Kitaev chain, the thermal phase transition in the classical Ising model, and the many-body-localization transition in a disordered quantum spin chain. Our method does not depend on order parameters, knowledge of the topological content of the phases, or any other specifics of the transition at hand. It therefore paves the way to the development of a generic tool for identifying unexplored phase transitions.

  9. Percolation Phase Transition of Surface Air Temperature Networks: A new test bed for El Niño/La Niña simulations.

    Science.gov (United States)

    Hua, Lijuan; Lu, Zhenghui; Yuan, Naiming; Chen, Lin; Yu, Yongqiang; Wang, Lu

    2017-08-16

    In this work, we studied the air-sea interaction over the tropical central eastern Pacific from a new perspective, climate network. The surface air temperatures over the tropical Pacific were constructed as a network, and the nodes within this network were linked if they have a similar temporal varying pattern. Using three different reanalysis datasets, we verified the percolation phase transition. That is, when the influences of El Niño/La Niña are strong enough to isolate more than 48% of the nodes, the network may abruptly be divided into many small pieces, indicating a change of the network state. This phenomenon was reproduced successfully by a coupled general circulation model, Flexible Global Ocean-Atmosphere-Land System Model Spectral Version 2, but another model, Flexible Global Ocean-Atmosphere-Land System Model Grid-point Version 2, failed. As both models have the same oceanic component, but are with different atmospheric components, the improperly used atmospheric component should be responsible for the missing of the percolation phase transition. Considering that this new phenomenon is only recently noticed, current state-of-the-art models may ignore this process and induce unrealistic simulations. Accordingly, percolation phase transition is proposed as a new test bed, which deserves more attention in the future.

  10. Detecting phase transitions in a CaCl2-H2O system at low temperatures using a fiber-optic Fresnel reflection sensor.

    Science.gov (United States)

    Priyadarshini, Mani; Machavaram, Venkata Rajanikanth; Sivaramakrishna, Akella; Arulmozhivarman, Pachiyappan

    2017-04-10

    Temperature-induced crystallization events in an aqueous calcium chloride solution in the concentration range of 15-40 mass% are monitored using an optical fiber Fresnel reflection sensor in the temperature range of 30°C to -200°C. The deviation of the phase boundary from equilibrium and the formation of an eutectic mixture followed by its densification during rapid cooling are inferred from the distinct signatures of the optical fiber sensor via the changes in refractive index. During the natural heating at laboratory ambient conditions, the optical signals impart the completion of dissolution of ice and CaCl2·6H2O. The corresponding temperatures have been used in Linke's equations to obtain the salinities, which are in good agreement with the intended solution concentrations. The sensor signal imparts simultaneous melting of the constituents of the eutectic mixture of a 29.7 mass% solution during the natural heating phase. The persistence of the metastable liquid phase at -200°C for tens of minutes followed by solidification is observed at all the concentrations studied. Finally, the feasibility of monitoring phase transitions in a NaCl-CaCl2-H2O system has been demonstrated.

  11. Incommensurate phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Currat, R. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)

    1996-11-01

    We review the characteristic aspects of modulated crystals from the point of view of inelastic neutron scattering. We discuss the phenomenological Landau theory of the normal-to-incommensurate displacive instability and its predictions concerning the fluctuation spectrum of the modulated phase. General results on the form of the normal-mode eigenvectors and on the inelastic scattering channels through which they couple to the probe are established using the superspace approach. We illustrate these results on a simple discrete model symmetry and we review available inelastic neutron scattering data on several displacively modulated compounds. (author) 21 figs., 73 refs.

  12. Cosmological Inflation as a Quantum Phase Transition

    Science.gov (United States)

    Morikawa, M.

    1995-04-01

    The aim of this paper is to clarify the understanding of the fundamental dynamics in the time evolution of phase transitions based on quantum field theory. This formalism is particularly necessary for the inflationary phase transition in the early Universe when it is quenched in the effectively zero temperature phase. In this situation, quantum fluctuations dominate thermal fluctuations. We first critically review the standard scenario of the inflationary phase transition: the problem of defining the order parameter, the problem of complex and non-convex effective potentials etc. In order to solve these fundamental problems, we develop the formalism of non-equilibrium quantum firld theory. In the process, we a) define the local order parameter relevant for the dynamics of phase transitions in this formalism, and compare this local order parameter with the ordinary global order parameter, b) systematically describe the dissipation and fluctuation effects induced from the special type of radiative corrections (in-in formalism of quantum field theory), c) derive the equation of motion for the local order parameter which becomes a generalized Langevin-type stochastic differential equation, d) argue that dissipative effects destroy the quantum coherence of the system and demonstrate that the ordinary quantum theory based on a single Hilbert space is not sufficient, e) expound upon the validity of using the effective potential for the dynamics of phase transitions, and finally, f) demonstrate that the unstable self-coupling scalar field can actually induce the dissipative effects, and derive the equation of motion for the order parameter.

  13. A study on the change in the phase transition temperature of TiSi sub 2 by adding the Zr element on different Si substrates

    CERN Document Server

    Yoon, S H

    1999-01-01

    The stabilization of C49 TiSi sub 2 at high temperature was investigated by adding Zr element to Ti-silicide both on single crystalline Si(100) and amorphous Si substrates. This stabilization of the C49 TiSi sub 2 phase, which exhibits lower surface and interface energies than those of the C54 TiSi sub 2 phase, was expected to suppress the problems of Ti-silicide, such as the phase transition and the agglomeration. Ti and Zr films of 40 nm were co-deposited on Si substrates in a dual e-beam evaporation system equipped with an ion pump and at a base pressure of approx 5x10 sup - sup 9 Torr. The amounts of Zr contents added to the Ti-silicide were 5, 10 and 20 atomic %, and the thicknesses were monitored by in-situ quartz-crystal thickness monitors. After the deposition, films were annealed by using an ex-situ vacuum furnace at temperatures between 600 .deg. C and 900 .deg. C in 100 .deg. C increments. The phase identification and the chemical compositions were investigated by X-ray diffraction (XRD) and Auger ...

  14. Phase transitions in operational risk.

    Science.gov (United States)

    Anand, Kartik; Kühn, Reimer

    2007-01-01

    In this paper we explore the functional correlation approach to operational risk. We consider networks with heterogeneous a priori conditional and unconditional failure probability. In the limit of sparse connectivity, self-consistent expressions for the dynamical evolution of order parameters are obtained. Under equilibrium conditions, expressions for the stationary states are also obtained. Consequences of the analytical theory developed are analyzed using phase diagrams. We find coexistence of operational and nonoperational phases, much as in liquid-gas systems. Such systems are susceptible to discontinuous phase transitions from the operational to nonoperational phase via catastrophic breakdown. We find this feature to be robust against variation of the microscopic modeling assumptions.

  15. Giant Volume Change and Topological Gaps in Temperature- and Pressure-Induced Phase Transitions: Experimental and Computational Study of ThMo2 O8.

    Science.gov (United States)

    Xiao, Bin; Kegler, Philip; Gesing, Thorsten M; Robben, Lars; Blanca-Romero, Ariadna; Kowalski, Piotr M; Li, Yan; Klepov, Vladislav; Bosbach, Dirk; Alekseev, Evgeny V

    2016-01-18

    By applying high temperature (1270 K) and high pressure (3.5 GPa), significant changes occur in the structural volume and crystal topology of ThMo2 O8 , allowing the formation of an unexpected new ThMo2 O8 polymorph (high-temperature/high-pressure (HT/HP) orthorhombic ThMo2 O8 ). Compared with the other three ThMo2 O8 polymorphs prepared at the ambient pressure (monoclinic, orthorhombic, and hexagonal phases), the molar volume for the quenched HT/HP-orthorhombic ThMo2 O8 is decreased by almost 20 %. As a result of such a dramatic structural transformation, a permanent high-pressure quenchable state is able to be sustained when the pressure is released. The crystal structures of the three ambient ThMo2 O8 phases are based on three-dimensional (3D) frameworks constructed from corner-sharing ThOx (x=6, 8, or 9) polyhedra and MoO4 tetrahedra. The HT/HP-orthorhombic ThMo2 O8 , however, crystallizes in a novel structural topology, exhibiting very dense arrangements of ThO11 and MoO4+1 polyhedra connecting along the crystallographic c axis. The phase transitions among all four of these ThMo2 O8 polymorphs are unveiled and fully characterized with regard to the structural transformation, thermal stability, and vibrational properties. The complementary first principles calculations of Gibbs free energies reveal the underlying energetics of the phase transition, which support the experimental findings. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Phase transitions in finite systems

    Energy Technology Data Exchange (ETDEWEB)

    Chomaz, Ph. [Grand Accelerateur National d' Ions Lourds (GANIL), DSM-CEA / IN2P3-CNRS, 14 - Caen (France); Gulminelli, F. [Caen Univ., 14 (France). Lab. de Physique Corpusculaire

    2002-07-01

    In this series of lectures we will first review the general theory of phase transition in the framework of information theory and briefly address some of the well known mean field solutions of three dimensional problems. The theory of phase transitions in finite systems will then be discussed, with a special emphasis to the conceptual problems linked to a thermodynamical description for small, short-lived, open systems as metal clusters and data samples coming from nuclear collisions. The concept of negative heat capacity developed in the early seventies in the context of self-gravitating systems will be reinterpreted in the general framework of convexity anomalies of thermo-statistical potentials. The connection with the distribution of the order parameter will lead us to a definition of first order phase transitions in finite systems based on topology anomalies of the event distribution in the space of observations. Finally a careful study of the thermodynamical limit will provide a bridge with the standard theory of phase transitions and show that in a wide class of physical situations the different statistical ensembles are irreducibly inequivalent. (authors)

  17. Extracellular ice phase transitions in insects.

    Science.gov (United States)

    Hawes, T C

    2014-01-01

    At temperatures below their temperature of crystallization (Tc), the extracellular body fluids of insects undergo a phase transition from liquid to solid. Insects that survive the transition to equilibrium (complete freezing of the body fluids) are designated as freeze tolerant. Although this phenomenon has been reported and described in many Insecta, current nomenclature and theory does not clearly delineate between the process of transition (freezing) and the final solid phase itself (the frozen state). Thus freeze tolerant insects are currently, by convention, described in terms of the temperature at which the crystallization of their body fluids is initiated, Tc. In fact, the correct descriptor for insects that tolerate freezing is the temperature of equilibrium freezing, Tef. The process of freezing is itself a separate physical event with unique physiological stresses that are associated with ice growth. Correspondingly there are a number of insects whose physiological cryo-limits are very specifically delineated by this transitional envelope. The distinction also has considerable significance for our understanding of insect cryobiology: firstly, because the ability to manage endogenous ice growth is a fundamental segregator of cryotype; and secondly, because our understanding of internal ice management is still largely nascent.

  18. Chiral phase transition from string theory.

    Science.gov (United States)

    Parnachev, Andrei; Sahakyan, David A

    2006-09-15

    The low energy dynamics of a certain D-brane configuration in string theory is described at weak t'Hooft coupling by a nonlocal version of the Nambu-Jona-Lasinio model. We study this system at finite temperature and strong t'Hooft coupling, using the string theory dual. We show that for sufficiently low temperatures chiral symmetry is broken, while for temperatures larger then the critical value, it gets restored. We compute the latent heat and observe that the phase transition is of the first order.

  19. Infrared studies of temperature-dependent phase transitions in ammonium sulfate aerosol and the development of a visible light scattering technique to measure atmospheric particle compositions

    Science.gov (United States)

    Onasch, Timothy Bruce

    1999-10-01

    Sulfate containing particles exist globally throughout the atmosphere and impact its chemistry and radiative properties. Under the low temperature conditions found in the upper troposphere and lower stratosphere, sulfate particles act as nuclei for cirrus clouds and facilitate heterogeneous reactions which affect ozone chemistry. Both of these processes are dependent upon the chemical composition and phase of the background aerosol, and thus the behavior of these particles at low temperatures. This thesis represents two approaches undertaken to investigate the composition and phase of atmospheric aerosols. First, a flow tube system has been developed to study the low temperature behavior of atmospherically relevant particles within a controlled laboratory environment. Second, a visible light scattering technique has been developed to characterize the physical properties of particles in situ from an aircraft platform. The relative humidities of temperature-dependent phase transitions in ammonium sulfate aerosols were measured within a flow tube system. A chilled-mirror hygrometer measured the relative humidity and Fourier transform infrared spectroscopy was utilized to probe the phase of the particles and to characterize their microphysical properties. The relative humidity of deliquescence changed from 80% to 82% over the temperature range from 294.8 K to 258.0 K, in agreement with thermodynamic theory. The efflorescence relative humidity of submicron ammonium sulfate particles increased slightly from 32% to 39% as the temperature decreased from 294.8 K to 234.3 K. The latter result suggests that salt particles may exist as metastable solution droplets under low relative humidity conditions for significant time periods in the upper troposphere. To measure particle refractive indices in situ, a visible light scattering technique based on NCAR's Multiangle Aerosol Spectrometer Probe (MASP) was developed. The MASP was calibrated with monodisperse particles having

  20. Phase transitions and critical phenomena

    CERN Document Server

    Domb, Cyril

    2001-01-01

    The field of phase transitions and critical phenomena continues to be active in research, producing a steady stream of interesting and fruitful results. It has moved into a central place in condensed matter studies.Statistical physics, and more specifically, the theory of transitions between states of matter, more or less defines what we know about 'everyday' matter and its transformations.The major aim of this serial is to provide review articles that can serve as standard references for research workers in the field, and for graduate students and others wishing to obtain reliable in

  1. Unraveling Crystal Growth in GeSb Phase-Change Films in between the Glass-Transition and Melting Temperatures

    NARCIS (Netherlands)

    Eising, Gert; Van Damme, Tobias; Kooi, Bart J.

    The study of crystal growth in phase-change thin films is of crucial importance to improve our understanding of the extraordinary phase transformation kinetics of these materials excellently suited for data storage applications. Here, we developed and used a new method, based on isothermal heating

  2. Low temperature vibrational spectroscopy. II. Evidence for order–disorder phase transitions due to weak C–H···Cl hydrogen bonding in tetramethylammonium hexachloroplatinate (IV), -tellurate (IV), and -stannate (IV) and the related perdeuterated compounds

    DEFF Research Database (Denmark)

    Berg, Rolf W.

    1978-01-01

    and it is suggested that the phase transitions are caused by an ordering of rotationally disordered methyl groups via the formation of weak C–H···Cl hydrogen bonds at low temperatures. The transition temperatures and hence the interactions are shown to depend on both the kind of hydrogen isotope and metal present...... torsions and other noncubic features play a role, especially in spectra at low temperatures. Possible site symmetries of the [PtCl6]2− ion, which cannot have strictly Oh symmetry in either phase, have been deduced. The spectra of a mixed Pt : Te compound showed that the hexachlorometallate anions vibrate...

  3. Temperature-Dependent Phase Transition in Orthorhombic [011]c Pb(Mg1/3Nb2/3 O3-0.35PbTiO3 Single Crystal

    Directory of Open Access Journals (Sweden)

    Wenhui He

    2014-07-01

    Full Text Available Relaxor [011]c PMN-0.35PT single crystal phase transition characteristics are investigated through various methods including variable temperature dielectric properties, X-ray diffraction, bipolar ferroelectric hysteresis loops (P-E and electric-field-induced strain (S-E hysteresis loops measurements. The results reveal that two phase transitions exist within the range from room temperature to 250 °C: orthorhombic (O-tetragonal (T-cubic (C. The O-to-T and T-to-C phase transition temperatures have been identified as 84 °C and 152 °C, respectively. Diffuseness degree of the T-to-C phase transition for the unpoled single crystal has been calculated to be 1.56, implying an intermediate state between normal and relaxor ferroelectrics. Temperature-dependent remanent polarization (Pr, coercive field (Ec, saturation polarization (Ps, hysteresis loop squareness (Rsq, and longitudinal piezoelectric constant (d* 33 are also explored to learn the details of the phase transitions. Variable temperature unipolar Suni-E hysteresis loops avail additional evidence for the microstructure change in the as-measured single crystal.

  4. Phase transition of holographic entanglement entropy in massive gravity

    Directory of Open Access Journals (Sweden)

    Xiao-Xiong Zeng

    2016-05-01

    Full Text Available The phase structure of holographic entanglement entropy is studied in massive gravity for the quantum systems with finite and infinite volumes, which in the bulk is dual to calculating the minimal surface area for a black hole and black brane respectively. In the entanglement entropy–temperature plane, we find for both the black hole and black brane there is a Van der Waals-like phase transition as the case in thermal entropy–temperature plane. That is, there is a first order phase transition for the small charge and a second order phase transition at the critical charge. For the first order phase transition, the equal area law is checked and for the second order phase transition, the critical exponent of the heat capacity is obtained. All the results show that the phase structure of holographic entanglement entropy is the same as that of thermal entropy regardless of the volume of the spacetime on the boundary.

  5. Temperature-dependent phase transition and comparative investigation on enhanced magnetic and optical properties between sillenite and perovskite bismuth ferrite-rGO nanocomposites

    Science.gov (United States)

    Jalil, M. A.; Chowdhury, Sayeed Shafayet; Alam Sakib, Mashnoon; Enamul Hoque Yousuf, S. M.; Khan Ashik, Emran; Firoz, Shakhawat H.; Basith, M. A.

    2017-08-01

    The manuscript reports the synthesis as well as a comparative investigation of the structural, magnetic, and optical properties between sillenite and perovskite type bismuth ferrite-reduced graphene oxide nanocomposites. Graphite oxide is prepared using the modified Hummers' method, followed by hydrothermal synthesis of bismuth ferrite-reduced graphene oxide nanocomposites at different reaction temperatures. The X-ray diffraction measurements confirm the formation of perovskite type BiFeO3-rGO nanocomposites at a reaction temperature of 200 °C. This is the lowest temperature to obtain perovskite type BiFeO3-rGO nanocomposites under the reaction procedure adopted, however, a structural transition to sillenite type Bi25FeO40-rGO is observed at 180 °C. The FESEM images demonstrate that the particle size of the perovskite nanocomposite is 25-60 nm, and for the sillenite phase nanocomposite it is 10-30 nm. The as-synthesized nanocomposites exhibit significantly enhanced saturation magnetization over pure BiFeO3 nanoparticles, with the sillenite Bi25FeO40-rGO nanocomposite having higher saturation magnetization than perovskite BiFeO3-rGO. The optical characteristics of the as-synthesized nanocomposites demonstrate considerably higher absorbance in the visible range with significantly lower band gap in comparison to undoped BiFeO3. Again, the sillenite Bi25FeO40-rGO nanocomposite is shown to have a lower band gap compared to the perovskite counterpart. Our investigation provides a means of selective phase formation as desired between sillenite Bi25FeO40-rGO and perovskite BiFeO3-rGO by controlling the hydrothermal reaction temperature. The outcome of our investigation suggests that the formation of nanocomposite of sillenite bismuth ferrite with reduced graphene oxide is promising to improve the magnetic and optical properties for potential technological applications.

  6. Infield X-ray diffraction studies of field and temperature driven structural phase transition in Nd{sub 0.49}Sr{sub 0.51}MnO{sub 3+δ}

    Energy Technology Data Exchange (ETDEWEB)

    Shahee, Aga, E-mail: agashahee@gmail.com [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452001 (India); Department of Physics, IIT Bombay, Powai, Mumbai 400076 (India); Sharma, Shivani; Singh, K.; Lalla, N.P. [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452001 (India)

    2017-07-15

    Highlights: • Temperature and magnetic field driven coupled magneto-structural phase transition in Nd{sub 0.49}Sr{sub 0.51}MnO{sub 3+δ}. • Microscopic evidence of strong spin-charge-lattice coupling. • Iso-thermal magnetic field driven structure phase transition. • Field-driven structural phase transition origin of observed 1st order type CMR effect. - Abstract: Comprehensive X-ray diffraction (XRD) studies have been performed at different temperature (T) (4.2–300 K) and magnetic field (H) (0–8 T) to understand the evolution of crystal structure of Nd{sub 0.49}Sr{sub 0.51}MnO{sub 3+δ} (NSMO) under non ambient conditions. The T dependent XRD results show the abrupt change in the lattice parameters without any change in lattice symmetry at ∼200 K, which is associated with the first order structural phase transition from ferromagnetic to antiferromagnetic phase. This phase transition is strongly H dependent and shifted to lower temperature (∼150 K) on the application of 8 T field with phase coexistence (high temperature phase ∼18%), even down to 4.2 K. Isothermal XRD results at 150 K under different H clearly illustrate the H induced first order structural phase transition. The critical H at which this phase transformation starts is ∼1 T, with rapid growth above 4 T with hysteretic nature during increasing and decreasing H. These results are supported with the resistivity and magnetoresistance results and affirm the strong spin-lattice coupling in NSMO. Our detail studies reveal the structural correlations to the observed colossal magnetoresistance and magnetocaloric effect in this material.

  7. Symmetry structure and phase transitions

    Indian Academy of Sciences (India)

    2 µ2(σ2 +π2) + 1. 4λ(σ2 +π2)2. (2). For µ2. 0 chiral symmetry is spontaneously broken. Theσ field can be used to represent the quark condensate, the order parameter for chiral phase transition and the pions are the. Goldstone bosons. At the tree level the sigma, pion and the quark masses are given by m2 σ =3λσ2 cl µ2; m2.

  8. Ge(001)-(<2 1>, <0 3>)-Pb(<2 1>, <0 6>)↔Pb: Low-temperature two-dimensional phase transition

    DEFF Research Database (Denmark)

    Bunk, Oliver; Nielsen, Martin Meedom; Zeysing, J.H.

    2001-01-01

    configuration. Both the room-temperature and low-temperature phases of this system were investigated by surface x-ray diffraction using synchrotron radiation. The room-temperature Ge(001)-((2 1)(0 3)) phase is best described by a model with dynamically flipping germanium dimers underneath a distorted Pb(111...

  9. Topological Phase Transitions in Multicomponent Superconductors

    Science.gov (United States)

    Wang, Yuxuan; Fu, Liang

    2017-11-01

    We study the phase transition between a trivial and a time-reversal-invariant topological superconductor in a single-band system. By analyzing the interplay of symmetry, topology, and energetics, we show that for a generic normal state band structure, the phase transition occurs via extended intermediate phases in which even- and odd-parity pairing components coexist. For inversion-symmetric systems, the coexistence phase spontaneously breaks time-reversal symmetry. For noncentrosymmetric superconductors, the low-temperature intermediate phase is time-reversal breaking, while the high-temperature phase preserves time-reversal symmetry and has topologically protected line nodes. Furthermore, with approximate rotational invariance, the system has an emergent U (1 )×U (1 ) symmetry, and novel topological defects, such as half vortex lines binding Majorana fermions, can exist. We analytically solve for the dispersion of the Majorana fermion and show that it exhibits small and large velocities at low and high energies. Relevance of our theory to superconducting pyrochlore oxide Cd2 Re2 O7 and half-Heusler materials is discussed.

  10. Holography and the Electroweak Phase Transition

    CERN Document Server

    Creminelli, Paolo; Rattazzi, Riccardo; Creminelli, Paolo; Nicolis, Alberto; Rattazzi, Riccardo

    2002-01-01

    We study through holography the compact Randall-Sundrum (RS) model at finite temperature. In the presence of radius stabilization, the system is described at low enough temperature by the RS solution. At high temperature it is described by the AdS-Schwarzshild solution with an event horizon replacing the TeV brane. We calculate the transition temperature T_c between the two phases and we find it to be somewhat smaller than the TeV scale. Assuming that the Universe starts out at T >> T_c and cools down by expansion, we study the rate of the transition to the RS phase. We find that the transition is too slow and the Universe ends up in an old inflation scenario unless tight bounds are satisfied by the model parameters. In particular we find that the AdS curvature must be comparable to the 5D Planck mass and that the radius stabilization mechanism must lead to a sizeable distortion of the basic RS metric.

  11. Magnetic-field-induced orientational phase structure transition.

    Science.gov (United States)

    Dou, Yingying; Dong, Shuli; Hao, Jingcheng

    2014-02-11

    Magnetic field effect on the phase transition at high temperature (from 50 °C) inside the magnetic field has been found in C14G2 (N-tetradecyllactobionamide)/C12EO4 (tetraethylene glycol monododecyl ether)/D2O system. The phase was transited quickly from lamellar phase to isotropic phases [bottom, micellar phase (L1 phase) and top, sponge phase (L3 phase)] induced by a magnetic field, which was demonstrated by (2)H NMR and FF-TEM measurements. The isotropic phases induced by magnetic field were not stable, and the upper L3 phase can recover to lamellar phase after being restored in a 55 °C thermostat outside the magnetic field for about one month. During the mechanism study, the C12EO4 molecule was proved to be the dominant component for the phase transition induced by the magnetic field, while the C14G2 molecule was the auxiliary and just affected the transition speed. The breaking and rebuilding of hydrogen bonds could play an important role in the phase transition and recovering. Moreover, the surfactant concentration had an effect on the speed of phase transiting and phase recovering. These observations could provide an understanding of the phase transition and also the applications for the controlled drug delivery system of bilayer membranes driving, induced by the magnetic field.

  12. Phase transitions of fluids in heterogeneous pores

    Directory of Open Access Journals (Sweden)

    A. Malijevský

    2016-03-01

    Full Text Available We study phase behaviour of a model fluid confined between two unlike parallel walls in the presence of long range (dispersion forces. Predictions obtained from macroscopic (geometric and mesoscopic arguments are compared with numerical solutions of a non-local density functional theory. Two capillary models are considered. For a capillary comprising two (differently adsorbing walls we show that simple geometric arguments lead to the generalized Kelvin equation locating very accurately capillary condensation, provided both walls are only partially wet. If at least one of the walls is in complete wetting regime, the Kelvin equation should be modified by capturing the effect of thick wetting films by including Derjaguin's correction. Within the second model, we consider a capillary formed of two competing walls, so that one tends to be wet and the other dry. In this case, an interface localized-delocalized transition occurs at bulk two-phase coexistence and a temperature T*(L depending on the pore width L. A mean-field analysis shows that for walls exhibiting first-order wetting transition at a temperature T_{w}, T_{s} > T*(L > T_{w}, where the spinodal temperature Ts can be associated with the prewetting critical temperature, which also determines a critical pore width below which the interface localized-delocalized transition does not occur. If the walls exhibit critical wetting, the transition is shifted below Tw and for a model with the binding potential W(l=A(Tl-2+B(Tl-3+..., where l is the location of the liquid-gas interface, the transition can be characterized by a dimensionless parameter κ=B/(AL, so that the fluid configuration with delocalized interface is stable in the interval between κ=-2/3 and κ ~ -0.23.

  13. Low-temperature phase transition in γ-glycine single crystal. Pyroelectric, piezoelectric, dielectric and elastic properties

    Energy Technology Data Exchange (ETDEWEB)

    Tylczyński, Zbigniew, E-mail: zbigtyl@amu.edu.pl [Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Busz, Piotr [Institute of Molecular Physics, Polish Academy of Science, Smoluchowskiego 17, 60-179 Poznań (Poland)

    2016-11-01

    Temperature changes in the pyroelectric, piezoelectric, elastic and dielectric properties of γ-glycine crystals were studied in the range 100 ÷ 385 K. The pyroelectric coefficient increases monotonically in this temperature range and its value at RT was compared with that of other crystals having glycine molecules. A big maximum in the d14 component of piezoelectric tensor compared by maximum in attenuation of the resonant face-shear mode were observed at 189 K. The components of the elastic stiffness tensor and other components of the piezoelectric tensor show anomalies at this temperature. The components of electromechanical coupling coefficient determined indicate that γ-glycine is a weak piezoelectric. The real and imaginary part of the dielectric constant measured in the direction perpendicular to the trigonal axis show the relaxation anomalies much before 198 K and the activation energies were calculated. These anomalies were interpreted as a result of changes in the NH{sub 3}{sup +} vibrations through electron-phonon coupling of the so called “dynamical transition”. The anomalies of dielectric constant ε*{sub 11} and piezoelectric tensor component d{sub 14} taking place at 335 K are associated with an increase in ac conductivity caused by charge transfer of protons. - Graphical abstract: Imaginary part of dielectric constant in [100] direction. - Highlights: • Piezoelectric, elastic and dielectric constants anomalies were discovered at 189 K. • These anomalies were interpreted as a result of so called “dynamical transition”. • Relaxational dielectric anomaly was explained by the dynamics of glycine molecules. • Pyroelectric coefficient of γ-glycine was determined in a wide temperature range. • Complex dielectric & piezoelectric anomalies at 335 K were caused by protons hopping.

  14. High temperature phase equilibria and phase diagrams

    CERN Document Server

    Kuo, Chu-Kun; Yan, Dong-Sheng

    2013-01-01

    High temperature phase equilibria studies play an increasingly important role in materials science and engineering. It is especially significant in the research into the properties of the material and the ways in which they can be improved. This is achieved by observing equilibrium and by examining the phase relationships at high temperature. The study of high temperature phase diagrams of nonmetallic systems began in the early 1900s when silica and mineral systems containing silica were focussed upon. Since then technical ceramics emerged and more emphasis has been placed on high temperature

  15. Generalized phase transitions in Lovelock gravity

    Science.gov (United States)

    Camanho, Xián O.; Edelstein, José D.; Giribet, Gastón; Gomberoff, Andrés

    2014-09-01

    We investigate a novel mechanism for phase transitions that is a distinctive feature of higher-curvature gravity theories. For definiteness, we bound ourselves to the case of Lovelock gravities. These theories are known to have several branches of asymptotically anti-de Sitter solutions. Here, extending our previous work, we show that phase transitions among some of these branches are driven by a thermalon configuration: a bubble separating two regions of different effective cosmological constants, generically hosting a black hole in the interior. Above some critical temperature, this thermalon configuration is preferred with respect to the finite-temperature anti-de Sitter space, triggering a sophisticated version of the Hawking-Page transition. After being created, the unstable bubble configuration can in general dynamically change the asymptotic cosmological constant. While this phenomenon already occurs in the case of a gravity action with square curvature terms, we point out that in the case of Lovelock theory with cubic (and higher) terms new effects appear. For instance, the theory may admit more than one type of bubble and branches that are in principle free of pathologies may also decay through the thermalon mechanism. We also find ranges of the gravitational couplings for which the theory becomes sick. These add up to previously found restrictions to impose tighter constraints on higher-curvature gravities. The results of this paper point to an intricate phase diagram which might accommodate similarly rich behavior in the dual conformal field theory side.

  16. Light scattering near phase transitions

    CERN Document Server

    Cummins, HZ

    1983-01-01

    Since the development of the laser in the early 1960's, light scattering has played an increasingly crucial role in the investigation of many types of phase transitions and the published work in this field is now widely dispersed in a large number of books and journals.A comprehensive overview of contemporary theoretical and experimental research in this field is presented here. The reviews are written by authors who have actively contributed to the developments that have taken place in both Eastern and Western countries.

  17. Phase transitions and critical phenomena

    CERN Document Server

    Domb, Cyril

    2000-01-01

    The field of phase transitions and critical phenomena continues to be active in research, producing a steady stream of interesting and fruitful results. No longer an area of specialist interest, it has acquired a central focus in condensed matter studies. The major aim of this serial is to provide review articles that can serve as standard references for research workers in the field, and for graduate students and others wishing to obtain reliable information on important recent developments.The two review articles in this volume complement each other in a remarkable way. Both deal with what m

  18. Gibbs measures and phase transitions

    CERN Document Server

    Georgii, Hans-Otto

    2011-01-01

    From a review of the first edition: ""This book […] covers in depth a broad range of topics in the mathematical theory of phase transition in statistical mechanics. […] It is in fact one of the author's stated aims that this comprehensive monograph should serve both as an introductory text and as a reference for the expert."" (F. Papangelou, Zentralblatt MATH) The second edition has been extended by a new section on large deviations and some comments on the more recent developments in the area.

  19. Brain Performance versus Phase Transitions.

    Science.gov (United States)

    Torres, Joaquín J; Marro, J

    2015-07-20

    We here illustrate how a well-founded study of the brain may originate in assuming analogies with phase-transition phenomena. Analyzing to what extent a weak signal endures in noisy environments, we identify the underlying mechanisms, and it results a description of how the excitability associated to (non-equilibrium) phase changes and criticality optimizes the processing of the signal. Our setting is a network of integrate-and-fire nodes in which connections are heterogeneous with rapid time-varying intensities mimicking fatigue and potentiation. Emergence then becomes quite robust against wiring topology modification--in fact, we considered from a fully connected network to the Homo sapiens connectome--showing the essential role of synaptic flickering on computations. We also suggest how to experimentally disclose significant changes during actual brain operation.

  20. High-temperature phase transitions and domain structures of KLiSO{sub 4}. Studied by polarisation-optics, X-ray topography and liquid-crystal surface decoration

    Energy Technology Data Exchange (ETDEWEB)

    Scherf, Christian; Chung, Su Jin; Hahn, Theo; Klapper, Helmut [RWTH Aachen Univ. (Germany). Inst. fuer Kristallographie; Ivanov, Nicolay R. [Russian Academy of Sciences, Moscow (Russian Federation). Shubnikov Inst. of Crystallography

    2017-07-01

    The transitions between the room temperature phase III (space group P6{sub 3}) and the two high-temperature phases II (Pcmn) and I (P6{sub 3}/mmc) of KLiSO{sub 4} and the domain structures generated by them were investigated by high-temperature polarisation optics (birefringence) and room-temperature X-ray topography, optical activity and nematic-liquid-crystal (NLC) surface decoration. The transition from the polar hexagonal phase III into the centrosymmetric orthorhombic phase II at 708 K leads, due to the loss of the trigonal axis and the radial temperature gradient of the optical heating chamber used, to a roughly hexagonal arrangement of three sets of thin orthorhombic {110} lamelleae with angles of 60 (120 ) between them. The associated twin law ''reflection m{110}{sub orth}'' corresponds to the frequent growth twin m{10 anti 10}{sub hex} of phase III. The domains are easily ferroelastically switched. Upon further heating above 949 K into phase I (P6{sub 3}/mmc) all domains vanish. Upon cooling back into phase II the three domain states related by 60 (120 ) reflections m{110}{sub orth} re-appear, however (due to the higher thermal agitation at 949 K) with a completely different domain structure consisting of many small, irregularly arranged {110}{sub orth} domains. Particular attention is paid to the domain structure of the hexagonal room temperature phase III generated during the re-transition from the orthorhombic phase II. Curiously, from the expected three twin laws inversion anti 1, rotation 2 perpendicular to [001]{sub hex} and reflection m{10 anti 10}{sub hex} only the latter, which corresponds to the frequent growth twinning, has been found. Finally a short treatise of the structural relations of the KLiSO{sub 4} high-temperature polymorphs is given.

  1. Thermodynamic phase transition of a black hole in rainbow gravity

    Science.gov (United States)

    Feng, Zhong-Wen; Yang, Shu-Zheng

    2017-09-01

    In this letter, using the rainbow functions that were proposed by Magueijo and Smolin, we investigate the thermodynamics and the phase transition of rainbow Schwarzschild black hole. First, we calculate the rainbow gravity corrected Hawking temperature. From this modification, we then derive the local temperature, free energy, and other thermodynamic quantities in an isothermal cavity. Finally, we analyze the critical behavior, thermodynamic stability, and phase transition of the rainbow Schwarzschild black hole. The results show that the rainbow gravity can stop the Hawking radiation in the final stages of black holes' evolution and lead to the remnants of black holes. Furthermore, one can observe that the rainbow Schwarzschild black hole has one first-order phase transition, two second-order phase transitions, and three Hawking-Page-type phase transitions in the framework of rainbow gravity theory.

  2. Thermodynamic phase transition of a black hole in rainbow gravity

    Directory of Open Access Journals (Sweden)

    Zhong-Wen Feng

    2017-09-01

    Full Text Available In this letter, using the rainbow functions that were proposed by Magueijo and Smolin, we investigate the thermodynamics and the phase transition of rainbow Schwarzschild black hole. First, we calculate the rainbow gravity corrected Hawking temperature. From this modification, we then derive the local temperature, free energy, and other thermodynamic quantities in an isothermal cavity. Finally, we analyze the critical behavior, thermodynamic stability, and phase transition of the rainbow Schwarzschild black hole. The results show that the rainbow gravity can stop the Hawking radiation in the final stages of black holes' evolution and lead to the remnants of black holes. Furthermore, one can observe that the rainbow Schwarzschild black hole has one first-order phase transition, two second-order phase transitions, and three Hawking–Page-type phase transitions in the framework of rainbow gravity theory.

  3. Phase transitions in the coal-water-methane system

    Directory of Open Access Journals (Sweden)

    A.D.Alexeev

    2006-01-01

    Full Text Available Low temperature phase transitions in water and methane occurring in fossil coals were studied experimentally using Nuclear Magnetic Resonance (NMR techniques. Contributions of constituent fluids into narrow line of 1H NMR wide line spectrum were analyzed.

  4. Exploring the new phase transition of CDT

    OpenAIRE

    Coumbe, D. N.; Gizbert-Studnicki, J.; Jurkiewicz, J.

    2015-01-01

    This work focuses on the newly discovered bifurcation phase transition of CDT quantum gravity. We define various order parameters and investigate which is most suitable to study this transition in numerical simulations. By analyzing the behaviour of the order parameters we present evidence that the transition separating the bifurcation phase and the physical phase of CDT is likely a second or higher-order transition, a result that may have important implications for the continuum limit of CDT.

  5. Exploring the new phase transition of CDT

    Energy Technology Data Exchange (ETDEWEB)

    Coumbe, D.N. [The Niels Bohr Institute, Copenhagen University,Blegdamsvej 17, DK-2100 Copenhagen (Denmark); Gizbert-Studnicki, J.; Jurkiewicz, J. [Faculty of Physics, Astronomy and Applied Computer Science, Jagiellonian University,ul. prof. Stanislawa Lojasiewicza 11, Krakow, PL 30-348 (Poland)

    2016-02-22

    This work focuses on the newly discovered bifurcation phase transition of CDT quantum gravity. We define various order parameters and investigate which is most suitable to study this transition in numerical simulations. By analyzing the behaviour of the order parameters we present evidence that the transition separating the bifurcation phase and the physical phase of CDT is likely a second or higher-order transition, a result that may have important implications for the continuum limit of CDT.

  6. Structural phase transitions in niobium oxide nanocrystals

    Science.gov (United States)

    Yuvakkumar, R.; Hong, Sun Ig

    2015-09-01

    Niobium oxide nanocrystals were successfully synthesized employing the green synthesis method. Phase formation, microstructure and compositional properties of 1, 4 and 7 days incubation treated samples after calcinations at 450 °C were examined using X-ray diffraction, Raman, photoluminescence (PL), infrared, X-ray photoelectron spectra and transmission electron microscopic characterizations. It was observed that phase formation of Nb2O5 nanocrystals was dependent upon the incubation period required to form stable metal oxides. The characteristic results clearly revealed that with increasing incubation and aging, the transformation of cubic, orthorhombic and monoclinic phases were observed. The uniform heating at room temperature (32 °C) and the ligation of niobium atoms due to higher phenolic constituents of utilized rambutan during aging processing plays a vital role in structural phase transitions in niobium oxide nanocrystals. The defects over a period of incubation and the intensities of the PL spectra changing over a period of aging were related to the amount of the defects induced by the phase transition.

  7. Effect of temperature-driven phase transition on energy-storage and -release properties of Pb0.97La0.02[Zr0.55Sn0.30Ti0.15]O3 ceramics

    Science.gov (United States)

    Xu, Ran; Tian, Jingjing; Zhu, Qingshan; Feng, Yujun; Wei, Xiaoyong; Xu, Zhuo

    2017-07-01

    Temperature-driven phase transition of Pb0.97La0.02[Zr0.55Sn0.30Ti0.15]O3 ceramics was studied, and the consecutive ferroelectric-antiferroelectric-paraelectric (FE-AFE-PE) switching was confirmed. The materials have better dielectric tunability (-82% to 50%) in the AFE state than in the FE state. Also, the phase transition influences the energy-storage and -release performance significantly. A sharp increase in releasable energy density and efficiency was observed due to the temperature-driven FE-AFE transition. Highest releasable energy density, current density, and peak power density were achieved at 130 °C, which was attributed to the highest backward transition field. The stored charge was released completely in AFE and PE states in the microseconds scale, while only a small part of it was released in the FE state. The above results indicate the huge impact of temperature-driven phase transition on dielectrics' performance, which is significant when developing AFE materials working in a wide temperature range.

  8. QCD Phase Transitions, Volume 15

    Energy Technology Data Exchange (ETDEWEB)

    Schaefer, T.; Shuryak, E.

    1999-03-20

    The title of the workshop, ''The QCD Phase Transitions'', in fact happened to be too narrow for its real contents. It would be more accurate to say that it was devoted to different phases of QCD and QCD-related gauge theories, with strong emphasis on discussion of the underlying non-perturbative mechanisms which manifest themselves as all those phases. Before we go to specifics, let us emphasize one important aspect of the present status of non-perturbative Quantum Field Theory in general. It remains true that its studies do not get attention proportional to the intellectual challenge they deserve, and that the theorists working on it remain very fragmented. The efforts to create Theory of Everything including Quantum Gravity have attracted the lion share of attention and young talent. Nevertheless, in the last few years there was also a tremendous progress and even some shift of attention toward emphasis on the unity of non-perturbative phenomena. For example, we have seen some efforts to connect the lessons from recent progress in Supersymmetric theories with that in QCD, as derived from phenomenology and lattice. Another example is Maldacena conjecture and related development, which connect three things together, string theory, super-gravity and the (N=4) supersymmetric gauge theory. Although the progress mentioned is remarkable by itself, if we would listen to each other more we may have chance to strengthen the field and reach better understanding of the spectacular non-perturbative physics.

  9. Low temperature vibrational spectra, lattice dynamics, and phase transitions in some potassium hexahalometallates: K2[XY6] with X=Sn or Te and Y=Cl or Br

    DEFF Research Database (Denmark)

    Chodos, Steven L.; Berg, Rolf W.

    1979-01-01

    This paper deals with the observation and identification of phonon frequencies resulting from the low temperature phase transitions in K2XY6 crystals. By means of a simple lattice dynamical model, the vibrational Raman and IR data available in the literature and obtained here have been analyzed. ...

  10. Data set: 31 years of spatially distributed air temperature, humidity, precipitation amount and precipitation phase from a mountain catchment in the rain-snow transition zone

    Science.gov (United States)

    Thirty one years of spatially distributed air temperature, relative humidity, dew point temperature, precipitation amount, and precipitation phase data are presented for the Reynolds Creek Experimental Watershed. The data are spatially distributed over a 10m Lidar-derived digital elevation model at ...

  11. Study of the pressure-time-temperature transformation of amorphous La6Ni5Al89 by the energy dispersive method for phase transition

    DEFF Research Database (Denmark)

    Paci, B.; Rossi-Albertini, V.; Sikorski, M.

    2005-01-01

    was measured and the curves describing the transitions, qualitatively equivalent to a differential scanning calorimetry (DSC) thermogram, could be drawn. Finally, the analysis of such curves allowed calculation of some points of the alloy pressure-time-temperature transformation (PTTT) diagram. More...

  12. Phase transition in L-alaninium oxalate by photoacoustics

    Indian Academy of Sciences (India)

    Phase transition in L-alaninium oxalate is studied by using TG, DTA and photoacoustic spectroscopy. A sharp transition at 378 K by photoacoustics is observed whereas at the same temperature the endothermic energy change observed by TG and DTA is not very sharp. This is discussed in detail with reference to the other ...

  13. Nuclear Binding Near a Quantum Phase Transition.

    Science.gov (United States)

    Elhatisari, Serdar; Li, Ning; Rokash, Alexander; Alarcón, Jose Manuel; Du, Dechuan; Klein, Nico; Lu, Bing-Nan; Meißner, Ulf-G; Epelbaum, Evgeny; Krebs, Hermann; Lähde, Timo A; Lee, Dean; Rupak, Gautam

    2016-09-23

    How do protons and neutrons bind to form nuclei? This is the central question of ab initio nuclear structure theory. While the answer may seem as simple as the fact that nuclear forces are attractive, the full story is more complex and interesting. In this work we present numerical evidence from ab initio lattice simulations showing that nature is near a quantum phase transition, a zero-temperature transition driven by quantum fluctuations. Using lattice effective field theory, we perform Monte Carlo simulations for systems with up to twenty nucleons. For even and equal numbers of protons and neutrons, we discover a first-order transition at zero temperature from a Bose-condensed gas of alpha particles (^{4}He nuclei) to a nuclear liquid. Whether one has an alpha-particle gas or nuclear liquid is determined by the strength of the alpha-alpha interactions, and we show that the alpha-alpha interactions depend on the strength and locality of the nucleon-nucleon interactions. This insight should be useful in improving calculations of nuclear structure and important astrophysical reactions involving alpha capture on nuclei. Our findings also provide a tool to probe the structure of alpha cluster states such as the Hoyle state responsible for the production of carbon in red giant stars and point to a connection between nuclear states and the universal physics of bosons at large scattering length.

  14. Antiferromagnetic phase transition and spin correlations in NiO

    DEFF Research Database (Denmark)

    Chatterji, Tapan; McIntyre, G.J.; Lindgård, Per-Anker

    2009-01-01

    We have investigated the antiferromagnetic (AF) phase transition and spin correlations in NiO by high-temperature neutron diffraction below and above TN. We show that AF phase transition is a continuous second-order transition within our experimental resolution. The spin correlations manifested...... by the strong diffuse magnetic scattering persist well above TN530 K and could still be observed at T=800 K which is about 1.5TN. We argue that the strong spin correlations above TN are due to the topological frustration of the spins on a fcc lattice. The Néel temperature is substantially reduced...

  15. Mixed state dynamical quantum phase transitions

    Science.gov (United States)

    Bhattacharya, Utso; Bandyopadhyay, Souvik; Dutta, Amit

    2017-11-01

    Preparing an integrable system in a mixed state described by a thermal density matrix, we subject it to a sudden quench and explore the subsequent unitary dynamics. To address the question of whether the nonanalyticities, namely, the dynamical quantum phase transitions (DQPTs), persist when the initial state is mixed, we consider two versions of the generalized Loschmidt overlap amplitude (GLOA). Our study shows that the GLOA constructed using the Uhlmann approach does not show any signature of DQPTs at any nonzero initial temperature. On the other hand, a GLOA defined in the interferometric phase approach through the purifications of the time-evolved density matrix, indeed shows that nonanalyiticies in the corresponding "dynamical free-energy density" persist, thereby establishing the existence of mixed state dynamical quantum phase transitions (MSDQPTs). Our work provides a framework that perfectly reproduces both the nonanalyticities and also the emergent topological structure in the pure state limit. These claims are corroborated by analyzing the nonequilibrium dynamics of a transverse Ising chain initially prepared in a thermal state and subjected to a sudden quench of the transverse field.

  16. Phase transitions in Ising Chains?

    Science.gov (United States)

    Mancini, Ferdinando

    2009-12-01

    An open question in the study of the spin-1/2 Ising model is the solution of the two-dimensional case in the presence of a magnetic field. A possible answer is based on the study of L-coupled linear chains in the limit of large L. Results reported in the literature show that a dimensional crossover from the one to the two dimensional model does not exist. However, what happens if one considers open boundary conditions (BC)? In this article I show that, for an appropriate choice of the BC, a system of L-chains exhibits a ferromagnetic order characterized by a critical temperature which, for zero magnetic field, tends to the Onsager's one as L increases. It is then possible to study the phase diagram in the (h, T) plane and obtain a solution for finite magnetic field.

  17. Phase transitions in semidefinite relaxations.

    Science.gov (United States)

    Javanmard, Adel; Montanari, Andrea; Ricci-Tersenghi, Federico

    2016-04-19

    Statistical inference problems arising within signal processing, data mining, and machine learning naturally give rise to hard combinatorial optimization problems. These problems become intractable when the dimensionality of the data is large, as is often the case for modern datasets. A popular idea is to construct convex relaxations of these combinatorial problems, which can be solved efficiently for large-scale datasets. Semidefinite programming (SDP) relaxations are among the most powerful methods in this family and are surprisingly well suited for a broad range of problems where data take the form of matrices or graphs. It has been observed several times that when the statistical noise is small enough, SDP relaxations correctly detect the underlying combinatorial structures. In this paper we develop asymptotic predictions for several detection thresholds, as well as for the estimation error above these thresholds. We study some classical SDP relaxations for statistical problems motivated by graph synchronization and community detection in networks. We map these optimization problems to statistical mechanics models with vector spins and use nonrigorous techniques from statistical mechanics to characterize the corresponding phase transitions. Our results clarify the effectiveness of SDP relaxations in solving high-dimensional statistical problems.

  18. Phase transition in a modified square Josephson-junction array

    CERN Document Server

    Han, J

    1999-01-01

    We study the phase transition in a modified square proximity-coupled Josephson-junction array with small superconducting islands at the center of each plaquette. We find that the modified square array undergoes a Kosterlitz-Thouless-Berezinskii-like phase transition, but at a lower temperature than the simple square array with the same single-junction critical current. The IV characteristics, as well as the phase transition, resemble qualitatively those of a disordered simple square array. The effects of the presence of the center islands in the modified square array are discussed.

  19. The electroweak phase transition in the Inert Doublet Model

    Energy Technology Data Exchange (ETDEWEB)

    Blinov, Nikita [Department of Physics, University of California Santa Cruz,1156 High St, Santa Cruz, CA 95064 (United States); Santa Cruz Institute for Particle Physics,1156 High St, Santa Cruz, CA 95064 (United States); Theory Department, TRIUMF,4004 Wesbrook Mall, Vancouver, BC V6T 2A3 (Canada); Department of Physics and Astronomy, University of British Columbia,Vancouver, BC V6T 1Z1 (Canada); Profumo, Stefano; Stefaniak, Tim [Department of Physics, University of California Santa Cruz,1156 High St, Santa Cruz, CA 95064 (United States); Santa Cruz Institute for Particle Physics,1156 High St, Santa Cruz, CA 95064 (United States)

    2015-07-21

    We study the strength of a first-order electroweak phase transition in the Inert Doublet Model (IDM), where particle dark matter (DM) is comprised of the lightest neutral inert Higgs boson. We improve over previous studies in the description and treatment of the finite-temperature effective potential and of the electroweak phase transition. We focus on a set of benchmark models inspired by the key mechanisms in the IDM leading to a viable dark matter particle candidate, and illustrate how to enhance the strength of the electroweak phase transition by adjusting the masses of the yet undiscovered IDM Higgs states. We argue that across a variety of DM masses, obtaining a strong enough first-order phase transition is a generic possibility in the IDM. We find that due to direct dark matter searches and collider constraints, a sufficiently strong transition and a thermal relic density matching the universal DM abundance is possible only in the Higgs funnel regime.

  20. The electroweak phase transition in the Inert Doublet Model

    Energy Technology Data Exchange (ETDEWEB)

    Blinov, Nikita; Profumo, Stefano; Stefaniak, Tim, E-mail: nblinov@triumf.ca, E-mail: profumo@ucsc.edu, E-mail: tistefan@ucsc.edu [Department of Physics, University of California Santa Cruz, 1156 High St, Santa Cruz, CA 95064 (United States)

    2015-07-01

    We study the strength of a first-order electroweak phase transition in the Inert Doublet Model (IDM), where particle dark matter (DM) is comprised of the lightest neutral inert Higgs boson. We improve over previous studies in the description and treatment of the finite-temperature effective potential and of the electroweak phase transition. We focus on a set of benchmark models inspired by the key mechanisms in the IDM leading to a viable dark matter particle candidate, and illustrate how to enhance the strength of the electroweak phase transition by adjusting the masses of the yet undiscovered IDM Higgs states. We argue that across a variety of DM masses, obtaining a strong enough first-order phase transition is a generic possibility in the IDM. We find that due to direct dark matter searches and collider constraints, a sufficiently strong transition and a thermal relic density matching the universal DM abundance is possible only in the Higgs funnel regime.

  1. Temperature-induced reversible first-order single crystal to single crystal phase transition in Boc-γ(4)(R)Val-Val-OH: interplay of enthalpy and entropy.

    Science.gov (United States)

    Pal, Rumpa; Reddy, M B Madhusudana; Dinesh, Bhimareddy; Balaram, Padmanabhan; Guru Row, Tayur N

    2014-10-09

    Crystals of Boc-γ(4)(R)Val-Val-OH undergo a reversible first-order single crystal to single crystal phase transition at Tc ≈ 205 K from the orthorhombic space group P22121 (Z' = 1) to the monoclinic space group P21 (Z' = 2) with a hysteresis of ∼2.1 K. The low-temperature monoclinic form is best described as a nonmerohedral twin with ∼50% contributions from its two components. The thermal behavior of the dipeptide crystals was characterized by differential scanning calorimetry experiments. Visual changes in birefringence of the sample during heating and cooling cycles on a hot-stage microscope with polarized light supported the phase transition. Variable-temperature unit cell check measurements from 300 to 100 K showed discontinuity in the volume and cell parameters near the transition temperature, supporting the first-order behavior. A detailed comparison of the room-temperature orthorhombic form with the low-temperature (100 K) monoclinic form revealed that the strong hydrogen-bonding motif is retained in both crystal systems, whereas the non-covalent interactions involving side chains of the dipeptide differ significantly, leading to a small change in molecular conformation in the monoclinic form as well as a small reorientation of the molecules along the ac plane. A rigid-body thermal motion analysis (translation, libration, screw; correlation of translation and libration) was performed to study the crystal entropy. The reversible nature of the phase transition is probably the result of an interplay between enthalpy and entropy: the low-temperature monoclinic form is enthalpically favored, whereas the room-temperature orthorhombic form is entropically favored.

  2. Low-temperature phase transition in glycine-glutaric acid co-crystals studied by single-crystal X-ray diffraction, Raman spectroscopy and differential scanning calorimetry.

    Science.gov (United States)

    Zakharov, Boris A; Losev, Evgeniy A; Kolesov, Boris A; Drebushchak, Valeri A; Boldyreva, Elena V

    2012-06-01

    The occurrence of a first-order reversible phase transition in glycine-glutaric acid co-crystals at 220-230 K has been confirmed by three different techniques - single-crystal X-ray diffraction, polarized Raman spectroscopy and differential scanning calorimetry. The most interesting feature of this phase transition is that every second glutaric acid molecule changes its conformation, and this fact results in the space-group symmetry change from P2(1)/c to P1. The topology of the hydrogen-bonded motifs remains almost the same and hydrogen bonds do not switch to other atoms, although the hydrogen bond lengths do change and some of the bonds become inequivalent.

  3. Phases and phase transitions of S=1 bosons

    Indian Academy of Sciences (India)

    smukerjee

    Quantum phases and phase transitions of bosons. Subroto Mukerjee. Dept. of Physics & Centre for Quantum. Information and Quantum Computing (CQIQC). Indian Institute of Science, Bangalore. 77th annual meeting of the IAS, Nov. 20 2011, PRL Ahmedabad ...

  4. The Landau theory of phase transitions

    Indian Academy of Sciences (India)

    mechanical theory of diamagnetism, the theory of sec- ond order phase transitions, the mean-field theory of superconductivity, the explanation of Landau damping in plasma physics, the Landau pole in quantum electro-. Keywords. Phase transition, Landau theory, symmetry breaking, bead-on-a- ring, critical angular velocity ...

  5. Transition temperature of martensitic transformations in hafnia and zirconia

    Science.gov (United States)

    Luo, Xuhui; Demkov, A. A.

    2008-03-01

    Transition metal oxides find applications in ceramics, catalysis and semiconductor technology. In particular, hafnium dioxide or hafnia will succeed silica as a gate dielectric in advanced transistors. However, thermodynamic properties of thin hafnia films are not well understood, despite their technological importance. We use density functional theory to investigate the tetragonal to monoclinic phase transition in hafnia and zirconia. We find that unlike the case of the cubic to tetragonal transition, this phase transition is not driven by a soft mode. We use transition state theory to identify the minimum energy path (MEP) employing first principle calculations for hafnia and zirconia, sow that both transformations are martensitic, and obtain the transition barriers. Martensitic transformations include both the internal coordinate transformation and deformation of the cell lattice vectors (``strain and shuffle''), therefore the potential energy surface and MEP are function not only of the internal atomic coordinates but also of the unit cell lattice vectors. Considering the simplest case of uniform strain the transition temperatures we then relate the barrier height to the transition temperature. As a self-consistency check, assuming the equality of thermodynamics potentials of the tetragonal and monoclinic phases during the transition, and using the difference in the internal energy calculated from first principles we estimate the entropy change associated with the transition which is found in good agreement with that calculated form the phonon spectra.

  6. Supercooling across first-order phase transitions in vortex matter

    Indian Academy of Sciences (India)

    ... as depicted in figure 1. Vortex matter contracts on being heated from the ordered (solid) phase to the disordered (liquid) phase, similar to the behaviour of ice at pressures below 200 MPa [5]. Hysteresis has been reported, with both field and temperature as the control variable, across the vortex–lattice melting transition.

  7. Elastic properties and stress-temperature phase diagrams of high-temperature phases with low-temperature lattice instabilities

    Science.gov (United States)

    Thomas, John C.; Van der Ven, Anton

    2014-12-01

    The crystal structures of many technologically important high-temperature phases are predicted to have lattice instabilities at low temperature, making their thermodynamic and mechanical properties inaccessible to standard first principles approaches that rely on the (quasi) harmonic approximation. Here, we use the recently developed anharmonic potential cluster expansion within Monte Carlo simulations to predict the effect of temperature and anisotropic stress on the elastic properties of ZrH2, a material that undergoes diffusionless transitions among cubic, tetragonal, and orthorhombic phases. Our analysis shows that the mechanical properties of high-temperature phases with low-temperature vibrational instabilities are very sensitive to temperature and stress state. These findings have important implications for materials characterization and multi-scale simulations and suggest opportunities for enhanced strain engineering of high-temperature phases exhibiting soft-mode instabilities.

  8. Thermal Fluctuations in Electroweak Phase Transition

    Science.gov (United States)

    Shiromizu, T.; Morikawa, M.; Yokoyama, J.

    1995-11-01

    We estimate the amplitude of thermal fluctuations by calculating the typical size of subcritical bubbles in cosmological electroweak phase transition and show that this thermal fluctuation effect drastically changes dynamics of the phase transition from the ordinary first order type with supercooling. From this fact, we conclude that the standard electroweak baryogenesis scenario associated with such a first order transition does not work in the minimal standard model in certain conditions.

  9. First-Order Dynamical Phase Transitions

    Science.gov (United States)

    Canovi, Elena; Werner, Philipp; Eckstein, Martin

    2014-12-01

    Recently, dynamical phase transitions have been identified based on the nonanalytic behavior of the Loschmidt echo in the thermodynamic limit [Heyl et al., Phys. Rev. Lett. 110, 135704 (2013)]. By introducing conditional probability amplitudes, we show how dynamical phase transitions can be further classified, both mathematically, and potentially in experiment. This leads to the definition of first-order dynamical phase transitions. Furthermore, we develop a generalized Keldysh formalism which allows us to use nonequilibrium dynamical mean-field theory to study the Loschmidt echo and dynamical phase transitions in high-dimensional, nonintegrable models. We find dynamical phase transitions of first order in the Falicov-Kimball model and in the Hubbard model.

  10. Phase transition and PTCR effect in erbium doped BT ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Leyet, Y. [Departamento de Fisica, Facultad de Ciencias Naturales, Universidad de Oriente, C.P. 90500 Santiago de Cuba (Cuba); Instituto Federal de Educacao Ciencia e Tecnologia (IFAM), Av. 7 de Setembro 1975, Centro, Manaus 69020-120, AM (Brazil); Pena, R.; Zulueta, Y. [Departamento de Fisica, Facultad de Ciencias Naturales, Universidad de Oriente, C.P. 90500 Santiago de Cuba (Cuba); Guerrero, F. [Departamento de Fisica, Facultad de Ciencias Naturales, Universidad de Oriente, C.P. 90500 Santiago de Cuba (Cuba); CESI, Universidade do Estado do Amazonas, Ave Mario Andreaza, Amazonas (Brazil); Anglada-Rivera, J. [CESI, Universidade do Estado do Amazonas, Ave Mario Andreaza, Amazonas (Brazil); Romaguera, Y. [INESC TEC, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal); Perez de la Cruz, J., E-mail: jcruz@inescporto.pt [INESC TEC, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal)

    2012-06-25

    Highlights: Black-Right-Pointing-Pointer Erbium influence the dielectric response BaTiO{sub 3} ceramics. Black-Right-Pointing-Pointer Features of the phase transition are not explained by phenomenological models. Black-Right-Pointing-Pointer Relaxation parameters do not show influence on ferroelectric-paraelectric phase transition. Black-Right-Pointing-Pointer Dielectric anomaly on BET phase transition is associated with the PTCR effect. - Abstract: In this work the dielectric behaviour and main features of the phase transition of BaTiO{sub 3} and Ba{sub 0.99}Er{sub 0.01}TiO{sub 3} ceramics were carefully investigated. The temperature and frequency dependences of the dielectric properties of erbium doped BaTiO{sub 3} ceramics were measured in the 25-225 Degree-Sign C and 100 Hz to 10 MHz ranges, respectively. From this study, a dielectric anomaly in the ferroelectric-paraelectric phase transition of the Ba{sub 0.99}Er{sub 0.01}TiO{sub 3} ceramic was observed. The features of the samples phase transition were analysed by using Curie-Weiss, Santos-Eiras' and order parameter local phenomenological models. In the BaTiO{sub 3} system, all models showed a normal phase transition, while was not possible to establish the character of the phase transition in the Ba{sub 0.99}Er{sub 0.01}TiO{sub 3} system. The relaxation parameters of conductive processes for the study ferroelectric materials, analysed in the time domain, did not show any influence on the ferroelectric-paraelectric phase transition. Finally, it was demonstrated that the anomaly observed on the phase transition of the erbium doped BaTiO{sub 3} ceramics is associated with the processes that results in the PTCR effect.

  11. Quantum Phase Transitions: A Network Approach

    Science.gov (United States)

    Vargas, David L.; Larue, David M.; Carr, Lincoln D.

    2014-03-01

    Understanding the network structure of complex systems has opened up new avenues of research in sociology, biology, technology, and physics. In this talk we present evidence that complex network measures are able to identify the phases in two well known models. We distinguish the ferromagnetic and paramagnetic phases of the transverse Ising Hamiltonian. We also identify the Mott-insulator to superfluid transition of the Bose-Hubbard Hamiltonian. The network approach to the analysis of quantum phase transitions provides us with a new set of tools to explore the many body physics of quantum phase transitions. Supported by NSF and AFOSR.

  12. Non-equilibrium phase transitions in a liquid crystal.

    Science.gov (United States)

    Dan, K; Roy, M; Datta, A

    2015-09-07

    The present manuscript describes kinetic behaviour of the glass transition and non-equilibrium features of the "Nematic-Isotropic" (N-I) phase transition of a well known liquid crystalline material N-(4-methoxybenzylidene)-4-butylaniline from the effects of heating rate and initial temperature on the transitions, through differential scanning calorimetry (DSC), Fourier transform infrared and fluorescence spectroscopy. Around the vicinity of the glass transition temperature (Tg), while only a change in the baseline of the ΔCp vs T curve is observed for heating rate (β) > 5 K min(-1), consistent with a glass transition, a clear peak for β ≤ 5 K min(-1) and the rapid reduction in the ΔCp value from the former to the latter rate correspond to an order-disorder transition and a transition from ergodic to non-ergodic behaviour. The ln β vs 1000/T curve for the glass transition shows convex Arrhenius behaviour that can be explained very well by a purely entropic activation barrier [Dan et al., Eur. Phys. Lett. 108, 36007 (2014)]. Fourier transform infrared spectroscopy indicates sudden freezing of the out-of-plane distortion vibrations of the benzene rings around the glass transition temperature and a considerable red shift indicating enhanced coplanarity of the benzene rings and, consequently, enhancement in the molecular ordering compared to room temperature. We further provide a direct experimental evidence of the non-equilibrium nature of the N-I transition through the dependence of this transition temperature (TNI) and associated enthalpy change (ΔH) on the initial temperature (at fixed β-values) for the DSC scans. A plausible qualitative explanation based on Mesquita's extension of Landau-deGennes theory [O. N. de Mesquita, Braz. J. Phys. 28, 257 (1998)] has been put forward. The change in the molecular ordering from nematic to isotropic phase has been investigated through fluorescence anisotropy measurements where the order parameter, quantified by the

  13. Functional Implications of Intracellular Phase Transitions.

    Science.gov (United States)

    Holehouse, Alex S; Pappu, Rohit V

    2018-01-11

    Intracellular environments are heterogeneous milieus comprising of macromolecules, osmolytes, and a range of assemblies that include membrane-bound organelles and membraneless biomolecular condensates. The latter are non-stoichiometric assemblies of protein and RNA molecules. They represent distinct phases and form via intracellular phase transitions. Here, we present insights from recent studies and provide a perspective on how phase transitions that lead to biomolecular condensates might contribute to cellular functions.

  14. Fidelity analysis of topological quantum phase transitions

    Science.gov (United States)

    Abasto, Damian F.; Hamma, Alioscia; Zanardi, Paolo

    2008-07-01

    We apply the fidelity metric approach to analyze two recently introduced models that exhibit a quantum phase transition to a topologically ordered phase. These quantum models have a known connection to classical statistical mechanical models; we exploit this mapping to obtain the scaling of the fidelity metric tensor near criticality. The topological phase transitions manifest themselves in divergences of the fidelity metric across the phase boundaries. These results provide evidence that the fidelity approach is a valuable tool to investigate novel phases lacking a clear characterization in terms of local order parameters.

  15. High-temperature structural phase transition coupled with dielectric switching in an organic-inorganic hybrid crystal: [NH3(CH2)2Br]3CdBr5.

    Science.gov (United States)

    Chen, Hai-Peng; Wang, Zhong-Xia; Chen, Cheng; Lu, Yang; Yin, Zi; Sun, Xiao-Fen; Fu, Da-Wei

    2017-04-05

    Molecular bistable switches (electrical switches "ON" and "OFF") represent a class of highly desirable intelligent materials due to their sensitive switchable responses, simple and environmentally friendly processing, light weight, and mechanical flexibility. In particular, these switches above room temperature with potential practical application are rarely reported. In this work, a new zigzag chained organic-inorganic hybrid compound [NH3(CH2)2Br]3CdBr5 (1), which displays rapidly sensitive dielectric switching reversibility and remarkable switching antifatigue, has been successfully synthesized. Systematic characterization including differential scanning calorimetry measurements (DSC), dielectric measurements, and variable-temperature structural analyses was performed to reveal the phase transition of 1. A couple of reversible heat anomaly peaks at 335.6/323.8 K with a large hysteresis (ca. 11.8 K) were observed in the DSC curve, indicating the first-order type of phase transition. 1 exhibits an obvious dielectric switching at around 327 K, which makes 1 a potential switchable dielectric material. Variable-temperature structural analyses show that the cationic order-disorder motion is the main attribution for the phase transition of 1.

  16. Theoretical Predictions of Phase Transitions at Ultra-high Pressures

    Science.gov (United States)

    Boates, Brian

    2013-06-01

    We present ab initio calculations of the high-pressure phase diagrams of important planetary materials such as CO2, MgSiO3, and MgO. For CO2, we predict a series of distinct liquid phases over a wide pressure (P) and temperature (T) range, including a first-order transition to a dense polymer liquid. We have computed finite-temperature free energies of liquid and solid CO2 phases to determine the melting curve beyond existing measurements and investigate possible phase separation transitions. The interaction of these phase boundaries with the mantle geotherm will also be discussed. Furthermore, we find evidence for a vast pressure-temperature regime where molten MgSiO3 decomposes into liquid SiO2 and solid MgO, with a volume change of approximately 1.2 percent. The demixing transition is driven by the crystallization of MgO ? the reaction only occurs below the high-pressure MgO melting curve. The predicted transition pressure at 10,000 K is in close proximity to an anomaly reported in recent laser-driven shock experiments of MgSiO3. We also present new results for the high-pressure melting curve of MgO and its B1-B2 solid phase transition, with a triple point near 364 GPa and 12,000 K.

  17. Information Dynamics at a Phase Transition

    CERN Document Server

    Sowinski, Damian

    2016-01-01

    We propose a new way of investigating phase transitions in the context of information theory. We use an information-entropic measure of spatial complexity known as configurational entropy (CE) to quantify both the storage and exchange of information in a lattice simulation of a Ginzburg-Landau model with a scalar order parameter coupled to a heat bath. The CE is built from the Fourier spectrum of fluctuations around the mean-field and reaches a minimum at criticality. In particular, we investigate the behavior of CE near and at criticality, exploring the relation between information and the emergence of ordered domains. We show that as the temperature is increased from below, the CE displays three essential scaling regimes at different spatial scales: scale free, turbulent, and critical. Together, they offer an information-entropic characterization of critical behavior where the storage and processing of information is maximized at criticality.

  18. Synthesis, characterisation and phase transition behaviour of temperature-responsive physically crosslinked poly (N-vinylcaprolactam) based polymers for biomedical applications.

    Science.gov (United States)

    Halligan, Shane C; Dalton, Maurice B; Murray, Kieran A; Dong, Yixiao; Wang, Wenxin; Lyons, John G; Geever, Luke M

    2017-10-01

    Poly (N-vinylcaprolactam) (PNVCL) is a polymer which offers superior characteristics for various potential medical device applications. In particular it offers unique thermoresponsive capabilities, which fulfils the material technology constraints required in targeted drug delivery applications. PNVCL phase transitions can be tailored in order to suit the requirements of current and next generation devices, by modifying the contents with regard to the material composition and aqueous polymer concentration. In this study, physically crosslinked Poly (N-vinylcaprolactam)-Vinyl acetate (PNVCL-VAc) copolymers were prepared by photopolymerisation. The structure of the polymers was established by Fourier transform infrared spectroscopy, nuclear magnetic resonance and gel permeation chromatography. The polymers were further characterised using differential scanning calorimetry and swelling studies. Determination of the LCST of the polymers in aqueous solution was achieved by employing four techniques; cloud point, UV-spectrometry, differential scanning calorimetry and rheometry. Sol-gel transition was established using tube inversion method and rheological analysis. This study was conducted to determine the characteristics of PNVCL with the addition of VAc, and to establish the effects on the phase transition. The PNVCL based polymers exhibited a decrease in the LCST as the composition of VAc increased. Sol-gel transition could be controlled by altering the monomeric feed ratio and polymer concentration in aqueous milieu. Importantly all copolymers (10wt% in solution) underwent gelation between 33.6 and 35.9°C, and based on this and the other materials properties recorded in this study, these novel copolymers have potential for use as injectable in situ forming drug delivery systems for targeted drug delivery. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Formamidinium iodide: crystal structure and phase transitions

    Directory of Open Access Journals (Sweden)

    Andrey A. Petrov

    2017-04-01

    Full Text Available At a temperature of 100 K, CH5N2+·I− (I, crystallizes in the monoclinic space group P21/c. The formamidinium cation adopts a planar symmetrical structure [the r.m.s. deviation is 0.002 Å, and the C—N bond lengths are 1.301 (7 and 1.309 (8 Å]. The iodide anion does not lie within the cation plane, but deviates from it by 0.643 (10 Å. The cation and anion of I form a tight ionic pair by a strong N—H...I hydrogen bond. In the crystal of I, the tight ionic pairs form hydrogen-bonded zigzag-like chains propagating toward [20-1] via strong N—H...I hydrogen bonds. The hydrogen-bonded chains are further packed in stacks along [100]. The thermal behaviour of I was studied by different physicochemical methods (thermogravimetry, differential scanning calorimetry and powder diffraction. Differential scanning calorimetry revealed three narrow endothermic peaks at 346, 387 and 525 K, and one broad endothermic peak at ∼605 K. The first and second peaks are related to solid–solid phase transitions, while the third and fourth peaks are attributed to the melting and decomposition of I. The enthalpies of the phase transitions at 346 and 387 K are estimated as 2.60 and 2.75 kJ mol−1, respectively. The X-ray powder diffraction data collected at different temperatures indicate the existence of I as the monoclinic (100–346 K, orthorhombic (346–387 K and cubic (387–525 K polymorphic modifications.

  20. Discovering phase transitions with unsupervised learning

    Science.gov (United States)

    Wang, Lei

    2016-11-01

    Unsupervised learning is a discipline of machine learning which aims at discovering patterns in large data sets or classifying the data into several categories without being trained explicitly. We show that unsupervised learning techniques can be readily used to identify phases and phases transitions of many-body systems. Starting with raw spin configurations of a prototypical Ising model, we use principal component analysis to extract relevant low-dimensional representations of the original data and use clustering analysis to identify distinct phases in the feature space. This approach successfully finds physical concepts such as the order parameter and structure factor to be indicators of a phase transition. We discuss the future prospects of discovering more complex phases and phase transitions using unsupervised learning techniques.

  1. Detection of phase transition via convolutional neural network

    CERN Document Server

    Tanaka, Akinori

    2016-01-01

    We design a Convolutional Neural Network (CNN) which studies correlation between discretized inverse temperature and spin configuration of 2D Ising model and show that it can find a feature of the phase transition without teaching any a priori information for it. We also define a new order parameter via the CNN and show that it provides well approximated critical inverse temperature. In addition, we compare the activation functions for convolution layer and find that the Rectified Linear Unit (ReLU) is important to detect the phase transition of 2D Ising model.

  2. Melting Phase Transitions and Catalytic Activity of Bilayer Gold Nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Yanting Wang; Sergey N. Rashkeev

    2009-06-01

    Recent experiments in oxidation catalysis indicate that bilayer gold nanostructures exhibit exceptional catalytic activity at ambient temperatures. Here we use molecular dynamics simulations to show that an unsupported bilayer gold nanocluster has a broad and mild second-order melting phase transition. The transition is characterized by an interplay between the intralayer and interlayer diffusion processes, and the transition temperature region ranges from about 300 K to 1200 K. We suggest that surface thermal instabilities of partially melted bilayer gold nanoclusters result in their exceptional catalytic activity at ambient temperatures. For gold nanoclusters with more than two layers, the melting transition temperature range narrows, and the activity of the cluster decreases due to the suppression of surface fluctuations. These results systematically explain experimental observations showing that catalytic ability of gold nanoclusters decreases with size.

  3. Estimated phase transition and melting temperature of APTES self-assembled monolayer using surface-enhanced anti-stokes and stokes Raman scattering

    Science.gov (United States)

    Sun, Yingying; Yanagisawa, Masahiro; Kunimoto, Masahiro; Nakamura, Masatoshi; Homma, Takayuki

    2016-02-01

    A structure's temperature can be determined from the Raman spectrum using the frequency and the ratio of the intensities of the anti-Stokes and Stokes signals (the Ias/Is ratio). In this study, we apply this approach and an equation relating the temperature, Raman frequency, and Ias/Is ratio to in-situ estimation of the phase change point of a (3-aminopropyl)triethoxysilane self-assembled monolayer (APTES SAM). Ag nanoparticles were deposited on APTES to enhance the Raman signals. A time-resolved measurement mode was used to monitor the variation in the Raman spectra in situ. Moreover, the structural change in APTES SAM (from ordered to disordered structure) under heating was discussed in detail, and the phase change point (around 118 °C) was calculated.

  4. Quantum Phase Transitions in Quantum Dots

    OpenAIRE

    Rau, I. G.; Amasha, S.; Oreg, Y.; Goldhaber-Gordon, D.

    2013-01-01

    This review article describes theoretical and experimental advances in using quantum dots as a system for studying impurity quantum phase transitions and the non-Fermi liquid behavior at the quantum critical point.

  5. Gravitationally self-induced phase transition

    Science.gov (United States)

    Novello, M.; Duque, S. L. S.

    1990-10-01

    We propose a new mechanism by means of which a phase transition can be stimulated by self-gravitating matter. We suggest that this model could be used to explain the observed isotropy of the Universe.

  6. Phase transition process in DDAB supported lipid bilayer

    Science.gov (United States)

    Isogai, Takumi; Nakada, Sakiko; Yoshida, Naoya; Sumi, Hayato; Tero, Ryugo; Harada, Shunta; Ujihara, Toru; Tagawa, Miho

    2017-06-01

    We report the results of microscope measurements examining the phase transition process of a cationic lipid, Dimethyldioctadecylammonium bromide (DDAB) supported lipid bilayer (SLB). Due to lateral fluidity and strong electrostatic interaction with DNA, SLB serves as a fluid substrate for assembling 2D lattices of DNA functionalized nanoparticles (DNA-NPs): lipid molecules work as carriers for transporting DNA-NPs. By fluorescence microscopy and atomic force microscopy (AFM), two types of phase transitions, which correspond to liquid crystalline-gel and liquid crystalline-interdigitated gel (LβI) ones, were observed in DDAB SLB during cooling. In thermal equilibrium at room temperature both gel and LβI phases have enough adsorbed amounts of DNA-NPs which indicate that both domains have enough surface charge densities for adsorbing DNA-NPs, however, during phase transition DNA-NPs preferably distributed into LβI phase.

  7. Second-order structural phase transitions, free energy curvature, and temperature-dependent anharmonic phonons in the self-consistent harmonic approximation: Theory and stochastic implementation

    Science.gov (United States)

    Bianco, Raffaello; Errea, Ion; Paulatto, Lorenzo; Calandra, Matteo; Mauri, Francesco

    2017-07-01

    The self-consistent harmonic approximation is an effective harmonic theory to calculate the free energy of systems with strongly anharmonic atomic vibrations, and its stochastic implementation has proved to be an efficient method to study, from first-principles, the anharmonic properties of solids. The free energy as a function of average atomic positions (centroids) can be used to study quantum or thermal lattice instability. In particular the centroids are order parameters in second-order structural phase transitions such as, e.g., charge-density-waves or ferroelectric instabilities. According to Landau's theory, the knowledge of the second derivative of the free energy (i.e., the curvature) with respect to the centroids in a high-symmetry configuration allows the identification of the phase-transition and of the instability modes. In this work we derive the exact analytic formula for the second derivative of the free energy in the self-consistent harmonic approximation for a generic atomic configuration. The analytic derivative is expressed in terms of the atomic displacements and forces in a form that can be evaluated by a stochastic technique using importance sampling. Our approach is particularly suitable for applications based on first-principles density-functional-theory calculations, where the forces on atoms can be obtained with a negligible computational effort compared to total energy determination. Finally, we propose a dynamical extension of the theory to calculate spectral properties of strongly anharmonic phonons, as probed by inelastic scattering processes. We illustrate our method with a numerical application on a toy model that mimics the ferroelectric transition in rock-salt crystals such as SnTe or GeTe.

  8. Critical temperature for shape transitions in excited nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Martin, V. [Analisis Numerico, Facultad de Informatica, Universidad Politecnica de Madrid, E-28660, Madrid (Spain); Egido, J.L.; Robledo, L.M. [Departamento de Fisica Teorica, Universidad Autonoma de Madrid, E-28049, Madrid (Spain)

    2004-04-01

    The behavior of shell effects with temperature is studied within the framework of the finite-temperature Hartree-Fock-Bogoliubov theory with the Gogny force. Thermal shape fluctuations in the quadrupole degree of freedom are taken into account in the frame of the Landau theory. Numerical results for the superfluid-to-normal and deformed-to-spherical phase transitions are presented for the nucleus {sup 164}Er. We find that the critical temperature for the deformed-spherical shape transition is much lowered when the thermal shape fluctuations are considered. (orig.)

  9. Dynamical topological quantum phase transitions for mixed states

    Science.gov (United States)

    Heyl, M.; Budich, J. C.

    2017-11-01

    We introduce and study the dynamical probes of band-structure topology in the postquench time evolution of quantum many-body systems initialized in mixed states. Our construction generalizes the notion of dynamical quantum phase transitions (DQPTs), a real-time counterpart of conventional equilibrium phase transitions in quantum dynamics, to finite temperatures and generalized Gibbs ensembles. The nonanalytical signatures hallmarking these mixed-state DQPTs are found to be characterized by observable phase singularities manifesting in the dynamical formation of vortex-antivortex pairs in the interferometric phase of the density matrix. Studying quenches in Chern insulators, we find that changes in the topological properties of the Hamiltonian can be identified in this scenario, without ever preparing a topologically nontrivial or low-temperature initial state. Our observations are of immediate relevance for current experiments aimed at realizing topological phases in ultracold atomic gases.

  10. Novel phase transition in charged dilaton black holes

    Science.gov (United States)

    Dehyadegari, Amin; Sheykhi, Ahmad; Montakhab, Afshin

    2017-10-01

    We disclose a novel phase transition in black hole physics by investigating thermodynamics of charged dilaton black holes in an extended phase space where the charge of the black hole is regarded as a fixed quantity. Along with the usual critical (second-order) as well as the first-order phase transitions in charged black holes, we find that a finite jump in Gibbs free energy is generated by the dilaton-electromagnetic coupling constant α for a certain range of pressure. This novel behavior indicates a small/large black hole zeroth-order phase transition the thermodynamic response function of black hole diverges, e.g., isothermal compressibility. Such zeroth-order transition separates the usual critical point and the standard first-order transition curve. We show that increasing the dilaton parameter (α ) increases the zeroth-order portion of the transition curve. Additionally, we find that the second-order (critical) phase transition exponents are unaffected by the dilaton parameter; however, the condition of positive critical temperature puts an upper bound on the dilaton parameter (α <1 ).

  11. Phase transitions of black holes in massive gravity

    CERN Document Server

    Fernando, Sharmanthie

    2016-01-01

    In this paper we have studied thermodynamics of a black hole in massive gravity in the canonical ensemble. The massive gravity theory in consideration here has a massive graviton due to Lorentz symmetry breaking. The black hole studied here has a scalar charge due to the massive graviton and is asymptotically anti-de Sitter. We have computed various thermodynamical quantities such as temperature, specific heat and free energy. Both the local and global stability of the black hole are studied by observing the behavior of the specific heat and the free energy. We have observed that there is a first order phase transition between small and large black hole for a certain range of the scalar charge. This phase transition is similar to the liquid/gas phase transition at constant temperature for a Van der Waals fluid. The coexistence curves for the small and large black hole branches are also discussed in detail.

  12. Thermal phase transition in a QCD-like holographic model

    Science.gov (United States)

    Evans, Nick; Threlfall, Ed

    2008-11-01

    We investigate the high-temperature phase of a dilaton flow deformation of the anti-de Sitter/conformal field theory correspondence. We argue that these geometries should be interpreted as the N=4 gauge theory perturbed by a SO(6) invariant scalar mass and that the high-temperature phase is just the well-known anti-de Sitter-Schwarzschild solution. We compute, within supergravity, the resulting Hawking-Page phase transition, which in this model can be interpreted as a deconfining transition in which the vacuum expectation value for the operator TrF2 dissolves. In the presence of quarks the model also displays a simultaneous chiral symmetry restoring transition with the Goldstone mode and other quark bound states dissolving into the thermal bath.

  13. Structural Phase Transition Accompanied by Metal - Insulator Transition in PrRu4P12

    OpenAIRE

    Lee, C. H.; Matsuhata, H.; Yamamoto, A.; Ohta, T.; Takazawa, H.; Ueno, K.; Sekine, C.; Shirotani, I.; Hirayama, T.

    2000-01-01

    A structural phase transition has been found using electron diffraction technique in PrRu4P12 accompanied by a metal - insulator (M - I) transition (TMI = 60K). Weak superlattice spots appeared at (H, K, L) (H + K + L = 2n + 1; n is an integer) position at a temperature of T = 12 K and 40 K. Above T = 70 K, the spots completely vanished. The space group of the low temperature phase is probably Pm3. This is the first observation of a symmetry other than Im3 in skutterudite compounds.

  14. Superfluid phase transitions in dense neutron matter.

    Science.gov (United States)

    Khodel, V A; Clark, J W; Zverev, M V

    2001-07-16

    The phase transitions in a realistic system with triplet pairing, dense neutron matter, have been investigated. The spectrum of phases of the 3P2-3F2 model, which adequately describes pairing in this system, is analytically constructed with the aid of a separation method for solving BCS gap equations in states of arbitrary angular momentum. In addition to solutions involving a single value of the magnetic quantum number (and its negative), there exist ten real multicomponent solutions. Five of the corresponding angle-dependent order parameters have nodes, and five do not. In contrast to the case of superfluid 3He, transitions occur between phases with nodeless order parameters.

  15. Phase transition – Break down the walls

    DEFF Research Database (Denmark)

    Wandahl, Søren

    2012-01-01

    . In a popular term this problem is often called “over the wall syndrome”. The manufacturing industry has worked with this for many years, in e.g. integrated product development, concurrent engineering, supply chain management, etc. Now the construction industry needs to focus more on these crucial inter......-phase issues of the construction process. This research first identifies the problems theoretically, and looks into which framework to be used in understanding of the phase transition problem. This combined with data from interviews reveal 8 major issues in phase transition, which decrease the value...

  16. Topological phase transitions in the gauged BPS baby Skyrme model

    Science.gov (United States)

    Adam, C.; Naya, C.; Romanczukiewicz, T.; Sanchez-Guillen, J.; Wereszczynski, A.

    2015-05-01

    We demonstrate that the gauged BPS baby Skyrme model with a double vacuum potential allows for phase transitions from a non-solitonic to a solitonic phase, where the latter corresponds to a ferromagnetic liquid. Such a transition can be generated by increasing the external pressure P or by turning on an external magnetic field H. As a consequence, the topological phase where gauged BPS baby skyrmions exist, is a higher density phase. For smaller densities, obtained for smaller values of P and H, a phase without solitons is reached. We find the critical line in the P, H parameter space. Furthermore, in the soliton phase, we find the equation of state for the baby skyrmion matter V = V( P,H) at zero temperature, where V is the "volume", i.e., area of the solitons.

  17. Topological phase transitions in the gauged BPS baby Skyrme model

    Energy Technology Data Exchange (ETDEWEB)

    Adam, C.; Naya, C. [Departamento de Física de Partículas, Universidad de Santiago de Compostela andInstituto Galego de Física de Altas Enerxias (IGFAE), Santiago de Compostela, E-15782 (Spain); Romanczukiewicz, T. [Institute of Physics, Jagiellonian University, Lojasiecza 11, Kraków, 30-348 (Poland); Sanchez-Guillen, J. [Departamento de Física de Partículas, Universidad de Santiago de Compostela andInstituto Galego de Física de Altas Enerxias (IGFAE), Santiago de Compostela, E-15782 (Spain); Wereszczynski, A. [Institute of Physics, Jagiellonian University, Lojasiecza 11, Kraków, 30-348 (Poland)

    2015-05-29

    We demonstrate that the gauged BPS baby Skyrme model with a double vacuum potential allows for phase transitions from a non-solitonic to a solitonic phase, where the latter corresponds to a ferromagnetic liquid. Such a transition can be generated by increasing the external pressure P or by turning on an external magnetic field H. As a consequence, the topological phase where gauged BPS baby skyrmions exist, is a higher density phase. For smaller densities, obtained for smaller values of P and H, a phase without solitons is reached. We find the critical line in the P,H parameter space. Furthermore, in the soliton phase, we find the equation of state for the baby skyrmion matter V=V(P,H) at zero temperature, where V is the “volume”, i.e., area of the solitons.

  18. Effects of calcining temperatures of Eu{sup 2+} and Dy{sup 3+} ion-codoped calcia-alumina binary compounds on their phase transition and luminescence properties

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Chen-Jui, E-mail: cjliang@fcu.edu.tw; Siao, Hao-Yi

    2017-06-01

    In this study, phase evolution as a function of calcining temperature in calcia-alumina binary compound phosphors was examined to interpret their luminescence properties. The binary compounds were prepared through a coprecipitation method employing potassium carbonate as the precipitant to obtain precursors with a high-precision stoichiometric composition for the calcination. The results indicate that the morphology, surface properties, and infrared transmittance of the prepared phosphors were affected by the calcining temperature. X-ray diffraction analysis results enabled identification of Ca{sub 12}Al{sub 14}O{sub 33}, CaAl{sub 2}O{sub 4}, and CaAl{sub 4}O{sub 7} phase transitions at various calcining temperatures. The amount of the CaAl{sub 2}O{sub 4} phase increased with the calcining temperature within the range of 700–1060 °C. The Ca{sub 12}Al{sub 14}O{sub 33} and CaAl{sub 4}O{sub 7} phases exhibited trends opposite to that of the CaAl{sub 2}O{sub 4} phase. When the calcining temperature reached 980 °C, the CaAl{sub 2}O{sub 4} phase (60.5%) was determined to be the main phase in the structure, and excellent emission intensity at an emission band of 449 nm was observed as a result of the complete substitution of Eu{sup 2+} for Ca{sup 2+}. The emission intensity corresponding to Eu{sup 2+} 4f{sup 6}5d{sup 1} → 4f{sup 7} decreased slightly when the temperature reached 1060 °C because of more monoclinic reciprocal CaAl{sub 4}O{sub 7} phase (81.5%) formation, causing the transfer of some Eu{sup 2+} to Eu{sup 3+}, during which strong photoluminescence spectra of Eu{sup 3+5}D{sub 0} → {sup 7}F{sub j} (j = 0, 1, 2, 3, 4) within the wavelength range of 570–720 nm were observed. Because the strong photoluminescence spectra of the Eu{sup 2+} and Eu{sup 3+} emissions were together within the wavelength range of 449–720 nm in this phosphor, the photoluminescence was white light. One moderately intense emission band in the infrared region was observed and

  19. Phase Transitions in Antibody Solutions: from Pharmaceuticals to Human Disease

    Science.gov (United States)

    Wang, Ying; Lomakin, Aleksey; Benedek, George; Dana Farber Cancer Institute Collaboration; Amgen Inc. Collaboration

    2014-03-01

    Antibodies are very important proteins. Natural antibodies play essential role in the immune system of human body. Pharmaceutical antibodies are used as drugs. Antibodies are also indispensable tools in biomedical research and diagnostics. Recently, a number of observations of phase transitions of pharmaceutical antibodies have been reported. These phase transitions are undesirable from the perspective of colloid stability of drug solutions in processing and storage, but can be used for protein purification, X-ray crystallography, and improving pharmokinetics of drugs. Phase transitions of antibodies can also take place in human body, particularly in multiple myeloma patients who overproduce monoclonal antibodies. These antibodies, in some cases, crystallize at body temperature and cause severe complications called cryoglobulinemia. I will present the results of our current studies on phase transitions of both pharmaceutical antibodies and cryoglobulinemia-associated antibodies. These studies have shown that different antibodies have different propensity to undergo phase transitions, but their phase behavior has universal features which are remarkably different from those of spherical proteins. I will discuss how studies of phase behavior can be useful in assessing colloid stability of pharmaceutical antibodies and in early diagnostics of cryoglobulinemia, as well as general implications of the fact that some antibodies can precipitate at physiological conditions.

  20. LDRD final report : raman spectroscopic measurements to monitor the HMX beta-delta phase transition.

    Energy Technology Data Exchange (ETDEWEB)

    Renlund, Anita Mariana; Tappan, Alexander Smith; Miller, Jill C.

    2000-11-01

    The HMX {beta}-{delta} solid-solid phase transition, which occurs as HMX is heated near 170 C, is linked to increased reactivity and sensitivity to initiation. Thermally damaged energetic materials (EMs) containing HMX therefore may present a safety concern. Information about the phase transition is vital to predictive safety models for HMX and HMX-containing EMs. We report work on monitoring the phase transition with real-time Raman spectroscopy aimed towards obtaining a better understanding of physical properties of HMX through the phase transition. HMX samples were confined in a cell of minimal free volume in a displacement-controlled or load-controlled arrangement. The cell was heated and then cooled at controlled rates while real-time Raman spectroscopic measurements were performed. Raman spectroscopy provides a clear distinction between the phases of HMX because the vibrational transitions of the molecule change with conformational changes associated with the phase transition. Temperature of phase transition versus load data are presented for both the heating and cooling cycles in the load-controlled apparatus, and general trends are discussed. A weak dependence of the temperature of phase transition on load was discovered during the heating cycle, with higher loads causing the phase transition to occur at a higher temperature. This was especially true in the temperature of completion of phase transition data as opposed to the temperature of onset of phase transition data. A stronger dependence on load was observed in the cooling cycle, with higher loads causing the reverse phase transitions to occur at a higher cooling temperature. Also, higher loads tended to cause the phase transition to occur over a longer period of time in the heating cycle and over a shorter period of time in the cooling cycle. All three of the pure HMX phases ({alpha}, {beta} and {delta}) were detected on cooling of the heated samples, either in pure form or as a mixture.

  1. Corrosion behaviour, microstructure and phase transitions of Zn ...

    Indian Academy of Sciences (India)

    Unknown

    nique. The microstructure and phase transitions of the alloy are also investigated. 2. Experimental. Zn-based ingot casting alloy was prepared from high purity materials (99⋅99% Zn, 99⋅99% Al, 99⋅99% Cu). The alloy was first melted in graphite crucible in a high temperature furnace, and then it was poured in a steel mold ...

  2. Chiral phase transitions in quantum chromodynamics at finite ...

    Indian Academy of Sciences (India)

    pp. 1029–1033. Chiral phase transitions in quantum chromodynamics at finite temperature: Hard-thermal-loop resummed. Dyson–Schwinger equation in the real time formalism. HISAO NAKKAGAWA1, HIROSHI YOKOTA1, KOJI YOSHIDA1 and YUKO FUEKI2. 1Institute for Natural Sciences, Nara University, Nara 631-8502 ...

  3. Corrosion behaviour, microstructure and phase transitions of Zn ...

    Indian Academy of Sciences (India)

    This paper is aimed at investigating the corrosion behaviour, microstructure and phase transitions of Zn-based alloys with different compositions. The corrosion tests are carried out both in acidic medium using 1 N HCl solution and in temperature dependence of thermogravimetric analysis (TGA). In the two different media, ...

  4. Gradual phase transition between the smectic- C* and smectic- CA* phases and the thresholdless antiferroelectricity

    OpenAIRE

    VIJ, JAGDISH; SONG, JANG-KUN; Fukuda, Atsuo

    2008-01-01

    PUBLISHED We have constructed the phase diagrams for a binary-mixture system of antiferroelectric and ferroelectric liquid-crystalline materials in both thick and thin cells. In the phase diagrams the boundary between the smectic-C* and smectic-CA * phases runs almost parallel to the temperature axis below from ca. 70 ?C down to at least ?25 ?C. The SmC*-SmCA * phase transition for a thin cell shows a large supercooling, and a gradual transition occurs near the boundary. ...

  5. Intrinsic evolutions of dielectric function and electronic transition in tungsten doping Ge{sub 2}Sb{sub 2}Te{sub 5} phase change films discovered by ellipsometry at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Guo, S.; Ding, X. J.; Zhang, J. Z.; Hu, Z. G., E-mail: zghu@ee.ecnu.edu.cn; Chu, J. H. [Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronic Engineering, East China Normal University, Shanghai 200241 (China); Ji, X. L.; Wu, L. C.; Song, Z. T. [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China)

    2015-02-02

    Tungsten (W) doping effects on Ge{sub 2}Sb{sub 2}Te{sub 5} (GSTW) phase change films with different concentrations (3.2, 7.1, and 10.8%) have been investigated by variable-temperature spectroscopic ellipsometry. The dielectric functions from 210 K to 660 K have been evaluated with the aid of Tauc-Lorentz and Drude dispersion models. The analysis of Tauc gap energy (E{sub g}) and partial spectral weight integral reveal the correlation between optical properties and local structural change. The order degree increment and chemical bond change from covalent to resonant should be responsible for band gap narrowing and electronic transition enhancement during the phase change process. It is found that the elevated crystalline temperature for GSTW can be related to improved disorder degree. Furthermore, the shrinkage of E{sub g} for GSTW should be attributed to the enhanced metallicity compared with undoped GST.

  6. Direct investigations of deformation and yield induced structure transitions in polyamide 6 below glass transition temperature with WAXS and SAXS

    DEFF Research Database (Denmark)

    Guo, Huilong; Wang, Jiayi; Zhou, Chengbo

    2015-01-01

    Deformation and yield induced structure transitions of polyamide 6 (PA6) were detected with the combination of the wide- and small-angle X-ray scattering (WAXS and SAXS) at 30 degrees C below glass transition temperature (T-g) of PA6. During deformation, gamma-alpha phase transition was found...

  7. Phase transition in mesonic bags, using the sound velocity

    Energy Technology Data Exchange (ETDEWEB)

    Araujo Junior, C.F.; Tomio, L. [UNESP, Sao Paulo, SP (Brazil). Inst. de Fisica Teorica; Dey, J.; Dey, M. [Lady Brabourne Coll., Calcutta (India). Dept. of Physics

    1995-12-31

    Sound velocity, u{sub s}, was shown in lattice theory to become zero at a transition point. Besides the fact that sharp transitions are perhaps absent in QCD, one looks for physical quantities like that which may reflect a second order phase change. We show that even the simple bag model, is able to reproduce the lattice result for the masses, and the sound velocity, at finite would be interesting to check the last conclusion in present day finite temperature lattice theory, as different transition points are indicated by particle emission T in heavy ion reactions. (author) 16 refs., 1 tab.

  8. Detection of Phase Transition via Convolutional Neural Networks

    Science.gov (United States)

    Tanaka, Akinori; Tomiya, Akio

    2017-06-01

    A convolutional neural network (CNN) is designed to study correlation between the temperature and the spin configuration of the two-dimensional Ising model. Our CNN is able to find the characteristic feature of the phase transition without prior knowledge. Also a novel order parameter on the basis of the CNN is introduced to identify the location of the critical temperature; the result is found to be consistent with the exact value.

  9. Compression-induced phase transition of GaN bulk from wurtzite phase to five-fold coordination hexagonal phase

    Science.gov (United States)

    Qian, Yu; Shang, Fulin; Wan, Qiang; Yan, Yabin

    2017-09-01

    The phase transformation of GaN bulk from the Wurtzite phase (WZ) to the hexagonal phase (HX) is studied by molecular dynamics simulation. The mechanical response and atomic structural evolution of transition are analyzed in detail. In addition, the loading rate effect on the phase transition is determined, that is, the phase transition ratio declines with a decrease of the strain rate. The WZ GaN bulk completely transforms into the HX phase in the case of compression at an ultrahigh strain rate. However, at a relatively slower strain rate, the HX phase of GaN partly nucleates and the untransformed regions are proved to be elastic deformed regions. Combined with an energy analysis, two atomic movement modes are recognized as the inducements for the phase transition and formation of elastic deformed regions. The first mode, which is responsible for the formation of elastic deformed regions, is an atomic sliding motion along the c {0001} planes. The second mode is a radial stretching atomic motion. The radial stretching motion, which requires a lot of energy, induces the WZ-HX phase transition. Moreover, the phase transition is affected drastically by the rise of temperature.

  10. Thermogeometric phase transition in a unified framework

    CERN Document Server

    Banerjee, Rabin; Samanta, Saurav

    2016-01-01

    Using geomterothermodynamics (GTD), we investigate the phase transition of black hole in a metric independent way. We show that for any black hole, curvature scalar (of equilibrium state space geometry) is singular at the point where specific heat diverges. Previously such a result could only be shown by taking specific examples on a case by case basis. A different type of phase transition, where inverse specific heat diverges, is also studied within this framework. We show that in the latter case, metric (of equilibrium state space geometry) is singular instead of curvature scalar. Since a metric singularity may be a coordinate artifact, we propose that GTD indicates that it is the singularity of specific heat and not inverse specific heat which indicates a phase transition of black holes.

  11. Thermogeometric phase transition in a unified framework

    Energy Technology Data Exchange (ETDEWEB)

    Banerjee, Rabin, E-mail: rabin@bose.res.in [S.N. Bose National Centre for Basic Sciences, JD Block, Sector III, Salt Lake, Kolkata 700098 (India); Majhi, Bibhas Ranjan, E-mail: bibhas.majhi@iitg.ernet.in [Department of Physics, Indian Institute of Technology Guwahati, Guwahati 781039, Assam (India); Samanta, Saurav, E-mail: srvsmnt@gmail.com [Department of Physics, Narasinha Dutt College, 129, Belilious Road, Howrah 711101 (India)

    2017-04-10

    Using geomterothermodynamics (GTD), we investigate the phase transition of black hole in a metric independent way. We show that for any black hole, curvature scalar (of equilibrium state space geometry) is singular at the point where specific heat diverges. Previously such a result could only be shown by taking specific examples on a case by case basis. A different type of phase transition, where inverse specific heat diverges, is also studied within this framework. We show that in the latter case, metric (of equilibrium state space geometry) is singular instead of curvature scalar. Since a metric singularity may be a coordinate artifact, we propose that GTD indicates that it is the singularity of specific heat and not inverse specific heat which indicates a phase transition of black holes.

  12. Calculated Phase Diagram for the γ⇌α Transition in Ce

    DEFF Research Database (Denmark)

    Johansson, Børje; Abrikosov, I. A.; Aldén, Magnus

    1995-01-01

    We have calculated the pressure-temperature phase diagram of the γ⇌α isostructural transition in Ce on the basis of the Mott transition model. The theory correctly describes the linear variation of the transition temperature with pressure and the existence of a critical point. The quantitative ag...

  13. Phase transitions in chiral magnets from Monte Carlo simulations

    Science.gov (United States)

    Belemuk, A. M.; Stishov, S. M.

    2017-06-01

    Motivated by the unusual temperature dependence of the specific heat in MnSi, comprising a combination of a sharp first-order feature accompanied by a broad hump, we study the extended Heisenberg model with competing exchange J and anisotropic Dzyaloshinskii-Moriya D interactions in a broad range of ratio D /J . Utilizing classical Monte Carlo simulations we find an evolution of the temperature dependence of the specific heat and magnetic susceptibility with variation of D /J . Combined with an analysis of the Bragg intensity patterns, we clearly demonstrate that the observed puzzling hump in the specific heat of MnSi originates from smearing out of the virtual ferromagnetic second-order phase transition by helical fluctuations which manifest themselves in the transient multiple spiral state. These fluctuations finally condense into the helical ordered phase via a first-order phase transition, as is indicated by the specific heat peak. Thus the model demonstrates a crossover from a second-order to a first-order transition with increasing D /J . Upon further increasing D /J another crossover from a first-order to a second-order transition takes place in the system. Moreover, the results of the calculations clearly indicate that these competing interactions are the primary factors responsible for the appearance of first-order phase transitions in helical magnets with the Dzyaloshinskii-Moriya interaction.

  14. Phase Transition Behavior of HPMC-AA and Preparation of HPMC-PAA Nanogels

    Directory of Open Access Journals (Sweden)

    Risheng Yao

    2011-01-01

     nm diameters characterized by transmission electron microscope and dynamic light scattering. The HPMC-PAA nanogels exhibit the temperature phase transition behaviors, and these nanogels' volume phase transition temperature is close to the LCST of HPMC/AA system.

  15. Queueing phase transition: theory of translation.

    Science.gov (United States)

    Romano, M Carmen; Thiel, Marco; Stansfield, Ian; Grebogi, Celso

    2009-05-15

    We study the current of particles on a lattice, where to each site a different hopping probability has been associated and the particles can move only in one direction. We show that the queueing of the particles behind a slow site can lead to a first-order phase transition, and derive analytical expressions for the configuration of slow sites for this to happen. We apply this stochastic model to describe the translation of mRNAs. We show that the first-order phase transition, uncovered in this work, is the process responsible for the classification of the proteins having different biological functions.

  16. Metamagnetic Anomalies near Dynamic Phase Transitions.

    Science.gov (United States)

    Riego, P; Vavassori, P; Berger, A

    2017-03-17

    We report the existence of anomalous metamagnetic fluctuations in the vicinity of the dynamic phase transition (DPT) that do not occur for the corresponding thermodynamic behavior of simple ferromagnets. Our results demonstrate that key characteristics associated with the DPT are qualitatively different from conventional thermodynamic phase transitions. We also provide evidence that these differences are tunable by showing that the presence of metamagnetic fluctuations and the size of the critical scaling regime depend strongly on the amplitude of the oscillating field that is driving the DPT in the first place.

  17. Exceptional Points and Dynamical Phase Transitions

    Directory of Open Access Journals (Sweden)

    I. Rotter

    2010-01-01

    Full Text Available In the framework of non-Hermitian quantum physics, the relation between exceptional points,dynamical phase transitions and the counter intuitive behavior of quantum systems at high level density is considered. The theoretical results obtained for open quantum systems and proven experimentally some years ago on a microwave cavity, may explain environmentally induce deffects (including dynamical phase transitions, which have been observed in various experimental studies. They also agree(qualitatively with the experimental results reported recently in PT symmetric optical lattices.

  18. Quasi-phases and pseudo-transitions in one-dimensional models with nearest neighbor interactions

    Science.gov (United States)

    de Souza, S. M.; Rojas, Onofre

    2018-01-01

    There are some particular one-dimensional models, such as the Ising-Heisenberg spin models with a variety of chain structures, which exhibit unexpected behaviors quite similar to the first and second order phase transition, which could be confused naively with an authentic phase transition. Through the analysis of the first derivative of free energy, such as entropy, magnetization, and internal energy, a "sudden" jump that closely resembles a first-order phase transition at finite temperature occurs. However, by analyzing the second derivative of free energy, such as specific heat and magnetic susceptibility at finite temperature, it behaves quite similarly to a second-order phase transition exhibiting an astonishingly sharp and fine peak. The correlation length also confirms the evidence of this pseudo-transition temperature, where a sharp peak occurs at the pseudo-critical temperature. We also present the necessary conditions for the emergence of these quasi-phases and pseudo-transitions.

  19. Supersymmetric phase transition in Josephson-tunnel-junction arrays

    Energy Technology Data Exchange (ETDEWEB)

    Foda, O.

    1988-08-31

    The fully frustrated XY model in two dimensions exhibits a vortex-unbinding as well as an Ising transition. If the Ising transition overlaps with the critical line that ends on the vortex transition: T/sub I/less than or equal toT/sub V/, then the model is equivalent, at the overlap temperature, to a free massless field theory of 1 boson and 1 Majorana fermion, which is a superconformal field theory, of central charge c=3/2. The model is experimentally realized in terms of an array of Josephson-tunnel junctions in a transverse magnetic field. The experiment reveals a phase transition consistent with T/sub I/=T/sub V/. Thus, at the critical temperature, the array provides a physical realization of a supersymmetric quantum field theory.

  20. Non-equilibrium physics at a holographic chiral phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Evans, Nick; Kim, Keun-young [Southampton Univ. (United Kingdom). School of Physics and Astronomy; Kavli Institute for Theoretical Physics China, Beijing (China); Kalaydzhyan, Tigran; Kirsch, Ingo [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2010-11-15

    The D3/D7 system holographically describes an N=2 gauge theory which spontaneously breaks a chiral symmetry by the formation of a quark condensate in the presence of a magnetic field. At finite temperature it displays a first order phase transition. We study out of equilibrium dynamics associated with this transition by placing probe D7 branes in a geometry describing a boost-invariant expanding or contracting plasma. We use an adiabatic approximation to track the evolution of the quark condensate in a heated system and reproduce the phase structure expected from equilibrium dynamics. We then study solutions of the full partial differential equation that describes the evolution of out of equilibrium configurations to provide a complete description of the phase transition including describing aspects of bubble formation. (orig.)

  1. Structural Phase Transition of ThC Under High Pressure.

    Science.gov (United States)

    Yu, Cun; Lin, Jun; Huai, Ping; Guo, Yongliang; Ke, Xuezhi; Yu, Xiaohe; Yang, Ke; Li, Nana; Yang, Wenge; Sun, Baoxing; Xie, Ruobing; Xu, Hongjie

    2017-03-07

    Thorium monocarbide (ThC) as a potential fuel for next generation nuclear reactor has been subjected to its structural stability investigation under high pressure, and so far no one reported the observation of structure phase transition induced by pressure. Here, utilizing the synchrotron X-ray diffraction technique, we for the first time, experimentally revealed the phase transition of ThC from B1 to P4/nmm at pressure of ~58 GPa at ambient temperature. A volume collapse of 10.2% was estimated during the phase transition. A modulus of 147 GPa for ThC at ambient pressure was obtained and the stoichiometry was attributed to the discrepancy of this value to the previous reports.

  2. A MATLAB GUI to study Ising model phase transition

    Science.gov (United States)

    Thornton, Curtislee; Datta, Trinanjan

    We have created a MATLAB based graphical user interface (GUI) that simulates the single spin flip Metropolis Monte Carlo algorithm. The GUI has the capability to study temperature and external magnetic field dependence of magnetization, susceptibility, and equilibration behavior of the nearest-neighbor square lattice Ising model. Since the Ising model is a canonical system to study phase transition, the GUI can be used both for teaching and research purposes. The presence of a Monte Carlo code in a GUI format allows easy visualization of the simulation in real time and provides an attractive way to teach the concept of thermal phase transition and critical phenomena. We will also discuss the GUI implementation to study phase transition in a classical spin ice model on the pyrochlore lattice.

  3. Ab initio theory of helix <-> coil phase transition

    DEFF Research Database (Denmark)

    Yakubovich, Alexander V.; Solov'yov, Ilia; Solov'yov, Andrey V.

    2008-01-01

    In this paper, we suggest a theoretical method based on the statistical mechanics for treating the alpha-helix <-> random coil transition in alanine polypeptides. We consider this process as a first-order phase transition and develop a theory which is free of model parameters and is based solely ...... twisting. The suggested theory is general and with some modification can be applied for the description of phase transitions in other complex molecular systems (e.g. proteins, DNA, nanotubes, atomic clusters, fullerenes).......In this paper, we suggest a theoretical method based on the statistical mechanics for treating the alpha-helix random coil transition in alanine polypeptides. We consider this process as a first-order phase transition and develop a theory which is free of model parameters and is based solely...... on fundamental physical principles. It describes essential thermodynamical properties of the system such as heat capacity, the phase transition temperature and others from the analysis of the polypeptide potential energy surface calculated as a function of two dihedral angles, responsible for the polypeptide...

  4. Phase Transitions in Electron Spin Resonance Under Continuous Microwave Driving

    Science.gov (United States)

    Karabanov, A.; Rose, D. C.; Köckenberger, W.; Garrahan, J. P.; Lesanovsky, I.

    2017-10-01

    We study an ensemble of strongly coupled electrons under continuous microwave irradiation interacting with a dissipative environment, a problem of relevance to the creation of highly polarized nonequilibrium states in nuclear magnetic resonance. We analyze the stationary states of the dynamics, described within a Lindblad master equation framework, at the mean-field approximation level. This approach allows us to identify steady-state phase transitions between phases of high and low polarization controlled by the distribution of disordered electronic interactions. We compare the mean-field predictions to numerically exact simulations of small systems and find good agreement. Our study highlights the possibility of observing collective phenomena, such as metastable states, phase transitions, and critical behavior, in appropriately designed paramagnetic systems. These phenomena occur in a low-temperature regime which is not theoretically tractable by conventional methods, e.g., the spin-temperature approach.

  5. Hawking–Page phase transition in new massive gravity

    Directory of Open Access Journals (Sweden)

    Shao-Jun Zhang

    2015-07-01

    Full Text Available We consider Hawking–Page phase transition between the BTZ black hole with M≥0 and the thermal soliton with M=−1 in new massive gravity. By comparing the on-shell free energies, we can see that there exists a critical temperature. The thermal soliton is more probable than the black hole below the critical temperature while the black hole is more probable than the thermal soliton above the critical temperature. By consistently constructing the off-shell free energies taking into account the conical singularity, we show that there exist infinite non-equilibrium states connecting the BTZ black hole and the thermal soliton, so that they provide a picture of continuous evolution of the phase transition.

  6. Space Storm as a Dynamical Phase Transition

    Science.gov (United States)

    Wanliss, J. A.

    2006-12-01

    Fluctuations of the DST index were analyzed for several magnetic storms preceded by more than a week of extremely quiet conditions to establish that there is a rapid and unidirectional change in the Hurst scaling exponent at the time of storm onset. That is, the transition is accompanied by the specific signature of a rapid unidirectional change in the temporal fractal scaling of fluctuations in DST, signaling the formation of a new dynamical phase (or mode) which is considerably more organized than the background state. We compare these results to a model of multifractional Brownian motion and suggest that the relatively sudden change from a less correlated to a more correlated pattern of multiscale fluctuations at storm onset can be characterized in terms of nonequilibrium dynamical phase transitions. Initial results show that a dynamical transition in solar wind VBs is correlated with the storm onset for intense storms, suggesting that the transition observed in DST is of external solar wind origin, rather than internal magnetospheric origin. On the other hand, some results show a dynamical transition in solar wind scaling exponents not matched in DST. As well, we also present results for small storms where there is a strong dynamical transition in DST without a similar changes in the VBs scaling statistics. The results for small storms seem to reduce the importance of the solar wind fluctuations but the evidence for the intense storms seems to point to the solar wind as being responsible for providing the scale free properties in the DST fluctuations.

  7. Late time phase transition as dark energy

    Indian Academy of Sciences (India)

    Instituto de F isica, UNAM, Apdo. Postal 20-364, 01000 M exico D.F., M exico. Abstract. We show that the dark energy field can naturally be described by the scalar condensates of a non-abelian gauge group. This gauge group is unified with the standard model gauge groups and it has a late time phase transition. The small ...

  8. The simulation of entropic phase transitions

    NARCIS (Netherlands)

    Frenkel, D.

    1994-01-01

    This paper reviews recent (numerical) progress in the understanding of entropic phase transitions in complex fluids. In particular, I discuss (liquid-)crystal formation and demixing in binary mixtures. In some cases it appears that lessons learnt in the study of complex fluids may have an unexpected

  9. Phase Transitions, Diffraction Studies and Marginal Dimensionality

    DEFF Research Database (Denmark)

    Als-Nielsen, Jens Aage

    1985-01-01

    Continuous phase transitions and the associated critical phenomena have been one of the most active areas of research in condensed matter physics for several decades. This short review is only one cut through this huge subject and the author has chosen to emphasize diffraction studies as a basic ...

  10. Late time phase transition as dark energy

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 62; Issue 3. Late time phase transition as dark energy. A De La Macorra. Cosmology Volume 62 Issue 3 March 2004 pp 779-783. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/pram/062/03/0779-0783. Keywords.

  11. Hysteresis in the phase transition of chocolate

    Science.gov (United States)

    Ren, Ruilong; Lu, Qunfeng; Lin, Sihua; Dong, Xiaoyan; Fu, Hao; Wu, Shaoyi; Wu, Minghe; Teng, Baohua

    2016-01-01

    We designed an experiment to reproduce the hysteresis phenomenon of chocolate appearing in the heating and cooling process, and then established a model to relate the solidification degree to the order parameter. Based on the Landau-Devonshire theory, our model gave a description of the hysteresis phenomenon in chocolate, which lays the foundations for the study of the phase transition behavior of chocolate.

  12. Monte Carlo Simulation of Phase Transitions

    OpenAIRE

    村井, 信行; N., MURAI; 中京大学教養部

    1983-01-01

    In the Monte Carlo simulation of phase transition, a simple heat bath method is applied to the classical Heisenberg model in two dimensions. It reproduces the correlation length predicted by the Monte Carlo renor-malization group and also computed in the non-linear σ model

  13. Passive Supporters of Terrorism and Phase Transitions

    CERN Document Server

    August, Friedrich; Delitzscher, Sascha; Hiller, Gerald; Krueger, Tyll

    2010-01-01

    We discuss some social contagion processes to describe the formation and spread of radical opinions. The dynamics of opinion spread involves local threshold processes as well as mean field effects. We calculate and observe phase transitions in the dynamical variables resulting in a rapidly increasing number of passive supporters. This strongly indicates that military solutions are inappropriate.

  14. Phase Transition in Strongly Degenerate Hydrogen Plasma

    OpenAIRE

    Filinov, V. S.; Fortov, V. E.; Bonitz, M.; Levashov, P. R.

    2001-01-01

    Direct fermionic path-integral Monte-Carlo simulations of strongly coupled hydrogen are presented. Our results show evidence for the hypothetical plasma phase transition. Its most remarkable manifestation is the appearance of metallic droplets which are predicted to be crucial for the electrical conductivity allowing to explain the rapid increase observed in recent shock compression measurments.

  15. Phase Change Fabrics Control Temperature

    Science.gov (United States)

    2009-01-01

    Originally featured in Spinoff in 1997, Outlast Technologies Inc. (formerly Gateway Technologies Inc.) has built its entire product line on microencapsulated phase change materials, developed in Small Business Innovation Research (SBIR) contracts with Johnson Space Center after initial development for the U.S. Air Force. The Boulder, Colorado-based company acquired the exclusive patent rights and now integrates these materials into textiles or onto finished apparel, providing temperature regulation in bedding materials and a full line of apparel for both ordinary and extreme conditions.

  16. Nonuniversal surface behavior of dynamic phase transitions.

    Science.gov (United States)

    Riego, Patricia; Berger, Andreas

    2015-06-01

    We have studied the dynamic phase transition (DPT) of the kinetic Ising model in systems with surfaces within the mean-field approximation. Varying the surface exchange coupling strength J(s), the amplitude of the externally applied oscillating field h(0), and its period P, we explore the dynamic behavior of the layer-dependent magnetization and the associated DPTs. The surface phase diagram shows several features that resemble those of the equilibrium case, with an extraordinary bulk transition and a surface transition for high J(s) values, independent from the value of h(0). For low J(s), however, h(0) is found to be a crucial parameter that leads to nonuniversal surface behavior at the ordinary bulk transition point. Specifically, we observed here a bulk-supported surface DPT for high field amplitudes h(0) and correspondingly short critical periods P(c), whereas this surface transition simultaneous to the bulk one is suppressed for slow critical dynamics occurring for low values of h(0). The suppression of the DPT for low h(0) not only occurs for the topmost surface layer, but also affects a significant number of subsurface layers. We find that the key physical quantity that explains this nonuniversal behavior is the time correlation between the dynamic surface and bulk magnetizations at the bulk critical point. This time correlation has to pass a threshold value to trigger a bulk-induced DPT in the surface layers. Otherwise, dynamic phase transitions are absent at the surface in stark contrast to the equilibrium behavior of the corresponding thermodynamic Ising model. Also, we have analyzed the penetration depth of the dynamically ordered phase for the surface DPT that occurs for large J(s) values. Here we find that the penetration depth depends strongly on J(s) and behaves identically to the corresponding equilibrium Ising model.

  17. Equilibrium Statistical Physics Phases of Matter and Phase Transitions

    CERN Document Server

    Baus, Marc

    2008-01-01

    This is a textbook which gradually introduces the student to the statistical mechanical study of the different phases of matter and to the phase transitions between them. Throughout, only simple models of both ordinary and soft matter are used but these are studied in full detail. The subject is developed in a pedagogical manner, starting from the basics, going from the simple ideal systems to the interacting systems, and ending with the more modern topics. The latter include the renormalisation group approach to critical phenomena, the density functional theory of interfaces, the topological defects of nematic liquid crystals and the kinematic aspects of the phase transformation process. This textbook provides the student with a complete overview, intentionally at an introductory level, of the theory of phase transitions. References include suggestions for more detailed treatments and four appendices supply overviews of the mathematical tools employed in the text.

  18. Comparing two tetraalkylammonium ionic liquids. II. Phase transitions

    Science.gov (United States)

    Lima, Thamires A.; Paschoal, Vitor H.; Faria, Luiz F. O.; Ribeiro, Mauro C. C.; Ferreira, Fabio F.; Costa, Fanny N.; Giles, Carlos

    2016-06-01

    Phase transitions of the ionic liquids n-butyl-trimethylammonium bis(trifluoromethanesulfonyl)imide, [N1114][NTf2], and methyl-tributylammonium bis(trifluoromethanesulfonyl)imide, [N1444][NTf2], were investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD) measurements, and Raman spectroscopy. XRD and Raman spectra were obtained as a function of temperature at atmospheric pressure, and also under high pressure at room temperature using a diamond anvil cell (DAC). [N1444][NTf2] experiences glass transition at low temperature, whereas [N1114][NTf2] crystallizes or not depending on the cooling rate. Both the ionic liquids exhibit glass transition under high pressure. XRD and low-frequency Raman spectra provide a consistent physical picture of structural ordering-disordering accompanying the thermal events of crystallization, glass transition, cold crystallization, pre-melting, and melting. Raman spectra in the high-frequency range of some specific cation and anion normal modes reveal conformational changes of the molecular structures along phase transitions.

  19. Comparing two tetraalkylammonium ionic liquids. II. Phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Lima, Thamires A.; Paschoal, Vitor H.; Faria, Luiz F. O.; Ribeiro, Mauro C. C., E-mail: mccribei@iq.usp.br [Laboratório de Espectroscopia Molecular, Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, CP 26077, CEP 05513-970 São Paulo, SP (Brazil); Ferreira, Fabio F.; Costa, Fanny N. [Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Santo André, SP (Brazil); Giles, Carlos [Depto. de Física da Matéria Condensada, Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, 13083-859 Campinas, SP (Brazil)

    2016-06-14

    Phase transitions of the ionic liquids n-butyl-trimethylammonium bis(trifluoromethanesulfonyl)imide, [N{sub 1114}][NTf{sub 2}], and methyl-tributylammonium bis(trifluoromethanesulfonyl)imide, [N{sub 1444}][NTf{sub 2}], were investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD) measurements, and Raman spectroscopy. XRD and Raman spectra were obtained as a function of temperature at atmospheric pressure, and also under high pressure at room temperature using a diamond anvil cell (DAC). [N{sub 1444}][NTf{sub 2}] experiences glass transition at low temperature, whereas [N{sub 1114}][NTf{sub 2}] crystallizes or not depending on the cooling rate. Both the ionic liquids exhibit glass transition under high pressure. XRD and low-frequency Raman spectra provide a consistent physical picture of structural ordering-disordering accompanying the thermal events of crystallization, glass transition, cold crystallization, pre-melting, and melting. Raman spectra in the high-frequency range of some specific cation and anion normal modes reveal conformational changes of the molecular structures along phase transitions.

  20. Phase transitions and glass transition in a hyperquenched silica–alumina glass

    DEFF Research Database (Denmark)

    Zhang, Y.F.; Zhao, D.H.; Yue, Yuanzheng

    2017-01-01

    We investigate phase transitions, glass transition, and dynamic behavior in the hyperquenched 69SiO2–31Al2O3 (mol%) glass (SA glass). Upon reheating, the SA glass exhibits a series of thermal responses. Subsequent to the sub-Tg enthalpy release, the glass undergoes a large jump in isobaric heat...... capacity (ΔCp) during glass transition, implying the fragile nature of the SA glass. The mullite starts to form before the end of glass transition, indicating that the SA glass is extremely unstable against crystallization. After the mullite formation, the remaining glass phase exhibits an increased Tg...... and a suppressed ΔCp. The formation of cristobalite at 1553 K indicates the dominance of silica in the remaining glass matrix. The cristobalite gradually re-melts as the isothermal heat-treatment temperature is raised from 1823 to 1853 K, which is well below the melting point of cristobalite, while the amount...

  1. Superfluid Phase Transitions in Dense Neutron Matter

    Energy Technology Data Exchange (ETDEWEB)

    Khodel, V. A.; Clark, J. W.; Zverev, M. V.

    2001-07-16

    The phase transitions in a realistic system with triplet pairing, dense neutron matter, have been investigated. The spectrum of phases of the P{sub 2}{sup 3}- F{sub 2}{sup 3} model, which adequately describes pairing in this system, is analytically constructed with the aid of a separation method for solving BCS gap equations in states of arbitrary angular momentum. In addition to solutions involving a single value of the magnetic quantum number (and its negative), there exist ten real multicomponent solutions. Five of the corresponding angle-dependent order parameters have nodes, and five do not. In contrast to the case of superfluid {sup 3}He , transitions occur between phases with nodeless order parameters.

  2. Scaling of entanglement close to a quantum phase transition.

    Science.gov (United States)

    Osterloh, A; Amico, Luigi; Falci, G; Fazio, Rosario

    2002-04-11

    Classical phase transitions occur when a physical system reaches a state below a critical temperature characterized by macroscopic order. Quantum phase transitions occur at absolute zero; they are induced by the change of an external parameter or coupling constant, and are driven by quantum fluctuations. Examples include transitions in quantum Hall systems, localization in Si-MOSFETs (metal oxide silicon field-effect transistors; ref. 4) and the superconductor-insulator transition in two-dimensional systems. Both classical and quantum critical points are governed by a diverging correlation length, although quantum systems possess additional correlations that do not have a classical counterpart. This phenomenon, known as entanglement, is the resource that enables quantum computation and communication. The role of entanglement at a phase transition is not captured by statistical mechanics-a complete classification of the critical many-body state requires the introduction of concepts from quantum information theory. Here we connect the theory of critical phenomena with quantum information by exploring the entangling resources of a system close to its quantum critical point. We demonstrate, for a class of one-dimensional magnetic systems, that entanglement shows scaling behaviour in the vicinity of the transition point.

  3. Effect of nanoparticles on the RII -RI -RV rotator phase transitions of alkanes

    Science.gov (United States)

    Mukherjee, Prabir K.

    2017-08-01

    Experimental studies have shown that nanoparticles play an important role on the rotator phase transitions of n-alkanes. A phenomenological model for predicting the RII -RI -RV phase transitions in mixtures of alkanes and nanoparticles has been proposed by combining Flory-Huggins free energy of isotropic mixing and Landau free energy. The impact of nanoparticles on the RII -RI -RV phase transitions and their transition temperatures is discussed by means of phenomenological theory. The possibility of the tricritical behavior of the RI -RV phase transition in the mixtures of alkanes and nanoparticles is discussed. The theoretical predictions are in good qualitative agreement with available experimental results.

  4. Space storm as a phase transition

    Science.gov (United States)

    Wanliss, J. A.; Dobias, P.

    2007-04-01

    Fluctuations of the SYM-H index were analyzed for several space storms preceded by more than a week of extremely quiet conditions to establish that there was a rapid and unidirectional change in the Hurst scaling exponent at the time of storm onset. That is, the transition was accompanied by the specific signature of a rapid unidirectional change in the temporal fractal scaling of fluctuations in SYM-H, signaling the formation of a new dynamical phase (or mode) which was considerably more organized than the background state. We compare these results to a model of multifractional Brownian motion and suggest that the relatively sudden change from a less correlated to a more correlated pattern of multiscale fluctuations at storm onset can be characterized in terms of nonequilibrium dynamical phase transitions. The results show that a dynamical transition in solar wind VB is correlated with the storm onset for intense storms, suggesting that the dynamical transition observed in SYM-H is of external solar wind origin, rather than internal magnetospheric origin. However, some results showed a dynamical transition in solar wind scaling exponents not matched by similar transitions in SYM-H. In other instances, we observed some small storms where there was a strong dynamical transition in SYM-H without similar changes in the VB scaling statistics, suggesting that changes were due to internal magnetospheric processes. In summary, the results for intense storms points to the solar wind as being responsible for providing the scale free properties in the SYM-H fluctuations but the evidence for small storms clearly limit the importance of the solar wind fluctuations; their interaction is more complex than simple causality.

  5. Phase transitions in Pareto optimal complex networks.

    Science.gov (United States)

    Seoane, Luís F; Solé, Ricard

    2015-09-01

    The organization of interactions in complex systems can be described by networks connecting different units. These graphs are useful representations of the local and global complexity of the underlying systems. The origin of their topological structure can be diverse, resulting from different mechanisms including multiplicative processes and optimization. In spatial networks or in graphs where cost constraints are at work, as it occurs in a plethora of situations from power grids to the wiring of neurons in the brain, optimization plays an important part in shaping their organization. In this paper we study network designs resulting from a Pareto optimization process, where different simultaneous constraints are the targets of selection. We analyze three variations on a problem, finding phase transitions of different kinds. Distinct phases are associated with different arrangements of the connections, but the need of drastic topological changes does not determine the presence or the nature of the phase transitions encountered. Instead, the functions under optimization do play a determinant role. This reinforces the view that phase transitions do not arise from intrinsic properties of a system alone, but from the interplay of that system with its external constraints.

  6. Entanglement growth during Van der Waals like phase transition

    Science.gov (United States)

    Xu, Hao

    2017-09-01

    We address the problem of describing the coexistence state of two different black holes and Van der Waals like phase transition in Reissner-Nordström-AdS space-time. We start by a small charged black hole, then introduce a collapsing neutral thin-shell described by Vaidya metric to form a large one. The formation of the large black hole does not change the temperature and free energy of the initial state. We discuss the entanglement growing during the phase transition. The transition is always continuous and the saturation time is determined by the final state. It opens a possibility for studying the holography from excited states to excited states.

  7. Negative thermal expansion near two structural quantum phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Occhialini, Connor A.; Handunkanda, Sahan U.; Said, Ayman; Trivedi, Sudhir; Guzmán-Verri, G. G.; Hancock, Jason N.

    2017-12-01

    Recent experimental work has revealed that the unusually strong, isotropic structural negative thermal expansion in cubic perovskite ionic insulator ScF3 occurs in excited states above a ground state tuned very near a structural quantum phase transition, posing a question of fundamental interest as to whether this special circumstance is related to the anomalous behavior. To test this hypothesis, we report an elastic and inelastic x-ray scattering study of a second system Hg2I2 also tuned near a structural quantum phase transition while retaining stoichiometric composition and high crystallinity. We find similar behavior and significant negative thermal expansion below 100 K for dimensions along the body-centered-tetragonal c axis, bolstering the connection between negative thermal expansion and zero-temperature structural transitions.We identify the common traits between these systems and propose a set of materials design principles that can guide discovery of newmaterials exhibiting negative thermal expansion

  8. Phase transitions and domain structures in multiferroics

    Science.gov (United States)

    Vlahos, Eftihia

    2011-12-01

    Thin film ferroelectrics and multiferroics are two important classes of materials interesting both from a scientific and a technological prospective. The volatility of lead and bismuth as well as environmental issues regarding the toxicity of lead are two disadvantages of the most commonly used ferroelectric random access memory (FeRAM) materials such as Pb(Zr,Ti)O3 and SrBi2Ta2O9. Therefore lead-free thin film ferroelectrics are promising substitutes as long as (a) they can be grown on technologically important substrates such as silicon, and (b) their T c and Pr become comparable to that of well established ferroelectrics. On the other hand, the development of functional room temperature ferroelectric ferromagnetic multiferroics could lead to very interesting phenomena such as control of magnetism with electric fields and control of electrical polarization with magnetic fields. This thesis focuses on the understanding of material structure-property relations using nonlinear optical spectroscopy. Nonlinear spectroscopy is an excellent tool for probing the onset of ferroelectricity, and domain dynamics in strained ferroelectrics and multiferroics. Second harmonic generation was used to detect ferroelectricity and the antiferrodistortive phase transition in thin film SrTiO3. Incipient ferroelectric CaTiO3 has been shown to become ferroelectric when strained with a combination of SHG and dielectric measurements. The tensorial nature of the induced nonlinear polarization allows for probing of the BaTiO3 and SrTiO3 polarization contributions in nanoscale BaTiO3/SrTiO3 superlattices. In addition, nonlinear optics was used to demonstrate ferroelectricity in multiferroic EuTiO3. Finally, confocal SHG and Raman microscopy were utilized to visualize polar domains in incipient ferroelectric and ferroelastic CaTiO3.

  9. Phase transitions in hybrid SFS structures with thin superconducting layers

    Science.gov (United States)

    Samokhvalov, A. V.

    2017-11-01

    Calculations of critical temperature T c of the phase transition to superconducting state of a superconductor/ ferromagnet/superconductor (SFS) hybrid structure with proximity effect is performed on the base of linearized Usadel equations. It is shown that the proximity effect between S and F metals and the exchange interaction can induce an inhomogeneous superconducting state with longitudinal to layers Δ ∝ exp( ipz) modulation of the superconductivity order parameter, which is characterized by nonzero value of the wave number p, describing the Larkin-Ovchinnikov-Fulde-Ferrell instability. Influence of this instability on transitions between 0- and π-states of the SFS structure is studied. It is shown that the 0-π transition is accompanied by a nonmonotonic dependence of both the critical temperature T c and the effective penetration depth Λ of the magnetic field into the hybrid structure on the characteristic size of the ferromagnetic region.

  10. Thermalon mediated phase transitions in Gauss-Bonnet gravity

    Energy Technology Data Exchange (ETDEWEB)

    Hennigar, Robie A.; Mann, Robert B.; Mbarek, Saoussen [Department of Physics and Astronomy, University of Waterloo,Waterloo, Ontario, Canada, N2L 3G1 (Canada)

    2016-02-04

    Thermalons can mediate phase transitions between different vacua in higher curvature gravity, potentially changing the asymptotic structure of the spacetime. Treating the cosmological constant as a dynamical parameter, we study these phase transitions in the context of extended thermodynamic phase space. We find that in addition to the AdS to dS phase transitions previously studied, thermal AdS space can undergo a phase transition to an asymptotically flat black hole geometry. In the context of AdS to AdS transitions, we comment on the similarities and differences between thermalon transitions and the Hawking-Page transition.

  11. Influence of pions on the hadron-quark phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Lourenco, O.; Dutra, M.; Frederico, T.; Malheiro, M. [Departamento de Fisica, Instituto Tecnologico de Aeronautica-CTA, 12228-900, Sao Jose dos Campos (Brazil); Delfino, A. [Instituto de Fisica, Universidade Federal Fluminense, Av. Litoranea s/n, 24210-150, Boa Viagem, Niteroi RJ (Brazil)

    2013-05-06

    In this work we present the features of the hadron-quark phase transition diagrams in which the pions are included in the system. To construct such diagrams we use two different models in the description of the hadronic and quark sectors. At the quark level, we consider two distinct parametrizations of the Polyakov-Nambu-Jona-Lasinio (PNJL) models. In the hadronic side, we use a well known relativistic mean-field (RMF) nonlinear Walecka model. We show that the effect of the pions on the hadron-quark phase diagrams is to move the critical end point (CEP) of the transitions lines. Such an effect also depends on the value of the critical temperature (T{sub 0}) in the pure gauge sector used to parametrize the PNJL models. Here we treat the phase transitions using two values for T{sub 0}, namely, T{sub 0}= 270 MeV and T{sub 0}= 190 MeV. The last value is used to reproduce lattice QCD data for the transition temperature at zero chemical potential.

  12. Phase Transition in the Bandwidth Minimization Problem

    Science.gov (United States)

    Rangel-Valdez, Nelson; Torres-Jimenez, Jose

    It is known that some NP-Complete problems exhibit sharp phase transitions with respect to some order parameter. Moreover, a correlation between that critical behavior and the hardness of finding a solution exists in some of these problems. This paper shows experimental evidence about the existence of a critical behavior in the computational cost of solving the bandwidth minimization problem for graphs (BMPG). The experimental design involved the density of a graph as order parameter, 200000 random connected graphs of size 16 to 25 nodes, and a branch and bound algorithm taken from the literature. The results reveal a bimodal phase transition in the computational cost of solving the BMPG instances. This behavior was confirmed with the results obtained by metaheuristics that solve a known BMPG benchmark.

  13. Gravitational Waves from a Dark Phase Transition.

    Science.gov (United States)

    Schwaller, Pedro

    2015-10-30

    In this work, we show that a large class of models with a composite dark sector undergo a strong first order phase transition in the early Universe, which could lead to a detectable gravitational wave signal. We summarize the basic conditions for a strong first order phase transition for SU(N) dark sectors with n_{f} flavors, calculate the gravitational wave spectrum and show that, depending on the dark confinement scale, it can be detected at eLISA or in pulsar timing array experiments. The gravitational wave signal provides a unique test of the gravitational interactions of a dark sector, and we discuss the complementarity with conventional searches for new dark sectors. The discussion includes the twin Higgs and strongly interacting massive particle models as well as symmetric and asymmetric composite dark matter scenarios.

  14. Electroweak monopoles and the electroweak phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Arunasalam, Suntharan; Kobakhidze, Archil [The University of Sydney, ARC Centre of Excellence for Particle Physics at the Terascale, School of Physics, Sydney, NSW (Australia)

    2017-07-15

    We consider an isolated electroweak monopole solution within the Standard Model with a nonlinear Born-Infeld extension of the hypercharge gauge field. Monopole (and dyon) solutions in such an extension are regular and their masses are predicted to be proportional to the Born-Infeld mass parameter. We argue that cosmological production of electroweak monopoles may delay the electroweak phase transition and make it more strongly first order for monopole masses M >or similar 9.3 . 10{sup 3} TeV, while the nucleosynthesis constraints on the abundance of relic monopoles impose the bound M phase transition. (orig.)

  15. Status of electroweak phase transition and baryogenesis

    Indian Academy of Sciences (India)

    SUSY breaking. (gaugino)2 ? 100 GeV. Electroweak: SU(2)¢U(1) U(1)em. SM Higgs. 100 MeV. QCD chiral phase transition. nqДqК this negative conclusion by ... А, and perturbation theory breaks down for heavy Higgs bosons, ..... and S is a CP-violating source term arising from the force on the particles or from quantum.

  16. Ferroelectric Phase Transitions from First Principles

    CERN Document Server

    Rabe, K M

    1995-01-01

    An effective Hamiltonian for the ferroelectric transition in $PbTiO_3$ is constructed from first-principles density-functional-theory total-energy and linear-response calculations through the use of a localized, symmetrized basis set of ``lattice Wannier functions.'' Preliminary results of Monte Carlo simulations for this system show a first-order cubic-tetragonal transition at 660 K. The involvement of the Pb atom in the lattice instability and the coupling of local distortions to strain are found to be particularly important in producing the behavior characteristic of the $PbTiO_3$ transition. A tentative explanation for the presence of local distortions experimentally observed above $T_c$ is suggested. Further applications of this method to a variety of systems and structures are proposed for first-principles study of finite-temperature structural properties in individual materials.

  17. Highly tilted liquid crystalline materials possessing a direct phase transition from antiferroelectric to isotropic phase

    Energy Technology Data Exchange (ETDEWEB)

    Milewska, K.; Drzewiński, W. [Institute of Chemistry, Military University of Technology, 00-908 Warsaw (Poland); Czerwiński, M., E-mail: mczerwinski@wat.edu.pl [Institute of Chemistry, Military University of Technology, 00-908 Warsaw (Poland); Dąbrowski, R. [Institute of Chemistry, Military University of Technology, 00-908 Warsaw (Poland); Piecek, W. [Institute of Applied Physics, Military University of Technology, 00-908 Warsaw (Poland)

    2016-03-01

    Pure compounds and multicomponent mixtures with a broad temperature range of high tilted liquid crystalline antiferroelectric phase and a direct phase transition from antiferroelectric to isotropic phase, were obtained. X-ray diffraction analysis confirms these kinds of materials form a high tilted anticlinic phase, with a fixed layer spacing and very weak dependency upon temperature, after the transition from the isotropic phase. Due to this, not only pure orthoconic antiferroelectric liquid crystals but also those with a moderate tilt should generate a good dark state. Furthermore, due to the increased potential for forming anticlinic forces, such materials could minimize a commonly observed asymmetry of a rise and fall switching times at a surface stabilized geometry. - Highlights: • The new class of liquid crystalline materials with the direct SmC{sub A}*. • Iso phase transition were obtained. • Materials possess the layer spacing fixed and very weak dependent upon temperature. • Smectic layers without shrinkage are observed. • A good dark state can be generate in SSAFLC.

  18. Geometric Phase and Quantum Phase Transition in the Lipkin-Meshkov-Glick model

    OpenAIRE

    Cui, H. T.; Li, K.; Yi, X. X.

    2006-01-01

    The relation between the geometric phase and quantum phase transition has been discussed in the Lipkin-Meshkov-Glick model. Our calculation shows the ability of geometric phase of the ground state to mark quantum phase transition in this model. The possibility of the geometric phase or its derivatives as the universal order parameter of characterizing quantum phase transitions has been also discussed.

  19. Size dependence of phase transitions in aerosol nanoparticles

    Science.gov (United States)

    Cheng, Yafang; Su, Hang; Koop, Thomas; Mikhailov, Eugene; Pöschl, Ulrich

    2015-04-01

    Phase transitions of nanoparticles are of fundamental importance in atmospheric sciences. Current understanding is insufficient to explain observations at the nano-scale. In particular, discrepancies exist between observations and model predictions of deliquescence and efflorescence transitions and the hygroscopic growth of salt nanoparticles. Here we show that these discrepancies can be resolved by consideration of particle size effects with consistent thermodynamic data. We present a new method for the determination of water and solute activities and interfacial energies in highly supersaturated aqueous solution droplets. Our analysis reveals that particle size can strongly alter the characteristic concentration of phase separation in mixed systems, resembling the influence of temperature. Due to similar effects, atmospheric secondary organic aerosol particles at room temperature are expected to be always liquid at diameters below ~20 nm. We thus propose and demonstrate that particle size should be included as an additional dimension in the equilibrium phase diagram of aerosol nanoparticles. Reference: Cheng, Y. et al. Size dependence of phase transitions in aerosol nanoparticles. Nature Communications. 5:5923 doi: 10.1038/ncomms6850 (2015).

  20. Generalized simulated tempering for exploring strong phase transitions.

    Science.gov (United States)

    Kim, Jaegil; Straub, John E

    2010-10-21

    An extension of the simulation tempering algorithm is proposed. It is shown to be particularly suited to the exploration of first-order phase transition systems characterized by the backbending or S-loop in the statistical temperature or a microcanonical caloric curve. A guided Markov process in an auxiliary parameter space systematically combines a set of parametrized Tsallis-weight ensemble simulations, which are targeted to transform unstable or metastable energy states of canonical ensembles into stable ones and smoothly join ordered and disordered phases across phase transition regions via a succession of unimodal energy distributions. The inverse mapping between the sampling weight and the effective temperature enables an optimal selection of relevant Tsallis-weight parameters. A semianalytic expression for the biasing weight in parameter space is adaptively updated "on the fly" during the simulation to achieve rapid convergence. Accelerated tunneling transitions with a comprehensive sampling for phase-coexistent states are explicitly demonstrated in systems subject to strong hysteresis including Potts and Ising spin models and a 147 atom Lennard-Jones cluster.

  1. Windows open for highly tunable magnetostructural phase transitions

    KAUST Repository

    Li, Y.

    2016-07-18

    An attempt was made to tailor the magnetostructural transitions over a wide temperature range under the principle of isostructural alloying. A series of wide Curie-temperature windows (CTWs) with a maximal width of 377 K between 69 and 446 K were established in the Mn1− yCoyNiGe1− xSix system. Throughout the CTWs, the magnetic-field-induced metamagnetic behavior and giant magnetocaloric effects are obtained. The (Mn,Co)Ni(Ge,Si) system shows great potential as multifunctional phase-transition materials that work in a wide range covering liquid-nitrogen and above water-boiling temperatures. Moreover, general understanding of isostructural alloying and CTWs constructed in (Mn,Co)Ni(Ge,Si) as well as (Mn,Fe)Ni(Ge,Si) is provided.

  2. Phase Transitions in Model Active Systems

    Science.gov (United States)

    Redner, Gabriel S.

    The amazing collective behaviors of active systems such as bird flocks, schools of fish, and colonies of microorganisms have long amazed scientists and laypeople alike. Understanding the physics of such systems is challenging due to their far-from-equilibrium dynamics, as well as the extreme diversity in their ingredients, relevant time- and length-scales, and emergent phenomenology. To make progress, one can categorize active systems by the symmetries of their constituent particles, as well as how activity is expressed. In this work, we examine two categories of active systems, and explore their phase behavior in detail. First, we study systems of self-propelled spherical particles moving in two dimensions. Despite the absence of an aligning interaction, this system displays complex emergent dynamics, including phase separation into a dense active solid and dilute gas. Using simulations and analytic modeling, we quantify the phase diagram and separation kinetics. We show that this nonequilibrium phase transition is analogous to an equilibrium vapor-liquid system, with binodal and spinodal curves and a critical point. We also characterize the dense active solid phase, a unique material which exhibits the structural signatures of a crystalline solid near the crystal-hexatic transition point, as well as anomalous dynamics including superdiffusive motion on intermediate timescales. We also explore the role of interparticle attraction in this system. We demonstrate that attraction drastically changes the phase diagram, which contains two distinct phase-separated regions and is reentrant as a function of propulsion speed. We interpret this complex situation with a simple kinetic model, which builds from the observed microdynamics of individual particles to a full description of the macroscopic phase behavior. We also study active nematics, liquid crystals driven out of equilibrium by energy-dissipating active stresses. The equilibrium nematic state is unstable in these

  3. Nonlinear clustering during the BEC dark matter phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Freitas, Rodolfo C. de, E-mail: rodolfo.camargo@pq.cnpq.br [Universidade Federal do Espírito Santo, Av. Fernando Ferrari, Goiabeiras, Vitória (Brazil); Instituto Federal de Educação, Ciência e Tecnologia do Espírito Santo, Avenida Vitória 1729, Jucutuquara, Vitória (Brazil); Velten, Hermano, E-mail: velten@pq.cnpq.br [Universidade Federal do Espírito Santo, Av. Fernando Ferrari, Goiabeiras, Vitória (Brazil); UMR 7332, CPT, Aix Marseille Université, 13288, Marseille (France)

    2015-12-16

    Spherical collapse of the Bose–Einstein condensate (BEC) dark matter model is studied in the Thomas–Fermi approximation. The evolution of the overdensity of the collapsed region and its expansion rate are calculated for two scenarios. We consider the case of a sharp phase transition (which happens when the critical temperature is reached) from the normal dark matter state to the condensate one and the case of a smooth first order phase transition where there is a continuous conversion of “normal” dark matter to the BEC phase. We present numerical results for the physics of the collapse for a wide range of the model’s space parameter, i.e. the mass of the scalar particle m{sub χ} and the scattering length l{sub s}. We show the dependence of the transition redshift on m{sub χ} and l{sub s}. Since small scales collapse earlier and eventually before the BEC phase transition, the evolution of collapsing halos in this limit is indeed the same in both the CDM and the BEC models. Differences are expected to appear only on the largest astrophysical scales. However, we argue that the BEC model is almost indistinguishable from the usual dark matter scenario concerning the evolution of nonlinear perturbations above typical clusters scales, i.e., ≳10{sup 14}M{sub ⊙}. This provides an analytical confirmation for recent results from cosmological numerical simulations (Schive et al., Nat Phys 10:496, 2014)

  4. Compact Stars with Sequential QCD Phase Transitions.

    Science.gov (United States)

    Alford, Mark; Sedrakian, Armen

    2017-10-20

    Compact stars may contain quark matter in their interiors at densities exceeding several times the nuclear saturation density. We explore models of such compact stars where there are two first-order phase transitions: the first from nuclear matter to a quark-matter phase, followed at a higher density by another first-order transition to a different quark-matter phase [e.g., from the two-flavor color-superconducting (2SC) to the color-flavor-locked (CFL) phase]. We show that this can give rise to two separate branches of hybrid stars, separated from each other and from the nuclear branch by instability regions, and, therefore, to a new family of compact stars, denser than the ordinary hybrid stars. In a range of parameters, one may obtain twin hybrid stars (hybrid stars with the same masses but different radii) and even triplets where three stars, with inner cores of nuclear matter, 2SC matter, and CFL matter, respectively, all have the same mass but different radii.

  5. Berni Alder and Phase Transitions in Two Dimensions

    Science.gov (United States)

    Kosterlitz, J. Michael

    I do not know Berni Alder as a person, but I feel that I know him well through his seminal paper "Phase Transition in Elastic Disks𠇍 by B. J. Alder and T. E. Wainwright [1962], which was essential in motivating David Thouless and myself to think about phase transitions in two dimensional systems with a continuous symmetry. In the early 1970's, the conventional wisdom was that a crystalline solid could not exist in a two dimensional world because of the rigorous Mermin-Wagner theorem prohibiting true long range translational order at any non-zero temperature. This contradiction was settled by the theory of dislocation mediated melting to an intermediate hexatic phase followed by a second transition to the isotropic fluid at a higher temperature. This scenario, with its associated sophisticated theory, seemed to settle the controversy of two dimensional melting once and for all. However, in our elation at understanding the fundamental physics and the essential excitations of melting in 2D, we had all forgotten that the early work of Berni Alder also showed that this melting involved a weak first order transition while theory now predicted melting by two successive continuous transitions with no discontinuity in area at the critical pressure. This discrepancy could be hand waved away by arguing that Berni's system was far too small and his computers far too slow so that the areal discontinuity could be due to finite size effects or to failing to equilibrate the system. Experiments were not able to resolve the order of the transitions, but seemed to agree quantitatively with theory…

  6. Neutron-Diffraction Study of the Phase Transition in Stannous Chloride Dihydrate

    DEFF Research Database (Denmark)

    Youngblood, R.; Kjems, Jørgen

    1979-01-01

    of the system does not change. We present neutron-diffraction results which show that the temperature dependence of the hydrogen-site occupancies is also highly symmetric around the phase-transition temperature. These results are discussed in terms of a lattice statistical model which was proposed and solved......The order-disorder phase transition in two-dimensional hydrogen-bonded layers of water molecules in SnCl2·2D2O is remarkable in several respects. It has been shown that the peak in the specific heat is highly symmetric around the phase-transition temperature, and that the crystallographic symmetry...

  7. Phase transitions in A 4 Li (HSO 4) 3 (SO 4); A= Rb, K: Single crystal ...

    Indian Academy of Sciences (India)

    Keywords. Phase transition; ferroelastic; cryo-crystallography; crystal structure. Abstract. The crystal structure of ferroelastic Rb4Li(HSO4)3(SO4) has been determined at two temperatures, which indicates a structural phase transition, tetragonal 43 with = 7.629(1) Å, = 29.497(2) Å at 293 K and monoclinic 21 with  ...

  8. Dynamics of Subcritical Bubbles in First Order Phase Transition

    Science.gov (United States)

    Shiromizu, T.; Morikawa, M.; Yokoyama, J.

    1995-11-01

    We derivate the Langevin and the Fokker-Planck equations for the radius of O(3)-symmetric subcritical bubbles as a phenomenological model to treat thermal fluctuation. The effect of thermal noise on subcritical bubbles is examined. We find that the fluctuation-dissipation relation holds and that in the high temperature phase the system settles down rapidly to the thermal equilibrium state even if it was in a nonequilibrium state initially. We then estimate the typical size of subcritical bubbles as well as the amplitude of fluctuations on that scale. We also discuss their implication to the electroweak phase transition.

  9. Pressure-induced phase transition in GaN nanocrystals

    CERN Document Server

    Cui, Q; Zhang, W; Wang, X; Zhang, J; Cui, T; Xie, Y; Liu, J; Zou, G

    2002-01-01

    High-pressure in situ energy-dispersive x-ray diffraction experiments on GaN nanocrystals with 50 nm diameter have been carried out using a synchrotron x-ray source and a diamond-anvil cell up to about 79 GPa at room temperature. A pressure-induced first-order structural phase transition from the wurtzite-type structure to the rock-salt-type structure starts at about 48.8 GPa. The rock-salt-type phase persists to the highest pressure in our experimental range.

  10. An x-ray powder diffraction study of the high temperature phase transitions in {alpha}-quartz-type AlPO{sub 4}-GaPO{sub 4} solid solutions

    Energy Technology Data Exchange (ETDEWEB)

    Haines, J [Laboratoire de Physicochimie de la Matiere Condensee, UMR CNRS 5617, Universite Montpellier II, cc 003, Place E Bataillon, F-34095 Montpellier, Cedex 5 (France); Cambon, O [Laboratoire de Physicochimie de la Matiere Condensee, UMR CNRS 5617, Universite Montpellier II, cc 003, Place E Bataillon, F-34095 Montpellier, Cedex 5 (France); Fraysse, G [Laboratoire de Physicochimie de la Matiere Condensee, UMR CNRS 5617, Universite Montpellier II, cc 003, Place E Bataillon, F-34095 Montpellier, Cedex 5 (France); Lee, A van der [Institut Europeen des Membranes de Montpellier, UMR-CNRS 5635, Universite Montpellier II, cc 047, 300 Avenue Prof. E Jeanbrau, F-34095 Montpellier, Cedex 5 (France)

    2005-07-20

    Al{sub 1-x}Ga{sub x}PO{sub 4} solid solutions (x = 0.3, 0.7) with the {alpha}-quartz-type structure were investigated up to 1208 K by x-ray powder diffraction. The composition Al{sub 0.7}Ga{sub 0.3}PO{sub 4} exhibits almost simultaneous transitions to the {beta}-quartz and {beta}-cristobalite forms at close to 1050 K. The tendency towards the {beta}-quartz type structure is found to be much less marked for the Ga-rich composition (x = 0.7) based on the temperature dependence of the cell parameters, molar volume, fractional atomic coordinates and tetrahedral tilt angle. Direct transformation to the {beta}-cristobalite form begins close to 1123 K. The {beta}-quartz form exists as a stable phase only for values below x = 0.3.

  11. Phase transitions in shocked porous quartz

    Science.gov (United States)

    Akin, M. C.; Crum, R. S.; Lind, J.; Pagan, D. C.; Homel, M. A.; Hurley, R. C.; Herbold, E. B.

    2017-06-01

    The presence of porosity in granular media provides the means to probe regions of the phase diagram that do not coincide with the principal Hugoniot. In particular, the potential for increased heating is likely to lead to observable changes in phase boundaries. 55% dense quartz and forsterite were prepared by tap filling. These samples were shock compressed using the two stage light gas gun at DCS-APS to examine the impact of the increased porosity on the phase boundary. Here we discuss the observed changes to phase in quartz and forsterite compared to the fully dense materials, the effects of porosity upon compaction and phase transitions, and the implications for constructing the phase diagram. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Work was supported by LLNL's LDRD program under Grant 16-ERD-010. The Dynamic Compression Sector (35) is supported by Department of Energy / National Nuclear Security Administration under Award Number DE-NA0002442. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.

  12. String theory, quantum phase transitions, and the emergent Fermi liquid.

    Science.gov (United States)

    Cubrović, Mihailo; Zaanen, Jan; Schalm, Koenraad

    2009-07-24

    A central problem in quantum condensed matter physics is the critical theory governing the zero-temperature quantum phase transition between strongly renormalized Fermi liquids as found in heavy fermion intermetallics and possibly in high-critical temperature superconductors. We found that the mathematics of string theory is capable of describing such fermionic quantum critical states. Using the anti-de Sitter/conformal field theory correspondence to relate fermionic quantum critical fields to a gravitational problem, we computed the spectral functions of fermions in the field theory. By increasing the fermion density away from the relativistic quantum critical point, a state emerges with all the features of the Fermi liquid.

  13. A high-temperature Raman scattering study of the phase transitions in GaPO{sub 4} and in the AlPO{sub 4}-GaPO{sub 4} system

    Energy Technology Data Exchange (ETDEWEB)

    Angot, E [Laboratoire des Colloides, des Verres et des Nanomateriaux, UMR CNRS 5587, Universite Montpellier II, cc026, Place E Bataillon, F-34095 Montpellier Cedex 5 (France); Parc, R Le [Laboratoire des Colloides, des Verres et des Nanomateriaux, UMR CNRS 5587, Universite Montpellier II, cc026, Place E Bataillon, F-34095 Montpellier Cedex 5 (France); Levelut, C [Laboratoire des Colloides, des Verres et des Nanomateriaux, UMR CNRS 5587, Universite Montpellier II, cc026, Place E Bataillon, F-34095 Montpellier Cedex 5 (France); Beaurain, M [Laboratoire de Physicochimie de la Matiere Condensee, UMR CNRS 5617, Universite Montpellier II, cc003, Place E Bataillon, F-34095 Montpellier Cedex 5 (France); Armand, P [Laboratoire de Physicochimie de la Matiere Condensee, UMR CNRS 5617, Universite Montpellier II, cc003, Place E Bataillon, F-34095 Montpellier Cedex 5 (France); Cambon, O [Laboratoire de Physicochimie de la Matiere Condensee, UMR CNRS 5617, Universite Montpellier II, cc003, Place E Bataillon, F-34095 Montpellier Cedex 5 (France); Haines, J [Laboratoire de Physicochimie de la Matiere Condensee, UMR CNRS 5617, Universite Montpellier II, cc003, Place E Bataillon, F-34095 Montpellier Cedex 5 (France)

    2006-05-03

    Al{sub 1-x}Ga{sub x}PO{sub 4} solid solutions (x = 0.2, 0.3, 0.38, 0.7) and the pure AlPO{sub 4} (x = 0) and GaPO{sub 4} (x = 1) end members with the {alpha}-quartz-type structure were studied by Raman scattering. An investigation as a function of composition enabled the various modes to be assigned, in particular coupled and decoupled vibrations. The tetrahedral tilting modes, which have been linked to high-temperature phase transitions to {beta}-quartz-type forms, were found to be decoupled. In addition, it is shown that Raman spectroscopy is a powerful technique for determining the gallium content of these solid solutions. Single crystals with x = 0.2, 0.38, and 1.0 (GaPO{sub 4}) were investigated at high temperature. The composition Al{sub 0.8}Ga{sub 0.2}PO{sub 4} was found to exhibit sequential transitions upon heating to the {beta}-quartz and {beta}-cristobalite forms at close to 993 K and 1073 K, respectively. Direct {alpha}-quartz-{beta}-cristobalite transitions were observed for the two other compositions at close to 1083 K and 1253 K, respectively, upon heating. The spectra of the {beta}-quartz and {beta}-cristobalite forms indicate the presence of significant disorder. Back transformation to the {alpha}-quartz-type form occurred readily with a hysteresis of less than 100 K for the composition x = 0.38 and for pure GaPO{sub 4}. Rapid cooling was necessary to obtain the metastable {alpha}-cristobalite form. In contrast, for Al{sub 0.80}Ga{sub 0.20}PO{sub 4}, the {alpha}-cristobalite form was obtained even upon slow cooling.

  14. Casimir amplitudes in topological quantum phase transitions

    Science.gov (United States)

    Griffith, M. A.; Continentino, M. A.

    2018-01-01

    Topological phase transitions constitute a new class of quantum critical phenomena. They cannot be described within the usual framework of the Landau theory since, in general, the different phases cannot be distinguished by an order parameter, neither can they be related to different symmetries. In most cases, however, one can identify a diverging length at these topological transitions. This allows us to describe them using a scaling approach and to introduce a set of critical exponents that characterize their universality class. Here we consider some relevant models of quantum topological transitions associated with well-defined critical exponents that are related by a quantum hyperscaling relation. We extend to these models a finite-size scaling approach based on techniques for calculating the Casimir force in electromagnetism. This procedure allows us to obtain universal Casimir amplitudes at their quantum critical points. Our results verify the validity of finite-size scaling in these systems and confirm the values of the critical exponents obtained previously.

  15. Communication: Protein dynamical transition vs. liquid-liquid phase transition in protein hydration water

    Science.gov (United States)

    Schirò, Giorgio; Fomina, Margarita; Cupane, Antonio

    2013-09-01

    In this work, we compare experimental data on myoglobin hydrated powders from elastic neutron scattering, broadband dielectric spectroscopy, and differential scanning calorimetry. Our aim is to obtain new insights on the connection between the protein dynamical transition, a fundamental phenomenon observed in proteins whose physical origin is highly debated, and the liquid-liquid phase transition (LLPT) possibly occurring in protein hydration water and related to the existence of a low temperature critical point in supercooled water. Our results provide a consistent thermodynamic/dynamic description which gives experimental support to the LLPT hypothesis and further reveals how fundamental properties of water and proteins are tightly related.

  16. Monolayer of the 5 d transition metal trichloride OsCl3: A playground for two-dimensional magnetism, room-temperature quantum anomalous Hall effect, and topological phase transitions

    Science.gov (United States)

    Sheng, Xian-Lei; Nikolić, Branislav K.

    2017-05-01

    Based on density functional theory (DFT) calculations, we predict that a monolayer of OsCl3 (which is a layered material whose interlayer coupling is weaker than in graphite) possesses a quantum anomalous Hall (QAH) insulating phase generated by the combination of honeycomb lattice of osmium atoms, their strong spin-orbit coupling (SOC), and ferromagnetic ground state with in-plane easy axis. The band gap opened by SOC is Eg≃67 meV (or ≃191 meV if the easy axis can be tilted out of the plane by an external electric field), and the estimated Curie temperature of such an anisotropic planar rotator ferromagnet is TC≲350 K. The Chern number C =-1 , generated by the manifold of Os t2 g bands crossing the Fermi energy, signifies the presence of a single chiral edge state in nanoribbons of finite width, where we further show that edge states are spatially narrower for zigzag than armchair edges and investigate edge-state transport in the presence of vacancies at Os sites. Since 5 d electrons of Os exhibit both strong SOC and moderate correlation effects, we employ DFT+U calculations to show how increasing on-site Coulomb repulsion U : gradually reduces Eg while maintaining C =-1 for 0 insulating phase with C =0 for U >Uc .

  17. Scale invariance from phase transitions to turbulence

    CERN Document Server

    Lesne, Annick

    2012-01-01

    During a century, from the Van der Waals mean field description (1874) of gases to the introduction of renormalization group (RG techniques 1970), thermodynamics and statistical physics were just unable to account for the incredible universality which was observed in numerous critical phenomena. The great success of RG techniques is not only to solve perfectly this challenge of critical behaviour in thermal transitions but to introduce extremely useful tools in a wide field of daily situations where a system exhibits scale invariance. The introduction of scaling, scale invariance and universality concepts has been a significant turn in modern physics and more generally in natural sciences. Since then, a new "physics of scaling laws and critical exponents", rooted in scaling approaches, allows quantitative descriptions of numerous phenomena, ranging from phase transitions to earthquakes, polymer conformations, heartbeat rhythm, diffusion, interface growth and roughening, DNA sequence, dynamical systems, chaos ...

  18. The transition to chaotic phase synchronization

    DEFF Research Database (Denmark)

    Mosekilde, E.; Laugesen, J. L.; Zhusubaliyev, Zh. T.

    2012-01-01

    The transition to chaotic phase synchronization for a periodically driven spiral-type chaotic oscillator is known to involve a dense set of saddle-node bifurcations. By following the synchronization transition through the cascade of period-doubling bifurcations in a forced Ro¨ssler system......, this paper describes how these saddle-node bifurcations arise and how their characteristic cyclic organisation develops. We identify the cycles that are involved in the various saddle-node bifurcations and describe how the formation of multi-layered resonance cycles in the synchronization domain is related...... to the torus doubling bifurcations that take place outside this domain. By examining a physiology-based model of the blood flow regulation to the individual functional unit (nephron) of the kidney we demonstrate how a similar bifurcation structure may arise in this system as a response to a periodically...

  19. Isotropic to smectic A phase transitions in a porous matrix a case of multiporous phase coexistence

    CERN Document Server

    Bellini, T; Link, D R

    2003-01-01

    The one-dimensional smectic ordering of the liquid crystal 10CB incorporated in the pores of a silica aerogel has been investigated via x-ray scattering. Although the smectic order is made short-ranged by the aerogel host and the amplitude of the associated Bragg-like peak grows continuously with decreasing temperature, part of the first-order character of the 10CB's direct isotropic-smectic phase transition is retained in the discontinuous temperature dependence of the smectic correlation length. This behaviour contrasts with that of materials where the smectic phase develops from a locally orientationally ordered nematic and can be interpreted as a nucleation-type process.

  20. Label-free direct visual analysis of hydrolytic enzyme activity using aqueous two-phase system droplet phase transitions.

    Science.gov (United States)

    Lai, David; Frampton, John P; Tsuei, Michael; Kao, Albert; Takayama, Shuichi

    2014-04-15

    Dextran hydrolysis-mediated conversion of polyethylene glycol (PEG)-dextran (DEX) aqueous two-phase system droplets to a single phase was used to directly visualize Dextranase activity. DEX droplets were formed either by manual micropipetting or within a continuous PEG phase by computer controlled actuation of an orifice connecting rounded channels formed by backside diffused light lithography. The time required for the two-phase to one-phase transition was dependent on the Dextranase concentration, pH of the medium, and temperature. The apparent Michaelis constants for Dextranase were estimated based on previously reported catalytic constants, the binodal polymer concentration curves for PEG-DEX phase transition for each temperature, and pH condition. The combination of a microfluidic droplet system and phase transition observation provides a new method for label-free direct measurement of enzyme activity.

  1. Pressure induced structural phase transition in IB transition metal nitrides compounds

    Energy Technology Data Exchange (ETDEWEB)

    Soni, Shubhangi; Kaurav, Netram, E-mail: netramkaurav@yahoo.co.uk; Jain, A. [Department of Physics, Govt. Holkar Science college, A. B. Road, Indore-452001 India (India); Shah, S. [Department of Physics, P. M. B. Gujarati Science College, Indore-452001 (India); Choudhary, K. K. [Department of Physics, National Defence Academy, Khadakwasla, Pune-411 0231 India (India)

    2015-06-24

    Transition metal mononitrides are known as refractory compounds, and they have, relatively, high hardness, brittleness, melting point, and superconducting transition temperature, and they also have interesting optical, electronic, catalytic, and magnetic properties. Evolution of structural properties would be an important step towards realizing the potential technological scenario of this material of class. In the present study, an effective interionic interaction potential (EIOP) is developed to investigate the pressure induced phase transitions in IB transition metal nitrides TMN [TM = Cu, Ag, and Au] compounds. The long range Coulomb, van der Waals (vdW) interaction and the short-range repulsive interaction upto second-neighbor ions within the Hafemeister and Flygare approach with modified ionic charge are properly incorporated in the EIOP. The vdW coefficients are computed following the Slater-Kirkwood variational method, as both the ions are polarizable. The estimated value of the phase transition pressure (Pt) and the magnitude of the discontinuity in volume at the transition pressure are consistent as compared to the reported data.

  2. Phases and phase transitions in the algebraic microscopic shell model

    Directory of Open Access Journals (Sweden)

    Georgieva A. I.

    2016-01-01

    Full Text Available We explore the dynamical symmetries of the shell model number conserving algebra, which define three types of pairing and quadrupole phases, with the aim to obtain the prevailing phase or phase transition for the real nuclear systems in a single shell. This is achieved by establishing a correspondence between each of the pairing bases with the Elliott’s SU(3 basis that describes collective rotation of nuclear systems. This allows for a complete classification of the basis states of different number of particles in all the limiting cases. The probability distribution of the SU(3 basis states within theirs corresponding pairing states is also obtained. The relative strengths of dynamically symmetric quadrupole-quadrupole interaction in respect to the isoscalar, isovector and total pairing interactions define a control parameter, which estimates the importance of each term of the Hamiltonian in the correct reproduction of the experimental data for the considered nuclei.

  3. Swarms, phase transitions, and collective intelligence

    Energy Technology Data Exchange (ETDEWEB)

    Millonas, M.M. [Texas Univ., Austin, TX (United States). Dept. of Physics

    1992-12-31

    A model of the collective behavior of a large number of locally acting organisms is proposed. The model is intended to be realistic, but turns out to fit naturally into the category of connectionist models, Like all connectionist models, its properties can be divided into the categories of structure, dynamics, and learning. The space in which the organisms move is discretized, and is modeled by a lattice of nodes, or cells. Each cell hag a specified volume, and is connected to other cells in the space in a definite way. Organisms move probabilistically between local cells in this space, but with weights dependent on local morphogenic substances, or morphogens. The morphogens are in turn are effected by the passage of an organism. The evolution of the morphogens, and the corresponding constitutes of the organisms constitutes the collective behavior of the group. The generic properties of such systems are analyzed, and a number of results are obtained. The model has various types of phase transitions and self-organizing properties controlled both by the level of the noise, and other parameters. It is hoped that the present mode; might serve as a paradigmatic example of a complex cooperative system in nature. In particular this model can be used to explore the relation of phase transitions to at least three important issues encountered in artificial life. Firstly, that of emergence as complex adaptive behavior. Secondly, as an exploration of second order phase transitions in biological systems. Lastly, to derive behavioral criteria for the evolution of collective behavior in social organisms. The model is then applied to the specific case of ants moving on a lattice. The local behavior of the ants is inspired by the actual behavior observed in the laboratory, and analytic results for the collective behavior are compared to the corresponding laboratory results. Monte carlo simulations are used as illustrations.

  4. Swarms, phase transitions, and collective intelligence

    Energy Technology Data Exchange (ETDEWEB)

    Millonas, M.M. (Texas Univ., Austin, TX (United States). Dept. of Physics)

    1992-01-01

    A model of the collective behavior of a large number of locally acting organisms is proposed. The model is intended to be realistic, but turns out to fit naturally into the category of connectionist models, Like all connectionist models, its properties can be divided into the categories of structure, dynamics, and learning. The space in which the organisms move is discretized, and is modeled by a lattice of nodes, or cells. Each cell hag a specified volume, and is connected to other cells in the space in a definite way. Organisms move probabilistically between local cells in this space, but with weights dependent on local morphogenic substances, or morphogens. The morphogens are in turn are effected by the passage of an organism. The evolution of the morphogens, and the corresponding constitutes of the organisms constitutes the collective behavior of the group. The generic properties of such systems are analyzed, and a number of results are obtained. The model has various types of phase transitions and self-organizing properties controlled both by the level of the noise, and other parameters. It is hoped that the present mode; might serve as a paradigmatic example of a complex cooperative system in nature. In particular this model can be used to explore the relation of phase transitions to at least three important issues encountered in artificial life. Firstly, that of emergence as complex adaptive behavior. Secondly, as an exploration of second order phase transitions in biological systems. Lastly, to derive behavioral criteria for the evolution of collective behavior in social organisms. The model is then applied to the specific case of ants moving on a lattice. The local behavior of the ants is inspired by the actual behavior observed in the laboratory, and analytic results for the collective behavior are compared to the corresponding laboratory results. Monte carlo simulations are used as illustrations.

  5. Thermal phase transition with full 2-loop effective potential

    Science.gov (United States)

    Laine, M.; Meyer, M.; Nardini, G.

    2017-07-01

    Theories with extended Higgs sectors constructed in view of cosmological ramifications (gravitational wave signal, baryogenesis, dark matter) are often faced with conflicting requirements for their couplings; in particular those influencing the strength of a phase transition may be large. Large couplings compromise perturbative studies, as well as the high-temperature expansion that is invoked in dimensionally reduced lattice investigations. With the example of the inert doublet extension of the Standard Model (IDM), we show how a resummed 2-loop effective potential can be computed without a high-T expansion, and use the result to scrutinize its accuracy. With the exception of Tc, which is sensitive to contributions from heavy modes, the high-T expansion is found to perform well. 2-loop corrections weaken the transition in IDM, but they are moderate, whereby a strong transition remains an option.

  6. Thermal phase transition with full 2-loop effective potential

    Directory of Open Access Journals (Sweden)

    M. Laine

    2017-07-01

    Full Text Available Theories with extended Higgs sectors constructed in view of cosmological ramifications (gravitational wave signal, baryogenesis, dark matter are often faced with conflicting requirements for their couplings; in particular those influencing the strength of a phase transition may be large. Large couplings compromise perturbative studies, as well as the high-temperature expansion that is invoked in dimensionally reduced lattice investigations. With the example of the inert doublet extension of the Standard Model (IDM, we show how a resummed 2-loop effective potential can be computed without a high-T expansion, and use the result to scrutinize its accuracy. With the exception of Tc, which is sensitive to contributions from heavy modes, the high-T expansion is found to perform well. 2-loop corrections weaken the transition in IDM, but they are moderate, whereby a strong transition remains an option.

  7. Superconducting transition temperature of aluminum fine particles

    Energy Technology Data Exchange (ETDEWEB)

    Ohshima, K.; Kuroishi, T.; Fujita, T.

    1976-10-01

    The superconducting transition temperature T/sub C/ of films of aluminium fine particles deposited by gas evaporation method was determined by measuring D.C. electrical resistance. The observed values of T/sub C/ were distributed from 1.5 to 2.5K, about 5/4 = 2 times of that of bulk metal, for the samples of average particle diameter 150 = 50 A. The observed enhancement of T/sub C/ was not explained by the surface softening of the particles only.

  8. Phase transitions in de Sitter space

    Directory of Open Access Journals (Sweden)

    Alexander Vilenkin

    1983-10-01

    Full Text Available An effective potential in de Sitter space is calculated for a model of two interacting scalar fields in one-loop approximation and in a self-consistent approximation which takes into account an infinite set of diagrams. Various approaches to renormalization in de Sitter space are discussed. The results are applied to analyze the phase transition in the Hawking-Moss version of the inflationary universe scenario. Requiring that inflation is sufficiently large, we derive constraints on the parameters of the model.

  9. Traders' behavioral coupling and market phase transition

    Science.gov (United States)

    Ma, Rong; Zhang, Yin; Li, Honggang

    2017-11-01

    Traditional economic theory is based on the assumption that traders are completely independent and rational; however, trading behavior in the real market is often coupled by various factors. This paper discusses behavioral coupling based on the stock index in the stock market, focusing on the convergence of traders' behavior, its effect on the correlation of stock returns and market volatility. We find that the behavioral consensus in the stock market, the correlation degree of stock returns, and the market volatility all exhibit significant phase transitions with stronger coupling.

  10. A Note on Holography and Phase Transitions

    Directory of Open Access Journals (Sweden)

    Marc Bellon

    2011-01-01

    Full Text Available Focusing on the connection between the Landau theory of second-order phase transitions and the holographic approach to critical phenomena, we study diverse field theories in an anti de Sitter black hole background. Through simple analytical approximations, solutions to the equations of motion can be obtained in closed form which give rather good approximations of the results obtained using more involved numerical methods. The agreement we find stems from rather elementary considerations on perturbation of Schrödinger equations.

  11. Volume phase transitions of cholesteric liquid crystalline gels

    Energy Technology Data Exchange (ETDEWEB)

    Matsuyama, Akihiko, E-mail: matuyama@bio.kyutech.ac.jp [Department of Bioscience and Bioinformatics, Faculty of Computer Science and Systems Engineering, Kyushu Institute of Technology, Kawazu 680-4, Iizuka, Fukuoka 820-8502 (Japan)

    2015-05-07

    We present a mean field theory to describe anisotropic deformations of a cholesteric elastomer without solvent molecules and a cholesteric liquid crystalline gel immersed in isotropic solvents at a thermal equilibrium state. Based on the neoclassical rubber theory of nematic elastomers, we derive an elastic energy and a twist distortion energy, which are important to determine the shape of a cholesteric elastomer (or gel). We demonstrate that when the elastic energy dominates in the free energy, the cholesteric elastomer causes a spontaneous compression in the pitch axis and elongates along the director on the plane perpendicular to the pitch axis. Our theory can qualitatively describe the experimental results of a cholesteric elastomer. We also predict the first-order volume phase transitions and anisotropic deformations of a gel at the cholesteric-isotropic phase transition temperature. Depending on a chirality of a gel, we find a prolate or oblate shape of cholesteric gels.

  12. Effects of octane on the fatty acid composition and transition temperature of Pseudomonas oleovorans membrane lipids during growth in two-liquid-phase continuous cultures

    NARCIS (Netherlands)

    Chen, Qi; Nijenhuis, Atze; Preusting, Hans; Dolfing, Jan; Janssen, Dick B.; Witholt, Bernard

    Growth of Pseudomonas oleovorans GPol in continuous culture containing a bulk n-octane phase resulted in changes of the fatty acid composition of the membrane lipids. Compared to citrate-grown cells, the ratio of C-18 to C-16 fatty acids and the ratio of unsaturated to saturated fatty acids

  13. Low temperature vibrational spectroscopy. III. Structural aspects and detection of phase transitions in crystalline alkali metal and tetramethylammonium hexabromotellurates and platinates

    DEFF Research Database (Denmark)

    Berg, Rolf W.

    1979-01-01

    cases sharp, bands were observed at low temperatures. The spectra have been assigned, and in most cases a confirmation of previous results was obtained. The assignment ambiguity in the literature on the nu4 mode of [PtBr6]2− has been solved, placing it at ~ 130 cm−1. The majority of the new low...... of the tetramethylammonium compounds, methyl torsional IR bands were observed with increasing sharpness at lower temperatures. This behavior can be correlated with a gradual ordering of methyl torsional disorder. The potential energy barrier against methyl group rotation was found to be of the order 4–5 kcal/mol, showing...

  14. Isotropic-Nematic Phase Transitions in Gravitational Systems

    Science.gov (United States)

    Roupas, Zacharias; Kocsis, Bence; Tremaine, Scott

    2017-06-01

    We examine dense self-gravitating stellar systems dominated by a central potential, such as nuclear star clusters hosting a central supermassive black hole. Different dynamical properties of these systems evolve on vastly different timescales. In particular, the orbital-plane orientations are typically driven into internal thermodynamic equilibrium by vector resonant relaxation before the orbital eccentricities or semimajor axes relax. We show that the statistical mechanics of such systems exhibit a striking resemblance to liquid crystals, with analogous ordered-nematic and disordered-isotropic phases. The ordered phase consists of bodies orbiting in a disk in both directions, with the disk thickness depending on temperature, while the disordered phase corresponds to a nearly isotropic distribution of the orbit normals. We show that below a critical value of the total angular momentum, the system undergoes a first-order phase transition between the ordered and disordered phases. At a critical point, the phase transition becomes second order, while for higher angular momenta there is a smooth crossover. We also find metastable equilibria containing two identical disks with mutual inclinations between 90° and 180°.

  15. Isotropic–Nematic Phase Transitions in Gravitational Systems

    Energy Technology Data Exchange (ETDEWEB)

    Roupas, Zacharias; Kocsis, Bence [Institute of Physics, Eötvös University, Pázmány P. s. 1/A, Budapest, 1117 (Hungary); Tremaine, Scott [Institute for Advanced Study, Princeton, NJ 08540 (United States)

    2017-06-20

    We examine dense self-gravitating stellar systems dominated by a central potential, such as nuclear star clusters hosting a central supermassive black hole. Different dynamical properties of these systems evolve on vastly different timescales. In particular, the orbital-plane orientations are typically driven into internal thermodynamic equilibrium by vector resonant relaxation before the orbital eccentricities or semimajor axes relax. We show that the statistical mechanics of such systems exhibit a striking resemblance to liquid crystals, with analogous ordered-nematic and disordered-isotropic phases. The ordered phase consists of bodies orbiting in a disk in both directions, with the disk thickness depending on temperature, while the disordered phase corresponds to a nearly isotropic distribution of the orbit normals. We show that below a critical value of the total angular momentum, the system undergoes a first-order phase transition between the ordered and disordered phases. At a critical point, the phase transition becomes second order, while for higher angular momenta there is a smooth crossover. We also find metastable equilibria containing two identical disks with mutual inclinations between 90° and 180°.

  16. Magnetic-Field-Induced Soft-Mode Quantum Phase Transition in the High-Temperature Superconductor La1.855Sr0.145CuO4

    DEFF Research Database (Denmark)

    Chang, J.; Christensen, Niels Bech; Niedermayer, C.

    2009-01-01

    Inelastic neutron-scattering experiments on the high-temperature superconductor La1.855Sr0.145CuO4 reveal a magnetic excitation gap Delta that decreases continuously upon application of a magnetic field perpendicular to the CuO2 planes. The gap vanishes at the critical field required to induce long...

  17. Nonequilibrium Phase Transition in an Atomistic Glassformer: The Connection to Thermodynamics

    Directory of Open Access Journals (Sweden)

    Francesco Turci

    2017-08-01

    Full Text Available Tackling the low-temperature fate of supercooled liquids is challenging because of the immense time scales involved, which prevent equilibration and lead to the operational glass transition. Relating glassy behavior to an underlying, thermodynamic phase transition is a long-standing open question in condensed matter physics. Like experiments, computer simulations are limited by the small time window over which a liquid can be equilibrated. Here, we address the challenge of low-temperature equilibration using trajectory sampling in a system undergoing a nonequilibrium phase transition. This transition occurs in trajectory space between the normal supercooled liquid and a glassy state rich in low-energy geometric motifs. Our results indicate that this transition might become accessible in equilibrium configurational space at a temperature close to the so-called Kauzmann temperature, and they provide a possible route to unify dynamical and thermodynamical theories of the glass transition.

  18. UA(1) breaking and phase transition in chiral random matrix model

    OpenAIRE

    Sano, T.; Fujii, H.; Ohtani, M

    2009-01-01

    We propose a chiral random matrix model which properly incorporates the flavor-number dependence of the phase transition owing to the \\UA(1) anomaly term. At finite temperature, the model shows the second-order phase transition with mean-field critical exponents for two massless flavors, while in the case of three massless flavors the transition turns out to be of the first order. The topological susceptibility satisfies the anomalous \\UA(1) Ward identity and decreases gradually with the temp...

  19. Thermodynamic Theory with Mixing Entropy Coupled to Mixing Energy for Phase Separation and Solubility Transition

    Science.gov (United States)

    Sasaki, Shigeo

    2017-10-01

    Thermodynamic theory is developed by introducing the concept of intermolecular interaction surface areas in the evaluation of the mixing free energy, which can quantitatively explain the phase separation with the lower critical solution temperature (LCST) and the solubility transition.

  20. Small angle X-ray scattering study of poly(N-isopropyl acrylamide) based cryogels near the volume-phase transition temperature

    Energy Technology Data Exchange (ETDEWEB)

    Chalal, Mohand [Laboratoire d' Electronique Quantique, Faculte de Physique, USTHB Alger, 16111 Alger (Algeria); Ehrburger-Dolle, Francoise; Morfin, Isabelle [Laboratoire de Spectrometrie Physique, UMR 5588 CNRS/UJF, 38402 Saint Martin d' Heres (France); Armas, Maria-Rosa Aguilar de; Lopez, Maria-Luisa [Instituto de Ciencia y TecnologIa de PolImeros, CSIC and CIBER-BBN, 28006 Madrid (Spain); Bley, Francoise, E-mail: francoise.ehrburger-dolle@ujf-grenoble.f [Science et Ingenierie des Materiaux et Procedes, UMR 5266 CNRS/INPG/UJF, 38402 Saint Martin d' Heres (France)

    2010-10-01

    The structural modifications induced by changes in temperature are investigated by Small-Angle X-ray Scattering (SAXS) over a broad range of q-values (3.5x10{sup -2} - 12 nm{sup -1}) in cryogels based on N-isopropylacrylamide (NIPA) and/or 2-Hydroxyethyl methacrylate-L-Lactide-Dextran (HEMA-LLA-D) macromer. Various copolymeric cryogels of these two monomers are prepared by cryopolymerization yielding macroporous gels (cryogels). For the plain pNIPA cryogel, the SAXS curves obtained at each temperature are well fitted by a sum of four equations describing respectively the scattering resulting from the gel surface (power law), from the solid-like (Guinier equation) and liquid-like (Ornstein-Zernike equation) heterogeneities and from the chain-chain correlation yielding a broad peak (pseudo-Voigt equation) in the high-q domain. The temperature dependence of the parameters obtained from the fit is analyzed and discussed. It is shown that the existence of an isoscattering (or isosbestic) point observed in pNIPA gels and in some copolymers is related to features observed by Differential Scanning Calorimetry and swelling ratio measurements.

  1. Extensional Flow-Induced Dynamic Phase Transitions in Isotactic Polypropylene.

    Science.gov (United States)

    Ju, Jianzhu; Wang, Zhen; Su, Fengmei; Ji, Youxin; Yang, Haoran; Chang, Jiarui; Ali, Sarmad; Li, Xiangyang; Li, Liangbin

    2016-09-01

    With a combination of fast extension rheometer and in situ synchrotron radiation ultra-fast small- and wide-angle X-ray scattering, flow-induced crystallization (FIC) of isotactic polypropylene (iPP) is studied at temperatures below and above the melting point of α crystals (Tmα). A flow phase diagram of iPP is constructed in strain rate-temperature space, composing of melt, non-crystalline shish, α and α&β coexistence regions, based on which the kinetic and dynamic competitions among these four phases are discussed. Above Tmα , imposing strong flow reverses thermodynamic stabilities of the disordered melt and the ordered phases, leading to the occurrence of FIC of β and α crystals as a dynamic phase transition. Either increasing temperature or stain rate favors the competiveness of the metastable β over the stable α crystals, which is attributed to kinetic rate rather than thermodynamic stability. The violent competitions among four phases near the boundary of crystal-melt may frustrate crystallization and result in the non-crystalline shish winning out. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Theoretical Studies on Phase Transitions in Quasi-One-Dimensional Molecular Conductors

    Directory of Open Access Journals (Sweden)

    Yuichi Otsuka

    2012-07-01

    Full Text Available A review is given for recent theoretical studies on phase transitions in quasi-one-dimensional molecular conductors with a quarter-filled band. By lowering temperature, charge transfer salts exhibit a variety of transitions accompanying symmetry breaking, such as charge ordering, lattice dimerization, antiferromagnetic transition, spin-Peierls distortion, and so on. Analyses on microscopic quasi-one-dimensional models provide their systematic understandings, by the complementary use of different analytical and numerical techniques; they can reproduce finite-temperature phase transitions, whose results can be directly compared with experiments and give feedbacks to material design.

  3. Quark–hadron phase transition in massive gravity

    Energy Technology Data Exchange (ETDEWEB)

    Atazadeh, K., E-mail: atazadeh@azaruniv.ac.ir

    2016-11-15

    We study the quark–hadron phase transition in the framework of massive gravity. We show that the modification of the FRW cosmological equations leads to the quark–hadron phase transition in the early massive Universe. Using numerical analysis, we consider that a phase transition based on the chiral symmetry breaking after the electroweak transition, occurred at approximately 10 μs after the Big Bang to convert a plasma of free quarks and gluons into hadrons.

  4. A macroscopic constitutive model of temperature-induced phase transition of polycrystalline Ni{sub 2}MnGa by directional solidification

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Yuping, E-mail: zhuyuping@126.com; Gu, Yunling; Liu, Hongguang

    2015-02-25

    Directional solidification technology has been widely used to improve the properties of polycrystalline Ni{sub 2}MnGa materials. Mechanical training can adjust the internal organizational structures of the materials, reduce the stress of twin boundaries motion, and then result in larger strain at lower outfield levels. In this paper, we test the microscopic structure of Ni{sub 2}MnGa polycrystalline ferromagnetic shape memory alloy produced by directional solidification and compress it along two axes successively for mechanical training. The influences of pre-compressive stresses on the temperature-induced strains are analyzed. The macroscopic mechanical behaviors show anisotropy. According to the generating mechanism of the macroscopic strain, a three-dimensional constitutive model is established. Based on thermodynamic method, the kinetic equations of the martensitic transformation and inverse transformation are presented considering the driving force and energy dissipation. The prediction curves of temperature-induce strains along two different directions are investigated. And the results coincide well with the experiment data. It well explains the macroscopic anisotropy mechanical behaviors and fits for using in engineering.

  5. Intertwined Electronic and Structural Phase Transitions in the In/Si(111) Interface

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Jiandong [University of Tennessee, Knoxville (UTK); Lee, G. [Inha University, Korea; Plummer, E Ward [ORNL

    2005-01-01

    The structural (4 x 1) to (8 x 2) transition and the electronic metal to semimetal transition at the In/Si interface are studied with scanning tunneling microscopy and spectroscopy. Both transitions are gradual, resulting in a complex domain structure in the transition temperature regime. At these intermediate temperatures, the metallic (4 x 1) and semimetallic (8 x 2) domains coexist with each other and with new nanophases. By probing the two intertwined but distinguishable transitions at the atomic level, the interaction between different phases is visualized directly.

  6. Intertwined Electronic and Structural Phase Transitions in the In/Si(111) Interface

    Science.gov (United States)

    Guo, Jiandong; Lee, Geunseop; Plummer, E. W.

    2005-07-01

    The structural (4×1) to (8×2) transition and the electronic metal to semimetal transition at the In/Si interface are studied with scanning tunneling microscopy and spectroscopy. Both transitions are gradual, resulting in a complex domain structure in the transition temperature regime. At these intermediate temperatures, the metallic (4×1) and semimetallic (8×2) domains coexist with each other and with new nanophases. By probing the two intertwined but distinguishable transitions at the atomic level, the interaction between different phases is visualized directly.

  7. Phase transitions in biogenic amorphous calcium carbonate

    Science.gov (United States)

    Gong, Yutao

    Geological calcium carbonate exists in both crystalline phases and amorphous phases. Compared with crystalline calcium carbonate, such as calcite, aragonite and vaterite, the amorphous calcium carbonate (ACC) is unstable. Unlike geological calcium carbonate crystals, crystalline sea urchin spicules (99.9 wt % calcium carbonate and 0.1 wt % proteins) do not present facets. To explain this property, crystal formation via amorphous precursors was proposed in theory. And previous research reported experimental evidence of ACC on the surface of forming sea urchin spicules. By using X-ray absorption near-edge structure (XANES) spectroscopy and photoelectron emission microscopy (PEEM), we studied cross-sections of fresh sea urchin spicules at different stages (36h, 48h and 72h after fertilization) and observed the transition sequence of three mineral phases: hydrated ACC → dehydrated ACC → biogenic calcite. In addition, we unexpectedly found hydrated ACC nanoparticles that are surrounded by biogenic calcite. This observation indicates the dehydration from hydrated ACC to dehydrated ACC is inhibited, resulting in stabilization of hydrated ACC nanoparticles. We thought that the dehydration was inhibited by protein matrix components occluded within the biomineral, and we designed an in vitro assay to test the hypothesis. By utilizing XANES-PEEM, we found that SM50, the most abundant occluded matrix protein in sea urchin spicules, has the function to stabilize hydrated ACC in vitro.

  8. Kinetics of first order phase transitions

    CERN Document Server

    Slezov, Vitaly V

    2009-01-01

    Filling a gap in the literature, this crucial publication on the renowned Lifshitz-Slezov-Wagner Theory of first-order phase transitions is authored by one of the scientists who gave it its name. Prof Slezov spent decades analyzing this topic and obtained a number of results that form the cornerstone of this rapidly developing branch of science.Following an analysis of unresolved problems together with proposed solutions, the book develops a theoretical description of the overall course of first-order phase transformations, starting from the nucleation state right up to the late stages of coarsening. In so doing, the author illustrates the results by way of numerical computations and experimental applications. The outline of the general results is performed for segregation processes in solutions and the results used in the analysis of a variety of different topics, such as phase formation in multi-component solutions, boiling in one- and multi-component liquids, vacancy cluster evolution in solids with and wi...

  9. QCD PHASE TRANSITIONS-VOLUME 15.

    Energy Technology Data Exchange (ETDEWEB)

    SCHAFER,T.

    1998-11-04

    The title of the workshop, ''The QCD Phase Transitions'', in fact happened to be too narrow for its real contents. It would be more accurate to say that it was devoted to different phases of QCD and QCD-related gauge theories, with strong emphasis on discussion of the underlying non-perturbative mechanisms which manifest themselves as all those phases. Before we go to specifics, let us emphasize one important aspect of the present status of non-perturbative Quantum Field Theory in general. It remains true that its studies do not get attention proportional to the intellectual challenge they deserve, and that the theorists working on it remain very fragmented. The efforts to create Theory of Everything including Quantum Gravity have attracted the lion share of attention and young talent. Nevertheless, in the last few years there was also a tremendous progress and even some shift of attention toward emphasis on the unity of non-perturbative phenomena. For example, we have seen some. efforts to connect the lessons from recent progress in Supersymmetric theories with that in QCD, as derived from phenomenology and lattice. Another example is Maldacena conjecture and related development, which connect three things together, string theory, super-gravity and the (N=4) supersymmetric gauge theory. Although the progress mentioned is remarkable by itself, if we would listen to each other more we may have chance to strengthen the field and reach better understanding of the spectacular non-perturbative physics.

  10. Chiral smectic transition phases appearing near the electric-field-induced phase transition observed by resonant microbeam x-ray scattering.

    Science.gov (United States)

    Iida, Atsuo; Nishiyama, Isa; Takanishi, Yoichi

    2014-03-01

    The electric-field-induced phase transition of a chiral liquid crystal containing Br revealed a transition phase between the three-layer periodicity ferrielectric phase and the synclinic ferroelectric phase in the electric field versus temperature phase diagram. Resonant x-ray scattering from the transition phase showed a diffuse streak or spotty weak reflections, which were composed of strong m/3-order (where m = 1 and 2) reflections and other weak peaks. The spotty reflections were found to be related to a 12-layer periodicity phase with a weak contribution from the 15-layer periodicity. An x-ray intensity analysis based on the Ising model suggested that the 12-layer periodicity phase was composed of two three-layer ferrielectric blocks and six synclinic layers. This model indicated that, in the transition phase, the three-layer ferrielectric molecular configuration gradually changed to the synclinic configuration. The diffuse streak appearing around m/3-order reflections near the field-induced transition from the four-layer periodicity phase to the synclinic ferroelectric phase is also discussed.

  11. High pressure phase transitions for CdSe

    Indian Academy of Sciences (India)

    The structure and pressure-induced phase transitions for CdSe are investigated using first-principles calculations. The pressure-induced phase transition sequence WZ/ZB → Rs → → CsCl for CdSe is drawn reasonably for the fist time, the corresponding transition pressures are 3.8, 29 and 107 GPa, respectively and ...

  12. Holographic quantum phase transitions and interacting bulk scalars

    Directory of Open Access Journals (Sweden)

    Pankaj Chaturvedi

    2014-12-01

    Full Text Available We consider a system of two massive, mutually interacting probe real scalar fields, in zero temperature holographic backgrounds. The system does not have any continuous symmetry. For a suitable range of the interaction parameters adhering to the interaction potential between the bulk scalars, we have shown that as one turns on the source for one scalar field, the system may go through a second order quantum critical phase transition across which the second scalar field forms a condensate. We have looked at the resulting phase diagram and numerically computed the condensate. We have also investigated our system in two different backgrounds: AdS4 and AdS soliton, and got similar phase structure.

  13. Elevated transition temperature in Ge doped VO2 thin films

    Science.gov (United States)

    Krammer, Anna; Magrez, Arnaud; Vitale, Wolfgang A.; Mocny, Piotr; Jeanneret, Patrick; Guibert, Edouard; Whitlow, Harry J.; Ionescu, Adrian M.; Schüler, Andreas

    2017-07-01

    Thermochromic GexV1-xO2+y thin films have been deposited on Si (100) substrates by means of reactive magnetron sputtering. The films were then characterized by Rutherford backscattering spectrometry (RBS), four-point probe electrical resistivity measurements, X-ray diffraction, and atomic force microscopy. From the temperature dependent resistivity measurements, the effect of Ge doping on the semiconductor-to-metal phase transition in vanadium oxide thin films was investigated. The transition temperature was shown to increase significantly upon Ge doping (˜95 °C), while the hysteresis width and resistivity contrast gradually decreased. The precise Ge concentration and the film thickness have been determined by RBS. The crystallinity of phase-pure VO2 monoclinic films was confirmed by XRD. These findings make the use of vanadium dioxide thin films in solar and electronic device applications—where higher critical temperatures than 68 °C of pristine VO2 are needed—a viable and promising solution.

  14. The [epsilon] expansion and the electroweak phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Arnold, P.; Yaffe, L.G. (Department of Physics, University of Washington, Seattle, Washington 98195 (United States))

    1994-03-15

    Standard perturbative (or mean field theory) techniques are not adequate for studying the finite-temperature electroweak phase transition in some cases of interest to scenarios for electroweak baryogenesis. We instead study the properties of this transition using the renormalization group and the [epsilon] expansion. This expansion, based on dimensional continuation from 3 to 4--[epsilon] spatial dimensions, provides a systematic approximation for computing the effects of (near-)critical fluctuations. The [epsilon] expansion is known to predict a first-order transition in Higgs theories, even for heavy Higgs boson masses. The validity of this conclusion in the standard model is examined in detail. A variety of physical quantities are computed at leading and next-to-leading order in [epsilon]. For moderately light Higgs boson masses (below 100 GeV), the [epsilon] expansion suggests that the transition is more strongly first order than is predicted by the conventional analysis based on the one-loop (ring-improved) effective potential. Nevertheless, the rate of baryon nonconservation after the transition is found to be [ital larger] than that given by the one-loop effective potential calculation. Detailed next-to-leading order calculations of some sample quantities suggests that the [epsilon] expansion is reasonably well behaved for Higgs boson masses below 100--200 GeV. We also compare the [epsilon] expansion with large-[ital N] results (where [ital N] is the number of scalar fields) and find that the [epsilon] expansion is less well behaved in this limit.

  15. New type of two-dimensional phase transition

    Science.gov (United States)

    Tikhov, M.; Stolzenberg, M.; Bauer, E.

    1987-12-01

    A first-order phase transition in a Cu double layer on a Mo(110) surface in which the orientation of the interfacial misfit dislocations changes by 90° is reported. The transition shows considerable hysteresis. The analysis of the transition and of an irreversible transition preceding it suggests that the core of the misfit dislocations is partially empty.

  16. Global quantum discord and quantum phase transition in XY model

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Si-Yuan [Institute of Modern Physics, Northwest University, Xian 710069 (China); Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Zhang, Yu-Ran, E-mail: yrzhang@iphy.ac.cn [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Yang, Wen-Li, E-mail: wlyang@nwu.edu.cn [Institute of Modern Physics, Northwest University, Xian 710069 (China); Fan, Heng, E-mail: hfan@iphy.ac.cn [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Collaborative Innovation Center of Quantum Matter, Beijing 100190 (China); Institute of Modern Physics, Northwest University, Xian 710069 (China)

    2015-11-15

    We study the relationship between the behavior of global quantum correlations and quantum phase transitions in XY model. We find that the two kinds of phase transitions in the studied model can be characterized by the features of global quantum discord (GQD) and the corresponding quantum correlations. We demonstrate that the maximum of the sum of all the nearest neighbor bipartite GQDs is effective and accurate for signaling the Ising quantum phase transition, in contrast, the sudden change of GQD is very suitable for characterizing another phase transition in the XY model. This may shed lights on the study of properties of quantum correlations in different quantum phases.

  17. QCD phase transition with chiral quarks and physical quark masses.

    Science.gov (United States)

    Bhattacharya, Tanmoy; Buchoff, Michael I; Christ, Norman H; Ding, H-T; Gupta, Rajan; Jung, Chulwoo; Karsch, F; Lin, Zhongjie; Mawhinney, R D; McGlynn, Greg; Mukherjee, Swagato; Murphy, David; Petreczky, P; Renfrew, Dwight; Schroeder, Chris; Soltz, R A; Vranas, P M; Yin, Hantao

    2014-08-22

    We report on the first lattice calculation of the QCD phase transition using chiral fermions with physical quark masses. This calculation uses 2+1 quark flavors, spatial volumes between (4 fm)(3) and (11 fm)(3) and temperatures between 139 and 196 MeV. Each temperature is calculated at a single lattice spacing corresponding to a temporal Euclidean extent of N(t) = 8. The disconnected chiral susceptibility, χ(disc) shows a pronounced peak whose position and height depend sensitively on the quark mass. We find no metastability near the peak and a peak height which does not change when a 5 fm spatial extent is increased to 10 fm. Each result is strong evidence that the QCD "phase transition" is not first order but a continuous crossover for m(π) = 135 MeV. The peak location determines a pseudocritical temperature T(c) = 155(1)(8) MeV, in agreement with earlier staggered fermion results. However, the peak height is 50% greater than that suggested by previous staggered results. Chiral SU(2)(L) × SU(2)(R) symmetry is fully restored above 164 MeV, but anomalous U(1)(A) symmetry breaking is nonzero above T(c) and vanishes as T is increased to 196 MeV.

  18. Observables of non-equilibrium phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Tomasik, Boris [Univerzita Mateja Bela, FPV, Banska Bystrica (Slovakia); Ceske vysoke uceni technicke v Praze, FJFI, Prague (Czech Republic); Schulc, Martin; Kopecna, Renata [Ceske vysoke uceni technicke v Praze, FJFI, Prague (Czech Republic); Melo, Ivan [Univerzita Mateja Bela, FPV, Banska Bystrica (Slovakia); Zilinska univerzita, Elektrotechnicka fakulta, Zilina (Slovakia)

    2016-08-15

    A rapidly expanding fireball which undergoes first-order phase transition will supercool and proceed via spinodal decomposition. Hadrons are produced from the individual fragments as well as the left-over matter filling the space between them. Emission from fragments should be visible in rapidity correlations, particularly of protons. In addition to that, even within narrow centrality classes, rapidity distributions will be fluctuating from one event to another in case of fragmentation. This can be identified with the help of the Kolmogorov-Smirnov test. Finally, we present a method which allows to sort events with varying rapidity distributions, in such a way that events with similar rapidity histograms are grouped together. (orig.)

  19. Magnetocaloric materials and first order phase transitions

    DEFF Research Database (Denmark)

    Neves Bez, Henrique

    and magnetocaloric regenerative tests. The magnetic, thermal and structural properties obtained from such measurements are then evaluated through different models, i.e. the Curie-Weiss law, the Bean-Rodbell model, the free electron model and the Debye model.The measured magnetocaloric properties of La0.67Ca0.33MnO3...... through modelling. Moreover, inverse susceptibility measurements showed what could be evidences of magnetic polarons being formed in the paramagnetic phase of the material. The origin of the first order transition seems to be due to the magneto-elastic coupling observed through isothermal magnetostriction...... and dilatometric measurements. Although the Bean-Rodbell model has described with a good agreement the entropy change, hysteresis, magnetization and heat capacity, it has failed to describe the isothermal magnetostriction. It is suggested that such failure could be related to different factors that might influence...

  20. The phase transition of Axelrod's model revisited

    CERN Document Server

    Reia, Sandro M

    2016-01-01

    Axelrod's model with $F=2$ cultural features, where each feature can assume $k$ states drawn from a Poisson distribution of parameter $q$, exhibits a continuous nonequilibrium phase transition in the square lattice. Here we use extensive Monte Carlo simulations and finite size scaling to study the critical behavior of the order parameter $\\rho$, which is the fraction of sites that belong to the largest domain of an absorbing configuration averaged over many runs. We find that it vanishes as $\\rho \\sim \\left (q_c^0 - q \\right)^\\beta$ with $\\beta \\approx 0.25$ at the critical point $q_c^0 \\approx 3.10$ and that the exponent that measures the width of the critical region is $\

  1. Nonlinear clustering during the BEC dark matter phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Freitas, Rodolfo C. de [Universidade Federal do Espirito Santo, Vitoria (Brazil); Ciencia e Tecnologia do Espirito Santo, Instituto Federal de Educacao, Vitoria (Brazil); Velten, Hermano [Universidade Federal do Espirito Santo, Vitoria (Brazil); Aix Marseille Universite, UMR 7332, CPT, Marseille (France)

    2015-12-15

    Spherical collapse of the Bose-Einstein condensate (BEC) dark matter model is studied in the Thomas-Fermi approximation. The evolution of the overdensity of the collapsed region and its expansion rate are calculated for two scenarios. We consider the case of a sharp phase transition (which happens when the critical temperature is reached) from the normal dark matter state to the condensate one and the case of a smooth first order phase transition where there is a continuous conversion of ''normal'' dark matter to the BEC phase. We present numerical results for the physics of the collapse for a wide range of the model's space parameter, i.e. the mass of the scalar particle m{sub χ} and the scattering length l{sub s}. We show the dependence of the transition redshift on m{sub χ} and l{sub s}. Since small scales collapse earlier and eventually before the BEC phase transition, the evolution of collapsing halos in this limit is indeed the same in both the CDM and the BEC models. Differences are expected to appear only on the largest astrophysical scales. However, we argue that the BEC model is almost indistinguishable from the usual dark matter scenario concerning the evolution of nonlinear perturbations above typical clusters scales, i.e., >or similar 10{sup 14}M{sub s}un. This provides an analytical confirmation for recent results from cosmological numerical simulations (Schive et al., Nat Phys 10:496, 2014). (orig.)

  2. Striped nanoscale phase separation at the metal–insulator transition of heteroepitaxial nickelates

    Science.gov (United States)

    Mattoni, G.; Zubko, P.; Maccherozzi, F.; van der Torren, A.J.H.; Boltje, D. B.; Hadjimichael, M.; Manca, N.; Catalano, S.; Gibert, M.; Liu, Y.; Aarts, J.; Triscone, J.-M.; Dhesi, S. S.; Caviglia, A. D.

    2016-01-01

    Nucleation processes of mixed-phase states are an intrinsic characteristic of first-order phase transitions, typically related to local symmetry breaking. Direct observation of emerging mixed-phase regions in materials showing a first-order metal–insulator transition (MIT) offers unique opportunities to uncover their driving mechanism. Using photoemission electron microscopy, we image the nanoscale formation and growth of insulating domains across the temperature-driven MIT in NdNiO3 epitaxial thin films. Heteroepitaxy is found to strongly determine the nanoscale nature of the phase transition, inducing preferential formation of striped domains along the terraces of atomically flat stepped surfaces. We show that the distribution of transition temperatures is a local property, set by surface morphology and stable across multiple temperature cycles. Our data provide new insights into the MIT of heteroepitaxial nickelates and point to a rich, nanoscale phenomenology in this strongly correlated material. PMID:27804954

  3. Striped nanoscale phase separation at the metal-insulator transition of heteroepitaxial nickelates

    Science.gov (United States)

    Mattoni, G.; Zubko, P.; Maccherozzi, F.; van der Torren, A. J. H.; Boltje, D. B.; Hadjimichael, M.; Manca, N.; Catalano, S.; Gibert, M.; Liu, Y.; Aarts, J.; Triscone, J.-M.; Dhesi, S. S.; Caviglia, A. D.

    2016-11-01

    Nucleation processes of mixed-phase states are an intrinsic characteristic of first-order phase transitions, typically related to local symmetry breaking. Direct observation of emerging mixed-phase regions in materials showing a first-order metal-insulator transition (MIT) offers unique opportunities to uncover their driving mechanism. Using photoemission electron microscopy, we image the nanoscale formation and growth of insulating domains across the temperature-driven MIT in NdNiO3 epitaxial thin films. Heteroepitaxy is found to strongly determine the nanoscale nature of the phase transition, inducing preferential formation of striped domains along the terraces of atomically flat stepped surfaces. We show that the distribution of transition temperatures is a local property, set by surface morphology and stable across multiple temperature cycles. Our data provide new insights into the MIT of heteroepitaxial nickelates and point to a rich, nanoscale phenomenology in this strongly correlated material.

  4. Noninvasive Measurement of Core Temperature. Phase 1.

    Science.gov (United States)

    Topical Testing proposes the development of a noninvasive device to monitor core temperature by sampling the maximal temperature of the respiratory...air during expiration. Phase I development used a fast rise-time thermocouple to monitor the temperature of the expired air of an anesthetized animal

  5. Results from 3D electroweak phase transition simulations

    CERN Document Server

    Farakos, K.; Laine, M.; Rummukainen, K.; Shaposhnikov, Mikhail E.

    1995-01-01

    We study the phase transition in SU(2)-Higgs model on the lattice using the 3D dimensionally reduced formalism. The 3D formalism enables us to obtain highly accurate Monte Carlo results, which we extrapolate both to the infinite volume and to the continuum limit. Our formalism also provides for a well-determined and unique way to relate the results to the perturbation theory. We measure the critical temperature, latent heat and interface tension for Higgs masses up to 70 GeV.

  6. Phase Transitions above the Yrast Line in {sup 154}Dy

    Energy Technology Data Exchange (ETDEWEB)

    Ma, W. C. [Mississippi State University, Mississippi State, Mississippi 39762 (United States); Martin, V. [Analisis Numerico, Facultad de Informatica, Universidad Politecnica de Madrid, E-28660 Madrid, (Spain); Khoo, T. L. [Argonne National Laboratory, Argonne, Illinois 60439 (United States); Lauritsen, T. [Argonne National Laboratory, Argonne, Illinois 60439 (United States); Egido, J. L. [Departamento de Fisica Teorica C-XI, Universidad Autonoma de Madrid, E-28049 Madrid, (Spain); Ahmad, I. [Argonne National Laboratory, Argonne, Illinois 60439 (United States); Bhattacharyya, P. [Purdue University, West Lafayette, Indiana 47907 (United States); Carpenter, M. P. [Argonne National Laboratory, Argonne, Illinois 60439 (United States); Daly, P. J. [Purdue University, West Lafayette, Indiana 47907 (United States); Grabowski, Z. W. [Purdue University, West Lafayette, Indiana 47907 (United States)] (and others)

    2000-06-26

    Spectra of the E2 quasicontinuum {gamma} rays feeding different spin regions of the {sup 154}Dy yrast line have been extracted. These are compared with corresponding theoretical spectra obtained by numerical simulations based on temperature-dependent Hartree-Fock theory, with thermal shape fluctuations. In this manner, different regions of the spin-energy plane can be examined. The results support the predictions of a smeared-out phase transition at high spin above the yrast line. (c) 2000 The American Physical Society.

  7. Paramagnetism-ferromagnetism phase transition in a dyonic black hole

    Science.gov (United States)

    Cai, Rong-Gen; Yang, Run-Qiu

    2014-10-01

    Coupling an antisymmetric tensor field to the electromagnetic field in a dyonic Reissner-Nordström-anti-de Sitter black hole background, we build a holographic model for the paramagnetism/ferromagnetism phase transition. In the case of zero magnetic field, the time reversal symmetry is broken spontaneously and spontaneous magnetization happens at low temperatures. The critical exponents are in agreement with the ones from mean field theory. In the case of nonzero magnetic field, the model realizes the hysteresis loop of a single magnetic domain and the magnetic susceptibility satisfies the Curie-Weiss law.

  8. Constrained caloric curves and phase transition for hot nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Borderie, B., E-mail: borderie@ipno.in2p3.fr [Institut de Physique Nucléaire, CNRS-IN2P3, Université Paris-Sud 11, F-91406 Orsay Cedex (France); Piantelli, S. [INFN Sezione di Firenze, 50019 Sesto Fiorentino (Italy); Rivet, M.F. [Institut de Physique Nucléaire, CNRS-IN2P3, Université Paris-Sud 11, F-91406 Orsay Cedex (France); Raduta, Ad.R. [National Institute for Physics and Nuclear Engineering, RO-76900 Bucharest-Magurele (Romania); Ademard, G. [Institut de Physique Nucléaire, CNRS-IN2P3, Université Paris-Sud 11, F-91406 Orsay Cedex (France); Bonnet, E. [GANIL, (DSM-CEA/CNRS-IN2P3), F-14076 Caen Cedex (France); Bougault, R. [LPC Caen, ENSICAEN, Université de Caen, CNRS-IN2P3, F-14050 Caen Cedex (France); Chbihi, A.; Frankland, J.D. [GANIL, (DSM-CEA/CNRS-IN2P3), F-14076 Caen Cedex (France); Galichet, E. [Institut de Physique Nucléaire, CNRS-IN2P3, Université Paris-Sud 11, F-91406 Orsay Cedex (France); Conservatoire National des Arts et Métiers, F-75141 Paris Cedex 03 (France); Gruyer, D. [GANIL, (DSM-CEA/CNRS-IN2P3), F-14076 Caen Cedex (France); Guinet, D.; Lautesse, P. [Université Claude Bernard Lyon 1, Institut de Physique Nucléaire, CNRS-IN2P3, F-69622 Villeurbanne Cedex (France); Le Neindre, N.; Lopez, O. [LPC Caen, ENSICAEN, Université de Caen, CNRS-IN2P3, F-14050 Caen Cedex (France); Marini, P. [GANIL, (DSM-CEA/CNRS-IN2P3), F-14076 Caen Cedex (France); and others

    2013-06-10

    Simulations based on experimental data obtained from multifragmenting quasi-fused nuclei produced in central {sup 129}Xe+{sup nat}Sn collisions have been used to deduce event by event freeze-out properties in the thermal excitation energy range 4–12 AMeV [S. Piantelli, et al., INDRA Collaboration, Nucl. Phys. A 809 (2008) 111]. From these properties and the temperatures deduced from proton transverse momentum fluctuations, constrained caloric curves have been built. At constant average volumes caloric curves exhibit a monotonic behaviour whereas for constrained pressures a backbending is observed. Such results support the existence of a first order phase transition for hot nuclei.

  9. Temperature and electric-field induced phase transitions, and full tensor properties of [011] C -poled domain-engineered tetragonal 0.63Pb(Mg1/3Nb2/3)-0.37PbTiO3 single crystals.

    Science.gov (United States)

    Zheng, Limei; Jing, Yujia; Lu, Xiaoyan; Wang, Ruixue; Liu, Gang; Lü, Weiming; Zhang, Rui; Cao, Wenwu

    2016-03-01

    The phase-transition sequence of 0.67Pb(Mg1/3Nb2/3)-0.37PbTiO3 (PMN-0.37PT) single crystals driven by the electric (E) field and temperature is comprehensively studied. Based on the strain-E field loop, polarization-E field loop, and the evolution of domain configurations, the E field along the [011] C induced phase transitions have been confirmed to be as follows: tetragonal (T) → monoclinic (MC ) → single domain orthorhombic (O) phase. As the E field decreases, the induced O phase cannot be maintained and transformed to the MC phase, then to the coexistence state of MC and T phases. In addition, the complete sets of dielectric, piezoelectric, and elastic constants for the [011] C -poled domain-engineered PMN-0.37PT single crystal were measured at room temperature, which show high longitudinal dielectric, piezoelectric, and electromechanical properties ([Formula: see text], d33 = 1052 pC/N, and k33 = 0.766). Our results revealed that the MC phase plays an important role in the high electromechanical properties of this domain-engineered single crystal. The temperature dependence of the domain configuration revealed that the volume fraction of the MC phase decreases with temperature accompanied by the reduction of [Formula: see text], d31, and k31 due to the substantially smaller intrinsic properties of the T phase.

  10. Large radius generation and phase transitions in cosmology with extra dimensions

    CERN Document Server

    Dienes, K.R.; Gherghetta, T.; Riotto, A.

    2000-01-01

    We consider the role of extra dimensions in cosmology, focusing on cosmological phase transitions in field theory and the Hagedorn transition and generation of a large compactification radius in string theory. We find that for temperatures larger than the compactification radii, cosmological phase transitions in field theory are delayed compared with the usual four-dimensional case. Furthermore, we argue that phase transitions in extra dimensions cannot be of the first-order type. In string theories with large internal dimensions, the Hagedorn temperature is a limiting temperature and gives rise to significant entropy production as the universe approaches this temperature. We also point out that string thermal effects give rise to an effective potential for the radius of the compactified dimension. This leads to a thermal mechanism for generating a large radius of compactification.

  11. Survey of CRISM Transition Phase Observations

    Science.gov (United States)

    Seelos, F. P.; Murchie, S. L.; Choo, T. H.; McGovern, J. A.

    2006-12-01

    The Mars Reconnaissance Orbiter (MRO) transition phase extends from the end of aerobraking (08/30/06) to the start of the Primary Science Phase (PSP) (11/08/2006). Within this timeframe, the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) will acquire Mars scene observations in association with the deployment of the telescope cover (09/27/06) and during the operational checkout of the full science payload (09/29/06 - 10/05/06). The CRISM cover opening sequence includes scene observations that will be used to verify deployment and to validate the on-orbit instrument wavelength calibration. The limited cover opening observation set consists of: 1. A hyperspectral nadir scan acquired as the cover is deployed (first light) 2. A single targeted (gimbaled) hyperspectral observation in the northern plains 3. A restricted duration nadir multispectral strip The high level objectives for the science payload checkout are to obtain observations in support of in-flight wavelength, radiometric, and geometric instrument calibration, to acquire data that will contribute to the development of a first-order hyperspectral atmospheric correction, and to exercise numerous spacecraft and instrument observing modes and strategies that will be employed during PSP. The science payload checkout also enables a unique collaboration between the Mars Express OMEGA and CRISM teams, with both spectrometers slated to observe common target locations with a minimal time offset for the purpose of instrument cross-calibration. The priority CRISM observations for the payload checkout include: 1. Multispectral nadir and hyperspectral off-nadir targeted observations in support of the cross-calibration experiment with OMEGA 2. Terminator-to-terminator multispectral data acquisition demonstrating the strategy that will be used to construct the global multispectral survey map 3. Terminator-to-terminator atmospheric emission phase function (EPF) data acquisition demonstrating the observation

  12. Phase Transitions, Geometrothermodynamics, and Critical Exponents of Black Holes with Conformal Anomaly

    Directory of Open Access Journals (Sweden)

    Jie-Xiong Mo

    2014-01-01

    Full Text Available We investigate the phase transitions of black holes with conformal anomaly in canonical ensemble. Some interesting and novel phase transition phenomena have been discovered. It is shown that there are striking differences in both Hawking temperature and phase structure between black holes with conformal anomaly and those without it. Moreover, we probe in detail the dependence of phase transitions on the choice of parameters. The results show that black holes with conformal anomaly have much richer phase structure than those without it. There would be two, only one, or no phase transition points depending on the parameters. The corresponding parameter regions are derived both numerically and graphically. Geometrothermodynamics are built up to examine the phase structure we have discovered. It is shown that Legendre invariant thermodynamic scalar curvature diverges exactly where the specific heat diverges. Furthermore, critical behaviors are investigated by calculating the relevant critical exponents. And we prove that these critical exponents satisfy the thermodynamic scaling laws.

  13. A Direct Method for Viewing Ferromagnetic Phase Transition.

    Science.gov (United States)

    Lue, Chin-Shan

    1994-01-01

    Provides a method, using the Rowland ring as a specimen, to observe the phase transition process directly on the oscilloscope and even extract the critical exponent of ferromagnetic transition. Includes theory, experimental setup, and results. (MVL)

  14. Non-equilibrium phase transitions in complex plasma

    NARCIS (Netherlands)

    Sutterlin, K. R.; Wysocki, A.; Rath, C.; Ivlev, A. V.; Thomas, H. M.; Khrapak, S.; Zhdanov, S.; Rubin-Zuzic, M.; W. J. Goedheer,; Fortov, V. E.; Lipaev, A. M.; Molotkov, V. I.; Petrov, O. F.; Morfill, G. E.; Lowen, H.

    2010-01-01

    Complex plasma being the 'plasma state of soft matter' is especially suitable for investigations of non-equilibrium phase transitions. Non-equilibrium phase transitions can manifest in dissipative structures or self-organization. Two specific examples are lane formation and phase

  15. A superconductor to superfluid phase transition in liquid metallic hydrogen.

    Science.gov (United States)

    Babaev, Egor; Sudbø, Asle; Ashcroft, N W

    2004-10-07

    Although hydrogen is the simplest of atoms, it does not form the simplest of solids or liquids. Quantum effects in these phases are considerable (a consequence of the light proton mass) and they have a demonstrable and often puzzling influence on many physical properties, including spatial order. To date, the structure of dense hydrogen remains experimentally elusive. Recent studies of the melting curve of hydrogen indicate that at high (but experimentally accessible) pressures, compressed hydrogen will adopt a liquid state, even at low temperatures. In reaching this phase, hydrogen is also projected to pass through an insulator-to-metal transition. This raises the possibility of new state of matter: a near ground-state liquid metal, and its ordered states in the quantum domain. Ordered quantum fluids are traditionally categorized as superconductors or superfluids; these respective systems feature dissipationless electrical currents or mass flow. Here we report a topological analysis of the projected phase of liquid metallic hydrogen, finding that it may represent a new type of ordered quantum fluid. Specifically, we show that liquid metallic hydrogen cannot be categorized exclusively as a superconductor or superfluid. We predict that, in the presence of a magnetic field, liquid metallic hydrogen will exhibit several phase transitions to ordered states, ranging from superconductors to superfluids.

  16. Influence of Eu3+-Doped on Phase Transition Kinetics of Pseudoboehmite

    Directory of Open Access Journals (Sweden)

    Fuliang Zhu

    2013-01-01

    Full Text Available The influence of Eu3+-doped on phase transition kinetics of pseudoboehmite has not been reported in the literature. Through dropping Eu(NO33 into pseudoboehmite colloidal solution, pseudoboehmite xerogel was produced using spray pyrolysis. The influence of Eu3+-doped on the mechanism of pseudoboehmite phase transition kinetics has been calculated and analyzed by TG/DSC, XRD, and Kissinger equation. Part of Eu3+ ion formed compound EuAl12O19, which existed between α-Al2O3 grains. Bulk diffusion of Al3+ was prevented from compound EuAl12O19. Therefore, phase transition kinetics rate of θ-Al2O3 → α-Al2O3 was slowed down, causing an increase of phase transition activation energy and elevation of phase transition temperature.

  17. Phase transitions in Cs5(HSO4)2(H2PO4)3 crystal

    Science.gov (United States)

    Grebenev, V. V.; Makarova, I. P.; Ksenofontov, D. A.; Komornikov, V. A.; Dmitricheva, E. V.

    2013-11-01

    The symmetry (sp. gr. I 3 d) and lattice parameters have been determined for the first time for Cs5(H2SO4)2(H2PO4)3 crystals in the temperature range from 172 to 390 K. The thermal and optical properties of crystals, as well as their conductivity, have been investigated at elevated temperatures. It is shown that a crystal heated to T = 365 K undergoes a phase transition with symmetry lowering to the tetragonal phase (with the parameters a = 4.965(1) Å and c = 5.016(1) Å), while at T ≈ 390 K a phase transition to the cubic phase is presumably observed. With a decrease in temperature, a phase transition without a change in symmetry occurs at T = 240 K.

  18. Predicting a new phase (T'') of two-dimensional transition metal di-chalcogenides and strain-controlled topological phase transition

    Science.gov (United States)

    Ma, Fengxian; Gao, Guoping; Jiao, Yalong; Gu, Yuantong; Bilic, Ante; Zhang, Haijun; Chen, Zhongfang; Du, Aijun

    2016-02-01

    Single layered transition metal dichalcogenides have attracted tremendous research interest due to their structural phase diversities. By using a global optimization approach, we have discovered a new phase of transition metal dichalcogenides (labelled as T''), which is confirmed to be energetically, dynamically and kinetically stable by our first-principles calculations. The new T'' MoS2 phase exhibits an intrinsic quantum spin Hall (QSH) effect with a nontrivial gap as large as 0.42 eV, suggesting that a two-dimensional (2D) topological insulator can be achieved at room temperature. Most interestingly, there is a topological phase transition simply driven by a small tensile strain of up to 2%. Furthermore, all the known MX2 (M = Mo or W; X = S, Se or Te) monolayers in the new T'' phase unambiguously display similar band topologies and strain controlled topological phase transitions. Our findings greatly enrich the 2D families of transition metal dichalcogenides and offer a feasible way to control the electronic states of 2D topological insulators for the fabrication of high-speed spintronics devices.Single layered transition metal dichalcogenides have attracted tremendous research interest due to their structural phase diversities. By using a global optimization approach, we have discovered a new phase of transition metal dichalcogenides (labelled as T''), which is confirmed to be energetically, dynamically and kinetically stable by our first-principles calculations. The new T'' MoS2 phase exhibits an intrinsic quantum spin Hall (QSH) effect with a nontrivial gap as large as 0.42 eV, suggesting that a two-dimensional (2D) topological insulator can be achieved at room temperature. Most interestingly, there is a topological phase transition simply driven by a small tensile strain of up to 2%. Furthermore, all the known MX2 (M = Mo or W; X = S, Se or Te) monolayers in the new T'' phase unambiguously display similar band topologies and strain controlled topological

  19. Study of the deconfinement phase transition in a finite volume with massive particles: Hydrodynamics of the system near the transition

    Energy Technology Data Exchange (ETDEWEB)

    Ghenam, L.; Djoudi, A. Ait El [Laboratoire de Physique des Particules et Physique Statistique, Ecole Normale Superieure - Kouba, B.P. 92, 16050, Vieux Kouba, Algiers (Algeria)

    2012-06-27

    We study the finite size and finite mass effects for the thermal deconfinement phase transition in Quantum Chromodynamics (QCD), using a simple model of coexistence of hadronic (H) gas and quark-gluon plasma (QGP) phases in a finite volume. We consider the equations of state of the two phases with the QGP containing two massless u and d quarks and massive s quarks, and a hadronic gas of massive pions, and we probe the system near the transition. For this, we examine the behavior of the most important hydrodynamical quantities describing the system, at a vanishing chemical potential ({mu}= 0), with temperature and energy density.

  20. Spin-current probe for phase transition in an insulator

    National Research Council Canada - National Science Library

    Qiu, Zhiyong; Li, Jia; Hou, Dazhi; Arenholz, Elke; N'Diaye, Alpha T; Tan, Ali; Uchida, Ken-Ichi; Sato, Koji; Okamoto, Satoshi; Tserkovnyak, Yaroslav; Qiu, Z Q; Saitoh, Eiji

    2016-01-01

    .... Experimentally, the spin fluctuation is found transcribed onto scattering intensity in the neutron-scattering process, which is represented by dynamical magnetic susceptibility and maximized at phase transitions...

  1. Magnetism and phase transitions in LaCoO3

    Energy Technology Data Exchange (ETDEWEB)

    Belanger, David P [University of California, Santa Cruz; Durand, Alice M [University of California, Santa Cruz; Booth, C [Lawrence Berkeley National Laboratory (LBNL); Ye, Feng [ORNL; Chi, Songxue [ORNL; Fernandez-Baca, Jaime A [ORNL; Bhat, M [Castilleja School

    2013-01-01

    Neutron scattering and magnetometry measurements have been used to study phase transitions in LaCoO3 (LCO). For H 100 Oe, evidence for a ferromagnetic (FM) transition is observed at Tc 87 K. For 1 kOe H 60 kOe, no transition is apparent. For all H, Curie Weiss analysis shows predominantly antiferromagnetic (AFM) interactions for T > Tc, but the lack of long-range AFM order indicates magnetic frustration. We argue that the weak ferromagnetism in bulk LCO is induced by lattice strain, as is the case with thin films and nanoparticles. The lattice strain is present at the bulk surfaces and at the interfaces between the LCO and a trace cobalt oxide phase. The ferromagnetic ordering in the LCO bulk is strongly affected by the Co O Co angle ( ), in agreement with recent band calculations which predict that ferromagnetic long-range order can only take place above a critical value, C. Consistent with recent thin film estimations, we find C D 162:8. For > C, we observe power-law behavior in the structural parameters. decreases with T until the critical temperature, To 37 K; below To the rate of change becomes very small. For T < To, FM order appears to be confined to regions close to the surfaces, likely due to the lattice strain keeping the local Co O Co angle above C.

  2. Magnetic Phase Transitions in NdCoAsO

    Energy Technology Data Exchange (ETDEWEB)

    McGuire, Michael A [ORNL; Gout, Delphine J [ORNL; Garlea, Vasile O [ORNL; Sefat, A. S. [Oak Ridge National Laboratory (ORNL); Sales, Brian C [ORNL; Mandrus, David [ORNL

    2010-01-01

    NdCoAsO undergoes three magnetic phase transitions below room temperature. Here we report the results of our experimental investigation of this compound, including determination of the crystal and magnetic structures using powder neutron diffraction, as well as measurements of electrical resistivity, thermal conductivity, Seebeck coefficient, magnetization, and heat capacity. These results show that upon cooling a ferromagnetic state emerges near 69 K with a small saturation moment of -0.2{micro}{sub B}, likely on Co atoms. At 14 K the material enters an antiferromagnetic state with propagation vector (0 0 1/2) and small ordered moments (-0.4{micro}{sub B}) on Co and Nd. Near 3.5 K a third transition is observed, and corresponds to the antiferromagnetic ordering of larger moments on Nd, with the same propagation vector. The ordered moment on Nd reaches 1.39(5){micro}{sub B} at 300 mK. Anomalies in the magnetization, electrical resistivity, and heat capacity are observed at all three magnetic phase transitions.

  3. Size reduction effect on the critical behavior near the paramagnetic to ferromagnetic phase transition temperature in La0.9Sr0.1MnO3 nanoparticles

    Science.gov (United States)

    Baaziz, H.; Tozri, A.; Dhahri, E.; Hlil, E. K.

    2015-04-01

    The critical behavior of La0.9Sr0.1MnO3 nanoparticles, annealed at different temperatures (H6, H8, H10 and H12 annealed at 600 °C, 800 °C, 1000 °C, 1200 °C, respectively), has been investigated by magnetization measurements. Indeed, the magnetic data indicate that the compound exhibits a continuous (second-order) paramagnetic (PM) to ferromagnetic (FM) phase transition. The critical exponents are estimated by various techniques such as the Modified Arrott plot, Kouvel-Fisher plot and critical isotherm technique. Compared to standard models, the critical exponent values determined in our work are close to those expected for the mean-field model (with β=0.5, γ=1, and δ=3) (H8, H10, and H12). Concerning the sample having a smaller crystallite size (H6), the obtained values of the critical exponents β and δ are similar to those predicted by the mean-field model. However, the value of γ shows a (3D) Heisenberg model-like. This behavior, which is quite new and surprising, shows that the reduction of grain size strongly influences the universality class. Moreover, the decrease of the critical exponents (β, γ, δ) with the increase of grain size has been explained by crossover phenomenon. This result and the other obtained values are explained taking into account the contribution of uncompensated spins at the surface, strain anisotropies, and noncollinear magnetic ordering.

  4. Tension induced phase transitions in biomimetic fluid membranes

    Science.gov (United States)

    Shapiro, Marc; Vlahovska, Petia

    2012-11-01

    Membranes in eukaryotic cells are mixtures of hundreds of lipid species. The lipid diversity enables membranes to phase separate and form domains, called rafts, which play a critical role in cell functions such as signaling and trafficking. The phase transitions underlying raft formation have been extensively studied as a function of temperature and composition. However, the third dimension of the phase diagram, i.e., the tension (2D pressure), is still unexplored because membrane tension is difficult to control and quantify. To overcome this challenge, we develop two approaches, capillary micromechanics and electrodeformation, in which the tension is regulated by the area dilation accompanying deformation of a vesicle (a closed membrane). The first technique consists of forcing an initially quasi-spherical vesicle through a tapered glass microcapillary, while the second method utilizes uniform electric fields to deform the vesicle into an ellipsoid. Domains are visualized using a fluorescent dye, which preferentially partitions in one of the phases. The experimental results suggest that the miscibility temperature (at which domains form in an initially homogeneous membrane) increases with applied tension. Domain motions and coarsening are also investigated.

  5. Absence of phase transitions in an oxygen stoichiometric cobaltite, YBaCo4O7

    Directory of Open Access Journals (Sweden)

    R. Nithya

    2013-02-01

    Full Text Available Polycrystalline YBaCo4O7 compounds are synthesized by solid state reaction in air atmosphere. X-ray powder diffraction at room temperature indicates its single phase nature. Rietveld refinement of X-ray diffraction data shows distortions in bond lengths in the cobalt-oxygen tetrahedra. Electrical resistivity of YBaCo4O7 suggests a variable range hopping type of conductivity from 80 K up to room temperature. Raman scattering spectra exhibit several broad phonon modes at ambient temperature. Raman spectroscopic measurements are carried out as a function of temperature to look for any structural phase transitions from 80 to 823 K. Raman scattering results show no phase transitions, supporting low temperature conductivity measurements. From temperature variation of Raman spectra, it is found that the structure is stable in the temperature range of present study.

  6. Pressure induced phase transitions in ceramic compounds containing tetragonal zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Sparks, R.G.; Pfeiffer, G.; Paesler, M.A.

    1988-12-01

    Stabilized tetragonal zirconia compounds exhibit a transformation toughening process in which stress applied to the material induces a crystallographic phase transition. The phase transition is accompanied by a volume expansion in the stressed region thereby dissipating stress and increasing the fracture strength of the material. The hydrostatic component of the stress required to induce the phase transition can be investigated by the use of a high pressure technique in combination with Micro-Raman spectroscopy. The intensity of Raman lines characteristic for the crystallographic phases can be used to calculate the amount of material that has undergone the transition as a function of pressure. It was found that pressures on the order of 2-5 kBar were sufficient to produce an almost complete transition from the original tetragonal to the less dense monoclinic phase; while a further increase in pressure caused a gradual reversal of the transition back to the original tetragonal structure.

  7. Metamagnetic phase transition of the antiferromagnetic Heisenberg icosahedron.

    Science.gov (United States)

    Schröder, Christian; Schmidt, Heinz-Jürgen; Schnack, Jürgen; Luban, Marshall

    2005-05-27

    The observation of hysteresis effects in single molecule magnets like Mn12-acetate has initiated ideas of future applications in storage technology. The appearance of a hysteresis loop in such compounds is an outcome of their magnetic anisotropy. In this Letter we report that magnetic hysteresis occurs in a spin system without any anisotropy, specifically where spins mounted on the vertices of an icosahedron are coupled by antiferromagnetic isotropic nearest-neighbor Heisenberg interaction giving rise to geometric frustration. At T = 0 this system undergoes a first-order metamagnetic phase transition at a critical field Bc between two distinct families of ground state configurations. The metastable phase of the system is characterized by a temperature and field dependent survival probability distribution.

  8. Ab-initio Based Analytical Evaluation of Entropy in Magnetocaloric Materials with First Order Phase Transitions

    Science.gov (United States)

    Piazzi, Marco; Zemen, Jan; Basso, Vittorio

    We combine spin polarised density functional theory and thermodynamic mean field theory to describe the phase transitions of antiperovskite manganese nitrides. We find that the inclusion of the localized spin contribution to the entropy, evaluated through mean field theory, lowers the transition temperatures. Furthermore, we show that the electronic entropy leads to first order phase transitions in agreement with experiments whereas the localized spin contribution adds second order character to the transition. We compare our predictions to available experimental data to assess the validity of the assumptions underpinning our multilevel modelling.

  9. Quantum phase transition in strongly correlated many-body system

    Science.gov (United States)

    You, Wenlong

    The past decade has seen a substantial rejuvenation of interest in the study of quantum phase transitions (QPTs), driven by experimental advance on the cuprate superconductors, the heavy fermion materials, organic conductors, Quantum Hall effect, Fe-As based superconductors and other related compounds. It is clear that strong electronic interactions play a crucial role in the systems of current interest, and simple paradigms for the behavior of such systems near quantum critical points remain unclear. Furthermore, the rapid progress in Feshbach resonance and optical lattice provides a flexible platform to study QPT. Quantum Phase Transition (QPT) describes the non-analytic behaviors of the ground-state properties in a many-body system by varying a physical parameter at absolute zero temperature - such as magnetic field or pressure, driven by quantum fluctuations. Such quantum phase transitions can be first-order phase transition or continuous. The phase transition is usually accompanied by a qualitative change in the nature of the correlations in the ground state, and describing this change shall clearly be one of our major interests. We address this issue from three prospects in a few strong correlated many-body systems in this thesis, i.e., identifying the ordered phases, studying the properties of different phases, characterizing the QPT points. In chapter 1, we give an introduction to QPT, and take one-dimensional XXZ model as an example to illustrate the QPT therein. Through this simple example, we would show that when the tunable parameter is varied, the system evolves into different phases, across two quantum QPT points. The distinct phases exhibit very different behaviors. Also a schematic phase diagram is appended. In chapter 2, we are engaged in research on ordered phases. Originating in the work of Landau and Ginzburg on second-order phase transition, the spontaneous symmetry breaking induces nonzero expectation of field operator, e.g., magnetization M

  10. Van der Waals phase transition in the framework of holography

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Xiao-Xiong, E-mail: xxzeng@itp.ac.cn [State School of Material Science and Engineering, Chongqing Jiaotong University, Chongqing 400074 (China); Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190 (China); Li, Li-Fang, E-mail: lilf@itp.ac.cn [State Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing 100190 (China)

    2017-01-10

    Phase structure of the quintessence Reissner–Nordström–AdS black hole is probed by the nonlocal observables such as holographic entanglement entropy and two point correlation function. Our result shows that, as the case of the thermal entropy, both the observables exhibit the Van der Waals-like phase transition. To reinforce this conclusion, we further check the equal area law for the first order phase transition and critical exponent of the heat capacity for the second order phase transition. We also discuss the effect of the state parameter on the phase structure of the nonlocal observables.

  11. Coexistent physics of massive black holes in the phase transitions

    CERN Document Server

    Zhang, Ming

    2016-01-01

    The coexistent physics of de Rham-Gabada-dze-Tolley (dRGT) massive black holes and holographic massive black holes is investigated in the extended phase space where the cosmological constant is viewed as pressure. Van der Waals like phase transitions are found for both of them. Coexistent curves of reduced pressure and reduced temperature are found to be different from that of RN-AdS black holes. Coexistent curves of reduced Gibbs free energy and reduced pressure show that Gibbs free energy in the canonical ensemble decreases monotonically with the increasing pressure. The concept number density is introduced to study the coexistent physics. It is uncovered that with the increasing pressure, the number densities of small black holes (SBHs) and large black holes (LBHs) change monotonically in the contrary directions till finally reaching the same value at the critical points of the phase transitions. In other words, with the increasing pressure the number density differences between SBHs and LBHs decrease mono...

  12. Low temperature magnetic transition and high temperature oxidation in INCONEL alloy 718

    Energy Technology Data Exchange (ETDEWEB)

    Seehra, M.S.; Babu, V.S. [Physics Department, West Virginia University, Morgantown, West Virginia 26506-6315 (United States)

    1996-05-01

    X-ray diffraction and temperature dependent (5 K{endash}380 K) magnetic measurements have been carried out in INCONEL 718 superalloy before and after high temperature aging treatments (INCONEL is a trademark of the INCO family of companies). The nominal composition of this alloy is Ni (52.5{percent}), Cr (19.0{percent}), Fe (18.5{percent}), Nb (5.1{percent}), Mo (3.0{percent}), Ti (0.9{percent}), Al (0.5{percent}), Cu (0.15{percent}) and C (0.08{percent}) and it yields an x-ray diffraction pattern consisting of a fcc phase with {ital a}=3.5987 (3) A and an orthorhombic phase associated with {delta}{minus}Ni{sub 3}Nb. It is concluded that the fcc pattern is due to both the {gamma} austenitic phase and {gamma}{prime} Ni{sub 3}(Al,Ti) phase of alloy 718. The standard annealing and aging treatment carried out in air at temperatures between 621 and 982{degree}C produces surface oxides (Cr,Fe){sub 2}O{sub 3} and FeNbO{sub 4} (which are easily removed by etching and polishing) and contracts the lattice. Magnetic measurements show a distinct phase transition at {ital T}{sub {ital c}}=14 K, which has been attributed to the {gamma}{prime}{minus}Ni{sub 3}(Al,Ti) phase by the process of elimination and by observing that it has most of the characteristics of the weak itinerant ferromagnet Ni{sub 74.5}Al{sub 25.5}. This transition may have some effects on the cryogenic applications of this alloy. {copyright} {ital 1996 Materials Research Society.}

  13. Scaling of geometric quantum discord close to a topological phase transition.

    Science.gov (United States)

    Shan, Chuan-Jia; Cheng, Wei-Wen; Liu, Ji-Bing; Cheng, Yong-Shan; Liu, Tang-Kun

    2014-03-26

    Quantum phase transition is one of the most interesting aspects in quantum many-body systems. Recently, geometric quantum discord has been introduced to signature the critical behavior of various quantum systems. However, it is well-known that topological quantum phase transition can not be described by the conventional Landau's symmetry breaking theory, and thus it is unknown that whether previous study can be applicable in this case. Here, we study the topological quantum phase transition in Kitaev's 1D p-wave spinless quantum wire model in terms of its ground state geometric quantum discord. The derivative of geometric quantum discord is nonanalytic at the critical point, in both zero temperature and finite temperature cases. The scaling behavior and the universality are verified numerically. Therefore, our results clearly show that all the key ingredients of the topological phase transition can be captured by the nearest neighbor and long-range geometric quantum discord.

  14. ATLAS Transition Region Upgrade at Phase-1

    CERN Document Server

    Song, H; The ATLAS collaboration

    2014-01-01

    This report presents the L1 Muon trigger transition region (1.0<|ƞ|<1.3) upgrade of ATLAS Detector at phase-1. The high fake trigger rate in the Endcap region 1.0<|ƞ|<2.4 would become a serious problem for the ATLAS L1 Muon trigger system at high luminosity. For the region 1.3<|ƞ|<2.4, covered by the Small Wheel, ATLAS is enhancing the present muon trigger by adding local fake rejection and track angle measurement capabilities. To reduce the rate in the remaining ƞ interval it has been proposed a similar enhancement by adding at the edge of the inner barrel a structure of 3-layers RPCs of a new generation. These RPCs will be based on a thinner gas gap and electrodes with respect to the ATLAS standards, a new high performance Front End, integrating fast TDC capabilities, and a new low profile and light mechanical structure allowing the installation in the tiny space available.This design effectively suppresses fake triggers by making the coincidence with both end-cap and interaction point...

  15. Phase Transition and Uniqueness of Levelset Percolation

    Science.gov (United States)

    Broman, Erik; Meester, Ronald

    2017-06-01

    The main purpose of this paper is to introduce and establish basic results of a natural extension of the classical Boolean percolation model (also known as the Gilbert disc model). We replace the balls of that model by a positive non-increasing attenuation function l:(0,\\infty ) → [0,\\infty ) to create the random field Ψ (y)=\\sum _{x\\in η }l(|x-y|), where η is a homogeneous Poisson process in {\\mathbb {R}}^d. The field Ψ is then a random potential field with infinite range dependencies whenever the support of the function l is unbounded. In particular, we study the level sets Ψ _{\\ge h}(y) containing the points y\\in {\\mathbb {R}}^d such that Ψ (y)\\ge h. In the case where l has unbounded support, we give, for any d\\ge 2, a necessary and sufficient condition on l for Ψ _{\\ge h}(y) to have a percolative phase transition as a function of h. We also prove that when l is continuous then so is Ψ almost surely. Moreover, in this case and for d=2, we prove uniqueness of the infinite component of Ψ _{\\ge h} when such exists, and we also show that the so-called percolation function is continuous below the critical value h_c.

  16. Phase transitions in models of human cooperation

    Science.gov (United States)

    Perc, Matjaž

    2016-08-01

    If only the fittest survive, why should one cooperate? Why should one sacrifice personal benefits for the common good? Recent research indicates that a comprehensive answer to such questions requires that we look beyond the individual and focus on the collective behavior that emerges as a result of the interactions among individuals, groups, and societies. Although undoubtedly driven also by culture and cognition, human cooperation is just as well an emergent, collective phenomenon in a complex system. Nonequilibrium statistical physics, in particular the collective behavior of interacting particles near phase transitions, has already been recognized as very valuable for understanding counterintuitive evolutionary outcomes. However, unlike pairwise interactions among particles that typically govern solid-state physics systems, interactions among humans often involve group interactions, and they also involve a larger number of possible states even for the most simplified description of reality. Here we briefly review research done in the realm of the public goods game, and we outline future research directions with an emphasis on merging the most recent advances in the social sciences with methods of nonequilibrium statistical physics. By having a firm theoretical grip on human cooperation, we can hope to engineer better social systems and develop more efficient policies for a sustainable and better future.

  17. Size-driven quantum phase transitions.

    Science.gov (United States)

    Bausch, Johannes; Cubitt, Toby S; Lucia, Angelo; Perez-Garcia, David; Wolf, Michael M

    2018-01-02

    Can the properties of the thermodynamic limit of a many-body quantum system be extrapolated by analyzing a sequence of finite-size cases? We present models for which such an approach gives completely misleading results: translationally invariant, local Hamiltonians on a square lattice with open boundary conditions and constant spectral gap, which have a classical product ground state for all system sizes smaller than a particular threshold size, but a ground state with topological degeneracy for all system sizes larger than this threshold. Starting from a minimal case with spins of dimension 6 and threshold lattice size [Formula: see text], we show that the latter grows faster than any computable function with increasing local spin dimension. The resulting effect may be viewed as a unique type of quantum phase transition that is driven by the size of the system rather than by an external field or coupling strength. We prove that the construction is thermally robust, showing that these effects are in principle accessible to experimental observation.

  18. T-p phase diagrams and the barocaloric effect in materials with successive phase transitions

    Science.gov (United States)

    Gorev, M. V.; Bogdanov, E. V.; Flerov, I. N.

    2017-09-01

    An analysis of the extensive and intensive barocaloric effect (BCE) at successive structural phase transitions in some complex fluorides and oxyfluorides was performed. The high sensitivity of these compounds to a change in the chemical pressure allows one to vary the succession and parameters of the transformations (temperature, entropy, baric coefficient) over a wide range and obtain optimal values of the BCE. A comparison of different types of schematic T-p phase diagrams with the complicated T( p) dependences observed experimentally shows that in some ranges of temperature and pressure the BCE in compounds undergoing successive transformations can be increased due to a summation of caloric effects associated with distinct phase transitions. The maximum values of the extensive and intensive BCE in complex fluorides and oxyfluorides can be realized at rather low pressure (0.1-0.3 GPa). In a narrow temperature range around the triple points conversion from conventional BCE to inverse BCE is observed, which is followed by a gigantic change of both \\vertΔ S_BCE\\vert and \\vertΔ T_AD\\vert .

  19. Dissipative phases across the superconductor-to-insulator transition.

    Science.gov (United States)

    Couëdo, F; Crauste, O; Drillien, A A; Humbert, V; Bergé, L; Marrache-Kikuchi, C A; Dumoulin, L

    2016-10-27

    Competing phenomena in low dimensional systems can generate exotic electronic phases, either through symmetry breaking or a non-trivial topology. In two-dimensional (2D) systems, the interplay between superfluidity, disorder and repulsive interactions is especially fruitful in this respect although both the exact nature of the phases and the microscopic processes at play are still open questions. In particular, in 2D, once superconductivity is destroyed by disorder, an insulating ground state is expected to emerge, as a result of a direct superconductor-to-insulator quantum phase transition. In such systems, no metallic state is theoretically expected to survive to the slightest disorder. Here we map out the phase diagram of amorphous NbSi thin films as functions of disorder and film thickness, with two metallic phases in between the superconducting and insulating ones. These two dissipative states, defined by a resistance which extrapolates to a finite value in the zero temperature limit, each bear a specific dependence on disorder. We argue that they originate from an inhomogeneous destruction of superconductivity, even if the system is morphologically homogeneous. Our results suggest that superconducting fluctuations can favor metallic states that would not otherwise exist.

  20. The Influence of the Perovskite-post Perovskite Phase Transition and the Spin Transition in Iron on Layered Mantle Convection

    Science.gov (United States)

    Shahnas, H.; Peltier, W.

    2008-12-01

    The interaction between the endothermic phase transition(s) at the base of the transition zone and both subducting lithosphere and uprising plumes originating from the deep mantle remains a key issue in geodynamics. The rates of both heat and mass transfer between the upper and the lower mantle are controlled by this interaction. Factors that govern its impact include not only the Clapeyron slope of the transition but also the contrast in physical properties across the interface, notably viscosity. Mass transfer across the level of the endothermic transition at 660 km depth is inhibited by a viscosity increase. Evidence for such inhibition derives from several lines of argument. For example, seismic tomographic images of downgoing slabs trapped in the transition region above 660 km depth are common. We will describe a sequence of new simulations of convective mixing which include the most accurate representations of the temperature and pressure dependence of thermal conductivity, thermal expansively and viscosity as well as the presence of the near surface exothermic and endothermic traditional phase transitions that bracket the transition zone as well as the Perovskite-post Perovskite (Pv-pPv) deep mantle transition that appears to define the D" layer. In these new models we investigate the influence Pv-pPv transition and the spin transition in iron on mantle dynamics, with a focus upon the permeability to mass transfer of the 660 phase transition. This endothermic transition operating in conjunction with a modest but abrupt viscosity increase at 660 km depth results in an episodic but significant decrease in the radial mass flux. The frequency of mantle avalanches decreases as the viscosity contrast increases and the mass flux in each avalanche becomes more diffuse and less intense.

  1. Electron-phonon coupling and structural phase transitions in early transition metal oxides and chalcogenides

    Science.gov (United States)

    Farley, Katie Elizabeth

    Pronounced nonlinear variation of electrical transport characteristics as a function of applied voltage, temperature, magnetic field, strain, or photo-excitation is usually underpinned by electronic instabilities that originate from the complex interplay of spin, orbital, and lattice degrees of freedom. This dissertation focuses on two canonical materials that show pronounced discontinuities in their temperature-dependent resistivity as a result of electron---phonon and electron---electron correlations: orthorhombic TaS3 and monoclinic VO2. Strong electron-phonon interactions in transition metal oxides and chalcogenides results in interesting structural and electronic phase transitions. The properties of the material can be changed drastically in response to external stimuli such as temperature, voltage, or light. Understanding the influence these interactions have on the electronic structure and ultimately transport characteristics is of utmost importance in order to take these materials from a fundamental aspect to prospective applications such as low-energy interconnects, steep-slope transistors, and synaptic neural networks. This dissertation describes synthetic routes to nanoscale TaS3 and VO2, develops mechanistic understanding of their electronic instabilities, and in the case of the latter system explores modulation of the electronic and structural phase transition via the incorporation of substitutional dopant atoms. We start in chapter 2 with a detailed study of the synthesis and electronic transport properties of TaS3, which undergoes a Peierls' distortion to form a charge density wave. Scaling this material down to the nanometer-sized regime allows for interrogation of single or discrete phase coherent domains. Using electrical transport and broad band noise measurements, the dynamics of pinning/depinning of the charge density wave is investigated. Chapter 3 provides a novel synthetic approach to produce high-edge-density MoS2 nanorods. MoS2 is a

  2. Evidence of a liquid–liquid phase transition in hot dense hydrogen

    OpenAIRE

    Dzyabura, Vasily; Zaghoo, Mohamed; Silvera, Isaac F.

    2013-01-01

    We use pulsed-laser heating of hydrogen at static pressures in the megabar pressure region to search for the plasma phase transition to liquid atomic metallic hydrogen. We heat our samples substantially above the melting line and observe a plateau in a temperature vs. laser power curve that otherwise increases with power. This anomaly in the heating curve appears correlated with theoretical predictions for the plasma phase transition.

  3. Observation of a second order magnetic phase transition in CsFeS2

    Science.gov (United States)

    Sharma, Y. K.; Iannarella, L.; Wagner, F. E.; Taft, C. A.; Furtado, N. C.; Arsenio, T. P.

    1988-12-01

    Mössbauer experiments performed on CsFeS2 at temperatures between 4.2 K and 300 K show that the orthorhombic high temperature phase undergoes a second order magnetic phase transition near 69 K, when the previously reported first order magnetic and structural transition to a triclinic modification near 75 K is suppressed by lattice defects or internal stresses. The saturation values of the hyperfine fields are 19.1 T for the triclinic and 15.5 and 14.1 T for the orthorhombic phase.

  4. Axially engineered metal-insulator phase transition by graded doping VO2 nanowires.

    Science.gov (United States)

    Lee, Sangwook; Cheng, Chun; Guo, Hua; Hippalgaonkar, Kedar; Wang, Kevin; Suh, Joonki; Liu, Kai; Wu, Junqiao

    2013-03-27

    The abrupt first-order metal-insulator phase transition in single-crystal vanadium dioxide nanowires (NWs) is engineered to be a gradual transition by axially grading the doping level of tungsten. We also demonstrate the potential of these NWs for thermal sensing and actuation applications. At room temperature, the graded-doped NWs show metal phase on the tips and insulator phase near the center of the NW, and the metal phase grows progressively toward the center when the temperature rises. As such, each individual NW acts as a microthermometer that can be simply read out with an optical microscope. The NW resistance decreases gradually with the temperature rise, eventually reaching 2 orders of magnitude drop, in stark contrast to the abrupt resistance change in undoped VO2 wires. This novel phase transition yields an extremely high temperature coefficient of resistivity ~10%/K, simultaneously with a very low resistivity down to 0.001 Ω·cm, making these NWs promising infrared sensing materials for uncooled microbolometers. Lastly, they form bimorph thermal actuators that bend with an unusually high curvature, ~900 m(-1)·K(-1) over a wide temperature range (35-80 °C), significantly broadening the response temperature range of previous VO2 bimorph actuators. Given that the phase transition responds to a diverse range of stimuli-heat, electric current, strain, focused light, and electric field-the graded-doped NWs may find wide applications in thermo-opto-electro-mechanical sensing and energy conversion.

  5. Variability in Glycemic Control with Temperature Transitions during Therapeutic Hypothermia

    Directory of Open Access Journals (Sweden)

    Krystal K. Haase

    2017-01-01

    Full Text Available Purpose. Patients treated with therapeutic hypothermia (TH and continuous insulin may be at increased risk of hyperglycemia or hypoglycemia, particularly during temperature transitions. This study aimed to evaluate frequency of glucose excursions during each phase of TH and to characterize glycemic control patterns in relation to survival. Methods. Patients admitted to a tertiary care hospital for circulatory arrest and treated with both therapeutic hypothermia and protocol-based continuous insulin between January 2010 and June 2013 were included. Glucose measures, insulin, and temperatures were collected through 24 hours after rewarming. Results. 24 of 26 patients experienced glycemic excursions. Hyperglycemic excursions were more frequent during initiation versus remaining phases (36.3%, 4.3%, 2.5%, and 4.0%, p=0.002. Hypoglycemia occurred most often during rewarming (0%, 7.7%, 23.1%, and 3.8%, p=0.02. Patients who experienced hypoglycemia had higher insulin doses prior to rewarming (16.2 versus 2.1 units/hr, p=0.03. Glucose variation was highest during hypothermia and trended higher in nonsurvivors compared to survivors (13.38 versus 9.16, p=0.09. Frequency of excursions was also higher in nonsurvivors (32.3% versus 19.8%, p=0.045. Conclusions. Glycemic excursions are common and occur more often in nonsurvivors. Excursions differ by phase but risk of hypoglycemia is increased during rewarming.

  6. Tunable Crystal-to-Crystal Phase Transition in a Cadmium Halide Chain Polymer

    Directory of Open Access Journals (Sweden)

    Ulli Englert

    2011-07-01

    Full Text Available The chain polymer [{Cd(μ-X2py2}1∞] (X = Cl, Br; py = pyridine undergoes a fully reversible phase transition between a monoclinic low-temperature and an orthorhombic high-temperature phase. The transformation can be directly monitored in single crystals and can be confirmed for the bulk by powder diffraction. The transition temperature can be adjusted by tuning the composition of the mixed-halide phase: Transition temperatures between 175 K up to the decomposition of the material at ca. 350 K are accessible. Elemental analysis, ion chromatography and site occupancy refinements from single-crystal X-ray diffraction agree with respect to the stoichiometric composition of the samples.

  7. Structural phase transition and elastic properties of thorium pnictides ...

    Indian Academy of Sciences (India)

    In the present paper we have pointed out the weaknesses of the approach by Aynyas et al [1] to study the structural phase transition and elastic properties of thorium pnictides. The calculated values of phase transition pressure and other elastic properties using the realistic and actual approach are also given and compared ...

  8. Phase transition in a domain-wall lattice

    Science.gov (United States)

    Stolzenberg, M.; Lyuksyutov, I.; Bauer, E.

    1991-12-01

    A new type of phase transition in the domain-wall lattice between the (4×2) and (5×2) structure of Te on Mo(110) is reported. In this phase transition the period of the uniaxial domain-wall lattice remains constant, but domain walls themselves transform in more heavy ones.

  9. Local discontinuous Galerkin methods for phase transition problems

    NARCIS (Netherlands)

    Tian, Lulu

    2015-01-01

    In this thesis we develop a local discontinuous Galerkin (LDG) finite element method to solve mathematical models for phase transitions in solids and fluids. The first model we study is called a viscosity-capillarity (VC) system associated with phase transitions in elastic bars and Van der Waals

  10. Shape change as entropic phase transition: A study using Jarzynski ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 124; Issue 1. Shape change as entropic phase transition: A study using ... Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/jcsc/124/01/0021-0028. Keywords. Fick-Jacobs equation; entropic potental; Jarzynski equality; phase transition.

  11. Electroweak phase transition and some related phenomena–a brief

    Indian Academy of Sciences (India)

    In this article, we give a bird's eye view of the research on electroweak phase transition and some related phenomena, viz., cosmological baryogenesis, electroweak bubble dynamics and generation of gravitationalwaves. Our presentation revolves around the observation that a strong first-order electroweak phase transition ...

  12. High-density QCD phase transitions inside neutron stars: Glitches ...

    Indian Academy of Sciences (India)

    2017-10-09

    Oct 9, 2017 ... ... of different high-density phases and associated phase transitions. We study effectsof density fluctuations during transitions with and without topological defect production and study the effect on pulsar timings due to changing moment of inertia of the star. We also discuss gravitational wave production due ...

  13. Order–disorder phase transitions in thin films described by transverse Ising model

    Directory of Open Access Journals (Sweden)

    Nguyen Tu Niem

    2016-12-01

    Full Text Available The order–disorder phase transition in thin films at finite temperature and zero temperature (quantum phase transition is discussed within the transverse Ising model using molecular field approximation. Experimentally, it is shown that the Curie temperature TC of perovskite PbTiO3 ultra-thin film decreases with decreasing film thickness. We obtain an equation for TC of thin film in external magnetic and transverse fields. Our equation explains well for the case of strong transverse strain field this behaviour.

  14. Phase transitions in Ising models on directed networks.

    Science.gov (United States)

    Lipowski, Adam; Ferreira, António Luis; Lipowska, Dorota; Gontarek, Krzysztof

    2015-11-01

    We examine Ising models with heat-bath dynamics on directed networks. Our simulations show that Ising models on directed triangular and simple cubic lattices undergo a phase transition that most likely belongs to the Ising universality class. On the directed square lattice the model remains paramagnetic at any positive temperature as already reported in some previous studies. We also examine random directed graphs and show that contrary to undirected ones, percolation of directed bonds does not guarantee ferromagnetic ordering. Only above a certain threshold can a random directed graph support finite-temperature ferromagnetic ordering. Such behavior is found also for out-homogeneous random graphs, but in this case the analysis of magnetic and percolative properties can be done exactly. Directed random graphs also differ from undirected ones with respect to zero-temperature freezing. Only at low connectivity do they remain trapped in a disordered configuration. Above a certain threshold, however, the zero-temperature dynamics quickly drives the model toward a broken symmetry (magnetized) state. Only above this threshold, which is almost twice as large as the percolation threshold, do we expect the Ising model to have a positive critical temperature. With a very good accuracy, the behavior on directed random graphs is reproduced within a certain approximate scheme.

  15. Exotic, topological, and many body localized quantum phase transitions

    Science.gov (United States)

    Slagle, Kevin Jacob

    In this thesis we will study recent examples of exotic, topological, and many body localized quantum phase transitions. In Chapter 2 we study the quantum phase transition between the Z2 spin liquid and valence bond solid (VBS) orders on a triangular lattice. We find a possible nematic Z2 spin liquid intermediate phase and predict a continuous 3d XY* transition to the neighboring columnar and resonating-plaquette VBS phases. In Chapter 3 we demonstrate that an extended Kane-Mele Hubbard model on a bilayer honeycomb lattice has two novel quantum phase transitions. The first is a quantum phase transition between the weakly interacting gapless Dirac fermion phase and a strongly interacting fully gapped and symmetric trivial phase, which cannot be described by the standard Gross-Neveu model. The second is a quantum critical point between a quantum spin Hall insulator with spin Sz conservation and the previously mentioned strongly interacting fully gapped phase. We argue that the first quantum phase transition is related to the Z16 classification of the topological superconductor 3He-B phase with interactions, while the second quantum phase transition is a topological phase transition described by a bosonic O(4) nonlinear sigma model field theory with a Theta-term. In Chapter 4 we propose that if the highest and lowest energy eigenstates of a Hamiltonian belong to different SPT phases, then this Hamiltonian can't be fully many body localized. In Chapter 5 we study the disordered XYZ spin chain and its marginally many body localized critical lines, which we find to be characterized by an effective central charge c'=ln2 and continuously varying critical exponents.

  16. Pressure dependence of structural phase transition and superconducting transition in CsI

    CERN Document Server

    Nirmala-Louis, C

    2003-01-01

    The self-consistent band structure calculation for CsI performed both in CsCl and HCP structures using the TB-LMTO method is reported. The equilibrium lattice constant, bulk modulus and the phase-transition pressure at which the compound undergoes structural phase transition from CsCl to HCP are predicted from the total-energy calculations. The band structure, density of states (DOS), electronic charge distributions, metallization and superconducting transition temperature (T sub c) of CsI are obtained as a function of pressure for both the CsCl and HCP structures. It is found that the charge transfer from s and p states to d state causes metallization and superconductivity in CsI. The highest T sub c estimated is 2.11 K and the corresponding pressure is 1.8 Mbar. This value is in agreement with the recent experimental observation. The experimental trend - ''metallization and superconductivity is rather insensitive to the crystal structure of CsI'' - is also confirmed in our work. (Abstract Copyright [2003], ...

  17. Dynamic Off-Equilibrium Transition in Systems Slowly Driven across Thermal First-Order Phase Transitions.

    Science.gov (United States)

    Pelissetto, Andrea; Vicari, Ettore

    2017-01-20

    We study the off-equilibrium behavior of systems with short-range interactions, slowly driven across a thermal first-order transition, where the equilibrium dynamics is exponentially slow. We consider a dynamics that starts in the high-T phase at time t=t_{i}0 in the low-T phase, with a time-dependent temperature T(t)/T_{c}≈1-t/t_{s}, where t_{s} is the protocol time scale. A general off-equilibrium scaling (OS) behavior emerges in the limit of large t_{s}. We check it at the first-order transition of the two-dimensional q-state Potts model with q=20 and 10. The numerical results show evidence of a dynamic transition, where the OS functions show a spinodal-like singularity. Therefore, the general mean-field picture valid for systems with long-range interactions is qualitatively recovered, provided the time dependence is appropriately (logarithmically) rescaled.

  18. High-pressure-induced phase transitions in the ferroelectric bis-thiourea pyridinium iodide inclusion compound

    Energy Technology Data Exchange (ETDEWEB)

    Bilski, P; Bobrowicz-Sarga, L; Czarnecki, P; Maluszynska, H; Wasicki, J [Institute of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznan (Poland); Natkaniec, I [Frank Laboratory of Neutrons Physics, JINR, 141980 Dubna (Russian Federation)

    2008-12-03

    The effect of temperature and pressure on physical properties of the ferroelectric bis-thiourea pyridinium iodide inclusion compound has been studied by dielectric spectroscopy, neutron spectroscopy, neutron powder diffractometry, single crystal x-ray diffraction and nuclear magnetic resonance (NMR). At ambient pressure two structural phase transitions have been revealed: at T{sub 1} = 161 K between phases I and II and at T{sub 2} = 141 K between phases II and III. Phase III with increasing pressure splits into two phases, IIIa and IIIb. The temperatures of the phase transitions T{sub I-II}, T{sub II-IIIa} and T{sub IIIa-IIIb} increase with increasing pressure. The p-T phase diagram constructed for this compound shows two triple points of coordinates 150 K, 100 MPa and 115 K, 100 MPa.

  19. CO2 Capture from Flue Gas by Phase Transitional Absorption

    Energy Technology Data Exchange (ETDEWEB)

    Liang Hu

    2009-06-30

    A novel absorption process called Phase Transitional Absorption was invented. What is the Phase Transitional Absorption? Phase Transitional Absorption is a two or multi phase absorption system, CO{sub 2} rich phase and CO{sub 2} lean phase. During Absorption, CO{sub 2} is accumulated in CO{sub 2} rich phase. After separating the two phases, CO{sub 2} rich phase is forward to regeneration. After regeneration, the regenerated CO{sub 2} rich phase combines CO{sub 2} lean phase to form absorbent again to complete the cycle. The advantage for Phase Transitional Absorption is obvious, significantly saving on regeneration energy. Because CO{sub 2} lean phase was separated before regeneration, only CO{sub 2} rich phase was forward to regeneration. The absorption system we developed has the features of high absorption rate, high loading and working capacity, low corrosion, low regeneration heat, no toxic to environment, etc. The process evaluation shows that our process is able to save 80% energy cost by comparing with MEA process.

  20. Holographic entanglement entropy close to crossover/phase transition in strongly coupled systems

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Shao-Jun, E-mail: sjzhang84@hotmail.com

    2017-03-15

    We investigate the behavior of entanglement entropy in the holographic QCD model proposed by Gubser et al. By choosing suitable parameters of the scalar self-interaction potential, this model can exhibit various types of phase structures: crossover, first order and second order phase transitions. We use entanglement entropy to probe the crossover/phase transition, and find that it drops quickly/suddenly when the temperature approaches the critical point which can be seen as a signal of confinement. Moreover, the critical behavior of the entanglement entropy suggests that we may use it to characterize the corresponding phase structures.

  1. Topological Phase Transitions in Line-nodal Superconductors

    Science.gov (United States)

    Cho, Gil Young; Han, Sangeun; Moon, Eun-Gook

    Fathoming interplay between symmetry and topology of many-electron wave-functions deepens our understanding in quantum nature of many particle systems. Topology often protects zero-energy excitation, and in a certain class, symmetry is intrinsically tied to the topological protection. Namely, unless symmetry is broken, topological nature is intact. We study one specific case of such class, symmetry-protected line-nodal superconductors in three spatial dimensions (3d). Mismatch between phase spaces of order parameter fluctuation and line-nodal fermion excitation induces an exotic universality class in a drastic contrast to one of the conventional ϕ4 theory in 3d. Hyper-scaling violation and relativistic dynamic scaling with unusually large quantum critical region are main characteristics, and their implication in experiments is discussed. For example, continuous phase transition out of line-nodal superconductors has a linear phase boundary in a temperature-tuning parameter phase-diagram. This work was supported by the Brain Korea 21 PLUS Project of Korea Government and KAIST start-up funding.

  2. Concurrent transition of ferroelectric and magnetic ordering near room temperature.

    Science.gov (United States)

    Ko, Kyung-Tae; Jung, Min Hwa; He, Qing; Lee, Jin Hong; Woo, Chang Su; Chu, Kanghyun; Seidel, Jan; Jeon, Byung-Gu; Oh, Yoon Seok; Kim, Kee Hoon; Liang, Wen-I; Chen, Hsiang-Jung; Chu, Ying-Hao; Jeong, Yoon Hee; Ramesh, Ramamoorthy; Park, Jae-Hoon; Yang, Chan-Ho

    2011-11-29

    Strong spin-lattice coupling in condensed matter gives rise to intriguing physical phenomena such as colossal magnetoresistance and giant magnetoelectric effects. The phenomenological hallmark of such a strong spin-lattice coupling is the manifestation of a large anomaly in the crystal structure at the magnetic transition temperature. Here we report that the magnetic Néel temperature of the multiferroic compound BiFeO(3) is suppressed to around room temperature by heteroepitaxial misfit strain. Remarkably, the ferroelectric state undergoes a first-order transition to another ferroelectric state simultaneously with the magnetic transition temperature. Our findings provide a unique example of a concurrent magnetic and ferroelectric transition at the same temperature among proper ferroelectrics, taking a step toward room temperature magnetoelectric applications.

  3. Phase transition in vortex system in Bi2212:Pb monocrystal

    CERN Document Server

    Uspenskaya, L S; Rakhmanov, A L

    2002-01-01

    Penetration of the magnetic flux into the (Bi sub 0 sub . sub 8 sub 4 Pb sub 0 sub . sub 1 sub 6) sub 2 sub . sub 2 Sr sub 2 CaCu sub 2 O sub 8 high-temperature superconductor monocrystal is studied thorough the magnetooptical method in the crossed magnetic fields. It is shown that the magnetic flux penetration in the low-temperature areas is anisotropic: it moves primarily along the magnetic field, applied in the sample plane, and this anisotropy grows with the temperature growth. At the temperature of T sub m = 54 +- 2 K there takes place sharp change in the character of the magnetic field penetration into the superconductor, whereby the direction of the flux motion discontinues to be dependent on the direction and value of the magnetic field applied in the sample plane. This effect is interpreted within the frames of representations on the phase transition in the vortex system connected with a sharp decrease in the correlations of the vortex position in the different CuO-planes

  4. Boundary-field-driven control of discontinuous phase transitions on hyperbolic lattices.

    Science.gov (United States)

    Lee, Yoju; Verstraete, Frank; Gendiar, Andrej

    2016-08-01

    The multistate Potts models on two-dimensional hyperbolic lattices are studied with respect to various boundary effects. The free energy is numerically calculated using the corner transfer matrix renormalization group method. We analyze phase transitions of the Potts models in the thermodynamic limit with respect to contracted boundary layers. A false phase transition is present even if a couple of the boundary layers are contracted. Its significance weakens, as the number of the contracted boundary layers increases, until the correct phase transition (deep inside the bulk) prevails over the false one. For this purpose, we derive a thermodynamic quantity, the so-called bulk excess free energy, which depends on the contracted boundary layers and memorizes additional boundary effects. In particular, the magnetic field is imposed on the outermost boundary layer. While the boundary magnetic field does not affect the second-order phase transition in the bulk if suppressing all the boundary effects on the hyperbolic lattices, the first-order (discontinuous) phase transition is significantly sensitive to the boundary magnetic field. Contrary to the phase transition on the Euclidean lattices, the discontinuous phase transition on the hyperbolic lattices can be continuously controlled (within a certain temperature coexistence region) by varying the boundary magnetic field.

  5. High pressure structural phase transitions of PbPo

    Energy Technology Data Exchange (ETDEWEB)

    Bencherif, Y.; Boukra, A. [Departement de Physique, Faculte des Sciences, Universite de Mostaganem (Algeria); Departement de Physique, Universite des Sciences et de la Technologie d' Oran, USTO, Oran (Algeria); Zaoui, A., E-mail: azaoui@polytech-lille.fr [Universite Lille Nord de France, LGCgE (EA 4515) Lille1, Polytech' Lille, Cite Scientifique, Avenue Paul Langevin, 59655 Villeneuve D' Ascq Cedex (France); Ferhat, M. [Departement de Physique, Universite des Sciences et de la Technologie d' Oran, USTO, Oran (Algeria)

    2012-09-01

    First-principles calculations have been performed to investigate the high pressure phase transitions and dynamical properties of the less known lead polonium compound. The calculated ground state parameters for the NaCl phase show good agreement with the experimental data. The obtained results show that the intermediate phase transition for this compound is the orthorhombic Pnma phase. The PbPo undergoes from the rocksalt to Pnma phase at 4.20 GPa. Further structural phase transition from intermediate to CsCl phase has been found at 8.5 GPa. In addition, phonon dispersion spectra were derived from linear-response to density functional theory. In particular, we show that the dynamical properties of PbPo exhibit some peculiar features compared to other III-V compounds. Finally, thermodynamics properties have been also addressed from quasiharmonic approximation.

  6. Nonequilibrium topological phase transitions in two-dimensional optical lattices

    Science.gov (United States)

    Nakagawa, Masaya; Kawakami, Norio

    2014-01-01

    Recently, concepts of topological phases of matter are extended to nonequilibrium systems, especially periodically driven systems. In this paper, we construct an example which shows nonequilibrium topological phase transitions using ultracold fermions in optical lattices. We show that the Rabi oscillation has the possibility to induce nonequilibrium topological phases which are classified into time-reversal-invariant topological insulators for a two-orbital model of alkaline-earth-metal atoms. Furthermore, we study the nonequilibrium topological phases using time-dependent Schrieffer-Wolff-type perturbation theory, and we obtain an analytical expression to describe the topological phase transitions from a high-frequency limit of external driving fields.

  7. Patterns, dynamics and phase transitions in Ising ferromagnet driven by propagating magnetic field wave

    Science.gov (United States)

    Acharyya, Muktish

    2015-09-01

    The nonequilibrium behaviours of kinetic Ising ferromagnet driven by a propagating magnetic field wave have been studied by Monte Carlo simulation. Two types of propagating magnetic field waves are used here. Namely, the plane wave and the spherical wave. For plane propagating wave passing through the Ising ferromagnet, system undergoes a phase transition from a pinned phase to a propagating phase, as the temperature increases. The transition temperature is found to depend on the amplitude of the propagating magnetic field. A phase boundary is drawn in the plane described by the temperature of the system and amplitude of the propagating field. On the other hand, the nonequilibrium behaviours shown by the Ising ferromagnet driven by spherical magnetic field wave, are different. Here, the system exists in three different dynamical phases. The low temperature pinned phase, the intermediate temperature centrally localised breathing phase and the high temperature extended spreading phase. Here also, the transition temperatures are observed to depend upon the amplitude of the propagating magnetic field wave. The phase boundaries are drawn in the plane represented by temperature of the system and the amplitude of the propagating magnetic field wave. The two boundaries merge at the Onsager value of equilibrium critical temperature in the limit of vanishingly small amplitude of the propagating magnetic field. This article is mainly a review of earlier works and is based on the invited lecture delivered in the conference STATPHYSKOLKATAVIII, held at SNBNCBS, Kolkata, India in December 1-5, 2014. This article is dedicated to Prof. H. Nishimori on the occasion of his 60th birthday.

  8. Ramp-Reversal Memory and Phase-Boundary Scarring in Transition Metal Oxides.

    Science.gov (United States)

    Vardi, Naor; Anouchi, Elihu; Yamin, Tony; Middey, Srimanta; Kareev, Michael; Chakhalian, Jak; Dubi, Yonatan; Sharoni, Amos

    2017-06-01

    Transition metal oxides are complex electronic systems that exhibit a multitude of collective phenomena. Two archetypal examples are VO2 and NdNiO3 , which undergo a metal-insulator phase transition (MIT), the origin of which is still under debate. Here this study reports the discovery of a memory effect in both systems, manifested through an increase of resistance at a specific temperature, which is set by reversing the temperature ramp from heating to cooling during the MIT. The characteristics of this ramp-reversal memory effect do not coincide with any previously reported history or memory effects in manganites, electron-glass or magnetic systems. From a broad range of experimental features, supported by theoretical modelling, it is found that the main ingredients for the effect to arise are the spatial phase separation of metallic and insulating regions during the MIT and the coupling of lattice strain to the local transition temperature of the phase transition. We conclude that the emergent memory effect originates from phase boundaries at the reversal temperature leaving "scars" in the underlying lattice structure, giving rise to a local increase in the transition temperature. The universality and robustness of the effect shed new light on the MIT in complex oxides. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Crystal lattice and phase transitions in Na4TiP2O9 (NTP) and Na4.5FeP2O8(O,F) (NFP) superionic conductors as a function of high pressures and temperatures.

    Science.gov (United States)

    Maximov; Sirota; Werner; Schulz

    1999-06-01

    The lattice dynamics of Na(4)TiP(2)O(9) (tetrasodium titanium diphosphorus nonaoxide, NTP) and Na(4.5)FeP(2)O(8)(O,F) (nonasodium diiron tetraphosphorus difluoride octadecaoxide, NFP) crystals, which are superionic conductors with Na(+)-ion conductivity, were studied under high pressures. Lattice constants as a function of hydrostatic pressure were measured on a four-circle diffractometer using a high-pressure cell with diamond anvils. At 1.78 +/- 0.15 GPa NTP undergoes a reversible phase transition from the modulated monoclinic (pseudo-orthorhombic) modification which is stable under atmospheric conditions. A similar phase transition in NTP is observed at 523 K. For NFP, it may be assumed that at least three phase transitions occur when the pressure increases from atmospheric to 12 GPa, at 1.39 +/- 0.08, 4.52 +/- 0.32, and 6.02 +/- 0.02 GPa, as concluded from the change in the unit-cell parameters and in the color of the crystals: the color changes from ginger (dark orange) to pink at ~1.5-2.0 GPa pressure and to violet at ~6.0 GPa.

  10. Polarons and Mobile Impurities Near a Quantum Phase Transition

    Science.gov (United States)

    Shadkhoo, Shahriar

    derives the effective Euclidean action from the classical equation of motion. We calculate the effective mass of the polaron in the model polar liquid at zero and finite temperatures. The self-trapping transition of this polaron turns out to be discontinuous in certain regions of the phase diagram. In order to systematically investigate the role of quantum fluctuations on the polaron properties, we adopt a quantum field theory which supports nearly-critical local modes: the quantum Landau-Brazovskii (QLB) model, which exhibits fluctuation-induced first order transition (weak crystallization). In the vicinity of the phase transition, the quantum fluctuations are strongly correlated; one can in principle tune the strength of these fluctuations, by adjusting the parameters close to or away from the transition point. Furthermore, sufficiently close to the transition, the theory accommodates "soliton'' solutions, signaling the nonlinear response of the system. Therefore, the model seems to be a promising candidate for studying the effects of strong quantum fluctuations and also failure of linear response theory, in the polaron problem. We observe that at zero temperature, and away from the Brazovskii transition where the linear response approximation is valid, the localization transition of the polaron is discontinuous. Upon enhancing fluctuations---of either thermal or quantum nature---the gap of the effective mass closes at distinct second-order critical points. Sufficiently close to the Brazovskii transition where the nonlinear contributions of the field are significantly large, a new state appears in addition to extended and self-trapped polarons: an impurity-induced soliton. We interpret this as the break-down of linear response, reminiscent of what we observe in a polar liquid. Quantum LB model has been proposed to be realizable in ultracold Bose gases in cavities. We thus discuss the experimental feasibility, and propose a setup which is believed to exhibit the

  11. Symmetry protected topological phases in spin-1 ladders and their phase transitions

    OpenAIRE

    Chen, Ji-Yao; Liu, Zheng-Xin

    2015-01-01

    We study two-legged spin-1 ladder systems with $D_2\\times \\sigma$ symmetry group, where $D_2$ is discrete spin rotational symmetry and $\\sigma$ means interchain reflection symmetry. The system has one trivial phase and seven nontrivial symmetry protected topological (SPT) phases. We construct Hamiltonians to realize all of these SPT phases and study the phase transitions between them. Our numerical results indicate that there is no direct continuous transition between any two SPT phases we st...

  12. Magnetism and phase transitions in LaCoO3.

    Science.gov (United States)

    Durand, A M; Belanger, D P; Booth, C H; Ye, F; Chi, S; Fernandez-Baca, J A; Bhat, M

    2013-09-25

    Neutron scattering and magnetometry measurements have been used to study phase transitions in LaCoO3 (LCO). For H ≤ 100 Oe, evidence for a ferromagnetic (FM) transition is observed at Tc ≈ 87 K. For 1 kOe ≤ H ≤ 60 kOe, no transition is apparent. For all H, Curie-Weiss analysis shows predominantly antiferromagnetic (AFM) interactions for T > Tc, but the lack of long-range AFM order indicates magnetic frustration. We argue that the weak ferromagnetism in bulk LCO is induced by lattice strain, as is the case with thin films and nanoparticles. The lattice strain is present at the bulk surfaces and at the interfaces between the LCO and a trace cobalt oxide phase. The ferromagnetic ordering in the LCO bulk is strongly affected by the Co-O-Co angle (γ), in agreement with recent band calculations which predict that ferromagnetic long-range order can only take place above a critical value, γC. Consistent with recent thin film estimations, we find γC = 162.8°. For γ > γC, we observe power-law behavior in the structural parameters. γ decreases with T until the critical temperature, To ≈ 37 K; below To the rate of change becomes very small. For T < To, FM order appears to be confined to regions close to the surfaces, likely due to the lattice strain keeping the local Co-O-Co angle above γC.

  13. The phase transition of higher dimensional Charged black holes

    CERN Document Server

    Guo, Xiongying; Zhang, Lichun; Zhao, Ren

    2016-01-01

    In this paper,we have studied phase transitions of higher dimensional charge black hole with spherical symmetry. we calculated the local energy and local temperature, and find that these state parameters satisfy the first law of thermodynamics. We analyze the critical behavior of black hole thermodynamic system by taking state parameters $(Q,\\Phi)$ of black hole thermodynamic system, in accordance with considering to the state parameters $(P,V)$ of Van der Waals system respectively. we obtain the critical point of black hole thermodynamic system, and find the critical point is independent of the dual independent variables we selected. This result for asymptotically flat space is consistent with that for AdS spacetime, and is intrinsic property of black hole thermodynamic system.

  14. The Phase Transition of Higher Dimensional Charged Black Holes

    Directory of Open Access Journals (Sweden)

    Xiongying Guo

    2016-01-01

    Full Text Available We have studied phase transitions of higher dimensional charge black hole with spherical symmetry. We calculated the local energy and local temperature and find that these state parameters satisfy the first law of thermodynamics. We analyze the critical behavior of black hole thermodynamic system by taking state parameters (Q,Φ of black hole thermodynamic system, in accordance with considering the state parameters (P,V of van der Waals system, respectively. We obtain the critical point of black hole thermodynamic system and find that the critical point is independent of the dual independent variables we selected. This result for asymptotically flat space is consistent with that for AdS spacetime and is intrinsic property of black hole thermodynamic system.

  15. Phase transitions, inhomogeneous horizons and second-order hydrodynamics

    Science.gov (United States)

    Attems, Maximilian; Bea, Yago; Casalderrey-Solana, Jorge; Mateos, David; Triana, Miquel; Zilhão, Miguel

    2017-06-01

    We use holography to study the spinodal instability of a four-dimensional, strongly-coupled gauge theory with a first-order thermal phase transition. We place the theory on a cylinder in a set of homogeneous, unstable initial states. The dual gravity configurations are black branes afflicted by a Gregory-Laflamme instability. We numerically evolve Einstein's equations to follow the instability until the system settles down to a stationary, inhomogeneous black brane. The dual gauge theory states have constant temperature but non-constant energy density. We show that the time evolution of the instability and the final states are accurately described by second-order hydrodynamics. In the static limit, the latter reduces to a single, second-order, non-linear differential equation from which the inhomogeneous final states can be derived.

  16. Holographic paramagnetism–ferromagnetism phase transition with the nonlinear electrodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Cheng-Yuan; Wu, Ya-Bo, E-mail: ybwu61@163.com; Zhang, Ya-Nan; Wang, Huan-Yu; Wu, Meng-Meng

    2017-01-15

    In the probe limit, we investigate the nonlinear electrodynamical effects of the both exponential form and the logarithmic form on the holographic paramagnetism–ferromagnetism phase transition in the background of a Schwarzschild-AdS black hole spacetime. Moreover, by comparing the exponential form of nonlinear electrodynamics with the logarithmic form of nonlinear electrodynamics and the Born–Infeld nonlinear electrodynamics which has been presented in Ref. , we find that the higher nonlinear electrodynamics correction makes the critical temperature smaller and the magnetic moment harder form in the case without external field. Furthermore, the increase of nonlinear parameter b will result in extending the period of the external magnetic field. Especially, the effect of the exponential form of nonlinear electrodynamics on the periodicity of hysteresis loop is more noticeable.

  17. Holographic paramagnetism–ferromagnetism phase transition with the nonlinear electrodynamics

    Directory of Open Access Journals (Sweden)

    Cheng-Yuan Zhang

    2017-01-01

    Full Text Available In the probe limit, we investigate the nonlinear electrodynamical effects of the both exponential form and the logarithmic form on the holographic paramagnetism–ferromagnetism phase transition in the background of a Schwarzschild-AdS black hole spacetime. Moreover, by comparing the exponential form of nonlinear electrodynamics with the logarithmic form of nonlinear electrodynamics and the Born–Infeld nonlinear electrodynamics which has been presented in Ref. [55], we find that the higher nonlinear electrodynamics correction makes the critical temperature smaller and the magnetic moment harder form in the case without external field. Furthermore, the increase of nonlinear parameter b will result in extending the period of the external magnetic field. Especially, the effect of the exponential form of nonlinear electrodynamics on the periodicity of hysteresis loop is more noticeable.

  18. Holographic entanglement entropy in superconductor phase transition with dark matter sector

    Directory of Open Access Journals (Sweden)

    Yan Peng

    2015-11-01

    Full Text Available In this paper, we investigate the holographic phase transition with dark matter sector in the AdS black hole background away from the probe limit. We discuss the properties of phases mostly from the holographic topological entanglement entropy of the system. We find the entanglement entropy is a good probe to the critical temperature and the order of the phase transition in the general model. The behaviors of entanglement entropy at large strip size suggest that the area law still holds when including dark matter sector. We also conclude that the holographic topological entanglement entropy is useful in detecting the stability of the phase transitions. Furthermore, we derive the complete diagram of the effects of coupled parameters on the critical temperature through the entanglement entropy and analytical methods.

  19. On-chip detection of gel transition temperature using a novel micro-thermomechanical method.

    Directory of Open Access Journals (Sweden)

    Tsenguun Byambadorj

    Full Text Available We present a new thermomechanical method and a platform to measure the phase transition temperature at microscale. A thin film metal sensor on a membrane simultaneously measures both temperature and mechanical strain of the sample during heating and cooling cycles. This thermomechanical principle of operation is described in detail. Physical hydrogel samples are prepared as a disc-shaped gels (200 μm thick and 1 mm diameter and placed between an on-chip heater and sensor devices. The sol-gel transition temperature of gelatin solution at various concentrations, used as a model physical hydrogel, shows less than 3% deviation from in-depth rheological results. The developed thermomechanical methodology is promising for precise characterization of phase transition temperature of thermogels at microscale.

  20. Problem-Solving Phase Transitions During Team Collaboration.

    Science.gov (United States)

    Wiltshire, Travis J; Butner, Jonathan E; Fiore, Stephen M

    2017-02-18

    Multiple theories of problem-solving hypothesize that there are distinct qualitative phases exhibited during effective problem-solving. However, limited research has attempted to identify when transitions between phases occur. We integrate theory on collaborative problem-solving (CPS) with dynamical systems theory suggesting that when a system is undergoing a phase transition it should exhibit a peak in entropy and that entropy levels should also relate to team performance. Communications from 40 teams that collaborated on a complex problem were coded for occurrence of problem-solving processes. We applied a sliding window entropy technique to each team's communications and specified criteria for (a) identifying data points that qualify as peaks and (b) determining which peaks were robust. We used multilevel modeling, and provide a qualitative example, to evaluate whether phases exhibit distinct distributions of communication processes. We also tested whether there was a relationship between entropy values at transition points and CPS performance. We found that a proportion of entropy peaks was robust and that the relative occurrence of communication codes varied significantly across phases. Peaks in entropy thus corresponded to qualitative shifts in teams' CPS communications, providing empirical evidence that teams exhibit phase transitions during CPS. Also, lower average levels of entropy at the phase transition points predicted better CPS performance. We specify future directions to improve understanding of phase transitions during CPS, and collaborative cognition, more broadly. Copyright © 2017 Cognitive Science Society, Inc.

  1. A molecular ;phase ordering; phase transition leading to a modulated aperiodic composite in n-heptane/urea

    Energy Technology Data Exchange (ETDEWEB)

    Mariette, C.; Huard, M.; Rabiller, P.; Nichols, Shane M.; Ecolivet, C.; Janssen, Ted; Alquist, III, Keith E.; Hollingsworth, Mark D.; Toudic, B. (CNRS-UMR); (Nijmegen); (KSU)

    2012-07-11

    n-Heptane/urea is an aperiodic inclusion compound in which the ratio of host and guest repeats along the channel axis is very close to unity and is found to have a constant value (0.981) from 280 K to 90 K. Below 280 K, two phase transitions are observed. The first (T{sub c1} = 145 K) is a ferroelastic phase transition that generates superstructure reflections for the host while leaving the guest with 1D order. The second (T{sub c2} = 130 K) is a 'phase ordering' transition to a four-dimensional structure (P2{sub 1}11(0{beta}{gamma})) with pronounced host-guest intermodulation and a temperature dependent phase shift between guests in adjacent channels.

  2. Role of multistability in the transition to chaotic phase synchronization

    DEFF Research Database (Denmark)

    Postnov, D.E.; Vadivasova, T.E.; Sosnovtseva, Olga

    1999-01-01

    In this paper we describe the transition to phase synchronization for systems of coupled nonlinear oscillators that individually follow the Feigenbaum route to chaos. A nested structure of phase synchronized regions of different attractor families is observed. With this structure, the transition...... to nonsynchronous behavior is determined by the loss of stability for the most stable synchronous mode. It is shown that the appearance of hyperchaos and the transition from lag synchronization to phase synchronization are related to the merging of chaotic attractors from different families. Numerical examples...

  3. A note on Maxwell's equal area law for black hole phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Lan, Shan-Quan; Mo, Jie-Xiong; Liu, Wen-Biao [Beijing Normal University, Department of Physics, Institute of Theoretical Physics, Beijing (China)

    2015-09-15

    The state equation of the charged AdS black hole is reviewed in the T-r{sub +} plane. With a view on the the phase transition, the T-S, P-V, P-ν graphs are plotted and then the equal area law is used in the three cases to get the phase transition point (P, T). The analytical phase transition point relations for P-T of a charged AdS black hole has been obtained successfully. By comparing the three results, we find that the equal area law possibly cannot be used directly for the P-ν plane. According to the T-S, P-V results, we plot the P-T-Q graph and find that for a highly charged black hole a very low temperature condition is required for the phase transition. (orig.)

  4. A note on Maxwell’s equal area law for black hole phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Lan, Shan-Quan; Mo, Jie-Xiong; Liu, Wen-Biao, E-mail: wbliu@bnu.edu.cn [Department of Physics, Institute of Theoretical Physics, Beijing Normal University, 100875, Beijing (China)

    2015-09-09

    The state equation of the charged AdS black hole is reviewed in the T–r{sub +} plane. With a view on the the phase transition, the T–S, P–V, P–ν graphs are plotted and then the equal area law is used in the three cases to get the phase transition point (P, T). The analytical phase transition point relations for P–T of a charged AdS black hole has been obtained successfully. By comparing the three results, we find that the equal area law possibly cannot be used directly for the P–ν plane. According to the T–S, P–V results, we plot the P–T–Q graph and find that for a highly charged black hole a very low temperature condition is required for the phase transition.

  5. Energy probability distribution zeros: A route to study phase transitions

    Science.gov (United States)

    Costa, B. V.; Mól, L. A. S.; Rocha, J. C. S.

    2017-07-01

    In the study of phase transitions a very few models are accessible to exact solution. In most cases analytical simplifications have to be done or some numerical techniques have to be used to get insight about their critical properties. Numerically, the most common approaches are those based on Monte Carlo simulations together with finite size scaling analysis. The use of Monte Carlo techniques requires the estimation of quantities like the specific heat or susceptibilities in a wide range of temperaturesor the construction of the density of states in large intervals of energy. Although many of these techniques are well developed they may be very time consuming when the system size becomes large enough. It should be suitable to have a method that could surpass those difficulties. In this work we present an iterative method to study the critical behavior of a system based on the partial knowledge of the complex Fisher zeros set of the partition function. The method is general with advantages over most conventional techniques since it does not need to identify any order parameter a priori. The critical temperature and exponents can be obtained with great precision even in the most unamenable cases like the two dimensional XY model. To test the method and to show how it works we applied it to some selected models where the transitions are well known: The 2D Ising, Potts and XY models and to a homopolymer system. Our choices cover systems with first order, continuous and Berezinskii-Kosterlitz-Thouless transitions as well as the homopolymer that has two pseudo-transitions. The strategy can easily be adapted to any model, classical or quantum, once we are able to build the corresponding energy probability distribution.

  6. The low-temperature phase of morpholinium tetrafluoroborate

    Directory of Open Access Journals (Sweden)

    Tadeusz Lis

    2008-04-01

    Full Text Available The crystal structure of the low-temperature form of the title compound, C4H10NO+·BF4−, was determined at 80 K. Two reversible phase transitions, at 158/158 and 124/126 K (heating/cooling, were detected by differential scanning calorimetry for this compound, and the sequence of phase transitions was subsequently confirmed by single-crystal X-ray diffraction experiments. The asymmetric unit at 80 K consists of three BF4− tetrahedral anions and three morpholinium cations (Z′ = 3. Hydrogen-bonded morpholinium cations form chains along the [100] direction. The BF4− anions are connected to these chains by N—H...F hydrogen bonds. In the crystal structure, two different layers perpendicular to the [001] direction can be distinguished, which differ in the geometry of the hydrogen bonds between cationic and anionic species.

  7. Phase transitions and Heisenberg limited metrology in an Ising chain interacting with a single-mode cavity field

    DEFF Research Database (Denmark)

    Gammelmark, Søren; Mølmer, Klaus

    2011-01-01

    the Ising phase transition. Physical systems with first-order phase transitions are natural candidates for metrology and calibration purposes, and we apply filter theory to show that the sensitivity of the physical system to temperature and external fields reaches the 1/N Heisenberg limit....

  8. Oscillation phenomenon of transition temperatures of coupled magnetic planes

    Directory of Open Access Journals (Sweden)

    H. Moradi

    2004-06-01

    Full Text Available   Oscillatory behavior of transition temperature in supper lattice, Ni/Au/Ni, has been observed as a function of spacer layer, Au. The observed oscillation period is almost the half period of interlayer exchange coupling. The high temperature susceptibility of a two - dimensional lattice is evaluated within the Bethe-Peierls-Wiess approximation in the presence of a random field with square distribution. This susceptibility is used to evaluate the transition temperature of coupled planes as a function of spacer thickness. The calculated transition temperature of coupled planes oscillates as half period of interlayer exchange coupling and falls below the results of the uncoupled films at some values of the average spacer thickness that were experimentally observed. Additionally, the transition temperature depends on the distribution function of random field at the small thickness of spacer.

  9. Melt-vapor phase transition in the lead-selenium system at atmospheric and low pressure

    Science.gov (United States)

    Volodin, V. N.; Burabaeva, N. M.; Trebukhov, S. A.

    2016-03-01

    The boiling temperature and the corresponding vapor phase composition in the existence domain of liquid solutions were calculated from the partial pressures of saturated vapor of the components and lead selenide over liquid melts in the lead-selenium system. The phase diagram was complemented with the liquid-vapor phase transition at atmospheric pressure and in vacuum of 100 Pa, which allowed us to judge the behavior of the components during the distillation separation.

  10. Effect of annealing on phase transition in poly (vinylidene fluoride ...

    Indian Academy of Sciences (India)

    The -phase poly (vinylidene fluoride) (PVDF) films are usually prepared using dimethyl sulfoxide (DMSO) solvent, regardless of preparation temperature. Here we report the crystallization of both and -phase PVDF films by varying preparation temperature using DMSO solvent. The -phase PVDF films were annealed ...

  11. Pressure-dependence of the phase transitions and thermal expansion in zirconium and hafnium pyrovanadate

    Energy Technology Data Exchange (ETDEWEB)

    Gallington, Leighanne C.; Hester, Brett R.; Kaplan, Benjamin S.; Wilkinson, Angus P. (GIT)

    2017-05-01

    Low or negative thermal expansion (NTE) has been previously observed in members of the ZrP2O7 family at temperatures higher than their order-disorder phase transitions. The thermoelastic properties and phase behavior of the low temperature superstructure and high temperature negative thermal expansion phases of ZrV2O7 and HfV2O7 were explored via in situ variable temperature/pressure powder x-ray diffraction measurements. The phase transition temperatures of ZrV2O7 and HfV2O7 exhibited a very strong dependence on pressure (~700 K GPa), with moderate compression suppressing the formation of their NTE phases below 513 K. Compression also reduced the magnitude of the coefficients of thermal expansion in both the positive and negative thermal expansion phases. Additionally, the high temperature NTE phase of ZrV2O7 was found to be twice as stiff as the low temperature positive thermal expansion superstructure (24 and 12 GPa respectively).

  12. Dielectric behavior and phase transition in [111]-oriented PIN–PMN–PT single crystals under dc bias

    Directory of Open Access Journals (Sweden)

    Yuhui Wan

    2014-01-01

    Full Text Available Temperature and electric field dependences of the dielectric behavior and phase transition for [111]-oriented 0.23PIN–0.52PMN–0.25PT (PIN-PMN–0.25PT and 0.24PIN–0.43PMN–0.33PT (PIN–PMN–0.33PT single crystals were investigated over a temperature range from -100°C to 250°C using field-heating (FH dielectric measurements. The transition phenomenon from ferroelectric microdomain to macrodomain was found in rhombohedra (R phase region in the single crystals under dc bias. This transition temperature Tf of micro-to-macrodomain is sensitive to dc bias and move quickly to lower temperature with increasing dc bias. The phase transition temperatures in the two single crystals shift toward high temperature and the dielectric permittivities at the phase transition temperature decrease with increasing dc bias. Especially, the phase transition peaks are gradually broad in PIN–PMN–0.33PT single crystal with the increasing dc bias. Effects of dc bias on the dielectric behavior and phase transition in PIN–PMN–PT single crystals are discussed.

  13. Vapor phase lubrication of high temperature alloys

    Energy Technology Data Exchange (ETDEWEB)

    Hanyaloglu, B.F.; Graham, E.E.; Oreskovic, T.; Hajj, C.G. [Cleveland State Univ., OH (United States)

    1995-06-01

    In a previous study, it was found that when a nickel-based superalloy IN750 was heated to high temperatures, a passive layer of aluminum oxide formed on the surface, preventing vapor phase lubrication. In this study, two nickel-chrome-iron alloys and a nickel-copper alloy were studied for high temperature lubrication to see if these alloys, which contained small amounts of aluminum, would exhibit similar behavior. It was found that under static conditions, all three alloys formed a lubricious nodular coating when exposed to a vapor of aryl phosphate. Under dynamic sliding conditions at 500{degrees}C, these alloys were successfully lubricated with a coefficient of friction of 0.1 and no detectable wear. In order to explain these results, a direct correlation between successful vapor phase lubrication and the composition of the alloys containing aluminum has been proposed. If the ratio of copper/aluminum or iron/aluminum is greater that 100 vapor phase, lubrication will be successful. If the ratio is less than 10, a passive aluminum oxide layer will prevent vapor phase lubrication. By selecting alloys with a high iron or copper content, vapor phase lubrication can provide excellent lubrication at high temperatures. 14 refs., 11 figs., 1 tab.

  14. Transition Temperatures of Thermotropic Liquid Crystals from the Local Binary Gray Level Cooccurrence Matrix

    Directory of Open Access Journals (Sweden)

    S. Sreehari Sastry

    2012-01-01

    Full Text Available This paper presents a method which combines the statistical analysis with texture structural analysis called Local Binary Gray Level Cooccurrence Matrix (LBGLCM to investigate the phase transition temperatures of thermotropic p,n-alkyloxy benzoic acid (nOBA, n=4,6,8,10 and 12 liquid crystals. Textures of the homeotropically aligned liquid crystal compounds are recorded as a function of temperature using polarizing optical microscope attached to the hot stage and high resolution camera. In this method, second-order statistical parameters (contrast, energy, homogeneity, and correlation are extracted from the LBGLCM of the textures. The changes associatedwiththe values of extracted parameters as a function of temperature are a helpful process to identify the phases and phase transition temperatures of the samples. Results obtained from this method have validity and are in good agreement with the literature.

  15. The Electroweak Phase Transition, Part 2: $\\epsilon$-Expansion Results

    OpenAIRE

    Yaffe, Laurence

    1994-01-01

    Talk presented at the conference Quarks `94: Vladimir, Russia. I summarize the application of $\\epsilon$-expansion methods to the electroweak phase transition. Results from both leading and next-to-leading order calculations are discussed.

  16. Dynamical Symmetries and Causality in Non-Equilibrium Phase Transitions

    Directory of Open Access Journals (Sweden)

    Malte Henkel

    2015-11-01

    Full Text Available Dynamical symmetries are of considerable importance in elucidating the complex behaviour of strongly interacting systems with many degrees of freedom. Paradigmatic examples are cooperative phenomena as they arise in phase transitions, where conformal invariance has led to enormous progress in equilibrium phase transitions, especially in two dimensions. Non-equilibrium phase transitions can arise in much larger portions of the parameter space than equilibrium phase transitions. The state of the art of recent attempts to generalise conformal invariance to a new generic symmetry, taking into account the different scaling behaviour of space and time, will be reviewed. Particular attention will be given to the causality properties as they follow for co-variant n-point functions. These are important for the physical identification of n-point functions as responses or correlators.

  17. Glass transition and heavy oil dynamics at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Abivin, P.; Indo, K.; Cheng, Y.; Freed, D.; Taylor, S. D. [Schlumberger (Canada)], email: PAbivin@slb.com

    2011-07-01

    In the oil industry, the viscosity of crude oils is a key factor as it affects market value, field developments and the design of production strategies. In heavy oils, a glass transition occurs and previous work related this to oil's temperature-viscosity behavior. This study aimed at better characterizing heavy oil dynamics and the temperature dependency of viscosity. Experiments were conducted with differential scanning calorimetry and shear rate sweeps on heavy oils from Asia, South America and North America over a wide range of temperatures to measure their viscosities and characterize their glass transition. The glass transition was observed at around 210K and results showed that the Arrhenius model does not fit the experimental data at low temperatures but the WLF model does. This research provided a better understanding of heavy oil dynamics but further work is required to explain the viscosity-temperature behavior of heavy oils at low temperatures.

  18. Detection of thermoresponsive polymer phase transition in dilute low-volume format by microscale thermophoretic depletion.

    Science.gov (United States)

    Wolff, Manuel; Braun, Dieter; Nash, Michael A

    2014-07-15

    Environmentally responsive polymers are becoming increasingly important in the biomaterials field for use as diagnostic reagents, drug carriers, and tissue engineering scaffolds. Characterizing polymer phase transitions by cloud point curves typically requires large milliliter volumes of sample at high micromolar solution concentrations. Here we present a method based on quantification of thermophoretic Soret diffusion that allows determination of polymer phase transitions using only ~1 μL of liquid at dilute nanomolar concentrations, effectively reducing the amount of sample required by a factor of 10(6). We prepared an oligo(ethylene glycol) (OEG) methyl ether methacrylate copolymer via RAFT polymerization. End-group modification with fluorescent BODIPY-maleimide provided a dye-labeled pOEG-BODIPY conjugate with a lower critical solution temperature (LCST) in the range of ~25-35 °C. Thermophoresis measurements in dilute solution demonstrated a marked change in polymer thermodiffusion in the vicinity of the LCST. We measured the temperature dependence of thermodiffusion and transformed these data sets into sigmoidal curves characterizing the phase transition of the polymer. Finite element modeling suggested a correction to the measured values that brought the transition temperatures measured by thermophoresis into accord with the cloud point curves. Our results demonstrate that observation of polymer thermodiffusion in a low volume dilute format is a facile method for determining polymer phase transition temperatures.

  19. Causes And Effects Of Phase Transitions In Highway Traffic

    OpenAIRE

    Daganzo, C. F.; Cassidy, M. J.; Bertini, R. L.

    1997-01-01

    It is shown that all the phase transitions in and out of freely flowing traffic reported earlier for a German site could be caused by bottlenecks, as are all the transitions observed at two other sites examined here. Furthermore, all the evidence indicates that bottlenecks cause these transitions in a predictable way, and no evidence is found that stoppages (jams) appear spontaneously in free flow traffic for no apparent reason. The most salient phenomena observed at all locations are explain...

  20. Phase Transitions in Dynamically Compressed Bi

    Science.gov (United States)

    Gorman, Martin; Briggs, Richard; Coleman, Amy; McWilliams, Stewart; McBride, Emma; McGonegle, David; Wark, Justin; Bolme, Cindy; Gleason, Arianna; Collins, Gilbert; Eggert, Jon; Fratanduono, Dayne; Smith, Ray; Galtier, Eric; Lee, Hae Ja; Grandos, Eduardo; Nagler, Bob; Xing, Zhou; McMahon, Malcolm; N/A, N./A.; University of Edinburgh Team; LLNL Team; Oxford University Team; SLAC Team; LANL Team

    2017-06-01

    The ability to characterise atomic structure at extreme conditions and on the timescale of laser-driven shock experiments is vital for our understanding of how materials behave under rapid pressure loading. A key finding in recent static high-pressure studies has been that many materials adopt complex crystal structures at high-pressure such as incommensurate host-guest structures. However, it is uncertain whether such complex structures are able to form on the timescales of laser shock experiments due to the highly reconstructive nature of the phase transformation mechanisms, leading to the possibility of non-equilibrium phases forming. We present X-ray diffraction measurements that characterise the structure of several solid phases of Bi including one new phase, which is not reported in the equilibrium phase diagram. Diffraction measurements on molten Bi will also be presented and the prospect of extracting quantitative density information from the liquid diffraction data will be discussed.

  1. On the theory of phase transitions in polypeptides

    DEFF Research Database (Denmark)

    Yakubovich, Alexander V.; Solov'yov, Ilia; Solov'yov, Andrey V.

    2008-01-01

    We suggest a theoretical method based on the statistical mechanics for treating the alpha-helix random coil transition in polypeptides. This process is considered as a first-order-like phase transition. The developed theory is free of model parameters and is based solely on fundamental physical...

  2. Phase transition of bismuth telluride thin films grown by MBE

    DEFF Research Database (Denmark)

    Fülöp, Attila; Song, Yuxin; Charpentier, Sophie

    2014-01-01

    A previously unreported phase transition between Bi2Te3 and Bi4Te3 in bismuth telluride grown by molecular beam epitaxy is recorded via XRD, AFM, and SIMS observations. This transition is found to be related to the Te/Bi beam equivalent pressure (BEP) ratio. BEP ratios below 17 favor the formation...

  3. The QCD phase transitions: From mechanism to observables

    Energy Technology Data Exchange (ETDEWEB)

    Shuryak, E.V.

    1997-09-22

    This paper contains viewgraphs on quantum chromodynamic phase transformations during heavy ion collisions. Some topics briefly described are: finite T transitions of I molecule pairs; finite density transitions of diquarks polymers; and the softtest point of the equation of state as a source of discontinuous behavior as a function of collision energy or centrality.

  4. Ultrafast photoinduced structure phase transition in antimony single crystals

    NARCIS (Netherlands)

    Fausti, Daniele; Misochko, Oleg V.; van Loosdrecht, Paul H. M.

    2009-01-01

    Picosecond Raman scattering is used to study the photoinduced ultrafast dynamics in Peierls distorted antimony. We find evidence for an ultrafast nonthermal reversible structural phase transition. Most surprisingly, we find evidence that this transition evolves toward a lower symmetry in contrast to

  5. Experimental Properties of Phase Transitions in Traffic Flow

    Science.gov (United States)

    Kerner, B. S.; Rehborn, H.

    1997-11-01

    Investigations of a great number of measurements of traffic flow on German highways show that there are some common macroscopic properties of phase transitions between free flow, synchronized flow, and traffic jams. In particular, it is shown that a short-time localized perturbation is able to cause a local phase transition from free flow to synchronized flow and that synchronized flow of slow moving vehicles can further be self-maintained on a highway for several hours.

  6. Quantum Phase Transitions around the Staggered Valence Bond Solid

    OpenAIRE

    Xu, Cenke; Balents, Leon

    2011-01-01

    Motivated by recent numerical results, we study the quantum phase transitions between Z_2 spin liquid, Neel ordered, and various valence bond solid (VBS) states on the honeycomb and square lattices, with emphasis on the staggered VBS. In contrast to the well-understood columnar VBS order, the staggered VBS is not described by an XY order parameter with Z_N anisotropy close to these quantum phase transitions. Instead, we demonstrate that on the honeycomb lattice, the staggered VBS is more appr...

  7. QCD-bag mass spectrum and phase transitions

    OpenAIRE

    Tounsi, A.; Letessier, J.; Rafelski, J

    1998-01-01

    We obtain the hadronic mass spectrum in the `bag of bags' statistical bootstrap model (BBSBM), implementing the colorless state condition, aside of baryon and strangeness conservation, using group projection method. We study the partition function, investigate the properties of dense hadronic matter, and determine the conditions under which the system undergoes a phase transition to a deconfined quark-gluon plasma. We show that a phase transition cannot occur in the N=1 (Abelian) limit of our...

  8. Locating phase transitions in computationally hard problems

    Indian Academy of Sciences (India)

    Treating the computational time, value and utility functions involved in the search results in analogy with quantities in statistical physics, we indicate how the onset of a computationally hard regime can be detected and the transit to higher quality solutions be quantified by an appropriate response function. The existence of a ...

  9. Low-temperature high magnetic field powder x-ray diffraction setup for field-induced structural phase transition studies from 2 to 300 K and at 0 to 8-T field

    Science.gov (United States)

    Shahee, Aga; Sharma, Shivani; Kumar, Dhirendra; Yadav, Poonam; Bhardwaj, Preeti; Ghodke, Nandkishor; Singh, Kiran; Lalla, N. P.; Chaddah, P.

    2016-10-01

    A low-temperature and high magnetic field powder x-ray diffractometer (XRD) has been developed at UGC-DAE CSR (UGC: University Grant Commission, DAE: Department of Atomic Energy, and CSR: Consortium for scientific research), Indore, India. The setup has been developed around an 18 kW rotating anode x-ray source delivering Cu-Kα x-rays coming from a vertical line source. It works in a symmetric θ-2θ parallel beam geometry. It consists of a liquid helium cryostat with an 8 T split-pair Nb-Ti superconducting magnet comprising two x-ray windows each covering an angular range of 65°. This is mounted on a non-magnetic type heavy duty goniometer equipped with all necessary motions along with data collection accessories. The incident x-ray beam has been made parallel using a parabolic multilayer mirror. The scattered x-ray is detected using a NaI detector through a 0.1° acceptance solar collimator. To control the motions of the goniometer, a computer programme has been developed. The wide-angle scattering data can be collected in a range of 2°-115° of 2θ with a resolution of ˜0.1°. The whole setup is tightly shielded for the scattered x-rays using a lead hutch. The functioning of the goniometer and the artifacts arising possibly due to the effect of stray magnetic field on the goniometer motions, on the x-ray source, and on the detector have been characterized by collecting powder XRD data of a National Institute of Standards and Technology certified standard reference material LaB6 (SRM-660b) and Si powder in zero-field and in-field conditions. Occurrence of field induced structural-phase transitions has been demonstrated on various samples like Pr0.5Sr0.5MnO3, Nd0.49Sr0.51MnO3-δ and La0.175Pr0.45Ca0.375MnO3 by collecting data in zero field cool and field cool conditions.

  10. Low-temperature high magnetic field powder x-ray diffraction setup for field-induced structural phase transition studies from 2 to 300 K and at 0 to 8-T field.

    Science.gov (United States)

    Shahee, Aga; Sharma, Shivani; Kumar, Dhirendra; Yadav, Poonam; Bhardwaj, Preeti; Ghodke, Nandkishor; Singh, Kiran; Lalla, N P; Chaddah, P

    2016-10-01

    A low-temperature and high magnetic field powder x-ray diffractometer (XRD) has been developed at UGC-DAE CSR (UGC: University Grant Commission, DAE: Department of Atomic Energy, and CSR: Consortium for scientific research), Indore, India. The setup has been developed around an 18 kW rotating anode x-ray source delivering Cu-Kα x-rays coming from a vertical line source. It works in a symmetric θ-2θ parallel beam geometry. It consists of a liquid helium cryostat with an 8 T split-pair Nb-Ti superconducting magnet comprising two x-ray windows each covering an angular range of 65°. This is mounted on a non-magnetic type heavy duty goniometer equipped with all necessary motions along with data collection accessories. The incident x-ray beam has been made parallel using a parabolic multilayer mirror. The scattered x-ray is detected using a NaI detector through a 0.1° acceptance solar collimator. To control the motions of the goniometer, a computer programme has been developed. The wide-angle scattering data can be collected in a range of 2°-115° of 2θ with a resolution of ∼0.1°. The whole setup is tightly shielded for the scattered x-rays using a lead hutch. The functioning of the goniometer and the artifacts arising possibly due to the effect of stray magnetic field on the goniometer motions, on the x-ray source, and on the detector have been characterized by collecting powder XRD data of a National Institute of Standards and Technology certified standard reference material LaB6 (SRM-660b) and Si powder in zero-field and in-field conditions. Occurrence of field induced structural-phase transitions has been demonstrated on various samples like Pr0.5Sr0.5MnO3, Nd0.49Sr0.51MnO3-δ and La0.175Pr0.45Ca0.375MnO3 by collecting data in zero field cool and field cool conditions.

  11. Bubble nucleation and growth in very strong cosmological phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Mégevand, Ariel, E-mail: megevand@mdp.edu.ar; Ramírez, Santiago

    2017-06-15

    Strongly first-order phase transitions, i.e., those with a large order parameter, are characterized by a considerable supercooling and high velocities of phase transition fronts. A very strong phase transition may have important cosmological consequences due to the departures from equilibrium caused in the plasma. In general, there is a limit to the strength, since the metastability of the old phase may prevent the transition to complete. Near this limit, the bubble nucleation rate achieves a maximum and thus departs from the widely assumed behavior in which it grows exponentially with time. We study the dynamics of this kind of phase transitions. We show that in some cases a gaussian approximation for the nucleation rate is more suitable, and in such a case we solve analytically the evolution of the phase transition. We compare the gaussian and exponential approximations with realistic cases and we determine their ranges of validity. We also discuss the implications for cosmic remnants such as gravitational waves.

  12. Liquid-liquid phase transition and glass transition in a monoatomic model system.

    Science.gov (United States)

    Xu, Limei; Buldyrev, Sergey V; Giovambattista, Nicolas; Stanley, H Eugene

    2010-01-01

    We review our recent study on the polyamorphism of the liquid and glass states in a monatomic system, a two-scale spherical-symmetric Jagla model with both attractive and repulsive interactions. This potential with a parametrization for which crystallization can be avoided and both the glass transition and the liquid-liquid phase transition are clearly separated, displays water-like anomalies as well as polyamorphism in both liquid and glassy states, providing a unique opportunity to study the interplay between the liquid-liquid phase transition and the glass transition. Our study on a simple model may be useful in understanding recent studies of polyamorphism in metallic glasses.

  13. Stability of rhombohedral phases in vanadium at high-pressure and high-temperature: first-principles investigations

    CERN Document Server

    Wang, Yi X; Chen, Xiang R; Geng, Hua Y

    2016-01-01

    The pressure-induced transition of vanadium from BCC to rhombohedral structures is unique and intriguing among transition metals. In this work, the stability of these phases is revisited by using density functional theory. At finite temperatures, a novel transition of rhombohedral phases back to BCC phase induced by thermal electrons is discovered. This reentrant transition is found not driven by phonons, instead it is the electronic entropy that stabilizes the latter phase, which is totally out of expectation. Parallel to this transition, we find a peculiar and strong increase of the shear modulus C44 with increasing temperature. It is counter-intuitive in the sense that it suggests an unusual harding mechanism of vanadium by temperature. With these stability analyses, the high-pressure and finite-temperature phase diagram of vanadium is proposed. Furthermore, the dependence of the stability of RH phases on the Fermi energy and chemical environment is investigated. The results demonstrate that the position o...

  14. Problem-solving phase transitions during team collaboration

    DEFF Research Database (Denmark)

    Wiltshire, Travis; Butner, Jonathan E.; Fiore, Stephen M.

    2017-01-01

    ) with dynamical systems theory suggesting that when a system is undergoing a phase transition it should exhibit a peak in entropy and that entropy levels should also relate to team performance. Communications from 40 teams that collaborated on a complex problem were coded for occurrence of problem......-solving processes. We applied a sliding window entropy technique to each team's communications and specified criteria for (a) identifying data points that qualify as peaks and (b) determining which peaks were robust. We used multilevel modeling, and provide a qualitative example, to evaluate whether phases exhibit...... phases. Peaks in entropy thus corresponded to qualitative shifts in teams’ CPS communications, providing empirical evidence that teams exhibit phase transitions during CPS. Also, lower average levels of entropy at the phase transition points predicted better CPS performance. We specify future directions...

  15. Non-Fourier heat conduction and phase transition in laser ablation of polytetrafluoroethylene (PTFE)

    Science.gov (United States)

    Zhang, Yu; Zhang, Daixian; Wu, Jianjun; Li, Jian; He, Zhaofu

    2017-11-01

    The phase transition in heat conduction of polytetrafluoroethylene-like polymers was investigated and applied in many fields of science and engineering. Considering more details including internal absorption of laser radiation, reflectivity of material and non-Fourier effect etc., the combined heat conduction and phase transition in laser ablation of polytetrafluoroethylene were modeled and investigated numerically. The thermal and mechanic issues in laser ablation were illustrated and analyzed. Especially, the phenomenon of temperature discontinuity formed in the combined phase transition and non-Fourier heat conduction was discussed. Comparisons of target temperature profiles between Fourier and non-Fourier heat conduction in melting process were implemented. It was indicated that the effect of non-Fourier plays an important role in the temperature evolvement. The effect of laser fluence was proven to be significant and the thermal wave propagation was independent on the laser intensity for the non-Fourier heat conduction. Besides, the effect of absorption coefficients on temperature evolvements was studied. For different ranges of absorption coefficients, different temperature evolvements can be achieved. The above numerical simulation provided insight into physical processes of combined non-Fourier heat conduction and phase transition in laser ablation.

  16. Disappearance of the Superionic Phase Transition in Sub-5 nm Silver Iodide Nanoparticles.

    Science.gov (United States)

    Yamamoto, Takayuki; Kobayashi, Hirokazu; Kumara, Loku Singgappulige Rosantha; Sakata, Osami; Nitta, Kiyofumi; Uruga, Tomoya; Kitagawa, Hiroshi

    2017-09-13

    Bulk silver iodide (AgI) is known to show a phase transition from the poorly conducting β/γ-phases into the superionic conducting α-phase at 147 °C. Its transition temperature decreases with decreasing the size of AgI, and the α-phase exists stably at 37 °C in AgI nanoparticles with a diameter of 6.3 nm. In this Letter, we investigated the atomic configuration, the phase transition behavior, and the ionic conductivity of AgI nanoparticles with a diameter of 3.0 nm. The combination of pair distribution function (PDF) analysis and reverse Monte Carlo (RMC) modeling based on high-energy X-ray diffraction (XRD) revealed for the first time that they formed the β/γ-phases with atomic disorder. The results of extended X-ray absorption fine structure (EXAFS) analysis, differential scanning calorimetry (DSC), and AC impedance spectroscopy demonstrated that they did not exhibit the superionic phase transition and their ionic conductivity was lower than that of crystalline AgI. The disappearance of the superionic phase transition and low ionic conductivity in the very small AgI nanoparticles originates from their small size and disordered structure.

  17. Density Functional Theory for Phase-Ordering Transitions

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Jianzhong [Univ. of California, Riverside, CA (United States)

    2016-03-30

    Colloids display astonishing structural and dynamic properties that can be dramatically altered by modest changes in the solution condition or an external field. This complex behavior stems from a subtle balance of colloidal forces and intriguing mesoscopic and macroscopic phase transitions that are sensitive to the processing conditions and the dispersing environment. Whereas the knowledge on the microscopic structure and phase behavior of colloidal systems at equilibrium is now well-advanced, quantitative predictions of the dynamic properties and the kinetics of phase-ordering transitions in colloids are not always realized. Many important mesoscopic and off-equilibrium colloidal states remain poorly understood. The proposed research aims to develop a new, unifying approach to describe colloidal dynamics and the kinetics of phase-ordering transitions based on accomplishments from previous work for the equilibrium properties of both uniform and inhomogeneous systems and on novel concepts from the state-of-the-art dynamic density functional theory. In addition to theoretical developments, computational research is designed to address a number of fundamental questions on phase-ordering transitions in colloids, in particular those pertinent to a competition of the dynamic pathways leading to various mesoscopic structures, off-equilibrium states, and crystalline phases. By providing a generic theoretical framework to describe equilibrium, metastable as well as non-ergodic phase transitions concurrent with the colloidal self-assembly processes, accomplishments from this work will have major impacts on both fundamental research and technological applications.

  18. Dielectric properties and phase transition of zinc tris(thiourea) sulfate single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Moitra, S. [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata-700032, West Bengal (India); Bhattacharya, S. [Department of Solid State Physics, Indian Association for the Cultivation of Science, Jadavpur, Kolkata-700032, West Bengal (India); Kar, T. [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata-700032, West Bengal (India); Ghosh, A. [Department of Solid State Physics, Indian Association for the Cultivation of Science, Jadavpur, Kolkata-700032, West Bengal (India)], E-mail: sspag@iacs.res.in

    2008-09-01

    The dielectric properties and the ferroelectric to paraelectric phase transition of zinc tris(thiourea) sulfate (ZTS) single crystal have been investigated in a wide range of temperatures and frequencies. In the lower frequency region the real part of dielectric permittivity of the ZTS crystal shows a sudden increase at 323 K. Prominent first-order ferroelectric to paraelectric phase transition at 323 K has been observed in the plot of dielectric permittivity versus temperature at different frequencies. It has been observed that the phase transition occurs in ZTS crystal with a low degree of disorder. Surprisingly, it has been observed for ZTS that the value of the dielectric permittivity is only about 10 at high frequencies and is found to increase to 50 at low frequencies. Dielectric loss has higher values in the paraelectric region.

  19. Molecular dynamics and the phase transition in solid C60

    Science.gov (United States)

    Tycko, R.; Dabbagh, G.; Fleming, R. M.; Haddon, R. C.; Makhija, A. V.; Zahurak, S. M.

    1991-09-01

    The molecular reorientational dynamics in two phases of solid C60 with C-13 NMR measurements are characterized. A change in the nature of the dynamics, indicated by a change in kinetic parameters extracted from spin-lattice relaxation data, occurs at the phase transition at 260 K. Above the transition, the molecules appear to execute continuous rotational diffusion; below the transition, they appear to jump between symmetry-equivalent orientations. This interpretation is consistent with the X-ray-diffraction results of Heiney et al. (1991) as well as the NMR relaxation and spectral data.

  20. Writhe induced phase transition in unknotted self-avoiding polygons

    Science.gov (United States)

    Dagrosa, E.; Owczarek, A. L.; Prellberg, T.

    2017-09-01

    Recently it has been argued that weighting the writhe of unknotted self-avoiding polygons can be related to possible experiments that turn double stranded DNA. We first solve exactly a directed model and demonstrate that in such a subset of polygons the problem of weighting their writhe is associated with a phase transition. We then analyse simulations using the Wang-Landau algorithm to observe scaling in the fluctuations of the writhe that is compatible with a second-order phase transition in a undirected self-avoiding polygon model. The transition can be clearly detected when the polygon is stretched with a strong pulling force.

  1. Gravitational waves from cosmological first order phase transitions

    CERN Document Server

    Hindmarsh, Mark; Rummukainen, Kari; Weir, David

    2015-01-01

    First order phase transitions in the early Universe generate gravitational waves, which may be observable in future space-based gravitational wave observatiories, e.g. the European eLISA satellite constellation. The gravitational waves provide an unprecedented direct view of the Universe at the time of their creation. We study the generation of the gravitational waves during a first order phase transition using large-scale simulations of a model consisting of relativistic fluid and an order parameter field. We observe that the dominant source of gravitational waves is the sound generated by the transition, resulting in considerably stronger radiation than earlier calculations have indicated.

  2. High speed, high temperature electrical characterization of phase change materials: metastable phases, crystallization dynamics, and resistance drift.

    Science.gov (United States)

    Dirisaglik, Faruk; Bakan, Gokhan; Jurado, Zoila; Muneer, Sadid; Akbulut, Mustafa; Rarey, Jonathan; Sullivan, Lindsay; Wennberg, Maren; King, Adrienne; Zhang, Lingyi; Nowak, Rebecca; Lam, Chung; Silva, Helena; Gokirmak, Ali

    2015-10-28

    During the fast switching in Ge2Sb2Te5 phase change memory devices, both the amorphous and fcc crystalline phases remain metastable beyond the fcc and hexagonal transition temperatures respectively. In this work, the metastable electrical properties together with crystallization times and resistance drift behaviour of GST are studied using a high-speed, device-level characterization technique in the temperature range of 300 K to 675 K.

  3. Chiral phase transition in the SU (3) Nambu and Jona-Lasinio model

    Energy Technology Data Exchange (ETDEWEB)

    Klimt, S.; Lutz, M.; Weise, W. (Regensburg Univ. (Germany, F.R.). Inst. fuer Physik 1 - Theoretische Physik)

    1990-10-25

    We calculate the thermodynamical potential of the SU(3) Nambu and Jona-Lasinio model in the mean field approximation and discuss the nature of the chiral phase transition, i.e. the mechanisms which govern chiral symmetry restoration at large temperature and/or quark densities. No evidence is found for a first order transition once realistic coupling strengths are used in the model. (orig.).

  4. Susceptibilities for the Müller-Hartmann-Zitartz countable infinity of phase transitions on a Cayley tree.

    Science.gov (United States)

    Sharma, Auditya

    2015-07-01

    We obtain explicit susceptibilities for the countable infinity of phase transition temperatures of Müller-Hartmann-Zitartz on a Cayley tree. The susceptibilities are a product of the zeroth spin with the sum of an appropriate set of averages of spins on the outermost layer of the tree. A clear physical understanding for these strange phase transitions emerges naturally. In the thermodynamic limit, the susceptibilities tend to zero above the transition and to infinity below it.

  5. Structural phase transition and phase diagram of half doped organometallic compound [(CH3)2NH2]Mn0.5Ni0.5(HCOO)3

    Science.gov (United States)

    Chakraborty, Tirthankar; Swain, Diptikanta; Yadav, Ruchika; Row, T. N. Guru; Elizabeth, Suja

    2017-11-01

    Structural phase transition in half doped compound [(CH3)2NH2]Mn0.5Ni0.5(HCOO)3 is investigated. Differential scanning calorimetry data indicated this to be a distinct transition with enthalpy 465.6 J/mol. Powder X-ray diffraction at different temperature shows structural phase transition from trigonal R-3c to monoclinic Cc through co-existing mixed phase. Based on the experimental results, a phase diagram has been proposed. This phase transition is confirmed to be of first order nature by specific heat measurement. Entropy change and latent heat of the phase transition are also calculated from specific heat which are found to be 2.53 J/mol-K and 412 J/mol respectively.

  6. Surface Premelting Coupled with Bulk Phase Transitions in Colloidal Crystals

    Science.gov (United States)

    Li, Bo; Wang, Feng; Zhou, Di; Cao, Xin; Peng, Yi; Ni, Ran; Liao, Maijia; Han, Yilong

    2015-03-01

    Colloids have been used as outstanding model systems for the studies of various phase transitions in bulk, but not at interface yet. Here we obtained equilibrium crystal-vapor interfaces using tunable attractive colloidal spheres and studied the surface premelting at the single-particle level by video microscopy. We found that monolayer crystals exhibit a bulk isostructural solid-solid transition which triggers the surface premelting. The premelting is incomplete due to the interruption of a mechanical-instability-induced bulk melting. By contrast, two- or multilayer crystals do not have the solid-solid transition and the mechanical instability, hence they exhibit complete premelting with divergent surface-liquid thickness. These novel interplays between bulk and surface phase transitions cast new lights for both types of transitions.

  7. Exploring percolative landscapes: Infinite cascades of geometric phase transitions.

    Science.gov (United States)

    Timonin, P N; Chitov, Gennady Y

    2016-01-01

    The evolution of many kinetic processes in 1+1 (space-time) dimensions results in 2D directed percolative landscapes. The active phases of these models possess numerous hidden geometric orders characterized by various types of large-scale and/or coarse-grained percolative backbones that we define. For the patterns originated in the classical directed percolation (DP) and contact process we show from the Monte Carlo simulation data that these percolative backbones emerge at specific critical points as a result of continuous phase transitions. These geometric transitions belong to the DP universality class and their nonlocal order parameters are the capacities of corresponding backbones. The multitude of conceivable percolative backbones implies the existence of infinite cascades of such geometric transitions in the kinetic processes considered. We present simple arguments to support the conjecture that such cascades of transitions are a generic feature of percolation as well as of many other transitions with nonlocal order parameters.

  8. Spin-current probe for phase transition in an insulator

    Science.gov (United States)

    Qiu, Zhiyong; Li, Jia; Hou, Dazhi; Arenholz, Elke; N'Diaye, Alpha T.; Tan, Ali; Uchida, Ken-ichi; Sato, Koji; Okamoto, Satoshi; Tserkovnyak, Yaroslav; Qiu, Z. Q.; Saitoh, Eiji

    2016-01-01

    Spin fluctuation and transition have always been one of the central topics of magnetism and condensed matter science. Experimentally, the spin fluctuation is found transcribed onto scattering intensity in the neutron-scattering process, which is represented by dynamical magnetic susceptibility and maximized at phase transitions. Importantly, a neutron carries spin without electric charge, and therefore it can bring spin into a sample without being disturbed by electric energy. However, large facilities such as a nuclear reactor are necessary. Here we show that spin pumping, frequently used in nanoscale spintronic devices, provides a desktop microprobe for spin transition; spin current is a flux of spin without an electric charge and its transport reflects spin excitation. We demonstrate detection of antiferromagnetic transition in ultra-thin CoO films via frequency-dependent spin-current transmission measurements, which provides a versatile probe for phase transition in an electric manner in minute devices. PMID:27573443

  9. Origin of time before inflation from a topological phase transition

    Science.gov (United States)

    Bellini, Mauricio

    2017-09-01

    We study the origin of the universe (or pre-inflation) by suggesting that the primordial space-time in the universe suffered a global topological phase transition, from a 4D Euclidean manifold to an asymptotic 4D hyperbolic one. We introduce a complex time, τ, such that its real part becomes dominant after started the topological phase transition. Before the big bang, τ is a space-like coordinate, so that can be considered as a reversal variable. After the phase transition is converted in a causal variable. The formalism solves in a natural manner the quantum to classical transition of the geometrical relativistic quantum fluctuations: σ, which has a geometric origin.

  10. The Physics of Phase Transitions Concepts and Applications

    CERN Document Server

    Papon, Pierre; Meijer, Paul H.E

    2006-01-01

    The physics of phase transitions is an important area at the crossroads of several fields that play central roles in materials sciences. In this second edition, new developments had been included which came up in the states of matter physics, in particular in the domain of nanomaterials and atomic Bose-Einstein condensates where progress is accelerating. The presentation of several chapters had been improved by bringing better information on some phase transition mechanisms and by illustrating them with new application examples. This work deals with all classes of phase transitions in fluids and solids. It contains chapters on evaporation, melting, solidification, magnetic transitions, critical phenomena, superconductivity, etc., and is intended for graduate students in physics and engineering; for scientists it will serve both as an introduction and an overview. End-of-chapter problems and complete answers are included.

  11. Structural phase transitions and topological defects in ion Coulomb crystals

    Energy Technology Data Exchange (ETDEWEB)

    Partner, Heather L. [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany); Nigmatullin, Ramil [Institute of Quantum Physics, Ulm Univ., Ulm (Germany); Burgermeister, Tobias [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany); Keller, Jonas [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany); Pyka, Karsten [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany); Plenio, Martin B. [Center for Integrated Quantum Science and Technology, Ulm Univ., Ulm, (Germany):Institute for Theoretical Physics, Ulm Univ.,Ulm, (Germany); Retzker, Alex [Racah Institute of Physics, The Hebrew University of Jerusalem, Givat Ram (Israel); Zurek, Wojciech Hubert [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); del Campo, Adolfo [Univ. of Massachusetts, Amherst, MA (United States). Dept. of Physics; Mehlstaubler, Tanja E. [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany)

    2014-11-19

    We use laser-cooled ion Coulomb crystals in the well-controlled environment of a harmonic radiofrequency ion trap to investigate phase transitions and defect formation. Topological defects in ion Coulomb crystals (kinks) have been recently proposed for studies of nonlinear physics with solitons and as carriers of quantum information. Defects form when a symmetry breaking phase transition is crossed non-adiabatically. For a second order phase transition, the Kibble-Zurek mechanism predicts that the formation of these defects follows a power law scaling in the rate of the transition. We demonstrate a scaling of defect density and describe kink dynamics and stability. We further discuss the implementation of mass defects and electric fields as first steps toward controlled kink preparation and manipulation.

  12. The liquid-liquid phase transition in dense hydrogen

    Science.gov (United States)

    Ceperley, David; Pierleoni, Carlo; Holzmann, Markus; Morales, Miguel

    The phase diagram of high pressure hydrogen is of great interest for fundamental research. A first-order phase transition in the fluid phase between a molecular insulating fluid and a monoatomic metallic fluid has been long anticipated. Recent experiments reported contrasting results about the location of the transition and theoretical results are very uncertain. We report highly accurate coupled electron-ion quantum Monte Carlo calculations of this transition, finding results that lie between the two experimental predictions, close to that measured in diamond anvil cell experiments but at 25-30 GPa higher pressure. The transition along an isotherm is signaled by a discontinuity in the specific volume, a sudden dissociation of the molecules, a jump in electrical conductivity and loss of electron localization. Funding from DOE NA DE-NA0001789 and DE-AC52-07NA27344. Computer time from PRACE and Blue Waters.

  13. Pressure-induced reversible phase transition in thiourea dioxide crystal

    Science.gov (United States)

    Wang, Qinglei; Yan, Tingting; Wang, Kai; Zhu, Hongyang; Cui, Qiliang; Zou, Bo

    2015-06-01

    The effect of high pressure on the crystal structure of thiourea dioxide has been investigated by Raman spectroscopy and angle-dispersive X-ray diffraction (ADXRD) in a diamond anvil cell up to 10.3 GPa. The marked changes in the Raman spectra at 3.7 GPa strongly indicated a structural phase transition associated with the distortions of hydrogen bonding. There were no further changes up to the maximum pressure of 10.3 GPa and the observed transition was completely reversible when the system was brought back to ambient pressure. This transition was further confirmed by the changes of ADXRD spectra. The high-pressure phase was indexed and refined to an orthorhombic structure with a possible space group Pbam. The results from the first-principles calculations suggested that this phase transition was mainly related to the changes of hydrogen-bonded networks in thiourea dioxide.

  14. Pressure-induced reversible phase transition in thiourea dioxide crystal

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Qinglei; Yan, Tingting; Zhu, Hongyang; Cui, Qiliang; Zou, Bo, E-mail: kaiwang@jlu.edu.cn, E-mail: zoubo@jlu.edu.cn [State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China); Wang, Kai, E-mail: kaiwang@jlu.edu.cn, E-mail: zoubo@jlu.edu.cn [State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China); College of Chemistry, Jilin University, Changchun 130012 (China)

    2015-06-28

    The effect of high pressure on the crystal structure of thiourea dioxide has been investigated by Raman spectroscopy and angle-dispersive X-ray diffraction (ADXRD) in a diamond anvil cell up to 10.3 GPa. The marked changes in the Raman spectra at 3.7 GPa strongly indicated a structural phase transition associated with the distortions of hydrogen bonding. There were no further changes up to the maximum pressure of 10.3 GPa and the observed transition was completely reversible when the system was brought back to ambient pressure. This transition was further confirmed by the changes of ADXRD spectra. The high-pressure phase was indexed and refined to an orthorhombic structure with a possible space group Pbam. The results from the first-principles calculations suggested that this phase transition was mainly related to the changes of hydrogen-bonded networks in thiourea dioxide.

  15. Analytic model for low energy excitation states and phase transitions in spin-ice systems

    Science.gov (United States)

    López-Bara, F. I.; López-Aguilar, F.

    2017-04-01

    Low energy excitation states in magnetic structures of the so-called spin-ices are produced via spin flips among contiguous tetrahedra of their crystal structure. These spin flips generate entities which mimic magnetic dipoles in every two tetrahedra according to the dumbbell model. When the temperature increases, the spin-flip processes are transmitted in the lattice, generating so-called Dirac strings, which constitute structural entities that can present mimetic behavior similar to that of magnetic monopoles. In recent studies of both specific heat and ac magnetic susceptibility, two (even possibly three) phases have been shown to vary the temperature. The first of these phases presents a sharp peak in the specific heat and another phase transition occurs for increasing temperature whose peak is broader than that of the former phase. The sharp peak occurs when there are no free individual magnetic charges and temperature of the second phase transition coincides with the maximum proliferation of free deconfined magnetic charges. In the present paper, we propose a model for analyzing the low energy excitation many-body states of these spin-ice systems. We give analytical formulas for the internal energy, specific heat, entropy and their temperature evolution. We study the description of the possible global states via the nature and structure of their one-body components by means of the thermodynamic functions. Below 0.37 K, the Coulomb-like magnetic charge interaction can generate a phase transition to a condensation of pole-antipole pairs, possibly having Bose-Einstein structure which is responsible for the sharp peak of the first phase transition. When there are sufficient free positive and negative charges, the system tends to behave as a magnetic plasma, which implies the broader peak in the specific heat appearing at higher temperature than the sharper experimental peak.

  16. Analytic model for low energy excitation states and phase transitions in spin-ice systems.

    Science.gov (United States)

    López-Bara, F I; López-Aguilar, F

    2017-04-20

    Low energy excitation states in magnetic structures of the so-called spin-ices are produced via spin flips among contiguous tetrahedra of their crystal structure. These spin flips generate entities which mimic magnetic dipoles in every two tetrahedra according to the dumbbell model. When the temperature increases, the spin-flip processes are transmitted in the lattice, generating so-called Dirac strings, which constitute structural entities that can present mimetic behavior similar to that of magnetic monopoles. In recent studies of both specific heat and ac magnetic susceptibility, two (even possibly three) phases have been shown to vary the temperature. The first of these phases presents a sharp peak in the specific heat and another phase transition occurs for increasing temperature whose peak is broader than that of the former phase. The sharp peak occurs when there are no free individual magnetic charges and temperature of the second phase transition coincides with the maximum proliferation of free deconfined magnetic charges. In the present paper, we propose a model for analyzing the low energy excitation many-body states of these spin-ice systems. We give analytical formulas for the internal energy, specific heat, entropy and their temperature evolution. We study the description of the possible global states via the nature and structure of their one-body components by means of the thermodynamic functions. Below 0.37 K, the Coulomb-like magnetic charge interaction can generate a phase transition to a condensation of pole-antipole pairs, possibly having Bose-Einstein structure which is responsible for the sharp peak of the first phase transition. When there are sufficient free positive and negative charges, the system tends to behave as a magnetic plasma, which implies the broader peak in the specific heat appearing at higher temperature than the sharper experimental peak.

  17. Phase transitions of natural corals monitored by ESR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Vongsavat, V. [Department of Chemistry, Faculty of Science, Mahidol University, Rama VI Road, Rajathevi, Bangkok 10400 (Thailand); Winotai, P. [Department of Chemistry, Faculty of Science, Mahidol University, Rama VI Road, Rajathevi, Bangkok 10400 (Thailand); Meejoo, S. [Department of Chemistry, Faculty of Science, Mahidol University, Rama VI Road, Rajathevi, Bangkok 10400 (Thailand)]. E-mail: scsmj@mahidol.ac.th

    2006-01-15

    The main purpose of this work is to present a systematic study of structure of marine exoskeletons, Acropora coral and its structural transformation upon heat treatments. The coralline sample was ground and characterized as powder throughout this work. Structural identifications of all samples have been confirmed using X-ray diffraction and IR spectroscopy. It was clearly found that the fresh specimen is made of aragonite, a common phase of the mineral CaCO{sub 3}. Thermal analyses, DSC and TGA were used to monitor structural and thermal decompositions and an irreversible solid-state phase transition from aragonite to calcite of the marine carbonate. Next, the coral powder was annealed at specific temperatures over the range 350-900 deg. C, and the effects of heat treatment on the structure of coralline samples were carefully studied by Rietveld refinement method. In addition, we have examined Mn{sup 2+} paramagnetic ions and free radicals present in the coral and changes of those upon heating by using ESR spectroscopy. The local environments of Mn{sup 2+} ions were verified from the calculated ESR spectra using appropriate spin Hamiltonian parameters, i.e. gyromagnetic tensor g , zero-field splitting D and hyperfine tensor A . This work reported structures and compositions as well as physical, chemical and thermal properties of the coralline material upon heat treatments qualitatively and quantitatively.

  18. Field induced quantum phase transition in the anisotropic spin ladder

    Energy Technology Data Exchange (ETDEWEB)

    Rezania, Hamed, E-mail: rezania.hamed@gmail.com [Department of Physics, Razi University, Kermanshah (Iran, Islamic Republic of); Jesri, Sounya [Department of Physics, Razi University, Kermanshah (Iran, Islamic Republic of)

    2013-02-15

    We have studied the quantum phase transition between antiferromagnetic and spin liquid phases for field induced quasi-one dimensional spin ladder model Hamiltonian. Using bond operator formalism, the original spin Hamiltonian is mapped to bosonic one. Green's function approach has been implemented to get the low energy spectrum and the corresponding structure factor. The critical field (B{sub c}) for a fixed coupling exchange between two rungs is found based on the Bose-Einstein condensation of quasi-particles (triplons) which takes place when the spin excitation spectrum vanishes at the antiferromagnetic wave vector. We have investigated the effect of both intersite ({delta}) and local ({Delta}) anisotropy on the critical field, critical coupling exchange and transverse static structure factor of the field induced quasi-one dimensional antiferromagnetic anisotropic spin ladder model at zero temperature. We have also studied the divergent behavior of static spin structure factor when magnetic field approaches the critical point. - Highlights: Black-Right-Pointing-Pointer The calculation of quantum critical field of spin ladder Hamiltonian by Green's function approach. Black-Right-Pointing-Pointer The study of behavior of energy gap of spin excitation spectrum versus field and anisotropies. Black-Right-Pointing-Pointer The investigation of behavior of transverse structure factor in terms of magnetic field.

  19. Phase transition properties of a cylindrical ferroelectric nanowire

    Indian Academy of Sciences (India)

    In the present paper, we apply the mean-field theory to investigate the phase transition properties of a cylindrical ferroelectric nanowire by taking into account two different exchange interactions and two different transverse field parameters in the. TIM. The effects of various parameters on the phase diagrams are given, and ...

  20. Nonequilibrium Phase Transition in Spin-S Ising Ferromagnet Driven by Propagating and Standing Magnetic Field Wave

    Science.gov (United States)

    Halder, Ajay; Acharyya, Muktish

    2017-11-01

    The dynamical response of spin-S (S=1, 3/2, 2, 3) Ising ferromagnet to the plane propagating wave, standing magnetic field wave and uniformly oscillating field with constant frequency are studied separately in two dimensions by extensive Monte Carlo simulation. Depending upon the strength of the magnetic field and the value of the spin state of the Ising spin lattice two different dynamical phases are observed. For a fixed value of S and the amplitude of the propagating magnetic field wave the system undergoes a dynamical phase transition from propagating phase to pinned phase as the temperature of the system is cooled down. Similarly in case with standing magnetic wave the system undergoes dynamical phase transition from high temperature phase where spins oscillate coherently in alternate bands of half wavelength of the standing magnetic wave to the low temperature pinned or spin frozen phase. For a fixed value of the amplitude of magnetic field oscillation the transition temperature is observed to decrease to a limiting value as the value of spin S is increased. The time averaged magnetisation over a full cycle of the magnetic field oscillation plays the role of the dynamic order parameter. A comprehensive phase boundary is drawn in the plane of magnetic field amplitude and dynamic transition temperature. It is found that the phase boundary shrinks inwards for high value of spin state S. Also in the low temperature (and high field) region the phase boundaries are closely spaced.

  1. Phase transition study in strongly correlated VO{sub 2} based sensing systems

    Energy Technology Data Exchange (ETDEWEB)

    Simo, A., E-mail: alinesimo.aline@gmail.com [UNESCO-UNISA Africa Chair in Nanoscience’s/Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape Province (South Africa); Kaviyarasu, K. [UNESCO-UNISA Africa Chair in Nanoscience’s/Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape Province (South Africa); Mwakikunga, B. [Council for Scientific and Industrial Research, P.O. Box 395, Pretoria 0001 (South Africa); Madjoe, R. [Physics Department, University of Western Cape, 7535 Belville Cape Town (South Africa); Gibaud, A. [Laboratoire de Physique de l’Etat Condensé, Université du Maine Faculte des sciences, UPRESA 6087, 72085, Le Mans Cedex 9 (France); Maaza, M. [UNESCO-UNISA Africa Chair in Nanoscience’s/Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape Province (South Africa)

    2017-04-15

    Highlights: • At 230 °C for about 48 h to prepare successfully VO{sub 2} nanobelts. • 1D shows good sensing performance due to the large active surface of the material. • The good selectivity of methanol compared to acetone and isopropanol. • VOC compounds was observed at room temperature. - Abstract: Intermediate phase monoclinic M2 was observed by inducing in situ X-ray thermo diffraction on VO{sub 2} (M) nanoplatelets. The solid-solid phase transition occurs at around 65 °C assisted with the percolative transition metal-insulator. The existence of an intermediate crystalline phase with room temperature insulator phase and high temperature metallic phase across MIT in VO{sub 2} could be of relevance to understand structural contributions to the phase transition dynamics. In addition, pellet of VO{sub 2} nanostructures have shown to present good sensing properties to various alcohols vapors at room temperature and good selectivity of methanol with 5.54% sensitivity and limit detection below 5 ppm, compared to isopropanol 3.2% and acetone 2.4% respectively.

  2. Investigating the solid-liquid phase transition of water nanofilms using the generalized replica exchange method

    Science.gov (United States)

    Lu, Qing; Kim, Jaegil; Farrell, James D.; Wales, David J.; Straub, John E.

    2014-11-01

    The generalized Replica Exchange Method (gREM) was applied to study a solid-liquid phase transition in a nanoconfined bilayer water system using the monatomic water (mW) model. Exploiting optimally designed non-Boltzmann sampling weights with replica exchanges, gREM enables an effective sampling of configurations that are metastable or unstable in the canonical ensemble via successive unimodal energy distributions across phase transition regions, often characterized by S-loop or backbending in the statistical temperature. Extensive gREM simulations combined with Statistical Temperature Weighted Histogram Analysis Method (ST-WHAM) for nanoconfined mW water at various densities provide a comprehensive characterization of diverse thermodynamic and structural properties intrinsic to phase transitions. Graph representation of minimized structures of bilayer water systems determined by the basin-hopping global optimization revealed heterogeneous ice structures composed of pentagons, hexagons, and heptagons, consistent with an increasingly ordered solid phase with decreasing density. Apparent crossover from a first-order solid-liquid transition to a continuous one in nanoconfined mW water with increasing density of the system was observed in terms of a diminishing S-loop in the statistical temperature, smooth variation of internal energies and heat capacities, and a characteristic variation of lateral radial distribution functions, and transverse density profiles across transition regions.

  3. THE NEXT GENERATION TRANSIT SURVEY PROTOTYPING PHASE

    OpenAIRE

    McCormac, J.; Pollacco, D.; The NGTS Consortium

    2014-01-01

    El Next Generation Transit Survey (NGTS) es un nuevo sondeo d e exoplanetas transitantes de campo amplio que tiene como objetivo descubrir exoplanetas del tama ̃no d e Neptuno y super-Tierras entorno a estrellas brillantes ( V < 13) cercanas. NGTS consiste de un arreglo de 12 telescopios o perados rob ́oticamente observando en la banda de 600 − 900 nm. NGTS sondear ́a m ́as de cinco veces el n ́umero de estre llas, con V < 13, que Kepler y por lo tanto proveer ́a los objetivos m ́as brillante...

  4. Continuous Phase Transitions in two Dimensional Systems.

    Science.gov (United States)

    1986-05-01

    CRITICAL BEHAVIOR. Davisson and Germer probably made the first observation of a surface order- disorder transition in their classic paper on electron...47. P. A. Bennett and M. B. Webb, Surface Sci. 148, 74 (1981 ). 48. K. Liang and W. N. Unertl, private communication. 49. C. J. Davisson and L. M... Germer , Phys. Rev. 30, 705 (1927). 50. A. U. MacRae, Surface Sci. 1, 319 (1964). 51. D.E. Taylor and R.L. Park, Surface Sci. L33, 125 (1983). 52. V. S

  5. Non-equilibrium quantum phase transition via entanglement decoherence dynamics

    Science.gov (United States)

    Lin, Yu-Chen; Yang, Pei-Yun; Zhang, Wei-Min

    2016-10-01

    We investigate the decoherence dynamics of continuous variable entanglement as the system-environment coupling strength varies from the weak-coupling to the strong-coupling regimes. Due to the existence of localized modes in the strong-coupling regime, the system cannot approach equilibrium with its environment, which induces a nonequilibrium quantum phase transition. We analytically solve the entanglement decoherence dynamics for an arbitrary spectral density. The nonequilibrium quantum phase transition is demonstrated as the system-environment coupling strength varies for all the Ohmic-type spectral densities. The 3-D entanglement quantum phase diagram is obtained.

  6. Phase transitions in warped AdS{sub 3} gravity

    Energy Technology Data Exchange (ETDEWEB)

    Detournay, Stéphane; Zwikel, Céline [Physique Théorique et Mathématique,Université Libre de Bruxelles and International Solvay Institutes, Campus Plaine C.P. 231, B-1050 Bruxelles (Belgium)

    2015-05-14

    We consider asymptotically Warped AdS{sub 3} black holes in Topologically Massive Gravity. We study their thermodynamic stability and show the existence of a Hawking-Page phase transition between the black hole and thermal background phases. At zero angular potential, the latter is shown to occur at the self-dual point of the dual Warped Conformal Field Theory partition function, in analogy with the phase transition for BTZ black holes in AdS{sub 3}/CFT{sub 2}. We also discuss how the central and vacuum charges can be obtained from inner horizon mechanics in the presence of a gravitational anomaly.

  7. Weyl semimetal and topological phase transition in five dimensions

    Science.gov (United States)

    Lian, Biao; Zhang, Shou-Cheng

    2017-06-01

    We study two Weyl semimetal generalizations in five dimensions (5D) which have Yang monopoles and linked Weyl surfaces in the Brillouin zone, respectively, and carry the second Chern number as a topological number. In particular, we show a Yang monopole naturally reduces to a Hopf link of two Weyl surfaces when the TP (time reversal combined with space inversion) symmetry is broken. We then examine the phase transition between insulators with different topological numbers in 5D. In analogy to the three-dimensional case, 5D Weyl semimetals emerge as intermediate phases during the topological phase transition.

  8. Non-equilibrium quantum phase transition via entanglement decoherence dynamics.

    Science.gov (United States)

    Lin, Yu-Chen; Yang, Pei-Yun; Zhang, Wei-Min

    2016-10-07

    We investigate the decoherence dynamics of continuous variable entanglement as the system-environment coupling strength varies from the weak-coupling to the strong-coupling regimes. Due to the existence of localized modes in the strong-coupling regime, the system cannot approach equilibrium with its environment, which induces a nonequilibrium quantum phase transition. We analytically solve the entanglement decoherence dynamics for an arbitrary spectral density. The nonequilibrium quantum phase transition is demonstrated as the system-environment coupling strength varies for all the Ohmic-type spectral densities. The 3-D entanglement quantum phase diagram is obtained.

  9. Plasma phase transition in hydrogen and electron-hole plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Filinov, V.; Levashov, P.; Fortov, V. [Institute for High Energy Density, Russian Academy of Sciences, Izhorskay 13/19, Moscow 127412 (Russian Federation); Bonitz, M. [Fachbereich Physik, Universitaet Rostock, D-18051 Rostock (Germany); Ebeling, W. [Institut fuer Physik, Humboldt-Universitaet Berlin Invalidenstrasse 110, D-10115 Berlin (Germany); Schlanges, M. [Fachbereich Physik, Universitaet Greifswald, D-17489 Greifswald (Germany)

    2003-10-01

    The plasma phase transition in dense hydrogen and in electron-hole plasmas is investigated by direct path integral Monte Carlo simulations. Hydrogen results for the internal energy at T=10,000 K show a deep minimum and strong fluctuations around the density n=10{sup 23} cm{sup -3} indicating the existence of a phase transition. To verify this explanation, the analogous phenomenon is studied for an electron-hole plasma in Germanium. The calculated phase boundary of the electron-hole liquid is found to agree reasonably well with the available experimental data. (copyright 2003 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. Pressure-Driven Commensurate-Incommensurate Transition Low-Temperature Submonolayer Krypton on Graphite

    DEFF Research Database (Denmark)

    Nielsen, Mourits; Als-Nielsen, Jens Aage; Bohr, Jakob

    1981-01-01

    By using D2 gas as a source of two-dimensional spreading pressure, we have studied the commensurate-incommensurate (C-I) transition in submonolayer Kr on ZYX graphite at temperatures near 40 K. High-resolution synchrotron x-ray diffraction results show both hysteresis and C-I phase coexistence, c...

  11. Solid state phase transition and vapor pressure studies in ammonium nitrate-potassium nitrate binary system

    Science.gov (United States)

    Chien, Wen-Ming

    The solid-state phase transitions in ammonium nitrate (NH4NO 3) and potassium nitrate (KNO3) solid solutions and the equilibrium NH4NO3-KNO3 (AN-KN) phase diagram have been determined. The phase transitions and phase diagram were determined by using the differential scanning calorimetry (DSC) and high temperature X-ray diffractometry. Samples of several different compositions were made for these analyses in a special "Dry Room" with very low humidity. In the X-ray diffraction experiments, the samples were heated on Pt-Rh strip and LaB6 or Si was added for internal calibration. Equilibrium phase diagram was also calculated by using the "FactSage" computer program. A single (AN III) phase region without any phase transitions between 293 to 373 K was observed for compositions between 5 to 25wt% KNO3 in NH4NO3 that is critical for air bag gas generators. The higher temperature KNO3 (KN I) phase has a wide stability range, from 100%KNO3 to 20%KNO3 solution. There is one eutectic, two eutectoids, and two peritectoids in this phase diagram. Two newly discovered solid-state phases were found in the mid-composition range of AN-KN solid solutions. Details of phase equilibria and lattice expansions during heating have been determined. Phase diagram calculations show a reasonable match of the phase boundaries. The total vapor pressures as well as the average molecular weights of pure ammonium nitrate and 16% KNO3 solid solution were measured at various temperatures by the torsion-Knudsen effusion method. The partial pressures of NH4NO3 (PNH4NO 3), NH3 (PNH3), and HNO3 (PHNO 3) have also been determined.

  12. Scaling Concepts in Describing Continuous Phase Transitions

    Indian Academy of Sciences (India)

    research addresses the behaviour of liquids and disordered soft matter, including glassy .... interesting discussion of Landau theory is found in a 'Classroom' article by. Rekha S Raorane et al, The Landau Theory of Phase ..... action strength and applied fields. In other words, a block spin transformation maps the system from ...

  13. Influences of P doping on magnetic phase transition and structure in MnCoSi ribbon

    Science.gov (United States)

    Du, Qian-Heng; Chen, Guo-Fu; Yang, Wen-Yun; Hua, Mu-Xin; Du, Hong-Lin; Wang, Chang-Sheng; Liu, Shun-Quan; Hang, Jing-Zhi; Zhou, Dong; Zhang, Yan; Yan, Jin-Bo

    2015-06-01

    The structure and magnetic properties of MnCoSi1- x Px (x = 0.05-0.50) are systematically investigated. With P content increasing, the lattice parameter a increases monotonically while both b and c decrease. At the same time, the temperature of metamagnetic transition from a low-temperature non-collinear ferromagnetic state to a high-temperature ferromagnetic state decreases and a new magnetic transition from a higher-magnetization ferromagnetic state to a lower-magnetization ferromagnetic state is observed in each of these compounds for the first time. This is explained by the changes of crystal structure and distance between Mn and Si atoms with the increase of temperature according to the high-temperature XRD result. The metamagnetic transition is found to be a second-order magnetic transition accompanied by a low inversed magnetocaloric effect (1.0 J·kg-1·K-1 at 5 T) with a large temperature span (190 K at 5 T) compared with the scenario of MnCoSi. The changes in the order of metamagnetic transition and structure make P-doped MoCoSi compounds good candidates for the study of magnetoelastic coupling and the modulation of magnetic phase transition. Project supported by the National Natural Science Foundation of China (Grant No. 11275013), the Fund from the National Physics Laboratory, China Academy of Engineering Physics (Grant No. 2013DB01), and the National Key Basic Research Program of China (Grant No. 2010CB833104).

  14. Spin transition of ferric iron in the calcium-ferrite type aluminous phase: Fe 3+ Spin Transition in the CF Phase

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Ye [School of Science, Wuhan University of Technology, Wuhan China; Qin, Fei [Key Laboratory of Orogenic Belts and Crustal Evolution, MOE, and School of Earth and Space Sciences, Peking University, Beijing China; Wu, Xiang [State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan China; Huang, Haijun [School of Science, Wuhan University of Technology, Wuhan China; McCammon, Catherine A. [Bayerisches Geoinstitut, Universität Bayreuth, Bayreuth Germany; Yoshino, Takashi [Institute for Planetary Materials, Okayama University, Misasa Japan; Zhai, Shuangmeng [Key Laboratory of High-temperature and High-pressure Study of the Earth' s Interior, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang China; Xiao, Yuming [HPCAT, Geophysical Laboratory, Carnegie Institution of Washington, Argonne Illinois USA; Prakapenka, Vitali B. [GeoSoilEnviroCARS, University of Chicago, Chicago Illinois USA

    2017-08-01

    We investigated Fe-free and Fe-bearing CF phases using nuclear forward scattering and X-ray diffraction coupled with diamond anvil cells up to 80 GPa at room temperature. Octahedral Fe3+ ions in the Fe-bearing CF phase undergo a high-spin to low-spin transition at 25–35 GPa, accompanied by a volume reduction of ~2.0% and a softening of bulk sound velocity up to 17.6%. Based on the results of this study and our previous studies, both the NAL and CF phases, which account for 10–30 vol % of subducted MORB in the lower mantle, are predicted to undergo a spin transition of octahedral Fe3+ at lower mantle pressures. Spin transitions in these two aluminous phases result in an increase of density of 0.24% and a pronounced softening of bulk sound velocity up to 2.3% for subducted MORB at 25–60 GPa and 300 K. The anomalous elasticity region expands and moves to 30–75 GPa at 1200 K and the maximum of the VΦ reduction decreases to ~1.8%. This anomalous elastic behavior of Fe-bearing aluminous phases across spin transition zones may be relevant in understanding the observed seismic signatures in the lower mantle.

  15. A High-Pressure Phase Transition of Calcite-III

    Science.gov (United States)

    Catalli, K. C.; Williams, Q.

    2005-12-01

    We document the presence of a high-pressure phase transition in metastable calcite-III using infrared spectroscopy. The post-calcite-III transition initiates at a pressure of 15.5 (±2) GPa, and is completed between 25 and 30 GPa. The transition is particularly apparent in the ν4-in-plane bending vibration of the carbonate group, in which two new peaks gradually supplant the doublet associated with calcite-III. Furthermore, both the ν3-asymmetric and ν1-symmetric stretches of the carbonate group in the high-pressure phase appear at considerably lower frequencies than the extrapolated positions of the corresponding calcite-III peaks. The geometry of the carbonate unit within the high-pressure phase is likely closer to trigonal symmetry than in the calcite-III structure, and the C-O bond is probably longer than in the lower pressure calcite-III phase.

  16. Oxygen vacancies dependent phase transition of Y2O3 films

    Science.gov (United States)

    Yu, Pengfei; Zhang, Kan; Huang, Hao; Wen, Mao; Li, Quan; Zhang, Wei; Hu, Chaoquan; Zheng, Weitao

    2017-07-01

    Y2O3 films have great application potential in high-temperature metal matrix composite and nuclear engineering, used as interface diffusion and reaction barrier coating owing to their excellent thermal and chemical stability, high melting point and extremely negative Gibbs formation energy, and thus their structural and mechanical properties at elevated temperature are especially important. Oxygen vacancies exist commonly in yttrium oxide (Y2O3) thin films and act strongly on the phase structure and properties, but oxygen vacancies dependent phase transition at elevated temperature has not been well explored yet. Y2O3 thin films with different oxygen vacancy concentrations have been achieved by reactive sputtering through varying substrate temperature (Ts), in which oxygen vacancies increase monotonously with increasing Ts. For as-deposited Y2O3 films, oxygen vacancies present at high Ts can promote the nucleation of monoclinic phase, meanwhile, high Ts can induce the instability of monoclinic phase. Thus their competition results in forming mixed phases of cubic and monoclinic at high Ts. During vacuum annealing at 1000 °C, a critical oxygen vacancy concentration is observed, below which phase transition from monoclinic to cubic takes place, and above which phase transfer from monoclinic to the oxygen defective phase (ICDD file no. 39-1063), accompanying by stress reversal from compressive to tensile and maintenance of high hardness.

  17. Gravitational waves from the sound of a first order phase transition.

    Science.gov (United States)

    Hindmarsh, Mark; Huber, Stephan J; Rummukainen, Kari; Weir, David J

    2014-01-31

    We report on the first three-dimensional numerical simulations of first-order phase transitions in the early Universe to include the cosmic fluid as well as the scalar field order parameter. We calculate the gravitational wave (GW) spectrum resulting from the nucleation, expansion, and collision of bubbles of the low-temperature phase, for phase transition strengths and bubble wall velocities covering many cases of interest. We find that the compression waves in the fluid continue to be a source of GWs long after the bubbles have merged, a new effect not taken properly into account in previous modeling of the GW source. For a wide range of models, the main source of the GWs produced by a phase transition is, therefore, the sound the bubbles make.

  18. Diffuse phase transition, piezoelectric and optical study of Bi0· 5Na0 ...

    Indian Academy of Sciences (India)

    The microstructure of the ceramic was investigated by scanning electron microscopic (SEM) technique. The temperature-dependent dielectric study of the sample sintered at 1150°C was done in the frequency range of 50 kHz–1 MHz which shows a diffuse phase transition. The piezoelectric constant (33) was found to be ...

  19. Indication of liquid-liquid phase transition in CuZr-based melts

    DEFF Research Database (Denmark)

    Zhou, C.; Hu, L.N.; Sun, Q.J.

    2013-01-01

    We study the dynamic behavior of CuZr-based melts well above the liquidus temperature. The results show a discontinuous change in viscosity during cooling, which is attributed to an underlying liquid-liquid phase transition (LLPT) in these melts. The LLPT is further verified by thermodynamic...

  20. First Order Electroweak Phase Transition from (Non)Conformal Extensions of the Standard Model

    DEFF Research Database (Denmark)

    Sannino, Francesco; Virkajärvi, Jussi

    2015-01-01

    We analyse and compare the finite-temperature electroweak phase transition properties of classically (non)conformal extensions of the Standard Model. In the classically conformal scenarios the breaking of the electroweak symmetry is generated radiatively. The models feature new scalars coupled co...... the associated models are testable at the upcoming Large Hadron Collider run two experiments....