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Sample records for high-pressure phase diagram

  1. The phase diagram of high-pressure superionic ice

    Science.gov (United States)

    Sun, Jiming; Clark, Bryan K.; Torquato, Salvatore; Car, Roberto

    2015-08-01

    Superionic ice is a special group of ice phases at high temperature and pressure, which may exist in ice-rich planets and exoplanets. In superionic ice liquid hydrogen coexists with a crystalline oxygen sublattice. At high pressures, the properties of superionic ice are largely unknown. Here we report evidence that from 280 GPa to 1.3 TPa, there are several competing phases within the close-packed oxygen sublattice. At even higher pressure, the close-packed structure of the oxygen sublattice becomes unstable to a new unusual superionic phase in which the oxygen sublattice takes the P21/c symmetry. We also discover that higher pressure phases have lower transition temperatures. The diffusive hydrogen in the P21/c superionic phase shows strong anisotropic behaviour and forms a quasi-two-dimensional liquid. The ionic conductivity changes abruptly in the solid to close-packed superionic phase transition, but continuously in the solid to P21/c superionic phase transition.

  2. Phase diagram of Mo at high pressure and temperature

    Energy Technology Data Exchange (ETDEWEB)

    Ross, M

    2008-10-01

    We report values of the Poisson Ratios for shock compressed Mo, calculated from the sound speed measurements, which provide evidence that the 210 GPa ({approx}4100K) transition cannot be a bcc-hcp transition, as originally proposed. Instead, we find the transition is from the bcc to a noncrystalline phase. For pressures above 210 GPa, the Poisson Ratio increases steadily with increasing temperature, approaching the liquid value of 0.5 at 390 GPa({approx}10,000K), suggesting the presence of a noncrystalline solid-liquid mixture. Free energy model calculations were used to show that the low melting slope of Mo, and the phase diagram, can be explained by the presence of local liquid structures. A new phase diagram is proposed for Mo that is constrained by the experimental evidence.

  3. High-pressure high-temperature phase diagram of organic crystal paracetamol

    Science.gov (United States)

    Smith, Spencer J.; Montgomery, Jeffrey M.; Vohra, Yogesh K.

    2016-01-01

    High-pressure high-temperature (HPHT) Raman spectroscopy studies have been performed on the organic crystal paracetamol in a diamond anvil cell utilizing boron-doped heating diamond anvil. Isobaric measurements were conducted at pressures up to 8.5 GPa and temperature up to 520 K in five different experiments. Solid state phase transitions from monoclinic Form I  →  orthorhombic Form II were observed at various pressures and temperatures as well as transitions from Form II  →  unknown Form IV. The melting temperature for paracetamol was observed to increase with increasing pressures to 8.5 GPa. This new data is combined with previous ambient temperature high-pressure Raman and x-ray diffraction data to create the first HPHT phase diagram of paracetamol.

  4. High-Pressure High-Temperature Phase Diagram of the Organic Crystal Paracetamol

    Science.gov (United States)

    Smith, Spencer; Montgomery, Jeffrey; Vohra, Yogesh

    High-pressure high-temperature (HPHT) Raman spectroscopy studies have been performed on the organic crystal paracetamol in a diamond anvil cell utilizing boron-doped diamond as heating anvil. The HPHT data obtained from boron-doped diamond heater is cross-checked with data obtained using a standard block heater diamond anvil cell. Isobaric measurements were conducted at pressures up to 8.5 GPa and temperature up to 520 K in a number of different experiments. Solid state phase transitions from monoclinic Form I --> orthorhombic Form II were observed at various pressures and temperatures as well as transitions from Form II --> unknown Form IV. The melting temperature for paracetamol was observed to increase with increasing pressures to 8.5 GPa. Our previous angle dispersive x-ray diffraction studies at the Advanced Photon Source has confirmed the existence of two unknown crystal structures Form IV and Form V of paracetamol at high pressure and ambient temperature. The phase transformation from Form II to Form IV occurs at ~8.5 GPa and from Form IV to Form V occurs at ~11 GPa at ambient temperature. Our new data is combined with the previous ambient temperature high-pressure Raman and X- ray diffraction data to create the first HPHT phase diagram of paracetamol. Doe-NNSA Carnegie DOE Alliance Center (CDAC) under Grant Number DE-NA0002006.

  5. Nuclear quantum and electronic exchange-correlation effects on the high pressure phase diagram of lithium

    Science.gov (United States)

    Clay, Raymond; Morales, Miguel; Bonev, Stanimir

    Lithium at ambient conditions is the simplest alkali metal and exhibits textbook nearly-free electron character. However, increased core/valence electron overlap under compression leads to surprisingly complex behavior. Dense lithium is known to posses a maximum in the melting line, a metal to semiconductor phase transition around 80GPa, reemergent metallicity around 120GPa, and low coordination solid and liquid phases. In addition to its complex electronic structure at high pressure, the atomic mass of lithium is low enough that nuclear quantum effects could have a nontrivial impact on its phase diagram. Through a combination of density functional theory based path-integral and classical molecular dynamics simulations, we have investigated the impact of both nuclear quantum effects and anharmonicity on the melting line and solid phase boundaries. Additionally, we have determined the robustness of previously predicted tetrahedral clustering in the dense liquid to the inclusion of nuclear quantum effects and approximate treatment of electronic exchange-correlation effects.

  6. Exploring the Phase Diagram SiO2-CO2 at High Pressures and Temperatures

    Science.gov (United States)

    Kavner, A.

    2015-12-01

    CO2 is an important volatile system relevant for planetary sciences and fundamental chemistry. Molecular CO2 has doubly bonded O=C=O units but high pressure-high temperature (HP-HT) studies have recently shown its transformation into a three-dimensional network of corner-linked [CO4] units analogous to the silica mineral polymorphs, through intermediate non-molecular phases. Here, we report P-V-T data on CO2-IV ice from time-of-flight neutron diffraction experiments, which allow determining the compressibility and thermal expansivity of this intermediate molecular-to-non-molecular phase.1 Aditionally, we have explored the SiO2-CO2 phase diagram and the potential formation of silicon carbonate compounds. New data obtained by laser-heating diamond-anvil experiments in CO2-filled microporous silica polymorphs will be shown. In particular, these HP-HT experiments explore the existence of potential CO2/SiO2 compounds with tetrahedrally-coordinated C/Si atoms by oxygens, which are predicted to be stable (or metastable) by state-of-the-art ab initio simulations.2,3 These theoretical predictions were supported by a recent study that reports the formation of a cristobalite-type Si0.4C0.6O2 solid solution at high-pressures and temperatures, which can be retained as a metastable solid down to ambient conditions.4 Entirely new families of structures could exist based on [CO4]4- units in various degrees of polymerisation, giving rise to a range of chain, sheet and framework solids like those found in silicate chemistry. References[1] S. Palaich et al., Am. Mineral. Submitted (2015) [2] A. Morales-Garcia et al., Theor. Chem. Acc. 132, 1308 (2013) [3] R. Zhou et al., Phys. Rev. X, 4, 011030 (2014) [4] M. Santoro et al. Nature Commun. 5, 3761 (2014)

  7. Combined high-pressure and high-temperature vibrational studies of dolomite: phase diagram and evidence of a new distorted modification

    Science.gov (United States)

    Efthimiopoulos, I.; Jahn, S.; Kuras, A.; Schade, U.; Koch-Müller, M.

    2017-02-01

    A combined high-pressure mid-infrared absorption and Raman spectroscopy study on a natural CaMg0.98Fe0.02(CO3)2 dolomite sample was performed both at ambient and high temperatures. A pressure-temperature phase diagram was constructed for all the reported dolomite ambient- and high-pressure polymorphs. In addition, a local distortion of the ambient-pressure dolomite structure was identified close to 11 GPa, just before the transition toward the first known high-pressure phase. All the Clausius-Clapeyron slopes are found to be positive with similar magnitudes. Complementary first-principles calculations suggest a metastable nature of the high-pressure dolomite polymorphs. Finally, theoretical spectroscopy is used to interpret and discuss the observed changes in the measured vibrational spectra.

  8. High-pressure phase diagram and equation of state of solid helium from single-crystal X-ray diffraction to 23.3 GPa

    Science.gov (United States)

    Mao, H. K.; Hemley, R. J.; Jephcoat, A. P.; Finger, L. W.; Wu, Y.

    1988-01-01

    Single-crystal X-ray diffraction measurements have been performed on solid He-4 from 15.6 to 23.3 GPa at 300 K with synchrotron radiation. The diffraction patterns demonstrate that the structure of the solid is hexagonal close packed over this pressure-temperature range, contrary to both the interpretation of high-pressure optical studies and to theoretical predictions. The solid is more compressible than is indicated by equations of state calculated with recently determined helium pair potentials. The results suggest that a significant revision of current views of the phase diagram and energetics of dense solid helium is in order.

  9. Physical properties and phase diagram of the magnetic compound Cr0.26NbS1.74 at high pressures

    Science.gov (United States)

    Sidorov, V. A.; Petrova, A. E.; Pinyagin, A. N.; Kolesnikov, N. N.; Khasanov, S. S.; Stishov, S. M.

    2016-06-01

    We report the results of a study of magnetic, electrical, and thermodynamic properties of a single crystal of the magnetic compound Cr0.26NbS1.74 at ambient and high pressures. Results of the measurements of magnetization as a function of temperature reveal the existence of a ferromagnetic phase transition in Cr0.26NbS1.74. The effective number of Bohr magnetons per Cr atom in the paramagnetic phase of Cr0.26NbS1.74 is µeff ≈ 4.6µB, which matches the literature data for Cr1/3NbS2. Similarly, the effective number of Bohr magnetons per Cr atom in the saturation fields is rather close in both substances and corresponds to the number of magnetons in the Cr+3 ion. In contrast to the stoichiometric compound, Cr0.26NbS1.74 does not show a metamagnetic transition, that indicates the lack of a magnetic soliton. A high-pressure phase diagram of the compound reveals the quantum phase transition at T = 0 and P ≈ 4.2 GPa and the triple point situated at T ≈ 20 K and P ≈ 4.2 GPa.

  10. The high-pressure phase diagram of Fe(0.94)O - A possible constituent of the earth's core

    Science.gov (United States)

    Knittle, Elise; Jeanloz, Raymond

    1991-01-01

    Electrical resistivity measurements to pressures of 83 GPa and temperatures ranging from 300 K to 4300 K confirm the presence of both crystalline and liquid metallic phases of FeO at pressures above 60-70 GPa and temperatures above 1000 K. By experimentally determinig the melting temperature of FeO to 100 GPa and of a model-core composition at 83 GPa, it is found that the solid-melt equilibria can be described by complete solid solution across the Fe-FeO system at pressures above 70 GPa. The results indicate that oxygen is a viable and likely candidate for the major light alloying element of the earth's liquid outer core. The data suggest that the temperature at the core-mantle boundary is close to 4800 K and that heat lost out of the core accounts for more than 20 percent of the heat flux observed at the surface.

  11. Phase Equilibria Diagrams Database

    Science.gov (United States)

    SRD 31 NIST/ACerS Phase Equilibria Diagrams Database (PC database for purchase)   The Phase Equilibria Diagrams Database contains commentaries and more than 21,000 diagrams for non-organic systems, including those published in all 21 hard-copy volumes produced as part of the ACerS-NIST Phase Equilibria Diagrams Program (formerly titled Phase Diagrams for Ceramists): Volumes I through XIV (blue books); Annuals 91, 92, 93; High Tc Superconductors I & II; Zirconium & Zirconia Systems; and Electronic Ceramics I. Materials covered include oxides as well as non-oxide systems such as chalcogenides and pnictides, phosphates, salt systems, and mixed systems of these classes.

  12. Atomic phase diagram

    Institute of Scientific and Technical Information of China (English)

    LI Shichun

    2004-01-01

    Based on the Thomas-Fermi-Dirac-Cheng model, atomic phase diagram or electron density versus atomic radius diagram describing the interaction properties of atoms of different kinds in equilibrium state is developed. Atomic phase diagram is established based on the two-atoms model. Besides atomic radius, electron density and continuity condition for electron density on interfaces between atoms, the lever law of atomic phase diagram involving other physical parameters is taken into account, such as the binding energy, for the sake of simplicity.

  13. Engineering holographic phase diagrams

    Science.gov (United States)

    Chen, Jiunn-Wei; Dai, Shou-Huang; Maity, Debaprasad; Zhang, Yun-Long

    2016-10-01

    By introducing interacting scalar fields, we tried to engineer physically motivated holographic phase diagrams which may be interesting in the context of various known condensed matter systems. We introduce an additional scalar field in the bulk which provides a tunable parameter in the boundary theory. By exploiting the way the tuning parameter changes the effective masses of the bulk interacting scalar fields, desired phase diagrams can be engineered for the boundary order parameters dual to those scalar fields. We give a few examples of generating phase diagrams with phase boundaries which are strikingly similar to the known quantum phases at low temperature such as the superconducting phases. However, the important difference is that all the phases we have discussed are characterized by neutral order parameters. At the end, we discuss if there exists any emerging scaling symmetry associated with a quantum critical point hidden under the dome in this phase diagram.

  14. Algorithmic phase diagrams

    Science.gov (United States)

    Hockney, Roger

    1987-01-01

    Algorithmic phase diagrams are a neat and compact representation of the results of comparing the execution time of several algorithms for the solution of the same problem. As an example, the recent results are shown of Gannon and Van Rosendale on the solution of multiple tridiagonal systems of equations in the form of such diagrams. The act of preparing these diagrams has revealed an unexpectedly complex relationship between the best algorithm and the number and size of the tridiagonal systems, which was not evident from the algebraic formulae in the original paper. Even so, for a particular computer, one diagram suffices to predict the best algorithm for all problems that are likely to be encountered the prediction being read directly from the diagram without complex calculation.

  15. Phase diagram of ammonium nitrate

    Science.gov (United States)

    Dunuwille, M.; Yoo, C. S.

    2014-05-01

    Ammonium Nitrate (AN) has often subjected to uses in improvised explosive devices, due to its wide availability as a fertilizer and its capability of becoming explosive with slight additions of organic and inorganic compounds. Yet, the origin of enhanced energetic properties of impure AN (or AN mixtures) is neither chemically unique nor well understood -resulting in rather catastrophic disasters in the past1 and thereby a significant burden on safety in using ammonium nitrates even today. To remedy this situation, we have carried out an extensive study to investigate the phase stability of AN at high pressure and temperature, using diamond anvil cells and micro-Raman spectroscopy. The present results confirm the recently proposed phase IV-to-IV' transition above 17 GPa2 and provide new constraints for the melting and phase diagram of AN to 40 GPa and 400 °C.

  16. Prediction of boron carbon nitrogen phase diagram

    Science.gov (United States)

    Yao, Sanxi; Zhang, Hantao; Widom, Michael

    We studied the phase diagram of boron, carbon and nitrogen, including the boron-carbon and boron-nitrogen binaries and the boron-carbon-nitrogen ternary. Based on the idea of electron counting and using a technique of mixing similar primitive cells, we constructed many ''electron precise'' structures. First principles calculation is performed on these structures, with either zero or high pressures. For the BN binary, our calculation confirms that a rhmobohedral phase can be stablized at high pressure, consistent with some experimental results. For the BCN ternary, a new ground state structure is discovered and an Ising-like phase transition is suggested. Moreover, we modeled BCN ternary phase diagram and show continuous solubility from boron carbide to the boron subnitride phase.

  17. Collective neurodynamics: Phase diagram

    OpenAIRE

    Ovchinnikov, Igor V.; Li, Wenyuan; Schwartz, Robert N.; Hudson, Andrew E.; Meier, Karlheinz; Wang, Kang L.

    2016-01-01

    Here, we conceptualize the phase diagram of collective short-term bio-chemo-electric component of neurodynamics (S-ND) on the parameter space of externally, e.g., pharmacologically, controllable single-neuron parameters such as the resting potential and/or firing threshold, repolarization time, etc. This concept may become a useful tool for the systematization of knowledge in anesthesiology and provide a fruitful venue for future studies of the high-level S-ND functionalities such as short-te...

  18. High-pressure fluid phase equilibria phenomenology and computation

    CERN Document Server

    Deiters, Ulrich K

    2012-01-01

    The book begins with an overview of the phase diagrams of fluid mixtures (fluid = liquid, gas, or supercritical state), which can show an astonishing variety when elevated pressures are taken into account; phenomena like retrograde condensation (single and double) and azeotropy (normal and double) are discussed. It then gives an introduction into the relevant thermodynamic equations for fluid mixtures, including some that are rarely found in modern textbooks, and shows how they can they be used to compute phase diagrams and related properties. This chapter gives a consistent and axiomatic approach to fluid thermodynamics; it avoids using activity coefficients. Further chapters are dedicated to solid-fluid phase equilibria and global phase diagrams (systematic search for phase diagram classes). The appendix contains numerical algorithms needed for the computations. The book thus enables the reader to create or improve computer programs for the calculation of fluid phase diagrams. introduces phase diagram class...

  19. Bonding in boron: building high-pressure phases from boron sheets

    Energy Technology Data Exchange (ETDEWEB)

    Kunstmann, Jens [Institute for Materials Science and Max Bergmann Center of Biomaterials, Dresden University of Technology (Germany); Boeri, Lilia [Max Planck Institute for Solid State Research, Stuttgart (Germany); Kortus, Jens [Institute for Theoretical Physics, TU Bergakademie Freiberg (Germany)

    2010-07-01

    We present the results of a study of the high pressure phase diagram of elemental boron, using full-potential density functional calculations. We show that at high pressures (P > 100 GPa) boron crystallizes in quasi-layered bulk phases, characterized by in-plane multicenter bonds and out-of-plane unidimensional sigma bonds. These structures are all metallic, in contrast to the low-pressure icosahedral ones, which are semiconducting. We show that the structure and bonding of layered bulk phases can be easily described in terms of single puckered boron sheets. Our results bridge the gap between boron nanostructures and bulk phases.

  20. Equations of State and Phase Diagrams of Ammonia

    Science.gov (United States)

    Glasser, Leslie

    2009-01-01

    We present equations of state relating the phases and a three-dimensional phase diagram for ammonia with its solid, liquid, and vapor phases, based on fitted authentic experimental data and including recent information on the high-pressure solid phases. This presentation follows similar articles on carbon dioxide and water published in this…

  1. Ion mixing and phase diagrams

    Science.gov (United States)

    Lau, S. S.; Liu, B. X.; Nicolet, M.-A.

    1983-05-01

    Interactions induced by ion irradiation are generally considered to be non-equilibrium processes, whereas phase diagrams are determined by phase equilibria. These two entities are seemingly unrelated. However, if one assumes that quasi-equilibrium conditions prevail after the prompt events, subsequent reactions are driven toward equilibrium by thermodynamical forces. Under this assumption, ion-induced reactions are related to equilibrium and therefore to phase diagrams. This relationship can be seen in the similarity that exists in thin films between reactions induced by ion irradiation and reactions induced by thermal annealing. In the latter case, phase diagrams have been used to predict the phase sequence of stable compound formation, notably so in cases of silicide formation. Ion-induced mixing not only can lead to stable compound formation, but also to metastable alloy formation. In some metal-metal systems, terminal solubilities can be greatly extended by ion mixing. In other cases, where the two constituents of the system have different crystal structures, extension of terminal solubility from both sides of the phase diagram eventually becomes structurally incompatible and a glassy (amorphous) mixture can form. The composition range where this bifurcation is likely to occur is in the two-phase regions of the phase diagram. These concepts are potentially useful guides in selecting metal pairs that from metallic glasses by ion mixing. In this report, phenomenological correlation between stable (and metastable) phase formation and phase diagram is discussed in terms of recent experimental data.

  2. Experimental methods for phase equilibria at high pressures.

    Science.gov (United States)

    Dohrn, Ralf; Fonseca, José M S; Peper, Stephanie

    2012-01-01

    Knowledge of high-pressure phase equilibria is crucial in many fields, e.g., for the design and optimization of high-pressure chemical and separation processes, carbon capture and storage, hydrate formation, applications of ionic liquids, and geological processes. This review presents the variety of methods to measure phase equilibria at high pressures and, following a classification, discusses the measurement principles, advantages, challenges, and error sources. Examples of application areas are given. A detailed knowledge and understanding of the different methods is fundamental not only for choosing the most suitable method for a certain task but also for the evaluation of experimental data. The discrepancy between the (sometimes low) true accuracy of published experimental data and the (high) accuracy claimed by authors is addressed. Some essential requirements for the generation of valuable experimental results are summarized.

  3. Synthesis of an orthorhombic high pressure boron phase

    Science.gov (United States)

    Zarechnaya, Evgeniya Yu; Dubrovinsky, Leonid; Dubrovinskaia, Natalia; Miyajima, Nobuyoshi; Filinchuk, Yaroslav; Chernyshov, Dmitry; Dmitriev, Vladimir

    2008-12-01

    The densest boron phase (2.52 g cm-3) was produced as a result of the synthesis under pressures above 9 GPa and temperatures up to ~1800 °C. The x-ray powder diffraction pattern and the Raman spectra of the new material do not correspond to those of any known boron phases. A new high-pressure high-temperature boron phase was defined to have an orthorhombic symmetry (Pnnm (No. 58)) and 28 atoms per unit cell.

  4. Phase equilibria in molecular hydrogen-helium mixtures at high pressures

    Science.gov (United States)

    Streett, W. B.

    1973-01-01

    Experiments on phase behavior in hydrogen-helium mixtures have been carried out at pressures up to 9.3 kilobars, at temperatures from 26 to 100 K. Two distinct fluid phases are shown to exist at supercritical temperatures and high pressures. Both the trend of the experimental results and an analysis based on the van der Waals theory of mixtures suggest that this fluid-fluid phase separation persists at temperatures and pressures beyond the range of these experiments, perhaps even to the limits of stability of the molecular phases. The results confirm earlier predictions concerning the form of the hydrogen-helium phase diagram in the region of pressure-induced solidification of the molecular phases at supercritical temperatures. The implications of this phase diagram for planetary interiors are discussed.

  5. Structural and magnetic phase transitions in NdCoAsO under high pressures

    Energy Technology Data Exchange (ETDEWEB)

    Uhoya, Walter; Tsoi, Georgiy M.; Vohra, Yogesh K.; McGuire, Michael A.; Sefat, Athena S.; Sales, Brian C.; Mandrus, David; Weir, Samuel T. (UAB); (ORNL); (LLNL)

    2010-05-04

    We have investigated structural and magnetic phase transitions under high pressures in a quaternary rare-earth transition-metal arsenide oxide NdCoAsO compound that is isostructural to the high temperature superconductor parent phase NdFeAsO. The four-probe electrical resistance measurements carried out in a designer diamond anvil cell show that the ferromagnetic Curie temperature and antiferromagnetic Neel temperature increase with an increase in pressure. High pressure x-ray diffraction studies using a synchrotron source show a structural phase transition from a tetragonal phase to a new crystallographic phase at a pressure of 23 GPa at 300 K. The NdCoAsO sample remained antiferromagnetic and non-superconducting down to 10 K and up to the highest pressure achieved in this experiment, 53 GPa. A P-T phase diagram for NdCoAsO is presented from ambient conditions to P = 53 GPa and T = 10 K.

  6. Structural and magnetic phase transitions in NdCoAsO under high pressures

    Energy Technology Data Exchange (ETDEWEB)

    Uhoya, Walter [University of Alabama, Birmingham; Tsoi, Georgiy [University of Alabama, Birmingham; Vohra, Y. K. [University of Alabama, Birmingham; McGuire, Michael A [ORNL; Sefat, A. S. [Oak Ridge National Laboratory (ORNL); Sales, Brian C [ORNL; Mandrus, David [ORNL; Weir, S. T. [Lawrence Livermore National Laboratory (LLNL)

    2010-01-01

    We have investigated structural and magnetic phase transitions under high pressures in a quaternary rare-earth transition-metal arsenide oxide NdCoAsO compound that is isostructural to the high temperature superconductor parent phase NdFeAsO. The four-probe electrical resistance measurements carried out in a designer diamond anvil cell show that the ferromagnetic Curie temperature and antiferromagnetic Neel temperature increase with an increase in pressure. High pressure x-ray diffraction studies using a synchrotron source show a structural phase transition from a tetragonal phase to a new crystallographic phase at a pressure of 23 GPa at 300 K. The NdCoAsO sample remained antiferromagnetic and non-superconducting down to 10 K and up to the highest pressure achieved in this experiment, 53 GPa. A P-T phase diagram for NdCoAsO is presented from ambient conditions to P = 53 GPa and T = 10 K.

  7. High pressure phase determination and electronic properties of lithiumamidoborane

    Science.gov (United States)

    Ramzan, M.; Hussain, T.; Ahuja, R.

    2012-09-01

    In this study we report on the high pressure phase of the promising hydrogen storage material lithiumamidoborane (LiNH2BH3), on the basis of density functional theory calculations with generalized gradient approximation. We take the five possible candidate structures, Pbca, Pbcn, Pcca, Pnma, and Pnnm for the high pressure study of LiNH2BH3. The corresponding structures are relaxed with respect to fractional atomic coordinates and cell parameters, with the use of fully self-consistent ab initio electronic structure calculations to get the equilibrium parameters and total energies. Then we compare the energies of these phases and find that Pbcn is the most favorable phase at ≈100 GPa. Then we calculate the structural parameters of this phase. Finally, we calculate the density of states, Bader charge analysis, and corresponding electron density of this phase.

  8. Phase diagram of Hertzian spheres

    NARCIS (Netherlands)

    Pàmies, J.C.; Cacciuto, A.; Frenkel, D.

    2009-01-01

    We report the phase diagram of interpenetrating Hertzian spheres. The Hertz potential is purely repulsive, bounded at zero separation, and decreases monotonically as a power law with exponent 5/2, vanishing at the overlapping threshold. This simple functional describes the elastic interaction of wea

  9. Mapping the QCD phase diagram

    CERN Document Server

    Rajagopal, K

    1999-01-01

    The QCD vacuum in which we live, which has the familiar hadrons as its excitations, is but one phase of QCD, and far from the simplest one at that. One way to better understand this phase and the nonperturbative dynamics of QCD more generally is to study other phases and the transitions between phases. We are engaged in a voyage of exploration, mapping the QCD phase diagram as a function of temperature T and baryon number chemical potential mu . Because of asymptotic freedom, the high temperature and high baryon density phases of QCD are more simply and more appropriately described in terms of quarks and gluons as degrees of freedom, rather than hadrons. The chiral symmetry breaking condensate which characterizes the vacuum phase melts away. At high densities, quarks form Cooper pairs and new condensates develop. The formation of such superconducting phases requires only weak attractive interactions; these phases may nevertheless break chiral symmetry and have excitations which are indistinguishable from thos...

  10. Synthesis of an orthorhombic high pressure boron phase

    Energy Technology Data Exchange (ETDEWEB)

    Yu Zarechnaya, Evgeniya; Dubrovinsky, Leonid; Miyajima, Nobuyoshi [Bayerisches Geoinstitut, Universitaet Bayreuth, 95440 Bayreuth (Germany); Dubrovinskaia, Natalia [Institute of Earth Sciences, Universitaet Heidelberg, Im Neuenheimer Feld 236, 69120 Heidelberg (Germany); Filinchuk, Yaroslav; Chernyshov, Dmitry; Dmitriev, Vladimir [Swiss Norwegian Beam lines at ESRF, 38043 Gernoble (France)], E-mail: Evgeniya.Zarechnaya@uni-bayreuth.de

    2008-12-15

    The densest boron phase (2.52 g cm{sup -3}) was produced as a result of the synthesis under pressures above 9 GPa and temperatures up to {approx}1800 deg. C. The x-ray powder diffraction pattern and the Raman spectra of the new material do not correspond to those of any known boron phases. A new high-pressure high-temperature boron phase was defined to have an orthorhombic symmetry (Pnnm (No. 58)) and 28 atoms per unit cell.

  11. Synthesis of an orthorhombic high pressure boron phase

    Directory of Open Access Journals (Sweden)

    Evgeniya Yu Zarechnaya, Leonid Dubrovinsky, Natalia Dubrovinskaia, Nobuyoshi Miyajima, Yaroslav Filinchuk, Dmitry Chernyshov and Vladimir Dmitriev

    2008-01-01

    Full Text Available The densest boron phase (2.52 g cm-3 was produced as a result of the synthesis under pressures above 9 GPa and temperatures up to ~1800 °C. The x-ray powder diffraction pattern and the Raman spectra of the new material do not correspond to those of any known boron phases. A new high-pressure high-temperature boron phase was defined to have an orthorhombic symmetry (Pnnm (No. 58 and 28 atoms per unit cell.

  12. High-pressure phase of brucite stable at Earth's mantle transition zone and lower mantle conditions

    Science.gov (United States)

    Hermann, Andreas; Mookherjee, Mainak

    2016-12-01

    We investigate the high-pressure phase diagram of the hydrous mineral brucite, Mg(OH)2, using structure search algorithms and ab initio simulations. We predict a high-pressure phase stable at pressure and temperature conditions found in cold subducting slabs in Earth’s mantle transition zone and lower mantle. This prediction implies that brucite can play a much more important role in water transport and storage in Earth’s interior than hitherto thought. The predicted high-pressure phase, stable in calculations between 20 and 35 GPa and up to 800 K, features MgO6 octahedral units arranged in the anatase–TiO2 structure. Our findings suggest that brucite will transform from a layered to a compact 3D network structure before eventual decomposition into periclase and ice. We show that the high-pressure phase has unique spectroscopic fingerprints that should allow for straightforward detection in experiments. The phase also has distinct elastic properties that might make its direct detection in the deep Earth possible with geophysical methods.

  13. 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.

  14. The Phase Diagram of Superionic Ice

    Science.gov (United States)

    Sun, Jiming; Clark, Bryan; Car, Roberto

    2014-03-01

    Using the variable cell Car-Parrinello molecular dynamics method, we study the phase diagram of superionic ice from 200GPa to 2.5TPa. We present evidence that at very high pressure the FCC structure of the oxygen sublattice may become unstable allowing for a new superionic ice phase, in which the oxygen sublattice takes the P21 structure found in zero-temperature total energy calculations. We also report on how the melting temperature of the hydrogen sublattice is affected by this new crystalline structure of the oxygen sublattice. This work was supported by the NSF under grant DMS-1065894(J.S. and R.C.) and PHY11-25915(B.C.).

  15. A subdivision algorithm for phase equilibrium calculations at high pressures

    Directory of Open Access Journals (Sweden)

    M. L. Corazza

    2007-12-01

    Full Text Available Phase equilibrium calculations at high pressures have been a continuous challenge for scientists and engineers. Traditionally, this task has been performed by solving a system of nonlinear algebraic equations originating from isofugacity equations. The reliability and accuracy of the solutions are strongly dependent on the initial guess, especially due to the fact that the phase equilibrium problems frequently have multiple roots. This work is focused on the application of a subdivision algorithm for thermodynamic calculations at high pressures. The subdivision algorithm consists in the application of successive subdivisions at a given initial interval (rectangle of variables and a systematic test to verify the existence of roots in each subinterval. If the interval checked passes in the test, then it is retained; otherwise it is discharged. The algorithm was applied for vapor-liquid, solid-fluid and solid-vapor-liquid equilibrium as well as for phase stability calculations for binary and multicomponent systems. The results show that the proposed algorithm was capable of finding all roots of all high-pressure thermodynamic problems investigated, independent of the initial guess used.

  16. Phase equilibria in fluid mixtures at high pressures: The He-CH4 system

    Science.gov (United States)

    Streett, W. B.; Erickson, A. L.; Hill, J. L. E.

    1972-01-01

    An experimental study of phase equilibria in the He-CH4 system was carried out over the temperature range 95 to 290 K and at pressures to 10,000 atm. The experimental results consist of equilibrium phase composition for twenty-eight isotherms in the region of coexistence of two fluid phases, together with the pressure-temperature trace of the three-phase boundary at which a CH4-rich solid phase is in equilibrium with the two fluid phases. The system exhibits a fluid-fluid phase separation which persists to temperatures and pressures beyond the range of this experiment. These results, together with those recently obtained for other binary systems, provide information about the form of phase diagrams for binary gas mixtures in the region of pressure induced phase transitions at high pressures. These findings are relevant to problems of deep atmosphere and interior structures in the outer planets.

  17. High Pressure Materials Research: Novel Extended Phases of Molecular Triatomics

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, C

    2004-05-26

    Application of high pressure significantly alters the interatomic distance and thus the nature of intermolecular interaction, chemical bonding, molecular configuration, crystal structure, and stability of solid [1]. With modern advances in high-pressure technologies [2], it is feasible to achieve a large (often up to a several-fold) compression of lattice, at which condition material can be easily forced into a new physical and chemical configuration [3]. The high-pressure thus offers enhanced opportunities to discover new phases, both stable and metastable ones, and to tune exotic properties in a wide-range of atomistic length scale, substantially greater than (often being several orders of) those achieved by other thermal (varying temperatures) and chemical (varying composition or making alloys) means. Simple molecular solids like H{sub 2}, C, CO{sub 2}, N{sub 2}, O{sub 2}, H{sub 2}O, CO, NH{sub 3}, and CH{sub 4} are bounded by strong covalent intramolecular bonds, yet relatively weak intermolecular bonds of van der Waals and/or hydrogen bonds. The weak intermolecular bonds make these solids highly compressible (i.e., low bulk moduli typically less than 10 GPa), while the strong covalent bonds make them chemically inert at least initially at low pressures. Carbon-carbon single bonds, carbon-oxygen double bonds and nitrogen-nitrogen triple bonds, for example, are among the strongest. These molecular forms are, thus, often considered to remain stable in an extended region of high pressures and high temperatures. High stabilities of these covalent molecules are also the basis of which their mixtures are often presumed to be the major detonation products of energetic materials as well as the major constituents of giant planets. However, their physical/chemical stabilities are not truly understood at those extreme pressure-temperature conditions. In fact, an increasing amount of experimental evidences contradict the assumed stability of these materials at high

  18. Origin and use of crystallization phase diagrams.

    Science.gov (United States)

    Rupp, Bernhard

    2015-03-01

    Crystallization phase diagrams are frequently used to conceptualize the phase relations and also the processes taking place during the crystallization of macromolecules. While a great deal of freedom is given in crystallization phase diagrams owing to a lack of specific knowledge about the actual phase boundaries and phase equilibria, crucial fundamental features of phase diagrams can be derived from thermodynamic first principles. Consequently, there are limits to what can be reasonably displayed in a phase diagram, and imagination may start to conflict with thermodynamic realities. Here, the commonly used `crystallization phase diagrams' are derived from thermodynamic excess properties and their limitations and appropriate use is discussed.

  19. Phase diagram of crushed powders

    Science.gov (United States)

    Bodard, Sébastien; Jalbaud, Olivier; Saurel, Richard; Burtschell, Yves; Lapebie, Emmanuel

    2016-12-01

    Compression of monodisperse powder samples in quasistatic conditions is addressed in a pressure range such that particles fragmentation occurs while the solid remains incompressible (typical pressure range of 1-300 MPa for glass powders). For a granular bed made of particles of given size, the existence of three stages is observed during compression and crush up. First, classical compression occurs and the pressure of the granular bed increases along a characteristic curve as the volume decreases. Then, a critical pressure is reached for which fragmentation begins. During the fragmentation process, the granular pressure stays constant in a given volume range. At the end of this second stage, 20%-50% of initial grains are reduced to finer particles, depending on the initial size. Then the compression undergoes the third stage and the pressure increases along another characteristic curve, in the absence of extra fragmentation. The present paper analyses the analogies between the phase transition in liquid-vapour systems and powder compression with crush-up. Fragmentation diagram for a soda lime glass is determined by experimental means. The analogues of the saturation pressure and latent heat of phase change are determined. Two thermodynamic models are then examined to represent the crush-up diagram. The first one uses piecewise functions while the second one is of van der Waals type. Both equations of state relate granular pressure, solid volume fraction, and initial particle diameter. The piecewise functions approach provides reasonable representations of the phase diagram while the van der Waals one fails.

  20. Superhard Semiconducting Optically Transparent High Pressure Phase of Boron

    Science.gov (United States)

    Zarechnaya, E. Yu.; Dubrovinsky, L.; Dubrovinskaia, N.; Filinchuk, Y.; Chernyshov, D.; Dmitriev, V.; Miyajima, N.; El Goresy, A.; Braun, H. F.; van Smaalen, S.; Kantor, I.; Kantor, A.; Prakapenka, V.; Hanfland, M.; Mikhaylushkin, A. S.; Abrikosov, I. A.; Simak, S. I.

    2009-05-01

    An orthorhombic (space group Pnnm) boron phase was synthesized at pressures above 9 GPa and high temperature, and it was demonstrated to be stable at least up to 30 GPa. The structure, determined by single-crystal x-ray diffraction, consists of B12 icosahedra and B2 dumbbells. The charge density distribution obtained from experimental data and ab initio calculations suggests covalent chemical bonding in this phase. Strong covalent interatomic interactions explain the low compressibility value (bulk modulus is K300=227GPa) and high hardness of high-pressure boron (Vickers hardness HV=58GPa), after diamond the second hardest elemental material.

  1. Phase Diagrams of Nuclear Pasta

    Science.gov (United States)

    Caplan, Matthew; Horowitz, Chuck; Berry, Don; da Silva Schneider, Andre

    2016-03-01

    In the inner crust of neutrons stars, where matter is near the saturation density, protons and neutrons arrange themselves into complex structures called nuclear pasta. Early theoretical work predicted a simple graduated hierarchy of pasta phases, consisting of spheres, cylinders, slabs, and uniform matter with voids. Previous work has simulated these phases with a simple classical model and has shown that the formation of these structures is dependent on the temperature, density, and proton fraction. However, previous work only studied a limited range of these parameters due to computational limitations. Thanks to recent advances in computing it is now possible to survey the structure of nuclear pasta for a larger range of parameters. By simulating nuclear pasta with constant temperature and proton fraction in an expanding simulation volume we are able to study the phase transitions in nuclear pasta, and thus produce a set of phase diagrams. We report on these phase diagrams as well as newly identified phases of nuclear pasta and discuss their implications for neutron star observables.

  2. Elastic phase transitions in metals at high pressures.

    Science.gov (United States)

    Krasilnikov, O M; Vekilov, Yu Kh; Mosyagin, I Yu; Isaev, E I; Bondarenko, N G

    2012-04-19

    The elastic phase transitions of cubic metals at high pressures are investigated within the framework of Landau theory. It is shown that at pressures comparable with the magnitude of the bulk modulus the phase transition is connected with the loss of stability relative to uniform deformation of the crystalline lattice. Discontinuity of the order parameter at the transition point and its equilibrium value are expressed through the second- to fourth-order elastic constants. The second-,third- and fourth-order elastic constants and phonon dispersion curves of vanadium under hydrostatic pressure are obtained by first-principles calculations. Structural transformation in vanadium under pressure is studied using the obtained results. It is shown that the experimentally observed at P ≈ 69 GPa phase transition in vanadium is the first-order phase transition close to a second-order phase transition.

  3. Phase Stability of Epsilon and Gamma Hniw (CL-20) at High-Pressure and Temperature

    Science.gov (United States)

    Gump, Jared C.; Stoltz, Chad A.; Peiris, Suhithi M.

    2007-12-01

    Hexanitrohexaazaisowurtzitane (CL-20) is one of the few ingredients developed since World War II to be considered for transition to military use. Five polymorphs have been identified for CL-20 by FTIR measurements (α, β, γ, ɛ, ζ). As CL-20 is transitioned into munitions it will become necessary to predict its response under conditions of detonation, for performance evaluation. Such predictive modeling requires a phase diagram and basic thermodynamic properties of the various phases at high pressure and temperature. Therefore, the epsilon and gamma phases of CL-20 at static high-pressure and temperature were investigated using synchrotron angle-dispersive x-ray diffraction experiments. The samples were compressed and heated using diamond anvil cells (DAC). Pressures and temperatures achieved were around 5 GPa and 240 °C, respectively. The epsilon phase was stable to 6.3 GPa at ambient temperature. When heated at ambient pressure the epsilon phase was sustained to a temperature of 120 °C then underwent a transition to the gamma phase above 125 °C and then thermal decomposition occurred above 150 °C. Upon compression, the gamma phase underwent a phase transition at both ambient temperature and 140 °C. Pressure—volume data for the epsilon and gamma phase at ambient temperature and the epsilon phase at 75 °C were fit to the Birch-Murnaghan formalism to obtain isothermal equations of state.

  4. Phase Transition and Structure of Silver Azide at High Pressure

    Energy Technology Data Exchange (ETDEWEB)

    D Hou; F Zhang; C Ji; T Hannon; H Zhu; J Wu; V Levitas; Y Ma

    2011-12-31

    Silver azide (AgN{sub 3}) was compressed up to 51.3 GPa. The results reveal a reversible second-order orthorhombic-to-tetragonal phase transformation starting from ambient pressure and completing at 2.7 GPa. The phase transition is accompanied by a proximity of cell parameters a and b, a 3{sup o} rotation of azide anions, and a change of coordination number from 4-4 (four short, four long) to eight fold. The crystal structure of the high pressure phase is determined to be in I4/mcm space group, with Ag at 4a, N{sub 1} at 4d, and N{sub 2} at 8h Wyckoff positions. Both of the two phases have anisotropic compressibility: the orthorhombic phase exhibits an anomalous expansion under compression along a-axis and is more compressive along b-axis than c-axis; the tetragonal phase is more compressive along the interlayer direction than the intralayer directions. The bulk moduli of the orthorhombic and tetragonal phases are determined to be K{sub OT} = 39{+-}5 GPa with K{sub OT'} = 10{+-}7 and K{sub OT} = 57 {+-}2 GPa with K{sub OT'} = 6.6{+-}0.2, respectively.

  5. Superhard Semiconducting Optically Transparent High Pressure Phase of Boron

    Energy Technology Data Exchange (ETDEWEB)

    Zarechnaya, E.Yu.; Dubrovinsky, L.; Dubrovinskaia, N.; Filinchuk, Y.; Chernyshov, D.; Dmitriev, V.; Miyajima, N.; Goresy, A. El; Braun, H.F.; Van Smaalen, S.; Kantor, I.; Kantor, A.; Prakapenka, V.; Hanfland, M.; Mikhaylushkin, A.S.; Abrikosov, I.A.; Simak, S.I.; (Link); (Heidelberg); (Bayreuth); (ESRF); (UC)

    2009-05-21

    An orthorhombic (space group Pnnm) boron phase was synthesized at pressures above 9 GPa and high temperature, and it was demonstrated to be stable at least up to 30 GPa. The structure, determined by single-crystal x-ray diffraction, consists of B{sub 12} icosahedra and B{sub 2} dumbbells. The charge density distribution obtained from experimental data and ab initio calculations suggests covalent chemical bonding in this phase. Strong covalent interatomic interactions explain the low compressibility value (bulk modulus is K{sub 300} = 227 GPa) and high hardness of high-pressure boron (Vickers hardness H{sub v} = 58 GPa), after diamond the second hardest elemental material.

  6. 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

  7. On the high-pressure phase stability and elastic properties of β-titanium alloys

    Science.gov (United States)

    Smith, D.; Joris, O. P. J.; Sankaran, A.; Weekes, H. E.; Bull, D. J.; Prior, T. J.; Dye, D.; Errandonea, D.; Proctor, J. E.

    2017-04-01

    We have studied the compressibility and stability of different β-titanium alloys at high pressure, including binary Ti-Mo, Ti-24Nb-4Zr-8Sn (Ti2448) and Ti-36Nb-2Ta-0.3O (gum metal). We observed stability of the β phase in these alloys to 40 GPa, well into the ω phase region in the P-T diagram of pure titanium. Gum metal was pressurised above 70 GPa and forms a phase with a crystal structure similar to the η phase of pure Ti. The bulk moduli determined for the different alloys range from 97  ±  3 GPa (Ti2448) to 124  ±  6 GPa (Ti-16.8Mo-0.13O).

  8. High pressure antiferrodistortive phase transition in mixed crystals of EuTiO3 and SrTiO3

    Directory of Open Access Journals (Sweden)

    Paraskevas Parisiades

    2016-06-01

    Full Text Available We report a detailed high pressure study on Eu1−xSrxTiO3 polycrystalline samples using synchrotron x-ray diffraction. We have observed a second-order antiferrodistortive phase transition for all doping levels which corresponds to the transition that has been previously explored as a function of temperature. The analysis of the compression mechanism by calculating the lattice parameters, spontaneous strains and tilt angles of the TiO6 octahedra leads to a high pressure phase diagram for Eu1−xSrxTiO3.

  9. High pressure antiferrodistortive phase transition in mixed crystals of EuTiO3 and SrTiO3

    Science.gov (United States)

    Parisiades, Paraskevas; Saltarelli, Francesco; Liarokapis, Efthymios; Köhler, Jürgen; Bussmann-Holder, Annette

    2016-06-01

    We report a detailed high pressure study on Eu1-xSrxTiO3 polycrystalline samples using synchrotron x-ray diffraction. We have observed a second-order antiferrodistortive phase transition for all doping levels which corresponds to the transition that has been previously explored as a function of temperature. The analysis of the compression mechanism by calculating the lattice parameters, spontaneous strains and tilt angles of the TiO6 octahedra leads to a high pressure phase diagram for Eu1-xSrxTiO3.

  10. Stereo 3D spatial phase diagrams

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Jinwu, E-mail: kangjw@tsinghua.edu.cn; Liu, Baicheng, E-mail: liubc@tsinghua.edu.cn

    2016-07-15

    Phase diagrams serve as the fundamental guidance in materials science and engineering. Binary P-T-X (pressure–temperature–composition) and multi-component phase diagrams are of complex spatial geometry, which brings difficulty for understanding. The authors constructed 3D stereo binary P-T-X, typical ternary and some quaternary phase diagrams. A phase diagram construction algorithm based on the calculated phase reaction data in PandaT was developed. And the 3D stereo phase diagram of Al-Cu-Mg ternary system is presented. These phase diagrams can be illustrated by wireframe, surface, solid or their mixture, isotherms and isopleths can be generated. All of these can be displayed by the three typical display ways: electronic shutter, polarization and anaglyph (for example red-cyan glasses). Especially, they can be printed out with 3D stereo effect on paper, and watched by the aid of anaglyph glasses, which makes 3D stereo book of phase diagrams come to reality. Compared with the traditional illustration way, the front of phase diagrams protrude from the screen and the back stretches far behind of the screen under 3D stereo display, the spatial structure can be clearly and immediately perceived. These 3D stereo phase diagrams are useful in teaching and research. - Highlights: • Stereo 3D phase diagram database was constructed, including binary P-T-X, ternary, some quaternary and real ternary systems. • The phase diagrams can be watched by active shutter or polarized or anaglyph glasses. • The print phase diagrams retains 3D stereo effect which can be achieved by the aid of anaglyph glasses.

  11. Phase diagram of elastic spheres.

    Science.gov (United States)

    Athanasopoulou, L; Ziherl, P

    2017-02-15

    Experiments show that polymeric nanoparticles often self-assemble into several non-close-packed lattices in addition to the face-centered cubic lattice. Here, we explore theoretically the possibility that the observed phase sequences may be associated with the softness of the particles, which are modeled as elastic spheres interacting upon contact. The spheres are described by two finite-deformation theories of elasticity, the modified Saint-Venant-Kirchhoff model and the neo-Hookean model. We determine the range of indentations where the repulsion between the spheres is pairwise additive and agrees with the Hertz theory. By computing the elastic energies of nine trial crystal lattices at densities far beyond the Hertzian range, we construct the phase diagram and find the face- and body-centered cubic lattices as well as the A15 lattice and the simple hexagonal lattice, with the last two being stable at large densities where the spheres are completely faceted. These results are qualitatively consistent with observations, suggesting that deformability may indeed be viewed as a generic property that determines the phase behavior in nanocolloidal suspensions.

  12. Phase relations in the Fe-FeSi system at high pressures and temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, Rebecca A.; Campbell, Andrew J.; Reaman, Daniel M.; Miller, Noah A.; Heinz, Dion L.; Dera, Przymyslaw; Prakapenka, Vitali B. (UC); (Maryland)

    2016-07-29

    The Earth's core is comprised mostly of iron and nickel, but it also contains several weight percent of one or more unknown light elements, which may include silicon. Therefore it is important to understand the high pressure, high temperature properties and behavior of alloys in the Fe–FeSi system, such as their phase diagrams. We determined melting temperatures and subsolidus phase relations of Fe–9 wt% Si and stoichiometric FeSi using synchrotron X-ray diffraction at high pressures and temperatures, up to ~200 GPa and ~145 GPa, respectively. Combining this data with that of previous studies, we generated phase diagrams in pressure–temperature, temperature–composition, and pressure–composition space. We find the B2 crystal structure in Fe–9Si where previous studies reported the less ordered bcc structure, and a shallower slope for the hcp+B2 to fcc+B2 boundary than previously reported. In stoichiometric FeSi, we report a wide B2+B20 two-phase field, with complete conversion to the B2 structure at ~42 GPa. The minimum temperature of an Fe–Si outer core is 4380 K, based on the eutectic melting point of Fe–9Si, and silicon is shown to be less efficient at depressing the melting point of iron at core conditions than oxygen or sulfur. At the highest pressures reached, only the hcp and B2 structures are seen in the Fe–FeSi system. We predict that alloys containing more than ~4–8 wt% silicon will convert to an hcp+B2 mixture and later to the hcp structure with increasing pressure, and that an iron–silicon alloy in the Earth's inner core would most likely be a mixture of hcp and B2 phases.

  13. Dense superconducting phases of copper-bismuth at high pressure

    Science.gov (United States)

    Amsler, Maximilian; Wolverton, Chris

    2017-08-01

    Although copper and bismuth do not form any compounds at ambient conditions, two intermetallics, CuBi and Cu11Bi7 , were recently synthesized at high pressures. Here we report on the discovery of additional copper-bismuth phases at elevated pressures with high densities from ab initio calculations. In particular, a Cu2Bi compound is found to be thermodynamically stable at pressures above 59 GPa, crystallizing in the cubic Laves structure. In strong contrast to Cu11Bi7 and CuBi, cubic Cu2Bi does not exhibit any voids or channels. Since the bismuth lone pairs in cubic Cu2Bi are stereochemically inactive, the constituent elements can be closely packed and a high density of 10.52 g/cm3 at 0 GPa is achieved. The moderate electron-phonon coupling of λ =0.68 leads to a superconducting temperature of 2 K, which exceeds the values observed both in Cu11Bi7 and CuBi, as well as in elemental Cu and Bi.

  14. Ferroelectric phase diagram of PVDF:PMMA

    NARCIS (Netherlands)

    Li, M.; Stingelin, N.; Michels, J.J.; Spijkman, M.-J.; Asadi, K.; Feldman, K.; Blom, P.W.M.; Leeuw, D.M. de

    2012-01-01

    We have investigated the ferroelectric phase diagram of poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA). The binary nonequilibrium temperature composition diagram was determined and melting of α- and β-phase PVDF was identified. Ferroelectric β-PVDF:PMMA blend films were made b

  15. Ferroelectric Phase Diagram of PVDF : PMMA

    NARCIS (Netherlands)

    Li, Mengyuan; Stingelin, Natalie; Michels, Jasper J.; Spijkman, Mark-Jan; Asadi, Kamal; Feldman, Kirill; Blom, Paul W. M.; de Leeuw, Dago M.

    2012-01-01

    We have investigated the ferroelectric phase diagram of poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA). The binary nonequilibrium temperature composition diagram was determined and melting of alpha- and beta-phase PVDF was identified. Ferroelectric beta-PVDF:PMMA blend films w

  16. High-pressure sapphire cell for phase equilibria measurements of CO2/organic/water systems.

    Science.gov (United States)

    Pollet, Pamela; Ethier, Amy L; Senter, James C; Eckert, Charles A; Liotta, Charles L

    2014-01-24

    The high pressure sapphire cell apparatus was constructed to visually determine the composition of multiphase systems without physical sampling. Specifically, the sapphire cell enables visual data collection from multiple loadings to solve a set of material balances to precisely determine phase composition. Ternary phase diagrams can then be established to determine the proportion of each component in each phase at a given condition. In principle, any ternary system can be studied although ternary systems (gas-liquid-liquid) are the specific examples discussed herein. For instance, the ternary THF-Water-CO2 system was studied at 25 and 40 °C and is described herein. Of key importance, this technique does not require sampling. Circumventing the possible disturbance of the system equilibrium upon sampling, inherent measurement errors, and technical difficulties of physically sampling under pressure is a significant benefit of this technique. Perhaps as important, the sapphire cell also enables the direct visual observation of the phase behavior. In fact, as the CO2 pressure is increased, the homogeneous THF-Water solution phase splits at about 2 MPa. With this technique, it was possible to easily and clearly observe the cloud point and determine the composition of the newly formed phases as a function of pressure. The data acquired with the sapphire cell technique can be used for many applications. In our case, we measured swelling and composition for tunable solvents, like gas-expanded liquids, gas-expanded ionic liquids and Organic Aqueous Tunable Systems (OATS)(1-4). For the latest system, OATS, the high-pressure sapphire cell enabled the study of (1) phase behavior as a function of pressure and temperature, (2) composition of each phase (gas-liquid-liquid) as a function of pressure and temperature and (3) catalyst partitioning in the two liquid phases as a function of pressure and composition. Finally, the sapphire cell is an especially effective tool to gather

  17. QCD Phase Diagram with Imaginary Chemical Potential

    Directory of Open Access Journals (Sweden)

    Nakamura Atsushi

    2012-02-01

    Full Text Available We report our recent results on the QCD phase diagram obtained from the lattice QCD simulation. The location of the phase boundary between hadronic and QGP phases in the two-flavor QCD phase diagram is investigated. The imaginary chemical potential approach is employed, which is based on Monte Carlo simulations of the QCD with imaginary chemical potential and analytic continuation to the real chemical potential region.

  18. Phase diagram to design passive nanostructures

    CERN Document Server

    Lee, Jeng Yi

    2015-01-01

    A phase diagram, defined by the amplitude square and phase of scattering coefficients for absorption cross-section in each individual channel, is introduced as a universal map on the electromagnetic properties for passive scatterers. General physical bounds are naturally revealed based on the intrinsic power conservation in a passive scattering system, entailing power competitions among scattering, absorption, and extinction. Exotic scattering and absorption phenomena, from resonant scattering, invisible cloaking, coherent perfect absorber, and subwavelength superscattering can all be illustrated in this phase diagram. With electrically small core-shell scatterers as an example, we demonstrate a systematic method to design field-controllable structures based on the allowed trajectories in the phase diagram. The proposed phase diagram not only provides a simple tool to design optical devices but also promotes a deep understanding on Mie's scattering theory.

  19. High pressure phase transition and variation of elastic constants of diluted magnetic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Varshney, Dinesh; Sharma, P.; Kaurav, N. [School of Physics, Vigyan Bhawan, Devi Ahilya University, Takshila Campus, Indore 452017 (India); Shah, S. [Department of Physics, P. M. B. Gujarati Science College, Indore-452001 (India); Singh, R.K. [M. P. Bhoj (Open) University, Shivaji Nagar, Bhopal-462016 (India)

    2004-11-01

    A theoretical study of the high-pressure phase transition and elastic behavior in diluted magnetic semiconductors Zn{sub 0.83}Mn{sub 0.17}Se, using a three-body interaction (TBI) potential caused by the electron-shell deformation of the overlapping ions is carried out. The estimated values of phase transition pressure and the vast volume discontinuity in pressure-volume (PV) phase diagram indicate the structural phase transition from zincblende (B3) to rock salt (B1). The variation of second-order elastic constants with pressure resembles that observed in some binary semiconductors. The inconsistency in the deduced value of pressure derivative of second order elastic constant with the available data is attributed to the fact that we derive expressions neglecting thermal effects and assuming the overlap repulsion significant only up to nearest neighbors. The vdW interaction is effective in obtaining the thermodynamical parameters such as Debye temperature, Gruneisen parameter, thermal expansion coefficient, compressibility as well phase stability in diluted magnetic semiconductors. It is revealed that TBI model has a promise to predict the phase transition pressure and the pressure variation of elastic constants of other semiconductors as well. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Phase transformations of amorphous semiconductor alloys under high pressures

    CERN Document Server

    Antonov, V E; Fedotov, V K; Harkunov, A I; Ponyatovsky, E G

    2002-01-01

    The paper reviews the results of experimental studies and thermodynamical modelling of metastable T-P diagrams of initially amorphous GaSb-Ge and Zn-Sb alloys which provide a new insight into the problem of pressure-induced amorphization.

  1. New high-pressure phases of MoSe2 and MoTe2

    Science.gov (United States)

    Kohulák, Oto; MartoÅák, Roman

    2017-02-01

    Three Mo-based transition-metal dichalcogenides MoS2,MoSe2, and MoTe2 share at ambient conditions the same structure 2 Hc , consisting of layers where Mo atoms are surrounded by six chalcogen atoms in trigonal prism coordination. The knowledge of their high-pressure behavior is, however, limited, particularly in case of MoSe2 and MoTe2. The latter materials do not undergo a layer-sliding transition 2 Hc→ 2 Ha known in MoS2 and currently no other stable phase aside from 2 Hc is known in these systems at room temperature. Employing evolutionary crystal structure prediction in combination with ab initio calculations, we study the zero-temperature phase diagram of both materials up to Mbar pressures. We find a tetragonal phase with space group P4/mmm, previously predicted in MoS2, to become stable in MoSe2 at 118 GPa. In MoTe2, we predict at 50 GPa a transition to a new layered tetragonal structure with space group I4/mmm, similar to CaC2, where Mo atoms are surrounded by eight Te atoms. The phase is metallic already at the transition pressure and becomes a good metal beyond 1 Mbar. We discuss chemical trends in the family of Mo-based transition-metal dichalcogenides and suggest that MoTe2 likely offers the easiest route towards the post-2 H phases.

  2. From ergodicity to extended phase diagrams.

    Science.gov (United States)

    Woodley, Scott M; Sokol, Alexey A

    2012-04-16

    Structure prediction of stable and metastable phases is put on equal footing for the first time, with a solid thermodynamical background. How to estimate the lifetime of metastable phases is demonstrated by recent groundbreaking work of Jansen, Pentin, and Schön. At the heart lies the exploration of the Gibbs free-energy landscapes and the extended phase diagrams for complex systems.

  3. Phase diagrams modified by interfacial penalties

    Directory of Open Access Journals (Sweden)

    Atanacković T.M.

    2007-01-01

    Full Text Available The conventional forms of phase diagrams are constructed without consideration of interfacial energies and they represent an impor­tant tool for chemical engineers and metallurgists. If interfacial energies are taken into consideration, it is intuitively obvious that the regions of phase equilibria must become smaller, because there is a penalty on the formation of interfaces. We investigate this phe­nomenon qualitatively for a one-dimensional model, in which the phases occur as layers rather than droplets or bubbles. The modified phase diagrams are shown in Chapters 3 and 4.

  4. Phase diagram of a truncated tetrahedral model

    Science.gov (United States)

    Krcmar, Roman; Gendiar, Andrej; Nishino, Tomotoshi

    2016-08-01

    Phase diagram of a discrete counterpart of the classical Heisenberg model, the truncated tetrahedral model, is analyzed on the square lattice, when the interaction is ferromagnetic. Each spin is represented by a unit vector that can point to one of the 12 vertices of the truncated tetrahedron, which is a continuous interpolation between the tetrahedron and the octahedron. Phase diagram of the model is determined by means of the statistical analog of the entanglement entropy, which is numerically calculated by the corner transfer matrix renormalization group method. The obtained phase diagram consists of four different phases, which are separated by five transition lines. In the parameter region, where the octahedral anisotropy is dominant, a weak first-order phase transition is observed.

  5. The high-pressure phase of CePtAl

    Energy Technology Data Exchange (ETDEWEB)

    Heymann, Gunter [Univ. Innsbruck (Austria). Inst. fuer Allgemeine, Anorganische und Theoretische Chemie; Heying, Birgit; Rodewald, Ute C. [Univ. Muenster (Germany). Inst. fuer Anorganische und Analytische Chemie; Janka, Oliver [Univ. Muenster (Germany). Inst. fuer Anorganische und Analytische Chemie; Univ. Oldenburg (Germany). Inst. fuer Chemie

    2017-03-01

    The intermetallic aluminum compound HP-CePtAl was synthesized by arc melting of the elements with subsequent high-pressure/high-temperature treatment at 1620 K and 10.5 GPa in a multianvil press. The compound crystallizes in the hexagonal MgZn{sub 2}-type structure (P6{sub 3}/mmc) with lattice parameters of a=552.7(1) and c=898.8(2) pm refined from powder X-ray diffraction data. With the help of single crystal investigations (wR=0.0527, 187 F{sup 2} values, 13 variables), the proposed structure type was confirmed and the mixed Pt/Al site occupations could be refined. Magnetic susceptibility measurements showed a disappearance of the complex magnetic ordering phenomena, which are observed in NP-CePtAl.

  6. PHASE DIAGRAMS OF SODIUM SULFATE AND SODIUM CHROMATE TO 45 KBAR.

    Science.gov (United States)

    The phase diagrams of NaSO4 and Na2CrO4 were determined to 45 kbar. Two new high-pressure phases were found for Na2SO4. Eight different solid... phase diagrams of Na2SO4 and Na2CrO4 are strikingly similar, and there are reasons for believing that every known polymorph of Na2CrO4 has an isostructural counterpart in the phase diagram of Na2SO4. (Author)

  7. Modeling the phase diagram of carbon

    NARCIS (Netherlands)

    Ghiringhelli, L.M.; Los, J.H.; Meijer, E.J.; Fasolino, A.; Frenkel, D.

    2005-01-01

    We determined the phase diagram involving diamond, graphite, and liquid carbon using a recently developed semiempirical potential. Using accurate free-energy calculations, we computed the solid-solid and solid-liquid phase boundaries for pressures and temperatures up to 400 GPa and 12 000 K, respect

  8. Phase diagram distortion from traffic parameter averaging.

    NARCIS (Netherlands)

    Stipdonk, H. Toorenburg, J. van & Postema, M.

    2010-01-01

    Motorway traffic congestion is a major bottleneck for economic growth. Therefore, research of traffic behaviour is carried out in many countries. Although well describing the undersaturated free flow phase as an almost straight line in a (k,q)-phase diagram, congested traffic observations and

  9. Phase diagram distortion from traffic parameter averaging.

    NARCIS (Netherlands)

    Stipdonk, H. Toorenburg, J. van & Postema, M.

    2010-01-01

    Motorway traffic congestion is a major bottleneck for economic growth. Therefore, research of traffic behaviour is carried out in many countries. Although well describing the undersaturated free flow phase as an almost straight line in a (k,q)-phase diagram, congested traffic observations and theori

  10. Phase diagram of the B-B2O3 system at pressures to 24 GPa

    OpenAIRE

    Turkevich, Vladimir Z.; Turkevich, Dmitry V.; Solozhenko, Vladimir L.

    2016-01-01

    The evolution of topology of the B-B2O3 phase diagram has been studied at pressures up to 24 GPa using models of phenomenological thermodynamics with interaction parameters derived from experimental data on phase equilibria at high pressures and high temperatures.

  11. Phase diagrams of diluted transverse Ising nanowire

    Energy Technology Data Exchange (ETDEWEB)

    Bouhou, S.; Essaoudi, I. [Laboratoire de Physique des Matériaux et Modélisation, des Systèmes, (LP2MS), Unité Associée au CNRST-URAC 08, University of Moulay Ismail, Physics Department, Faculty of Sciences, B.P. 11201 Meknes (Morocco); Ainane, A., E-mail: ainane@pks.mpg.de [Laboratoire de Physique des Matériaux et Modélisation, des Systèmes, (LP2MS), Unité Associée au CNRST-URAC 08, University of Moulay Ismail, Physics Department, Faculty of Sciences, B.P. 11201 Meknes (Morocco); Max-Planck-Institut für Physik Complexer Systeme, Nöthnitzer Str. 38 D-01187 Dresden (Germany); Saber, M. [Laboratoire de Physique des Matériaux et Modélisation, des Systèmes, (LP2MS), Unité Associée au CNRST-URAC 08, University of Moulay Ismail, Physics Department, Faculty of Sciences, B.P. 11201 Meknes (Morocco); Max-Planck-Institut für Physik Complexer Systeme, Nöthnitzer Str. 38 D-01187 Dresden (Germany); Ahuja, R. [Condensed Matter Theory Group, Department of Physics and Astronomy, Uppsala University, 75120 Uppsala (Sweden); Dujardin, F. [Laboratoire de Chimie et Physique des Milieux Complexes (LCPMC), Institut de Chimie, Physique et Matériaux (ICPM), 1 Bd. Arago, 57070 Metz (France)

    2013-06-15

    In this paper, the phase diagrams of diluted Ising nanowire consisting of core and surface shell coupling by J{sub cs} exchange interaction are studied using the effective field theory with a probability distribution technique, in the presence of transverse fields in the core and in the surface shell. We find a number of characteristic phenomena. In particular, the effect of concentration c of magnetic atoms, the exchange interaction core/shell, the exchange in surface and the transverse fields in core and in surface shell of phase diagrams are investigated. - Highlights: ► We use the EFT to investigate the phase diagrams of Ising transverse nanowire. ► Ferrimagnetic and ferromagnetic cases are investigated. ► The effects of the dilution and the transverse fields in core and shell are studied. ► Behavior of the transition temperature with the exchange interaction is given.

  12. Shock dynamics of phase diagrams

    CERN Document Server

    Moro, Antonio

    2014-01-01

    A thermodynamic phase transition denotes a drastic change of state of a physical system due to a continuous change of thermodynamic variables, as for instance pressure and temperature. The classical van der Waals equation of state is the simplest model that predicts the occurrence of a critical point associated with the gas-liquid phase transition. Nevertheless, below the critical temperature, theoretical predictions of the van der Waals theory significantly depart from the observed physical behaviour. We develop a novel approach to classical thermodynamics based on the solution of Maxwell relations for a generalised family of nonlocal entropy functions. This theory provides an exact mathematical description of discontinuities of the order parameter within the phase transition region, it explains the universal form of the equations of state and the occurrence of triple points in terms of the dynamics of nonlinear shock wave fronts.

  13. Phase diagram of a single lane roundabout

    Science.gov (United States)

    Echab, H.; Lakouari, N.; Ez-Zahraouy, H.; Benyoussef, A.

    2016-03-01

    Using the cellular automata model, we numerically study the traffic dynamic in a single lane roundabout system of four entry/exit points. The boundaries are controlled by the injecting rates α1, α2 and the extracting rate β. Both the system with and without Splitter Islands of width Lsp are considered. The phase diagram in the (α1 , β) space and its variation with the roundabout size, Pagg (i.e. the probability of aggressive entry), and Pexit (i.e. the probability of preferential exit) are constructed. The results show that the phase diagram in both cases consists of three phases: free flow, congested and jammed. However, as Lsp increases the free flow phase enlarges while the congested and jammed ones shrink. On the other hand, the short sized roundabout shows better performance in the free flow phase while the large one is more optimal in the congested phase. The density profiles are also investigated.

  14. Phase transition of solid bismuth under high pressure

    Science.gov (United States)

    Chen, Hai-Yan; Xiang, Shi-Kai; Yan, Xiao-Zhen; Zheng, Li-Rong; Zhang, Yi; Liu, Sheng-Gang; Bi, Yan

    2016-10-01

    As a widely used pressure calibrator, the structural phase transitions of bismuth from phase I, to phase II, to phase III, and then to phase V with increasing pressure at 300 K have been widely confirmed. However, there are different structural versions for phase III, most of which are determined by x-ray diffraction (XRD) technology. Using x-ray absorption fine structure (XAFS) measurements combined with ab initio calculations, we show that the proposed incommensurate composite structure of bismuth of the three configurations is the best option. An abnormal continuous increase of the nearest-neighbor distance of phase III with elevated pressure is also observed. The electronic structure transformation from semimetal to metal is responsible for the complex behavior of structure transformation. Project supported by the National Natural Science Foundation of China (Grant Nos. 10904133, 11304294, 11274281, 11404006, and U1230201), the Development Foundation of China Academy of Engineering Physics (Grant Nos. 2015B0101004, 2013B0401062, and 2012A0101001), the Research Foundation of the Laboratory of Shock Wave and Detonation, China (Grant No. 9140C670201140C67282).

  15. 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...

  16. High pressure phase transitions for CdSe

    Indian Academy of Sciences (India)

    Bo Kong; Ti-Xian Zeng; Zhu-Wen Zhou; De-Liang Chen; Xiao-Wei Sun

    2014-05-01

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

  17. Magnetic phase diagram of Ho-Ag

    Energy Technology Data Exchange (ETDEWEB)

    Paul-Boncour, V [Chimie Metallurgique des Terres Rares, ICMPE, CNRS, 2 rue H Dunant, 94320 Thiais (France); Hoser, A; Stuesser, N [Hahn-Meitner Institut, Glienicker Strasse 100, 14109, Berlin (Germany); Hense, K; Gratz, E [Institute for Experimental Physics, Technical University Vienna, Wiedner Hauptstrasse 8-10, A-1040 (Austria); Rotter, M [Institut fuer Physikalische Chemie, Universitaet Wien, Waehringerstrasse 42, 1090 Wien (Austria)], E-mail: paulbon@glvt-cnrs.fr

    2008-03-12

    The magnetic phase diagram of Ho-Ag has been established using magnetoresistance, magnetostriction and neutron diffraction experiments versus applied field and temperature. Three different magnetic phases were observed: an incommensurate antiferromagnetic phase (IC) below T{sub N} = 33 K, a commensurate antiferromagnetic phase (C) above 5 T and below T{sub 1} (5-8 K) and a ferromagnetic component above 3 T. The IC phase undergoes spin reorientations around 5 T (IC') and 13 T (IC'')

  18. Phase Diagram in Quantum Chromodynamics

    CERN Document Server

    Apostol, M

    2013-01-01

    It is suggested that the hadronization of the quark-gluon plasma is a first-order phase transition described by a critical curve in the temperature-(quark) density plane which terminates in a critical point. Such a critical curve is derived from the van der Waals equation and its parameters are estimated by using the theoretical approach given in M. Apostol, Roum. Reps. Phys. 59 249 (2007); Mod. Phys. Lett. B21 893 (2007). The main assumption is that quark-gluon plasma created by high-energy nucleus-nucleus collisions is a gas of ultrarelativistic quarks in equilibrium with gluons (vanishing chemical potential, indefinite number of quarks). This plasma expands, gets cool and dilute and hadronizes at a certain transition temperature and transition density. The transition density is very close to the saturation density of the nuclear matter and, it is suggested that both these points are very close to the critical point n~1fm^{-3} (quark density) and T~200MeV (temperature).

  19. Phase Diagrams of Strongly Interacting Theories

    DEFF Research Database (Denmark)

    Sannino, Francesco

    2010-01-01

    We summarize the phase diagrams of SU, SO and Sp gauge theories as function of the number of flavors, colors, and matter representation as well as the ones of phenomenologically relevant chiral gauge theories such as the Bars-Yankielowicz and the generalized Georgi-Glashow models. We finally repo...

  20. Phase Diagram of Vertically Shaken Granular Matter

    CERN Document Server

    Eshuis, P; Lohse, D; Van der Meer, D; Van der Weele, K; Bos, Robert; Eshuis, Peter; Lohse, Detlef; Meer, Devaraj van der; Weele, Ko van der

    2006-01-01

    A shallow, vertically shaken granular bed in a quasi 2-D container is studied experimentally yielding a wider variety of phenomena than in any previous study: (1) bouncing bed, (2) undulations, (3) granular Leidenfrost effect, (4) convection rolls, and (5) granular gas. These phenomena and the transitions between them are characterized by dimensionless control parameters and combined in a full experimental phase diagram.

  1. Complexities of One-Component Phase Diagrams

    Science.gov (United States)

    Ciccioli, Andrea; Glasser, Leslie

    2011-01-01

    For most materials, the solid at and near the triple-point temperature is denser than the liquid with which it is in equilibrium. However, for water and certain other materials, the densities of the phases are reversed, with the solid being less dense. The profound consequences for the appearance of the "pVT" diagram of one-component materials…

  2. Fog Machines, Vapors, and Phase Diagrams

    Science.gov (United States)

    Vitz, Ed

    2008-01-01

    A series of demonstrations is described that elucidate the operation of commercial fog machines by using common laboratory equipment and supplies. The formation of fogs, or "mixing clouds", is discussed in terms of the phase diagram for water and other chemical principles. The demonstrations can be adapted for presentation suitable for elementary…

  3. Phase diagram of UCoGe

    Science.gov (United States)

    Mineev, V. P.

    2017-03-01

    The temperature-pressure phase diagram of ferromagnetic superconductor UCoGe includes four phase transitions. They are between the paramagnetic and the ferromagnetic states with the subsequent transition in the superconducting ferromagnetic state and between the normal and the superconducting states after which the transition to the superconducting ferromagnetic state has to occur. Here we have developed the Landau theory description of the phase diagram and established the specific ordering arising at each type of transition. The phase transitions to the ferromagnetic superconducting state are inevitably accompanied by the emergence of screening currents. The corresponding magnetostatics considerations allow for establishing the significant difference between the transition from the ferromagnetic to the ferromagnetic superconducting state and the transition from the superconducting to the ferromagnetic superconducting state.

  4. Review of high pressure phases of calcium by first-principles calculations

    Science.gov (United States)

    Ishikawa, T.; Nagara, H.; Suzuki, N.; Tsuchiya, J.; Tsuchiya, T.

    2010-03-01

    We review high pressure phases of calcium which have obtained by recent experimental and first-principles studies. In this study, we investigated the face-centered cubic (fcc) structure, the body-centered cubic (bcc) structure, the simple cubic (sc) structure, a tetragonal P43212 [Ishikawa T et al. 2008 Phys. Rev. B 77 020101(R)], an orthorhombic Cmca [Ishikawa T et al. 2008 Phys. Rev. B 77 020101(R)], an orthorhombic Cmcm [Teweldeberhan A M and Bonev S A 2008 Phys. Rev. B 78 140101(R)], an orthorhombic Pnma [Yao Y et al. 2008 Phys. Rev. B 78 054506] and a tetragonal I4/mcm(00) [Arapan S et al. 2008 Proc. Natl. Acad. Sci. USA 105 20627]. We compared the enthalpies among the structures up to 200 GPa and theoretically determined the phase diagram of calcium. The sequence of the structural transitions is fcc (0- 3.5 GPa) → bcc (3.5 - 35.7 GPa) → Cmcm (35.7- 52GPa) → P43212 (52-109 GPa) → Cmca (109-117.4GPa) → Pnma (117.4-134.6GPa) → I4/mcm(00) (134.6 GPa -). The sc phase is experimentally observed in the pressure range from 32 to 113 GPa but, in our calculation, there is no pressure region where the sc phase is the most stable. In addition, we found that the enthalpy of the hexagonal close-packed (hcp) structure is lower than that of I4/mcm(00) above 495 GPa.

  5. Novel high-pressure phase of ZrO{sub 2}: An ab initio prediction

    Energy Technology Data Exchange (ETDEWEB)

    Durandurdu, Murat, E-mail: murat.durandurdu@agu.edu.tr

    2015-10-15

    The high-pressure behavior of the orthorhombic cotunnite type ZrO{sub 2} is explored using an ab initio constant pressure technique. For the first time, a novel hexagonal phase (Ni{sub 2}In type) within P6{sub 3}/mmc symmetry is predicted through the simulation. The Ni{sub 2}In type crystal is the densest high-pressure phase of ZrO{sub 2} proposed so far and has not been observed in other metal dioxides at high pressure before. The phase transformation is accompanied by a small volume drop and likely to occur around 380 GPa in experiment. - Graphical abstract: Post-cotunnite Ni{sub 2}In type hexagonal phase forms in zirconia at high pressure. - Highlights: • A post-cotunnite phase is predicted for ZrO{sub 2} through an ab initio simulation. • Cotunnite ZrO{sub 2} adopts the Ni{sub 2}In type structure at high pressure. • The Ni{sub 2}In type structure is the densest high-pressure phase of ZrO{sub 2} proposed so far. • The preferred mechanism in ZrO{sub 2} differs from the other metal dioxides.

  6. Transformation of Hume-Rothery phases under the action of high pressure torsion

    Science.gov (United States)

    Straumal, B. B.; Kilmametov, A. R.; Kucheev, Yu. O.; Kolesnikova, K. I.; Korneva, A.; Zieba, P.; Baretzky, B.

    2014-11-01

    It has been revealed experimentally that high-pressure torsion induces phase transformations of certain Hume-Rothery phases (electron compounds) to others. High-pressure torsion induces the ξ → δ + ɛ reaction in copper-tin alloys with the appearance of the δ + ɛ phase mixture as after long-term annealing in the temperature range T eff = 350-589°C. The mass transfer rate driven by high-pressure torsion is 14-18 orders of magnitude higher than the rate of conventional thermal diffusion at the processing temperature T HPT. This phenomenon can be explained by an increased concentration of defects (in particular, vacancies) in the steady state under high-pressure torsion, which is equivalent to an increase in the temperature.

  7. High pressure structural phase transitions of TiO2 nanomaterials

    Science.gov (United States)

    Quan-Jun, Li; Bing-Bing, Liu

    2016-07-01

    Recently, the high pressure study on the TiO2 nanomaterials has attracted considerable attention due to the typical crystal structure and the fascinating properties of TiO2 with nanoscale sizes. In this paper, we briefly review the recent progress in the high pressure phase transitions of TiO2 nanomaterials. We discuss the size effects and morphology effects on the high pressure phase transitions of TiO2 nanomaterials with different particle sizes, morphologies, and microstructures. Several typical pressure-induced structural phase transitions in TiO2 nanomaterials are presented, including size-dependent phase transition selectivity in nanoparticles, morphology-tuned phase transition in nanowires, nanosheets, and nanoporous materials, and pressure-induced amorphization (PIA) and polyamorphism in ultrafine nanoparticles and TiO2-B nanoribbons. Various TiO2 nanostructural materials with high pressure structures are prepared successfully by high pressure treatment of the corresponding crystal nanomaterials, such as amorphous TiO2 nanoribbons, α-PbO2-type TiO2 nanowires, nanosheets, and nanoporous materials. These studies suggest that the high pressure phase transitions of TiO2 nanomaterials depend on the nanosize, morphology, interface energy, and microstructure. The diversity of high pressure behaviors of TiO2 nanomaterials provides a new insight into the properties of nanomaterials, and paves a way for preparing new nanomaterials with novel high pressure structures and properties for various applications. Project supported by the National Basic Research Program of China (Grant No. 2011CB808200), the National Natural Science Foundation of China (Grant Nos. 11374120, 11004075, 10979001, 51025206, 51032001, and 21073071), and the Cheung Kong Scholars Programme of China.

  8. First-Principles Phase Diagram for Ce-Th System

    Energy Technology Data Exchange (ETDEWEB)

    Landa, A; Soderlind, P; Ruban, A; Vitos, L; Pourovskii, L

    2004-05-11

    Ab initio total energy calculations based on the exact muffin-tin orbitals (EMTO) theory are used to determine the high pressure and low temperature phase diagram of Ce and Th metals as well as the Ce{sub 43}Th{sub 57} disordered alloy. The compositional disorder for the alloy is treated in the framework of the coherent potential approximation (CPA). Equation of state for Ce, Th and Ce{sub 43}Th{sub 57} has been calculated up to 1 Mbar in good comparison with experimental data: upon compression the Ce-Th system undergoes crystallographic phase transformation from an fcc to a bct structure and the transition pressure increases with Th content in the alloy.

  9. Antiferromagnetic phase diagram of the cuprate superconductors

    Science.gov (United States)

    Nunes, L. H. C. M.; Teixeira, A. W.; Marino, E. C.

    2017-02-01

    Taking the spin-fermion model as the starting point for describing the cuprate superconductors, we obtain an effective nonlinear sigma-field hamiltonian, which takes into account the effect of doping in the system. We obtain an expression for the spin-wave velocity as a function of the chemical potential. For appropriate values of the parameters we determine the antiferromagnetic phase diagram for the YBa2Cu3O6+x compound as a function of the dopant concentration in good agreement with the experimental data. Furthermore, our approach provides a unified description for the phase diagrams of the hole-doped and the electron doped compounds, which is consistent with the remarkable similarity between the phase diagrams of these compounds, since we have obtained the suppression of the antiferromagnetic phase as the modulus of the chemical potential increases. The aforementioned result then follows by considering positive values of the chemical potential related to the addition of holes to the system, while negative values correspond to the addition of electrons.

  10. Structure of ice IV, a metastable high-pressure phase

    Science.gov (United States)

    Engelhardt, Hermann; Kamb, Barclay

    1981-12-01

    283.3 pm, which is high relative to other ice structures except ice VII/VIII, reflects similarly the accommodation of a relatively large number (3.75 on average) of nonbonded neighbors around each molecule at relatively short distances of 310-330 pm. Bond bending in ice IV, as measured by deviation of the OṡṡṡOṡṡṡO bond angles from 109.5°, is relatively low compared to most other dense ice structures. All H bonds in ice IV except O(1)ṡṡṡO(1') are required to be proton-disordered by constraints of space-group symmetry. The x-ray structure-factor data indicate that O(1)ṡṡṡO(1') is probably also proton-disordered. Ice IV is the only ice phase other than ice I and Ic to remain proton-disordered on quenching to 77 K. The increased internal energy of ice IV relative to ice V, amounting to about 0.23 kJ mole-1, which underlies the metastability of ice IV in relation to ice V, can be explained structurally as a result of extra overlap and bond-stretching energy in ice IV, partially compensated by extra bond-bending energy in ice V. The structural relation between ice IV and ice I offers a possible explanation for the reduced barrier to nucleation of ice IV, as compared to ice V, in crystallizing from liquid water.

  11. Preparation of high-pressure phase boron nitride films by physical vapor deposition

    CERN Document Server

    Zhu, P W; Zhao, Y N; Li, D M; Liu, H W; Zou Guang Tian

    2002-01-01

    The high-pressure phases boron nitride films together with cubic, wurtzic, and explosive high-pressure phases, were successfully deposited on the metal alloy substrates by tuned substrate radio frequency magnetron sputtering. The percentage of cubic boron nitride phase in the film was about 50% as calculated by Fourier transform infrared measurements. Infrared peak position of cubic boron nitride at 1006.3 cm sup - sup 1 , which is close to the stressless state, indicates that the film has very low internal stress. Transition electron microscope micrograph shows that pure cubic boron nitride phase exits on the surface of the film. The growth mechanism of the BN films was also discussed.

  12. Hydrodynamics of bacterial colonies: Phase diagrams

    Science.gov (United States)

    Lega, J.; Passot, T.

    2004-09-01

    We present numerical simulations of a recent hydrodynamic model describing the growth of bacterial colonies on agar plates. We show that this model is able to qualitatively reproduce experimentally observed phase diagrams, which relate a colony shape to the initial quantity of nutrients on the plate and the initial wetness of the agar. We also discuss the principal features resulting from the interplay between hydrodynamic motions and colony growth, as described by our model.

  13. Phase Diagram Modelling: Nickel - Aluminum - Chromium System

    Science.gov (United States)

    1998-04-01

    conducted by Kaufman and co-workers and their lattice stabilities have formed the basis of phase diagram calculations to the present day.1 In...mol ( 0.74827 Ni + 0.73305E-01 Cr + 0.83609E-02 Al ( 1200.00 C, 1.0000 <—s -.Molten alloy <—s <—s) atm, L- NiCrAl , a=0.82994 ) 0.00000

  14. Fluctuations and the QCD Phase Diagram

    CERN Document Server

    Koch, Volker

    2016-01-01

    In this contribution we will discuss how the study of various fluctuation observables may be used to explore the phase diagram of the strong interaction. We will briefly summarize the present study of experimental and theoretical research in this area. We will then discuss various corrections and issues which need to be understood and applied for a meaningful comparison of experimental measurements with theoretical predictions. This contribution is dedicated to Andrzej Bialas on the occasion of his $80^{\\mathrm{th}}$ birthday.

  15. Metastable phases and "metastable" phase diagrams

    OpenAIRE

    Brazhkin, V. V.

    2006-01-01

    The work discusses specifics of phase transitions for metastable states of substances. The objects of condensed media physics are primarily equilibrium states of substances with metastable phases viewed as an exception, while the overwhelming majority of organic substances investigated in chemistry are metastable. It turns out that at normal pressure many of simple molecular compounds based on light elements (these include: most hydrocarbons; nitrogen oxides, hydrates, and carbides; carbon ox...

  16. Allotropic phase transformation of pure zirconium by high-pressure torsion

    Energy Technology Data Exchange (ETDEWEB)

    Edalati, Kaveh, E-mail: kaveh.edalati@zaiko6.zaiko.kyushu-u.ac.jp [Department of Materials Science and Engineering, Faculty of Engineering, Kyushu University, Fukuoka 819-0395 (Japan); Horita, Zenji [Department of Materials Science and Engineering, Faculty of Engineering, Kyushu University, Fukuoka 819-0395 (Japan); Yagi, Shunsuke; Matsubara, Eiichiro [Department of Materials Science and Engineering, Faculty of Engineering, Kyoto University, Kyoto 606-8501 (Japan)

    2009-10-15

    Pure Zr is processed by high-pressure torsion (HPT) at pressures in the range of 1-40 GPa. A phase transformation occurs from {alpha} to {omega} phase during HPT at pressures above {approx}4 GPa while the total fraction of {omega} phase increases with straining and saturates to a constant level at higher strain. This phase transformation leads to microstructural refinement, hardness and strength enhancement and ductility reduction. Lattice parameter measurements confirm that c for {alpha} phase is expanded about 0.6% by the presence of {omega} phase. The temperature for reverse transformation from {omega} to {alpha} phase increases with straining and thus, straining under high pressure increases thermal stability of {omega} phase. The {omega} phase obtained by HPT is stable for more than 400 days at room temperature.

  17. First-Principles Prediction of High-Pressure Phase of CaC6

    Institute of Scientific and Technical Information of China (English)

    LI Yan; ZHANG Li-Jun; GUI Tian; LIU Yan-Hui; MA Yan-Ming; ZOU Guang-Tian

    2007-01-01

    The lattice dynamics of rhombohedral CaCe is studied as a function of pressure to probe its high pressure phase with low superconducting transition temperature using the density functional liner-response theory. The pressure-induced phase transition in CaC6 is attributable to the softening transverse acoustic (TA) phonon mode at the zone boundary X (0.5, 0.0, 0.5) point. The high pressure phase is then explored by performing fully structural optimization in the supercell which accommodates the atomic displacements corresponding to the eigenvectors of the unstable mode of TA(X). The high-pressure phase is predicted to be a monoclinic unit cell with space group P21/m.

  18. On the relative stability of orthorhombic and hcp phases of beryllium at high pressures

    Energy Technology Data Exchange (ETDEWEB)

    Palanivel, B.; Rao, R.S.; Godwal, B.K.; Sikka, S.K. [High Pressure Physics Division, Bhabha Atomic Research Center, Mumbai (India)

    2000-10-16

    High-pressure electronic properties of Be have been investigated theoretically by means of ab initio electronic structure calculations. The calculations have been carried out by the semi-relativistic full-potential, linear muffin-tin orbital (FPLMTO) method, within the local density approximation. The crystal structure stability among the hcp, bcc and orthorhombic (distorted hcp) phases has been studied as a function of compression. The bcc structure is found to be energetically stable at pressures above 180 GPa. From the results of our calculations, the orthorhombic phase cannot occur as an intermediate phase between the ambient pressure hcp phase and the high-pressure bcc structure. Our work thus suggests the need for more accurate high-pressure x-ray data. (author)

  19. 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...

  20. Ab initio phase diagram of iridium

    Science.gov (United States)

    Burakovsky, L.; Burakovsky, N.; Cawkwell, M. J.; Preston, D. L.; Errandonea, D.; Simak, S. I.

    2016-09-01

    The phase diagram of iridium is investigated using the Z methodology. The Z methodology is a technique for phase diagram studies that combines the direct Z method for the computation of melting curves and the inverse Z method for the calculation of solid-solid phase boundaries. In the direct Z method, the solid phases along the melting curve are determined by comparing the solid-liquid equilibrium boundaries of candidate crystal structures. The inverse Z method involves quenching the liquid into the most stable solid phase at various temperatures and pressures to locate a solid-solid boundary. Although excellent agreement with the available experimental data (to ≲65 GPa) is found for the equation of state (EOS) of Ir, it is the third-order Birch-Murnaghan EOS with B0'=5 rather than the more widely accepted B0'=4 that describes our ab initio data to higher pressure (P ) . Our results suggest the existence of a random-stacking hexagonal close-packed structure of iridium at high P . We offer an explanation for the 14-layer hexagonal structure observed in experiments by Cerenius and Dubrovinsky.

  1. Modeling and Experimental Studies on Phase and Chemical Equilibria in High-Pressure Methanol Synthesis

    NARCIS (Netherlands)

    van Bennekom, Joost G.; Winkelman, Jozef G. M.; Venderbosch, Robertus H.; Nieland, Sebastiaan D. G. B.; Heeres, Hero J.

    2012-01-01

    A solution method was developed to calculate the simultaneous phase and chemical equilibria in high-pressure methanol synthesis (P = 20 MPa, 463 phase and include dew point calculations. A modification of the

  2. Phase transition and high pressure behavior of Zirconium and Niobium carbides

    Science.gov (United States)

    Singh, Archana; Aynyas, Mahendra; Sanyal, Sankar

    2009-03-01

    We have predicted the phase transition pressure (PT)and high pressure behavior of Zirconium and Niobium carbide (ZrC, NbC). The high pressure structural phase transitions in ZrC and NbC has been studied by using a two body inter-ionic potential model, which includes the Coulomb screening effect, due to the semi-metallic nature of these compounds. These transition metal carbides have been found to undergo NaCl (B1) to CsCl (B2)-type structural phase transition, at high pressure like other binary systems. We predict such structural transformation in ZrC and NbC at a pressure of 98GPa and 85GPa respectively. We have also predicted second order elastic constant and bulk modulus. The present theoretical work has been compared with the corresponding experimental data and prediction of LAPW and GGA and LDA theories.

  3. Phase diagram of twisted mass lattice QCD

    Science.gov (United States)

    Sharpe, Stephen R.; Wu, Jackson M.

    2004-11-01

    We use the effective chiral Lagrangian to analyze the phase diagram of two-flavor twisted mass lattice QCD as a function of the normal and twisted masses, generalizing previous work for the untwisted theory. We first determine the chiral Lagrangian including discretization effects up to next-to-leading order (NLO) in a combined expansion in which m2π/(4πfπ)2˜aΛ (a being the lattice spacing, and Λ=ΛQCD). We then focus on the region where m2π/(4πfπ)2˜(aΛ)2, in which case competition between leading and NLO terms can lead to phase transitions. As for untwisted Wilson fermions, we find two possible phase diagrams, depending on the sign of a coefficient in the chiral Lagrangian. For one sign, there is an Aoki phase for pure Wilson fermions, with flavor and parity broken, but this is washed out into a crossover if the twisted mass is nonvanishing. For the other sign, there is a first order transition for pure Wilson fermions, and we find that this transition extends into the twisted mass plane, ending with two symmetrical second order points at which the mass of the neutral pion vanishes. We provide graphs of the condensate and pion masses for both scenarios, and note a simple mathematical relation between them. These results may be of importance to numerical simulations.

  4. Phase diagram of quantum square ice

    Science.gov (United States)

    Henry, Louis-Paul; Holdsworth, Peter; Mila, Frederic; Roscilde, Tommaso

    2013-03-01

    We have investigated the ground-state and finite-temperature phase diagram of quantum square ice - realized by the transverse-field Ising model on a checkerboard lattice - using both linear spin-wave (LSW) theory and quantum Monte Carlo (QMC). We generalize the model with different couplings between nearest (J1) and next-to-nearest (J2) neighbors on the checkerboard lattice. Our QMC approach generalizes the loop algorithm - very efficient in the study of constrained classical systems - to a ``brane algorithm'' for quantum systems. At the LSW level the vast degeneracy of the ground-state for J1 =J2 and J2 >J1 remains intact; moreover LSW theory breaks down in extended regions of the phase diagram, pointing at non-classical states. Our QMC study goes beyond perturbative schemes and addresses directly the nature of the low-temperature phases. We have critically examined the possibility of a resonating-plaquette state for J1 =J2 , suggested by degenerate perturbation theory on the ice-rule manifold for weak fields. Our QMC results for finite fields confirm the absence of Néel or collinear order, but they do not confirm the presence of resonating-plaquette order, pointing at a possibly more complex non-classical state.

  5. The magnetized effective QCD phase diagram

    CERN Document Server

    Ayala, Alejandro; Hernandez, L A; Loewe, M; Zamora, R

    2015-01-01

    The QCD phase diagram in the temperature versus quark chemical potential plane is studied in the presence of a magnetic field, using the linear sigma model coupled to quarks. It is shown that the decrease of the couplings with increasing field strength obtained in this model leads to the critical temperature for the phase transition to decrease with increasing field intensity (inverse magnetic catalysis). This happens provided that plasma screening is properly accounted for. It is also found that with increasing field strength the location of the critical end point (CEP) in the phase diagram moves toward lower values of the critical quark chemical potential and larger values of the critical temperature. In addition, the CEP approaches the temperature axis for large values of the magnetic field. We argue that a similar behavior is to be expected in QCD, since the physical impact of the magnetic field, regardless of strength, is to produce a spatial dimension reduction, whereby virtual quark-antiquark pairs are...

  6. Phase Diagram of the Frustrated Hubbard Model

    Science.gov (United States)

    Zitzler, R.; Tong, N.-H.; Pruschke, Th.; Bulla, R.

    2004-07-01

    The Mott-Hubbard metal-insulator transition in the paramagnetic phase of the one-band Hubbard model has long been used to describe similar features in real materials like V2O3. In this Letter we investigate the antiferromagnetic phase of this model with frustration. At T=0 we find a first-order transition from a paramagnetic metal to an antiferromagnetic insulator. We show that even in the presence of strong magnetic frustration, the paramagnetic metal-insulator transition is hidden inside an extended antiferromagnetic region. This raises the question of whether the one-band Hubbard model with frustration is sufficient to describe the phase diagram of V2O3 or similar transition metal oxides even qualitatively.

  7. QCD phase diagram with isospin chemical potential

    CERN Document Server

    Brandt, Bastian B

    2016-01-01

    In this contribution we investigate the phase diagram of QCD in the presence of an isospin chemical potential. To alleviate the infrared problems of the theory associated with pion condensation, we introduce the pionic source as an infrared regulator. We discuss various methods to extrapolate the results to vanishing pionic source, including a novel method based on the singular value spectrum of the massive Dirac operator, a leading-order reweighting and a spline Monte-Carlo fit. Our main results concern the phase transition boundary between the normal and the pion condensation phases and the chiral/deconfinement transition temperature as a function of the chemical potential. In addition, we perform a quantitative comparison between our direct results and a Taylor-expansion obtained at zero chemical potential to assess the applicability range of the latter.

  8. Understanding starch gelatinization: The phase diagram approach.

    Science.gov (United States)

    Carlstedt, Jonas; Wojtasz, Joanna; Fyhr, Peter; Kocherbitov, Vitaly

    2015-09-20

    By constructing a detailed phase diagram for the potato starch-water system based on data from optical microscopy, synchrotron X-ray scattering and differential scanning calorimetry, we show that gelatinization can be interpreted in analogy with a eutectic transition. The phase rule explains why the temperature of the gelatinization transition (G) is independent on water content. Furthermore, the melting (M1) endotherm observed in DSC represents a liquidus line; the temperature for this event increases with increasing starch concentration. Both the lamellar spacing and the inter-helix distance were observed to decrease with increasing starch content for starch concentrations between approximately 65 wt% and 75 wt%, while the inter-helix distance continued decreasing upon further dehydration. Understanding starch gelatinization has been a longstanding challenge. The novel approach presented here shows interpretation of this phenomenon from a phase equilibria perspective. Copyright © 2015 Elsevier Ltd. All rights reserved.

  9. Superconducting phase prepared from Ta{sub 3}Si under high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Murao, R; Kusaba, K; Fukuoka, K; Sugiyama, K; Syono, Y [IMR, Tohoku University 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Kikuchi, M [Kansei Fukushi Research Center, Tohoku Fukushi University1-8-1 Kunimi, Aoba-ku, Sendai, Miyagi 981-8522 (Japan); Atou, T [SMC, Materials and Structures Lab. Tokyo Tech. 4259 Nagatsuta-cho Midori-ku, Yokohama, Kanagawa 226-8503 (Japan); Kikegawa, T, E-mail: r_murao@imr.tohoku.ac.j [IMSS, KEK, Oho 1-1, Tsukuba, Ibaraki 305-0801 (Japan)

    2010-03-01

    High-pressure behaviour of Ta{sub 3}Si intermetallic compound was investigated by shock compression and static compression methods. Superconducting phase with T{sub C} = 9.3 K was found in the sample shocked to 50-61 GPa, however most of the shock recovered sample indicated the starting stable phase with the Ti{sub 3}P-type structure. The new superconducting phase was not obtained from static compression up to 15 GPa and 800 {sup 0}C. Bulk modulus of Ta{sub 3}Si with the Ti{sub 3}P-type structure was determined to be K{sub 0} = 246(4) GPa. The present results suggest that a rapid phase transformation occurred during shock compression, but most of the high-pressure phase was reverted to the stable phase in the decompression process.

  10. Low pressure phase diagram of CeCoGe{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Mizoo, Masakazu; Nishioka, Takashi; Kato, Harukazu; Matsumura, Masahiro, E-mail: nisioka@kochi-u.ac.jp [Graduate School of Integrated Arts and Sciences, Kochi University, Kochi 780-8520 (Japan)

    2011-01-01

    We have performed measurements of the Hall magnetization and electrical resistivity on a pressure-induced antiferromagnetic heavy fermion superconductor CeCoGe{sub 3} at pressures up to {approx}1.7 GPa, which crystallizes in the tetragonal BaNiSn{sub 3}-type structure without inversion symmetry. We have clarified that five successive phase transitions appear at ambient pressure. As pressure is applied, these transitions approach one another until {approx}1.2 GPa, and then separate again. We have also found another phase transition emerges above {approx}0.5 GPa, which is consistent with a recent Co-NQR study. From these results, we propose a low pressure P-T phase diagram, which contains at least eight ordered phases below {approx}2 GPa. This phase diagram is consistent with a recent reported high pressure phase diagram.

  11. Phase diagram of colloid-rod system

    Science.gov (United States)

    Lai, S. K.; Xiao, Xuhui

    2010-01-01

    The semigrand ensemble theory [H. N. W. Lekkerkerker, W. C. K. Poon, P. N. Pusey, A. Stroobants, and P. B. Warren, Europhys. Lett. 20, 559 (1992)] in conjunction with the fundamental measure density functional theory [V. B. Warshavsky and X. Song, Phys. Rev. E 69, 061113 (2004)] are used to construct the Helmholtz free energy densities of a mixture of uncharged colloidal hard spheres and colloidal rods in its solid and liquid phases. Given these free energy density functions, we apply the free energy density minimization method [G. F. Wang and S. K. Lai, Phys. Rev. E 70, 051402 (2004)] to crosshatch the system's regions of phases in coexistence. The calculated results show that the triangular area bounded by gas-liquid, gas-solid, and liquid-solid coexisting two phases which has been called the coexistence region of gas-liquid-solid corresponds in fact to sets of two phases in coexistence. The phase boundaries which define our calculated coexistence domains compare very well with previous theoretical calculations. The relevance of the phase-diagram domains to three phases in coexistence will be discussed.

  12. Phase Diagram of Spiking Neural Networks

    Directory of Open Access Journals (Sweden)

    Hamed eSeyed-Allaei

    2015-03-01

    Full Text Available In computer simulations of spiking neural networks, often it is assumed that every two neurons of the network are connected by a probablilty of 2%, 20% of neurons are inhibitory and 80% are excitatory. These common values are based on experiments, observations. but here, I take a different perspective, inspired by evolution. I simulate many networks, each with a different set of parameters, and then I try to figure out what makes the common values desirable by nature. Networks which are configured according to the common values, have the best dynamic range in response to an impulse and their dynamic range is more robust in respect to synaptic weights. In fact, evolution has favored networks of best dynamic range. I present a phase diagram that shows the dynamic ranges of different networks of different parameteres. This phase diagram gives an insight into the space of parameters -- excitatory to inhibitory ratio, sparseness of connections and synaptic weights. It may serve as a guideline to decide about the values of parameters in a simulation of spiking neural network.

  13. High pressure phase transitions in scheelite structured fluoride: ErLiF{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Garg, Nandini; Mishra, A.K.; Poswal, H.K. [High Pressure and Synchrotron Radiation Physics Division, Mumbai (India); Tyagi, A.K. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Sharma, Surinder M [High Pressure and Synchrotron Radiation Physics Division, Mumbai (India)

    2015-09-15

    Our synchrotron based angle dispersive x-ray diffraction studies on scheelite structured ErLiF{sub 4} show that it undergoes two phase transitions, at ~11.5 and ~15.5 GPa to lower symmetry monoclinic phases, before becoming (irreversibly) amorphous at ~28 GPa. The first high pressure phase transformation to the fergusonite structure (space group I2/a) is found to be of thermodynamically second order. The second high pressure phase could be fitted to the P2/c space group, but detailed analysis rules out the wolframite structure (P2/c space group), common to many scheelite compounds under high pressures. We also suggest that despite the ionic character of the LiF{sub 4} tetrahedra, the compressibility of LnLiF{sub 4} (Ln=Eu–Lu) kind of scheelites is more affected by the LnF{sub 8} dodecahedra than the LiF{sub 4} tetrahedra. - Graphical abstract: Volume per formula unit of the scheelite and high pressure phases of ErLiF{sub 4} as a function of pressure. - Highlights: • ErLiF{sub 4} transforms to fergusonite and P2/c phase at high pressure. • Polyhedra of LnF{sub 8} affects compressibility of LnLiF{sub 4} (Ln=Eu–Lu) more than LiF{sub 4}. • Amorphization pressure varies inversely in LnLiF{sub 4} with ionic size of Ln cation. • In ErLiF{sub 4}a/c ratio reduces with pressure in contrast to reported increase in YLiF{sub 4}.

  14. High-pressure Al-rich hexagonal phases-What are their kin?

    DEFF Research Database (Denmark)

    Makovicky, Emil; Olsen, Lars Arnskov

    2008-01-01

    The hexagonal Al-rich high-pressure phases are members of a structural family with the same type of framework composed of double-ribbons of edge-sharing octahedra, but variably occupied trigonal and hexagonal channels. This family includes jaffeite, fluoborite, yeremeyevite, painite, and synthetic...

  15. Phase field simulations of plastic strain-induced phase transformations under high pressure and large shear

    Science.gov (United States)

    Javanbakht, Mahdi; Levitas, Valery I.

    2016-12-01

    Pressure and shear strain-induced phase transformations (PTs) in a nanograined bicrystal at the evolving dislocations pile-up have been studied utilizing a phase field approach (PFA). The complete system of PFA equations for coupled martensitic PT, dislocation evolution, and mechanics at large strains is presented and solved using the finite element method (FEM). The nucleation pressure for the high-pressure phase (HPP) under hydrostatic conditions near a single dislocation was determined to be 15.9 GPa. Under shear, a dislocation pile-up that appears in the left grain creates strong stress concentration near its tip and significantly increases the local thermodynamic driving force for PT, which causes nucleation of HPP even at zero pressure. At pressures of 1.59 and 5 GPa and shear, a major part of a grain transforms to HPP. When dislocations are considered in the transforming grain as well, they relax stresses and lead to a slightly smaller stationary HPP region than without dislocations. However, they strongly suppress nucleation of HPP and require larger shear. Unexpectedly, the stationary HPP morphology is governed by the simplest thermodynamic equilibrium conditions, which do not contain contributions from plasticity and surface energy. These equilibrium conditions are fulfilled either for the majority of points of phase interfaces or (approximately) in terms of stresses averaged over the HPP region or for the entire grain, despite the strong heterogeneity of stress fields. The major part of the driving force for PT in the stationary state is due to deviatoric stresses rather than pressure. While the least number of dislocations in a pile-up to nucleate HPP linearly decreases with increasing applied pressure, the least corresponding shear strain depends on pressure nonmonotonously. Surprisingly, the ratio of kinetic coefficients for PT and dislocations affect the stationary solution and the nanostructure. Consequently, there are multiple stationary solutions

  16. Phase Diagrams for Systems Containing Hyperbranched Polymers

    Directory of Open Access Journals (Sweden)

    Tim Zeiner

    2012-01-01

    Full Text Available Hyperbranched polymers show an outstanding potential for applications ranging from chemistry over nanotechnology to pharmacy. In order to take advantage of this potential, the underlying phase behaviour must be known. From the thermodynamic point of view, the modelling of these phase diagrams is quite challenging, because the thermodynamic properties depend on the architecture of the hyperbranched polymer as well as on the number and kind of present functional end groups. The influence of architecture can be taken into account via the lattice cluster theory (LCT as an extension of the well-known Flory–Huggins theory. Whereas the Flory–Huggins theory is limited to linear polymer chains, the LCT can be applied to an arbitrary chain architecture. The number and the kind of functional groups can be handled via the Wertheim perturbation theory, applicable for directed forces between the functional groups and the surrounding solvent molecules. The combination of the LCT and the Wertheim theory can be established for the modelling or even prediction of the liquid-liquid equilibria (LLE of polymer solutions in a single solvent or in a solvent mixture or polymer blends, where the polymer can have an arbitrary structure. The applied theory predicts large demixing regions for mixtures of linear polymers and hyperbranched polymers, as well as for mixtures made from two hyperbranched polymers. The introduction of empty lattice sites permits the theoretical investigation of pressure effects on phase behaviour. The calculated phase diagrams were compared with own experimental data or to experimental data taken from literature.

  17. Stability of rhombohedral phases in vanadium at high-pressure and high-temperature: first-principles investigations

    Science.gov (United States)

    Wang, Yi X.; Wu, Q.; Chen, Xiang R.; Geng, Hua Y.

    2016-09-01

    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 of the Fermi level has a significant impact on the phase stability, and follows the band-filling argument. Besides the Fermi surface nesting, we find that the localization/delocalization of the d orbitals also contributes to the instability of rhombohedral distortions in vanadium.

  18. Phase Diagrams of Silicate Systems: Handbook; Third Issue; Ternary Systems

    Science.gov (United States)

    In the third issue of the handbook Phase Diagrams of Silicate Systems, information is included on the phase relationships in systems containing...radioelectronics, nuclear engineering, etc. Not only are equilibrium phase diagrams presented in the handbook, but the phases existing in the

  19. High-pressure Raman scattering of CaWO₄ up to 46.3 GPa: evidence of a new high-pressure phase.

    Science.gov (United States)

    Botella, Pablo; Lacomba-Perales, Raúl; Errandonea, Daniel; Polian, Alain; Rodríguez-Hernández, Placida; Muñoz, Alfonso

    2014-09-15

    The high-pressure behavior of CaWO4 was analyzed at room temperature by Raman spectroscopy. Pressure was generated using a diamond-anvil cell and Ne as pressure-transmitting medium. The pressure range of previous studies has been extended from 23.4 to 46.3 GPa. The experiments reveal the existence of two reversible phase transitions. The first one occurs from the tetragonal scheelite structure to the monoclinic fergusonite structure and is observed at 10 GPa. The onset of a previously unknown second transition is found at 33.4 GPa. The two high-pressure phases coexist up to 39.4 GPa. The Raman spectra measured for the low-pressure phase and the first high-pressure phase are consistent with previous studies in the pressure range where comparison is possible. The pressure dependence of all the Raman-active modes is reported for different phases. We also report total-energy and lattice-dynamics calculations, which determine the occurrence of two phase transitions in the pressure range covered by the experiments. The first transition is in full agreement with experiments (scheelite-to-fergusonite). According to calculations, the second-highest pressure phase has an orthorhombic structure (space group Cmca). Details of this structure, its Raman modes, and its electronic band structure are given. The reliability of the reported results is supported by the consistency between the theoretical and experimental values obtained for transition pressures, phonon frequencies, and phonon pressure coefficients.

  20. Phase diagram of a Schelling segregation model

    Science.gov (United States)

    Gauvin, L.; Vannimenus, J.; Nadal, J.-P.

    2009-07-01

    The collective behavior in a variant of Schelling’s segregation model is characterized with methods borrowed from statistical physics, in a context where their relevance was not conspicuous. A measure of segregation based on cluster geometry is defined and several quantities analogous to those used to describe physical lattice models at equilibrium are introduced. This physical approach allows to distinguish quantitatively several regimes and to characterize the transitions between them, leading to the building of a phase diagram. Some of the transitions evoke empirical sudden ethnic turnovers. We also establish links with ‘spin-1’ models in physics. Our approach provides generic tools to analyze the dynamics of other socio-economic systems.

  1. High-pressure phases in SnO2 to 117 GPa

    Science.gov (United States)

    Shieh, Sean R.; Kubo, Atsushi; Duffy, Thomas S.; Prakapenka, Vitali B.; Shen, Guoyin

    2006-01-01

    X-ray diffraction of SnO2 (cassiterite) at high pressures and temperatures demonstrates the existence of four phase transitions to 117 GPa. The observed sequence of phases for SnO2 is rutile-type (P42/mnm)→CaCl2-type(Pnnm)→pyrite-type(Pa3¯)→ZrO2 orthorhombic phase I (Pbca)→cotunnite-type(Pnam) . Our observations of the first three phases are generally in agreement with earlier studies. The orthorhombic phase I and cotunnite-type structure (orthorhombic phase II) were observed in SnO2 for the first time. The Pbca phase is found at 50-74 GPa during room-temperature compression. The cotunnite-type structure was synthesized when SnO2 was compressed to 74 GPa and heated at 1200 K. The cotunnite-type form was observed during compression between 54-117 GPa with additional laser heating carried out at 91 and 111 GPa. Fitting the pressure-volume data for the high-pressure phases to the second-order Birch-Murnaghan equation of state yields a bulk modulus of 259(26) GPa for the Pbca phase and 417(7) GPa for the cotunnite-type phase.

  2. High pressure phase transition in Zr–Ni binary system: A first principle study

    Energy Technology Data Exchange (ETDEWEB)

    Mukherjee, Debojyoti, E-mail: debojyoti@barc.gov.in; Sahoo, B.D.; Joshi, K.D.; Gupta, Satish C.

    2015-11-05

    Total energy calculations have been performed on zirconium–nickel (with 50% nickel by atom) binary system to examine its structural stability under high pressure. The evolutionary structure search method in conjunction with density functional theory based projector augmented wave (PAW) method suggested that at zero pressure an orthorhombic phase with space group symmetry Cmcm is the lowest enthalpy structure, in agreement with the experiments. Further, it has been predicted that upon compression at ∼10 GPa, this structure will transform to a lower symmetry triclinic phase (space group P-1) which will remain stable up to ∼50 GPa, the maximum pressure of the present calculations. To support the results of our static lattice calculations, we performed lattice dynamic calculations also on Cmcm and P-1 structures. Lattice dynamic calculations correctly showed that at ambient condition the Cmcm phase is dynamically stable. Further, these calculations carried around the Cmcm to P-1 transition pressure predicted that the Cmcm phase will become unstable dynamically due to failure of acoustic zone boundary phonons, suggesting that the Cmcm to P-1 transition is phonon driven. For P-1 phase our calculations showed that this structure is dynamically stable not only at high pressures but also at ambient condition, indicating that at pressure lower than 10 GPa this phase could be a metastable structure. Further, we have calculated the elastic constants for both the phase at various pressures. - Highlights: • Pressure induced phonon driven orthorhombic to triclinic phase transformations in Zr–Ni binary system at ∼10 GPa. • Elastic and lattice dynamic stability of orthorhombic and triclinic phase. • Exploitation of evolutionary structure searching method to explore high pressure phase of Zr–Ni material.

  3. The Phase Transition of Eu2O3 under High Pressures

    Institute of Scientific and Technical Information of China (English)

    JIANG Sheng; BAI Li-Gang; LIU Jing; XIAO Wan-Sheng; LI Xiao-Dong; LI Yan-Chun; TANG Ling-Yun; ZHANG Yu-Feng; ZHANG De-Chun; ZHENG Li-Rong

    2009-01-01

    Pressure-induced phase transition of cubic Eu2Oa is studied by angle-dispersive x-ray diffraction (ADXD) up to 42.3 GPa at room temperature. A structural transformation from a cubic phase to a hexagonal phase is observed,which starts at 5.0 GPa and finishes at about 13.1 GPa. The phase transition leads to a volume collapse of 9.0% at 8.6 GPa. The hexagonal phase of Eu2O3 maintains stable up to the highest experiment pressure. After release of pressure, the high-pressure phase transforms to a monoclinic phase. The pressure-volume data are fitted with the Birch-Murnaghan equation of state. The bulk moduli obtained upon compression from the fitting are 145(2) GPa and 151(6) GPa for the cubic and hexagonal phases, respectively, when their first pressure derivatives are fixed at 4.

  4. Fully Consistent Finite-Strain Landau Theory for High-Pressure Phase Transitions

    Science.gov (United States)

    Tröster, A.; Schranz, W.; Karsai, F.; Blaha, P.

    2014-07-01

    Landau theory (LT) is an indispensable cornerstone in the thermodynamic description of phase transitions. As with structural transitions, most applications require one to consistently take into account the role of strain. If temperature drives the transition, the relevant strains are, as a rule, small enough to be treated as infinitesimal, and therefore one can get away with linearized elasticity theory. However, for transitions driven by high pressure, strains may become so large that it is absolutely mandatory to treat them as finite and deal with the nonlinear nature of the accompanying elastic energy. In this paper, we explain how to set up and apply what is, in fact, the only possible consistent Landau theory of high-pressure phase transitions that systematically allows us to take these geometrical and physical nonlinearities into account. We also show how to incorporate available information on the pressure dependence of elastic constants taken from experiment or simulation. We apply our new theory to the example of the high-pressure cubic-tetragonal phase transition in strontium titanate, a model perovskite that has played a central role in the development of the theory of structural phase transitions. Armed with pressure-dependent elastic constants calculated by density-functional theory, we give an accurate description of recent high-precision experimental data and predict a number of elastic transition anomalies accessible to experiments.

  5. Phase transition studies of the exsoluted ilmenite-hematite at high pressure and temperature conditions

    Science.gov (United States)

    Kim, Y.; Secco, R.; Hwang, G.; Bao, X.; Ming, L.

    2011-12-01

    Ilmenite minerals found in Switzerland Alpe Arami peridotite massif indicate that these precipitates are metastable phases converted from the single perovskite phase during the ascending process in the mantle. After this work, lots of subsequent high pressure-temperature experiments on ilmenite itself and its solid solution phases were performed to check the phase boundary from the starting phase to perovskite structure. This study also aims to identify the phase transition sequence(s) of the exsoluted ilmenite-hematite specimen where its locality is the Allard Lake area, Quebac, Canada, under high pressure and high temperature conditions. Bulky ore sample consists of 76.2% ilmenite and 23.8% hematite in volume. Chemistry of ilmenite is Fe1.02Mg0.13Ti0.92O3 and that of hematite, Fe2O3. Lattice parameters of ilmenite are a=5.08287(2)Å, c=14.0511(1)Å, and those of hematite a=5.04378(4)Å, c=13.7757(2)Å. Walker-type large volume multi anvil cell was employed for high pressure and high temperature experiment up to 14GPa and 2400K, respectively. Recovered samples after high pressure-temperature treatment were subjected to identify the product phase(s) by the general area detector x-ray diffraction method with conventional x-radiation as well as the x-ray micro-diffraction technique using synchrotron radiation. Phase transition sequences observed are the followings: starting exsoluted ilmenite-hematite phase transforms to the single phase of perovskite, then this perovskite phase disproportionate into various kind of oxides. Phase boundaries to perovskite, then to oxides were determined to be P(GPa)=31.8 - 0.0178T(K), and P(GPa)=23.8 - 0.0072T(K), respectively. Present result is different from the previous reports of Syono et al. (1980)(i.e., P(GPa)=25.2 - 0.01T(K)) and Ming et al. (2006)(i.e., P(GPa)=16.0 - 0.0012T(K)). Based on the present results applied to the Alpe Arami peridotite massif, source region would be much shallower part at the upper mantle(i.e., 240km

  6. Phase diagram of one-patch colloids forming tubes and lamellae.

    Science.gov (United States)

    Preisler, Zdenek; Vissers, Teun; Smallenburg, Frank; Munaò, Gianmarco; Sciortino, Francesco

    2013-08-15

    We numerically calculate the equilibrium phase diagram of one-patch particles with 30% patch coverage. It has been previously shown that in the fluid phase these particles organize into extremely long tubelike aggregates (G. Munaò et al. Soft Matter 2013, 9, 2652). Here, we demonstrate by means of free-energy calculations that such a disordered tube phase, despite forming spontaneously from the fluid phase below a density-dependent temperature, is always metastable against a lamellar crystal. We also show that a crystal of infinitely long packed tubes is thermodynamically stable, but only at high pressure. The full phase diagram of the model, beside the fluid phase, displays four different stable crystals. A gas-liquid critical point, and hence a liquid phase, is not detected.

  7. High-pressure fluid-phase equilibria: Experimental methods and systems investigated (2005-2008)

    DEFF Research Database (Denmark)

    Fonseca, José; Dohrn, Ralf; Peper, Stephanie

    2011-01-01

    A review of systems is given, for which experimental high-pressure phase-equilibrium data were published in the period between 2005 and 2008, continuing a series of reviews. To find candidates for articles that are of interest for this survey a three-stage search strategy was used including...... a systematic search of the contents of the 17 most important journals of the field. Experimental methods for the investigation of high-pressure phase equilibria were classified, described and illustrated using examples from articles of the period between 2005 and 2008. For the systems investigated......, the reference, the temperature and pressure range of the data, and the experimental method used for the measurements is given in 54 tables. Vapor–liquid equilibria, liquid–liquid equilibria, vapor–liquid–liquid equilibria, solid–liquid equilibria, solid–vapor equilibria, solid–vapor–liquid equilibria, critical...

  8. Exploring the QCD phase diagram through relativistic heavy ion collisions

    CERN Document Server

    Mohanty, Bedangadas

    2013-01-01

    We present a review of the studies related to establishing the QCD phase diagram through high energy nucleus-nucleus collisions. We particularly focus on the experimental results related to the formation of a quark-gluon phase, crossover transition and search for a critical point in the QCD phase diagram.

  9. Water, Water Everywhere: Phase Diagrams of Ordinary Water Substance

    Science.gov (United States)

    Glasser, L.

    2004-01-01

    The full phase diagram of water in the form of a graphical representation of the three-dimensional (3D) PVT diagram using authentic data is presented. An interesting controversy regarding the phase behavior of water was the much-touted proposal of a solid phase of water, polywater, supposedly stable under atmospheric conditions.

  10. Role of relativity in high-pressure phase transitions of thallium.

    Science.gov (United States)

    Kotmool, Komsilp; Chakraborty, Sudip; Bovornratanaraks, Thiti; Ahuja, Rajeev

    2017-02-20

    We demonstrate the relativistic effects in high-pressure phase transitions of heavy element thallium. The known first phase transition from h.c.p. to f.c.c. is initially investigated by various relativistic levels and exchange-correlation functionals as implemented in FPLO method, as well as scalar relativistic scheme within PAW formalism. The electronic structure calculations are interpreted from the perspective of energetic stability and electronic density of states. The full relativistic scheme (FR) within L(S)DA performs to be the scheme that resembles mostly with experimental results with a transition pressure of 3 GPa. The s-p hybridization and the valence-core overlapping of 6s and 5d states are the primary reasons behind the f.c.c. phase occurrence. A recent proposed phase, i.e., a body-centered tetragonal (b.c.t.) phase, is confirmed with a small distortion from the f.c.c. phase. We have also predicted a reversible b.c.t. → f.c.c. phase transition at 800 GPa. This finding has been suggested that almost all the III-A elements (Ga, In and Tl) exhibit the b.c.t. → f.c.c. phase transition at extremely high pressure.

  11. Phase transition and elastic properties of zinc sulfide under high pressure from first principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Wei [Hubei Univ. of Education, Wuhan (China). Dept. of Physics and Electronics; Chinese Academy of Engineering Physics, Mianyang (China). Inst. of Fluid Physics; Song, Jin-Fan; Wang, Ping; Lu, Cheng; Lu, Zhi-Wen [Nanyang Normal Univ. (China). Dept. of Physics; Tan, Xiao-Ming [Ludong Univ., Yantai (China). Dept. of Physics

    2011-10-15

    A theoretical investigation on structural and elastic properties of zinc sulfide semiconductor under high pressure is performed by employing the first-principles method based on the density functional theory. The calculated results show that the transition pressure P{sub t} for the structural phase transition from the B3 structure to the B1 structure is 17.04 GPa. The calculated values are generally speaking in good agreement with experiments and with similar theoretical calculations. (orig.)

  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. The Dy-Zn phase diagram

    Science.gov (United States)

    Saccone, A.; Cardinale, A. M.; Delfino, S.; Ferro, R.

    2003-03-01

    The dysprosium-zinc phase diagram has been investigated over its entire composition range by using differential thermal analysis, (DTA) metallographic analysis, X-ray powder diffraction, and electron probe microanalysis (EPMA). Seven intermetallic phases have been found and their structures confirmed. DyZn, DyZn2, Dy13Zn58, and Dy2Zn17 melt congruently at 1095 °C, 1050 °C, 930 °C, and 930 °C, respectively. DyZn3, Dy3Zn11, and DyZn12 form through peritectic reactions at 895 °C, about 900 °C and 685 °C, respectively. Four eutectic reactions occur at 850 °C and 30.0 at pct Zn (between (Dy) and DyZn), 990 °C and 60.0 at pct Zn (between DyZn and DyZn2), 885 °C and 76.0 at pct Zn (between DyZn3 and Dy3Zn11), and 875 °C and 85.0 at pct Zn (involving Dy13Zn58 and Dy2Zn17). The Dy-rich end presents a catatectic equilibrium; a degenerate invariant effect has been found in the Zn-rich region. The phase equilibria of the Dy-Zn alloys are discussed and compared with those of the other known RE-Zn systems (RE=rare earth metal) in view of the regular change in the relative stabilities of the phases across the lanthanide series

  14. Enantiomeric 3-chloromandelic acid system: binary melting point phase diagram, ternary solubility phase diagrams and polymorphism.

    Science.gov (United States)

    Le Minh, Tam; von Langermann, Jan; Lorenz, Heike; Seidel-Morgenstern, Andreas

    2010-09-01

    A systematic study of binary melting point and ternary solubility phase diagrams of the enantiomeric 3-chloromandelic acid (3-ClMA) system was performed under consideration of polymorphism. The melting point phase diagram was measured by means of thermal analysis, that is, using heat-flux differential scanning calorimetry (DSC). The results reveal that 3-ClMA belongs to the racemic compound-forming systems. Polymorphism was found for both the enantiomer and the racemate as confirmed by X-ray powder diffraction analysis. The ternary solubility phase diagram of 3-ClMA in water was determined between 5 and 50 degrees C by the classical isothermal technique. The solubilities of the pure enantiomers are extremely temperature-dependent. The solid-liquid equilibria of racemic 3-ClMA are not trivial due to the existence of polymorphism. The eutectic composition in the chiral system changes as a function of temperature. Further, solubility data in the alternative solvent toluene are also presented.

  15. Phase transformation of Ho[subscript 2]O[subscript 3] at high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Sheng; Liu, Jing; Li, Xiaodong; Bai, Ligang; Xiao, Wansheng; Zhang, Yufeng; Lin, Chuanlong; Li, Yanchun; Tang, Lingyun (Chinese Aca. Sci.)

    2012-01-20

    The structural stability of cubic Ho{sub 2}O{sub 3} under high pressure has been investigated by angle-dispersive x-ray diffraction (ADXD) in a diamond anvil cell up to 63.0 GPa at room temperature. The diffraction data reveal two structural transformations on compression. The structural transformation from a cubic to a monoclinic structure starts at 8.9 GPa and is complete at 16.3 GPa with an {approx}8.1% volume collapse. A hexagonal phase begins to appear at {approx}14.8 GPa and becomes dominant at 26.4 GPa. This high-pressure hexagonal phase with a small amount of retained monoclinic phase is stable up to the highest pressure of 63.0 GPa in this study. After release of pressure, the hexagonal phase transforms to a monoclinic structure. A third-order Birch-Murnaghan fit yields zero pressure bulk moduli (B{sub 0}) of 206(3), 200(7) and 204(19) GPa and their pressure derivatives (B'{sub 0}) of 4.8(4), 2.1(4), 3.8(5) for the cubic, monoclinic and hexagonal phases, respectively. Comparing with other rare-earth sesquioxides, it is suggested that the transition pressure from cubic to monoclinic phase, as well as the bulk modulus of the cubic phase, increases with the decreasing of the cation radius of rare-earth sesquioxides.

  16. Structural phase transitions in Bi2Se3 under high pressure

    Science.gov (United States)

    Yu, Zhenhai; Wang, Lin; Hu, Qingyang; Zhao, Jinggeng; Yan, Shuai; Yang, Ke; Sinogeikin, Stanislav; Gu, Genda; Mao, Ho-Kwang

    2015-11-01

    Raman spectroscopy and angle dispersive X-ray diffraction (XRD) experiments of bismuth selenide (Bi2Se3) have been carried out to pressures of 35.6 and 81.2 GPa, respectively, to explore its pressure-induced phase transformation. The experiments indicate that a progressive structural evolution occurs from an ambient rhombohedra phase (Space group (SG): R-3m) to monoclinic phase (SG: C2/m) and eventually to a high pressure body-centered tetragonal phase (SG: I4/mmm). Evidenced by our XRD data up to 81.2 GPa, the Bi2Se3 crystallizes into body-centered tetragonal structures rather than the recently reported disordered body-centered cubic (BCC) phase. Furthermore, first principles theoretical calculations favor the viewpoint that the I4/mmm phase Bi2Se3 can be stabilized under high pressure (>30 GPa). Remarkably, the Raman spectra of Bi2Se3 from this work (two independent runs) are still Raman active up to ~35 GPa. It is worthy to note that the disordered BCC phase at 27.8 GPa is not observed here. The remarkable difference in atomic radii of Bi and Se in Bi2Se3 may explain why Bi2Se3 shows different structural behavior than isocompounds Bi2Te3 and Sb2Te3.

  17. High pressure structural phase transition and elastic properties of Ga1-xInxAs semiconducting compounds

    Science.gov (United States)

    Varshney, D.; Joshi, G.

    2009-08-01

    The present paper addresses the high-pressure phase transformation and mechanical properties of Ga1-xInxAs (x = 0.25, 0.5 and 0.75) by formulating an effective interionic interaction potential. This potential consists of the long-range Coulomb and charge transfer caused by the deformation of the electron shells of the overlapping ions and the Hafemeister and Flygare type short-range overlap repulsion extended upto the second neighbor ions and the van der Waals (vdW) interaction. The estimated values of phase transition pressure and the vast volume discontinuity in pressure-volume ( PV) phase diagram indicate the structural phase transition from zinc blende (B3) to rock salt (B1). The equation of state curves plotted between V (P)/ V (0) and pressure are for both the zincblende (B3) and rocksalt (B1) structures. Further, the variations of the second and third order elastic constants with pressure have followed a systematic trend, which are almost identical to those exhibited by the observed data measured for other compounds of this family.

  18. THE SYSTEM NEODYMIUM - MANGANESE (STRUCTURES, MAGNETIC PROPERTIES, PHASE DIAGRAM), THE PHASE DIAGRAMS YB-HG AND TB-HG,

    Science.gov (United States)

    ALLOYS, YTTERBIUM, TERBIUM, MANGANESE ALLOYS, MERCURY ALLOYS, X RAY DIFFRACTION, X RAY SPECTROSCOPY, DIFFERENTIAL THERMAL ANALYSIS, PHASE DIAGRAMS , MAGNETIC PROPERTIES, CRYSTAL STRUCTURE, METALLOGRAPHY, AUSTRIA

  19. A new high-pressure phase transition in natural Fe-bearing orthoenstatite

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jin S.; Dera, Przemyslaw; Bass, Jay D. (UC); (UIUC)

    2016-07-29

    Single-crystal X-ray structure refinements have been carried out on natural Fe-bearing orthoenstatite (OEN) at pressures up to 14.53 GPa. We report a new high-pressure phase transition from OEN to a monoclinic phase (HPCEN2) with space group P2{sub 1}/c, with a density change of {approx}1.9(3)%. The HPCEN2 phase is crystallographically different from low-pressure clinoenstatite (LPCEN), which also has P2{sub 1}/c symmetry. Upon release of pressure HPCEN2 reverts to OEN, and the transition pressure is bracketed between 9.96 and 14.26 GPa at room temperature. We find no evidence for a C2/c phase at high pressure. The lattice constants for the new phase at 14.26 GPa are a = 17.87(2), b = 8.526(9), c = 4.9485(10) {angstrom}, {beta} = 92.88(4){sup o} [{rho} = 3.658(9) g/cm{sup 3}]. Refinement of the new structure indicates rotation of tetrahedral chain as the key characteristic of this transition. This experiment points to the possibility of OEN and HPCEN2 as the stable phases in Earth's upper mantle.

  20. High-pressure phase transition and properties of spinel ZnMn2O4

    DEFF Research Database (Denmark)

    Åbrink, S.; Waskowska, A.; Gerward, Leif

    1999-01-01

    X-ray photoelectron spectroscopy, magnetic measurements, and a single-crystal x-ray structure determination at normal pressure have shown that Jahn-Teller active manganese ions in ZnMn2O4 are present in one valence state (III) on the octahedral sites of the spinel structure. The high-pressure beh...... of the Mn3+ ions is moved to the d(x2-y2) level, which is revealed as an abrupt fall of observed magnitude of the distortion of the bulk crystal above P-c. [S0163-1829(99)08341-1].......X-ray photoelectron spectroscopy, magnetic measurements, and a single-crystal x-ray structure determination at normal pressure have shown that Jahn-Teller active manganese ions in ZnMn2O4 are present in one valence state (III) on the octahedral sites of the spinel structure. The high......-pressure behavior of ZnMn2O4 was investigated up to 52 GPa using the energy-dispersive x-ray diffraction technique and synchrotron radiation. The structural first-order phase transition from the body-centered to primitive-tetragonal cell takes place at P-c = 23 GPa. The high-pressure phase is metastable down...

  1. Phase stability and structural distortion of NiO under high pressure

    Institute of Scientific and Technical Information of China (English)

    ZHANG Wei-bing; HU Yu-lin; TANG Bi-yu

    2006-01-01

    The phase stability and structural distortion of NiO under high pressure were investigated using first-principles calculations based on density-functional theory. Different forms of exchange-correlation functional including LDA,GGA and GGA+U were used in the present calculations. All of the three methods predict NiO to be AFM II ordering with the cell slightly compressed along [111] direction and also indicate that there is no structural phase transition of NiO under pressure up to 140 GPa,which are in agreement with the experiment. However,both LDA and GGA incorrectly predict the structural distortion under pressure especially above 60 GPa. Only when strong correlations are included in form of GGA+U,structural distortion under high pressure can qualitatively agree with the experiment. The related mechanism was also analyzed and discussed. These results suggest that the strong electronic correlations still play a very important role in the properties of NiO under high pressure.

  2. Computation of Space Shuttle high-pressure cryogenic turbopump ball bearing two-phase coolant flow

    Science.gov (United States)

    Chen, Yen-Sen

    1990-01-01

    A homogeneous two-phase fluid flow model, implemented in a three-dimensional Navier-Stokes solver using computational fluid dynamics methodology is described. The application of the model to the analysis of the pump-end bearing coolant flow of the high-pressure oxygen turbopump of the Space Shuttle main engine is studied. Results indicate large boiling zones and hot spots near the ball/race contact points. The extent of the phase change of the liquid oxygen coolant flow due to the frictional and viscous heat fluxes near the contact areas has been investigated for the given inlet conditions of the coolant.

  3. The dysprosium-tin phase diagram

    Energy Technology Data Exchange (ETDEWEB)

    Eremenko, V.N.; Bulanova, M.V.; Martsenjuk, P.S. (I.N. Frantsevich Inst. for Problems of Materials Science, Kiev (Ukraine))

    1992-12-07

    The dysprosium-tin phase diagram was established by means of differential thermal, X-ray and microscopic analyses of 22 alloys. Seven intermetallic compounds were found to exist in the system. Dy[sub 5]Sn[sub 3] melts congruently at 1870 degC, and undergoes a polymorphous transformation at 1823 [+-] 6 degC. The intermetallics Dy[sub 5]Sn[sub 4], Dy[sub 11]Sn[sub 10], DySn, Dy[sub 4]Sn[sub 5], DySn[sub 2], DySn[sub 3] are formed peritectically at 1712 [+-]11, 1605 [+-]12, 1208 [+-]3, 1166 [+-]7, 1138 [+-]3 and 747 [+-]6 degC respectively. DySn[sub 3] exists in a narrow temperature range, in two polymorphous modifications. The transformation [beta]-DySn[sub 3] [yields] [alpha]-DySn[sub 3] occurs at 608 [+-] 12 degC, and at 499 [+-]2 degC [alpha]-DySn[sub 3] decomposes to DySn[sub 2] and the tin-rich melt. The dysprosium-rich eutectic crystallizes at 1204 [+-]10 degC and contains 13 at.% tin. The solid-state solubility of tin in dysprosium is about 3 at.%, and that of dysprosium in tin is negligible.

  4. Phase Transition and EOS of Cinnabar (α-HgS) at High Pressure and High Temperature

    Institute of Scientific and Technical Information of China (English)

    FAN Da-Wei; ZHOU Wen-Ge; LIU Cong-Qiang; WAN Fang; XING Yin-Suo; LIU Jing; LI Yan-Chun; XIE Hong-Sen

    2009-01-01

    @@ Phase relations and equation of state (EOS) of natural cinnabar (α-HgS) are investigated by high-pressure and high-temperature synchrotron x-ray powder diffraction. The unambiguous cinnabar-rocksalt structure phase boundaries are determined to be Plower(Gpa)=15.54-0.014T(℃) and Pupper(Gpa)= 23.84 - 0.014T(℃) at 300--623K. With K' axed at 4, we obtain K0 = 37(4) Gpa, ( K/ T)p=-0.025(2) GPaK-1, and α0= 3.79(20)× 10-5 K-1 for the cinnabar phase of α-HgS. The ( K/ T)p and α0 of cinnabar phase are obtained for the first time. A nearly isotropic compression of cinnabar phase is observed by linear regressions.

  5. An Introductory Idea for Teaching Two-Component Phase Diagrams

    Science.gov (United States)

    Peckham, Gavin D.; McNaught, Ian J.

    2011-01-01

    The teaching of two-component phase diagrams has attracted little attention in this "Journal," and it is hoped that this article will make a useful contribution. Current physical chemistry textbooks describe two-component phase diagrams adequately, but do so in a piecemeal fashion one section at a time; first solid-liquid equilibria, then…

  6. Phase stability and magnetic behavior of hexagonal phase of N2-O2 system with kagome lattice under high pressure and low temperature

    Science.gov (United States)

    Akahama, Y.; Ishihara, D.; Yamashita, H.; Fujihisa, H.; Hirao, N.; Ohishi, Y.

    2016-08-01

    The pressure-temperature (P -T ) phase diagram of N2-O2 mixture with a composition of N2-48 mol % O2 has been investigated using x-ray diffraction and the phase stability of a hexagonal phase (space group: P 6 /mmm), with the kagome lattice examined under high-pressure and low-temperature conditions. While the phase appears as a low-temperature phase of the cubic phase (P m 3 n ) with the structure of γ -O2 or δ -N2 and is stable in a wide range of pressures and temperatures, it transforms to lower symmetry monoclinic or orthorhombic phases at lower temperature, accompanied with a distortion of the kagome lattice. Based on Rietveld refinements, the monoclinic and orthorhombic phases are found to be in the P 21/a and Cmmm space groups, respectively. In magnetization measurements, a magnetic transition is observed with a relatively large drop of magnetization, corresponding to the cubic-to-hexagonal phase transition. This suggests that the hexagonal phase has a certain magnetic ordered state that arises from the molecular magnetic moment of O2.

  7. Calculation of Gallium-metal-Arsenic phase diagrams

    Science.gov (United States)

    Scofield, J. D.; Davison, J. E.; Ray, A. E.; Smith, S. R.

    1991-01-01

    Electrical contacts and metallization to GaAs solar cells must survive at high temperatures for several minutes under specific mission scenarios. The determination of which metallizations or alloy systems that are able to withstand extreme thermal excursions with minimum degradation to solar cell performance can be predicted by properly calculated temperature constitution phase diagrams. A method for calculating a ternary diagram and its three constituent binary phase diagrams is briefly outlined and ternary phase diagrams for three Ga-As-X alloy systems are presented. Free energy functions of the liquid and solid phase are approximated by the regular solution theory. Phase diagrams calculated using this method are presented for the Ga-As-Ge and Ga-As-Ag systems.

  8. High-pressure structural phase transitions in chromium-doped BaFe2As2

    Energy Technology Data Exchange (ETDEWEB)

    Uhoya, Walter [University of Alabama, Birmingham; Brill, Joseph W. [University of Kentucky; Montgomery, Jeffrey M [University of Alabama, Birmingham; Samudrala, G K [University of Alabama, Birmingham; Tsoi, Georgiy [University of Alabama, Birmingham; Vohra, Y. K. [University of Alabama, Birmingham; Weir, S. T. [Lawrence Livermore National Laboratory (LLNL); Safa-Sefat, Athena [ORNL

    2012-01-01

    We report on the results from high pressure x-ray powder diffraction and electrical resistance measurements for hole doped BaFe{sub 2-x}Cr{sub x}As{sub 2} (x = 0, 0.05, 0.15, 0.4, 0.61) up to 81 GPa and down to 10 K using a synchrotron source and diamond anvil cell (DAC). At ambient temperature, an isostructural phase transition from a tetragonal (T) phase (I4/mmm) to a collapsed tetragonal (CT) phase is observed at 17 GPa. This transition is found to be dependent on ambient pressure unit cell volume and is slightly shifted to higher pressure upon increase in the Cr-doping. Unlike BaFe{sub 2}As{sub 2} which superconduct under high pressure, we have not detected any evidence of pressure induced superconductivity in chromium doped samples in the pressure and temperature range of this study. The measured equation of state parameters are presented for both the tetragonal and collapsed tetragonal phases for x = 0.05, 0.15, 0.40 and 0.61.

  9. Phase equilibrium data and thermodynamic modelling of the system (propane + DMF + methanol) at high pressures

    Energy Technology Data Exchange (ETDEWEB)

    Charin, Rafael M. [Department of Chemical Engineering, Federal University of Parana (UFPR), Polytechnic Center (DTQ/ST/UFPR), Jardim das Americas, Curitiba 82530-990, PR (Brazil); Department of Food Engineering, URI - Campus de Erechim, Av. Sete de Setembro, 1621, Erechim 99700-000, RS (Brazil); Corazza, Marcos L.; Ndiaye, Papa M. [Department of Chemical Engineering, Federal University of Parana (UFPR), Polytechnic Center (DTQ/ST/UFPR), Jardim das Americas, Curitiba 82530-990, PR (Brazil); Rigo, Aline A.; Mazutti, Marcio A. [Department of Food Engineering, URI - Campus de Erechim, Av. Sete de Setembro, 1621, Erechim 99700-000, RS (Brazil); Vladimir Oliveira, J., E-mail: vladimir@uricer.edu.b [Department of Food Engineering, URI - Campus de Erechim, Av. Sete de Setembro, 1621, Erechim 99700-000, RS (Brazil)

    2011-03-15

    Reported in this work are phase equilibrium data at high pressures for the binary and ternary systems formed by {l_brace}propane + N,N-dimethylformamide (DMF) + methanol{r_brace}. Phase equilibrium measurements were performed in a high-pressure, variable-volume view cell, following the static synthetic method for obtaining the experimental bubble and dew points transition data over the temperature range of (363 to 393) K, pressures up to 11.5 MPa and overall mole fraction of the lighter component varying from 0.1 to 0.995. For the systems investigated, vapour-liquid (VLE), liquid-liquid (LLE) and vapour-liquid-liquid (VLLE) phase transitions were visually recorded. Results show that the systems investigated present UCST (upper critical solution temperature) phase transition curves with an UCEP (upper critical end point) at a temperature higher than the propane critical temperature. The experimental data were modelled using the Peng-Robinson equation of state with the Wong-Sandler and the classical quadratic mixing rules, affording a satisfactory representation of the experimental data.

  10. High pressure-induced distortion in face-centered cubic phase of thallium

    Science.gov (United States)

    Kotmool, Komsilp; Li, Bing; Chakraborty, Sudip; Bovornratanaraks, Thiti; Luo, Wei; Mao, Ho-kwang; Ahuja, Rajeev

    2016-10-01

    The complex and unusual high-pressure phase transition of III-A (i.e. Al, Ga, and In) metals have been investigated in the last several decades because of their interesting periodic table position between the elements having metallic and covalent bonding. Our present first principles-based electronic structure calculations and experimental investigation have revealed the unusual distortion in face-centered cubic (f.c.c.) phase of the heavy element thallium (Tl) induced by the high pressure. We have predicted body-centered tetragonal (b.c.t) phase at 83 GPa using an evolutionary algorithm coupled with ab initio calculations, and this prediction has been confirmed with a slightly distorted parameter (2 × a - c)/c lowered by 1% using an angle-dispersive X-ray diffraction technique. The density functional theory (DFT)-based calculations suggest that s-p mixing states and the valence-core overlapping of 6s and 5d states play the most important roles for the phase transitions along the pathway h.c.p→b.c.t.

  11. Ferrian Ilmenites: Investigating the Magnetic Phase Diagram

    Science.gov (United States)

    Lagroix, F.

    2007-12-01

    The main objective of this study is to investigate the magnetic phase changes within the hematite-ilmenite solid solution, yFeTiO3·(1-y)·Fe2O3. Two sets of synthetic ferrian ilmenites of y-values equal to 0.7, 0.8, 0.9, and 1.0 were available for this study. As currently drawn, the magnetic phase diagram, proposed by Ishikawa et al. [1985, J. Phys. Soc. Jpn. v.54, 312-325], predicts for increasing y values (0.5phase changes for the different compositions investigated. The y=1.0 sample, pure ilmenite, is antiferromagnetic below 57K, the measured Néel temperature. The y=0.9 sample magnetically orders at about 100K in a superparamagnetic state. Hysteresis loops remain effectively closed down to 60K below which an antiferromagnetic order prior to reaching the spin glass state is ambiguous. The y=0.8 sample magnetically orders at about 270K in an initially superparamagnetic states before entering a ferrimagnetic state below about 250K. Lastly, as previously demonstrated in Lagroix et al. [2004, JGR-B, v.109, doi:10.1029/2004JB003076], the y=0.7 samples order ferrimagnetically at 380K. However, like the y=0.7 samples which also demonstrated an antiferromagnetic state at temperature above the Curie temperature, hysteresis loops for y=0.9 and y=0.8 only achieve perfect linearity at 190K and 340K respectively. All samples (except y=1.0) show a frequency dependent amplitude non

  12. High-pressure Phase Equilibria for Binary Ethanol System Containing Supercritical CO2

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    High-pressure phase behavior of supercritical (SC) CO2+ethanol system was investigated at 333.2 K, 348.2 K, 353.2 K, 368.2 K, 413.2 K and 453.2 K and pressure from 2.0 MPa to 14.3 MPa. The measurement was carried out in a cylindrical autoclave with a moveable piston and a window for adjustment and observation of phase equilibria at given T and p. The samples were taken from two coexisting phases and were analyzed to obtain their compositions. It is shown that the solubility of SC CO2 in ethanol increases drastically with pressures at the given temperature, but the content of ethanol in CO2-rich phase increase faintly.

  13. High-pressure Phase Equilibria for Binary Ethanol System Containing Supercriticai CO2

    Institute of Scientific and Technical Information of China (English)

    朱虎刚; 田宜灵; 陈丽; 秦颖; 冯季军

    2001-01-01

    High-pressure phase behavior of supercritical (SC) CO2+ethanol system was investigated at 333.2 K,348.2K, 353.2K, 368.2K, 413.2K and 453.2K and pressure from 2.0MPa to 14.3MPa. The measurement was carried out in a cylindrical autoclave with a moveable piston and a window for adjustment and observation of phase equilibria at given T and p. The samples were taken from two coexisting phases and were analyzed to obtain their compositions. It is shown that the solubility of SC CO2 in ethanol increases drastically with pressures at the given temperature, but the content of ethanol in CO2-rich phase increase faintly.

  14. Phase transition and superconductivity of SrFe2As2 under high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Uhoya, Walter [University of Alabama, Birmingham; Montgomery, Jeffrey M [University of Alabama, Birmingham; Tsoi, Georgiy [University of Alabama, Birmingham; Vohra, Yogesh [University of Alabama, Birmingham; McGuire, Michael A [ORNL; Sefat, A. S. [Oak Ridge National Laboratory (ORNL); Sales, Brian C [ORNL; Weir, S. T. [Lawrence Livermore National Laboratory (LLNL)

    2011-01-01

    High pressure x-ray diffraction and electrical resistance measurements have been carried out on SrFe{sub 2}As{sub 2} to a pressure of 23 GPa and temperature of 10 K using a synchrotron source and designer diamond anvils. At ambient temperature, a phase transition from the tetragonal phase to a collapsed tetragonal (CT) phase is observed at 10 GPa under non-hydrostatic conditions. The experimental relation that T-CT transition pressure for 122 Fe-based superconductors is dependent on ambient pressure volume is affirmed. The superconducting transition temperature is observed at 32 K at 1.3 GPa and decreases rapidly with a further increase of pressure in the region where the T-CT transition occurs. Our results suggest that T{sub C} falls below 10 K in the pressure range of 10-18 GPa where the CT phase is expected to be stable.

  15. High-temperature and high-pressure phase transitions in uranium

    Science.gov (United States)

    Bouchet, J.; Bottin, F.

    2017-02-01

    The phase diagram of uranium has been explored up to 100 GPa and 2000 K by means of ab initio molecular dynamics (AIMD) simulations. The lattice dynamics and energetics of the stable phases observed experimentally in this range of pressure and temperature are studied in this work. The phonon spectra of the α and γ phases are shown to evolve strongly as a function of temperature, unveiling the huge anharmonic effects present in this material. If the elastics constants and the bulk and shear moduli of the γ phase do not disclose any temperature effects, the shear modulus of the α phase decreases strongly as a function of temperature. Using the pressure- and temperature-dependent vibrational density of states and the Gibbs free energy of these two structures, we found a line transition between the α and γ phases which slightly underestimates the experimental one. Coherently with experiments, the bct structure is never found stable between 0 and 100 GPa.

  16. Synthesis and equation of state of high pressure phase of chromium-bearing spinel

    Science.gov (United States)

    Shieh, S. R.; Khan, T.; Prescher, C.; Prakapenka, V.; MI, Z.

    2015-12-01

    Chromium-bearing spinel (Mg,Fe)Cr2O4 can be found in the Earth's crust, upper mantle, and even in meteorites. Mantle derived chromium-bearing spinel suggests that its high pressure phase may be existing at deep mantle but however its high pressure elastic property is not well understood yet. In situ synchrotron X-ray diffraction studies of magnesiochromite and chromite using the laser-heated diamond anvil cell were performed at GSECARS, Advanced Photon Source, to explore their high pressure phases and elastic property. Our results on magnesiochromite showed dissociation of MgCr2O4 to Cr2O3+MgO at ~15 GPa and to modified Ludwigite (mLd)-type Mg2Cr2O5+Cr2O3 below and above ~1500 K, respectively. At above 20 GPa, only a single phase CaTi2O4-type structure of MgCr2O4 was observed at 1400-2000 K. Pressure-volume data of CaTi2O4 type structure of MgCr2O4 fitted to Birch-Murnaghan equation of state yield zero-pressure volume (V0) = 264.4(8) Å3, bulk modulus (K0) = 185.4(4) GPa, and pressure derivative (K0') = 4; and mLd-type Mg2Cr2O5 yields: V0 = 338.9(8) Å3, K0 = 186.5(6) GPa, K0' = 4. For CaTi2O4 type structure of natural chromite, our fitted P-V data show V0 = 261(1) Å3, K0 = 175.4(2) GPa, and K0' = 4.

  17. Nanomaterials under high-pressure.

    Science.gov (United States)

    San-Miguel, Alfonso

    2006-10-01

    The use of high-pressure for the study and elaboration of homogeneous nanostructures is critically reviewed. Size effects, the interaction between nanostructures and guest species or the interaction of the nanosystem with the pressure transmitting medium are emphasized. Phase diagrams and the possibilities opened by the combination of pressure and temperature for the elaboration of new nanomaterials is underlined through the examination of three different systems: nanocrystals, nano-cage materials which include fullerites and group-14 clathrates, and single wall nanotubes. This tutorial review is addressed to scientist seeking an introduction or a panoramic view of the study of nanomaterials under high-pressure.

  18. High-pressure fluid-phase equilibria: Experimental methods and systems investigated (2000-2004)

    DEFF Research Database (Denmark)

    Dohrn, Ralf; Peper, Stephanie; Fonseca, José

    2010-01-01

    , and the experimental method used for the measurements are given in 54 tables. Most of experimental data in the literature have been given for binary systems. Of the 1204 binary systems, 681 (57%) have carbon dioxide as one of the components. Information on 156 pure components, 451 ternary systems of which 267 (62......%) contain carbon dioxide, 150 multicomponent and complex systems, and 129 systems with hydrates is given. Experimental methods for the investigation of high-pressure phase equilibria are classified and described. Work on the continuation of the review series is under way, covering the period between 2005...

  19. Reverse phase ion pair high pressure liquid chromatographic determination of ethylenediaminetetraacetic acid in crabmeat and mayonnaise.

    Science.gov (United States)

    Perfetti, G A; Warner, C R

    1979-09-01

    A method is described for the determination of ethylenediaminetetraacetic acid (EDTA) in crabmeat and mayonnaise. EDTA is extracted from the food sample with water and converted to its copper chelate, which is then quantitated by reverse phase ion pair high pressure liquid chromatography with ultraviolet detection. Maximum sensitivity is obtained with detection at about 254 nm; higher wavelengths may be used for enhanced specificity. Cleanup procedures for crabmeat and mayonnaise were improved by using a radiotracer method. Analyses of crabmeat and mayonnaise samples spiked at 3 different levels showed greater than 90% recovery of EDTA.

  20. Hydrostatic Compression Behavior and High-Pressure Stabilized β-Phase in γ-Based Titanium Aluminide Intermetallics

    Directory of Open Access Journals (Sweden)

    Klaus-Dieter Liss

    2016-07-01

    Full Text Available Titanium aluminides find application in modern light-weight, high-temperature turbines, such as aircraft engines, but suffer from poor plasticity during manufacturing and processing. Huge forging presses enable materials processing in the 10-GPa range, and hence, it is necessary to investigate the phase diagrams of candidate materials under these extreme conditions. Here, we report on an in situ synchrotron X-ray diffraction study in a large-volume press of a modern (α2 + γ two-phase material, Ti-45Al-7.5Nb-0.25C, under pressures up to 9.6 GPa and temperatures up to 1686 K. At room temperature, the volume response to pressure is accommodated by the transformation γ → α2, rather than volumetric strain, expressed by the apparently high bulk moduli of both constituent phases. Crystallographic aspects, specifically lattice strain and atomic order, are discussed in detail. It is interesting to note that this transformation takes place despite an increase in atomic volume, which is due to the high ordering energy of γ. Upon heating under high pressure, both the eutectoid and γ-solvus transition temperatures are elevated, and a third, cubic β-phase is stabilized above 1350 K. Earlier research has shown that this β-phase is very ductile during plastic deformation, essential in near-conventional forging processes. Here, we were able to identify an ideal processing window for near-conventional forging, while the presence of the detrimental β-phase is not present under operating conditions. Novel processing routes can be defined from these findings.

  1. Rare twin linked to high-pressure phase transition in iron

    Energy Technology Data Exchange (ETDEWEB)

    Dougherty, L.M. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)], E-mail: lmdough@lanl.gov; Gray, G.T.; Cerreta, E.K.; McCabe, R.J.; Field, R.D.; Bingert, J.F. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    2009-05-15

    At approximately 13 GPa, body-centered cubic alpha-iron undergoes a fully reversible, pressure-induced phase transition into hexagonal close-packed epsilon-iron. Microstructural evidence of this phase transition has been identified in the fully reverted alpha-iron as a large number of {l_brace}3 3 2{r_brace}<113> twins found primarily as secondary twins within {l_brace}1 1 2{r_brace}<111> primary twins. The {l_brace}3 3 2{r_brace}<113> twins were produced during high-pressure shock-loading of 1018 steel at a peak pressure above the alpha-epsilon phase transition pressure. The twins were identified using electron backscattered diffraction and transmission electron microscopy.

  2. A New High Pressure Phase and the Equation of State of YbH2

    DEFF Research Database (Denmark)

    Staun Olsen, J.; Buras, B.; Gerward, Leif

    1984-01-01

    High-pressure X-ray diffraction studies have been performed on YbH2 up to 28 GPa. A first order phase transition from an orthorhombic structure to a collapsed hexagonal structure with c/a = 1.34 has been observed at about 15 GPa. The transition is accompanied by a 5.2% decrease in volume. Fitting...... the V(P) data to Murnaghan's equation of state yields the bulk modulus B0 = 40.2 GPa and its pressure derivative B'0 = 4.75 for the orthorhombic phase. For the hexagonal phase we find the bulk modulus to be B = B0 = 138 GPa independent of pressure, i.e. B'0 = 0....

  3. Phase stability of TiH{sub 2} under high pressure and temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Selva Vennila, R.; Durygin, A.; Saxena, S.K. [Center for Study of Matter at Extreme Conditions (CeSMEC), Florida International University, VH-150, University Park, Miami, FL 33199 (United States); Merlini, Marco [European Synchrotron Radiation Facility (ESRF), Grenoble 38043 (France); Wang, Zhongwu [Cornell High Energy Synchrotron Source (CHESS), Wilson Laboratory, Cornell University, Ithaca, NY 14853 (United States)

    2008-11-15

    Phase stability of titanium hydride (TiH{sub 2}) was studied at high pressure-high temperature conditions using synchrotron radiation under non-hydrostatic conditions. Resistive heating method was used to heat the sample to a maximum temperature of 873 K in a diamond anvil cell (DAC) under pressure up to 12 GPa. Pressure-temperature behavior was studied by varying the temperature upto 823 K in steps of 50 K with pressure variations within 3 GPa. Structural phase transformation from tetragonal (I4/mmm) to cubic (Fm-3 m) was observed with increase in temperature. Tetragonal phase was found to be stabilized when the sample was subjected to pressure and temperature cycle. (author)

  4. Phase Behavior at High Pressure of the Ternary System: CO2, Ionic Liquid and Disperse Dye

    Directory of Open Access Journals (Sweden)

    Helen R. Mazzer

    2012-01-01

    Full Text Available High pressure phase behavior experimental data have been measured for the systems carbon dioxide (CO2 + 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim] [PF6] and carbon dioxide (CO2 + 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim] [PF6] + 1-amino-2-phenoxy-4-hydroxyanthraquinone (C.I. Disperse Red 60. Measurements were performed in the pressure up to 18 MPa and at the temperature (323 to 353 K. As reported in the literature, at higher concentrations of carbon dioxide the phase transition pressure increased very steeply. The experimental data for the binary and ternary systems were correlated with good agreement using the Peng-Robinson equation of state. The amount of water in phase behavior of the systems was evaluated.

  5. Hybrid functional study rationalizes the simple cubic phase of calcium at high pressures.

    Science.gov (United States)

    Liu, Hanyu; Cui, Wenwen; Ma, Yanming

    2012-11-14

    Simple cubic (SC) phase has been long experimentally determined as the high-pressure phase III of elemental calcium (Ca) since 1984. However, recent density functional calculations within semi-local approximation showed that this SC phase is structurally unstable by exhibiting severely imaginary phonons, and is energetically unstable with respect to a theoretical body-centered tetragonal I4(1)/amd structure over the pressure range of phase III. These calculations generated extensive debates on the validity of SC phase. Here we have re-examined the SC structure by performing more precise density functional calculations within hybrid functionals of Heyd-Scuseria-Erhzerhof and PBE0. Our calculations were able to rationalize fundamentally the phase stability of SC structure over all other known phases by evidence of its actual energetic stability above 33 GPa and its intrinsically dynamical stability without showing any imaginary phonons in the entire pressure range studied. We further established that the long-thought theoretical I4(1)/amd structure remains stable in a narrow pressure range before entering SC phase and is actually the structure of experimental Ca-III(') synthesized recently at low temperature 14 K as supported by the excellent agreement between our simulated x-ray diffraction patterns and the experimental data. Our results shed strong light on the crucial role played by the precise electron exchange energy in a proper description of the potential energy of Ca.

  6. Nanosecond Ultrasonics to Study Phase Transitions in Solid and Liquid Systems at High Pressure and Temperature

    Energy Technology Data Exchange (ETDEWEB)

    Bonner, B P; Berge, P A; Carlson, S C; Farber, D L; Akella, J

    2007-03-21

    This report describes the development of a high-frequency ultrasonic measurement capability for application to the study of phase transitions at elevated pressure and temperature. We combined expertise in various aspects of static high-pressure technique with recent advances in wave propagation modeling, ultrasonic transducer development, electronic methods and broadband instrumentation to accomplish the goals of this project. The transduction and electronic systems have a demonstrated bandwidth of 400 MHz, allowing investigations of phenomena with characteristic times as short as 2.5 nS. A compact, pneumatically driven moissanite anvil cell was developed and constructed for this project. This device generates a high-pressure environment for mm dimension samples to pressures of 3 GPa. Ultrasonic measurements were conducted in the moissanite cell, an LLNL multi-anvil device and in a modified piston cylinder device. Measurements for water, and elemental tantalum, tin and cerium demonstrate the success of the methods. The {gamma}-{alpha} phase transition in cerium was clearly detected at {approx}0.7 GPa with 75 MHz longitudinal waves. These results have direct application to important problems in LLNL programs, as well as seismology and planetary science.

  7. Using a Spreadsheet To Explore Melting, Dissolving and Phase Diagrams.

    Science.gov (United States)

    Goodwin, Alan

    2002-01-01

    Compares phase diagrams relating to the solubilities and melting points of various substances in textbooks with those generated by a spreadsheet using data from the literature. Argues that differences between the diagrams give rise to new chemical insights. (Author/MM)

  8. Phase diagrams and kinetics of phase transitions in protein solutions.

    Science.gov (United States)

    Vekilov, Peter G

    2012-05-16

    The phase behavior of proteins is of interest for fundamental and practical reasons. The nucleation of new phases is one of the last major unresolved problems of nature. The formation of protein condensed phases (crystals, polymers, and other solid aggregates, as well as dense liquids and gels) underlies pathological conditions, plays a crucial role in the biological function of the respective protein, or is an essential part of laboratory and industrial processes. In this review, we focus on phase transitions of proteins in their properly folded state. We first summarize the recently acquired understanding of physical processes underlying the phase diagrams of the protein solutions and the thermodynamics of protein phase transitions. Then we review recent findings on the kinetics of nucleation of dense liquid droplets and crystals. We explore the transition from nucleation to spinodal decomposition for liquid-liquid separation and introduce the new concept of solution-to-crystal spinodal. We review the two-step mechanism of protein crystal nucleation, in which mesoscopic metastable protein clusters serve as precursors to the ordered crystal nuclei. The concepts and mechanisms reviewed here provide powerful tools for control of the nucleation process by varying the solution thermodynamic parameters.

  9. Phase diagrams of binary mixtures of oppositely charged colloids.

    Science.gov (United States)

    Bier, Markus; van Roij, René; Dijkstra, Marjolein

    2010-09-28

    Phase diagrams of binary mixtures of oppositely charged colloids are calculated theoretically. The proposed mean-field-like formalism interpolates between the limits of a hard-sphere system at high temperatures and the colloidal crystals which minimize Madelung-like energy sums at low temperatures. Comparison with computer simulations of an equimolar mixture of oppositely charged, equally sized spheres indicate semiquantitative accuracy of the proposed formalism. We calculate global phase diagrams of binary mixtures of equally sized spheres with opposite charges and equal charge magnitude in terms of temperature, pressure, and composition. The influence of the screening of the Coulomb interaction upon the topology of the phase diagram is discussed. Insight into the topology of the global phase diagram as a function of the system parameters leads to predictions on the preparation conditions for specific binary colloidal crystals.

  10. Phase diagrams of binary crystalline-crystalline polymer blends.

    Science.gov (United States)

    Matkar, Rushikesh A; Kyu, Thein

    2006-08-17

    A thermodynamically self-consistent theory has been developed to establish binary phase diagrams for two-crystalline polymer blends by taking into consideration all interactions including amorphous-amorphous, crystal-amorphous, amorphous-crystal, and crystal-crystal interactions. The present theory basically involves combination of the Flory-Huggins free energy for amorphous-amorphous isotropic mixing and the Landau free energy of polymer solidification (e.g., crystallization) of the crystalline constituents. The self-consistent solution via minimization of the free energy of the mixture affords determination of eutectic, peritectic, and azeotrope phase diagrams involving various coexistence regions such as liquid-liquid, liquid-solid, and solid-solid coexistence regions bound by liquidus and solidus lines. To validate the present theory, the predicted eutectic phase diagrams have been compared with the reported experimental binary phase diagrams of blends such as polyethylene fractions as well as polycaprolactone/trioxane mixtures.

  11. A dialogue about protein crystallization and phase diagrams.

    Science.gov (United States)

    Asherie, Neer

    2012-07-01

    A lighthearted researcher and a disheartened student discuss the challenges of protein crystallization and how phase diagrams can be used to address these challenges. The student feels a little better afterwards, but many proteins remain uncrystallized.

  12. High pressure phase transitions in the rare earth metal erbium to 151 GPa.

    Science.gov (United States)

    Samudrala, Gopi K; Thomas, Sarah A; Montgomery, Jeffrey M; Vohra, Yogesh K

    2011-08-10

    High pressure x-ray diffraction studies have been performed on the heavy rare earth metal erbium (Er) in a diamond anvil cell at room temperature to a pressure of 151 GPa and Er has been compressed to 40% of its initial volume. The rare earth crystal structure sequence hcp → Sm type → dhcp → distorted fcc (hcp: hexagonal close packed; fcc: face centered cubic; dhcp: double hcp) is observed in Er below 58 GPa. We have carried out Rietveld refinement of crystal structures in the pressure range between 58 GPa and 151 GPa. We have examined various crystal structures that have been proposed for the distorted fcc (dfcc) phase and the post-dfcc phase in rare earth metals. We find that the hexagonal hR 24 structure is the best fit between 58 and 118 GPa. Above 118 GPa, a structural transformation from hR 24 phase to a monoclinic C 2/m phase is observed with a volume change of - 1.9%. We have also established a clear trend for the pressure at which a post-dfcc phase is formed in rare earth metals and show that there is a monotonic increase in this pressure with the filling of 4f shell.

  13. Phase Diagram for Ashkin-Teller Model on Bethe Lattice

    Institute of Scientific and Technical Information of China (English)

    LE Jian-Xin; YANG Zhan-Ru

    2005-01-01

    Using the recursion method, we study the phase transitions of the Ashkin-Teller model on the Bethe lattice,restricting ourselves to the case of ferromagnetic interactions. The isotropic Ashkin-Teller model and the anisotropic one are respectively investigated, and exact expressions for the free energy and the magnetization are obtained. It can be found that each of the three varieties of phase diagrams, for the anisotropic Ashkin-Teller model, consists of four phases, I.e., the fully disordered paramagnetic phase Para, the fully ordered ferromagnetic phase Ferro, and two partially ordered ferromagnetic phases and , while the phase diagram, for the isotropic Ashkin-Teller model,contains three phases, I.e., the fully disordered paramagnetic phase Para, the fully ordered ferromagnetic phase Baxter Phase, and the partially ordered ferromagnetic phase .

  14. In situ X-ray observation of phase transitions in ZnF2 under high pressure and high temperature

    Science.gov (United States)

    Kusaba, Keiji; Kikegawa, Takumi

    2008-02-01

    High-pressure and high-temperature behavior of ZnF 2 with the rutile-type structure was investigated using an energy-dispersive-type X-ray diffraction method. Two high-pressure phases were found in the range up to 15 GPa and 400 ∘C. The CaCl 2-type phase with an orthorhombic cell (space group: Pnnm) was clearly observed at 5.4 GPa and 400 ∘C. Further phase transition was induced above 10 GPa at room temperature. The single phase of the high-pressure phase was obtained at 15.3 GPa and 350 ∘C. The high-pressure phase was found to have the PdF 2-type structure with a cubic cell (space group: Pa-3). The single phase was observed above 4 GPa in a pressure-release process at room temperature, and completely reverted to a mixture of the rutile-type phase and the α- PbO 2-type phase at ambient condition. The high-pressure behavior of ZnF 2 was similar to that of MgF 2.

  15. Phase transitions in Group III-V and II-VI semiconductors at high pressure

    Science.gov (United States)

    Yu, S. C.; Liu, C. Y.; Spain, I. L.; Skelton, E. F.

    1979-01-01

    The structures and transition pressures of Group III-V and II-VI semiconductors and of a pseudobinary system (Ga/x/In/1-x/Sb) have been investigated. Results indicate that GaP, InSb, GaSb, GaAs and possible AlP assume Metallic structures at high pressures; a tetragonal, beta-Sn-like structure is adopted by only InSb and GaSb. The rocksalt phase is preferred in InP, InAs, AlSb, ZnO and ZnS. The model of Van Vechten (1973) gives transition pressures which are in good agreement with measured values, but must be refined to account for the occurrence of the ionic rocksalt structure in some compounds. In addition, discrepancies between the theoretical scaling values for volume changes at the semiconductor-to-metal transitions are observed.

  16. Structural Phase Transformations of ZnS Nanocrystalline Under High Pressure

    Institute of Scientific and Technical Information of China (English)

    潘跃武; 曲胜春; 高春晓; 韩永昊; 骆继锋; 崔启良; 刘景; 邹广田

    2004-01-01

    In-situ energy dispersive x-ray diffraction on ZnS nanocrystalline was carried out under high pressure by using a diamond anvil cell. Phase transition of wurtzite of 10nm ZnS to rocksalt occurred at 16.0GPa, which was higher than that of the bulk materials. The structures of ZnS nanocrystalline at different pressures were built by using materials studio and the bulk modulus, and the pressure derivative of ZnS nanocrystalline were derived by fitting the equation of Birch-Murnaghan. The resulting modulus was higher than that of the corresponding bulk material, which indicates that the nanomaterial has higher hardness than its bulk materials.

  17. High-Pressure Phase Behavior of Polycaprolactone, Carbon Dioxide, and Dichloromethane Ternary Mixture Systems

    Energy Technology Data Exchange (ETDEWEB)

    Gwon, JungMin; Kim, Hwayong [Seoul National University, Seoul (Korea, Republic of); Shin, Hun Yong [Seoul National University of Science and Technology, Seoul (Korea, Republic of); Kim, Soo Hyun [Korea Institute of Science and Technology, Seoul (Korea, Republic of)

    2015-04-15

    The high-pressure phase behavior of a polycaprolactone (Mw=56,145 g/mol, polydispersity 1.2), dichloromethane, and carbon dioxide ternary system was measured using a variable-volume view cell. The experimental temperatures and pressures ranged from 313.15 K to 353.15 K and up to 300 bar as functions of the CO{sub 2}/dichloromethane mass ratio and temperature, at poly(D-lactic acid) weight fractions of 1.0, 2.0, and 3.0%. The correlation results were obtained from the hybrid equation of state (Peng-Robinson equation of state + SAFT equation of state) for the CO{sub 2}-polymer system using the van der Waals one-fluid mixing rule. The three binary interaction parameters were optimized by the simplex method algorithm.

  18. Phase Behaviour of the System Propene/Polypropene at High Pressure

    Directory of Open Access Journals (Sweden)

    Oliver Ruhl

    2011-01-01

    Full Text Available The phase behaviour of mixtures of supercritical propene and a number of polypropenes, which have a similar density but significantly different molecular weights and tacticities, was investigated in a broad range of polymer weight fractions and temperatures at high pressures. The cloud-point pressures were measured optically, using a view cell which was equipped with two windows made of synthetic sapphire and a metal bellows to accurately adjust the pressure. The cloud-point pressures were found in the range from 29 to 37 MPa decreasing with increasing polymer weight fraction and increasing with increasing temperature and polymer molecular weight. The critical weight fraction was found below 2 to 6 wt.-%. Whereas the cloud-point pressures of atactic and syndiotactic samples were high and very similar, the isotactic species exhibit distinctly lower values. The results, extrapolated to lower temperatures, show good agreement with the literature data.

  19. High pressure induced phase transition and superdiffusion in anomalous fluid confined in flexible nanopores

    Energy Technology Data Exchange (ETDEWEB)

    Bordin, José Rafael, E-mail: josebordin@unipampa.edu.br [Campus Caçapava do Sul, Universidade Federal do Pampa, Caixa Postal 15051, CEP 96570-000, Caçapava do Sul, RS (Brazil); Krott, Leandro B., E-mail: leandro.krott@ufrgs.br; Barbosa, Marcia C., E-mail: marcia.barbosa@ufrgs.br [Instituto de Física, Universidade Federal do Rio Grande do Sul, Caixa Postal 15051, CEP 91501-970, Porto Alegre, RS (Brazil)

    2014-10-14

    The behavior of a confined spherical symmetric anomalous fluid under high external pressure was studied with Molecular Dynamics simulations. The fluid is modeled by a core-softened potential with two characteristic length scales, which in bulk reproduces the dynamical, thermodynamical, and structural anomalous behavior observed for water and other anomalous fluids. Our findings show that this system has a superdiffusion regime for sufficient high pressure and low temperature. As well, our results indicate that this superdiffusive regime is strongly related with the fluid structural properties and the superdiffusion to diffusion transition is a first order phase transition. We show how the simulation time and statistics are important to obtain the correct dynamical behavior of the confined fluid. Our results are discussed on the basis of the two length scales.

  20. PHASE TRANSITION IN LAYERED PEROVSKITE LIKE MANGANATE Ca3Mn2O7 UNDER HIGH PRESSURE

    Institute of Scientific and Technical Information of China (English)

    J.L.ZHU; L.C.CHEN; R.C.YU; F.Y.LI; J.LIU; C.Q.JIN

    2001-01-01

    In situ high pressure energy dispersive X-ray diffraction measurements on layered perovskite-like manganate Ca3Mn2O7 under pressures up to 35 GPa have been Performed by using diamond anvil cell with synchrotron radiation.The results show that the structure of layered perovskite-like manganate Ca3Mn2O7 is unstable under pressure due to the easy compression of NaCl-type blocks.The structure of Ca3Mn2O7 underwent two phase transitions under pressures in the range of 0-35GPa.One was at about 1.3GPa with the crystal structure changing from tetragonalt go orthorhombic.The other was at about 9.5GPa with the crystal structure changing form orthorhombic back to another tetragonal.

  1. Atomic ordering in cubic bismuth telluride alloy phases at high pressure

    Science.gov (United States)

    Loa, I.; Bos, J.-W. G.; Downie, R. A.; Syassen, K.

    2016-06-01

    Pressure-induced transitions from ordered intermetallic phases to substitutional alloys to semi-ordered phases were studied in a series of bismuth tellurides. By using angle-dispersive x-ray diffraction, the compounds Bi4Te5 , BiTe, and Bi2Te were observed to form alloys with the disordered body-centered cubic (bcc) crystal structure upon compression to above 14-19 GPa at room temperature. The BiTe and Bi2Te alloys and the previously discovered high-pressure alloys of Bi2Te3 and Bi4Te3 were all found to show atomic ordering after gentle annealing at very moderate temperatures of ˜100 ∘C . Upon annealing, BiTe transforms from bcc to the B2 (CsCl) crystal-structure type, and the other phases adopt semi-disordered variants thereof, featuring substitutional disorder on one of the two crystallographic sites. The transition pressures and atomic volumes of the alloy phases show systematic variations across the BimTen series including the end members Bi and Te. First-principles calculations were performed to characterize the electronic structure and chemical bonding properties of B2-type BiTe and to identify the driving forces of the ordering transition. The calculated Fermi surface of B2-type BiTe has an intricate structure and is predicted to undergo three topological changes between 20 and 60 GPa.

  2. Phase diagram for a nano-yttria-stabilized zirconia system

    DEFF Research Database (Denmark)

    Asadikiya, Mohammad; Sabarou, Hooman; Chen, Ming;

    2016-01-01

    Due to the attractive properties of nanoparticles because of their effective surface area, they have been studied widely. Nano-yttria-stabilized zirconia (n-YSZ) is a ceramic which has been scrutinized extensively in past years. Because of the different stability behavior of n-YSZ in comparison...... with bulk YSZ, a new phase diagram is needed for the n-YSZ system in order to identify stable phases under various conditions. In this study, a phase diagram for the n-YSZ system was provided to determine phase stability ranges at room temperature with respect to particle size and composition....... By applying the CALPHAD approach, a 3-D phase diagram for the n-YSZ system was established in which the stability range of each individual phase can be predicted based on the particle size, composition, and temperature....

  3. Infrared thermography method for fast estimation of phase diagrams

    Energy Technology Data Exchange (ETDEWEB)

    Palomo Del Barrio, Elena [Université de Bordeaux, Institut de Mécanique et d’Ingénierie, Esplanade des Arts et Métiers, 33405 Talence (France); Cadoret, Régis [Centre National de la Recherche Scientifique, Institut de Mécanique et d’Ingénierie, Esplanade des Arts et Métiers, 33405 Talence (France); Daranlot, Julien [Solvay, Laboratoire du Futur, 178 Av du Dr Schweitzer, 33608 Pessac (France); Achchaq, Fouzia, E-mail: fouzia.achchaq@u-bordeaux.fr [Université de Bordeaux, Institut de Mécanique et d’Ingénierie, Esplanade des Arts et Métiers, 33405 Talence (France)

    2016-02-10

    Highlights: • Infrared thermography is proposed to determine phase diagrams in record time. • Phase boundaries are detected by means of emissivity changes during heating. • Transition lines are identified by using Singular Value Decomposition techniques. • Different binary systems have been used for validation purposes. - Abstract: Phase change materials (PCM) are widely used today in thermal energy storage applications. Pure PCMs are rarely used because of non adapted melting points. Instead of them, mixtures are preferred. The search of suitable mixtures, preferably eutectics, is often a tedious and time consuming task which requires the determination of phase diagrams. In order to accelerate this screening step, a new method for estimating phase diagrams in record time (1–3 h) has been established and validated. A sample composed by small droplets of mixtures with different compositions (as many as necessary to have a good coverage of the phase diagram) deposited on a flat substrate is first prepared and cooled down to ambient temperature so that all droplets crystallize. The plate is then heated at constant heating rate up to a sufficiently high temperature for melting all the small crystals. The heating process is imaged by using an infrared camera. An appropriate method based on singular values decomposition technique has been developed to analyze the recorded images and to determine the transition lines of the phase diagram. The method has been applied to determine several simple eutectic phase diagrams and the reached results have been validated by comparison with the phase diagrams obtained by Differential Scanning Calorimeter measurements and by thermodynamic modelling.

  4. Revised Phase Diagram of the Gross-Neveu Model

    CERN Document Server

    Thies, M; Thies, Michael; Urlichs, Konrad

    2003-01-01

    We confirm earlier hints that the conventional phase diagram of the discrete chiral Gross-Neveu model in the large N limit is deficient at non-zero chemical potential. We present the corrected phase diagram constructed in mean field theory. It has three different phases, including a kink-antikink crystal phase. All transitions are second order. The driving mechanism for the new structure of baryonic matter in the Gross-Neveu model is an Overhauser type instability with gap formation at the Fermi surface.

  5. A Finite Temperature Phase Diagram in Rotating Bosonic Optical Lattices

    Institute of Scientific and Technical Information of China (English)

    HUANG Bei-Bing; WAN Shao-Long

    2011-01-01

    A finite temperature phase diagram of the rotating Bose-Hubbard model, including the crossover between Mott insulator and the normal state, is derived on the frame of the Gutzwiller mean-field theory. In addition, we calculate the critical temperature of superBuid-normal phase transition.%@@ A finite temperature phase diagram of the rotating Bose-Hubbard model, including the crossover between Mort insulator and the normal state, is derived on the frame of the Gutzwiller mean-field theory.In addition, we calculate the critical temperature of superfluid-normal phase transition.

  6. Interacting Weyl fermions: Phases, phase transitions, and global phase diagram

    Science.gov (United States)

    Roy, Bitan; Goswami, Pallab; Juričić, Vladimir

    2017-05-01

    We study the effects of short-range interactions on a generalized three-dimensional Weyl semimetal, where the band touching points act as the (anti)monopoles of Abelian Berry curvature of strength n . We show that any local interaction has a negative scaling dimension -2 /n . Consequently, all Weyl semimetals are stable against weak short-range interactions. For sufficiently strong interactions, we demonstrate that the Weyl semimetal either undergoes a first-order transition into a band insulator or a continuous transition into a symmetry breaking phase. A translational symmetry breaking axion insulator and a rotational symmetry breaking semimetal are two prominent candidates for the broken symmetry phase. At the one-loop order, the correlation length exponent for continuous transitions is ν =n /2 , indicating their non-Gaussian nature for any n >1 . We also discuss the scaling of the thermodynamic and transport quantities in general Weyl semimetals as well as inside broken symmetry phases.

  7. High-pressure phase transitions in the rare-earth orthoferrite LaFeO3.

    Science.gov (United States)

    Etter, Martin; Müller, Melanie; Hanfland, Michael; Dinnebier, Robert E

    2014-06-01

    Sequential Rietveld refinements were applied on high-pressure synchrotron powder X-ray diffraction measurements of lanthanum ferrite (LaFeO3) revealing two phase transitions on the room-temperature isotherm up to a pressure of 48 GPa. The first structural phase transition of second order occurs at a pressure of 21.1 GPa, changing the space group from Pbnm to Ibmm. The second transition, involving a isostructural first-order phase transition, occurs at approximately 38 GPa, indicating a high-spin to low-spin transition of the Fe(3+) ion. Following the behavior of the volume up to the hydrostatic limit of methanol-ethanol it was possible to use inverted equations of state (EoS) to determine a bulk modulus of B0 = 172 GPa and a corresponding pressure derivative of B'0 = 4.3. In addition, the linearized version of the inverted EoS were used to determine the corresponding moduli and pressure derivatives for each lattice direction.

  8. Phase diagram studies on the Na-Mo-O system

    Science.gov (United States)

    Gnanasekaran, T.; Mahendran, K. H.; Kutty, K. V. G.; Mathews, C. K.

    1989-06-01

    The phase diagram of the Na-Mo-O ternary system is of interest in interpreting the behaviour of structural materials in the sodium circuits of fast breeder reactors and sodium-filled heat pipes. Experiments involving heating of sodium oxide with molybdenum metal under vacuum, selective removal of oxygen from polymolybdates by reducing them under hydrogen and confirmation of the coexistence of various phase mixtures were conducted in the temperature range of 673 to 923 K. Phase fields involving molybdenum metal, dioxide of molybdenum and ternary compounds were derived from these results. The ternary phase diagram of the Na-Mo-O system was constructed and isothermal cross sections of the phase diagram are presented.

  9. High-pressure phase diagrams of methane + squalane and methane + hexatriacontane mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Marteau, P.; Tobaly, P. [CNRS, Villetaneuse (France). Lab. d`Ingenierie des Materiaux et des Hautes Pressions; Ruffier-Meray, V.; Hemptinne, J.C. de [Institut Francais du Petrole, Rueil-Malmaison (France)

    1998-05-01

    Thermodynamic properties of crude oils and natural gases are important for optimizing operating conditions. Equilibrium data on the methane + hexatriacontane mixture at (373, 398, 423, and 453) K and on the methane + squalane (2,6,10,15,19,23-hexamethyltetracosane) mixture at (323, 370, 420) K are reported. The apparatus and the near-infrared absorption method have been previously described.

  10. Synthesis, structural characterization and high pressure phase transitions of monolithium hydronium sulfate

    Energy Technology Data Exchange (ETDEWEB)

    Banerjee, Debasis, E-mail: debasis.banerjee@stonybrook.edu [Department of Chemistry, Stony Brook University, Stony Brook 11794-3400 (United States); Plonka, Anna M. [Department of Geosciences, Stony Brook University, Stony Brook 11794-2100 (United States); Kim, Sun Jin [Nano-Materials Research Center, Korea Institute of Science and Technology, P.O. Box 131, Cheongryang, Seoul 130-650 (Korea, Republic of); Xu Wenqian [Department of Geosciences, Stony Brook University, Stony Brook 11794-2100 (United States); Parise, John B. [Department of Chemistry, Stony Brook University, Stony Brook 11794-3400 (United States); Mineral Physics Institute, Stony Brook University, Stony Brook, NY 11790-2100 (United States)

    2013-01-15

    A three dimensional lithium hydronium sulfate LiSO{sub 4}{center_dot}H{sub 3}O [1], [space group Pna2{sub 1}a=8.7785(12) A, b=9.1297(12) A, c=5.2799(7) A, V=423.16(10) A{sup 3}] was synthesized via solvothermal methods using 1,5-naphthalenedisulfonic acid (1,5-NSA) as the source of sulfate ions. The structure of [1], determined by single crystal X-ray diffraction techniques, consists of corner sharing LiO{sub 4} and SO{sub 4} tetrahedra, forming an anionic 3-D open framework that is charge balanced by hydronium ions positioned within channels running along [001] and forming strong H-bonding with the framework oxygen atoms. Compound [1] undergoes two reversible phase transitions, involving reorientation of SO{sub 4}{sup 2-} ions at pressures of approximately 2.5 and 5 GPa at room temperature, as evident from characteristic discontinuous frequency drops in the {nu}{sub 1} mode of the Raman spectra. Additionally, compound [1] forms dense {beta}-lithium sulfate at 300 Degree-Sign C, as evident from temperature dependent powder XRD and combined reversible TGA-DSC experiments. - Graphical abstract: Left: View of corner-shared LiO{sub 4} and SO{sub 4} tetrahedra along [001] direction with hydronium ions situated in the channels. Right: (a) Photograph of the loaded DAC (b) Ambient pressure Raman spectrum of compound [1] (c) Evolution of the {nu}{sub 1} mode with the increasing and decreasing pressure indicating transitions to high-pressure phases at {approx}2.5 (red curves) and {approx}5 GPa (blue curves) and at {approx}3.5 GPa upon decompression. Highlights: Black-Right-Pointing-Pointer A 3-D lithium hydronium sulfate is synthesized by solvothermal methods. Black-Right-Pointing-Pointer Two high pressure phase transition occurs due to rotation of sulfate groups. Black-Right-Pointing-Pointer The framework undergoes a high temperature structural transformation, to form {beta}-Li{sub 2}SO{sub 4} phase.

  11. Ab initio molecular crystal structures, spectra, and phase diagrams.

    Science.gov (United States)

    Hirata, So; Gilliard, Kandis; He, Xiao; Li, Jinjin; Sode, Olaseni

    2014-09-16

    illustrations of their unprecedented power in addressing some of the outstanding problems of solid-state chemistry, high-pressure chemistry, or geochemistry. They are the structure and spectra of ice Ih, in particular, the origin of two peaks in the hydrogen-bond-stretching region of its inelastic neutron scattering spectra, a solid-solid phase transition from CO2-I to elusive, metastable CO2-III, pressure tuning of Fermi resonance in solid CO2, and the structure and spectra of solid formic acid, all at the level of second-order Møller-Plesset perturbation theory or higher.

  12. Interacting Weyl fermions: Phases, phase transitions and global phase diagram

    CERN Document Server

    Roy, Bitan; Juricic, Vladimir

    2016-01-01

    We study the effects of short-range interactions on a generalized three-dimensional Weyl semimetal, where the band touching points act as the (anti)monopoles of Abelian Berry curvature of strength $n$. We show that any local interaction has a \\emph{negative} scaling dimension $-2/n$. Consequently all Weyl semimetals are stable against weak short-range interactions. For sufficiently strong interactions, we demonstrate that the Weyl semimetal either undergoes a first order transition into a band insulator or a continuous transition into a symmetry breaking phase. A translational symmetry breaking axion insulator and a rotational symmetry breaking semimetal are two prominent candidates for the broken symmetry phase. At one loop level, the correlation length exponent for continuous transitions is $\

  13. High-pressure differential thermal analysis (DTA) of the phase behaviors of didodecyl-dimethylammoniumbromide (DDAB) and ditetradecyl-dimethylammoniumbromide (DTAB)

    Science.gov (United States)

    Hamann, F.; Reuter, John; Wuerflinger, A.; Godlewska, Malgorzata; Dynarowicz, Patrycja

    1998-01-01

    Dialkyldimethylammonium halides are known for their applications as commercial detergents and for their membrane-mimetic properties. They display both thermotropic and lyotropic liquid crystalline properties. In this work we establish the T(p)-phase diagrams of two representatives, namely didodecyl- and ditetradecyl-ammonium bromides. The transitions between crystal, smectic Ii and smectic I phases were recorded using a high-pressure differential thermal analysis device. For both compounds the stable range of smectic II phase is pressure-limited, resulting in a triple point crystal/smectic II/smectic I. Enthalpy changes at ambient pressure have been determined with the aid of a commercial heat flux differential scanning calorimeter. Volume changes were calculated from the slopes of the transitions lines, employing the Clausius Clapeyron equation.

  14. Metastable Al-Sc phase diagram in aluminium rich region

    Energy Technology Data Exchange (ETDEWEB)

    Drits, M.E.; Toropova, L.S.; Bykov, Yu.G.; Gushchina, F.L.; Elagin, V.I.; Filatov, Yu.A.

    1982-12-01

    An aluminium rich part of binary metastable phase diagram Al-Sc for 100 deg/s alloy cooling rate under crystallization is studied. Eutectic horizontal in the metastable diagram is 4 deg lower as compared to the equilibrium one, scandium concentration in the eutectic point makes up approximately 0.8%, the maximum solubility is 0.6%. Maximum cast grain refining in aluminium under crystallization at the rate of 100 deg/s is attained at 0.6% scandium content.

  15. Ternary phase diagram calculations of pentaerythritol-pentaglycerine-neopentylglycol system

    Energy Technology Data Exchange (ETDEWEB)

    Mishra, A.; Talekar, A. [Chemical and Materials Engineering Department (MS388), University of Nevada, Reno, NV 89557 (United States); Chandra, D., E-mail: dchandra@unr.edu [Chemical and Materials Engineering Department (MS388), University of Nevada, Reno, NV 89557 (United States); Chien, W.-M. [Chemical and Materials Engineering Department (MS388), University of Nevada, Reno, NV 89557 (United States)

    2012-05-10

    Highlights: Black-Right-Pointing-Pointer Ternary phase diagrams of polyalcohols are developed using the CALPHAD method. Black-Right-Pointing-Pointer These ternary phase diagrams are thermodynamically calculated for the first time. Black-Right-Pointing-Pointer Orientational disorder is observed in the high temperature (energy storage) phase. Black-Right-Pointing-Pointer Polyalcohols are potential thermal energy storage materials. - Abstract: The pentaerythritol (PE)-pentaglycerine (PG)-neopentylglycol (NPG) ternary system has been thermodynamically assessed using the CALPHAD method and Thermo-Calc software. The PE-PG, PG-NPG, PE-NPG binary systems have also been calculated using CALPHAD on the basis of reported binary experimental data. The solution phases are modeled as substitutional solutions, in which the excess Gibbs energies are expressed by the Redlich-Kister-Muggianu polynomial. The PE-NPG binary phase diagram was modeled using Henrian solution model, and the liquid phase was assumed ideal. The PG-NPG system was optimized using regular and sub-regular solution models and show invariant equilibria at 298 K. The PE-NPG binary system was calculated from room temperature to the liquid phase temperatures. The modeled phase diagrams and the experimental data are in good agreement. A set of self consistent thermodynamic parameters formulating the Gibbs energies of various phases in the PE-PG-NPG ternary system are obtained in the present work. Thermodynamic properties, several vertical and isopleth sections have been calculated and are in good agreement with experimental data.

  16. Kinematics and thermodynamics of a growing rim of high-pressure phase

    Science.gov (United States)

    Morris, S. J. S.

    2014-03-01

    We have reanalysed the problem of growth of a dense product rim on a sphere of parent phase. To decouple the problem of calculating deformation from rheology, we assume spherical symmetry, and incompressible phases. Within the product, the radial deviatoric strain and its time-derivative prove to be of opposite sign: strain is compressive, but the strain rate is tensile. Further, the radial deviatoric strain in the new product adjacent to the interface is invariant in time. Propagation of the phase interface is determined by a competition between two mechanisms: as an element of material is transformed, its shear strain energy is increased; and the core pressure performs work compressing it. For elastic phases, this competition results in metastability. Within a certain pressure range, either phase can occur alone, but the two phases can not coexist. Because this result is inconsistent with experiments by Kawazoe et al. (2010) in which a rim of high-pressure phase (wadsleyite) coexists with a central core of low-pressure phase (olivine), we then incorporate plastic flow. Assuming perfect plasticity, we show that for a given applied pressure exceeding the coexistence pressure, a rim of product can now nucleate if the excess pressure Δp exceeds a critical value depending on yield stress. Increasing Δp above this value allows product to grow into the parent phase. There are now two possibilities, depending on the value of Δp. Growth may eventually cease to produce a state in which the product rim is in equilibrium with a parent core; or growth may follow a more complicated path: within a range of excess pressures, the growth rate can decrease strongly from its initial value to produce a quasi-equilibrium state, before increasing again to a rate similar to that at which transformation began. We interpret these results to mean that if Δp is increased slowly in a series of experiments with constant yield stress, the sample passes through a series of equilibria until

  17. Phase diagrams and synthesis of cubic boron nitride

    CERN Document Server

    Turkevich, V Z

    2002-01-01

    On the basis of phase equilibria, the lowest temperatures, T sub m sub i sub n , above which at high pressures cubic boron nitride crystallization from melt solution is allowable in terms of thermodynamics have been found for a number of systems that include boron nitride.

  18. Incommensurate atomic density waves in the high-pressure IVb phase of barium

    Directory of Open Access Journals (Sweden)

    Alla Arakcheeva

    2017-03-01

    Full Text Available The host–guest structures of elements at high pressure discovered a decade ago still leave many open questions due to the lack of precise models based on full exploitation of the diffraction data. This concerns in particular Ba IV, which is stable in the range 12–45 GPa. With the example of phase Ba IVb, which is characterized here for the first time, a systematic analysis is presented of possible host–guest structure models based on high-quality single-crystal diffraction data obtained with synchrotron radiation at six different pressures between 16.5 and 19.6 GPa. It is shown that a new incommensurately modulated (IM structure model better fits the experimental data. Unlike the composite models which are commonly reported for the Ba IV phases, the IM model reveals a density wave and its pressure-dependent evolution. The crucial role played by the selected model in the interpretation of structure evolution under pressure is discussed. The findings give a new experimental basis for a better understanding of the nature of host–guest structures.

  19. The role of equilibrium volume and magnetism on the stability of iron phases at high pressures.

    Science.gov (United States)

    Alnemrat, S; Hooper, J P; Vasiliev, I; Kiefer, B

    2014-01-29

    The present study provides new insights into the pressure dependence of magnetism by tracking the hybridization between crystal orbitals for pressures up to 600 GPa in the known hcp, bcc and fcc iron. The Birch-Murnaghan equation of state parameters are; bcc: V0 = 11.759 A(3)/atom, K0 = 177.72 GPa; hcp: V0 = 10.525 A(3)/atom, K0 = 295.16 GPa; and fcc: V0 = 10.682 A(3)/atom, K0 = 274.57 GPa. These parameters compare favorably with previous studies. Consistent with previous studies we find that the close-packed hcp and fcc phases are non-magnetic at pressures above 50 GPa and 60 GPa, respectively. The principal features of magnetism in iron are predicted to be invariant, at least up to ∼6% overextension of the equilibrium volume. Our results predict that magnetism for overextended fcc iron disappears via an intermediate spin state. This feature suggests that overextended lattices can be used to stabilize particular magnetic states. The analysis of the orbital hybridization shows that the magnetic bcc structure at high pressures is stabilized by splitting the majority and minority spin bands. The bcc phase is found to be magnetic at least up to 600 GPa; however, magnetism is insufficient to stabilize the bcc phase itself, at least at low temperatures. Finally, the analysis of the orbital contributions to the total energy provides evidence that non-magnetic hcp and fcc phases are likely more stable than bcc at core earth pressures.

  20. High pressure monoclinic phases of Sb{sub 2}Te{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Souza, S.M.; Poffo, C.M.; Triches, D.M. [Departamento de Engenharia Mecanica, Universidade Federal de Santa Catarina, Campus Universitario Trindade, S/N, C.P. 476, 88040-900 Florianopolis, Santa Catarina (Brazil); Lima, J.C. de, E-mail: fsc1jcd@fisica.ufsc.br [Departamento de Fisica, Universidade Federal de Santa Catarina, Campus Universitario Trindade, S/N, C.P. 476, 88040-900 Florianopolis, Santa Catarina (Brazil); Grandi, T.A. [Departamento de Fisica, Universidade Federal de Santa Catarina, Campus Universitario Trindade, S/N, C.P. 476, 88040-900 Florianopolis, Santa Catarina (Brazil); Polian, A.; Gauthier, M. [Physique des Milieux Denses, IMPMC, CNRS-UMR 7590, Universite Pierre et Marie Curie-Paris 6, 4 Place Jussieu, 75252 Paris Cedex 05 (France)

    2012-09-15

    The effect of pressure on nanostructured rhombohedral {alpha}-Sb{sub 2}Te{sub 3} (phase I) was investigated using X-ray diffraction (XRD) and Raman spectroscopy (RS) up to 19.2 and 25.5 GPa, respectively. XRD patterns showed two new high pressure phases (named phases II and III). From a Rietveld refinement of XRD patterns of {alpha}-Sb{sub 2}Te{sub 3}, the unit cell volume as a function of pressure was obtained and the values were fitted to a Birch-Murnaghan equation of state (BM-EOS). The best fit was obtained for bulk modulus B{sub 0}=36.1{+-}0.9 GPa and its derivative B{sub 0}{sup Prime }=6.2{+-}0.4 (not fixed). Using the refined structural data for {alpha}-Sb{sub 2}Te{sub 3}, for pressures up to 9.8 GPa, changes in the angle of succession [Te-Sb-Te-Sb-Te], in the interaromic distances of Sb and Te atoms belonging to this angle of succession and in the interatomic distances of atoms located on the c axis were examined. This analysis revealed an electronic topological transition (ETT) along the a and c axes at close to 3.7 GPa. From the RS spectra, the full widths at half maximum (FWHM) of the Raman active modes of {alpha}-Sb{sub 2}Te{sub 3} were plotted as functions of pressure and showed an ETT along the a and c axes at close to 3.2 GPa. The XRD patterns of phases II and III were well reproduced assuming {beta}-Bi{sub 2}Te{sub 3} and {gamma}-Bi{sub 2}Te{sub 3} structures similar to those reported in the literature for {alpha}-Bi{sub 2}Te{sub 3}.

  1. Synthesis of Dense BC3 Phases under High-Pressure and High-Temperature

    Science.gov (United States)

    Zinin, P.; Ming, L.; Acosta, T.; Jia, R.; Hellebrand, E.; Ishii, H.

    2010-12-01

    The finding of the new diamond-like B-C phases is of fundamental importance. These phases are potential high-temperature superconductors and their development is important for understanding the nature of high-temperature superconductivity (Moussa, Cohen, Phys. Rev. B, 77, 064518 2008). They will shed light on the nature of the bonding of the boron atoms in a diamond-like structure. Recently, theoretical simulations of pressure- and temperature-induced phase transition in the B-C system demonstrated that the incorporation of B atoms into a diamond structure should not lead to a drastic distortion of the cubic cell of a diamond (Lowther, J. Phys. Condense Matter. 17, 3221, 2005). In this report we present data on the synthesis of new dense phases cubic BC3 (c-BC3) phase from graphitic BC3 phase (g-BC3) phase under high pressure and high temperature. Two graphitic polycrystalline BCx samples were compressed in a diamond-anvil cell to about 24 GPa and 45 GPa, respectively, and then were laser-heated to ~2000 K. After quenching, each sample was decompressed gradually stepwise to the atmospheric pressure. Synchrotron-based X-ray diffraction patterns were taken before and after the laser-heating, and also at each pressure step-down. The experimental data showed that two new phases were synthesized: (a) an orthorhombic phase with a0 = 3.74 Å, b0 = 3.24 Å, c0=4.25 Å; and (b) a cubic phase with a0 = 3.587Å recovered from 24 GPa and 44 GPa, respectively. The zero-pressure lattice parameter of the cubic phase obtained in this study is larger than that of diamond (i.e., a0=3.5667 Å, ASTM # 6-0675), which is consistent with theoretical prediction The micro-Raman measurements were directly performed on the new phases. The Raman spectra excited by a green (Nd-YAG, 532-nm) laser were taken with a confocal Raman system (WiTec alpha300). The Raman spectrum of the c-BC3 phase is similar to that of diamond-like BC3 phase (Zinin et al., J. Raman Spectrosc., 38, 1362, 2007) with a

  2. Phase diagrams for geoscientists an atlas of the Earth's interior

    CERN Document Server

    Gasparik, Tibor

    2014-01-01

    Presented in this new, full-color edition, with the first polychrome phase diagrams to be published, this geoscientific atlas is backed by the author's unrivalled dataset, and amounts to the most complete survey yet of phase relations in Earth's chemistry.

  3. Enhanced superconductivity in the high pressure phase of SnAs studied from first principles

    Science.gov (United States)

    Sreenivasa Reddy, P. V.; Kanchana, V.; Millichamp, T. E.; Vaitheeswaran, G.; Dugdale, S. B.

    2017-01-01

    First principles calculations are performed using density functional theory and density functional perturbation theory for SnAs. Total energy calculations show the first order phase transition from an NaCl structure to a CsCl one at around 37 GPa, which is also confirmed from enthalpy calculations and agrees well with experimental work. Calculations of the phonon structure and hence the electron-phonon coupling, λep, and superconducting transition temperature, Tc, across the phase diagram are performed. These calculations give an ambient pressure Tc, in the NaCl structure, of 3.08 K, in good agreement with experiment whilst at the transition pressure, in the CsCl structure, a drastically increased value of Tc = 12.2 K is found. Calculations also show a dramatic increase in the electronic density of states at this pressure. The lowest energy acoustic phonon branch in each structure also demonstrates some softening effects. Electronic structure calculations of the Fermi surface in both phases are presented for the first time as well as further calculations of the generalised susceptibility with the inclusion of matrix elements. These calculations indicate that the softening is not derived from Fermi surface nesting and it is concluded to be due to a wavevector-dependent enhancement of the electron-phonon coupling.

  4. Development and testing of a new apparatus for the measurement of high-pressure low-temperature phase equilibria

    DEFF Research Database (Denmark)

    Fonseca, José M.S.; von Solms, Nicolas

    2012-01-01

    A new apparatus for the study of high-pressure phase equilibria at low temperatures using an analytical method was designed, assembled and tested. The apparatus was specially developed for the study of multi-phase equilibria in systems containing hydrocarbons, water and hydrate inhibitors...

  5. Monte-Carlo study of Dirac semimetals phase diagram

    CERN Document Server

    Braguta, V V; Kotov, A Yu; Nikolaev, A A

    2016-01-01

    In this paper the phase diagram of Dirac semimetals is studied within lattice Monte-Carlo simulation. In particular, we concentrate on the dynamical chiral symmetry breaking which results in semimetal/insulator transition. Using numerical simulation we determined the values of the critical coupling constant of the semimetal/insulator transition for different values of the anisotropy of the Fermi velocity. This measurement allowed us to draw tentative phase diagram for Dirac semimetals. It turns out that within the Dirac model with Coulomb interaction both Na$_3$Bi and Cd$_3$As$_2$ known experimentally to be Dirac semimetals would lie deeply in the insulating region of the phase diagram. It probably shows a decisive role of screening of the interelectron interaction in real materials, similar to the situation in graphene.

  6. Monte Carlo study of Dirac semimetals phase diagram

    Science.gov (United States)

    Braguta, V. V.; Katsnelson, M. I.; Kotov, A. Yu.; Nikolaev, A. A.

    2016-11-01

    In this paper the phase diagram of Dirac semimetals is studied within a lattice Monte Carlo simulation. In particular, we concentrate on the dynamical chiral symmetry breaking which results in a semimetal-insulator transition. Using numerical simulation, we determine the values of the critical coupling constant of the semimetal-insulator transition for different values of the anisotropy of the Fermi velocity. This measurement allows us to draw a tentative phase diagram for Dirac semimetals. It turns out that within the Dirac model with Coulomb interaction both Na3Bi and Cd3As2 , known experimentally to be Dirac semimetals, would lie deep in the insulating region of the phase diagram. This result probably shows a decisive role of screening of the interelectron interaction in real materials, similar to the situation in graphene.

  7. Structures and phase transitions of ScH3 under high pressure

    Institute of Scientific and Technical Information of China (English)

    Kong Bo; Zhou Zhu-Wen; Chen De-Liang; Ling-hu Rong-Feng

    2013-01-01

    The structures and the phase transitions of ScH3 under high pressure are investigated using first-principles calculations.The calculated structural parameters at zero pressure agree well with the available experimental data.With increasing pressure,the transition sequence hcp (GdH3-type)→ C2/m →fcc→hcp (YH3-type)→Cmcm of ScH3 is predicted first; the corresponding transition pressures at 0 K are 23 GPa,25 GPa,348 GPa,and 477 GPa,respectively.The C2/m symmetry structure is a possible candidate but not a good one as the intermediate state from hexagonal to cubic in ScH3.On the other hand,via the analysis of the structures of hexagonal ScH2.9,cubic ScH3,and cubic ScH2,we find that the repulsive interactions of H-H atoms must play an important role in the transition from hexagonal to cubic.

  8. Extraction of Lipids from Chlorella saccharophila Using High-Pressure Homogenization Followed by Three Phase Partitioning.

    Science.gov (United States)

    Mulchandani, Ketan; Kar, Jayaranjan R; Singhal, Rekha S

    2015-07-01

    Commercial exploitation of microalgae for biofuel and food ingredients is hindered due to laborious extraction protocols and use of hazardous chemicals. Production of lipids in the microalga grown in modified BG11 medium was evaluated to arrive at the appropriate harvesting conditions. The use of three phase partitioning (TPP) as a green approach for extraction of lipids from Chlorella saccharophila was investigated. Cells disrupted by probe sonication were used for separation of lipids by TPP. The TPP-optimized conditions of 30 % ammonium sulfate, using slurry/t-butanol of 1:0.75 for 60 min at 25 to 35 °C, showed a lipid recovery of 69.05 ± 3.12 % (w/w) as against 100 % (w/w) by using chloroform-methanol extraction. Subsequently, parameters of high-pressure homogenization for cell disruption were optimized for maximum recovery of lipids by TPP. A final recovery of 89.91 ± 3.69 % (w/w) lipids was obtained along with ∼1.26 % w/w carotenoids of dry biomass in the t-butanol layer and protein content of ∼12 % w/w of dry biomass in the middle protein layer due to ammonium sulfate precipitation, after performing TPP under the optimized conditions.

  9. Mirrored continuum and molecular scale simulations of the ignition of high-pressure phases of RDX

    Science.gov (United States)

    Lee, Kibaek; Joshi, Kaushik; Chaudhuri, Santanu; Stewart, D. Scott

    2016-05-01

    We present a mirrored atomistic and continuum framework that is used to describe the ignition of energetic materials, and a high-pressure phase of RDX in particular. The continuum formulation uses meaningful averages of thermodynamic properties obtained from the atomistic simulation and a simplification of enormously complex reaction kinetics. In particular, components are identified based on molecular weight bin averages and our methodology assumes that both the averaged atomistic and continuum simulations are represented on the same time and length scales. The atomistic simulations of thermally initiated ignition of RDX are performed using reactive molecular dynamics (RMD). The continuum model is based on multi-component thermodynamics and uses a kinetics scheme that describes observed chemical changes of the averaged atomistic simulations. Thus the mirrored continuum simulations mimic the rapid change in pressure, temperature, and average molecular weight of species in the reactive mixture. This mirroring enables a new technique to simplify the chemistry obtained from reactive MD simulations while retaining the observed features and spatial and temporal scales from both the RMD and continuum model. The primary benefit of this approach is a potentially powerful, but familiar way to interpret the atomistic simulations and understand the chemical events and reaction rates. The approach is quite general and thus can provide a way to model chemistry based on atomistic simulations and extend the reach of those simulations.

  10. Synthesis of novel deuterides in several Laves phases by using gaseous deuterium under high pressure

    CERN Document Server

    Filipek, S M; Jacob, I; Marchuk, I; Dorogova, M; Hirata, T; Kaszkur, Z

    2002-01-01

    New deuterides of Laves phases: ErFe sub 2 D sub 5 , YFe sub 2 D sub 5 , ZrFe sub 2 D sub 3 sub . sub 5 and ZrCo sub 2 D sub 2 , have been obtained by using of gaseous deuterium at high pressure. A new orthorhombic structure was found for ErFe sub 2 D sub 5 and YFe sub 2 D sub 5 , while ZrFe sub 2 D sub 3 sub . sub 5 and ZrCo sub 2 D sub 2 were formed with a large expansion of the initial C15 cubic lattice. Formation of hydrides with high hydrogen concentration substantially changes the magnetic properties of ErFe sub 2 and YFe sub 2 but has no significant influence on the magnetization of ZrFe sub 2. The possibility of the formation of new deuterides (hydrides) in ZrCr sub 2 and YMn sub 2 has also been confirmed.

  11. High-Pressure Acceleration of Nanoliter Droplets in the Gas Phase in a Microchannel

    Directory of Open Access Journals (Sweden)

    Yutaka Kazoe

    2016-08-01

    Full Text Available Microfluidics has been used to perform various chemical operations for pL–nL volumes of samples, such as mixing, reaction and separation, by exploiting diffusion, viscous forces, and surface tension, which are dominant in spaces with dimensions on the micrometer scale. To further develop this field, we previously developed a novel microfluidic device, termed a microdroplet collider, which exploits spatially and temporally localized kinetic energy. This device accelerates a microdroplet in the gas phase along a microchannel until it collides with a target. We demonstrated 6000-fold faster mixing compared to mixing by diffusion; however, the droplet acceleration was not optimized, because the experiments were conducted for only one droplet size and at pressures in the 10–100 kPa range. In this study, we investigated the acceleration of a microdroplet using a high-pressure (MPa control system, in order to achieve higher acceleration and kinetic energy. The motion of the nL droplet was observed using a high-speed complementary metal oxide semiconductor (CMOS camera. A maximum droplet velocity of ~5 m/s was achieved at a pressure of 1–2 MPa. Despite the higher fluid resistance, longer droplets yielded higher acceleration and kinetic energy, because droplet splitting was a determining factor in the acceleration and using a longer droplet helped prevent it. The results provide design guidelines for achieving higher kinetic energies in the microdroplet collider for various microfluidic applications.

  12. High-pressure elasticity of stishovite and the P42/mnm ⇌ Pnnm phase transition

    Science.gov (United States)

    Carpenter, Michael A.; Hemley, Russell J.; Mao, Ho-Kwang

    2000-05-01

    A Landau free energy expansion has been developed to describe the elastic constant variations of stishovite (SiO2) associated with the P42/mnm (rutile-type) ⇌ Pnnm (CaCl2-type) phase transition as a function of pressure. The transition appears to display classical second-order character, with an equilibrium transition pressure which is renormalized by coupling of the soft optic mode with spontaneous strain. Lattice parameter data from the literature show that the symmetry breaking strain is large, while the nonsymmetry breaking strains are small. These have been used to constrain the numerical values of the strain/order parameter coupling coefficients, which in turn have been used to constrain values for the Landau coefficients. When substituted into expressions for all the individual elastic constants, taking values for experimental and calculated values of the bare elastic constants from the literature, a clear view of the pattern of elastic constant variations is produced. Variations of P and S wave velocities derived from the calculated elastic constants for a second-order transition show a dip as the transition point is approached from high pressure and from low pressure but do not show a discontinuity. The velocity anomaly provides a signature for the presence of free silica in the lower mantle.

  13. CALPHAD (calculation of phase diagrams) a comprehensive guide

    CERN Document Server

    Saunders, N

    1998-01-01

    This monograph acts as a benchmark to current achievements in the field of Computer Coupling of Phase Diagrams and Thermochemistry, often called CALPHAD which is an acronym for Computer CALculation of PHAse Diagrams. It also acts as a guide to both the basic background of the subject area and the cutting edge of the topic, combining comprehensive discussions of the underlying physical principles of the CALPHAD method with detailed descriptions of their application to real complex multi-component materials. Approaches which combine both thermodynamic and kinetic models to interpret non-equilibr

  14. Phase diagram of epidemic spreading - unimodal vs. bimodal probability distributions

    CERN Document Server

    Lancic, Alen; Sikic, Mile; Stefancic, Hrvoje

    2009-01-01

    The disease spreading on complex networks is studied in SIR model. Simulations on empirical complex networks reveal two specific regimes of disease spreading: local containment and epidemic outbreak. The variables measuring the extent of disease spreading are in general characterized by a bimodal probability distribution. Phase diagrams of disease spreading for empirical complex networks are introduced. A theoretical model of disease spreading on m-ary tree is investigated both analytically and in simulations. It is shown that the model reproduces qualitative features of phase diagrams of disease spreading observed in empirical complex networks. The role of tree-like structure of complex networks in disease spreading is discussed.

  15. Invariants in the Yukawa system’s thermodynamic phase diagram

    DEFF Research Database (Denmark)

    Veldhorst, Arno; Schrøder, Thomas; Dyre, Jeppe C.

    2015-01-01

    phase diagram deriving from the fact that they have curves (isomorphs) along which structure and dynamics in reduced units are invariant to a good approximation. We show that the Yukawa system has strong virial potential-energy correlations and identify its isomorphs by two different methods. One method...... of a known approximate analytical expression for this line in the temperature-density phase diagram. The paper's results give the first demonstration that the isomorph theory can be applied to systems like dense colloidal suspensions and strongly coupled dusty plasmas...

  16. Phase diagram of anisotropic boson t-J model

    OpenAIRE

    Boninsegni, M.; Prokof'ev, N. V.

    2007-01-01

    We have studied by Quantum Monte Carlo simulations the low temperature phase diagram of a mixture of isotopic, hard core bosons, described by the t-Jz-Jperp model, with Jperp=a Jz. Coexistence of superfluid hole-rich and insulating, antiferromagnetically ordered hole-free phases is observed at sufficiently low hole density, for any a < 1. A two-component checkerboard supersolid phase is not observed. The experimental relevance and possible broader implications of these findings are discussed.

  17. Global phase diagram of a dirty Weyl semimetal

    CERN Document Server

    Roy, Bitan; Juricic, Vladimir

    2016-01-01

    We here theoretically study the global phase diagram of a three-dimensional dirty Weyl system. The generalized Harris criterion, augmented by a perturbative renormalization-group (RG) analysis shows that weak disorder is an irrelevant perturbation at the Weyl semimetal(WSM)-insulator quantum critical point (QCP). But, a metallic phase sets in through a quantum phase transition (QPT) at strong disorder across a multicritical point, characterized by the correlation length exponent $\

  18. Strength and structural phase transitions of gadolinium at high pressure from radial X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Xiong, Lun, E-mail: xionglun@ihep.ac.cn; Liu, Jing; Bai, Ligang; Li, Xiaodong; Lin, Chuanlong [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Lin, Jung-Fu [Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Texas 78712 (United States)

    2014-12-28

    Lattice strength and structural phase transitions of gadolinium (Gd) were determined under nonhydrostatic compression up to 55 GPa using an angle-dispersive radial x-ray diffraction technique in a diamond-anvil cell at room temperature. Three new phases of fcc structure, dfcc structure, and new monoclinic structure were observed at 25 GPa, 34 GPa, and 53 GPa, respectively. The radial x-ray diffraction data yield a bulk modulus K{sub 0} = 36(1) GPa with its pressure derivate K{sub 0}′ = 3.8(1) at the azimuthal angle between the diamond cell loading axis and the diffraction plane normal and diffraction plane ψ = 54.7°. With K{sub 0}′ fixed at 4, the derived K{sub 0} is 34(1) GPa. In addition, analysis of diffraction data with lattice strain theory indicates that the ratio of differential stress to shear modulus (t/G) ranges from 0.011 to 0.014 at pressures of 12–55 GPa. Together with estimated high-pressure shear moduli, our results show that Gd can support a maximum differential stress of 0.41 GPa, while it starts to yield to plastic deformation at 16 GPa under uniaxial compression. The yield strength of Gd remains approximately a constant with increasing pressure, and reaches 0.46 GPa at 55 GPa.

  19. High-pressure phase transition of alkali metal-transition metal deuteride Li2PdD2

    Science.gov (United States)

    Yao, Yansun; Stavrou, Elissaios; Goncharov, Alexander F.; Majumdar, Arnab; Wang, Hui; Prakapenka, Vitali B.; Epshteyn, Albert; Purdy, Andrew P.

    2017-06-01

    A combined theoretical and experimental study of lithium palladium deuteride (Li2PdD2) subjected to pressures up to 50 GPa reveals one structural phase transition near 10 GPa, detected by synchrotron powder x-ray diffraction, and metadynamics simulations. The ambient-pressure tetragonal phase of Li2PdD2 transforms into a monoclinic C2/m phase that is distinct from all known structures of alkali metal-transition metal hydrides/deuterides. The structure of the high-pressure phase was characterized using ab initio computational techniques and from refinement of the powder x-ray diffraction data. In the high-pressure phase, the PdD2 complexes lose molecular integrity and are fused to extended [PdD2]∞ chains. The discovered phase transition and new structure are relevant to the possible hydrogen storage application of Li2PdD2 and alkali metal-transition metal hydrides in general.

  20. Phase diagram of a model of the protein amelogenin

    Science.gov (United States)

    Haaga, Jason; Pemberton, Elizabeth; Gunton, J. D.; Rickman, J. M.

    2016-08-01

    There has been considerable recent interest in the self-assembly and phase behavior of models of colloidal and protein particles with anisotropic interactions. One example of particular interest is amelogenin, an important protein involved in the formation of dental enamel. Amelogenin is primarily hydrophobic with a 25-residue charged C-terminus tail. This protein undergoes a hierarchical assembly process that is crucial to mineral deposition, and experimental work has demonstrated that the deletion of the C-terminus tail prevents this self-assembly. A simplified model of amelogenin has been proposed in which the protein is treated as a hydrophobic sphere, interacting via the Asakura-Oosawa (AO) potential, with a tethered point charge on its surface. In this paper, we examine the effect of the Coulomb interaction between the point charges in altering the phase diagram of the AO model. For the parameter case specific to amelogenin, we find that the previous in vitro experimental and model conditions correspond to the system being near the low-density edge of the metastable region of the phase diagram. Our study illustrates more generally the importance of understanding the phase diagram for proteins, in that the kinetic pathway for self-assembly and the resulting aggregate morphology depends on the location of the initial state in the phase diagram.

  1. Phase shifts of the paired wings of butterfly diagrams

    Institute of Scientific and Technical Information of China (English)

    Ke-Jun Li; Hong-Fei Liang; Wen Feng

    2010-01-01

    Sunspot groups observed by the Royal Greenwich Observatory/US Air Force/NOAA from 1874 May to 2008 November and the Carte Synoptique solar filaments from 1919 March to 1989 December are used to investigate the relative phase shift of the paired wings of butterfly diagrams of sunspot and filament activities.Latitudinal migration of sunspot groups(or filaments)does asynchronously occur in the northern and southern hemispheres,and there is a relative phase shift between the paired wings of their butterfly diagrams in a cycle,making the paired wings spatially asymmetrical on the solar equator.It is inferred that hemispherical solar activity strength should evolve in a similar way within the paired wings of a butterfly diagram in a cycle,demonstrating the paired wings phenomenon and showing the phase relationship between the northern and southern hemispherical solar activity strengths,as well as a relative phase shift between the paired wings of a butterfly diagram,which should bring about almost the same relative phase shift of hemispheric solar activity strength.

  2. The Phase Shifts of the Paired Wings of Butterfly Diagrams

    CERN Document Server

    Li, Kejun; Feng, Wen

    2010-01-01

    Sunspot groups observed by Royal Greenwich Observatory/US Air Force/NOAA from May 1874 to November 2008 and the Carte Synoptique solar filaments from March 1919 to December 1989 are used to investigate the relative phase shift of the paired wings of butterfly diagrams of sunspot and filament activities. Latitudinal migration of sunspot groups (or filaments) does asynchronously occur in the northern and southern hemispheres, and there is a relative phase shift between the paired wings of their butterfly diagrams in a cycle, making the paired wings spatially asymmetrical on the solar equator. It is inferred that hemispherical solar activity strength should evolve in a similar way within the paired wings of a butterfly diagram in a cycle, making the paired wings just and only keep the phase relationship between the northern and southern hemispherical solar activity strengths, but a relative phase shift between the paired wings of a butterfly diagram should bring about an almost same relative phase shift of hemis...

  3. Prediction of new high pressure phase of TaB{sub 3}: First-principles

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xiaozheng [College of Science, Inner Mongolia University of Technology, Hohhot 010051 (China); State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Zhao, Erjun, E-mail: ejzhao@yahoo.com [College of Science, Inner Mongolia University of Technology, Hohhot 010051 (China); Wu, Zhijian, E-mail: zjwu@ciac.ac.cn [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China)

    2015-05-25

    Highlights: • Crystal structure of TaB{sub 3} is predicted using the evolutionary algorithm USPEX code. • The structural and mechanical properties of tantalum borides are investigated by DFT. • The stable phases are found by enthalpy-pressure relationship and convex hull. • oC16–TaB{sub 3} has a estimated hardness (41.2 GPa) and indentation strength (22.8 GPa). • High pressure is advantageous to syntheses of ruthenium Triborides oC16–TaB{sub 3}. - Abstract: The phase stability, elastic, mechanical, dynamical and electronic properties of tantalum borides, i.e., Ta{sub 2}B, TaB, Ta{sub 3}B{sub 4}, Ta{sub 5}B{sub 6}, TaB{sub 2} and TaB{sub 3}, have been investigated by first-principles. The calculated convex hull indicates that at ambient conditions, the ground state phases are tI12–Ta{sub 2}B, oC8–TaB, oC22–Ta{sub 5}B{sub 6}, oI14–Ta{sub 3}B{sub 4}, and hP3–TaB{sub 2}; while at 75 GPa, they are tI12–Ta{sub 2}B, oC8–TaB, oC22–Ta{sub 5}B{sub 6}, oI14–Ta{sub 3}B{sub 4}, hP3–TaB{sub 2} and oC16–TaB{sub 3}; oC8–TaB, oC22–Ta{sub 5}B{sub 6}, oI14–Ta{sub 3}B{sub 4}, oC16–TaB{sub 3} are the most stable phases at 120 GPa. The enthalpy-pressure relationship reveals that the hP3–TaB{sub 2} is the most stable below 75 GPa, while the predicted oC16–TaB{sub 3} becomes the most stable above 75 GPa. Combining the estimated hardness (41.2 GPa) and indentation strength (22.8 GPa) for oC16–TaB{sub 3}, it is suggested that oC16–TaB{sub 3} is hard or potential superhard. Since it is not available experimentally, further experimental synthesis could be rewarding.

  4. Structure and compressibility of the high-pressure molecular phase II of carbon dioxide

    Science.gov (United States)

    Datchi, Frédéric; Mallick, Bidyut; Salamat, Ashkan; Rousse, Gwenaëlle; Ninet, Sandra; Garbarino, Gaston; Bouvier, Pierre; Mezouar, Mohamed

    2014-04-01

    The structure and equation of state of the crystalline molecular phase II of carbon dioxide have been investigated at room temperature from 15.5 to 57.5 GPa using synchrotron x-ray diffraction methods. The CO2 samples were embedded in neon pressure medium in order to provide quasihydrostatic conditions. The x-ray diffraction patterns of phase II are best described by a tetragonal structure, with space group P42/mnm and 2 molecules per unit cell, in accordance with a previous study [Yoo et al., Phys. Rev. B 65, 104103 (2002), 10.1103/PhysRevB.65.104103]. There is however a large (15%) difference in the intramolecular C=O bond length between the present study, 1.14(3) Å, and the latter work (1.329-1.366 Å). The present value is similar to that of the free molecule and is in very good agreement with predictions based on density functional theory. The compressibility of CO2-II determined here also disagrees with the previous study: our value for the zero-pressure bulk modulus, B0=8.5(3) GPa [with B0'=(∂B/∂P)0=6.29], is 15.5 times smaller. These findings oppose the view that CO2-II is an intermediate state between the low-pressure molecular phases and the high-pressure nonmolecular forms, consistent with our previous results for phase IV [Datchi et al., Phys. Rev. Lett. 103, 185701 (2009), 10.1103/PhysRevLett.103.185701]. The x-ray diffraction patterns of CO2-II above 15 GPa indicate the presence of a large orthorhombic microstrain. Carrying out density functional theory calculations of the elastic tensor and stress-strain relation, we interpret this as due to the softness of the crystal against deviatoric stress in the [110] and symmetry-related directions. Unlike the other dioxides of the group-14 elements, there is however no mechanical or dynamical instability of the P42/mnm structure in CO2 up to 57.5 GPa at 295 K, and therefore no symmetry lowering to Pnnm.

  5. The QCD phase diagram from analytic continuation

    Directory of Open Access Journals (Sweden)

    R. Bellwied

    2015-12-01

    Full Text Available We present the crossover line between the quark gluon plasma and the hadron gas phases for small real chemical potentials. First we determine the effect of imaginary values of the chemical potential on the transition temperature using lattice QCD simulations. Then we use various formulas to perform an analytic continuation to real values of the baryo-chemical potential. Our data set maintains strangeness neutrality to match the conditions of heavy ion physics. The systematic errors are under control up to μB≈300 MeV. For the curvature of the transition line we find that there is an approximate agreement between values from three different observables: the chiral susceptibility, chiral condensate and strange quark susceptibility. The continuum extrapolation is based on Nt=10, 12 and 16 lattices. By combining the analysis for these three observables we find, for the curvature, the value κ=0.0149±0.0021.

  6. The QCD phase diagram from analytic continuation

    CERN Document Server

    Bellwied, R; Fodor, Z; Günther, J; Katz, S D; Ratti, C; Szabo, K K

    2015-01-01

    We present the crossover line between the quark gluon plasma and the hadron gas phases for small real chemical potentials. First we determine the effect of imaginary values of the chemical potential on the transition temperature using lattice QCD simulations. Then we use various formulas to perform an analytic continuation to real values of the baryo-chemical potential. Our data set maintains strangeness neutrality to match the conditions of heavy ion physics. The systematic errors are under control up to $\\mu_B\\approx 300$ MeV. For the curvature of the transition line we find that there is an approximate agreement between values from three different observables: the chiral susceptibility, chiral condensate and strange quark susceptibility. The continuum extrapolation is based on $N_t=$ 10, 12 and 16 lattices. By combining the analysis for these three observables we find, for the curvature, the value $\\kappa = 0.0149 \\pm 0.0021$.

  7. Phase diagram of matrix compressed sensing

    Science.gov (United States)

    Schülke, Christophe; Schniter, Philip; Zdeborová, Lenka

    2016-12-01

    In the problem of matrix compressed sensing, we aim to recover a low-rank matrix from a few noisy linear measurements. In this contribution, we analyze the asymptotic performance of a Bayes-optimal inference procedure for a model where the matrix to be recovered is a product of random matrices. The results that we obtain using the replica method describe the state evolution of the Parametric Bilinear Generalized Approximate Message Passing (P-BiG-AMP) algorithm, recently introduced in J. T. Parker and P. Schniter [IEEE J. Select. Top. Signal Process. 10, 795 (2016), 10.1109/JSTSP.2016.2539123]. We show the existence of two different types of phase transition and their implications for the solvability of the problem, and we compare the results of our theoretical analysis to the numerical performance reached by P-BiG-AMP. Remarkably, the asymptotic replica equations for matrix compressed sensing are the same as those for a related but formally different problem of matrix factorization.

  8. Phase diagram and thermal properties of strong-interaction matter

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Fei; Chen, Jing; Liu, Yu-Xin; Qin, Si-Xue; Roberts, Craig D.; Schmidt, Sebastian M.

    2016-05-20

    We introduce a novel method for computing the (μ, T)-dependent pressure in continuum QCD, from which we obtain a complex phase diagram and predictions for thermal properties of the dressed-quark component of the system, providing the in-medium behavior of the related trace anomaly, speed of sound, latent heat, and heat capacity.

  9. Phase Stability Diagrams for High Temperature Corrosion Processes

    Directory of Open Access Journals (Sweden)

    J. J. Ramos-Hernandez

    2013-01-01

    Full Text Available Corrosion phenomena of metals by fused salts depend on chemical composition of the melt and environmental conditions of the system. Detail knowledge of chemistry and thermodynamic of aggressive species formed during the corrosion process is essential for a better understanding of materials degradation exposed to high temperature. When there is a lack of kinetic data for the corrosion processes, an alternative to understand the thermodynamic behavior of chemical species is to utilize phase stability diagrams. Nowadays, there are several specialized software programs to calculate phase stability diagrams. These programs are based on thermodynamics of chemical reactions. Using a thermodynamic data base allows the calculation of different types of phase diagrams. However, sometimes it is difficult to have access to such data bases. In this work, an alternative way to calculate phase stability diagrams is presented. The work is exemplified in the Na-V-S-O and Al-Na-V-S-O systems. This system was chosen because vanadium salts is one of the more aggressive system for all engineering alloys, especially in those processes where fossil fuels are used.

  10. Phase diagram of a system of hard ellipsoids

    NARCIS (Netherlands)

    Frenkel, D.; Mulder, B.M.; McTaque, J.P.

    1984-01-01

    The phase diagram of a system of hard ellipsoids of revolution was investigated by means of constant-pressure Monte Carlo simulation. Prolate as well as oblate ellipsoids were considered. The results for the isotherms of the system at several different values of the length-to-breadth ratio are prese

  11. Using Nuclear Magnetic Resonance Spectroscopy for Measuring Ternary Phase Diagrams

    Science.gov (United States)

    Woodworth, Jennifer K.; Terrance, Jacob C.; Hoffmann, Markus M.

    2006-01-01

    A laboratory experiment is presented for the upper-level undergraduate physical chemistry curriculum in which the ternary phase diagram of water, 1-propanol and n-heptane is measured using proton nuclear magnetic resonance (NMR) spectroscopy. The experiment builds upon basic concepts of NMR spectral analysis, typically taught in the undergraduate…

  12. Investigating the QCD phase diagram with hadron multiplicities at NICA

    CERN Document Server

    Becattini, F

    2016-01-01

    We discuss the potential of the experimental programme at NICA to investigate the QCD phase diagram and particularly the position of the critical line at large baryon-chemical potential with accurate measurements of particle multiplicities. We briefly review the present status and we outline the tasks to be accomplished both theoretically and the experimentally to make hadronic abundances a sensitive probe.

  13. Computer-Generated Phase Diagrams for Binary Mixtures.

    Science.gov (United States)

    Jolls, Kenneth R.; And Others

    1983-01-01

    Computer programs that generate projections of thermodynamic phase surfaces through computer graphics were used to produce diagrams representing properties of water and steam and the pressure-volume-temperature behavior of most of the common equations of state. The program, program options emphasizing thermodynamic features of interest, and…

  14. Investigating the QCD phase diagram with hadron multiplicities at NICA

    Energy Technology Data Exchange (ETDEWEB)

    Becattini, F. [Universita di Firenze (Italy); INFN, Firenze (Italy); Stock, R. [Goethe University, Frankfurt am Main (Germany)

    2016-08-15

    We discuss the potential of the experimental programme at NICA to investigate the QCD phase diagram and particularly the position of the critical line at large baryon-chemical potential with accurate measurements of particle multiplicities. We briefly review the present status and we outline the tasks to be accomplished both theoretically and the experimentally to make hadronic abundances a sensitive probe. (orig.)

  15. Phase Diagrams of Electrostatically Self-Assembled Amphiplexes

    Energy Technology Data Exchange (ETDEWEB)

    V Stanic; M Mancuso; W Wong; E DiMasi; H Strey

    2011-12-31

    We present the phase diagrams of electrostatically self-assembled amphiplexes (ESA) comprised of poly(acrylic acid) (PAA), cetyltrimethylammonium chloride (CTACl), dodecane, pentanol, and water at three different NaCl salt concentrations: 100, 300, and 500 mM. This is the first report of phase diagrams for these quinary complexes. Adding a cosurfactant, we were able to swell the unit cell size of all long-range ordered phases (lamellar, hexagonal, Pm3n, Ia3d) by almost a factor of 2. The added advantage of tuning the unit cell size makes such complexes (especially the bicontinuous phases) attractive for applications in bioseparation, drug delivery, and possibly in oil recovery.

  16. Magnetic phase diagrams of classical triangular and kagome antiferromagnets

    Energy Technology Data Exchange (ETDEWEB)

    Gvozdikova, M V [Department of Physics, Kharkov National University, 61077 Kharkov (Ukraine); Melchy, P-E; Zhitomirsky, M E, E-mail: mike.zhitomirsky@cea.fr [Service de Physique Statistique, Magnetisme et Supraconductivite, UMR-E9001 CEA-INAC/UJF, 17 rue des Martyrs, 38054 Grenoble (France)

    2011-04-27

    We investigate the effect of geometrical frustration on the H-T phase diagrams of the classical Heisenberg antiferromagnets on triangular and kagome lattices. The phase diagrams for the two models are obtained from large-scale Monte Carlo simulations. For the kagome antiferromagnet, thermal fluctuations are unable to lift degeneracy completely and stabilize translationally disordered multipolar phases. We find a substantial difference in the temperature scales of the order by disorder effect related to different degeneracy of the low- and the high-field classical ground states in the kagome antiferromagnet. In the low-field regime, the Kosterlitz-Thouless transition into a spin-nematic phase is produced by unbinding of half-quantum vortices.

  17. Magnetic phase diagrams of classical triangular and kagome antiferromagnets.

    Science.gov (United States)

    Gvozdikova, M V; Melchy, P-E; Zhitomirsky, M E

    2011-04-27

    We investigate the effect of geometrical frustration on the H-T phase diagrams of the classical Heisenberg antiferromagnets on triangular and kagome lattices. The phase diagrams for the two models are obtained from large-scale Monte Carlo simulations. For the kagome antiferromagnet, thermal fluctuations are unable to lift degeneracy completely and stabilize translationally disordered multipolar phases. We find a substantial difference in the temperature scales of the order by disorder effect related to different degeneracy of the low- and the high-field classical ground states in the kagome antiferromagnet. In the low-field regime, the Kosterlitz-Thouless transition into a spin-nematic phase is produced by unbinding of half-quantum vortices.

  18. Nonequilibrium phase diagram of the driven-dissipative photonic lattice

    CERN Document Server

    Biondi, M; Türeci, H E; Schmidt, S

    2016-01-01

    We study the nonequilibrium steady state of a driven-dissipative Bose-Hubbard model with Kerr nonlinearity. Employing a mean-field decoupling for the intercavity hopping $J$, we find that the crossover between low and high photon-number states inherited from the single cavity transforms into a gas--liquid bistability at large $J$. We determine the boundary separating smooth and sharp gas--liquid transitions in the $\\Delta$--$J$ diagram, where the detuning $\\Delta$ relates to the liquid-phase photon density, and find that it exhibits a lobe structure strikingly reminiscent of the phase boundary in the equilibrium phase diagram of the Bose-Hubbard model. Going beyond mean-field, we characterize the bulk phases and the transition region by their compressibility and pair-correlations.

  19. Phase diagram of a bulk 1d lattice Coulomb gas

    Science.gov (United States)

    Démery, V.; Monsarrat, R.; Dean, D. S.; Podgornik, R.

    2016-01-01

    The exact solution, via transfer matrix, of the simple one-dimensional lattice Coulomb gas (1d LCG) model can reproduce peculiar features of ionic liquid capacitors, such as overscreening, layering, and camel- and bell-shaped capacitance curves. Using the same transfer matrix method, we now compute the bulk properties of the 1d LCG in the constant voltage ensemble. We unveil a phase diagram with rich structure exhibiting low-density disordered and high-density ordered phases, separated by a first-order phase transition at low temperature; the solid state at full packing can be ordered or not, depending on the temperature. This phase diagram, which is strikingly similar to its three-dimensional counterpart, also sheds light on the behaviour of the confined system.

  20. "Phase diagrams of Lecithin-based microemulsions containing Sodium Salicylate "

    Directory of Open Access Journals (Sweden)

    "Aboofazeli R

    2000-08-01

    Full Text Available Partial phase diagrams were constructed at 25°C to investigate the phase behaviour of systems composed of soybean lecithin, water, sodium salicylate, alcohol and isopropyl myristate. The lecithins used were the commercially available soy bean lecithins, namely E200 and E170 (phosphatidyl choline purities greater than 95% and 68-72% respectively. The cosurfactants employed were n-propanol, 2-propanol and n-butanol and these were used at lecithin/alcohol weight ratios (Km of 1:1 and 1.5:1. At a given Km, the aqueous phase consisted of a 2% w/w sodium salicylate solution. Phase diagrams showed the area of existence of a stable isotropic region along the surfactant/oil axis (i.e., reverse microemulsion area. The extension of the microemulsion domain was influenced by the purity of surfactant, the lecithin/alcohol weight ratios and the kind of the alcohol.

  1. The phase diagram of water at negative pressures: virtual ices.

    Science.gov (United States)

    Conde, M M; Vega, C; Tribello, G A; Slater, B

    2009-07-21

    The phase diagram of water at negative pressures as obtained from computer simulations for two models of water, TIP4P/2005 and TIP5P is presented. Several solid structures with lower densities than ice Ih, so-called virtual ices, were considered as possible candidates to occupy the negative pressure region of the phase diagram of water. In particular the empty hydrate structures sI, sII, and sH and another, recently proposed, low-density ice structure. The relative stabilities of these structures at 0 K was determined using empirical water potentials and density functional theory calculations. By performing free energy calculations and Gibbs-Duhem integration the phase diagram of TIP4P/2005 was determined at negative pressures. The empty hydrates sII and sH appear to be the stable solid phases of water at negative pressures. The phase boundary between ice Ih and sII clathrate occurs at moderate negative pressures, while at large negative pressures sH becomes the most stable phase. This behavior is in reasonable agreement with what is observed in density functional theory calculations.

  2. Experimental determination of the Ta–Ge phase diagram

    Energy Technology Data Exchange (ETDEWEB)

    Araújo Pinto da Silva, Antonio Augusto, E-mail: aaaps@ppgem.eel.usp.br [EEL/USP – Escola de Engenharia de Lorena (EEL), Universidade de São Paulo (USP), Pólo Urbo-Industrial Gleba AI-6, 12602-810 Lorena, SP (Brazil); Coelho, Gilberto Carvalho [EEL/USP – Escola de Engenharia de Lorena (EEL), Universidade de São Paulo (USP), Pólo Urbo-Industrial Gleba AI-6, 12602-810 Lorena, SP (Brazil); UniFoa – Centro Universitário de Volta Redonda, Núcleo de Pesquisa, Campus Três Poços, Avenida Paulo Erlei Alves Abrantes, 1325, Bairro Três Poços, 27240-560 Volta Redonda, RJ (Brazil); Nunes, Carlos Angelo; Suzuki, Paulo Atsushi [EEL/USP – Escola de Engenharia de Lorena (EEL), Universidade de São Paulo (USP), Pólo Urbo-Industrial Gleba AI-6, 12602-810 Lorena, SP (Brazil); Fiorani, Jean Marc; David, Nicolas; Vilasi, Michel [Université de Lorraine, Institut Jean Lamour, Faculté des Sciences et Technologies, BP 70239, F-54506 Vandoeuvre-lès-Nancy (France)

    2013-11-05

    Highlights: •Ta–Ge phase diagram propose for the first time. •The phase αTa{sub 5}Ge{sub 3} was not observed in samples investigated in this work. •Three eutectics reactions where determined with the liquid compositions at 20.5; 28.0; 97.0 at.% Ge. -- Abstract: In the present work, the Ta–Ge phase diagram has been experimentally studied, considering the inexistence of a Ta–Ge phase diagram in the literature. The samples were prepared via arc melting and characterized by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and X-ray Diffraction (XRD). The intermetallics phases βTa{sub 3}Ge, αTa{sub 3}Ge, βTa{sub 5}Ge{sub 3} and TaGe{sub 2} where confirmed in this system. Three eutectics reactions where determined with the liquid compositions at 20.5; 28.0; 97.0 at.% Ge. The phases βTa{sub 3}Ge and βTa{sub 5}Ge{sub 3} solidifies congruently while TaGe{sub 2} is formed through a peritectic transformation. The temperature of the Ta-rich eutectic (L ↔ Ta{sub ss} + βTa{sub 3}Ge) was measured by the Pirani-Alterthum method at 2440 °C and the Ge-rich eutectic (L ↔ TaGe{sub 2} + Ge{sub ss}) by DTA at 937 °C.

  3. Dynamical phase diagram of Gaussian wave packets in optical lattices

    Science.gov (United States)

    Hennig, H.; Neff, T.; Fleischmann, R.

    2016-03-01

    We study the dynamics of self-trapping in Bose-Einstein condensates (BECs) loaded in deep optical lattices with Gaussian initial conditions, when the dynamics is well described by the discrete nonlinear Schrödinger equation (DNLSE). In the literature an approximate dynamical phase diagram based on a variational approach was introduced to distinguish different dynamical regimes: diffusion, self-trapping, and moving breathers. However, we find that the actual DNLSE dynamics shows a completely different diagram than the variational prediction. We calculate numerically a detailed dynamical phase diagram accurately describing the different dynamical regimes. It exhibits a complex structure that can readily be tested in current experiments in BECs in optical lattices and in optical waveguide arrays. Moreover, we derive an explicit theoretical estimate for the transition to self-trapping in excellent agreement with our numerical findings, which may be a valuable guide as well for future studies on a quantum dynamical phase diagram based on the Bose-Hubbard Hamiltonian.

  4. Collapsed tetragonal phase and superconductivity of BaFe[subscript 2]As[subscript 2] under high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Uhoya, Walter; Stemshorn, Andrew; Tsoi, Georgiy; Vohra, Yogesh K.; Sefat, Athena S.; Sales, Brian C.; Hope, Kevin M.; Weir, Samuel T. (UAB); (ORNL); (LLNL); (Montevallo)

    2010-11-12

    High pressure x-ray diffraction and electrical resistance measurements have been carried out on BaFe{sub 2}As{sub 2} to a pressure of 35 GPa and temperature of 10 K using a synchrotron source and designer diamond anvils. At ambient temperature, a phase transition from the tetragonal phase to a collapsed tetragonal (CT) phase is observed at 17 GPa under nonhydrostatic conditions as compared to 22 GPa under hydrostatic conditions. The superconducting transition temperature increases rapidly with pressure up to 34 K at 1 GPa and decreases gradually with a further increase in pressure. Our results suggest that T{sub C} falls below 10 K in the pressure range of 16-30 GPa, where CT phase is expected to be stable under high-pressure and low-temperature conditions.

  5. Phase diagram of hot QCD in an external magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Fraga, Eduardo; Mizher, Ana Julia [Instituto de Fisica, Universidade Federal do Rio de Janeiro, CP 68528, Rio de Janeiro, 21945-970 RJ (Brazil); Chernodub, Maxim [Laboratoire de Mathematiques et Physique Theorique - LMPT, CNRS UMR 6083 Tours, Federation Denis Poisson, Faculte des Sciences et Techniques, Universite Francois Rabelais, Parc de Grandmont, 37200 Tours (France)

    2010-07-01

    The structure of the phase diagram for strong interactions becomes richer in the presence of a magnetic background, which enters as a new control parameter for the thermodynamics, and can exhibit new phases and interesting features. Motivated by the relevance of this physical setting for current and future high-energy heavy ion collision experiments and for the cosmological QCD transitions, we use the linear sigma model coupled to quarks and to Polyakov loops as an effective theory to investigate how the chiral and the deconfining transitions are affected, and present a general picture for the temperature-magnetic field phase diagram. We compute and discuss each contribution to the effective potential for the approximate order parameters, and uncover new phenomena such as the para-magnetically-induced breaking of Z(3). (authors)

  6. Complete Phase Diagrams for a Holographic Superconductor/Insulator System

    CERN Document Server

    Horowitz, Gary T

    2010-01-01

    The gravitational dual of an insulator/superconductor transition driven by increasing the chemical potential has recently been constructed. However, the system was studied in a probe limit and only a part of the phase diagram was obtained. We include the backreaction and construct the complete phase diagram for this system. For fixed chemical potential there are typically two phase transitions as the temperature is lowered. Surprisingly, for a certain range of parameters, the system first becomes a superconductor and then becomes an insulator as the temperature approaches zero. As a byproduct of our analysis, we also construct the gravitational dual of a Bose-Einstein condensate of glueballs in a confining gauge theory.

  7. Si-Ge-metal ternary phase diagram calculations

    Science.gov (United States)

    Fleurial, J. P.; Borshchevsky, A.

    1990-01-01

    Solution crystal growth and doping conditions of Si-Ge alloys used for high-temperature thermoelectric generation are determined here. Liquid-phase epitaxy (LPE) has been successfully employed recently to obtain single-crystalline homogeneous layers of Si-Ge solid solutions from a liquid metal solvent. Knowledge of Si-Ge-metallic solvent ternary phase diagrams is essential for further single-crystal growth development. Consequently, a thermodynamic equilibrium model was used to calculate the phase diagrams of the Si-Ge-M systems, including solid solubilities, where M is Al, Ga, In, Sn, Pb, Sb, or Bi. Good agreement between calculated liquidus and solidus data and experimental DTA and microprobe results was obtained. The results are used to compare the suitability of the different systems for crystal growth (by LPE-type process).

  8. Evaluation of self-interaction parameters from binary phase diagrams

    Energy Technology Data Exchange (ETDEWEB)

    Ellison, T. L.

    1977-10-01

    The feasibility of calculating Wagner self-interaction parameters from binary phase diagrams was examined. The self-interaction parameters of 22 non-ferrous liquid solutions were calculated utilizing an equation based on the equality of the chemical potentials of a component in two equilibrium phases. Utilization of the equation requires the evaluation of the first and second derivatives of various liquidus and solidus data at infinite dilution of the solute component. Several numerical methods for evaluating the derivatives of tabular data were examined. A method involving power series curve fitting and subsequent differentiation of the power series was found to be the most suitable for the interaction parameter calculations. Comparison of the calculated self-interaction parameters with values obtained from thermodynamic measurements indicates that the Wagner self-interaction parameter can be successfully calculated from binary phase diagrams.

  9. Mapping Isobaric Aging onto the Equilibrium Phase Diagram

    Science.gov (United States)

    Niss, Kristine

    2017-09-01

    The linear volume relaxation and the nonlinear volume aging of a glass-forming liquid are measured, directly compared, and used to extract the out-of-equilibrium relaxation time. This opens a window to investigate how the relaxation time depends on temperature, structure, and volume in parts of phase space that are not accessed by the equilibrium liquid. It is found that the temperature dependence of relaxation time is non-Arrhenius even in the isostructural case—challenging the Adam-Gibbs entropy model. Based on the presented data and the idea that aging happens through quasiequilibrium states, we suggest a mapping of the out-of-equilibrium states during isobaric aging to the equilibrium phase diagram. This mapping implies the existence of isostructural lines in the equilibrium phase diagram. The relaxation time is found to depend on the bath temperature, density, and a just single structural parameter, referred to as an effective temperature.

  10. Phase diagrams of nanoalloys: influence of size and morphology.

    Science.gov (United States)

    Berthier, F; Maras, E; Legrand, B

    2015-11-14

    The size dependence of the phase diagram of nanoalloys with a tendency to phase separate is investigated. As the critical temperature may depend on both the size and the morphology of the nanoparticles, we consider nanowires with different cross-sections and also nanotubes with different circumferences. The variation of the critical temperature with the length of all these nanoparticles is systematically studied using Monte Carlo simulations based on an Ising model. A non-monotonic variation of the critical temperature is observed as a function of the length. The maximal value of the critical temperature is reached when the length and the circumference of the nanoparticles are similar. The phase diagrams obtained within two thermodynamic ensembles (the canonical ensemble and the pseudo grand canonical ensemble) are compared and discussed in terms of the behaviour of a single particle or an assembly of nanoparticles in mutual equilibrium with each other.

  11. Microcanonical Phase Diagram of the BEG and Ising Models

    Institute of Scientific and Technical Information of China (English)

    李粮生; 郑宁; 史庆藩

    2012-01-01

    The density of states of long-range Blume-Emery-Criffiths (BEG) and short-range lsing models are obtained by using Wang-Landau sampling with adaptive windows in energy and magnetization space. With accurate density of states, we are able to calculate the mierocanonical specific heat of fixed magnetization introduced by Kastner et al. in the regions of positive and negative temperature. The microcanonical phase diagram of the Ising model shows a continuous phase transition at a negative temperature in energy and magnetization plane. However the phase diagram of the long-range model constructed by peaks of the microeanonieal specific heat looks obviously different from the Ising chart.

  12. Poly(N-isopropylacrylamide) Phase Diagrams: Fifty Years of Research.

    Science.gov (United States)

    Halperin, Avraham; Kröger, Martin; Winnik, Françoise M

    2015-12-14

    In 1968, Heskins and Guillet published the first systematic study of the phase diagram of poly(N-isopropylacrylamide) (PNIPAM), at the time a "young polymer" first synthesized in 1956. Since then, PNIPAM became the leading member of the growing families of thermoresponsive polymers and of stimuli-responsive, "smart" polymers in general. Its thermal response is unanimously attributed to its phase behavior. Yet, in spite of 50 years of research, a coherent quantitative picture remains elusive. In this Review we survey the reported phase diagrams, discuss the differences and comment on theoretical ideas regarding their possible origins. We aim to alert the PNIPAM community to open questions in this reputably mature domain.

  13. Phase Diagrams of Electric-Fduced Aggregation in Conducting Colloids

    Science.gov (United States)

    Khusid, B.; Acrivos, A.

    1999-01-01

    Under the application of a sufficiently strong electric field, a suspension may undergo reversible phase transitions from a homogeneous random arrangement of particles into a variety of ordered aggregation patterns. The surprising fact about electric-field driven phase transitions is that the aggregation patterns, that are observed in very diverse systems of colloids, display a number of common structural features and modes of evolution thereby implying that a universal mechanism may exist to account for these phenomena. It is now generally believed that this mechanism emanates from the presence of the long-range anisotropic interactions between colloidal particles due to their polarization in an applied field. But, in spite of numerous applications of the electric-field-driven phenomena in biotechnology, separation, materials engineering, chemical analysis, etc. our understanding of these phenomena is far from complete. Thus, it is the purpose of the proposed research to develop a theory and then test experimentally, under normal- and low-gravity conditions, the accuracy of the theoretical predictions regarding the effect of the synergism of the interparticle electric and hydrodynamic interactions on the phase diagram of a suspension. The main results from our theoretical studies performed to-date enable one to trace how the variations of the electrical properties of the constituent materials influence the topology of the suspension phase diagram and then, by using an appropriate phase diagram, to evaluate how the electric-field-induced transformations will depend on the frequency and the strength of the applied field.

  14. New high-pressure phase of MgH2: An ab initio constant-pressure study

    Science.gov (United States)

    Durandurdu, Murat

    2014-02-01

    The stability of magnesium hydride (MgH2) at high pressure is studied using a constant-pressure ab initio technique. Two phase transformations are successfully observed through the simulations. The rutile structure undergoes a phase transformation into a CaCl2-type phase. Further increase in pressure results into a first-order phase transition into an orthorhombic state within Pbcm symmetry. This phase can be considered as a distorted CaF2-type crystal and does not correspond to the previously proposed MgH2 phases. The transformation mechanism of the CaCl2-Pbcm phase change at the atomistic level is successfully characterized and it is found that the CaCl2-to-Pbcm phase change proceeds via an ideal CaF2-type intermediate phase. These phase transformations are also analyzed using total energy-volume calculations.

  15. The High-Pressure Phase of MgB2C2

    NARCIS (Netherlands)

    Woerle, Michael; Fischbach, Urs; Widmer, Daniel; Krumeich, Frank; Nesper, Reinhard; Evers, Juergen; Stalder, Roland; Ulmer, Peter

    2010-01-01

    A high-pressure modification of MgB2C2 was synthesized and structurally characterized. The compound crystallizes in the orthorhombic space group Pnnm, with the lattice parameters a = 7.19633(3) angstrom, b = 4.61791(13) angstrom and c = 2.77714(8) angstrom. The compound contains heterographene B-C n

  16. Thermal fluctuations and phase diagrams of the phase-field crystal model with pinning.

    Science.gov (United States)

    Ramos, J A P; Granato, E; Achim, C V; Ying, S C; Elder, K R; Ala-Nissila, T

    2008-09-01

    We study the influence of thermal fluctuations in the phase diagram of a recently introduced two-dimensional phase field crystal model with an external pinning potential. The model provides a continuum description of pinned lattice systems allowing for both elastic deformations and topological defects. We introduce a nonconserved version of the model and determine the ground-state phase diagram as a function of lattice mismatch and strength of the pinning potential. Monte Carlo simulations are used to determine the phase diagram as a function of temperature near commensurate phases. The results show a rich phase diagram with commensurate, incommensurate, and liquidlike phases with a topology strongly dependent on the type of ordered structure. A finite-size scaling analysis of the melting transition for the c(2x2) commensurate phase shows that the thermal correlation length exponent nu and specific heat behavior are consistent with the Ising universality class as expected from analytical arguments.

  17. In Situ Observations of Thermoreversible Gelation and Phase Separation of Agarose and Methylcellulose Solutions under High Pressure.

    Science.gov (United States)

    Kometani, Noritsugu; Tanabe, Masahiro; Su, Lei; Yang, Kun; Nishinari, Katsuyoshi

    2015-06-04

    Thermoreversible sol-gel transitions of agarose and methylcellulose (MC) aqueous solutions on isobaric cooling or heating under high pressure up to 400 MPa have been investigated by in situ observations of optical transmittance and falling-ball experiments. For agarose, which undergoes the gelation on cooling, the application of pressure caused a gradual rise in the cloud-point temperature over the whole pressure range examined, which is almost consistent with the pressure dependence of gelling temperature estimated by falling-ball experiments, suggesting that agarose gel is stabilized by compression and that the gelation occurs nearly in parallel with phase separation under ambient and high-pressure conditions. For MC, which undergoes the gelation on heating, the cloud-point temperature showed a slight rise with an initial elevation of pressure up to ∼150 MPa, whereas it showed a marked depression above 200 MPa. In contrast, the gelling temperature of MC, which is nearly identical to the cloud-point temperature at ambient pressure, showed a monotonous rise with increasing pressure up to 350 MPa, which means that MC undergoes phase separation prior to gelation on heating under high pressure above 200 MPa. Similar results were obtained for the melting process of MC gel on cooling. The unique behavior of the sol-gel transition of MC under high pressure has been interpreted in terms of the destruction of hydrophobic hydration by compression.

  18. Global phase diagram of disordered type-II Weyl semimetals

    Science.gov (United States)

    Wu, Yijia; Liu, Haiwen; Jiang, Hua; Xie, X. C.

    2017-07-01

    With electron and hole pockets touching at the Weyl node, type-II Weyl semimetal is a newly proposed topological state distinct from its type-I cousin. We numerically study the localization effect for tilted type-I as well as type-II Weyl semimetals and give the global phase diagram. For disordered type-I Weyl semimetal, an intermediate three-dimensional quantum anomalous Hall phase is confirmed between Weyl semimetal phase and diffusive metal phase. However, this intermediate phase is absent for disordered type-II Weyl semimetal. Besides, along the direction of tilt, comparing to its type-I cousin, type-II Weyl semimetal typically possesses longer normalized localization length and therefore it is more robust against disorder. Near the phase boundary between the type-I and the type-II Weyl semimetals, infinitesimal disorder will induce an insulating phase so that, in this region, the concept of Weyl semimetal is meaningless for real materials.

  19. Confinement in Polyakov gauge and the QCD phase diagram

    Energy Technology Data Exchange (ETDEWEB)

    Marhauser, Marc Florian

    2009-10-14

    We investigate Quantum Chromodynamics (QCD) in the framework of the functional renormalisation group (fRG). Thereby describing the phase transition from the phase with confined quarks into the quark-gluon-plasma phase. We focus on a physical gauge in which the mechanism driving the phase transition is discernible. We find results compatible with lattice QCD data, as well as with functional methods applied in different gauges. The phase transition is of the expected order and we computed critical exponents. Extensions of the model are discussed. When investigating the QCD phase diagram, we compute the effects of dynamical quarks at finite density on the running of the gauge coupling. Additionally, we calculate how these affect the deconfinement phase transition, also, dynamical quarks allow for the inclusion of a finite chemical potential. Concluding the investigation of the phase diagram, we establish a relation between confinement and chiral symmetry breaking, which is tied to the dynamical generation of hadron masses. In the investigations, we often encounter scale dependent fields. We investigate a footing on which these can be dealt with in a uniform way. (orig.)

  20. Phase diagram of model anisotropic particles with octahedral symmetry

    OpenAIRE

    Noya, E. G.; Vega, C.; Doye, J. P. K.; Louis, A. A.

    2007-01-01

    We computed the phase diagram for a system of model anisotropic particles with six attractive patches in an octahedral arrangement. We chose to study this model for a relatively narrow value of the patch width where the lowest-energy configuration of the system is a simple cubic crystal. At this value of the patch width, there is no stable vapour-liquid phase separation, and there are three other crystalline phases in addition to the simple cubic crystal that is most stable at low pressure. F...

  1. New type of phase transformation in gas hydrate forming system at high pressures. Some experimental and computational investigations of clathrate hydrates formed in the SF6-H2O system.

    Science.gov (United States)

    Aladko, E Ya; Ancharov, A I; Goryainov, S V; Kurnosov, A V; Larionov, E G; Likhacheva, A Yu; Manakov, A Yu; Potemkin, V A; Sheromov, M A; Teplykh, A E; Voronin, V I; Zhurko, F V

    2006-10-26

    In this work, we present a new, previously unknown type of structure transformation in the high-pressure gas hydrates, which is related to the existence of two different isostructural phases of the sulfur hexafluoride clathrate hydrates. Each of these phases has its own stability field on the phase diagram. The difference between these hydrates consists of partial filling of small D cages by SF(6) molecules in the high-pressure phase; at 900 MPa, about half of small cages are occupied. Our calculations indicate that the increase of population of small cavities is improbable, therefore, at any pressure value, a part of the cavities remains vacant and the packing density is relatively low. This fact allowed us to suppose the existence of the upper pressure limit of hydrate formation in this system; the experimental results obtained confirm this assumption.

  2. Collapsing cycloidal structures in the magnetic phase diagram of erbium

    DEFF Research Database (Denmark)

    Jehan, D.A.; McMorrow, D.F.; Simpson, J.A.;

    1994-01-01

    how it distorts as the field is increased. In low fields, there is a spin reorientation, so that the plane of the cycloid becomes perpendicular to the applied field, while in larger fields, the cycloid collapses through a series of fanlike structures. At lower temperatures, as the field is increased......The magnetic structure of Er with a magnetic field applied in the hexagonal basal plane has been studied using a combination of experimental techniques and mean-field modeling. From neutron-scattering and magnetization measurements, phase diagrams are constructed. At temperatures above...... approximately 20 K, the application of a field is found to favor cycloidal structures with modulation wave vectors of q(c) = (6/23)c*, (4/15)c*, and (2/7)c*. For fields above almost-equal-to 40 kOe, the (2/7) structure dominates the phase diagram. From a detailed study of this most stable cycloid, we determine...

  3. Multiple nonergodic disordered states in Laponite suspensions: A phase diagram

    Science.gov (United States)

    Jabbari-Farouji, S.; Tanaka, Hajime; Wegdam, G. H.; Bonn, Daniel

    2008-12-01

    We study the time evolution of different Laponite suspensions from a low-viscosity ergodic state to a viscoelastic nonergodic state over a wide range of volume fractions and salt contents. We find that the evolution of nonergodicity parameter (Debye-Waller factor) splits into two branches for all the samples, which correspond to two distinct dynamically arrested states. At moderately high salt concentrations, on the other hand, a third nonergodic state appears that is different from the above two nonergodic states. Measurement of the conductivity of Laponite solutions in pure water shows that the contribution of counterions in the ionic strength is considerable and their role should be taken into account in interpretations of aging dynamics and the phase diagram. Based on these data and available data in the literature, we propose a (nonequilibrium) phase diagram for Laponite suspensions.

  4. Phase Diagrams for the PEO-LiX Electrolyte System.

    Science.gov (United States)

    1987-01-01

    rather flat, in sharp contrast to previous results. 3.2c PEO- LiBF4 System Pure PEO forms complexes with LiBF , and the subsequent phase diagram for...study; 0 ----NMR(15); 0 -DSC or DTA(7, 10,12); A ---a.c.conductivity(6,10,12); 4- optical microscopy(6). is 350 - (PEO) n- LiBF4 300 (PEO) n-LiCF 3SO 3...the PEO- LiBF4 system IS" , " ATOM RATIO O/Li 50 25 8 4 2 1 250 200 150 1 00 -50I 0 0 0.1 0.2 0.3 0.4 0.5 XLiPF6 -’+’ Figure 6. Phase diagram of the

  5. Phase diagram of hydrogen adsorbed on Ni(111)

    Science.gov (United States)

    Nagai, Kiyoshi; Ohno, Yuichi; Nakamura, Takashi

    1984-08-01

    The phase diagram for the H/Ni(111) system is calculated by treating a lattice gas on a honeycomb lattice through the position-space renormalization-group theory with prefacing transformation. The following interparticle interactions are considered: (A) nearest-neighbor exclusion, second-neighbor repulsion, and third-neighbor attraction, which was previously proposed by Domany et al.; (B) nearest-neighbor exclusion, second- and third-neighbor repulsions, and further-neighbor interactions up to the sixth-neighbor one. When the interaction parameters involved are suitably adjusted, both the interactions (A) and (B) lead to the phase diagrams in good agreement with the experimental one by Christmann et al. The change of the isosteric heat of hydrogen adsorption with the adsorbed amount is also calculated. The result obtained from interaction (B) is consistent with experiment, whereas that from interaction (A) is not.

  6. Size Dependent Phase Diagrams of Nickel-Carbon Nanoparticles.

    Science.gov (United States)

    Magnin, Y; Zappelli, A; Amara, H; Ducastelle, F; Bichara, C

    2015-11-13

    The carbon rich phase diagrams of nickel-carbon nanoparticles, relevant to catalysis and catalytic chemical vapor deposition synthesis of carbon nanotubes, are calculated for system sizes up to about 3 nm (807 Ni atoms). A tight binding model for interatomic interactions drives the grand canonical Monte Carlo simulations used to locate solid, core shell and liquid stability domains, as a function of size, temperature, and carbon chemical potential or concentration. Melting is favored by carbon incorporation from the nanoparticle surface, resulting in a strong relative lowering of the eutectic temperature and a phase diagram topology different from the bulk one. This should lead to a better understanding of the nanotube growth mechanisms.

  7. Sign-posting the phase diagram of quantum chromodynamics

    Indian Academy of Sciences (India)

    Sourendu Gupta

    2012-10-01

    The good agreement between lattice predictions and data for the shape of the distribution of event-by-event fluctuations of the baryon number is discussed. Such comparisons can give fine probes of thermalization, and can be used to provide a direct determination of the cross-over temperature c QCD. The logic of these comparisons and the systematics involved are discussed. The same methods can be used to further explore the phase diagram.

  8. Phase diagram of strong interactions in an external magnetic field

    CERN Document Server

    Mizher, Ana Julia; Chernodub, M N

    2011-01-01

    We obtain the phase diagram of strong interactions in the presence of a magnetic field within the linear sigma model coupled to quarks and to the Polyakov loop, and show that the chiral and deconfinement lines can split. We also study the behavior of the chiral condensate in this magnetic environment and find an approximately linear dependence on the external field, in accordance with lattice data.

  9. Lattice dynamics and phase diagram of aluminum at high temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Kudasov, Yu. B., E-mail: yu_kudasov@yahoo.com; Surdin, O. M.; Korshunov, A. S.; Pavlov, V. N. [National Research Nuclear University ' MEPhI,' , Sarov State Institute of Physics and Technology (Russian Federation); Frolova, N. V.; Kuzin, R. S. [Russian Federal Nuclear Center-All-Russian Research Institute of Experimental Physics (Russian Federation)

    2013-10-15

    The dispersion of phonons in the fcc, hcp, and bcc phases of aluminum is calculated at ultrahigh pressures by the method of small displacements in a supercell. The stability of the phonon subsystem is studied. The thermodynamic characteristics are calculated in the quasi-harmonic approximation, and a phase diagram of aluminum is plotted. As compared to the Debye model, the use of a phonon spectrum calculated in the quasi-harmonic approximation significantly broadens the hcp phase field and strongly shifts the phase boundary between the fcc and bcc phases. The normal isentrope is calculated at megabar pressures. It is shown to intersect the fcc-hcp and hcp-bcc phase boundaries. The sound velocity along the normal isentrope is calculated. It is shown to have a nonmonotonic character.

  10. Full Phase Diagram of the Massive Gross-Neveu Model

    CERN Document Server

    Schnetz, O; Urlichs, K; Schnetz, Oliver; Thies, Michael; Urlichs, Konrad

    2006-01-01

    The massive Gross-Neveu model is solved in the large N limit at finite temperature and chemical potential. The scalar potential is given in terms of Jacobi elliptic functions. It contains three parameters which are determined by transcendental equations. Self-consistency of the scalar potential is proved. The phase diagram for non-zero bare quark mass is found to contain a kink-antikink crystal phase as well as a massive fermion gas phase featuring a cross-over from light to heavy effective fermion mass. For zero bare quark mass we recover the three known phases kink-antikink crystal, massless fermion gas, and massive fermion gas. All phase transitions are shown to be of second order. Equations for the phase boundaries are given and solved numerically. Implications on condensed matter physics are indicated where our results generalize the bipolaron lattice in non-degenerate conducting polymers to finite temperature.

  11. Study of cements silicate phases hydrated under high pressure and high temperature; Etude des phases silicatees du ciment hydrate sous haute pression et haute temperature

    Energy Technology Data Exchange (ETDEWEB)

    Meducin, F.

    2001-10-01

    This study concerns the durability of oil-well cementing. Indeed, in oil well cementing a cement slurry is pumped down the steel casing of the well up the annular space between it and the surrounding rock to support and protect the casing. The setting conditions of pressure and temperature may be very high (up to 1000 bar and 250 deg C at the bottom of the oil-well). In this research, the hydration of the main constituent of cement, synthetic tri-calcium silicate Ca{sub 3}SiO{sub 2}, often called C{sub 3}S (C = CaO; S = SiO{sub 2} and H H{sub 2}O), is studied. Calcium Silicate hydrates are prepared in high-pressure cells to complete their phase diagram (P,T) and obtain the stability conditions for each species. Indeed, the phases formed in these conditions are unknown and the study consists in the hydration of C{sub 3}S at different temperatures, pressures, and during different times to simulate the oil-well conditions. In a first step (until 120 deg C at ambient pressure) the C-S-H, a not well crystallized and non-stoichiometric phase, is synthesized: it brings adhesion and mechanical properties., Then, when pressure and temperature increase, crystallized phases appear such as jaffeite (Ca{sub 6}(Si{sub 2}O{sub 7})(OH){sub 6}) and hillebrandite (Ca{sub 2}(SiO{sub 3})(OH){sub 2}). Silicon {sup 29}Si Nuclear Magnetic Resonance (using standard sequences MAS, CPMAS) allow us to identify all the silicates hydrates formed. Indeed, {sup 29}Si NMR is a valuable tool to determine the structure of crystallized or not-well crystallized phases of cement. The characterization of the hydrated samples is completed by other techniques: X- Ray Diffraction and Scanning Electron Microscopy. The following results are found: jaffeite is the most stable phase at C/S=3. To simulate the hydration of real cement, hydration of C{sub 3}S with ground quartz and with or without super-plasticizers is done. In those cases, new phases appear: kilchoanite mainly, and xonotlite. A large amount of

  12. Theoretical calculations of the high-pressure phases of ZnF2 and CdF2

    Science.gov (United States)

    Wu, X.; Wu, Z.

    2006-04-01

    First-principles calculations based on density functional theory were used to study the high-pressure phases of both ZnF2 and CdF2. We found that the sequence of the pressure-induced phase transitions is: Rutile (P42/mnm) ↦ CaCl2 (Pnnm) ↦ PdF2 (Pa-3) and CaF2 (Fm3m) ↦ PbCl2 (Pnma) ↦ Ni2In (P63/mmc) for ZnF2 and CdF2 respectively. In ZnF2 the behavior of the ground-state total energy, of the Gibbs free energy and of the lattice constant vs. pressure shown that the phase transition at 4 GPa from the rutile-type phase to the CaCl2-type phase is a second-order phase transition. The mechanism of the structural change was also revealed by the transition from the PbCl2-type phase to the Ni2In-type phase in CdF2. Moreover, the high-pressure behavior of divalent metal fluorides was compared and discussed.

  13. Development and testing of a high-pressure downhole pump for jet-assist drilling. Topical report, Phase II

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-10-01

    The goal of jet-assisted drilling is to increase the rate of penetration (ROP) in deeper gas and oil wells, where the rocks become harder and more difficult to drill. Increasing the ROP can result in fewer drilling days, and therefore, lower drilling cost. In late 1993, FlowDril and the Gas Research Institute (GRI) began a three-year development of a down hole pump (DHP{reg_sign}) capable of producing 30,000 psi out pressure to provide the high-pressure flow for high-pressure jet-assist of the drill bit. The U.S. Department of Energy (DOE) through its Morgantown, WV (DOE-Morgantown) field office, joined with GRI and FlowDril to develop and test a second prototype designed for drilling in 7-7/8 inch holes. This project, {open_quotes}Development and Testing of a High-Pressure Down Hole Pump for Jet-Assist Drilling,{close_quotes} is for the development and testing of the second prototype. It was planned in two phases. Phase I included an update of a market analysis, a design, fabrication, and an initial laboratory test of the second prototype. Phase II is continued iterative laboratory and field developmental testing. This report summarizes the results of Phase II. In the downhole pump approach shown in the following figure, conventional drill pipe and drill collars are used, with the DHP as the last component of the bottom hole assembly next to the bit. The DHP is a reciprocating double ended, intensifier style positive displacement, high-pressure pump. The drive fluid and the high-pressure output fluid are both derived from the same source, the abrasive drilling mud pumped downhole through the drill string. Approximately seven percent of the stream is pressurized to 30,000 psi and directed through a high-pressure nozzle on the drill bit to produce the high speed jet and assist the mechanical action of the bit to make it drill faster.

  14. Modelling ruptures of buried high pressure dense phase CO2 pipelines in carbon capture and storage applications - Part I. Validation

    OpenAIRE

    Wareing, CJ; Fairweather, M.; Falle, SAEG; Woolley, RM

    2015-01-01

    Carbon dioxide (CO2) capture and storage presents a short-term option for significantly reducing the amount of CO2 released into the atmosphere and mitigating the effects of climate change. To this end, National Grid initiated the COOLTRANS research programme to consider the pipeline transportation of high pressure dense phase CO2, including the development and application of a mathematical model for predicting the sonic near-field dispersion of pure CO2 following the venting or failure of su...

  15. Monitoring Rates and Heterogeneity of High-Pressure Germination of Bacillus Spores by Phase-Contrast Microscopy of Individual Spores

    Science.gov (United States)

    2014-01-01

    SECURITY CLASSIFICATION OF: The germination of multiple individual Bacillus subtilis spores by a high pressure (HP) of 140-150 (unless noted...otherwise) megaPascals (MPa) that activates spore germinant receptors (GRs) was monitored by phase contrast microscopy in a diamond anvil cell. Major...conclusions were that: i) >95% of spores germinated in 40 min; ii) individual spore’s HP germination kinetics were very similar to those for nutrient

  16. Ground-State Phase Diagram of S = 1 Diamond Chains

    Science.gov (United States)

    Hida, Kazuo; Takano, Ken'ichi

    2017-03-01

    We investigate the ground-state phase diagram of a spin-1 diamond chain. Owing to a series of conservation laws, any eigenstate of this system can be expressed using the eigenstates of finite odd-length chains or infinite chains with spins 1 and 2. The ground state undergoes quantum phase transitions with varying λ, a parameter that controls frustration. Exact upper and lower bounds for the phase boundaries between these phases are obtained. The phase boundaries are determined numerically in the region not explored in a previous work [Takano et al., https://doi.org/10.1088/0953-8984/8/35/009" xlink:type="simple">J. Phys.: Condens. Matter 8, 6405 (1996)].

  17. Phase diagram of hard snowman-shaped particles.

    Science.gov (United States)

    Dennison, Matthew; Milinković, Kristina; Dijkstra, Marjolein

    2012-07-28

    We present the phase diagram of hard snowman-shaped particles calculated using Monte Carlo simulations and free energy calculations. The snowman particles consist of two hard spheres rigidly attached at their surfaces. We find a rich phase behavior with isotropic, plastic crystal, and aperiodic crystal phases. The crystalline phases found to be stable for a given sphere diameter ratio correspond mostly to the close packed structures predicted for equimolar binary hard-sphere mixtures of the same diameter ratio. However, our results also show several crystal-crystal phase transitions, with structures with a higher degree of degeneracy found to be stable at lower densities, while those with the best packing are found to be stable at higher densities.

  18. Phase diagram and critical end point for strongly interacting quarks.

    Science.gov (United States)

    Qin, Si-xue; Chang, Lei; Chen, Huan; Liu, Yu-xin; Roberts, Craig D

    2011-04-29

    We introduce a method based on chiral susceptibility, which enables one to draw a phase diagram in the chemical-potential-temperature plane for strongly interacting quarks whose interactions are described by any reasonable gap equation, even if the diagrammatic content of the quark-gluon vertex is unknown. We locate a critical end point at (μ(E),T(E))∼(1.0,0.9)T(c), where T(c) is the critical temperature for chiral-symmetry restoration at μ=0, and find that a domain of phase coexistence opens at the critical end point whose area increases as a confinement length scale grows.

  19. The Phase Diagram of QC2D from Functional Methods

    CERN Document Server

    Khan, Naseemuddin; Rennecke, Fabian; Scherer, Michael M

    2015-01-01

    We study the phase diagram of two-color Quantum Chromodynamics at finite temperature and chemical potential. This is done within an effective low-energy description in terms of quarks, mesons and diquarks. Quantum, thermal and density fluctuations are taken into account with the functional renormalisation group approach. In particular, we establish the phenomenon of pre-condensation, affecting the location of the phase boundary to Bose-Einstein condensation. We also discuss the Silver Blaze property in the context of the functional renormalisation group.

  20. The phase diagram of NiSi under the conditions of small planetary interiors

    Science.gov (United States)

    Dobson, David P.; Hunt, Simon A.; Ahmed, Jabraan; Lord, Oliver T.; Wann, Elizabeth T. H.; Santangeli, James; Wood, Ian G.; Vočadlo, Lidunka; Walker, Andrew M.; Thomson, Andrew R.; Baron, Marzena A.; Mueller, Hans J.; Lathe, Christian; Whitaker, Matthew; Morard, Guillaume; Mezouar, Mohamed

    2016-12-01

    The phase diagram of NiSi has been determined using in situ synchrotron X-ray powder diffraction multi-anvil experiments to 19 GPa, with further preliminary results in the laser-heated diamond cell reported to 60 GPa. The low-pressure MnP-structured phase transforms to two different high-pressure phases depending on the temperature: the ε-FeSi structure is stable at temperatures above ∼1100 K and a previously reported distorted-CuTi structure (with Pmmn symmetry) is stable at lower temperature. The invariant point is located at 12.8 ± 0.2 GPa and 1100 ± 20 K. At higher pressures, ε-FeSi-structured NiSi transforms to the CsCl structure with CsCl-NiSi as the liquidus phase above 30 GPa. The Clapeyron slope of this transition is -67 MPa/K. The phase boundary between the ε-FeSi and Pmmn structured phases is nearly pressure independent implying there will be a second sub-solidus invariant point between CsCl, ε-FeSi and Pmmn structures at higher pressure than attained in this study. In addition to these stable phases, the MnP structure was observed to spontaneously transform at room temperature to a new orthorhombic structure (also with Pnma symmetry) which had been detailed in previous ab initio simulations. This new phase of NiSi is shown here to be metastable.

  1. Pitfalls and feedback when constructing topological pressure-temperature phase diagrams

    Science.gov (United States)

    Ceolin, R.; Toscani, S.; Rietveld, Ivo B.; Barrio, M.; Tamarit, J. Ll.

    2017-04-01

    The stability hierarchy between different phases of a chemical compound can be accurately reproduced in a topological phase diagram. This type of phase diagrams may appear to be the result of simple extrapolations, however, experimental complications quickly increase in the case of crystalline trimorphism (and higher order polymorphism). To ensure the accurate positioning of stable phase domains, a topological phase diagram needs to be consistent. This paper gives an example of how thermodynamic feedback can be used in the topological construction of phase diagrams to ensure overall consistency in a phase diagram based on the case of piracetam crystalline trimorphism.

  2. Phase diagram of the triangular-lattice Potts antiferromagnet

    Science.gov (United States)

    Lykke Jacobsen, Jesper; Salas, Jesús; Scullard, Christian R.

    2017-08-01

    We study the phase diagram of the triangular-lattice Q-state Potts model in the real (Q, v) -plane, where v=e^J-1 is the temperature variable. Our first goal is to provide an obviously missing feature of this diagram: the position of the antiferromagnetic critical curve. This curve turns out to possess a bifurcation point with two branches emerging from it, entailing important consequences for the global phase diagram. We have obtained accurate numerical estimates for the position of this curve by combining the transfer-matrix approach for strip graphs with toroidal boundary conditions and the recent method of critical polynomials. The second goal of this work is to study the corresponding Ap-1 RSOS model on the torus, for integer p=4, 5, \\ldots, 8 . We clarify its relation to the corresponding Potts model, in particular concerning the role of boundary conditions. For certain values of p, we identify several new critical points and regimes for the RSOS model and we initiate the study of the flows between the corresponding field theories.

  3. Understanding the H -T phase diagram of the monoaxial helimagnet

    Science.gov (United States)

    Laliena, Victor; Campo, Javier; Kousaka, Yusuke

    2016-09-01

    Some unexpected features of the phase diagram of the monoaxial helimagnet in presence of an applied magnetic field perpendicular to the chiral axis are theoretically predicted. A rather general Hamiltonian with long-range Heisenberg exchange and Dzyaloshinskii-Moriya interactions is considered. The continuum limit simplifies the free energy, which contains only a few parameters which in principle are determined by the many parameters of the Hamiltonian, although in practice they may be tuned to fit the experiments. The phase diagram contains a chiral soliton lattice phase and a forced ferromagnetic phase separated by a line of phase transitions, which are of second order at low T and of first order in the vicinity of the zero-field ordering temperature, and are separated by a tricritical point. A highly nonlinear chiral soliton lattice, in which many harmonics contribute appreciably to the spatial modulation of the local magnetic moment, develops only below the tricritical temperature, and in this case, the scaling shows a logarithmic behavior similar to that at T =0 , which is a universal feature of the chiral soliton lattice. Below the tricritical temperature, the normalized soliton density curves are found to be independent of T , in agreement with the experimental results of magnetorresistance curves, while above the tricritical temperature they show a noticeable temperature dependence. The implications in the interpretation of experimental results of CrNb3S6 are discussed.

  4. Ternary Phase Diagrams that Relate to the Plutonium Immobilization Ceramic

    Energy Technology Data Exchange (ETDEWEB)

    Ebbinghaus, B b; Krikorian, O H; Vance, E R; Stewart, M W

    2001-01-01

    The plutonium immobilization ceramic consists primarily of a pyrochlore titanate phase of the approximate composition Ca{sub 0.97}Hf{sub 0.17}Pu{sub 0.22}U{sub 0.39}Gd{sub 0.24} Ti{sub 2}O{sub 7}. In this study, a series of ternary phase diagrams was constructed to evaluate the relationship of various titanate phases (e.g., brannerite, zirconolite-2M, zirconolite-4M, and perovskite) to pyrochlore titanates, usually in the presence of excess TiO{sub 2} (rutile), and at temperatures in the vicinity of 1350 C. To facilitate the studies, U, Th, and Ce were used as surrogates for Pu in a number of the phase diagrams in addition to the use of Pu itself. The effects of impurity oxides, Al{sub 2}O{sub 3} and MgO, were also studied on pyrochlore (Gd{sub 2}Ti{sub 2}O{sub 7}) and zirconolite (CaHfTi{sub 2}O{sub 7}) mixtures. Either electron microprobe (at Lawrence Livermore National Laboratory) or quantitative SEM-EDS (at Australian Nuclear Science and Technology Organization) were used to evaluate the compositions of the phases.

  5. UPS Delivers Optimal Phase Diagram in High Dimensional Variable Selection

    CERN Document Server

    Ji, Pengsheng

    2010-01-01

    Consider linear regression in the so-called regime of p much larger than n. We propose the UPS as a new variable selection method. This is a Screen and Clean procedure [Wasserman and Roeder (2009)], in which we screen with the Univariate thresholding, and clean with the Penalized MLE. In many situations, the UPS possesses two important properties: Sure Screening and Separable After Screening (SAS). These properties enable us to reduce the original regression problem to many small-size regression problems that can be fitted separately. We measure the performance of variable selection procedure by the Hamming distance. In many situations, we find that the UPS achieves the optimal rate of convergence, and also yields an optimal partition of the so-called phase diagram. In the two-dimensional phase space calibrated by the signal sparsity and signal strength, there is a three-phase diagram shared by many choices of design matrices. In the first phase, it is possible to recover all signals. In the second phase, exa...

  6. Research data supporting "Determining pressure-temperature phase diagrams of materials"

    OpenAIRE

    Baldock, Robert J.N.; Partay, Livia B.; Bartok, Albert P.; Payne, Michael C.; Csanyi, Gabor

    2016-01-01

    Pressure-temperature phase diagrams of the Lennard-Jones system, aluminium and nickel titanium as reported in the paper "Determining pressure-temperature phase diagrams of materials", together with example nested sampling output for aluminium and nickel titanium calculations. This research data supports “Determining pressure-temperature phase diagrams of materials” which has been published in “Physical Review B”. Research data supporting “Determining pressure-temperature phase diagrams...

  7. Materials Research Society Symposia Proceedings, Volume 19. Alloy Phase Diagrams Held November 1982 in Boston, Massachusetts.

    Science.gov (United States)

    Alloys, * Phase diagrams , *Symposia, Stability, Thermodynamic properties, Models, Solidification, Chemical equilibrium, Microstructure, Metallurgy, Structural analysis, Research management, Materials

  8. Quarks and gluons in the phase diagram of quantum chromodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Welzbacher, Christian Andreas

    2016-07-14

    In this dissertation we study the phase diagram of strongly interacting matter by approaching the theory of quantum chromodynamics in the functional approach of Dyson-Schwinger equations. With these quantum (field) equations of motions we calculate the non-perturbative quark propagator within the Matsubara formalism. We built up on previous works and extend the so-called truncation scheme, which is necessary to render the infinite tower of Dyson-Schwinger equations finite and study phase transitions of chiral symmetry and the confinement/deconfinement transition. In the first part of this thesis we discuss general aspects of quantum chromodynamics and introduce the Dyson-Schwinger equations in general and present the quark Dyson-Schwinger equation together with its counterpart for the gluon. The Bethe-Salpeter equation is introduced which is necessary to perform two-body bound state calculations. A view on the phase diagram of quantum chromodynamics is given, including the discussion of order parameter for chiral symmetry and confinement. Here we also discuss the dependence of the phase structure on the masses of the quarks. In the following we present the truncation and our results for an unquenched N{sub f} = 2+1 calculation and compare it to previous studies. We highlight some complementary details for the quark and gluon propagator and discus the resulting phase diagram, which is in agreement with previous work. Results for an equivalent of the Columbia plot and the critical surface are discussed. A systematically improved truncation, where the charm quark as a dynamical quark flavour is added, will be presented in Ch. 4. An important aspect in this investigation is the proper adjustment of the scales. This is done by matching vacuum properties of the relevant pseudoscalar mesons separately for N{sub f} = 2+1 and N f = 2+1+1 via a solution of the Bethe-Salpeter equation. A comparison of the resulting N{sub f} = 2+1 and N{sub f} = 2+1+1 phase diagram indicates

  9. Phase diagram and entanglement of two interacting topological Kitaev chains

    Science.gov (United States)

    Herviou, Loïc; Mora, Christophe; Le Hur, Karyn

    2016-04-01

    A superconducting wire described by a p -wave pairing and a Kitaev Hamiltonian exhibits Majorana fermions at its edges and is topologically protected by symmetry. We consider two Kitaev wires (chains) coupled by a Coulomb-type interaction and study the complete phase diagram using analytical and numerical techniques. A topological superconducting phase with four Majorana fermions occurs until moderate interactions between chains. For large interactions, both repulsive and attractive, by analogy with the Hubbard model, we identify Mott phases with Ising-type magnetic order. For repulsive interactions, the Ising antiferromagnetic order favors the occurrence of orbital currents spontaneously breaking time-reversal symmetry. By strongly varying the chemical potentials of the two chains, quantum phase transitions towards fully polarized (empty or full) fermionic chains occur. In the Kitaev model, the quantum critical point separating the topological superconducting phase and the polarized phase belongs to the universality class of the critical Ising model in two dimensions. When increasing the Coulomb interaction between chains, then we identify an additional phase corresponding to two critical Ising theories (or two chains of Majorana fermions). We confirm the existence of such a phase from exact mappings and from the concept of bipartite fluctuations. We show the existence of negative logarithmic corrections in the bipartite fluctuations, as a reminiscence of the quantum critical point in the Kitaev model. Other entanglement probes such as bipartite entropy and entanglement spectrum are also used to characterize the phase diagram. The limit of large interactions can be reached in an equivalent setup of ultracold atoms and Josephson junctions.

  10. Phase diagram determination up to 823K in minerals using Diamond Anvil Cell

    Science.gov (United States)

    Raju, S. V.; Knight, J.; Pawley, A. R.; Clark, S. M.

    2008-12-01

    : The ruby fluorescence technique is widely used for pressure measurement inside the diamond anvil cell. However, at higher temperatures estimation of pressure becomes complex due to the broadening of the fluorescence peaks. There are other fluorescence markers upon which temperature has a lower effect. For example Sm: SrB2O7. Here, we present a high pressure - high temperature calibration of Samarium doped SrB2O7. In order to minimize the error in determining the pressure, Strontium Borate along with Ruby were loaded in diamond anvil cell under hydrostatic conditions and fluorescence measurements were carried out upto temperatures of 823K under pressure. An equation routine is obtained to fit the peaks at various temperatures upto 823K under pressure. Using this data for pressure determination, phase diagram of Lawsonite was studied and the results are discussed.

  11. High-pressure Raman investigations of phase transformations in pentaerythritol (C(CH sub 2 OH) sub 4)

    CERN Document Server

    Bhattacharya, T

    2002-01-01

    Our high-pressure Raman scattering experiments on pentaerythritol (C(CH sub 2 OH) sub 4) show that this compound undergoes at least three phase transformations up to 25 GPa. Splitting of various modes at approx 6.3, approx 8.2 and 10 GPa suggests that these phase transformations result in lowering of crystalline symmetry. A very small discontinuous change in slope of most of the Raman-active modes is observed at 0.3 GPa. However, no other signature of a phase transition was observed at this pressure. The observed correlation of the pressures for the onset of the two phase transformations with the limiting values of the distances between various non-bonded atoms in the parent phase suggests that the molecular rearrangements across the phase transformations are not very drastic. In addition, our earlier Fourier transform infrared and present Raman investigations indicate that high-pressure compression leads to increase in strength of the hydrogen bond present in this compound.

  12. Ionic and superionic phases in ammonia dihydrate N H3.2 H2O under high pressure

    Science.gov (United States)

    Jiang, Xue; Wu, Xue; Zheng, Zhaoyang; Huang, Yingying; Zhao, Jijun

    2017-04-01

    Water and ammonia have long been seen as the main species of extraterrestrial space, especially on solar giants, moons, comets, and numerous extrasolar planets. The phases formed by their admixtures under temperature and pressure conditions of the giant planets are important for understanding many observable properties (gravitational moments, atmospheric composition, and magnetic field). Here we employ a Monte Carlo packing algorithm combined with first-principles calculations to search the low-energy crystal structures of ammonia dihydrate (ADH). At high pressure above 11.81 GPa, we predict an unusual ionic phase (tetragonal, I 41c d ) consisting of three alternating layers of H2O ,NH4+ , and O H- . The occurrence of ionic phase is attributed to the NH4+ and O H- electrostatic interaction induced volume reduction, which lowers the energy barrier of molecular to ionic phase transition. Analysis of proton transfer under pressure further supports the transformation mechanism between molecular and ionic phase. According to the mobility of hydrogen atoms from ab initio molecular dynamics, this ionic crystal will transform into a superionic phase under high temperature and high pressure. The existence of ionic or superionic ADH may have important implications for understanding the interiors of Neptune, Uranus, and many extrasolar planets.

  13. Misfit strain phase diagrams of epitaxial PMN–PT films

    Energy Technology Data Exchange (ETDEWEB)

    Khakpash, N.; Khassaf, H.; Rossetti, G. A. [Department of Materials Science and Engineering and Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269 (United States); Alpay, S. P., E-mail: p.alpay@ims.uconn.edu [Department of Materials Science and Engineering and Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269 (United States); Department of Physics, University of Connecticut, Storrs, Connecticut 06269 (United States)

    2015-02-23

    Misfit strain–temperature phase diagrams of three compositions of (001) pseudocubic (1 − x)·Pb (Mg{sub l/3}Nb{sub 2/3})O{sub 3} − x·PbTiO{sub 3} (PMN–PT) thin films are computed using a phenomenological model. Two (x = 0.30, 0.42) are located near the morphotropic phase boundary (MPB) of bulk PMN–PT at room temperature (RT) and one (x = 0.70) is located far from the MPB. The results show that it is possible to stabilize an adaptive monoclinic phase over a wide range of misfit strains. At RT, the stability region of this phase is much larger for PMN–PT compared to barium strontium titanate and lead zirconate titanate films.

  14. Misfit strain phase diagrams of epitaxial PMN-PT films

    Science.gov (United States)

    Khakpash, N.; Khassaf, H.; Rossetti, G. A.; Alpay, S. P.

    2015-02-01

    Misfit strain-temperature phase diagrams of three compositions of (001) pseudocubic (1 - x).Pb (Mgl/3Nb2/3)O3 - x.PbTiO3 (PMN-PT) thin films are computed using a phenomenological model. Two (x = 0.30, 0.42) are located near the morphotropic phase boundary (MPB) of bulk PMN-PT at room temperature (RT) and one (x = 0.70) is located far from the MPB. The results show that it is possible to stabilize an adaptive monoclinic phase over a wide range of misfit strains. At RT, the stability region of this phase is much larger for PMN-PT compared to barium strontium titanate and lead zirconate titanate films.

  15. Phase diagrams and heterogeneous equilibria a practical introduction

    CERN Document Server

    Predel, Bruno; Pool, Monte

    2004-01-01

    This graduate-level textbook provides an introduction to the practical application of phase diagrams. It is intended for students and researchers in chemistry, metallurgy, mineralogy, and materials science as well as in engineering and physics. Heterogeneous equilibria are described by a minimum of theory illustrated by practical examples and realistic case discussions from the different fields of application. The treatment of the physical and energetic background of phase equilibria leads to the discussion of the thermodynamics of mixtures and the correlation between energetics and composition. Thus, tools for the prediction of energetic, structural, and physical quantities are provided. The authors treat the nucleation of phase transitions, the production and stability of technologically important metastable phases, and metallic glasses. Furthermore, the text also concisely presents the thermodynamics and composition of polymer systems.

  16. Moving through three-dimensional phase diagrams of monoclonal antibodies.

    Science.gov (United States)

    Rakel, Natalie; Baum, Miriam; Hubbuch, Jürgen

    2014-01-01

    Protein phase behavior characterization is a multivariate problem due to the high amount of influencing parameters and the diversity of the proteins. Single influences on the protein are not understood and fundamental knowledge remains to be obtained. For this purpose, a systematic screening method was developed to characterize the influence of fluid phase conditions on the phase behavior of proteins in three-dimensional phase diagrams. This approach was applied to three monoclonal antibodies to investigate influences of pH, protein and salt concentrations, with five different salts being tested. Although differences exist between the antibodies, this extensive study confirmed the general applicability of the Hofmeister series over the broad parameter range analyzed. The influence of the different salts on the aggregation (crystallization and precipitation) probability was described qualitatively using this Hofmeister series, with a differentiation between crystallization and precipitation being impossible, however.

  17. METHODOLOGICAL NOTES: Metastable phases, phase transformations, and phase diagrams in physics and chemistry

    Science.gov (United States)

    Brazhkin, Vadim V.

    2006-07-01

    Concepts of a 'phase' and a 'phase transition' are discussed for stable and metastable states of matter. While condensed matter physics primarily considers equilibrium states and treats metastable phases as exceptions, organic chemistry overwhelmingly deals with metastable states. It is emphasized that many simple light-element compounds — including most hydrocarbons; nitrogen oxides, hydrides, and carbides; carbon monoxide CO; alcohols and glycerin — are also metastable at normal pressure in the sense that they do not correspond to a minimum Gibbs free energy for a given chemical composition. At moderate temperatures and pressures, the phase transformations for these metastable phases are reversible with the fulfilment of all laws of equilibrium thermodynamics over the entire range of experimentally accessible times. At sufficiently high pressures (> 1-10 GPa), most of the metastable molecular phases irreversibly transform to lower-energy polymer phases, stable or metastable. These transitions do not correspond to the equality of the Gibbs free energy for the involved phases before and after the transition and so they are not first-order in the 'classical' sense. At normal pressure, the resulting polymer phases can exist at temperatures above the melting point of the original metastable molecular phase, as the examples of polyethylene and polymerized CO dramatically illustrate. As pressure is increased further to 20-50 GPa, the PV contribution to Gibbs free energy gives rise to stable high-density atomic phases. Many of the intermediate-energy polymer phases can likely be synthesized by methods of 'classical' chemistry at normal pressure.

  18. Theoretical Study of the High-Pressure Isosymmetric Phase Transition in Lead Fluoride, PbF2

    Science.gov (United States)

    Dutta, R.; Stan, C. V.; White, C.; Duffy, T. S.

    2016-12-01

    Under compression many AX2 compounds including the alkaline earth fluorides follow a canonical transition sequence from the fluorite-type (Coordination Number, CN = 8) to the cotunnite-type (CN = 9) to the Ni2In-type phase (CN = 11). Lead fluoride is instead reported to undergo an unusual isosymmetric phase transition from the cotunnite phase to a "Co2Si-like" phase (9-fold coordination) at 10 GPa1. Previous theoretical calculations2 have reported that the Ni2In-type structure should be stable, but this phase has not been observed experimentally. In our previous experimental study, we examined the high-pressure behavior of PbF2 using in-situ synchrotron x-ray diffraction to 70 GPa. Here we use theoretical density functional theory calculations to better understand the high-pressure behavior of this material. The calculated lattice parameters display highly anomalous trends from 9-21 GPa, consistent with experiments. Experimental evidence for a transition to a Co2Si-like phase was based solely on lattice parameter systematics. Here we use electron density calculations, to directly show that the high-pressure phase is Co2Si-type. Our calculations also reveal the detailed atomic rearrangements associated with the development of an extra Pb-F bond in the high-pressure phase. At P > 9 GPa, both the lead and fluorine ions begin to reorient themselves as an additional fluorine atom, initially outside the 9-fold coordination polyhedron of cotunnite, approaches it. The transition regime from 9 to 21 GPa is marked by continuous atomic movements leading to anomalous behavior of the lattice parameters and compressibilities. At P 21 GPa, the transformation to the Co2Si-type structure is completed with an increase in the coordination number from 9 to 10. References1Haines, J. M. Léger, and O. Schulte, Phys. Rev. B 57, 7551 (1998). 2A. Costales, M. A. Blanco, R. Pandey, and J. M. Recio, Phys. Rev. B 61, 11359 (2000). 3W. Jeitschko, Acta Crystallogr. Sect. B 24, 930 (1968).

  19. The phase diagram of twisted mass lattice QCD

    CERN Document Server

    Sharpe, S R; Sharpe, Stephen R.; Wu, Jackson M. S.

    2004-01-01

    We use the effective chiral Lagrangian to analyze the phase diagram of two-flavor twisted mass lattice QCD as a function of the normal and twisted masses, generalizing previous work for the untwisted theory. We first determine the chiral Lagrangian including discretization effects up to next-to-leading order (NLO) in a combined expansion in which m_\\pi^2/(4\\pi f_\\pi)^2 ~ a \\Lambda (a being the lattice spacing, and \\Lambda = \\Lambda_{QCD}). We then focus on the region where m_\\pi^2/(4\\pi f_\\pi)^2 ~ (a \\Lambda)^2, in which case competition between leading and NLO terms can lead to phase transitions. As for untwisted Wilson fermions, we find two possible phase diagrams, depending on the sign of a coefficient in the chiral Lagrangian. For one sign, there is an Aoki phase for pure Wilson fermions, with flavor and parity broken, but this is washed out into a crossover if the twisted mass is non-vanishing. For the other sign, there is a first order transition for pure Wilson fermions, and we find that this transitio...

  20. A new experimental setup for the liquid-solid phase transition determination in crude oils under high pressure conditions

    Energy Technology Data Exchange (ETDEWEB)

    A. Rizzo; H. Carrier; J. Castillo; S. Acevedo; J. Pauly [UNEXPO - Vicerectorado Barquisimeto (Venezuela). Departamento de Ingeniera Quimica

    2007-08-15

    A high pressure apparatus based on two sapphire windows high pressure cell coupled with a detection system of the reflected and refracted light intensities coming from a laser beam was designed to determine the phase transitions by the measurement of the light intensity change. The setup was used to measure the wax disappearance temperature under pressure up to 100 MPa in pure component, synthetic complex mixtures made up of distributions of n-paraffins ranging from n-C{sub 20} to n-C{sub 42}. Finally a real stabilized condensate was successfully investigated and the sensitivity of the detection system was demonstrated on a dark crude oil. 30 refs., 10 figs., 1 tab.

  1. Influence of the high pressure torsion die geometry on the allotropic phase transformations in pure Zr

    Energy Technology Data Exchange (ETDEWEB)

    Zhilyaev, A.P. [Centro Nacional de Investigaciones Metalurgicas (CENIM), CSIC, 28040 Madrid (Spain); Institute for Metals Superplasticity Problems, RAS, 450001 Ufa (Russian Federation); Galvez, F. [ETS Ingenieros de Caminos, Universidad Politecnica de Madrid, 28040 Madrid (Spain); Sharafutdinov, A. [Innovation Scientific Technology Center ' Iskra' , 450000 Ufa (Russian Federation); Perez-Prado, M.T., E-mail: teresa.perez.prado@imdea.org [Madrid Institute for Advanced Studies of Materials (IMDEA-Materials), C/Profesor Aranguren s/n, 28040 Madrid (Spain)

    2010-06-25

    The effect of the press geometry in the {alpha} to {omega} + {beta} transformation in pure Zr by high pressure torsion (HPT) was investigated. Specimens were processed in constrained and unconstrained setups using a wide range of applied pressures and 5 anvil turns. The resulting microstructures were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM and HRTEM) and electron backscatter diffraction (EBSD). Microhardness distributions were measured for each condition. The transformation kinetics and the stability of the fabricated nanostructures are enhanced when using an unconstrained setup. In the samples processed by constrained HPT the full transformation does not take place even at the highest pressures applied. Additionally, post-processing room temperature grain growth of some of the remaining nanocrystalline {alpha}-Zr grains with (0 0 0 1) orientations occurs, leading to a significant decrease in hardness. HRTEM allowed confirming the presence of pure {beta}-Zr.

  2. Structural analysis of a high-pressure amorphous phase of SnI sub 4

    CERN Document Server

    Ohmura, A; Sato, K; Ogawa, C; Isshiki, M; Ohishi, Y

    2002-01-01

    We have performed a high-pressure synchrotron x-ray diffraction study of a metallic amorphous state in SnI sub 4 induced by pressure. The Faber-Ziman structure factor S(Q) was obtained from diffraction intensities measured at pressures between 25 and 65 GPa. The first peak in S(Q) is relatively intense and sharp and the second peak is overlapped with the third one. Such features are also found in S(Q) for pure metallic glasses of Ni and Fe at 1 atm but not in molecular liquids. The obtained reduced radial distribution function g(r) shows no evidence for the presence of the SnI sub 4 molecules in the metallic amorphous state.

  3. Structural and magnetic phase transitions in gadolinium under high pressures and low temperatures

    Science.gov (United States)

    Samudrala, Gopi K.; Tsoi, Georgiy M.; Weir, Samuel T.; Vohra, Yogesh K.

    2014-10-01

    High pressure structural transition studies have been carried out on rare earth metal gadolinium in a diamond anvil cell at room temperature to 169 GPa. Gadolinium has been compressed to 38% of its initial volume at this pressure. With increasing pressure, a crystal structure sequence of hcp → Sm-type → dhcp → fcc → dfcc → monoclinic has been observed in our studies on gadolinium. The measured equation of state of gadolinium is presented to 169 GPa at ambient temperature. Magnetic ordering temperature of gadolinium has been studied using designer diamond anvils to a pressure of 25 GPa and a temperature of 10 K. The magnetic ordering temperature has been determined from the four-point electrical resistivity measurements carried out on gadolinium. Our experiments show that the magnetic transition temperature decreases with increasing pressure to 19 GPa and then increases when gadolinium is subjected to higher pressures.

  4. High-pressure phase equilibria for the carbon dioxide + 3-pentanol and carbon dioxide + 3-pentanol + water systems

    Energy Technology Data Exchange (ETDEWEB)

    Lee, H.S.; Mun, S.Y.; Lee, H. [Korea Advanced Inst. of Science and Technology, Taejon (Korea, Republic of). Dept. of Chemical Engineering

    1999-05-01

    High-pressure vapor-liquid equilibria for the binary carbon dioxide + 3-pentanol system were measured at 313.2 K. The phase equilibrium apparatus used in this work was of the circulation type in which the coexisting phases were recirculated, on-line sampled, and analyzed. The critical pressure and corresponding mole fraction of carbon dioxide at 313.2 K were found to be 8.22 MPa and 0.974, respectively, for this binary system. The phase equilibria for the ternary carbon dioxide + 3-pentanol + water system were also measured at 313.2 K and pressures of 2.00, 4.00, 6.00, 8.00, and 8.25 MPa. This ternary system showed the liquid-liquid-vapor (LLV) phase behavior over the range of pressure up to the critical pressure of 8.25 MPa. The binary equilibrium data were all reasonably well-correlated with the Redlich-Kwong, Soave-Redlich-Kwong, Peng-Robinson, and Patel-Teja equations of state incorporated with the eight different mixing rules: the van der Waals, Panagiotopoulos-Reic, and six modified Huron-Vidal mixing rules with UNIQUAC parameters. For the prediction of high-pressure phase equilibria for the systems containing carbon dioxide and alcohols, the SRK-MHV2 might reproduce many features of the measured behavior although further tests are needed with other systems.

  5. A first principles study of phase stability, bonding, electronic and lattice dynamical properties of beryllium chalcogenides at high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Dabhi, Shweta [Department of Physics, Maharaja Krishnakumarsinhji Bhavnagar University, Bhavnagar 364001 (India); Mankad, Venu [Central Institute of Plastic Engineering and Technology, Ahmedabad (India); Jha, Prafulla K., E-mail: prafullaj@yahoo.com [Department of Physics, Faculty of Science, The M.S. University of Baroda, Vadodara 390002 (India)

    2014-12-25

    Highlights: • First principles calculations are performed for BeS, BeSe and BeTe in B3, B8 and B1 phases. • They are indirect wide band gap semiconductors stable in B3 phase at ambient condition. • Phonon calculations at ambient and high pressure are reported. • The NiAs phase is dynamically stable at high pressure. - Abstract: The present paper reports a detailed and systematic theoretical study of structural, mechanical, electronic, vibrational and thermodynamical properties of three beryllium chalcogenides BeS, BeSe and BeTe in zinc blende, NiAs and rock salt phases by performing ab initio calculations based on density-functional theory. The calculated value of lattice constants and bulk modulus are compared with the available experimental and other theoretical data and found to agree reasonably well. These compounds are indirect wide band gap semiconductors with a partially ionic contribution in all considered three phases. The zinc blende phase of these chalcogenides is found stable at ambient condition and phase transition from zinc blende to NiAs structure is found to occur. The bulk modulus, its pressure derivative, anisotropic factor, Poission’s ratio, Young’s modulus for these are also calculated and discussed. The phonon dispersion curves of these beryllium chalcogenides in zinc blende phase depict their dynamical stability in this phase at ambient condition. We have also estimated the temperature variation of specific heat at constant volume, entropy and Debye temperature for these compounds in zinc blende phase. The variation of lattice-specific heat with temperature obeys the classical Dulong–Petit’s law at high temperature, while at low-temperature it obeys the Debye’s T{sup 3} law.

  6. Comparison of actual vs synthesized ternary phase diagrams for solutes of cryobiological interest☆

    OpenAIRE

    F W Kleinhans; Mazur, Peter

    2007-01-01

    Phase diagrams are of great utility in cryobiology, especially those consisting of a cryoprotective agent (CPA) dissolved in a physiological salt solution. These ternary phase diagrams consist of plots of the freezing points of increasing concentrations of solutions of cryoprotective agents (CPA) plus NaCl. Because they are time-consuming to generate, ternary diagrams are only available for a small number of CPA's. We wanted to determine whether accurate ternary phase diagrams could be synthe...

  7. ({alpha},{eta}) phase diagrams in tilted chiral smectics

    Energy Technology Data Exchange (ETDEWEB)

    Rjili, M., E-mail: medrjili@yahoo.fr [Laboratoire de Physique de la Matiere Molle et de la Modelisation Electromagnetique, Faculte des Sciences de Tunis, Universite Tunis El Manar, 2092 El Manar Tunis (Tunisia); Marcerou, J.P., E-mail: marcerou@crpp-bordeaux.cnrs.fr [Centre de Recherches Paul Pascal, 115, Av. Albert-Schweitzer, 33600 Pessac (France); Gharbi, A.; Othman, T. [Laboratoire de Physique de la Matiere Molle et de la Modelisation Electromagnetique, Faculte des Sciences de Tunis, Universite Tunis El Manar, 2092 El Manar Tunis (Tunisia)

    2013-02-01

    The polymorphism of tilted chiral smectics liquid crystals is incredibly rich and encompasses many subphases such as SmC{sub A}{sup Low-Asterisk }; SmC{sub Fi1}{sup Low-Asterisk }; SmC{sub Fi2}{sup Low-Asterisk }; SmC{sup Low-Asterisk }; SmC{sub {alpha}}{sup Low-Asterisk }. The continuum theory established by Marcerou (2010) is used to derive an expression for the free energy density of those subphases. The minimization of this free energy is obtained through a combination of analytical and numerical methods. It leads to a phase diagram built in the ({alpha},{eta}) plane where {alpha} is local angular parameter and {eta} describes the variation of the temperature. From this graphical representation, many experimentally observed phase sequences of ferroelectric liquid crystals can be explained, even them including subphases which were recently observed like the SmC{sub 5}{sup Low-Asterisk} and the SmC{sub 6}{sup Low-Asterisk} ones. However, it should be emphasized that the details of predicted phase diagram are strongly dependent on the compound studied.

  8. Essential Magnesium Alloys Binary Phase Diagrams and Their Thermochemical Data

    Directory of Open Access Journals (Sweden)

    Mohammad Mezbahul-Islam

    2014-01-01

    Full Text Available Magnesium-based alloys are becoming a major industrial material for structural applications because of their potential weight saving characteristics. All the commercial Mg alloys like AZ, AM, AE, EZ, ZK, and so forth series are multicomponent and hence it is important to understand the phase relations of the alloying elements with Mg. In this work, eleven essential Mg-based binary systems including Mg-Al/Zn/Mn/Ca/Sr/Y/Ni/Ce/Nd/Cu/Sn have been reviewed. Each of these systems has been discussed critically on the aspects of phase diagram and thermodynamic properties. All the available experimental data has been summarized and critically assessed to provide detailed understanding of the systems. The phase diagrams are calculated based on the most up-to-date optimized parameters. The thermodynamic model parameters for all the systems except Mg-Nd have been summarized in tables. The crystallographic information of the intermetallic compounds of different binary systems is provided. Also, the heat of formation of the intermetallic compounds obtained from experimental, first principle calculations and CALPHAD optimizations are provided. In addition, reoptimization of the Mg-Y system has been done in this work since new experimental data showed wider solubility of the intermetallic compounds.

  9. The QCD phase diagram from Schwinger-Dyson Equations

    CERN Document Server

    Gutierrez, Enif; Ayala, Alejandro; Bashir, Adnan; Raya, Alfredo

    2013-01-01

    We study the phase diagram of quantum chromodynamics (QCD). For this purpose we employ the Schwinger-Dyson equations (SDEs) technique and construct a truncation of the infinite tower of equations by demanding a matching with the lattice results for the quark-anti-quark condensate at finite temperature (T), for zero quark chemical potential (mu), that is, the region where lattice calculations are expected to provide reliable results. We compute the evolution of the phase diagram away from T=0 for increasing values of the chemical potential by following the evolution of the heat capacity as a function of T and mu. The behavior of this thermodynamic variable clearly demonstrates the existence of a cross-over for mu less than a critical value. However, the heat capacity develops a singularity near mu approx 0.22 GeV marking the onslaught of a first order phase transition characterized by the existence of a critical point. The critical line continues until mu approx 0.53 GeV where Tc=0 and thus chiral symmetry is ...

  10. Phase Diagrams of Instabilities in Compressed Film-Substrate Systems.

    Science.gov (United States)

    Wang, Qiming; Zhao, Xuanhe

    2014-05-01

    Subject to a compressive membrane stress, an elastic film bonded on a substrate can become unstable, forming wrinkles, creases or delaminated buckles. Further increasing the compressive stress can induce advanced modes of instabilities including period-doubles, folds, localized ridges, delamination, and coexistent instabilities. While various instabilities in film-substrate systems under compression have been analyzed separately, a systematic and quantitative understanding of these instabilities is still elusive. Here we present a joint experimental and theoretical study to systematically explore the instabilities in elastic film-substrate systems under uniaxial compression. We use the Maxwell stability criterion to analyze the occurrence and evolution of instabilities analogous to phase transitions in thermodynamic systems. We show that the moduli of the film and the substrate, the film-substrate adhesion strength, the film thickness, and the prestretch in the substrate determine various modes of instabilities. Defects in the film-substrate system can facilitate it to overcome energy barriers during occurrence and evolution of instabilities. We provide a set of phase diagrams to predict both initial and advanced modes of instabilities in compressed film-substrate systems. The phase diagrams can be used to guide the design of film-substrate systems to achieve desired modes of instabilities.

  11. Phase Diagram of Antiferromagnetically Exchange-Coupled Bilayer

    Institute of Scientific and Technical Information of China (English)

    GUO Guang-Hua; ZHANG Guang-Fu; SUN Li-Yuan; Peter A. J. de Groot

    2008-01-01

    Magnetic hysteresis properties of antiferromagnetically exchange-coupled bilayer structures, in which the two magnetic layers have different magnetic parameters and thicknesses, are studied within the framework of the Stoner-Wohifarth model. Analytical expressions for the switching fields corresponding to the linear magnetic states are obtained. By adjusting the magnetic parameters or thicknesses of layers, nine different types of easyaxis hysteresis loops may exist. The phase diagram of easy-axis hysteresis loops is mapped in the k,1 and k,2 plane, where k,1 and k,2 are the ratios of magnetic anisotropy to the interlayer exchange coupling of the two magnetic layers, respectively.

  12. Simple thermodynamic model for the hydrogen phase diagram

    Science.gov (United States)

    Magdǎu, Ioan B.; Marqués, Miriam; Borgulya, Balint; Ackland, Graeme J.

    2017-03-01

    We describe a classical thermodynamic model that reproduces the main features of the solid hydrogen phase diagram. In particular, we show how the general structure types, which are found by electronic structure calculations and the quantum nature of the protons, can also be understood from a classical viewpoint. The model provides a picture not only of crystal structure, but also for the anomalous melting curve and insights into isotope effects, liquid metallisation, and infrared activity. The existence of a classical picture for this most quantum of condensed matter systems provides a surprising extension of the correspondence principle of quantum mechanics, in particular the equivalent effects of classical and quantum uncertainty.

  13. Edge states and phase diagram for graphene under polarized light

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yi-Xiang, E-mail: wangyixiang@jiangnan.edu.cn [School of Science, Jiangnan University, Wuxi 214122 (China); Li, Fuxiang [Center for Nonlinear Studies and Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    2016-07-01

    In this work, we investigate the topological phase transitions in graphene under the modulation of circularly polarized light, by analyzing the changes of edge states and its topological structures. A full phase diagram, with several different topological phases, is presented in the parameter space spanned by the driving frequency and light strength. We find that the high-Chern number behavior is very common in the driven system. While the one-photon resonance can create the chiral edge states in the π-gap, the two-photon resonance will induce the counter-propagating edge modes in the zero-energy gap. When the driving light strength is strong, the number and even the chirality of the edge states may change in the π-gap. The robustness of the edge states to disorder potential is also examined. We close by discussing the feasibility of experimental proposals.

  14. Two-phase convection in the high-pressure ice layer of the large icy moons: geodynamical implications

    Science.gov (United States)

    Kalousova, K.; Sotin, C.; Tobie, G.; Choblet, G.; Grasset, O.

    2015-12-01

    The H2O layers of large icy satellites such as Ganymede, Callisto, or Titan probably include a liquid water ocean sandwiched between the deep high-pressure ice layer and the outer ice I shell [1]. It has been recently suggested that the high-pressure ice layer could be decoupled from the silicate core by a salty liquid water layer [2]. However, it is not clear whether accumulation of liquids at the bottom of the high-pressure layer is possible due to positive buoyancy of water with respect to high-pressure ice. Numerical simulation of this two-phase (i.e. ice and water) problem is challenging, which explains why very few studies have self-consistently handled the presence and transport of liquids within the solid ice [e.g. 3]. While using a simplified description of water production and transport, it was recently showed in [4] that (i) a significant fraction of the high-pressure layer reaches the melting point and (ii) the melt generation and its extraction to the overlying ocean significantly influence the global thermal evolution and interior structure of the large icy moons.Here, we treat the high-pressure ice layer as a compressible mixture of solid ice and liquid water [5]. Several aspects are investigated: (i) the effect of the water formation on the vigor of solid-state convection and its influence on the amount of heat that is transferred from the silicate mantle to the ocean; (ii) the fate of liquids within the upper thermal boundary layer - whether they freeze or reach the ocean; and (iii) the effect of salts and volatile compounds (potentially released from the rocky core) on the melting/freezing processes. Investigation of these aspects will allow us to address the thermo-chemical evolution of the internal ocean which is crucial to evaluate the astrobiological potential of large icy moons. This work has been performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract to NASA. [1] Hussmann et al. (2007), Treatise of

  15. Existence domains for invariant reactions in binary regular solution phase diagrams exhibiting two phases

    Indian Academy of Sciences (India)

    B Nageswara Sarma; S Srinivas Prasad; S Vijayvergiya; V Bharath Kumar; S Lele

    2003-06-01

    The thermodynamic origin of various types of phase diagrams in simple binary systems exhibiting two phases (e.g. a liquid and a solid phase) has been examined using the regular solution model. The necessary conditions for the occurrence of each of these types are identified in terms of the appropriate intersections of the miscibility gap boundaries (in solid/liquid phases) and the liquidus/solidus/iso- curves. Thus, the regions of occurrence of the different types of possible phase diagrams in the space of the regular solution interchange energy parameters (, ) are clearly delineated. This analysis makes it easier to make intelligent initial selections of model (energy) parameters for their optimization in the calculation of phase diagrams using thermodynamic models such as CALPHAD/CVM.

  16. Density-functional approach to the valence change in SmS: Normal and high-pressure phases

    Science.gov (United States)

    Schumann, R.; Richter, M.; Steinbeck, L.; Eschrig, H.

    1995-09-01

    The electronic structure of SmS in dependence of the lattice constant is calculated by means of density-functional theory. The local-density approximation (LDA) to the exchange and correlation potential is employed. The 4f electrons, however, are treated in three different ways, viz., (i) as localized core states, (ii) as extended band states, and (iii) as self-interaction corrected (SIC) band states. While the experimentally observed Sm valency of normal state SmS (black phase) cannot be described by methods (i) and (ii) the SIC calculations are consistent with the measured value. For pressures above 30 kbar, method (ii) agrees well with the observed Sm valency, whereas methods (i) and (iii) fail. Therefore we conclude that the phase transition in SmS is very similar to the α-γ transition in Ce metal. The SIC band structure shows the splitting between the occupied and empty 4f states due to the large on-site electron correlation. The Fermi level ɛF is situated in the gap between the S 3p states and the Sm band states mainly of 5d character. In the high-pressure phase the 4f states presumably become delocalized, resulting in vanishing self-interaction corrections. Therefore the uncorrected LDA results are appropriate for the high-pressure phase.

  17. High-pressure structural phase transitions in chromium-doped BaFe[subscript 2]As[subscript 2

    Energy Technology Data Exchange (ETDEWEB)

    Uhoya, W.O.; Montgomery, J.M.; Samudrala, G.K.; Tsoi, G.M.; Vohra, Y.K.; Weir, S.T.; Sefat, A.S. (UAB); (LLNL); (ORNL)

    2012-10-23

    We report on the results from high pressure x-ray powder diffraction and electrical resistance measurements for hole doped BaFe{sub 2-x}Cr{sub x}As{sub 2} (x = 0, 0.05, 0.15, 0.4, 0.61) up to 81 GPa and down to 10 K using a synchrotron source and diamond anvil cell (DAC). At ambient temperature, an isostructural phase transition from a tetragonal (T) phase (I4/mmm) to a collapsed tetragonal (CT) phase is observed at 17 GPa. This transition is found to be dependent on ambient pressure unit cell volume and is slightly shifted to higher pressure upon increase in the Cr-doping. Unlike BaFe{sub 2}As{sub 2} which superconduct under high pressure, we have not detected any evidence of pressure induced superconductivity in chromium doped samples in the pressure and temperature range of this study. The measured equation of state parameters are presented for both the tetragonal and collapsed tetragonal phases for x = 0.05, 0.15, 0.40 and 0.61.

  18. A new aluminocalcic high-pressure phase as a possible host of calcium and aluminium in the lower mantle

    Science.gov (United States)

    Madon, M.; Castex, J.; Peyronneau, J.

    1989-11-01

    To study the possibility of host minerals alternative to the perovskite structure for the large cations in the deep mantle, natural (M/0.88/, Ca/0.12/)Al2Si3O12 garnets (with M = Mg, Fe, or Mn) at high pressure and high temperature were transformed in a laser-heated diamond-anvil cell. The quenched products were studied by analytical TEM, revealing the presence of a new phase with a composition close to (Ca/0.5/, M/0.5/)Al2Si2O8. High-pressure experiments performed with a glass of similar composition, (Ca/0.5/, Mg/0/5/)Al2Si2O8, confirm the existence of this new phase at a pressure of 50 GPa. The cell dimensions and stoichiometry of this new phase how strong similarities to those of the hollandite structure. Depending on the chemical composition of the lower mantle, this aluminocalcic phase could be the second or the third most abundant constituent of the lower mantle, in which case the abundance of CaSiO3 perovskite would be negligible.

  19. The baryonic phase in holographic descriptions of the QCD phase diagram

    NARCIS (Netherlands)

    Evans, N.; Kim, K.-Y.; Magou, M.; Seo, Y.; Sin, S.J.

    2012-01-01

    We study holographic models of the QCD temperature-chemical potential phase diagram based on the D3/D7 system with chiral symmetry breaking. The baryonic phase may be included through linked D5-D7 systems. In a previous analysis of a model with a running gauge coupling a baryonic phase was shown to

  20. Phase equilibria in fluid mixtures at high pressures - The He-CH4 system.

    Science.gov (United States)

    Streett, W. B.; Erickson, A. L.; Hill, J. L. E.

    1972-01-01

    An experimental study of phase equilibria in the He-CH4 system has been carried out over the temperature range 95 to 290 K and at pressures to 10,000 atm. The experimental results consist of equilibrium phase composition for twenty-eight isotherms in the region of coexistence of two fluid phases, together with the pressure-temperature trace of the three-phase boundary at which a CH4-rich solid phase is in equilibrium with the two fluid phases. The system exhibits a fluid-fluid phase separation which persists to temperatures and pressures beyond the range of this experiment. These findings are relevant to problems of deep atmosphere and interior structures in the outer planets.-

  1. Phase Transition and Optical Properties of Solid Oxygen under High Pressure: A Density Functional Theory Study

    Institute of Scientific and Technical Information of China (English)

    LIU Yan-Hui; TIAN Fu-Bo; MA Yan-Ming; HE Zhi; CUI Tian; LIU Bing-Bing; ZOU Guang-Tian

    2008-01-01

    Crystal structures and optical properties of the δ-O,2 phase and the ε-O,8 phase have been investigated by using the ab initio pseudopotential plane-wave method. It is found that the phase transition is of the first order with a discontinuous volumetric change from the antiferromagnetic δ-O,2 phase to the nonmagnetic ε-O8 phase, consistent with the experimental findings. The energy band calculations show that the direct band gap changes into an indirect band gap after the phase transition. The apparent change in the optical properties can be used for identifying the phase transition from δ-O2 to ε-O,8.

  2. Theoretical Prediction of Melting Relations in the Deep Mantle: the Phase Diagram Approach

    Science.gov (United States)

    Belmonte, D.; Ottonello, G. A.; Vetuschi Zuccolini, M.; Attene, M.

    2016-12-01

    Despite the outstanding progress in computer technology and experimental facilities, understanding melting phase relations in the deep mantle is still an open challenge. In this work a novel computational scheme to predict melting relations at HP-HT by a combination of first principles DFT calculations, polymer chemistry and equilibrium thermodynamics is presented and discussed. The adopted theoretical framework is physically-consistent and allows to compute multi-component phase diagrams relevant to Earth's deep interior in a broad range of P-T conditions by a convex-hull algorithm for Gibbs free energy minimisation purposely developed for high-rank simplexes. The calculated phase diagrams are in turn used as a source of information to gain new insights on the P-T-X evolution of magmas in the deep mantle, providing some thermodynamic constraints to both present-day and early Earth melting processes. High-pressure melting curves of mantle silicates are also obtained as by-product of phase diagram calculation. Application of the above method to the MgO-Al2O3-SiO2 (MAS) ternary system highlights as pressure effects are not only able to change the nature of melting of some minerals (like olivine and pyroxene) from eutectic to peritectic (and vice versa), but also simplify melting relations by drastically reducing the number of phases with a primary phase field at HP-HT conditions. It turns out that mineral phases like Majorite-Pyrope garnet and Anhydrous Phase B (Mg14Si5O24), which are often disregarded in modelling melting processes of mantle assemblages, are stable phases at solidus or liquidus conditions in a P-T range compatible with the mantle transition zone (i.e. P = 16 - 23 GPa and T = 2200 - 2700 °C) when their thermodynamic and thermophysical properties are properly assessed. Financial support to the Senior Author (D.B.) during his stay as Invited Scientist at the Institut de Physique du Globe de Paris (IPGP, Paris) is warmly acknowledged.

  3. Studies on Phase Behavior of Alkyl Polyglucoside Based on Microemulsions with Modified Fishlike Phase Diagram

    Institute of Scientific and Technical Information of China (English)

    Jin Ling CHAI; Gan Zuo LI; Zhao Yu DIAO; Gao Yong ZHANG

    2004-01-01

    The three-phase behavior in the quaternary system of an alkyl (C8/10- or C12/14-) polyglucoside / 1-butanol / n-octane / water has been studied at 40 ℃ with the modified fishlike phase diagram, which is presented by us for the first time. The mass fraction of 1-butanol in the hydrophile-lipophile balanced interfacial layer, AS, the coordinates of the start point B and the end point E of the phase diagram, and the solubilities of alkyl polyglucoside and 1-butanol in n-octane phase were calculated. The solubilization of the microemulsion was also discussed.

  4. Structure of intermediate phase II of LiNH2 under high pressure.

    Science.gov (United States)

    Yamawaki, Hiroshi; Fujihisa, Hiroshi; Gotoh, Yoshito; Nakano, Satoshi

    2014-08-21

    A new intermediate phase (phase II) was found between phases I and III in LiNH2 in the pressure range of 10 to 13 GPa through the analysis of infrared and powder X-ray diffraction measurements to 25 GPa at room temperature. This result agreed with the prediction of a stable phase between phases I and III through theoretical calculations. Powder X-ray diffraction measurement and DFT calculation showed that this phase has a monoclinic structure with space group C2/c (Z = 8), which is the same structure as that of a slightly tilted crystal lattice of the Fddd structural model. The enthalpy of the C2/c structure was also found to be almost the same as that of the Fddd structure.

  5. The Iron-Iron Carbide Phase Diagram: A Practical Guide to Some Descriptive Solid State Chemistry.

    Science.gov (United States)

    Long, Gary J.; Leighly, H. P., Jr.

    1982-01-01

    Discusses the solid state chemistry of iron and steel in terms of the iron-iron carbide phase diagram. Suggests that this is an excellent way of introducing the phase diagram (equilibrium diagram) to undergraduate students while at the same time introducing the descriptive solid state chemistry of iron and steel. (Author/JN)

  6. High-pressure phase of the cubic spinel NiMn2O4

    DEFF Research Database (Denmark)

    Åsbrink, S.; Waskowska, A.; Olsen, J. Staun

    1998-01-01

    It has been observed that the fee spinel NiMn2O4 transforms to a tetragonal structure at about 12 GPa. The tetragonal phase does not revert to the cubic phase upon decompression and its unit-cell constants at ambient pressure are a(0)=8.65(8) and c(0)=7.88(15) Angstrom (distorted fee). Within thr......). The bulk modulus of the cubic phase is 206(4) GPa....

  7. The phase diagram and transport properties of MgO from theory and experiment

    Science.gov (United States)

    Shulenburger, Luke

    2013-06-01

    Planetary structure and the formation of terrestrial planets have received tremendous interest due to the discovery of so called super-earth exoplanets. MgO is a major constituent of Earth's mantle, the rocky cores of gas giants and is a likely component of the interiors of many of these exoplanets. The high pressure - high temperature behavior of MgO directly affects equation of state models for planetary structure and formation. In this work, we examine MgO under extreme conditions using experimental and theoretical methods to determine its phase diagram and transport properties. Using plate impact experiments on Sandia's Z facility the solid-solid phase transition from B1 to B2 is clearly determined. The melting transition, on the other hand, is subtle, involving little to no signal in us-up space. Theoretical work utilizing density functional theory (DFT) provides a complementary picture of the phase diagram. The solid-solid phase transition is identified through a series of quasi-harmonic phonon calculations and thermodynamic integration, while the melt boundary is found using phase coexistence calculations. One issue of particular import is the calculation of reflectivity along the Hugoniot and the influence of the ionic structure on the transport properties. Particular care is necessary because of the underestimation of the band gap and attendant overestimation of transport properties due to the use of semi-local density functional theory. We will explore the impact of this theoretical challenge and its potential solutions in this talk. The integrated use of DFT simulations and high-accuracy shock experiments together provide a comprehensive understanding of MgO under extreme conditions. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U.S. DOE's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  8. Real-Time Optical Monitoring of Flow Kinetics and Gas Phase Reactions Under High-Pressure OMCVD Conditions

    Science.gov (United States)

    Dietz, N.; McCall, S.; Bachmann, K. J.

    2001-01-01

    This contribution addresses the real-time optical characterization of gas flow and gas phase reactions as they play a crucial role for chemical vapor phase depositions utilizing elevated and high pressure chemical vapor deposition (HPCVD) conditions. The objectives of these experiments are to validate on the basis of results on real-time optical diagnostics process models simulation codes, and provide input parameter sets needed for analysis and control of chemical vapor deposition at elevated pressures. Access to microgravity is required to retain high pressure conditions of laminar flow, which is essential for successful acquisition and interpretation of the optical data. In this contribution, we describe the design and construction of the HPCVD system, which include access ports for various optical methods of real-time process monitoring and to analyze the initial stages of heteroepitaxy and steady-state growth in the different pressure ranges. To analyze the onset of turbulence, provisions are made for implementation of experimental methods for in-situ characterization of the nature of flow. This knowledge will be the basis for the design definition of experiments under microgravity, where gas flow conditions, gas phase and surface chemistry, might be analyzed by remote controlled real-time diagnostics tools, developed in this research project.

  9. Structural phase transition and elastic properties of thorium pnictides at high pressure

    Indian Academy of Sciences (India)

    Kuldeep Kholiya; B R K Gupta

    2007-04-01

    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 with the experimental and previous theoretical work.

  10. Stability of the high-pressure body-centered-cubic phase of helium

    NARCIS (Netherlands)

    Frenkel, D.

    1986-01-01

    This paper report absolute free-energy calculations of the fluid, body-centered-cubic, and face-centered-cubic phases of helium at T=327.04 K. We find that at and around this temperature the model potential proposed by Aziz et al. doe not yield a stable bcc phase. Quantum corrections do not alter th

  11. Stability of the high-pressure body-centered-cubic phase of helium

    OpenAIRE

    Frenkel, D.

    1987-01-01

    This paper report absolute free-energy calculations of the fluid, body-centered-cubic, and face-centered-cubic phases of helium at T=327.04 K. We find that at and around this temperature the model potential proposed by Aziz et al. doe not yield a stable bcc phase. Quantum corrections do not alter this conclusion

  12. QCD phase diagram from finite energy sum rules

    CERN Document Server

    Ayala, Alejandro; Dominguez, C A; Gutierrez, Enif; Loewe, M; Raya, Alfredo

    2011-01-01

    We study the QCD phase diagram at finite temperature and baryon chemical potential by relating the behavior of the light-quark condensate to the threshold energy for the onset of perturbative QCD. These parameters are connected to the chiral symmetry restoration and the deconfinement phase transition, respectively. This relation is obtained in the framework of finite energy QCD sum rules at finite temperature and density, with input from Schwinger-Dyson methods to determine the light-quark condensate. Results indicate that both critical temperatures are basically the same within some 3% accuracy. We also obtain bounds for the position of the critical end point, mu_{B c} >~ 300 MeV and T_c <~ 185 MeV.

  13. Constraints for the QCD phase diagram from imaginary chemical potential

    CERN Document Server

    Philipsen, Owe

    2010-01-01

    We present unambiguous evidence from lattice simulations of N_f=3 QCD for two tricritical points in the (T,m) phase diagram at fixed imaginary \\mu/T=i\\pi/3 mod. 2\\pi/3, one in the light and one in the heavy quark regime. Together with similar results in the literature for N_f=2 this implies the existence of a chiral and of a deconfinement tricritical line at those values of imaginary chemical potentials. These tricritical lines represent the boundaries of the analytically continued chiral and deconfinement critical surfaces, respectively, which delimit the parameter space with first order phase transitions. It is demonstrated that the shape of the deconfinement critical surface is dictated by tricritical scaling and implies the weakening of the deconfinement transition with real chemical potential. A qualitatively similar effect holds for the chiral critical surface.

  14. Magnetic phase diagrams of α-MnMoO 4

    Science.gov (United States)

    Ehrenberg, H.; Schwarz, B.; Weitzel, H.

    2006-10-01

    Field-induced spin-flop transitions in α-MnMoO 4 are summarized in magnetic H-T phase diagrams for different directions of the applied magnetic field up to 12 T. The antiferromagnetic arrangement in the spin-flop phase is preserved at least up to this field for a field parallel to the easy direction. This high transition field is in contrast to the low one of α-NiMoO 4 and favours a model, based on dominant antiferromagnetic supersuperexchange couplings in α-MnMoO 4 over a ferromagnetic Mn 4 "cluster" model. The Néel temperature of 9.8(1) K was determined from the corresponding specific-heat anomaly, measured on a single crystal of α-MnMoO 4.

  15. High-pressure phase transitions in rare earth metal thulium to 195 GPa.

    Science.gov (United States)

    Montgomery, Jeffrey M; Samudrala, Gopi K; Tsoi, Georgiy M; Vohra, Yogesh K

    2011-04-20

    We have performed image plate x-ray diffraction studies on a heavy rare earth metal, thulium (Tm), in a diamond anvil cell to a pressure of 195 GPa and volume compression V/V₀ = 0.38 at room temperature. The rare earth crystal structure sequence, hcp →Sm-type→ dhcp →fcc → distorted fcc, is observed in Tm below 70 GPa with the exception of a pure fcc phase. The focus of our study is on the ultrahigh-pressure phase transition and Rietveld refinement of crystal structures in the pressure range between 70 and 195 GPa. The hexagonal hR-24 phase is seen to describe the distorted fcc phase between 70 and 124 GPa. Above 124 ± 4 GPa, a structural transformation from hR 24 phase to a monoclinic C 2/m phase is observed with a volume change of -1.5%. The equation of state data shows rapid stiffening above the phase transition at 124 GPa and is indicative of participation of f-electrons in bonding. We compare the behavior of Tm to other heavy rare-earths and heavy actinide metals under extreme conditions of pressure.

  16. Synthesis of new Diamond-like B-C Phases under High Pressure and Temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Ming, L. C. [University of Hawaii; Zinin, P. V. [University of Hawaii; Sharma, S. K. [University of Hawaii

    2014-04-22

    A cubic BC3 (c-BC3) phase was synthesized by direct transformation from graphitic phases at a pressure of 39 GPa and temperature of 2200 K in a laser-heated diamond anvil cell (DAC). A combination of x-ray diffraction (XRD), electron diffraction (ED), transmission electron microscopy (TEM) imaging, and electron energy loss spectroscopy (EELS) measurements lead us to conclude that the obtained phase is hetero-nano-diamond, c-BC3. The EELS measurements show that the atoms inside the cubic structure are bonded by sp3 bonds.

  17. A study of the Al–Pt–Ir phase diagram

    Energy Technology Data Exchange (ETDEWEB)

    Grushko, B., E-mail: b.grushko@fz-juelich.de [MaTecK, 52428 Jülich (Germany); PGI-5, Forschungszentrum Jülich, 52425 Jülich (Germany); Samuha, S. [Dept. Materials Engineering, Ben-Gurion University of the Negev, 84105 Beer-Sheva (Israel); NRCN, P.O. Box 9001, 84190 Beer-Sheva (Israel); Meshi, L. [Dept. Materials Engineering, Ben-Gurion University of the Negev, 84105 Beer-Sheva (Israel)

    2015-10-15

    Phase equilibria in Al–Pt–Ir were studied up to 50 at.% Al at 1100 °C, up to 70 at.% Al at 900 °C and up to 75 at.% Al at 810 °C. At elevated temperatures the isostructural AlIr and high-temperature AlPt β-phases probably form a continuous compositional region. The ternary extensions of the phases Al{sub 4}Pt, Al{sub 21}Pt{sub 8}, Al{sub 3}Pt{sub 2} and low-temperature AlPt were revealed along approximately constant Al concentrations up to 15, 11, 20 and 10 at.% Ir, respectively. The Al–Ir C-phase dissolved up to 12 at.% Pt, and the χ-phase propagated up to almost Al{sub 3}Pt. A new ternary B-phase (I4{sub 1}/acd, a = 0.86250, c = 2.18409 nm) was revealed around Al{sub 69}Pt{sub 7}Ir{sub 24}. Its structural model was derived from the electron diffraction data. - Highlights: • The Al–Pt–Ir phase diagram was studied at 810, 900 and 1100 °C. • The majority of binaries extend widely along about constant Al. • The new ternary B-phase of the Ga{sub 4}Ir{sub 8}B type was revealed at Al{sub 69}Pt{sub 7}Ir{sub 24}. • The structural model of the B-phase was derived from electron diffraction.

  18. High-pressure synchrotron x-ray diffraction and infrared microspectroscopy: applications to dense hydrous phases

    CERN Document Server

    Liu, Z; Yang, H; Mao Ho Kwang; Hemley, R J

    2002-01-01

    Synchrotron x-ray diffraction (XRD) and infrared (IR) absorption spectra of hydrous and 'anhydrous' forms of phase X were measured to 30 GPa at room temperature. Three OH stretching modes were found in the hydrous phase, and surprisingly one sharp OH mode was observed in the previously characterized anhydrous phase. All OH stretching modes soften and broaden with increasing pressure and become very weak above approx 20 GPa. XRD indicates that the crystal structure remains stable up to 30 GPa. Combining IR absorption and XRD results, the behaviour is attributed to pressure-induced distortion of the Si sub 2 O sub 7 groups and disorder of the hydrogen atoms. The bulk moduli of the hydrous and 'anhydrous' phases are in the region of 74 GPa.

  19. In situ observations of a high-pressure phase of H2O ice

    Science.gov (United States)

    Chou, I.-Ming; Blank, J.G.; Goncharov, A.F.; Mao, Ho-kwang; Hemley, R.J.

    1998-01-01

    A previously unknown solid phase of H2O has been identified by its peculiar growth patterns, distinct pressure-temperature melting relations, and vibrational Raman spectra. Morphologies of ice crystals and their pressure-temperature melting relations were directly observed in a hydrothermal diamond-anvil cell for H2O bulk densities between 1203 and 1257 kilograms per cubic meter at temperatures between -10??and 50??C. Under these conditions, four different ice forms were observed to melt: two stable phases, ice V and ice VI, and two metastable phases, ice IV and the new ice phase. The Raman spectra and crystal morphology are consistent with a disordered anisotropic structure with some similarities to ice VI.

  20. Experimental investigation of the Cd-Pr phase diagram.

    Directory of Open Access Journals (Sweden)

    Thomas L Reichmann

    Full Text Available The complete Cd-Pr equilibrium phase diagram was investigated with a combination of powder-XRD, SEM and DTA. All intermetallic compounds within this system, already reported in literature, could be confirmed: CdPr, Cd2Pr, Cd3Pr, Cd45Pr11, Cd58Pr13, Cd6Pr and Cd11Pr. The corresponding phase boundaries were determined at distinct temperatures. The homogeneity range of the high-temperature allotropic modification of Pr could be determined precisely and a limited solubility of 22.1 at.% Cd was derived. Additionally, single-crystal X-ray diffraction was employed to investigate structural details of Cd2Pr; it is isotypic to the AlB2-type structure with a z value of the Cd site of 0.5. DTA results of alloys located in the adjacent two-phase fields of Cd2Pr suggested a phase transformation between 893 and 930°C. For the phase Cd3Pr it was found that the lattice parameter a changes linearly with increasing Cd content, following Vegard's rule. The corresponding defect mechanism could be evaluated from structural data collected with single-crystal XRD. Introduction of a significant amount of vacancies on the Pr site and the reduction in symmetry of one Cd position (8c to 32f resulted in a noticeable decrease of all R-values.

  1. Experimental investigation of the Cd-Pr phase diagram.

    Science.gov (United States)

    Reichmann, Thomas L; Effenberger, Herta S; Ipser, Herbert

    2014-01-01

    The complete Cd-Pr equilibrium phase diagram was investigated with a combination of powder-XRD, SEM and DTA. All intermetallic compounds within this system, already reported in literature, could be confirmed: CdPr, Cd2Pr, Cd3Pr, Cd45Pr11, Cd58Pr13, Cd6Pr and Cd11Pr. The corresponding phase boundaries were determined at distinct temperatures. The homogeneity range of the high-temperature allotropic modification of Pr could be determined precisely and a limited solubility of 22.1 at.% Cd was derived. Additionally, single-crystal X-ray diffraction was employed to investigate structural details of Cd2Pr; it is isotypic to the AlB2-type structure with a z value of the Cd site of 0.5. DTA results of alloys located in the adjacent two-phase fields of Cd2Pr suggested a phase transformation between 893 and 930°C. For the phase Cd3Pr it was found that the lattice parameter a changes linearly with increasing Cd content, following Vegard's rule. The corresponding defect mechanism could be evaluated from structural data collected with single-crystal XRD. Introduction of a significant amount of vacancies on the Pr site and the reduction in symmetry of one Cd position (8c to 32f) resulted in a noticeable decrease of all R-values.

  2. Conductivity, calorimetry and phase diagram of the NaHSO4–KHSO4 system

    DEFF Research Database (Denmark)

    Hind, Hamma-Cugny; Rasmussen, Søren Birk; Rogez, J.

    2006-01-01

    Physico-chemical properties of the binary system NaHSO4-KHSO4 were studied by calorimetry and conductivity, The enthalpy of mixing has been measured at 505 K in the full composition range and the phase diagram calculated. The phase diagram has also been constructed from phase transition temperatu......Physico-chemical properties of the binary system NaHSO4-KHSO4 were studied by calorimetry and conductivity, The enthalpy of mixing has been measured at 505 K in the full composition range and the phase diagram calculated. The phase diagram has also been constructed from phase transition...

  3. Structural and electronic properties of high pressure phases of lead chalcogenides

    Science.gov (United States)

    Petersen, John; Scolfaro, Luisa; Myers, Thomas

    2012-10-01

    Lead chalcogenides, most notably PbTe and PbSe, have become an active area of research due to their thermoelectric properties. The high figure of merit (ZT) of these materials has brought much attention to them, due to their ability to convert waste heat into electricity. Variation in synthesis conditions gives rise to a need for analysis of structural and thermoelectric properties of these materials at different pressures. In addition to the NaCl structure at ambient conditions, lead chalcogenides have a dynamic orthorhombic (Pnma) intermediate phase and a higher pressure yet stable CsCl phase. By altering the lattice constant, we simulate the application of external pressure; this has notable effects on ground state total energy, band gap, and structural phase. Using the General Gradient Approximation (GGA) in Density Functional Theory (DFT), we calculate the phase transition pressures by finding the differences in enthalpy from total energy calculations. For each phase, elastic constants, bulk modulus, shear modulus, Young's modulus, and hardness are calculated, using two different approaches. In addition to structural properties, we analyze the band structure and density of states at varying pressures, paying special note to thermoelectric implications.

  4. High-pressure phases of uranium monophosphide studied by synchrotron x-ray diffraction

    DEFF Research Database (Denmark)

    Olsen, J. Staun; Gerward, Leif; Benedict, U.

    1988-01-01

    X-ray diffraction studies have been performed on UP powder for pressures up to 51 GPa using synchrotron radiation and a diamond-anvil cell. At ambient pressure UP has the rocksalt structure. The bulk modulus has been determined to B0=102(4) GPa and its pressure derivative to B0’=4.0(8). The cubic...... phase has been found to transform to a new phase, UP II, at about 10 GPa. UP II can be characterized by a rhombohedral Bravais lattice. UP II transforms to an orthorhombic phase, UP III, at 28 GPa. No volume change has been observed at the two transitions. The influence of the 5f electrons...

  5. Spectroscopic Study of the Effects of Pressure Media on High-Pressure Phase Transitions in Natrolite

    Energy Technology Data Exchange (ETDEWEB)

    D Liu; W Lei; Z Liu; Y Lee

    2011-12-31

    Structural phase transitions in natrolite have been investigated as a function of pressure and different hydrostatic media using micro-Raman scattering and synchrotron infrared (IR) spectroscopy. Natrolite undergoes two reversible phase transitions at 0.86 and 1.53 GPa under pure water pressure medium. These phase transitions are characterized by the changes in the vibrational frequencies of four- and eight-membered rings related to the variations in the bridging T-O-T angles and the geometry of the elliptical eight-ring channels under pressure. Concomitant to the changes in the framework vibrational modes, the number of the O-H stretching vibrational modes of natrolite changes as a result of the rearrangements of the hydrogen bonds in the channels caused by a successive increase in the hydration level under hydrostatic pressure. Similar phase transitions were also observed at relatively higher pressures (1.13 and 1.59 GPa) under alcohol-water pressure medium. Furthermore, no phase transition was found up to 2.52 GPa if a lower volume ratio of the alcohol-water to natrolite was employed. This indicates that the water content in the pressure media plays a crucial role in triggering the pressure-induced phase transitions in natrolite. In addition, the average of the mode Grueneisen parameters is calculated to be about 0.6, while the thermodynamic Grueneisen parameter is found to be 1.33. This might be attributed to the contrast in the rigidity between the TO{sub 4} tetrahedral primary building units and other flexible secondary building units in the natrolite framework upon compression and subsequent water insertion.

  6. Compressibility of the high-pressure rocksalt phase of ZnO

    DEFF Research Database (Denmark)

    Recio, J.M.; Blanco, M.A.; Luana, V.

    1998-01-01

    We report the results of a combined experimental and theoretical investigation on the stability and the volume behavior under hydrostatic pressure of the rocksalt (B1) phase of ZnO. Synchrotron-radiation x-ray powder-diffraction data are obtained from 0 to 30 GPa. Static simulations of the ZnO B1...... in the range of 160-194 GPa. For its zero-pressure first derivative, the experimental and theoretical data yield a value of 4.4+/-1.0. Overall, our results show that the ZnO B1 phase is slightly more compressible than previously reported. [S0163-1829(98)07537-7]....

  7. Phase relation of CaSO4 at high pressure and temperature up to 90 GPa and 2300 K

    Science.gov (United States)

    Fujii, Taku; Ohfuji, Hiroaki; Inoue, Toru

    2016-05-01

    Calcium sulfate (CaSO4), one of the major sulfate minerals in the Earth's crust, is expected to play a major role in sulfur recycling into the deep mantle. Here, we investigated the crystal structure and phase relation of CaSO4 up to ~90 GPa and 2300 K through a series of high-pressure experiments combined with in situ X-ray diffraction. CaSO4 forms three thermodynamically stable polymorphs: anhydrite (stable below 3 GPa), monazite-type phase (stable between 3 and ~13 GPa) and barite-type phase (stable up to at least 93 GPa). Anhydrite to monazite-type phase transition is induced by pressure even at room temperature, while monazite- to barite-type transition requires heating at least to 1500 K at ~20 GPa. The barite-type phase cannot always be quenched from high temperature and is distorted to metastable AgMnO4-type structure or another modified barite structure depending on pressure. We obtained the pressure-volume data and density of anhydrite, monazite- and barite-type phases and found that their densities are lower than those calculated from the PREM model in the studied P-T conditions. This suggests that CaSO4 is gravitationally unstable in the mantle and fluid/melt phase into which sulfur dissolves and/or sulfate-sulfide speciation may play a major role in the sulfur recycling into the deep Earth.

  8. Beryl-II, a high-pressure phase of beryl: Raman and luminescence spectroscopy to 16.4 GPa

    Science.gov (United States)

    O'Bannon, Earl; Williams, Quentin

    2016-10-01

    The Raman and Cr3+ and V2+ luminescence spectra of beryl and emerald have been characterized up to 15.0 and 16.4 GPa, respectively. The Raman spectra show that an E 1g symmetry mode at 138 cm-1 shifts negatively by -4.57 (±0.55) cm-1/GPa, and an extrapolation of the pressure dependence of this mode indicates that a soft-mode transition should occur near 12 GPa. Such a transition is in accord with prior theoretical results. Dramatic changes in Raman mode intensities and positions occur between 11.2 and 15.0 GPa. These changes are indicative of a phase transition that primarily involves tilting and mild distortion of the Si6O18 rings. New Raman modes are not observed in the high-pressure phase, which indicates that the local bonding environment is not altered dramatically across the transition (e.g., changes in coordination do not occur). Both sharp line and broadband luminescence are observed for both Cr3+ and V2+ in emerald under compression to 16.4 GPa. The R-lines of both Cr3+ and V2+ shift to lower energy (longer wavelength) under compression. Both R-lines of Cr3+ split at ~13.7 GPa, and the V2+ R1 slope changes at this pressure and shifts more rapidly up to ~16.4 GPa. The Cr3+ R-line splitting and FWHM show more complex behavior, but also shift in behavior at ~13.7 GPa. These changes in the pressure dependency of the Cr3+ and V2+ R-lines and the changes in R-line splitting and FWHM at ~13.7 GPa further demonstrate that a phase transition occurs at this pressure, in good agreement with our Raman results. The high-pressure phase of beryl appears to have two Al sites that become more regular under compression. Hysteresis is not observed in our Raman or luminescence spectra on decompression, suggesting that this transition is second order in nature: The occurrence of a second-order transition near this pressure is also in accord with prior theoretical results. We speculate that the high-pressure phase (beryl-II) might be a mildly modulated structure, and/or that

  9. Structural and Phase State of Fractured Rotor of High-Pressure Steam Turbine

    Science.gov (United States)

    Smirnov, A. N.; Ababkov, N. V.; Kozlov, E. V.; Koneva, N. A.; Popova, N. A.

    2016-03-01

    The structural and phase state of the metal of a fractured rotor of a steam turbine is studied with the use of modern methods of physical research. The metal is shown to contain gradient structures. The cause of the failure of the rotor is established. The gradient structures are determined by the developed method of acoustic scanning.

  10. Monte Carlo simulations of high-pressure phase equilibria of CO2-H2O mixtures.

    Science.gov (United States)

    Liu, Yang; Panagiotopoulos, Athanassios Z; Debenedetti, Pablo G

    2011-05-26

    Histogram-reweighting grand canonical Monte Carlo simulations were used to obtain the phase behavior of CO(2)-H(2)O mixtures over a broad temperature and pressure range (50 °C ≤ T ≤ 350 °C, 0 ≤ P ≤ 1000 bar). We performed a comprehensive test of several existing water (SPC, TIP4P, TIP4P2005, and exponential-6) and carbon dioxide (EPM2, TraPPE, and exponential-6) models using conventional Lorentz-Berthelot combining rules for the unlike-pair parameters. None of the models we studied reproduce adequately experimental data over the entire temperature and pressure range, but critical assessments were made on the range of T and P where particular model pairs perform better. Away from the critical region (T ≤ 250 °C), the exponential-6 model combination yields the best predictions for the CO(2)-rich phase, whereas the TraPPE/TIP4P2005 model combination provides the most accurate coexistence composition and pressure for the H(2)O-rich phase. Near the critical region (250 °C < T ≤ 350 °C), the critical points are not accurately estimated by any of the models studied, but the exponential-6 models are able to qualitatively capture the critical loci and the shape of the phase envelopes. Local improvements can be achieved at specific temperatures by introducing modification factors to the Lorentz-Berthelot combining rules, but the modified combining rule is still not able to achieve global improvements over the entire temperature and pressure range. Our work points to the challenge and importance of improving current atomistic models so as to accurately predict the phase behavior of this important binary mixture.

  11. Liquid-ordered phases induced by cholesterol: a compendium of binary phase diagrams.

    Science.gov (United States)

    Marsh, Derek

    2010-03-01

    Mixtures of phospholipids with cholesterol are able to form liquid-ordered phases that are characterised by short-range orientational order and long-range translational disorder. These L(o)-phases are distinct from the liquid-disordered, fluid L(alpha)-phases and the solid-ordered, gel L(beta)-phases that are assumed by the phospholipids alone. The liquid-ordered phase can produce spatially separated in-plane fluid domains, which, in the form of lipid rafts, are thought to act as platforms for signalling and membrane sorting in cells. The areas of domain formation are defined by the regions of phase coexistence in the phase diagrams for the binary mixtures of lipid with cholesterol. In this paper, the available binary phase diagrams of lipid-cholesterol mixtures are all collected together. It is found that there is not complete agreement between different determinations of the phase diagrams for the same binary mixture. This can be attributed to the indirect methods largely used to establish the phase boundaries. Intercomparison of the various data sets allows critical assessment of which phase boundaries are rigorously established from direct evidence for phase coexistence.

  12. Phase Diagram of Inhomogeneous Percolation with a Defect Plane

    Science.gov (United States)

    Iliev, G. K.; Janse van Rensburg, E. J.; Madras, N.

    2015-01-01

    Let be the -dimensional hypercubic lattice and let be an -dimensional sublattice, with . We consider a model of inhomogeneous bond percolation on at densities and , in which edges in are open with probability , and edges in open with probability . We generalize several classical results of (homogeneous) bond percolation to this inhomogeneous model. The phase diagram of the model is presented, and it is shown that there is a subcritical regime for and (where is the critical probability for homogeneous percolation in ), a bulk supercritical regime for , and a surface supercritical regime for and . We show that is a strictly decreasing function for , with a jump discontinuity at . We extend the Aizenman-Barsky differential inequalities for homogeneous percolation to the inhomogeneous model and use them to prove that the susceptibility is finite inside the subcritical phase. We prove that the cluster size distribution decays exponentially in the subcritical phase, and sub-exponentially in the supercritical phases. For a model of lattice animals with a defect plane, the free energy is related to functions of the inhomogeneous percolation model, and we show how the percolation transition implies a non-analyticity in the free energy of the animal model. Finally, we present simulation estimates of the critical curve.

  13. Neutron diffraction and electrical transport studies on the incommensurate magnetic phase transition in holmium at high pressures

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, Sarah [University of Alabama, Birmingham; Uhoya, Walter [University of Alabama, Birmingham; Tsoi, Georgiy [University of Alabama, Birmingham; Wenger, Lowell E [University of Alabama, Birmingham; Vohra, Yogesh [University of Alabama, Birmingham; Chesnut, Gary Neal [University of Alabama, Birmingham; Weir, S. T. [Lawrence Livermore National Laboratory (LLNL); Tulk, Christopher A [ORNL; Moreira Dos Santos, Antonio F [ORNL

    2012-01-01

    Neutron diffraction and electrical transport measurements have been made on the heavy rare earth metal holmium at high pressures and low temperatures in order to elucidate its transition from a paramagnetic (PM) to a helical antiferromagnetic (AFM) ordered phase as a function of pressure. The electrical resistance measurements show a change in the resistance slope as the temperature is lowered through the antiferromagnetic Neel temperature. The temperature of this antiferromagnetic transition decreases from approximately 122 K at ambient pressure at a rate of -4.9 K GPa(-1) up to a pressure of 9 GPa, whereupon the PM-to-AFM transition vanishes for higher pressures. Neutron diffraction measurements as a function of pressure at 89 and 110 K confirm the incommensurate nature of the phase transition associated with the antiferromagnetic ordering of the magnetic moments in a helical arrangement and that the ordering occurs at similar pressures as determined from the resistance results for these temperatures.

  14. First-principles calculations of structure and high pressure phase transition in gallium nitride

    Institute of Scientific and Technical Information of China (English)

    Tan Li-Na; Hu Cui-E; Yu Bai-Ru; Chen Xiang-Rong

    2007-01-01

    The phase transitions of semiconductor GaN from the Wurtzite (WZ) structure and the zinc-blende (ZB) structure to the rocksalt (RS) structure are investigated by using the first-principles plane-wave pseudopotential density functional method combined with the ultrasoft pseudopotential scheme in the generalized gradient approximation (GGA)correction. It is found that the phase transitions from the WZ structure and the ZB structure to the RS structure occur at pressures of 46.1 GPa and 45.2 GPa, respectively. The lattice parameters, bulk moduli and their pressure derivatives of these structures of GaN are also calculated. Our results are consistent with available experimental and other theoretical results. The dependence of the normalized formula-unit volume V/Vo on pressure P is also successfully obtained.

  15. Predicted novel metallic metastable phases of polymeric nitrogen at high pressures

    Science.gov (United States)

    Wang, Xiaoli; Tian, Fubo; Wang, Lin; Jin, Xilian; Duan, Defang; Huang, Xiaoli; Liu, Bingbing; Cui, Tian

    2013-01-01

    Two new metallic polymeric structures of nitrogen, Pnnm and Cccm, are found by means of the first-principles density functional theory and a random structure-searching method. Firstly, it is shown that the transition behavior of nitrogen from insulator to metal starts at a pressure of approximately 460 GPa at 0 K. The Pnnm phase becomes energetically favorable with respect to cubic gauche at 363 GPa, and then transforms to the Cccm structure at 884 GPa. Electron-phonon coupling calculations suggest that the Pnnm crystal possesses superconductivity. The stability of these two phases is also explored, showing for the first time that they are stable structures of nitrogen exhibiting metallic properties.

  16. Phase Diagram and Electronic Structure of Praseodymium and Plutonium

    Science.gov (United States)

    Lanatà, Nicola; Yao, Yongxin; Wang, Cai-Zhuang; Ho, Kai-Ming; Kotliar, Gabriel

    2015-01-01

    We develop a new implementation of the Gutzwiller approximation in combination with the local density approximation, which enables us to study complex 4 f and 5 f systems beyond the reach of previous approaches. We calculate from first principles the zero-temperature phase diagram and electronic structure of Pr and Pu, finding good agreement with the experiments. Our study of Pr indicates that its pressure-induced volume-collapse transition would not occur without change of lattice structure—contrarily to Ce. Our study of Pu shows that the most important effect originating the differentiation between the equilibrium densities of its allotropes is the competition between the Peierls effect and the Madelung interaction and not the dependence of the electron correlations on the lattice structure.

  17. Phase diagram of hopping conduction mechanisms in polymer nanofiber network

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jeng-Ting; Lu, Yu-Cheng; Jiang, Shiau-Bin; Zhong, Yuan-Liang, E-mail: ylzhong@cycu.edu.tw [Department of Physics and Center for Nanotechnology, Chung Yuan Christian University, Chung-Li 32023, Taiwan (China); Yeh, Jui-Ming [Department of Chemistry and Center for Nanotechnology, Chung Yuan Christian University, Chung-Li 32023, Taiwan (China)

    2015-12-07

    Network formation by nanofiber crosslinking is usually in polymer materials as application in organic semiconductor devices. Electron hopping transport mechanisms depend on polymer morphology in network. Conducting polymers morphology in a random network structure is modeled by a quasi-one-dimensional system coupled of chains or fibers. We observe the varying hopping conduction mechanisms in the polyaniline nanofibers of the random network structure. The average diameter d of the nanofibers is varied from approximately 10 to 100 nm. The different dominant hopping mechanisms including Efros-Shklovskii variable-range hopping (VRH), Mott VRH, and nearest-neighbor hopping are dependent on temperature range and d in crossover changes. The result of this study is first presented in a phase diagram of hopping conduction mechanisms based on the theories of the random network model. The hopping conduction mechanism is unlike in normal semiconductor materials.

  18. Cumulants and Correlation Functions vs the QCD phase diagram

    CERN Document Server

    Bzdak, Adam; Strodthoff, Nils

    2016-01-01

    In this note we discuss the relation of particle number cumulants and correlation functions related to them. It is argued that measuring couplings of the genuine correlation functions could provide cleaner information on possible non-trivial dynamics in heavy-ion collisions. We extract integrated multi-particle correlation functions from the presently available experimental data on proton cumulants. We find that the STAR data contain significant four-particle correlations, at least at the lower energies, with indication of changing dynamics in central collisions. We also find that these correlations are rather long-ranged in rapidity. Finally based on the signs of genuine correlation functions we provide exclusion plots for the QCD phase diagram.

  19. Modelling of phase diagrams of nanoalloys with complex metallic phases: application to Ni-Sn.

    Science.gov (United States)

    Kroupa, A; Káňa, T; Buršík, J; Zemanová, A; Šob, M

    2015-11-14

    A method for modelling of size-dependent phase diagrams was developed by combining the semiempirical CALPHAD method and ab initio calculations of surface stresses for intermetallic phases. A novel approach was devised for the calculation of surface energy, free of systematic errors from the selection of different parameters of the software (e.g. number of the k-points) and for handling layered structures and off-stoichiometric slabs. Our approach allows the determination of complex size-dependent phase diagrams of systems with intermetallic phases, which was not possible up to now. The method was verified for the modelling of the phase diagram of the Ni-Sn system and basic comparison with rare experimental results was shown. There is reasonable agreement between the calculated and experimental results. The modelling of size-dependent phase diagrams of real systems allows the prediction of phase equilibria existing in nanosystems and possible changes in material properties. There is a need for such knowledge and the existence of reliable data for simpler systems is crucial for further application of this approach. This should motivate future experimental work.

  20. Phase Equilibria of the Carbon Dioxide + 1-Decanol System at High Pressures.

    Science.gov (United States)

    Ioniţă, Simona; Feroiu, Viorel; Geană, Dan

    2013-11-14

    In this work experimental vapor-liquid equilibrium (VLE) data and three-phase vapor-liquid-liquid equilibrium (VLLE) data are presented for the carbon dioxide + 1-decanol system. The VLE data were measured at five temperatures, (303.2, 308.2, 323.2, 333.2, and 343.2) K, and pressures up to 16 MPa. The VLLE data cover pressure-temperature (P-T) values from 289 K and 5 MPa to the upper critical end point (UCEP). We have used two models to represent the complex fluid phase behavior (P-T critical curve, VLLE line, and VLE isotherms) of the carbon dioxide + 1-decanol system: the cubic general equation of state (GEOS) and Peng-Robinson (PR) equation in conjunction with van der Waals two parameters conventional mixing rules (2PCMR). A correlation method involving temperature-dependent interaction parameters and a semipredictive approach with independent temperature interaction parameters have been used. Comparisons with experimental data reported in this work and available in the literature indicate that the topology of fluid phase behavior is satisfactorily given by the semipredictive procedure both for the critical line and in subcritical region, considering the relative simple used cubic equations of state.

  1. Phase transformation in hexagonal ErMnO3 under high pressure

    Science.gov (United States)

    Lin, Chuanlong; Liu, Jing; Li, Xiaodong; Li, Yanchun; Chu, Shenqi; Xiong, Lun; Li, Rui

    2012-12-01

    The pressure-induced phase transition of the hexagonal manganite ErMnO3 has been investigated using the synchrotron x-ray diffraction technique up to 57.6 GPa in a diamond anvil cell. The hexagonal structure exhibits anisotropic compression behavior. The bulk modulus (B0) is 168(3) GPa with B0' = 4.0 (fixed). At room temperature, ErMnO3 undergoes a hexagonal-to-orthorhombic phase transition at ˜20.2 GPa, but coexists with the orthorhombic phase up to the highest pressure of 57.6 GPa. When laser-heated to 1500-2000 K, the hexagonal ErMnO3 transforms to a denser orthorhombic perovskite structure completely at ˜17 GPa, accompanied by ˜11% volume reduction. The distortion and tilts of the octahedra MnO6 in the orthorhombic structure decrease with increasing pressure. The bulk modulus of the orthorhombic structure is 214(4) GPa with B0' = 4.0 (fixed), larger than that of the hexagonal structure. The orthorhombic structure ErMnO3 is stable at least up to ˜45 GPa and can be quenched.

  2. A molecular dynamics study of ambient and high pressure phases of silica: Structure and enthalpy variation with molar volume

    Science.gov (United States)

    Rajappa, Chitra; Sringeri, S. Bhuvaneshwari; Subramanian, Yashonath; Gopalakrishnan, J.

    2014-06-01

    Extensive molecular dynamics studies of 13 different silica polymorphs are reported in the isothermal-isobaric ensemble with the Parrinello-Rahman variable shape simulation cell. The van Beest-Kramer-van Santen (BKS) potential is shown to predict lattice parameters for most phases within 2%-3% accuracy, as well as the relative stabilities of different polymorphs in agreement with experiment. Enthalpies of high-density polymorphs - CaCl2-type, α-PbO2-type, and pyrite-type - for which no experimental data are available as yet, are predicted here. Further, the calculated enthalpies exhibit two distinct regimes as a function of molar volume—for low and medium-density polymorphs, it is almost independent of volume, while for high-pressure phases a steep dependence is seen. A detailed analysis indicates that the increased short-range contributions to enthalpy in the high-density phases arise not only from an increased coordination number of silicon but also shorter Si-O bond lengths. Our results indicate that amorphous phases of silica exhibit better optimization of short-range interactions than crystalline phases at the same density while the magnitude of Coulombic contributions is lower in the amorphous phase.

  3. New investigations on shock-wave synthesized high-pressure phases in the system Si-Al-O-N

    Science.gov (United States)

    Schlothauer, T.; Greif, A.; Keller, K.; Schwarz, M. R.; Kroke, E.; Heide, G.

    2012-12-01

    The shock-wave synthesis of nanostructured high-pressure phases at a gram-scale permits the analysis of spinel type nitrides with different chemical composition using methods not suitable for microgram amounts of material. Methods with a significant mass loss through the analytical process like TG-MS or FT-IR or bulk methods at the g-scale like 29Si-MAS-NMR or neutron diffraction were used. The synthesis of pure high-pressure modifications (gamma-phases) of different SiAlON-compounds using amorphous H-bearing precursors at pressures of 30-40 GPa is a necessary prerequisite for precise determinations of crystal chemical features. Etching with HF is a well-known method to purify the high-pressure nitrides (Sekine 2002). The etched parts were analyzed by neutron diffraction, TG-MS, and carrier gas hot extraction (CGHE). Volatile elements like H2 and Cl2, as well as non-stoichiometric oxygen and nitrogen, and NOx, H2O are enriched in the disordered rims. This degassing process ends at temperatures of approximately 600°C, while the spinel structure remains well preserved up to 1300°C. Under these conditions the gamma-phases stay unchanged under air, argon and vacuum. Furthermore chlorine, an important impurity of the H-bearing precursors neither influences the synthesized products nor the synthesis process itself. IR-spectroscopy of gamma-Si3(O,N)4 shows that peak shifts of octahedral lattice vibrations (≈ 680 cm-1) and both tetrahedral vibrations (ny3 and ny4) (Jeanloz 1980, Preudhomme & Tarte 1971) to higher frequencies with decreasing oxygen content occur. This effect is also visible in samples contaminated with impurities of low pressure modifications. The more complex structure of gamma-SiAlON and the simultaneously exchange of the cation- and the anion-positions prevents the appearance of this important feature. Yet to be synthesized pure gamma-SiAlON using similar H-bearing precursors is necessary to resolve its structure. Sekine, T., H. He, T. Kobayashi, K

  4. Phase diagrams of exceptional and supersymmetric lattice gauge theories

    Energy Technology Data Exchange (ETDEWEB)

    Wellegehausen, Bjoern-Hendrik

    2012-07-10

    In this work different strongly-coupled gauge theories with and without fundamental matter have been studied on the lattice with an emphasis on the confinement problem and the QCD phase diagram at nonvanishing net baryon density as well as on possible supersymmetric extensions of the standard model of particle physics. In gauge theories with a non-trivial centre symmetry, as for instance SU(3)-Yang-Mills theory, confinement is intimately related to the centre of the gauge group, and the Polyakov loop serves as an order parameter for confinement. In QCD, this centre symmetry is explicitly broken by quarks in the fundamental representation of the gauge group. But still quarks and gluons are confined in mesons, baryons and glueballs at low temperatures and small densities, suggesting that centre symmetry is not responsible for the phenomenon of confinement. Therefore it is interesting to study pure gauge theories without centre symmetry. In this work this has been done by replacing the gauge group SU(3) of the strong interaction with the exceptional Lie group G{sub 2}, that has a trivial centre. To investigate G{sub 2} gauge theory on the lattice, a new and highly efficient update algorithm has been developed, based on a local HMC algorithm. Employing this algorithm, the proposed and already investigated first order phase transition from a confined to a deconfined phase has been confirmed, showing that indeed a first order phase transition without symmetry breaking or an order parameter is possible. In this context, also the deconfinement phase transition of the exceptional Lie groups F4 and E6 in three spacetime dimensions has been studied. It has been shown that both theories also possess a first order phase transition.

  5. Determining scaling in known phase diagrams of nonionic microemulsions to aid constructing unknown.

    Science.gov (United States)

    Balogh, Joakim

    2010-08-11

    Microemulsions based on nonionic surfactants of the ethylene oxide alkyl ether type C(m)E(n), have been studied thoroughly for around 30 years. Thanks to the considerable amount of published data available on these systems, it is possible to observe trends to make predictions of phase diagrams not yet determined. Strey and Kahlweit, and subsequently Sottmann and Strey, with coworkers have studied and published phase diagrams for systems with a fixed ratio of oil to water, varying the surfactant, the so-called Kahlweit fish-cut diagrams. Some properties of the phase diagrams can be scaled to become general and not system dependent. Here are shown two examples of scaling data from phase diagrams and the use of trends to determine phase diagrams, both inside and outside a dataset. The trends of microemulsions with fixed ratio of surfactant to oil, the so-called Lund-cut diagrams, are also investigated. The trends are used to determine a new phase diagram and this is compared with previously unpublished experimental data on C(12)E(5)-Octadecane-Water system. The scalings and trends make it possible to get good estimations of many of the important properties of the phase diagrams, both temperatures and surfactant concentrations of interest, by investigating one sample in the 3-phase region of the balanced fish-cut diagram.

  6. In-situ Phase Transformation and Deformation of Iron at High Pressure andTemperature

    Energy Technology Data Exchange (ETDEWEB)

    Miyagi, Lowell; Kunz, Martin; Knight, Jason; Nasiatka, James; Voltolini, Marco; Wenk, Hans-Rudolf

    2008-07-01

    With a membrane based mechanism to allow for pressure change of a sample in aradial diffraction diamond anvil cell (rDAC) and simultaneous infra-red laser heating, itis now possible to investigate texture changes during deformation and phasetransformations over a wide range of temperature-pressure conditions. The device isused to study bcc (alpha), fcc (gamma) and hcp (epislon) iron. In bcc iron, room temperature compression generates a texture characterized by (100) and (111) poles parallel to the compression direction. During the deformation induced phase transformation to hcp iron, a subset of orientations are favored to transform to the hcp structure first and generate a texture of (01-10) at high angles to the compression direction. Upon further deformation, the remaining grains transform, resulting in a texture that obeys the Burgers relationship of (110)bcc // (0001)hcp. This is in contrast to high temperature results that indicate that texture is developed through dominant pyramidal {2-1-12}<2-1-13> and basal (0001)-{2-1-10} slip based on polycrystal plasticity modeling. We also observe that the high temperature fcc phase develops a 110 texture typical for fcc metals deformed in compression.

  7. A route to possible civil engineering materials: the case of high-pressure phases of lime

    Science.gov (United States)

    Bouibes, A.; Zaoui, A.

    2015-07-01

    Lime system has a chemical composition CaO, which is known as thermodynamically stable. The purpose here is to explore further possible phases under pressure, by means of variable-composition ab initio evolutionary algorithm. The present investigation shows surprisingly new stable compounds of lime. At ambient pressure we predict, in addition to CaO, CaO2 as new thermodynamically stable compound. The latter goes through two phases transition from C2/c space group structure to Pna21 at 1.5 GPa, and Pna21 space group structure to I4/mcm at 23.4 GPa. Under increasing pressure, further compounds such as CaO3 become the most stable and stabilize in P-421m space group structure above 65 GPa. For the necessary knowledge of the new predicted compounds, we have computed their mechanical and electronic properties in order to show and to explain the main reasons leading to the structural changes.

  8. Elasticity of single-crystal superhydrous phase B at simultaneous high pressure-temperature conditions

    Science.gov (United States)

    Li, Xinyang; Mao, Zhu; Sun, Ningyu; Liao, Yifan; Zhai, Shuangmeng; Wang, Yi; Ni, Huaiwei; Wang, Jingyun; Tkachev, Sergey N.; Lin, Jung-Fu

    2016-08-01

    We investigated the combined effect of pressure and temperature on the elasticity of single-crystal superhydrous phase B (Shy-B) using Brillouin scattering and X-ray diffraction up to 12 GPa and 700 K. Using the obtained elasticity, we modeled the anisotropy of Shy-B along slab geotherms, showing that Shy-B has a low anisotropy and cannot be the major cause of the observed anisotropy in the region. Modeled velocities of Shy-B show that Shy-B will be shown as positive velocity anomalies at the bottom transition zone. Once Shy-B is transported to the topmost lower mantle, it will exhibit a seismic signature of lower velocities than topmost lower mantle. We speculate that an accumulation of hydrous phases, such as Shy-B, at the topmost lower mantle with a weight percentage of ~17-26% in the peridotite layer as subduction progresses could help explain the observed 2-3% low shear velocity anomalies in the region.

  9. A route to possible civil engineering materials: the case of high-pressure phases of lime.

    Science.gov (United States)

    Bouibes, A; Zaoui, A

    2015-07-23

    Lime system has a chemical composition CaO, which is known as thermodynamically stable. The purpose here is to explore further possible phases under pressure, by means of variable-composition ab initio evolutionary algorithm. The present investigation shows surprisingly new stable compounds of lime. At ambient pressure we predict, in addition to CaO, CaO2 as new thermodynamically stable compound. The latter goes through two phases transition from C2/c space group structure to Pna21 at 1.5 GPa, and Pna21 space group structure to I4/mcm at 23.4 GPa. Under increasing pressure, further compounds such as CaO3 become the most stable and stabilize in P-421m space group structure above 65 GPa. For the necessary knowledge of the new predicted compounds, we have computed their mechanical and electronic properties in order to show and to explain the main reasons leading to the structural changes.

  10. Raman Scattering Spectroscopy of Phase Transition in n-Pentadecane under High Temperature and High Pressure

    Institute of Scientific and Technical Information of China (English)

    QIAO Er-Wei; ZHENG Hai-Fei; XU Bei

    2009-01-01

    The Raman spectroscopy of n-pentadecane is investigated in a moissanite anvil cell at normal temperatures and a diamond anvil cell under pressure to about 3000 MPa and at temperature from 298 to 573 K. Result indicates that at room temperature the vibration modes, assigned to the symmetric and asymmetric stretching of CH3 and CH2 stretching, shift to higher frequency and display a pressure dependent quasi-linear curve. A liquid-solid phase transition appears at a pressure of 150 MPa. The high temperature solidus line of n-pentadecane follows a quadratic function of P = 0.02369T2 - 9.117T + 725.58, in agreement with previous conclusion derived from studies of other hydrocarbons. Upon phase transition, fitting the experimental data obtained in a temperature range of 283-553 K to the Clausius-Clapeyron equation allows one to define the thermodynamic parameters of n-pentadecane of dP/dT = 0.04738T - 9.117.

  11. High-pressure phase transition makes B4.3C boron carbide a wide-gap semiconductor

    Science.gov (United States)

    Hushur, Anwar; Manghnani, Murli H.; Werheit, Helmut; Dera, Przemyslaw; Williams, Quentin

    2016-02-01

    Single-crystal B4.3C boron carbide is investigated through the pressure-dependence and inter-relation of atomic distances, optical properties and Raman-active phonons up to ~70 GPa. The anomalous pressure evolution of the gap width to higher energies is striking. This is obtained from observations of transparency, which most rapidly increases around 55 GPa. Full visible optical transparency is approached at pressures of  >60 GPa indicating that the band gap reaches ~3.5 eV at high pressure, boron carbide is a wide-gap semiconductor. The reason is that the high concentration of structural defects controlling the electronic properties of boron carbide at ambient conditions initially decreases and finally vanishes at high pressures. The structural parameters and Raman-active phonons indicate a pressure-dependent phase transition in single-crystal natB4.3C boron carbide near 40 GPa, likely related to structural changes in the C-B-C chains, while the basic icosahedral structure appears to be less affected.

  12. High-pressure phase transition makes B4.3C boron carbide a wide-gap semiconductor.

    Science.gov (United States)

    Hushur, Anwar; Manghnani, Murli H; Werheit, Helmut; Dera, Przemyslaw; Williams, Quentin

    2016-02-01

    Single-crystal B4.3C boron carbide is investigated through the pressure-dependence and inter-relation of atomic distances, optical properties and Raman-active phonons up to ~70 GPa. The anomalous pressure evolution of the gap width to higher energies is striking. This is obtained from observations of transparency, which most rapidly increases around 55 GPa. Full visible optical transparency is approached at pressures of  >60 GPa indicating that the band gap reaches ~3.5 eV; at high pressure, boron carbide is a wide-gap semiconductor. The reason is that the high concentration of structural defects controlling the electronic properties of boron carbide at ambient conditions initially decreases and finally vanishes at high pressures. The structural parameters and Raman-active phonons indicate a pressure-dependent phase transition in single-crystal (nat)B4.3C boron carbide near 40 GPa, likely related to structural changes in the C-B-C chains, while the basic icosahedral structure appears to be less affected.

  13. A theoretical study of MgH2 ambient and high-pressure phases using NQCC parameters

    Science.gov (United States)

    Rafiee, Marjan A.

    2014-12-01

    Quadrupolar parameters of nuclei can be used as a tool to understand the electronic structure of the compounds. Magnesium hydride (MgH2) is a potential hydrogen storage material due to its outstanding hydrogen capacity, however, its high thermodynamic stability is unfavorable for dehydrogenation processes. Understanding the bonding nature of Mg and H is essential for improving its dehydrogenation performance. In this work the charge density distribution in MgH2 is studied. For this purpose, using calculated NQCCs of hydrogen atoms, the electronic structure of α-MgH2 with several high pressure forms of MgH2 were compared. The results show that in the high pressure phases (β, γ, and δ) some hydrogens have very small NQCC and therefore these hydrogens form weaker bond with Mg. In other words, easier condition for dehydrogenation in pressure-induced forms is expected. The electric field gradient (EFG) at the site of quadrupolar nuclei were calculated to obtain NQCC parameters using Gaussian 03 at B3LYP/6-31G level of theory. The selected level and basis set give the rather acceptable qualitative NQCCs of hydrogen atoms.

  14. Phase diagram for ortho-para-hydrogen monolayers

    CERN Document Server

    Sullivan, N S

    2003-01-01

    The phase diagram for orientational ordering of hydrogen monolayers on graphite and boron nitride is revised in view of current theory and experimental observations from nuclear magnetic resonance (NMR) studies recently reported for ortho-H sub 2 concentrations 0.35 <= c <= 0.92 and temperatures 0.14 <= T <= 1.80 K. The characteristic interaction coupling GAMMA sub 0 = 0.50 +- 0.03 K and the crystalline field amplitude V sub 0 = 0.70 +- 0.10 K are derived from experimental data, and distinct types of the local orientationally ordered structures are analysed using a proposed model for site-diluted uniaxial quadrupoles on a triangular plane lattice of hexagonal symmetry. The long-range periodic pinwheel structure and the short-range quadrupolar glass (QG) phase are stable above the 2D site-percolation limit, c sub p = 0.72, and for 0.48 < c < c sub p , respectively, where quadrupolar-order effects dominate. At very low T, the QG phase shows instability with respect to local dipole-like polariz...

  15. Pressure-temperature Phase Diagram of the Earth

    CERN Document Server

    Jones, Eriita

    2010-01-01

    Based on a pressure-temperature (P-T) phase diagram model of the Earth, Jones & Lineweaver (2010) described uninhabited terrestrial liquid water. Our model represents the atmosphere, surface, oceans and interior of the Earth - allowing the range of P-T conditions in terrestrial environments to be compared to the phase regime of liquid water. Here we present an overview and additional results from the Earth model on the location of the deepest liquid water on Earth and the maximum possible extent of the terrestrial biosphere. The intersection of liquid water and terrestrial phase space indicates that the deepest liquid water environments in the lithosphere occur at a depth of ~ 75 km. 3.5 % of the volume of the Earth is above 75 km depth. Considering the 3.5 % of the volume of the Earth where liquid water exists, ~ 12% of this volume is inhabited by life while the remaining ~ 88% is uninhabited. This is distinct from the fraction of the volume of liquid water occupied by life. We find that at least 1% of t...

  16. Predicted phase diagram of boron-carbon-nitrogen

    Science.gov (United States)

    Zhang, Hantao; Yao, Sanxi; Widom, Michael

    2016-04-01

    Noting the structural relationships between phases of carbon and boron carbide with phases of boron nitride and boron subnitride, we investigate their mutual solubilities using a combination of first-principles total energies supplemented with statistical mechanics to address finite temperatures. Thus we predict the solid-state phase diagram of boron-carbon-nitrogen (B-C-N). Owing to the large energy costs of substitution, we find that the mutual solubilities of the ultrahard materials diamond and cubic boron nitride are negligible, and the same for the quasi-two-dimensional materials graphite and hexagonal boron nitride. In contrast, we find a continuous range of solubility connecting boron carbide to boron subnitride at elevated temperatures. An electron-precise ternary compound B13CN consisting of B12 icosahedra with NBC chains is found to be stable at all temperatures up to melting. It exhibits an order-disorder transition in the orientation of NBC chains at approximately T =500 K. We also propose that the recently discovered binary B13N2 actually has composition B12.67N2 .

  17. Dynamical charge density waves rule the phase diagram of cuprates

    Science.gov (United States)

    Caprara, S.; Di Castro, C.; Seibold, G.; Grilli, M.

    2017-06-01

    In the last few years, charge density waves (CDWs) have been ubiquitously observed in high-temperature superconducting cuprates and are now the most investigated among the competing orders in the still hot debate on these systems. A wealth of new experimental data raises several fundamental issues that challenge the various theoretical proposals. We here relate our mean-field instability line TCDW0 of a strongly correlated Fermi liquid to the pseudogap T*(p ) line, marking in this way the onset of CDW-fluctuations. These fluctuations reduce strongly the mean-field critical line. Controlling this reduction via an infrared frequency cutoff related to the characteristic time of the probes, we account for the complex experimental temperature versus doping phase diagram. We provide a coherent scenario explaining why different CDW onset curves are observed by different experimental probes and seem to extrapolate at zero temperature into seemingly different quantum critical points (QCPs) in the intermediate and overdoped region. The nearly singular anisotropic scattering mediated by these fluctuations also accounts for the rapid changes of the Hall number seen in experiments and provides the first necessary step for a possible Fermi surface reconstruction fully establishing at lower doping. Finally, we show that phase fluctuations of the CDWs, which are enhanced in the presence of strong correlations near the Mott insulating phase, naturally account for the disappearance of the CDWs at low doping with yet another QCP as seen by the experiments.

  18. Sedimentation stacking diagram of binary colloidal mixtures and bulk phases in the plane of chemical potentials.

    Science.gov (United States)

    de las Heras, Daniel; Schmidt, Matthias

    2015-05-20

    We give a full account of a recently proposed theory that explicitly relates the bulk phase diagram of a binary colloidal mixture to its phase stacking phenomenology under gravity (de las Heras and Schmidt 2013 Soft Matter 9 8636). As we demonstrate, the full set of possible phase stacking sequences in sedimentation-diffusion equilibrium originates from straight lines (sedimentation paths) in the chemical potential representation of the bulk phase diagram. From the analysis of various standard topologies of bulk phase diagrams, we conclude that the corresponding sedimentation stacking diagrams can be very rich, even more so when finite sample height is taken into account. We apply the theory to obtain the stacking diagram of a mixture of nonadsorbing polymers and colloids. We also present a catalog of generic phase diagrams in the plane of chemical potentials in order to facilitate the practical application of our concept, which also generalizes to multi-component mixtures.

  19. Flash flow pyrolysis: mimicking flash vacuum pyrolysis in a high-temperature/high-pressure liquid-phase microreactor environment.

    Science.gov (United States)

    Cantillo, David; Sheibani, Hassan; Kappe, C Oliver

    2012-03-02

    Flash vacuum pyrolysis (FVP) is a gas-phase continuous-flow technique where a substrate is sublimed through a hot quartz tube under high vacuum at temperatures of 400-1100 °C. Thermal activation occurs mainly by molecule-wall collisions with contact times in the region of milliseconds. As a preparative method, FVP is used mainly to induce intramolecular high-temperature transformations leading to products that cannot easily be obtained by other methods. It is demonstrated herein that liquid-phase high-temperature/high-pressure (high-T/p) microreactor conditions (160-350 °C, 90-180 bar) employing near- or supercritical fluids as reaction media can mimic the results obtained using preparative gas-phase FVP protocols. The high-T/p liquid-phase "flash flow pyrolysis" (FFP) technique was applied to the thermolysis of Meldrum's acid derivatives, pyrrole-2,3-diones, and pyrrole-2-carboxylic esters, producing the expected target heterocycles in high yields with residence times between 10 s and 10 min. The exact control over flow rate (and thus residence time) using the liquid-phase FFP method allows a tuning of reaction selectivities not easily achievable using FVP. Since the solution-phase FFP method does not require the substrate to be volatile any more--a major limitation in classical FVP--the transformations become readily scalable, allowing higher productivities and space-time yields compared with gas-phase protocols. Differential scanning calorimetry measurements and extensive DFT calculations provided essential information on pyrolysis energy barriers and the involved reaction mechanisms. A correlation between computed activation energies and experimental gas-phase FVP (molecule-wall collisions) and liquid-phase FFP (molecule-molecule collisions) pyrolysis temperatures was derived.

  20. Isolation and determination of deoxynivalenol by reversed-phase high-pressure liquid chromatography.

    Science.gov (United States)

    Gupta, Vikas Kumar; Chattopadhyay, Pronobesh; Kalita, Mohan Ch; Chaurasia, Asshwani Kumar; Gogoi, Hemanta Kumar; Singh, Lokendra

    2011-01-01

    Deoxynivalenol (DON) is a mycotoxin produced by food contamination. It is a pharmacologically active compound that acts on the serotonin receptor, leading to several neuroendocrine and hematological disorders. In this article we describe a simple, accurate, and sensitive method for the quantification of DON. DON was quantified using a Phenomenex(®) ODS analytical C18 column (150 mm × 46 mm, 5 μm) with a mobile phase composed of mixture of water-acetonitrile-methanol (5:4:1, v/v/v) at a flow rate of 1.5 ml/min and at 254 nm in an ultraviolet (UV) detector The method has been validated with isolated samples of DON and provides a tool for the control of substandard and counterfeit commercial food products.

  1. Laser-driven formation of a high-pressure phase in amorphous silica

    Energy Technology Data Exchange (ETDEWEB)

    Salleo, Alberto; Taylor, Seth T.; Martin, Michael C.; Panero, Wendy R.; Jeanloz, Raymond; Genin, Francois Y.; Sands, Timothy

    2002-05-31

    A combination of electron diffraction and infrared reflectance measurements shows that synthetic silica transforms partially into stishovite under high-intensity (GW/cm2) laser irradiation, probably by the formation of a dense ionized plasma above the silica surface. During the transformation the silicon coordination changes from four-fold to six-fold and the silicon-oxygen bond changes from mostly covalent to mostly ionic, such that optical properties of the transformed material differ significantly from those of the original glass. This phase transformation offers one suitable mechanism by which laser-induced damage grows catastrophically once initiated, thereby dramatically shortening the service lifetime of optics used for high-power photonics applications such as inertial confinement fusion.

  2. Matrix model approximations of fuzzy scalar field theories and their phase diagrams

    Energy Technology Data Exchange (ETDEWEB)

    Tekel, Juraj [Department of Theoretical Physics, Faculty of Mathematics, Physics and Informatics, Comenius University, Mlynska Dolina, Bratislava, 842 48 (Slovakia)

    2015-12-29

    We present an analysis of two different approximations to the scalar field theory on the fuzzy sphere, a nonperturbative and a perturbative one, which are both multitrace matrix models. We show that the former reproduces a phase diagram with correct features in a qualitative agreement with the previous numerical studies and that the latter gives a phase diagram with features not expected in the phase diagram of the field theory.

  3. Evaluation of the Current Status of the Combinatorial Approach for the Study of Phase Diagrams.

    Science.gov (United States)

    Wong-Ng, W

    2012-01-01

    This paper provides an evaluation of the effectiveness of using the high throughput combinatorial approach for preparing phase diagrams of thin film and bulk materials. Our evaluation is based primarily on examples of combinatorial phase diagrams that have been reported in the literature as well as based on our own laboratory experiments. Various factors that affect the construction of these phase diagrams are examined. Instrumentation and analytical approaches needed to improve data acquisition and data analysis are summarized.

  4. THE GENERALIZED MAXIMUM LIKELIHOOD METHOD APPLIED TO HIGH PRESSURE PHASE EQUILIBRIUM

    Directory of Open Access Journals (Sweden)

    Lúcio CARDOZO-FILHO

    1997-12-01

    Full Text Available The generalized maximum likelihood method was used to determine binary interaction parameters between carbon dioxide and components of orange essential oil. Vapor-liquid equilibrium was modeled with Peng-Robinson and Soave-Redlich-Kwong equations, using a methodology proposed in 1979 by Asselineau, Bogdanic and Vidal. Experimental vapor-liquid equilibrium data on binary mixtures formed with carbon dioxide and compounds usually found in orange essential oil were used to test the model. These systems were chosen to demonstrate that the maximum likelihood method produces binary interaction parameters for cubic equations of state capable of satisfactorily describing phase equilibrium, even for a binary such as ethanol/CO2. Results corroborate that the Peng-Robinson, as well as the Soave-Redlich-Kwong, equation can be used to describe phase equilibrium for the following systems: components of essential oil of orange/CO2.Foi empregado o método da máxima verossimilhança generalizado para determinação de parâmetros de interação binária entre os componentes do óleo essencial de laranja e dióxido de carbono. Foram usados dados experimentais de equilíbrio líquido-vapor de misturas binárias de dióxido de carbono e componentes do óleo essencial de laranja. O equilíbrio líquido-vapor foi modelado com as equações de Peng-Robinson e de Soave-Redlich-Kwong usando a metodologia proposta em 1979 por Asselineau, Bogdanic e Vidal. A escolha destes sistemas teve como objetivo demonstrar que o método da máxima verosimilhança produz parâmetros de interação binária, para equações cúbicas de estado capazes de descrever satisfatoriamente até mesmo o equilíbrio para o binário etanol/CO2. Os resultados comprovam que tanto a equação de Peng-Robinson quanto a de Soave-Redlich-Kwong podem ser empregadas para descrever o equilíbrio de fases para o sistemas: componentes do óleo essencial de laranja/CO2.

  5. Investigation of influence of coal properties on dense-phase pneumatic conveying at high pressure

    Institute of Scientific and Technical Information of China (English)

    Cai Liang; Xiaoxu Xie; Pan Xu; Xiaoping Chen; Changsui Zhao; Xin Wu

    2012-01-01

    Experiments of dense-phase pneumatic conveying of pulverized coal using nitrogen were carried out in a test facility at pressures of up to 3.7 MPa to study the effects of coal type,particle size and moisture content on flow characteristics.The Jenike shear test and scanning electron microscopy (SEM) were employed to provide a better understanding of effects of the material properties on flow characteristics.Two kinds of pulverized coals,Yanzhou and Datong,with similar particle size,moisture content and density,were used in the test.Pressure drop increases with increasing the particle size at similar solid-gas ratio,superficial velocity and pressure in the receiving hopper,and pressure drops through different test sections decrease firstly and then rise with increasing the conveying velocity for the same particle size,mass flow rate and pressure in the receiving hopper.The flowability of pulverized coal decreases with increasing the moisture content in the range from 3.24% to 8.18%.Unconfined yield strength (UYS) increases and flow function (FF) decreases with increasing the moisture content.Results of the shearing tests are consistent with the results of the conveying study.Pressure drops through different test sections are discussed and analyzed.

  6. Theoretical predictions of novel superconducting phases of BaGe3 stable at atmospheric and high pressures.

    Science.gov (United States)

    Zurek, Eva; Yao, Yansun

    2015-03-16

    A series of new superconducting binary silicides and germanides have recently been synthesized under high-pressure high-temperature conditions. A representative member of this group, BaGe3, was theoretically investigated using evolutionary structure searches coupled with structural analogies in the pressure range from 1 atm to 250 GPa, where three new phases were discovered. At 1 atm, in addition to the synthesized P63/mmc phase, we predicted two new phases, I4/mmm and Amm2, to be dynamically stable. The Amm2 structure comprises Ge clusters and triangular prisms intercalated with Ba and Ge atoms, a unique structural motif unknown to this group. The I4/mmm structure has been previously synthesized in binary silicides and is calculated to be thermodynamically stable in BaGe3 between 15.6 and 35.4 GPa. Above 35.4 GPa, two new phases of P6̅m2 and R3̅m symmetry become the global minima and remain so up to the highest pressure considered. These two phases have very similar enthalpies, and both feature layers of double Kagome nets of Ge intercalated with Ba-Ge layers. The predicted phases are suggested to be metallic with itinerant electrons and to be potentially superconducting from the considerable electron-phonon coupling strength. Density functional perturbation calculations combined with the Allen-Dynes-modified McMillan formula were used to estimate the superconducting critical temperatures (Tc) for these new phases, which, with slight pressure variations, are comparable to the experimental Tc measured for the P63/mmc phase.

  7. The Collins Model and the Eutectic-Type and the Peritectic-Type Phase Diagrams

    Institute of Scientific and Technical Information of China (English)

    XIE Chuan-Mei; CHEN Li-Rong

    2003-01-01

    From the Gibbs free energy and the equations of two-phase equilibrium curves of the two-dimensionalbinary system which has the Lennard-Jones potential, using the Collins model, the eutectic-type phase diagram and theperitectic-type phase diagram of the binary system are obtained, whose results are quite similar to the behavior of thethree-dimensional (3D) substances.

  8. A Closer Look at Phase Diagrams for the General Chemistry Course.

    Science.gov (United States)

    Gramsch, Stephen A.

    2000-01-01

    Information concerning structural chemistry and phase equilibria contained in the full phase diagrams of common substances is a great deal richer than the general chemistry students are given to believe. Discusses ways of enriching the traditional presentation of phase diagrams in general chemistry courses. (Contains over 20 references.) (WRM)

  9. Self-annealing in a two-phase Pb-Sn alloy after processing by high-pressure torsion

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Nian Xian [Materials Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ (United Kingdom); Chinh, Nguyen Q. [Department of Materials Physics, Eötvös Loránd University, 1117 Budapest, Pázmány Péter s. 1/A. (Hungary); Kawasaki, Megumi [Division of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Departments of Aerospace & Mechanical Engineering and Materials Science, University of Southern California, Los Angeles, CA 90089-1453 (United States); Huang, Yi, E-mail: Y.Huang@soton.ac.uk [Materials Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ (United Kingdom); Langdon, Terence G. [Materials Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ (United Kingdom); Departments of Aerospace & Mechanical Engineering and Materials Science, University of Southern California, Los Angeles, CA 90089-1453 (United States)

    2016-06-01

    A Pb-62% Sn two-phase eutectic alloy was processed by high-pressure torsion (HPT) and stored at room temperature (RT) to investigate the occurrence of self-annealing. The microstructural characteristics and mechanical properties were recorded during self-annealing using scanning electron microscopy, tensile testing and nanoindentation. Processing by HPT produces a weakening effect but storage at RT leads to a gradual increase in the hardness together with significant grain growth. Nanoindentation tests were performed by applying both the indentation depth-time (h-t) relationship at the holding stage and the hardness, H, at various loading rates in order to explore the evolution of the strain rate sensitivity (SRS), m. The results obtained by tensile testing and nanoindentation are consistent despite the large difference in the volumes of the examined regions, thereby confirming the validity of using nanoindentation to measure the strain rate sensitivity.

  10. Phase transition in layered perovskite-like manganate Ca3Mn2O7 under high pressure

    Institute of Scientific and Technical Information of China (English)

    朱嘉林; 陈良辰; 禹日成; 李凤英; 刘景; 靳常青

    2002-01-01

    In situ high pressure energy dispersive X-ray diffraction measurements on the layered perovskite-like manganate Ca3Mn2O7 powder under pressures were performed by using the diamond anvil cell with synchrotron radiation. The results show that the structure of layered perovskite-like manganate Ca3Mn2O7 is unstable under pressure due to the easy compression of NaCl-type blocks. The structure of Ca3Mn2O7 underwent two phase transitions under pressures in the range of 0-35 GPa. One was at about 1.3 GPa with the crystal structure changing from tetragonal to orthorhombic. The other was at about 9.5 GPa with the crystal structure changing from orthorhombic back to another tetragonal.

  11. Phase diagram of the half-filled ionic Hubbard model

    Science.gov (United States)

    Bag, Soumen; Garg, Arti; Krishnamurthy, H. R.

    2015-06-01

    We study the phase diagram of the ionic Hubbard model (IHM) at half filling on a Bethe lattice of infinite connectivity using dynamical mean-field theory (DMFT), with two impurity solvers, namely, iterated perturbation theory (IPT) and continuous time quantum Monte Carlo (CTQMC). The physics of the IHM is governed by the competition between the staggered ionic potential Δ and the on-site Hubbard U . We find that for a finite Δ and at zero temperature, long-range antiferromagnetic (AFM) order sets in beyond a threshold U =UA F via a first-order phase transition. For U smaller than UA F the system is a correlated band insulator. Both methods show a clear evidence for a quantum transition to a half-metal (HM) phase just after the AFM order is turned on, followed by the formation of an AFM insulator on further increasing U . We show that the results obtained within both methods have good qualitative and quantitative consistency in the intermediate-to-strong-coupling regime at zero temperature as well as at finite temperature. On increasing the temperature, the AFM order is lost via a first-order phase transition at a transition temperature TA F(U ,Δ ) [or, equivalently, on decreasing U below UA F(T ,Δ ) ], within both methods, for weak to intermediate values of U /t . In the strongly correlated regime, where the effective low-energy Hamiltonian is the Heisenberg model, IPT is unable to capture the thermal (Neel) transition from the AFM phase to the paramagnetic phase, but the CTQMC does. At a finite temperature T , DMFT +CTQMC shows a second phase transition (not seen within DMFT +IPT ) on increasing U beyond UA F. At UN>UA F , when the Neel temperature TN for the effective Heisenberg model becomes lower than T , the AFM order is lost via a second-order transition. For U ≫Δ , TN˜t2/U (1 -x2) , where x =2 Δ /U and thus TN increases with increase in Δ /U . In the three-dimensional parameter space of (U /t ,T /t ,andΔ /t ) , as T increases, the surface of first

  12. First principles prediction of a new high-pressure phase and transport properties of Mg2Si

    Science.gov (United States)

    Kessair, S.; Arbouche, O.; Amara, K.; Benallou, Y.; Azzaz, Y.; Zemouli, M.; Bekki, M.; Ameri, M.; Bouazza, B. S.

    2016-12-01

    We have investigated the structural properties of seven different structure types of Mg2Si which include the cubic CaF2, orthorhombic PbCl2, hexagonal Ni2In, tetragonal Al2Cu, Laves phase (cubic MgCu2), hexagonal MgZn2 and dihexagonal MgNi2 type of structures, using a full potential linearized augmented plane wave method as implemented in WIEN2k within the framework of density functional theory. The exchange-correlation potential is treated by the new form of generalized gradient approximation (GGA-PBEsol). In total energy calculations it is clearly seen that cubic CaF2-type structure is stable at ambient conditions, and it undergoes a first-order phase transition to orthorhombic PbCl2-type, then to the hexagonal Ni2In-type structure and finally to the cubic Laves phase MgCu2-type. A new structure type is predicted to be stable at high pressure. Moreover, we intend to combine the electronic structure calculations performed by mean of generalized gradient approximation and modified Becke-Johnson potential with Boltzmann transport theory as incorporated in BoltzTraP code to interpret and predict the thermoelectric performance of each stable phase as a function of the chemical potential at various temperatures. We find a high thermoelectric thermopower values in cubic CaF2-type structure that could promise an excellent candidate for potential thermoelectric applications.

  13. Temperature-pressure phase diagram of cubic Laves phase Au2Pb

    Science.gov (United States)

    Chen, K. W.; Graf, D.; Besara, T.; Gallagher, A.; Kikugawa, N.; Balicas, L.; Siegrist, T.; Shekhter, A.; Baumbach, R. E.

    2016-01-01

    The temperature (T ) as a function of pressure (P ) phase diagram is reported for the cubic Laves phase compound Au2Pb, which was recently proposed to support linearly dispersing topological bands, together with conventional quadratic bands. At ambient pressure, Au2Pb exhibits several structural phase transitions at T1=97 K , T2=51 K , and T3=40 K with superconductivity below Tc=1.2 K . Applied pressure results in a rich phase diagram where T1,T2, and T3 evolve strongly with P and a possible new phase is stabilized for P >0.64 GPa that also supports superconductivity below 1.1 K. These observations suggest that Au2Pb is an ideal system in which to investigate the relationship between structural degrees of freedom, band topology, and resulting anomalous behaviors.

  14. Phase diagrams and kinetics of solid-liquid phase transitions in crystalline polymer blends

    Science.gov (United States)

    Matkar, Rushikesh A.

    A free energy functional has been formulated based on an order parameter approach to describe the competition between liquid-liquid phase separation and solid-liquid phase separation. In the free energy description, the assumption of complete solvent rejection from the crystalline phase that is inherent in the Flory diluent theory was removed as solvent has been found to reside in the crystalline phase in the form of intercalates. Using this approach, we have calculated various phase diagrams in binary blends of crystalline and amorphous polymers that show upper or lower critical solution temperature. Also, the discrepancy in the chi values obtained from different experimental methods reported in the literature for the polymer blend of poly(vinylidenefluoride) and poly(methylmethacrylate) has been discussed in the context of the present model. Experimental phase diagram for the polymer blend of poly(caprolactone) and polystyrene has also been calculated. Of particular importance is that the crystalline phase concentration as a function of temperature has been calculated using free energy minimization methods instead of assuming it to be pure. In the limit of complete immiscibility of the solvent in the crystalline phase, the Flory diluent theory is recovered. The model is extended to binary crystalline blends and the formation of eutectic, peritectic and azeotrope phase diagrams has been explained on the basis of departure from ideal solid solution behavior. Experimental eutectic phase diagram from literature of a binary blend of crystalline polymer poly(caprolactone) and trioxane were recalculated using the aforementioned approach. Furthermore, simulations on the spatio temporal dynamics of crystallization in blends of crystalline and amorphous polymers were carried out using the Ginzburg-Landau approach. These simulations have provided insight into the distribution of the amorphous polymer in the blends during the crystallization process. The simulated results

  15. Reinvestigation of the Cd–Gd phase diagram

    Science.gov (United States)

    Reichmann, Thomas L.; Ipser, Herbert

    2014-01-01

    The complete Cd–Gd equilibrium phase diagram was investigated by a combination of powder-XRD, SEM and DTA. All previously reported phases, i.e., CdGd, Cd2Gd, Cd3Gd, Cd45Gd11, Cd58Gd13, and Cd6Gd, could be confirmed. In addition, a new intermetallic compound with a stoichiometric composition corresponding to “Cd8Gd” was found to exist. It was obtained that “Cd8Gd” decomposes peritectically at 465 °C. Homogeneity ranges of all intermetallic compounds were determined at distinct temperatures. In addition, the maximum solubilities of Cd in the low- and high-temperature modifications of Gd were determined precisely as 4.6 and 22.6 at.%, respectively. All invariant reaction temperatures (with the exception of the formation of Cd58Gd13) as well as liquidus temperatures were determined, most probably, Cd58Gd13 is formed in a peritectoid reaction from Cd45Gd11 and Cd6Gd at a temperature below 700 °C. PMID:25544803

  16. Reinvestigation of the Cd-Gd phase diagram.

    Science.gov (United States)

    Reichmann, Thomas L; Ipser, Herbert

    2014-12-25

    The complete Cd-Gd equilibrium phase diagram was investigated by a combination of powder-XRD, SEM and DTA. All previously reported phases, i.e., CdGd, Cd2Gd, Cd3Gd, Cd45Gd11, Cd58Gd13, and Cd6Gd, could be confirmed. In addition, a new intermetallic compound with a stoichiometric composition corresponding to "Cd8Gd" was found to exist. It was obtained that "Cd8Gd" decomposes peritectically at 465 °C. Homogeneity ranges of all intermetallic compounds were determined at distinct temperatures. In addition, the maximum solubilities of Cd in the low- and high-temperature modifications of Gd were determined precisely as 4.6 and 22.6 at.%, respectively. All invariant reaction temperatures (with the exception of the formation of Cd58Gd13) as well as liquidus temperatures were determined, most probably, Cd58Gd13 is formed in a peritectoid reaction from Cd45Gd11 and Cd6Gd at a temperature below 700 °C.

  17. Energy spectrum and phase diagrams of two-sublattice hard-core boson model

    Directory of Open Access Journals (Sweden)

    I.V. Stasyuk

    2013-06-01

    Full Text Available The energy spectrum, spectral density and phase diagrams have been obtained for two-sublattice hard-core boson model in frames of random phase approximation approach. Reconstruction of boson spectrum at the change of temperature, chemical potential and energy difference between local positions in sublattices is studied. The phase diagrams illustrating the regions of existence of a normal phase which can be close to Mott-insulator (MI or charge-density (CDW phase diagrams as well as the phase with the Bose-Einstein condensate (SF phase are built.

  18. Solid-liquid phase diagram of disubstituted benzene systems

    Institute of Scientific and Technical Information of China (English)

    黑恩成; 刘国杰

    1995-01-01

    The cooling curves of different compositions of the systems of ortho-chlorotoluene/para-chlorotoluene and ortho-nitrochlorobenzene/para-nitrochlorobenzene are carefully determined by the thermal analysis method. The crystals obtained are also tested. The conclusion that both systems are of simple eutectic diagram but not the solid solution diagram with a minimum melting point is confirmed. The characteristics of the diagram are explained according to the physical and thermodynarmc properties of the components.

  19. Inhomogeneous hard-core bosonic mixture with checkerboard supersolid phase: Quantum and thermal phase diagram

    Science.gov (United States)

    Heydarinasab, F.; Abouie, J.

    2017-09-01

    We introduce an inhomogeneous bosonic mixture composed of two kinds of hard-core and semi-hard-core bosons with different nilpotency conditions and demonstrate that in contrast with the standard hard-core Bose-Hubbard model, our bosonic mixture with nearest- and next-nearest-neighbor interactions on a square lattice develops the checkerboard supersolid phase characterized by the simultaneous superfluid and checkerboard solid orders. Our bosonic mixture is created from a two-orbital Bose-Hubbard model including two kinds of bosons: a single-orbital boson and a two-orbital boson. By mapping the bosonic mixture to an anisotropic inhomogeneous spin model in the presence of a magnetic field, we study the ground-state phase diagram of the model by means of cluster mean field theory and linear spin-wave theory and show that various phases such as solid, superfluid, supersolid, and Mott insulator appear in the phase diagram of the mixture. Competition between the interactions and magnetic field causes the mixture to undergo different kinds of first- and second-order phase transitions. By studying the behavior of the spin-wave excitations, we find the reasons of all first- and second-order phase transitions. We also obtain the temperature phase diagram of the system using cluster mean field theory. We show that the checkerboard supersolid phase persists at finite temperature comparable with the interaction energies of bosons.

  20. Exact ground-state phase diagrams for the spin-3/2 Blume Emery Griffiths model

    Science.gov (United States)

    Canko, Osman; Deviren, Bayram; Keskin, Mustafa

    2008-05-01

    We have calculated the exact ground-state phase diagrams of the spin-3/2 Ising model using the method that was proposed and applied to the spin-1 Ising model by Dublenych (2005 Phys. Rev. B 71 012411). The calculated, exact ground-state phase diagrams on the diatomic and triangular lattices with the nearest-neighbor (NN) interaction have been presented in this paper. We have obtained seven and 15 topologically different ground-state phase diagrams for J>0 and Jnon-uniform phases. We have also constructed the exact ground-state phase diagrams of the model on the triangular lattice and found 20 and 59 fundamental phase diagrams for J>0 and J<0, respectively, the conditions for the existence of uniform and intermediate phases have also been found.

  1. Phase stability in nanoscale material systems: extension from bulk phase diagrams.

    Science.gov (United States)

    Bajaj, Saurabh; Haverty, Michael G; Arróyave, Raymundo; Goddard, William A; Shankar, Sadasivan

    2015-06-07

    Phase diagrams of multi-component systems are critical for the development and engineering of material alloys for all technological applications. At nano dimensions, surfaces (and interfaces) play a significant role in changing equilibrium thermodynamics and phase stability. In this work, it is shown that these surfaces at small dimensions affect the relative equilibrium thermodynamics of the different phases. The CALPHAD approach for material surfaces (also termed "nano-CALPHAD") is employed to investigate these changes in three binary systems by calculating their phase diagrams at nano dimensions and comparing them with their bulk counterparts. The surface energy contribution, which is the dominant factor in causing these changes, is evaluated using the spherical particle approximation. It is first validated with the Au-Si system for which experimental data on phase stability of spherical nano-sized particles is available, and then extended to calculate phase diagrams of similarly sized particles of Ge-Si and Al-Cu. Additionally, the surface energies of the associated compounds are calculated using DFT, and integrated into the thermodynamic model of the respective binary systems. In this work we found changes in miscibilities, reaction compositions of about 5 at%, and solubility temperatures ranging from 100-200 K for particles of sizes 5 nm, indicating the importance of phase equilibrium analysis at nano dimensions.

  2. High-field phase-diagram of Fe arsenide superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Jo, Y.J.; Jaroszynski, J.; Yamamoto, A.; Gurevich, A.; Riggs, S.C.; Boebinger, G.S.; Larbalestier, D. [National High Magnetic Field Laboratory, Florida State University, Tallahassee-FL 32310 (United States); Wen, H.H. [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Zhigadlo, N.D.; Katrych, S.; Bukowski, Z.; Karpinski, J. [Laboratory for Solid State Physics, ETH Zuerich, CH-8093 Zuerich (Switzerland); Liu, R.H.; Chen, H.; Chen, X.H. [Hefei National Laboratory for Physical Science a Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Balicas, L., E-mail: balicas@magnet.fsu.ed [National High Magnetic Field Laboratory, Florida State University, Tallahassee-FL 32310 (United States)

    2009-05-01

    Here, we report an overview of the phase-diagram of single-layered and double-layered Fe arsenide superconductors at high magnetic fields. Our systematic magneto-transport measurements of polycrystalline SmFeAsO{sub 1-x}F{sub x} at different doping levels confirm the upward curvature of the upper critical magnetic field H{sub c2}(T) as a function of temperature T defining the phase boundary between the superconducting and metallic states for crystallites with the ab planes oriented nearly perpendicular to the magnetic field. We further show from measurements on single-crystals that this feature, which was interpreted in terms of the existence of two superconducting gaps, is ubiquitous among both series of single- and double-layered compounds. In all compounds explored by us the zero temperature upper critical field H{sub c2}(0), estimated either through the Ginzburg-Landau or the Werthamer-Helfand-Hohenberg single gap theories, strongly surpasses the weak-coupling Pauli paramagnetic limiting field. This clearly indicates the strong-coupling nature of the superconducting state and the importance of magnetic correlations for these materials. Our measurements indicate that the superconducting anisotropy, as estimated through the ratio of the effective masses gamma = (m{sub c}/m{sub ab}){sup 1/2} for carriers moving along the c-axis and the ab-planes, respectively, is relatively modest as compared to the high-T{sub c} cuprates, but it is temperature, field and even doping dependent. Finally, our preliminary estimations of the irreversibility field H{sub m}(T), separating the vortex-solid from the vortex-liquid phase in the single-layered compounds, indicates that it is well described by the melting of a vortex lattice in a moderately anisotropic uniaxial superconductor.

  3. High-temperature- and high-pressure-induced formation of the Laves-phase compound XeS2

    Science.gov (United States)

    Yan, Xiaozhen; Chen, Yangmei; Xiang, Shikai; Kuang, Xiaoyu; Bi, Yan; Chen, Haiyan

    2016-06-01

    We explore the reactivity of xenon with sulfur under high pressure, using unbiased structure searching techniques combined with first-principles calculations, which identify a stable XeS2 compound crystallized in a Laves phase with hypercoordinated (16-fold) Xe at 191 GPa and 0 K. Taking the thermal effects into account, we find that increasing the temperature could further stabilize it. The formation of XeS2 is a consequence of pressure-induced charge transfer from Xe to S atoms and the delocalization of Xe 5 p and S 3 p electrons. Meanwhile, the stabilization into a Laves phase of XeS2 is the result of delocalized chemical bonding and the need for optimum structure packing. The present discussion of the formation mechanism in XeS2 is general, and conclusions can be used to understand the formation of other Laves-phase compounds and the Xe chemistry that allows closed-shell Xe to participate in chemical reactions.

  4. influence of the molecular structures on the high-pressure and low-temperature phase transitions of plastic crystals.

    Science.gov (United States)

    Wunschel, Markus; Dinnebier, Robert E; Carlson, Stefan; Bernatowicz, Piotr; van Smaalen, Sander

    2003-02-01

    The crystal structures of tert-butyl-tris(trimethylsilyl)silane, Si[C(CH(3))(3)](1)[Si(CH(3))(3)](3) (Bu1), and di-tert-butyl-bis(trimethylsilyl)silane, Si[C(CH(3))(3)](2)[Si(CH(3))(3)](2) (Bu2), at room temperature and at 105 K have been determined by X-ray powder diffraction; the high-pressure behavior for pressures between 0 and 5 GPa is reported. The room-temperature structures have cubic Fm3m symmetry (Z = 4) with a = 13.2645 (2) A, V = 2333.87 (4) A(3) for Bu1 and a = 12.9673 (1) A, V = 2180.46 (3) A(3) for Bu2. The molecules are arranged in a cubic close packing (c.c.p.) and exhibit at least 48-fold orientational disorder. Upon cooling both compounds undergo a first-order phase transition at temperatures T(c) = 230 (5) K (Bu1) and T(c) = 250 (5) K (Bu2) into monoclinic structures with space group P2(1)/n. The structures at 105 K have a = 17.317 (1), b = 15.598 (1), c = 16.385 (1) A, gamma = 109.477 (4) degrees, V = 4172.7 (8) A(3) and Z = 8 for Bu1and a = 17.0089 (9), b = 15.3159 (8), c = 15.9325 (8) A, gamma = 110.343 (3) degrees, V = 3891.7 (5) A(3) and Z = 8 for Bu2. The severe disorder of the room-temperature phase is significantly decreased and only a two- or threefold rotational disorder of the molecules remains at 105 K. First-order phase transitions have been observed at pressures of 0.13-0.28 GPa for Bu1 and 0.20-0.24 GPa for Bu2. The high-pressure structures are isostructural to the low-temperature structures. The pressure dependencies of the unit-cell Volumes were fitted with Vinet equations of state and the bulk moduli were obtained. At still higher pressures further anomalies in the pressure dependencies of the lattice parameters were observed. These anomalies are explained as additional disorder-order phase transitions.

  5. Helicity, anisotropies, and their competition in a multiferroic magnet: Insight from the phase diagram

    Science.gov (United States)

    Gvozdikova, M. V.; Ziman, T.; Zhitomirsky, M. E.

    2016-07-01

    Motivated by the complex phase diagram of MnWO4, we investigate the competition between anisotropy, magnetic field, and helicity for the anisotropic next-nearest-neighbor Heisenberg model. Apart from two competing exchanges, which favor a spiral magnetic structure, the model features the biaxial single-ion anisotropy. The model is treated in the real-space mean-field approximation and the phase diagram containing various incommensurate and commensurate states is obtained for different field orientations. We discuss the similarities and differences of the theoretical phase diagram and the experimental diagram of MnWO4.

  6. Induced smectic phases in phase diagrams of binary nematic liquid crystal mixtures.

    Science.gov (United States)

    Huang, Tsang-Min; McCreary, Kathleen; Garg, Shila; Kyu, Thein

    2011-03-28

    To elucidate induced smectic A and smectic B phases in binary nematic liquid crystal mixtures, a generalized thermodynamic model has been developed in the framework of a combined Flory-Huggins free energy for isotropic mixing, Maier-Saupe free energy for orientational ordering, McMillan free energy for smectic ordering, Chandrasekhar-Clark free energy for hexagonal ordering, and phase field free energy for crystal solidification. Although nematic constituents have no smectic phase, the complexation between these constituent liquid crystal molecules in their mixture resulted in a more stable ordered phase such as smectic A or B phases. Various phase transitions of crystal-smectic, smectic-nematic, and nematic-isotropic phases have been determined by minimizing the above combined free energies with respect to each order parameter of these mesophases. By changing the strengths of anisotropic interaction and hexagonal interaction parameters, the present model captures the induced smectic A or smectic B phases of the binary nematic mixtures. Of particular importance is the fact that the calculated phase diagrams show remarkable agreement with the experimental phase diagrams of binary nematic liquid crystal mixtures involving induced smectic A or induced smectic B phase.

  7. Phase diagram of highly asymmetric binary hard-sphere mixtures.

    Science.gov (United States)

    Dijkstra, M; van Roij, R; Evans, R

    1999-05-01

    We study the phase behavior and structure of highly asymmetric binary hard-sphere mixtures. By first integrating out the degrees of freedom of the small spheres in the partition function we derive a formal expression for the effective Hamiltonian of the large spheres. Then using an explicit pairwise (depletion) potential approximation to this effective Hamiltonian in computer simulations, we determine fluid-solid coexistence for size ratios q=0.033, 0.05, 0.1, 0.2, and 1.0. The resulting two-phase region becomes very broad in packing fractions of the large spheres as q becomes very small. We find a stable, isostructural solid-solid transition for q0 the phase diagram mimics that of the sticky-sphere system. As expected, the radial distribution function g(r) and the structure factor S(k) of the effective one-component system show no sharp signature of the onset of the freezing transition and we find that at most points on the fluid-solid boundary the value of S(k) at its first peak is much lower than the value given by the Hansen-Verlet freezing criterion. Direct simulations of the true binary mixture of hard spheres were performed for q > or =0.05 in order to test the predictions from the effective Hamiltonian. For those packing fractions of the small spheres where direct simulations are possible, we find remarkably good agreement between the phase boundaries calculated from the two approaches-even up to the symmetric limit q=1 and for very high packings of the large spheres, where the solid-solid transition occurs. In both limits one might expect that an approximation which neglects higher-body terms should fail, but our results support the notion that the main features of the phase equilibria of asymmetric binary hard-sphere mixtures are accounted for by the effective pairwise depletion potential description. We also compare our results with those of other theoretical treatments and experiments on colloidal hard-sphere mixtures.

  8. A phase diagram for fluid-driven sediment trasport

    Science.gov (United States)

    Clark, Abe

    When a fluid flows laterally over a granular bed, grains may be transported with the flow. This process shapes much of the natural world. The boundary between states with and without grain motion has been studied for decades. However, this boundary is not well understood, since the process whereby grains are transported involves the coupling of several complex phenomena: turbulent fluid flow near a rough boundary, Darcy flow through the pore structure of the granular bed, the yield strength of granular beds comprised of frictional grains with irregular shape, and inertial effects of grains that become entrained in the flow. In order to clarify the essential physics that governs the onset of granular motion, we study this process computationally by including only the minimal features and then adding complexities one by one. We start with a simple numerical model that includes only gravity, grain-grain interactions that are repulsive and frictionless, and a purely horizontal viscous fluid flow. By varying the fluid flow rate and the effective viscosity, we find behavior that is qualitatively consistent with a large collection of experimental data known as the Shields curve. Thus, our results suggest that the main features of this curve result from a competition between grain inertia and viscous damping. We find this phase diagram to be qualitatively insensitive to secondary effects, such as friction, irregular grain shape, and restitution losses. Funded by U.S. Army Research Office under Grant No. W911NF-14-1-0005.

  9. Global phase diagram of a doped Kitaev-Heisenberg model

    Energy Technology Data Exchange (ETDEWEB)

    Okamoto, Satoshi [ORNL

    2013-01-01

    The global phase diagram of a doped Kitaev-Heisenberg model is studied using an $SU(2)$ slave-boson mean-field method. Near the Kitaev limit, $p$-wave superconducting states which break the time-reversal symmetry are stabilized as reported by You {\\it et al.} [Phys. Rev. B {\\bf 86}, 085145 (2012)] irrespective of the sign of the Kitaev interaction. By further doping, a $d$-wave superconducting state appears when the Kitaev interaction is antiferromagnetic, while another $p$-wave superconducting state appears when the Kitaev interaction is ferromagnetic. This $p$-wave superconducting state does not break the time-reversal symmetry as reported by Hyart {\\it et al.} [Phys. Rev. B {\\bf 85}, 140510 (2012)], and such a superconducting state also appears when the antiferromagnetic Kitaev interaction and the ferromagnetic Heisenberg interaction compete. This work, thus, demonstrates the clear difference between the antiferromagnetic Kitaev model and the ferromagnetic Kitaev model when carriers are doped while these models are equivalent in the undoped limit, and how novel superconducting states emerge when the Kitaev interaction and the Heisenberg interaction compete.

  10. Phase Diagram and Electronic Structure of Praseodymium and Plutonium systems

    Science.gov (United States)

    Yao, Yong-Xin; Nicola, Lanata; Wang, Cai-Zhuang; Kotliar, Gabriel; Ho, Kai-Ming

    2015-03-01

    We apply a new implementation of LDA +Gutzwiller to calculate the zero-temperature phase diagram and electronic structure of Pr and Pu. Our study of Pr indicates that its pressure-induced volume-collapse transition would not occur without change of lattice structure -- contrarily to Ce. Our study of Pu shows that the most important effect originating the differentiation between the equilibrium densities of its allotropes is the competition between the Peierls effect and the Madelung interaction. However, the proper treatment of electron correlation effects is crucial to reach good agreement with experiment. A similar interplay between correlation effects and bands structure is also displayed in Pr, and might emerge in even greater generality. N.L. and G.K. supported by U.S. DOE BES under Grant No. DE-FG02- 99ER45761. Research at Ames Lab supported by the U.S. DOE, Office of BES, DMSE, Ames Laboratory is operated for the U.S. DOE by Iowa State University under Contract No. DE-AC02-07CH11358.

  11. Coformer screening using thermal analysis based on binary phase diagrams.

    Science.gov (United States)

    Yamashita, Hiroyuki; Hirakura, Yutaka; Yuda, Masamichi; Terada, Katsuhide

    2014-08-01

    The advent of cocrystals has demonstrated a growing need for efficient and comprehensive coformer screening in search of better development forms, including salt forms. Here, we investigated a coformer screening system for salts and cocrystals based on binary phase diagrams using thermal analysis and examined the effectiveness of the method. Indomethacin and tenoxicam were used as models of active pharmaceutical ingredients (APIs). Physical mixtures of an API and 42 kinds of coformers were analyzed using Differential Scanning Calorimetry (DSC) and X-ray DSC. We also conducted coformer screening using a conventional slurry method and compared these results with those from the thermal analysis method and previous studies. Compared with the slurry method, the thermal analysis method was a high-performance screening system, particularly for APIs with low solubility and/or propensity to form solvates. However, this method faced hurdles for screening coformers combined with an API in the presence of kinetic hindrance for salt or cocrystal formation during heating or if there is degradation near the metastable eutectic temperature. The thermal analysis and slurry methods are considered complementary to each other for coformer screening. Feasibility of the thermal analysis method in drug discovery practice is ensured given its small scale and high throughput.

  12. Condensation phase diagrams for lipid-coated perfluorobutane microbubbles.

    Science.gov (United States)

    Mountford, Paul A; Sirsi, Shashank R; Borden, Mark A

    2014-06-03

    The goal of this study was to explore the thermodynamic conditions necessary to condense aqueous suspensions of lipid-coated gas-filled microbubbles into metastable liquid-filled nanodrops as well as the physicochemical mechanisms involved with this process. Individual perfluorobutane microbubbles and their lipid shells were observed as they were pressurized at 34.5 kPa s(-1) in a microscopic viewing chamber maintained at temperatures ranging from 5 to 75 °C. The microbubbles contracted under pressure, ultimately leading to either full dissolution or microbubble-to-nanodrop condensation. Temperature-pressure phase diagrams conveying condensation and stability transitions were constructed for microbubbles coated with saturated diacylphosphatidylcholine lipids of varying acyl chain length (C16 to C24). The onset of full dissolution was shifted to higher temperatures with the use of longer acyl chain lipids or supersaturated media. Longer chain lipid shells resisted both dissolution of the gas core and mechanical compression through a pronounced wrinkle-to-fold collapse transition. Interestingly, the lipid shell also provided a mechanical resistance to condensation, shifting the vapor-to-liquid transition to higher pressures than for bulk perfluorobutane. This result indicated that the lipid shell can provide a negative apparent surface tension under compression. Overall, the results of this study will aid in the design and formulation of vaporizable fluorocarbon nanodrops for various applications, such as diagnostic ultrasound imaging, targeted drug delivery, and thermal ablation.

  13. Phase diagram for rotating compact stars with two high density phases

    CERN Document Server

    Blaschke, David B; Poghosyan, G

    2002-01-01

    For the classification of rotating compact stars with two high density phases a phase diagram in the angular velocity (Omega) - baryon number (N) plane is investigated. The dividing line N_crit(Omega) between configurations with one and two phases is correlated to a local maximum of the moment of inertia and can thus be subject to experimental verification by observation of the rotational behavior of accreting compact stars. Another characteristic line, which also can be measured is the transition line to black holes that of the maximum mass configurations. The positions and the shape of these lines are sensitive to changes in the equation of state (EoS) of stellar matter. A comparison of the regional structure of phase diagrams is performed for polytropic and relativistic mean field type EoS and correlations between the topology of the transition lines and the properties of two-phase EoS are obtained. Different scenarios of compact star evolution are discussed as trajectories in the phase diagram. It is show...

  14. One-Component Pressure-Temperature Phase Diagrams in the Presence of Air

    Science.gov (United States)

    Andrade-Gamboa, Julio; Martire, Daniel O.; Donati, Edgardo R.

    2010-01-01

    One-component phase diagrams are good approximations to predict pressure-temperature ("P-T") behavior of a substance in the presence of air, provided air pressure is not much higher than the vapor pressure. However, at any air pressure, and from the conceptual point of view, the use of a traditional "P-T" phase diagram is not strictly correct. In…

  15. Strong bioresorbable Ca phosphate-PLA nanocomposites with uniform phase distribution by attrition milling and high pressure consolidation.

    Science.gov (United States)

    Rakovsky, Artoum; Gotman, Irena; Rabkin, Eugen; Gutmanas, Elazar Y

    2013-02-01

    Highly dense bioresorbable Ca-deficient HA-PLA (CDHA-PLA) and β-TCP-PLA nanocomposite materials with high (up to 80 vol%) contents of the calcium phosphate (CaP) phase and homogeneous phase distribution were prepared via attrition milling followed by high pressure consolidation at ambient temperature. The microstructure and mechanical properties of the materials obtained were studied as a function of milling time and PLA amount. Attrition milling resulted in disintegration of β-TCP powder agglomerates down to 50-150 nm, disintegration of CDHA agglomerates and refinement of 15 × 150 nm(2) CDHA nanoparticles to a size of 8 × 20 nm(2), and in a uniform distribution of the polymer component. Very high compressive strengths up to 400 MPa and high bending strengths up to 70 MPa were obtained. For both β-TCP and CDHA-based nanocomposites, the strength characteristics increased with milling time and decreased with increasing PLA content. For CDHA-based nanocomposites, attrition milling resulted in decrease of ductility while for β-TCP-40 vol% PLA the ductility increased. The observed behavior may be a result of formation of homogeneous, relatively thick (tens of nanometers), ductile PLA layers in β-TCP-PLA nanocomposites, but very thin (several nanometers) PLA layers in attrition milled CDHA-PLA nanocomposites. Degradation of compressive and bending strength in aqueous solutions was observed for all the studied CaP-PLA nanocomposites.

  16. Experimental determination of the peritectic transition temperature of MgB{sub 2} in the Mg–B phase diagram

    Energy Technology Data Exchange (ETDEWEB)

    Bohnenstiehl, S.D. [Department of Materials Science and Engineering, The Ohio State University, 143 Fontana Laboratories, 116 West 19th Avenue, Columbus, OH 43210 (United States); Susner, M.A., E-mail: susner.1@osu.edu [Department of Materials Science and Engineering, The Ohio State University, 143 Fontana Laboratories, 116 West 19th Avenue, Columbus, OH 43210 (United States); Dregia, S.A.; Sumption, M.D. [Department of Materials Science and Engineering, The Ohio State University, 143 Fontana Laboratories, 116 West 19th Avenue, Columbus, OH 43210 (United States); Donovan, J. [Center for Advanced Materials Characterization in Oregon, University of Oregon, 1443 East 13th Avenue, Eugene, OR 97403 (United States); Collings, E.W. [Department of Materials Science and Engineering, The Ohio State University, 143 Fontana Laboratories, 116 West 19th Avenue, Columbus, OH 43210 (United States)

    2014-01-20

    Highlights: • We have created a high pressure, high temperature material synthesis apparatus. • This apparatus is programmable and capable of various thermal analysis procedures. • Using our apparatus we have established the peritectic transition temperature of MgB{sub 2}. • This temperature is 300 °C lower than established values for the same pressure. • We have shown that this discrepancy is likely the result of impurities such as C. - Abstract: We have studied thermodynamic phase stability in the Mg–B system through use of a high-pressure, high-temperature apparatus consisting of a large pressure vessel and an RF induction heater. The incongruent melting temperature for MgB{sub 2} was found to be ∼1450 °C at 10 MPa using thermal analysis data applied to both MgB{sub 2} powder samples and Mg/B mixtures. The experimental temperature is ∼300 °C lower than temperatures shown in calculated phase diagrams of the Mg–B system at the same pressure and the discrepancy demonstrates the need for further experimental investigations of phase stability in binary Mg–B and ternary Mg–B–X systems. In this study C (as an impurity in boron) was found to have a large effect on the peritectic temperature, with a relatively small (0.7 wt% C) impurity concentration resulting in a ∼40 °C elevation of the peritectic temperature. Along with morphological characterization, XRD and EPMA analyses were used to identify phases and confirm the peritectic transformation in the Mg–B phase diagram.

  17. Constructing multicomponent phase diagrams by overlapping ZPF lines. [Zero Phase Fraction Line for improved mechanical and corrosion properties

    Science.gov (United States)

    Gupta, H.; Morral, J. E.; Nowotny, H.

    1986-01-01

    A procedure is introduced which can be used to draw isothermal sections from a multicomponent phase diagram in a matter of minutes, regardless of the diagram complexity. In the proposed method, the zero phase fraction (ZPF) lines are drawn separately for all phases existing in the system; by overlapping these ZPF lines, the desired section is obtained. Two examples - with five components and eight components - are given to illustrate the method. Regarding the second example, it is noted that although the final diagram may be altered to create discontinuities in slope at intersection points, the diagram remains unchanged from a topological standpoint. Thus, the overlapping ZPF lines supply all the information needed to construct complex diagrams. Even if many more phases and components are involved, the final diagram can be drawn with equal facility.

  18. Collins Model and Phase Diagram of 2D Ternary System

    Institute of Scientific and Technical Information of China (English)

    XIE Chuan-Mei; CHEN Li-Rong

    2004-01-01

    The Collins model is introduced into the two-dimensional (2D) alternative ternary system having the Lennard-Jones (L-J) potential. The Gibbs free energy of this ternary system is calculated, and according to thermodynamic theory, a group of equations that determine the solid-liquid diagram of ternary system are derived, some isothermal sectional diagrams of the 2D ternary system are obtained. The results are quite similar to the behavior of three-dimensional substances.

  19. Determination of β-Carotene in Supplements and Raw Materials by Reversed-Phase High Pressure Liquid Chromatography

    Science.gov (United States)

    Szpylka, John; DeVries, Jonathan W.; Bhandari, S.; Bui, M.H.; Ji, D.; Konings, E.; Lewis, R.; Maas, P.; Parish, H.; Post, B.; Schierle, J.; Sullivan, D.; Taylor, A.; Wang, J.; Ware, G.; Woollard, D.; Wu, T.

    2008-01-01

    Twelve laboratories representing 4 countries participated in an interlaboratory study conducted to determine all-trans-β-carotene and total β-carotene in dietary supplements and raw materials. Thirteen samples were sent as blind duplicates to the collaborators. Results obtained from 11 laboratories are reported. For products composed as softgels and tablets that were analyzed for total β-carotene, the reproducibility relative standard deviation (RSDR) ranged from 3.35 to 23.09% and the HorRat values ranged from 1.06 to 3.72. For these products analyzed for trans β-carotene, the reproducibility relative standard deviation (RSDR) ranged from 4.28 to 22.76% and the HorRat values ranged from 0.92 to 3.37. The RSDr and HorRat values in the analysis of a beadlet raw material were substantial and it is believed that the variability within the material itself introduced significant variation in subsampling. The method uses high pressure liquid chromatography (LC) in the reversed-phase mode with visible light absorbance for detection and quantitation. If high levels of α-carotenes are present, a second LC system is used for additional separation and quantitation of the carotene species. It is recommended that the method be adopted as an AOAC Official Method. PMID:16385976

  20. Crystal structure of SrGeO3 in the high-pressure perovskite-type phase

    Directory of Open Access Journals (Sweden)

    Akihiko Nakatsuka

    2015-05-01

    Full Text Available Single crystals of the SrGeO3 (strontium germanium trioxide high-pressure phase have been synthesized successfully at 6 GPa and 1223 K. The compound crystallizes with the ideal cubic perovskite-type structure (space group Pm-3m, which consists of a network of corner-linked regular GeO6 octahedra (point-group symmetry m-3m, with the larger Sr atoms located at the centers of cavities in the form of SrO12 cuboctahedra (point-group symmetry m-3m in the network. The degrees of covalencies included in the Sr—O and the Ge—O bonds calculated from bond valences are 20.4 and 48.9%, respectively. Thus, the Ge—O bond of the GeO6 octahedron in the SrGeO3 perovskite has a strong covalency, comparable to those of the Si—O bonds of the SiO4 tetrahedra in silicates with about 50% covalency. The thermal vibrations of the O atoms in the title compound are remarkably suppressed in the directions of the Ge—O bonds. This anisotropy ranks among the largest observed in stoichiometric cubic perovskites.

  1. High pressure homogenization and two-phased anaerobic digestion for enhanced biogas conversion from municipal waste sludge.

    Science.gov (United States)

    Wahidunnabi, Abdullahil K; Eskicioglu, Cigdem

    2014-12-01

    This study compared advanced anaerobic digestion combining two-phased anaerobic digestion (2PAD) with high pressure homogenization (HPH) pretreatment to conventional anaerobic digestion of municipal sludge at laboratory scale. The study began with examination of thickened waste activated sludge (TWAS) solubilization due to HPH pretreatment at different pressure (0-12,000 psi) and chemical dose (0.009-0.036 g NaOH/g total solids). Homogenizing pressure was found as the most significant factor (p-value production (0.61-1.32 L CH4/Ldigester-d) and VS removals (43-64%). Thermophilic control, 2PAD and HPH + 2PAD systems resulted in significant pathogen removals meeting Class A biosolids requirements according to Organic Matter Recycling Regulations (OMRR) of British Columbia (BC) at 20 d SRT. Energy analysis indicated that all the digestion scenarios attained positive energy balance with 2PAD system operated at 20 d SRT producing the maximum net energy of 4.76 GJ/tonne CODadded.

  2. Closed-loop phase diagrams, vaporization, and multicriticality in binary liquid mixtures

    Science.gov (United States)

    Caflisch, Robert G.; Walker, James S.

    1983-09-01

    The coupled Potts-Ising models of Walker and Vause, which successfully describe closed-loop phase diagrams in hydrogen-bonding mixtures, are generalized to encompass the vapor phase, and are studied using position-space renormalization-group techniques. Global phase diagrams are generated, exhibiting such features as miscibility-immiscibility criticality, liquid-vapor critical points, critical end points, and bicritical and tricritical points. In addition, new types of phase diagrams are found, involving upper and lower azeotropes, for example, which are expected to be physically realizable in experimental systems.

  3. Phase Diagram of the Gross-Neveu Model: Exact Results and Condensed Matter Precursors

    CERN Document Server

    Schnetz, O; Urlichs, K; Schnetz, Oliver; Thies, Michael; Urlichs, Konrad

    2004-01-01

    Recently the revised phase diagram of the (large N) Gross-Neveu model in 1+1 dimensions with discrete chiral symmetry has been determined numerically. It features three phases, a massless and a massive Fermi gas and a kink-antikink crystal. Here we investigate the phase diagram by analytical means, mapping the Dirac-Hartree-Fock equation onto the non-relativistic Schroedinger equation with the (single gap) Lame potential. It is pointed out that mathematically identical phase diagrams appeared in the condensed matter literature some time ago in the context of the Peierls-Froehlich model and ferromagnetic superconductors.

  4. Phase diagrams properties of the mixed traffic flow on a crossroad

    Science.gov (United States)

    Li, Qi-Lang; Wang, Bing-Hong; Liu, Mu-Ren

    2010-11-01

    Based on the Ishibashi and Fukui crossroad traffic flow model [Y. Ishibashi and M. Fukui. J. Phys. Soc. Japan. 70 (2001) 2793], mixed traffic flow (i.e., the fast and slow vehicles with different maximum velocities are mixed) is investigated in this work. According to the numerical simulation results and the principle for constructing the phase diagram, phase diagrams for mixed traffic flow are constructed. It is noted that the topology of these phase diagrams is similar to that of phase diagrams for homogeneous vehicles (which refers to slow vehicles only). From the phase diagrams, it is evident that mixed traffic flow is influenced by the mixing rate f (fraction of slow and fast vehicles) in regions II and V, but not in other regions. Although a mixture of fast and slow vehicles is introduced in the crossroad traffic flow model, the separation between phases in the phase diagrams remains linear. For a given q (the vehicle density on the northbound road), one flow plateau appears in regions IIx or IVy, while two maximum flow plateaus appear in region V in each of the phase diagrams. The maximum flow values in region V reflect the maximum traffic capacity for the traffic system as defined in this work. Since mixed traffic flow is a common phenomenon in real traffic, this work may offer help in real traffic simulations and traffic management.

  5. CaAl 12Si 4O 27, a New High-Pressure Phase Containing Al 6O 19 Clusters

    Science.gov (United States)

    Grey, I. E.; Madsen, I. C.; Hibberson, W. O.; O'Neill, H. St. C.

    2000-09-01

    CaAl12Si4O27, a new high-pressure phase in the CaO-Al2O3-SiO2 system, was prepared at 1550°C and 14 GPa. It has trigonal symmetry, P-3, with a=7.223(1) and c=8.614(3) Å. Its structure was solved using crystal chemistry principles and refined using the Rietveld method applied to powder X-ray diffraction data, Rwp=6.1%, RB=2.7%. The structure is a new type based on a close-packed anion lattice with a mixed layer stacking sequence ABACA≡(hc)2 and with Ca atoms ordered in one-seventh of the anion sites in alternate c-stacked layers. The Si atoms are ordered in both octahedral and tetrahedral sites while the Al atoms are ordered in two independent octahedral sites. Octahedral edge-shared clusters, Al6O19, occur in the structure, interconnected within the close-packed layers by corner-linking to SiO4 tetrahedra. The clusters are also connected by corner-sharing to nine-member rings of edge-shared Al- and Si-centered octahedra in adjacent layers. The new phase has structural features in common with the barium titanium ferrite of similar composition, BaFe11Ti3O23, as well as with the mineral simpsonite, Al4Ta3O13(OH), and alkali metal niobates which contain Nb6O19 clusters.

  6. High-pressure structural configuration and phase transition in celsian, BaAl2Si2O8

    Science.gov (United States)

    Curetti, Nadia; Benna, Piera; Bruno, Emiliano

    2016-10-01

    In situ high-pressure X-ray diffraction study was performed on celsian (Cls97Or3) from Jakobsberg, Sweden. A single crystal of celsian was loaded in an ETH-type diamond anvil cell, and unit-cell parameters were measured at 20 different pressures up to 6.0 GPa at room T. The evolution of the unit-cell parameters and volume as a function of pressure shows a discontinuity at P ~ 5.7 GPa indicating a displacive first-order phase transition. The P-V data were fitted by a second-order Birch-Murnaghan EoS only up to 2.55 GPa, because at higher pressures a slight change in the compressional behavior of the unit-cell volume is observed, indicating a pre-transition volume softening. The resulting EoS coefficients are V 0 = 1461.4(1) Å3 and K T0 = 88.1(6) GPa. A second crystal of celsian was loaded in the DAC cell, and single-crystal in situ HP X-ray diffraction was performed at P = 0.0001, 2.1, 4.2, 5.5, 5.9, 6.5 and 7.8 GPa. The data collections between 0 and 5.5 GPa show only a- and b-type reflections confirming the I2/c space group. The appearance of c and d-type reflections at 5.9, 6.5 and 7.8 GPa, the analysis of the systematic absence and the structural refinements define the HP phase transition as an I2/c-P21/c transition. The most significant changes with compression in celsian are the deformation in the Ba polyhedra and the variation in the T-O-T angles.

  7. Effects of gasket on coupled plastic flow and strain-induced phase transformations under high pressure and large torsion in a rotational diamond anvil cell

    Science.gov (United States)

    Feng, Biao; Levitas, Valery I.

    2016-01-01

    Combined plastic flow and strain-induced phase transformations (PTs) under high pressure in a sample within a gasket subjected to three dimensional compression and torsion in a rotational diamond anvil cell (RDAC) are studied using a finite element approach. The results are obtained for the weaker, equal-strength, and stronger high-pressure phases in comparison with low-pressure phases. It is found that, due to the strong gasket, the pressure in the sample is relatively homogenous and the geometry of the transformed zones is mostly determined by heterogeneity in plastic flow. For the equal-strength phases, the PT rate is higher than for the weaker and stronger high-pressure phases. For the weaker high-pressure phase, transformation softening induces material instability and leads to strain and PT localization. For the stronger high-pressure phase, the PT is suppressed by strain hardening during PT. The effect of the kinetic parameter k that scales the PT rate in the strain-controlled kinetic equation is also examined. In comparison with a traditional diamond anvil cell without torsion, the PT progress is much faster in RDAC under the same maximum pressure in the sample. Finally, the gasket size and strength effects are discussed. For a shorter and weaker gasket, faster plastic flow in radial and thickness directions leads to faster PT kinetics in comparison with a longer and stronger gasket. The rates of PT and plastic flows are not very sensitive to the modest change in a gasket thickness. Multiple experimental results are reproduced and interpreted. Obtained results allow one to design the desired pressure-plastic strain loading program in the experiments for searching new phases, reducing PT pressure by plastic shear, extracting kinetic properties from experiments with heterogeneous fields, and controlling homogeneity of all fields and kinetics of PTs.

  8. Phase equilibrium data and thermodynamic modeling of the system (CO{sub 2} + biodiesel + methanol) at high pressures

    Energy Technology Data Exchange (ETDEWEB)

    Pinto, Leandro F.; Segalen da Silva, Diogo Italo [Department of Chemical Engineering, Federal University of Parana, CEP 81531-990, Curitiba, PR (Brazil); Rosa da Silva, Fabiano; Ramos, Luiz P. [Department of Chemistry, Federal University of Parana, CEP 81531-990, Curitiba, PR (Brazil); Ndiaye, Papa M. [Department of Chemical Engineering, Federal University of Parana, CEP 81531-990, Curitiba, PR (Brazil); Corazza, Marcos L., E-mail: corazza@ufpr.br [Department of Chemical Engineering, Federal University of Parana, CEP 81531-990, Curitiba, PR (Brazil)

    2012-01-15

    Highlights: > We measured phase behavior for the system involving {l_brace}CO{sub 2} + biodiesel + methanol{r_brace}. > The saturation pressures were obtained using a variable-volume view cell. > The experimental data were modeled using PR-vdW2 and PR-WS equations of state. - Abstract: The main objective of this work was to investigate the high pressure phase behavior of the binary systems {l_brace}CO{sub 2}(1) + methanol(2){r_brace} and {l_brace}CO{sub 2}(1) + soybean methyl esters (biodiesel)(2){r_brace} and the ternary system {l_brace}CO{sub 2}(1) + biodiesel(2) + methanol(3){r_brace} were determined. Biodiesel was produced from soybean oil, purified, characterized and used in this work. The static synthetic method, using a variable-volume view cell, was employed to obtain the experimental data in the temperature range of (303.15 to 343.15) K and pressures up to 21 MPa. The mole fractions of carbon dioxide were varied according to the systems as follows: (0.2383 to 0.8666) for the binary system {l_brace}CO{sub 2}(1) + methanol(2){r_brace}; (0.4201 to 0.9931) for the binary system {l_brace}CO{sub 2}(1) + biodiesel(2){r_brace}; (0.4864 to 0.9767) for the ternary system {l_brace}CO{sub 2}(1) + biodiesel(2) + methanol(3){r_brace} with a biodiesel to methanol molar ratio of (1:3); and (0.3732 to 0.9630) for the system {l_brace}CO{sub 2} + biodiesel + methanol{r_brace} with a biodiesel to methanol molar ratio of (8:1). For these systems, (vapor + liquid), (liquid + liquid), (vapor + liquid + liquid) transitions were observed. The phase equilibrium data obtained for the systems were modeled using the Peng-Robinson equation of state with the classical van der Waals (PR-vdW2) and Wong-Sandler (PR-WS) mixing rules. Both thermodynamic models were able to satisfactorily correlate the phase behavior of the systems investigated and the PR-WS presented the best performance.

  9. Polyakov-Nambu-Jona-Lasinio phase diagrams and quarkyonic phase from order parameters

    CERN Document Server

    Dutra, M; Delfino, A; Frederico, T; Malheiro, M

    2013-01-01

    We show that the magnitude of the order parameters in Polyakov-Nambu-Jona-Lasinio (PNJL) model, given by the quark condensate and the Polyakov loop, can be used as a criterium to clearly identify, without ambiguities, phases and boundaries of the strongly interacting matter, namely, the broken/restored chiral symmetry, and confinement/deconfinement regions. This structure is represented by the projection of the order parameters in the temperature-chemical potential plane, which allows a clear identification of pattern changes in the phase diagram. Such a criterium also enables the emergence of a quarkyonic phase even in the two-flavor system. We still show that this new phase diminishes due to the influence of an additional vector-type interaction in the PNJL phase diagrams, and is quite sensitive to the effect of the change of the $T_0$ parameter in the Polyakov potential. Finally, we show that the phases and boundaries constructed by our method indicate that the order parameters should be more strongly corr...

  10. Gas Hydrate Stability and Sampling: The Future as Related to the Phase Diagram

    Directory of Open Access Journals (Sweden)

    E. Dendy Sloan

    2010-12-01

    Full Text Available The phase diagram for methane + water is explained, in relation to hydrate applications, such as in flow assurance and in nature. For natural applications, the phase diagram determines the regions for hydrate formation for two- and three-phase conditions. Impacts are presented for sample preparation and recovery. We discuss an international study for “Round Robin” hydrate sample preparation protocols and testing.

  11. Final Report. IUT No. B560420 with UC Berkeley. Organic Chemistry at High Pressures &Temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Montgomery, W; Crowhurst, J C; Zaug, J M; Jeanloz, R

    2007-03-20

    We have successfully completed the research outlined in our proposal: Organic Chemistry at High Pressures and Temperatures. We have experimentally determined a phase diagram which documents the phases and reaction regimes of cyanuric acid , H{sub 3}C{sub 3}N{sub 3}O{sub 3} (1,3,5-triazine-2,4,6-trione), from 300 - 750 K and 0 - 8.1 GPa. We utilized a comparatively new technique to study thin samples of cyanuric acid in the diamond anvil cell in order to collect ambient temperature, high pressure FTIR and Raman data as well as the high-pressure, high-temperature data used in the phase diagram. These experiments made use of the CMLS High-pressure lab's diamond anvil facilities as well as the FTIR and Raman systems.

  12. C.A.D. representation of ternary and quaternary phase diagrams

    Science.gov (United States)

    Delao, James D.

    1986-01-01

    This work is concerned with the utilization of C.A.D. solid-modeling software for the computer representation of three-dimensional phase diagrams. The work was undertaken in two parts. First, the C.A.D. software (I-DEAS, by Structural Dynamics Research Corp.) was integrated with a variety of auxiliary Fortran 77 and I-DEAS language programs which were written specifically for the purpose of phase diagram representation. The capabilities of the resulting suite of software for three-dimensional phase diagram representation were developed and illustrated by the construction, display and manipulation of solid-model phase diagrams for a hypothetical quaternary eutectic system. The results of this work are discussed in some detail in the attached publication ('Solid-modeling: a C.A.D. Alternative for Three-dimensional Phase Diagram Representation'). Such a technique is of general applicability, having utility in both research and education. Secondly, using the C.A.D. technique, data from the literature (gleaned from some 70 separate publications), which represent experimentally determined phase boundaries, were combined to form solid-model representations of the CMS2-M2S-S ternary space diagram and the CMS2-CAS2-M2S-S quaternary liquidus projection (where C=CaO, M=MgO, A=Al2O3, and S=SiO2). These diagrams were utilized in a concurrent study of solidification in the CMAS system.

  13. Analytical phase diagrams for colloids and non-adsorbing polymer.

    Science.gov (United States)

    Fleer, Gerard J; Tuinier, Remco

    2008-11-04

    introduce the size ratio q=delta/a, where the depletion thickness delta is no longer of order R. In the protein limit the binodal concentrations are above overlap. In such semidilute solutions delta approximately xi, where the De Gennes blob size (correlation length) xi scales as xi approximately phi(-gamma), with gamma=0.77 for good solvents and gamma=1 for a theta solvent. In this limit Pi=Pi(sd) approximately phi(3gamma). We now apply the following additional modifications: With these latter two modifications we obtain again a fully analytical model with simple equations for critical and triple points as a function of q(R). In the protein limit the binodal polymer concentrations scale as q(R)(1/gamma), and phase diagrams phiq(R)(-1/gamma) versus the colloid concentration eta become universal (i.e., independent of the size ratio q(R)). The predictions of this generalized free-volume theory (GFVT) are in excellent agreement with experiment and with computer simulations, not only for the colloid limit but also for the protein limit (and the crossover between these limits). The q(R)(1/gamma) scaling is accurately reproduced by both simulations and other theoretical models. The liquid window is the region between phi(c) (critical point) and phi(t) (triple point). In terms of the ratio phi(t)/phi(c) the liquid window extends from 1 in the cep (here phi(t)-phi(c)=0) to 2.2 in the protein limit. Hence, the liquid window is narrow: it covers at most a factor 2.2 in (external) polymer concentration.

  14. Pressure and temperature phase diagram of Gd{sub 2}Ti{sub 2}O{sub 7} under irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Catillon, G. [Université Paris-Est, G2I, EA4119, 5 Blvd. Descartes, F-77454 Marne la Vallée Cedex 2 (France); Chartier, A., E-mail: alain.chartier@cea.fr [CEA, DEN, DMN, SCCME, F-91191 Gif-Sur-Yvette Cedex (France)

    2014-11-21

    The pressure and temperature phase diagram of Gd{sub 2}Ti{sub 2}O{sub 7} under irradiation are calculated by means of molecular dynamics calculations. The critical temperature for amorphization obeys a linear law with pressure. Gd{sub 2}Ti{sub 2}O{sub 7} under irradiation transits towards the fluorite above this temperature and amorphizes below. The configuration of the Ti interstitial reveals to be the key of the amorphizability of Gd{sub 2}Ti{sub 2}O{sub 7}. Its stability depends upon disorder and pressure. Low pressure promotes the stabilization of Ti linked-polyhedra that drive the system to the amorphous state under irradiation. Conversely, high pressure activates its destabilization to interstitials that recombine with vacancies, driving the system to the fluorite structure under irradiation.

  15. A composite phase diagram of structure H hydrates using Schreinemakers' geometric approach

    Science.gov (United States)

    Mehta, A.P.; Makogon, T.Y.; Burruss, R.C.; Wendlandt, R.F.; Sloan, E.D.

    1996-01-01

    A composite phase diagram is presented for Structure H (sH) clathrate hydrates. In this work, we derived the reactions occurring among the various phases along each four-phase (Ice/Liquid water, liquid hydrocarbon, vapor, and hydrate) equilibrium line. A powerful method (though seldom used in chemical engineering) for multicomponent equilibria developed by Schreinemakers is applied to determine the relative location of all quadruple (four-phase) lines emanating from three quintuple (five-phase) points. Experimental evidence validating the approximate phase diagram is also provided. The use of Schreinemakers' rules for the development of the phase diagram is novel for hydrates, but these rules may be extended to resolve the phase space of other more complex systems commonly encountered in chemical engineering.

  16. The non-equilibrium phase diagrams of flow-induced crystallization and melting of polyethylene.

    Science.gov (United States)

    Wang, Zhen; Ju, Jianzhu; Yang, Junsheng; Ma, Zhe; Liu, Dong; Cui, Kunpeng; Yang, Haoran; Chang, Jiarui; Huang, Ningdong; Li, Liangbin

    2016-09-09

    Combining extensional rheology with in-situ synchrotron ultrafast x-ray scattering, we studied flow-induced phase behaviors of polyethylene (PE) in a wide temperature range up to 240 °C. Non-equilibrium phase diagrams of crystallization and melting under flow conditions are constructed in stress-temperature space, composing of melt, non-crystalline δ, hexagonal and orthorhombic phases. The non-crystalline δ phase is demonstrated to be either a metastable transient pre-order for crystallization or a thermodynamically stable phase. Based on the non-equilibrium phase diagrams, nearly all observations in flow-induced crystallization (FIC) of PE can be well understood. The interplay of thermodynamic stabilities and kinetic competitions of the four phases creates rich kinetic pathways for FIC and diverse final structures. The non-equilibrium flow phase diagrams provide a detailed roadmap for precisely processing of PE with designed structures and properties.

  17. Binary Solid-Liquid Phase Diagram of Phenol and t-Butanol: An Undergraduate Physical Chemistry Experiment

    Science.gov (United States)

    Xu, Xinhua; Wang, Xiaogang; Wu, Meifen

    2014-01-01

    The determination of the solid-liquid phase diagram of a binary system is always used as an experiment in the undergraduate physical chemistry laboratory courses. However, most phase diagrams investigated in the lab are simple eutectic ones, despite the fact that complex binary solid-liquid phase diagrams are more common. In this article, the…

  18. Binary Solid-Liquid Phase Diagram of Phenol and t-Butanol: An Undergraduate Physical Chemistry Experiment

    Science.gov (United States)

    Xu, Xinhua; Wang, Xiaogang; Wu, Meifen

    2014-01-01

    The determination of the solid-liquid phase diagram of a binary system is always used as an experiment in the undergraduate physical chemistry laboratory courses. However, most phase diagrams investigated in the lab are simple eutectic ones, despite the fact that complex binary solid-liquid phase diagrams are more common. In this article, the…

  19. Dynamic phase transitions and dynamic phase diagrams of the Ising model on the Shastry-Sutherland lattice

    Energy Technology Data Exchange (ETDEWEB)

    Deviren, Şeyma Akkaya, E-mail: sadeviren@nevsehir.edu.tr [Department of Science Education, Education Faculty, Nevsehir Hacı Bektaş Veli University, 50300 Nevşehir (Turkey); Deviren, Bayram [Department of Physics, Nevsehir Hacı Bektaş Veli University, 50300 Nevsehir (Turkey)

    2016-03-15

    The dynamic phase transitions and dynamic phase diagrams are studied, within a mean-field approach, in the kinetic Ising model on the Shastry-Sutherland lattice under the presence of a time varying (sinusoidal) magnetic field by using the Glauber-type stochastic dynamics. The time-dependence behavior of order parameters and the behavior of average order parameters in a period, which is also called the dynamic order parameters, as a function of temperature, are investigated. Temperature dependence of the dynamic magnetizations, hysteresis loop areas and correlations are investigated in order to characterize the nature (first- or second-order) of the dynamic phase transitions as well as to obtain the dynamic phase transition temperatures. We present the dynamic phase diagrams in the magnetic field amplitude and temperature plane. The phase diagrams exhibit a dynamic tricritical point and reentrant phenomena. The phase diagrams also contain paramagnetic (P), Néel (N), Collinear (C) phases, two coexistence or mixed regions, (N+C) and (N+P), which strongly depend on interaction parameters. - Highlights: • Dynamic magnetization properties of spin-1/2 Ising model on SSL are investigated. • Dynamic magnetization, hysteresis loop area, and correlation have been calculated. • The dynamic phase diagrams are constructed in (T/|J|, h/|J|) plane. • The phase diagrams exhibit a dynamic tricritical point and reentrant phenomena.

  20. High Pressure Biomass Gasification

    Energy Technology Data Exchange (ETDEWEB)

    Agrawal, Pradeep K [Georgia Tech Research Corporation, Atlanta, GA (United States)

    2016-07-29

    According to the Billion Ton Report, the U.S. has a large supply of biomass available that can supplement fossil fuels for producing chemicals and transportation fuels. Agricultural waste, forest residue, and energy crops offer potential benefits: renewable feedstock, zero to low CO2 emissions depending on the specific source, and domestic supply availability. Biomass can be converted into chemicals and fuels using one of several approaches: (i) biological platform converts corn into ethanol by using depolymerization of cellulose to form sugars followed by fermentation, (ii) low-temperature pyrolysis to obtain bio-oils which must be treated to reduce oxygen content via HDO hydrodeoxygenation), and (iii) high temperature pyrolysis to produce syngas (CO + H2). This last approach consists of producing syngas using the thermal platform which can be used to produce a variety of chemicals and fuels. The goal of this project was to develop an improved understanding of the gasification of biomass at high pressure conditions and how various gasification parameters might affect the gasification behavior. Since most downstream applications of synags conversion (e.g., alcohol synthesis, Fischer-Tropsch synthesis etc) involve utilizing high pressure catalytic processes, there is an interest in carrying out the biomass gasification at high pressure which can potentially reduce the gasifier size and subsequent downstream cleaning processes. It is traditionally accepted that high pressure should increase the gasification rates (kinetic effect). There is also precedence from coal gasification literature from the 1970s that high pressure gasification would be a beneficial route to consider. Traditional approach of using thermogravimetric analyzer (TGA) or high-pressure themogravimetric analyzer (PTGA) worked well in understanding the gasification kinetics of coal gasification which was useful in designing high pressure coal gasification processes. However

  1. Odd q-state clock spin-glass models in three dimensions, asymmetric phase diagrams, and multiple algebraically ordered phases.

    Science.gov (United States)

    Ilker, Efe; Berker, A Nihat

    2014-12-01

    Distinctive orderings and phase diagram structures are found, from renormalization-group theory, for odd q-state clock spin-glass models in d=3 dimensions. These models exhibit asymmetric phase diagrams, as is also the case for quantum Heisenberg spin-glass models. No finite-temperature spin-glass phase occurs. For all odd q≥5, algebraically ordered antiferromagnetic phases occur. One such phase is dominant and occurs for all q≥5. Other such phases occupy small low-temperature portions of the phase diagrams and occur for 5≤q≤15. All algebraically ordered phases have the same structure, determined by an attractive finite-temperature sink fixed point where a dominant and a subdominant pair states have the only nonzero Boltzmann weights. The phase transition critical exponents quickly saturate to the high q value.

  2. Standard values of fugacity for sulfur which are self-consistent with the low-pressure phase diagram

    Energy Technology Data Exchange (ETDEWEB)

    Marriott, Robert A., E-mail: rob.marriott@ucalgary.ca [Alberta Sulphur Research Ltd., University of Calgary, Alberta (Canada); Wan, Herman H. [Alberta Sulphur Research Ltd., University of Calgary, Alberta (Canada)

    2011-08-15

    Highlights: > We have provided a method for calculating the fugacity for elemental sulfur. > Calculated sulfur fugacities can be used in sulfur equilibrium models. > The sulfur fugacities also can be used to locate the phase changes in the low-pressure phase diagram. > We have measured the 'natural' melting point of sulfur, and found it to be T = 388.5 {+-} 0.2 K. - Abstract: A method for calculating the fugacity of pure sulfur in the {alpha}-solid, {beta}-solid and liquid phase regions has been reported for application to industrial equilibrium conditions, e.g., high-pressure solubility of sulfur in sour gas. The fugacity calculations are self-consistent with the low-pressure phase diagram. As recently discussed by Ferreira and Lobo , empirical fitting of the experimental data does not yield consistent behaviour for the low-pressure phase diagram of elemental sulfur. In particular, there is a discrepancy between the vapour pressure of {beta}-solid (monoclinic) and liquid sulfur at the fusion temperature. We have provided an alternative semi-empirical approach which allows one to calculate values of the fugacity at conditions removed from the conditions of the pure sulfur phase transitions. For our approach, we have forced the liquid vapour pressure to equal the {beta}-solid vapour pressure at the {beta}-l-g triple point corresponding to the 'natural' fusion temperature for {beta}-solid. Many studies show a higher 'observed' fusion temperature for elemental sulfur. The non-reversible conditions for 'observed' fusion conditions for elemental sulfur result from a kinetically hindered melt which causes some thermodynamic measurements to be related to a metastable S{sub 8} liquid. We have measured the 'natural' fusion temperature, T{sub fus}{sup {beta}}(exp.)=(388.5{+-}0.2)K at p = 89.9 kPa, which is consistent with literature fusion data at higher-pressures. Using our semi-empirical approach, we have used or found the

  3. 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...... agreement with the experimental diagram is good. The influence of different free energy contributions (configurational, magnetic, and vibrational) on the phase transition in Ce is discussed....

  4. Phase Diagrams and Tricritical Behaviour of the Spin-2 Ising Model in a Longitudinal Random Field

    Institute of Scientific and Technical Information of China (English)

    LIANG Ya-Qiu; WEI Guo-Zhu; ZHANG Qi; SONG Guo-Li

    2004-01-01

    @@ Within the framework of the effective-field theory with correlations, we study the ferromagnetic spin-2 randomfield Ising model (RFIM) in the presence of a crystal field on honeycomb (z = 3), square (z = 4) and simple cubic (z = 6) lattices. The effects of the crystal field and the longitudinal random field on the phase diagrams are investigated. Some characteristic features of the phase diagrams, such as the tricritical phenomena, reentrant phenomena and existence of two tricritical points, are found.

  5. PHASE DIAGRAM OF GELATINE-POLYURONATE COLLOIDS: ITS APPLICATION FOR MICROENCAPSULATION AND NOT ONLY

    Directory of Open Access Journals (Sweden)

    Alexei Baerle

    2016-06-01

    Full Text Available Phase state and the charge of colloidal particles in the gelatine-polyuronate system were studied. A method for comparative evaluation of molecular weight of colloids by means of viscosimetric measurements and electrophoresis was developed. It is shown that the Diagram {Phase state = f (composition, pH} contains six well-defined regions. The diagram explains and predicts the behaviour of protein-polysaccharide colloids, which are included in beverages or forms the shells of oil-containing microcapsules.

  6. Reinvestigation of superconducting phase diagram of UGe{sub 2} by AC magnetic susceptibility experiment

    Energy Technology Data Exchange (ETDEWEB)

    Ban, S. [Deptartment of Physics, University of Nagoya, Nagoya, 464-8602 (Japan)]. E-mail: f060214d@mbox.nagoya-u.ac.jp; Deguchi, K. [Deptartment of Physics, University of Nagoya, Nagoya, 464-8602 (Japan); Aso, N. [Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581 (Japan); Homma, Y. [Oarai Branch, Inst. for Mater. Research, University of Tohoku, Ibaraki 311-1313 (Japan); Shiokawa, Y. [Oarai Branch, Inst. for Mater. Research, University of Tohoku, Ibaraki 311-1313 (Japan); Sato, N.K. [Deptartment of Physics, University of Nagoya, Nagoya, 464-8602 (Japan)

    2007-03-15

    We report a superconducting phase diagram of the ferromagnetic superconductor UGe{sub 2} investigated by AC magnetic susceptibility measurements. In contrast to previous phase diagrams, we found that the superconducting transition temperature and volume fraction show a 'M-shaped' structure as a function of pressure. From this observation, we suggest that both of two critical points will play a crucial role in the occurrence of superconductivity in UGe{sub 2}.

  7. Phase Diagram of Wilson and Twisted Mass Fermions at finite isospin chemical potential

    CERN Document Server

    Kieburg, M; Verbaarschot, J J M; Zafeiropoulos, S

    2014-01-01

    Wilson Fermions with untwisted and twisted mass are widely used in lattice simulations. Therefore one important question is whether the twist angle and the lattice spacing affect the phase diagram. We briefly report on the study of the phase diagram of QCD in the parameter space of the degenerate quark masses, isospin chemical potential, lattice spacing, and twist angle by employing chiral perturbation theory. Moreover we calculate the pion masses and their dependence on these four parameters.

  8. PHASE DIAGRAM OF GELATINE-POLYURONATE COLLOIDS: ITS APPLICATION FOR MICROENCAPSULATION AND NOT ONLY

    OpenAIRE

    Alexei Baerle; Olga Dimova; Irina Urumoglova; Pavel Tatarov; Larisa Zadorojnai

    2016-01-01

    Phase state and the charge of colloidal particles in the gelatine-polyuronate system were studied. A method for comparative evaluation of molecular weight of colloids by means of viscosimetric measurements and electrophoresis was developed. It is shown that the Diagram {Phase state = f (composition, pH)} contains six well-defined regions. The diagram explains and predicts the behaviour of protein-polysaccharide colloids, which are included in beverages or forms the shells of oil-containing mi...

  9. Towards the heavy dense QCD phase diagram using Complex Langevin simulations

    CERN Document Server

    Aarts, Gert; Jäger, Benjamin; Seiler, Erhard; Sexty, Dénes; Stamatescu, Ion-Olimpiu

    2015-01-01

    Monte Carlo methods cannot probe far into the QCD phase diagram with a real chemical potential, due to the famous sign problem. Complex Langevin simulations, using adaptive step-size scaling and gauge cooling, are suited for sampling path integrals with complex weights. We report here on tests of the deconfinement transition in pure Yang-Mills SU(3) simulations and present an update on the QCD phase diagram in the limit of heavy and dense quarks.

  10. The 2D Alternative Binary L—J System:Solid—Liquid Phase Diagram

    Institute of Scientific and Technical Information of China (English)

    ZHANGZhi; CHENLi-Rong

    2002-01-01

    The Lennard-Jones potential is introduced into the Collins model and is generalized to the two-dimensional alternative binary system.The Gibbs free energy of the binary system is calculated.According to the thermodynamic conditions of solid-liquid equilibrium,the “cigar-type ” phase diagram and the phase diagram with a minimum are obtained.The results are quite analogous to the behavior of three-dimensional substances.

  11. The 2D Alternative Binary L-J System: Solid-Liquid Phase Diagram

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zhi; CHEN Li-Rong

    2002-01-01

    The Lennard-Jones potential is introduced into the Collins model and is generalized to the two-dimensionalalternative binary system. The Gibbs free energy of the binary system is calculated. According to the thermodynamicconditions of solid-liquid equilibrium, the "cigar-type" phase diagram and the phase diagram with a minimum areobtained. The results are quite analogous to the behavior of three-dimensional substances.

  12. High-Pressure Vibrational Spectroscopy.

    Science.gov (United States)

    Pogson, Mark

    1987-09-01

    Available from UMI in association with The British Library. Requires signed TDF. The study of solids at high pressure and variable temperature enables development of accurate interatomic potential functions over wide ranges of interatomic distances. A review of the main models used in the determination of these potentials is given in Chapter one. A discussion of phonon frequency as a variable physical parameter reflecting the interatomic potential is given. A high pressure Raman study of inorganic salts of the types MSCN, (M = K,Rb,Cs & NH_4^+ ) and MNO_2, (M = K,Na) has been completed. The studies have revealed two new phases in KNO_2 and one new phase in NaNO _2 at high pressure. The accurate phonon shift data have enabled the determination of the pure and biphasic stability regions of the phases of KNO _2. A discussion of the B1, B2 relationship of univalent nitrites is also given. In the series of thiocyanates studied new phases have been found in all four materials. In both the potassium and rubidium salts two new phases have been detected, and in the ceasium salt one new phase has been detected, all at high pressure, from accurate phonon shift data. These transitions are discussed in terms of second-order mechanisms with space groups suggested for all phases, based on Landau's theory of second-order phase transitions. In the ammonium salt one new phase has been detected. This new phase transition has been interpreted as a second-order transition. The series of molecular crystals CH_3 HgX, (X = Cl,Br & I) has been studied at high pressure and at variable temperature. In Chapter five, their phase behaviour at high pressure is detailed along with the pressure dependencies of their phonon frequencies. In the chloride and the bromide two new phases have been detected. In the bromide one has been detected at high temperature and one at high pressure, and latter being interpreted as the stopping of the methyl rotation. In the chloride one phase has been found at

  13. Isothermal section (500  ℃) of phase diagram of Nd-Al-Si ternary system

    Institute of Scientific and Technical Information of China (English)

    龙志林; 周益春; 庄应烘; 陈荣贞; 刘敬旗

    2001-01-01

    The isothermal section of the phase diagram of the ternary system Nd-Al-Si at 500  ℃ (Nd≤50%, mole fraction) has been constructed on the basis of the data obtained by X-ray diffraction analysis, differential thermal analysis, metallographic examination, chemical analysis and electron micro-probe analysis. The obtained diagram consists of 11 single-phase regions, 21 two-phase regions and 11 three-phase regions. There exist two limit solid solutions. The intermetallic compound NdAl1.5Si0.5 has not been found in this section. No evidence of new phase has been observed in this work.

  14. The topological phase diagram of cimetidine: A case of overall monotropy.

    Science.gov (United States)

    Céolin, R; Rietveld, I B

    2017-03-01

    Cimetidine is a histamine H2-receptor antagonist used against peptic ulcers. It is known to exhibit crystalline polymorphism. Forms A and D melt within 0.35 degrees from each other and the enthalpies of fusion are similar as well. The present paper demonstrates how to construct a pressure-temperature phase diagram with only calorimetric and volumetric data available. The phase diagram provides the stability domains and the phase equilibria for the phases A, D, the liquid and the vapor. Cimetidine is overall monotropic with form D the only stable solid phase.

  15. Phase diagrams and magnetic properties of tri-layer superlattices: Mean field study

    Science.gov (United States)

    Naji, S.; Belhaj, A.; Labrim, H.; Bahmad, L.; Benyoussef, A.; El Kenz, A.

    2014-04-01

    Motivated by spintronic device applications, we engineer a superlattice model based on periodic tri-layers consisting of spins σ={1}/{2}, S=1 and q={3}/{2} residing on the sites of a square lattice, interacting with an external magnetic field. We study its phase diagrams and magnetic properties. We determine the corresponding ground state phase diagrams. Then, we show that this Ising lattice model exhibits a ferromagnetic phase F1, two ferrimagnetic phases F2, F3 and an antiferromagnetic phase F4. It is found that the magnetic behaviors depend on the moduli space controlled by the exchange interaction couplings. More precisely, the hysteresis loops have been established.

  16. Determination of the quaternary phase diagram of the water-ethylene glycol-sucrose-NaCl system and a comparison between two theoretical methods for synthetic phase diagrams.

    Science.gov (United States)

    Han, Xu; Liu, Yang; Critser, John K

    2010-08-01

    Characterization of the thermodynamic properties of multi-solute aqueous solutions is of critical importance for biological and biochemical research. For example, the phase diagrams of aqueous systems, containing salts, saccharides, and plasma membrane permeating solutes, are indispensible in the field of cryobiology and pharmacology. However, only a few ternary phase diagrams are currently available for these systems. In this study, an auto-sampler differential scanning calorimeter (DSC) was used to determine the quaternary phase diagram of the water-ethylene glycol-sucrose-NaCl system. To improve the accuracy of melting point measurement, a "mass-redemption" method was also applied for the DSC technique. Base on the analyses of these experimental data, a comparison was made between the two practical approaches to generate phase diagrams of multi-solute solutions from those of single-solute solutions: the summation of cubic polynomial melting point equations versus the use of osmotic virial equations with cross coefficients. The calculated values of the model standard deviations suggested that both methods are satisfactory for characterizing this quaternary system.

  17. Evidence of a new crystalline phase in U–Gd–O phase diagram

    Energy Technology Data Exchange (ETDEWEB)

    Pieck, Darío [CEA, DEN, DEC, SESC – Laboratoire des Lois de Comportement des Combustibles (France); Desgranges, Lionel, E-mail: lionel.desgranges@cea.fr [CEA, DEN, DEC, SESC – Laboratoire des Lois de Comportement des Combustibles (France); Matheron, Pierre [CEA, DEN, DEC, SPUA – Laboratoire Combustibles Uranium (France); Palancher, Hervé [CEA, DEN, DEC, SESC – Laboratoire des Lois de Comportement des Combustibles (France)

    2015-06-15

    The U–Gd–O phase diagram was investigated in its high Gd content part. Several samples with the general (U{sub 1−y}, Gd{sub y})O{sub 2±x} composition were prepared by sintering under Ar H{sub 2} 5% atmosphere. The samples were characterized by SEM–EDS and X-ray diffraction. A new cubic crystalline phase was evidenced at high a Gd content that was not expected from previous literature. Rietveld refinements showed that its crystalline structure is related to C-Gd{sub 2}O{sub 3} phase. The existence of this compound has to be taken into account in the sintering of (U,Gd)O{sub 2} nuclear fuel.

  18. PHASE EQUILIBRIA INVESTIGATION OF BINARY, TERNARY, AND HIGHER ORDER SYSTEMS. PART 9. CALCULATION OF THERMODYNAMIC QUANTITIES FROM PHASE DIAGRAMS

    Science.gov (United States)

    The thermodynamic fundamentals relating phase equilibria in binary and ternary systems to the thermodynamic properties of the phases are reviewed and...system demonstrate the application of the equations for extracting thermodynamic data from phase diagrams and also for the prediction of phase equilibria .

  19. Comparison of actual vs. synthesized ternary phase diagrams for solutes of cryobiological interest.

    Science.gov (United States)

    Kleinhans, F W; Mazur, Peter

    2007-04-01

    Phase diagrams are of great utility in cryobiology, especially, those consisting of a cryoprotective agent (CPA) dissolved in a physiological salt solution. These ternary phase diagrams consist of plots of the freezing points of increasing concentrations of solutions of cryoprotective agents (CPA) plus NaCl. Because they are time-consuming to generate, ternary diagrams are only available for a small number of CPAs. We wanted to determine whether accurate ternary phase diagrams could be synthesized by adding together the freezing point depressions of binary solutions of CPA/water and NaCl/water which match the corresponding solute molality concentrations in the ternary solution. We begin with a low concentration of a solution of CPA+salt of given R (CPA/salt) weight ratio. Ice formation in that solution is mimicked by withdrawing water from it which increases the concentrations of both the CPA and the NaCl. We compute the individual solute concentrations, determine their freezing points from published binary phase diagrams, and sum the freezing points. These yield the synthesized ternary phase diagram for a solution of given R. They were compared with published experimental ternary phase diagrams for glycerol, dimethyl sulfoxide (DMSO), sucrose, and ethylene glycol (EG) plus NaCl in water. For the first three, the synthesized and experimental phase diagrams agreed closely, with some divergence occurring as wt% concentrations exceeded 30% for DMSO and 55% for glycerol, and sucrose. However, in the case of EG there were substantial differences over nearly the entire range of concentrations which we attribute to systematic errors in the experimental EG data. New experimental EG work will be required to resolve this issue.

  20. Synchrotron X-ray diffraction studies of phase transitions and mechanical properties of nanocrystalline materials at high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Prilliman, Gerald Stephen

    2003-09-01

    The behavior of nanocrystals under extreme pressure was investigated using synchrotron x-ray diffraction. A major part of this investigation was the testing of a prototype synchrotron endstation on a bend magnet beamline at the Advanced Light Source for high pressure work using a diamond anvil cell. The experiments conducted and documented here helped to determine issues of efficiency and accuracy that had to be resolved before the construction of a dedicated ''super-bend'' beamline and endstation. The major conclusions were the need for a cryo-cooled monochromator and a fully remote-controllable pressurization system which would decrease the time to change pressure and greatly reduce the error created by the re-placement of the diamond anvil cell after each pressure change. Two very different types of nanocrystal systems were studied, colloidal iron oxide (Fe{sub 2}O{sub 3}) and thin film TiN/BN. Iron oxide nanocrystals were found to have a transition from the {gamma} to the {alpha} structure at a pressure strongly dependent on the size of the nanocrystals, ranging from 26 GPa for 7.2 nm nanocrystals to 37 GPa for 3.6 nm nanocrystals. All nanocrystals were found to remain in the {alpha} structure even after release of pressure. The transition pressure was also found, for a constant size (5.7 nm) to be strongly dependent on the degree of aggregation of the nanocrystals, increasing from 30 GPa for completely dissolved nanocrystals to 45 GPa for strongly aggregated nanocrystals. Furthermore, the x-ray diffraction pattern of the pressure induced {alpha} phase demonstrated a decrease in intensity for certain select peaks. Together, these observations were used to make a complete picture of the phase transition in nanocrystalline systems. The size dependence of the transition was interpreted as resulting from the extremely high surface energy of the {alpha} phase which would increase the thermodynamic offset and thereby increase the kinetic barrier

  1. Phase diagram of electron systems near the superconductor-insulator transition.

    Science.gov (United States)

    Pokrovsky, V L; Falco, G M; Nattermann, T

    2010-12-31

    The zero temperature phase diagram of Cooper pairs exposed to disorder and a magnetic field is determined theoretically from a variational approach. Four distinct phases are found: a Bose and a Fermi insulating, a metallic, and a superconducting phase, respectively. The results explain the giant negative magnetoresistance found experimentally in In-O, TiN, Be and high-T(c) materials.

  2. Phase diagram of a three-sublattice mixed ferro-ferrimagnetic Heisenberg system

    Science.gov (United States)

    Mert, H. Şevki; Mert, Gülistan

    2013-10-01

    We present a numerical study of a three-sublattice mixed ferro-ferrimagnetic Heisenberg system. Green's function technique is used to calculate the magnetization as a function of temperature. The technique involves the random phase approximation and Anderson-Callen's decoupling. We obtain phase diagram and the first-order phase transition.

  3. Nanostructures and phase diagrams of ABC star triblock copolymers in pore geometries.

    Science.gov (United States)

    Li, Shiben; Qiu, Wenjuan; Zhang, Linxi; Liang, Haojun

    2012-03-28

    The nanostructures and phase diagrams of ABC star triblock copolymers in pore geometries are investigated using the real-space self-consistent field theory in two-dimensional space. Two types of pores with neutral surfaces, namely, pores with small and large diameters, are considered. A rich variety of nanostructures are exhibited by the ABC star triblock copolymers in these two types of pores, which differ from those observed in bulk and in other confinements. These structures include perpendicular undulating lamellae, concentric core-shell cylinders, polygonal tiling with cylindrical arrangements, and other complex structures. Triangular phase diagrams for the ABC star triblock copolymers are constructed. The small pores clearly affect the corner and central space of the phase diagrams by distorting the bulk structures into concentric arrangements. Meanwhile, the large pores induce the transformation of bulk structures into concentric structures in most of the phase space, but slightly affect the structures at the center of the phase diagrams. Furthermore, the order-order and order-disorder phase transitions, as well as the stable and metastable phases, in the triangular phase diagrams are examined by analyzing their free energies. These observations on the ABC star triblock copolymers in the pore geometries provide a deeper insight into the behavior of macromolecules in a confined system.

  4. Phase diagram of dilute nuclear matter: Unconventional pairing and the BCS-BEC crossover

    Energy Technology Data Exchange (ETDEWEB)

    Stein, Martin; Sedrakian, Armen [Frankfurt Univ. (Germany). Inst. fuer Theoretische Physik

    2013-07-01

    We report on a comprehensive study of the phase structure of cold, dilute nuclear matter featuring a {sup 3}S{sub 1}-{sup 3}D{sub 1} condensate at non-zero isospin asymmetry, within wide ranges of temperatures and densities. We find a rich phase diagram comprising three superfluid phases, namely a LOFF phase, the ordinary BCS phase, and a heterogeneous, phase-separated BCS phase, with associated crossovers from the latter two phases to a homogeneous or phase-separated Bose-Einstein condensate of deuterons. The phase diagram contains two tri-critical points (one a Lifshitz point), which may degenerate into a single tetra-critical point for some degree of isospin asymmetry.

  5. Influence of finite volume and magnetic field effects on the QCD phase diagram

    CERN Document Server

    Magdy, Niseem; Lacey, Roy A

    2015-01-01

    The Polyakov linear sigma model (PLSM) is used to investigate the respective influence of a finite volume and a magnetic field on the quark-hadron phase boundary in the plane of baryon chemical potential ($\\mu_{B}$) vs. temperature ($T$) of the QCD phase diagram. The calculated results indicate sizable shifts of the quark-hadron phase boundary to lower values of $(\\mu_{B}~\\text{and}~T)$ for increasing magnetic field strength, and an opposite shift to higher values of $(\\mu_{B}~\\text{and}~T)$ for decreasing system volume. Such shifts could have important implications for extraction of the thermodynamic properties of the QCD phase diagram from heavy ion data.

  6. Thermodynamic Optimization of TmCl3-ACl (A=Na, K, Rb, Cs) Phase Diagrams

    Institute of Scientific and Technical Information of China (English)

    Ye Xinyu; Zhang Jing; Sun Yimin; Wang Yu; Tan Junjun

    2005-01-01

    From the measured phase equilibria data and experimental thermochemical properties, the TmCl3-ACl (A=Na, K, Rb, Cs) phase diagrams were optimized and calculated using the CALPHAD technique. For describing the Gibbs energies of the liquid phase in these systems, the new modified quasichemical model in the pair-approximation for short-range ordering was used. A set of thermodynamic functions was optimized and gotten based on an interactive computer-assisted analysis. The calculated phase diagrams and thermodynamic data are self-consistent.

  7. The Cu-Li-Sn Phase Diagram: Isopleths, Liquidus Projection and Reaction Scheme

    OpenAIRE

    Fürtauer, Siegfried; Flandorfer, Hans

    2016-01-01

    The Cu-Li-Sn phase diagram was constructed based on XRD and DTA data of 60 different alloy compositions. Eight ternary phases and 14 binary solid phases form 44 invariant ternary reactions, which are illustrated by a Scheil-Schulz reaction scheme and a liquidus projection. Phase equilibria as a function of concentration and temperature are shown along nine isopleths. This report together with an earlier publication of our group provides for the first time comprehensive investigations of phase...

  8. Low-pressure phase diagram of crystalline benzene from quantum Monte Carlo

    Science.gov (United States)

    Azadi, Sam; Cohen, R. E.

    2016-08-01

    We studied the low-pressure (0-10 GPa) phase diagram of crystalline benzene using quantum Monte Carlo and density functional theory (DFT) methods. We performed diffusion quantum Monte Carlo (DMC) calculations to obtain accurate static phase diagrams as benchmarks for modern van der Waals density functionals. Using density functional perturbation theory, we computed the phonon contributions to the free energies. Our DFT enthalpy-pressure phase diagrams indicate that the Pbca and P21/c structures are the most stable phases within the studied pressure range. The DMC Gibbs free-energy calculations predict that the room temperature Pbca to P21/c phase transition occurs at 2.1(1) GPa. This prediction is consistent with available experimental results at room temperature. Our DMC calculations give 50.6 ± 0.5 kJ/mol for crystalline benzene lattice energy.

  9. High pressure technology 1994

    Energy Technology Data Exchange (ETDEWEB)

    Kapp, J.A.; Picqueuer, L.M. (eds.)

    1994-01-01

    This volume is divided into four sessions: fracture mechanics applications to high pressure vessels; high pressure code issues; high pressure design, analysis, and safety concerns; and military and other high pressure applications. Separate abstracts were prepared for eleven papers of this conference.

  10. In situ observation of multiple phase transitions in low-melting ionic liquid [BMIM][BF4] under high pressure up to 30 GPa.

    Science.gov (United States)

    Su, Lei; Zhu, Xiang; Wang, Zheng; Cheng, Xuerui; Wang, Yongqiang; Yuan, Chaosheng; Chen, Zhenping; Ma, Chunli; Li, Fangfei; Zhou, Qiang; Cui, Qiliang

    2012-02-23

    In situ characterization of phase transitions and direct microscopic observations of a low-melting ionic liquid, 1-butyl-3-methyl imidazolium tetrafluoroborate ([BMIM][BF(4)]), has been performed in detail by Raman spectroscopy. Compression of [BMIM][BF(4)] was measured under hydrostatic pressure up to ~30.0 GPa at room temperature by using a high-pressure diamond anvil cell. With pressure increasing, the characteristic bands of [BMIM][BF(4)] displayed nonmonotonic pressure-induced frequency shifts, and it is found to undergo four successive phase transitions at around 2.25, 6.10, 14.00, and 21.26 GPa. Especially, above a pressure of 21.26 GPa, luminescence of the sample occurs, which is connected with the most significant phase transition at around this pressure. It was indicated that the structure change under high pressure might be associated with a conformational change in the butyl chain. Upon releasing pressure, the spectrum was not recovered under a pressure up to 1.16 GPa, thereby indicating that this high-pressure phase remains stable over a large pressure range between 30 and 1.16 GPa in low-melting ionic liquid [BMIM][BF(4)]. Although the sample was kept under the normal pressure for 24 h, the spectrum was recovered, and it showed that the phase transition of [BMIM][BF(4)] was reversible. In other words, such a low-melting ionic liquid [BMIM][BF(4)] remains stable even after being treated under so a high pressure of up to 30 GPa. © 2012 American Chemical Society

  11. Phase diagram of Fe{sub 1-x}Co{sub x} ultrathin film

    Energy Technology Data Exchange (ETDEWEB)

    Fridman, Yu.A. [V.I. Vernadskiy Taurida National University, Vernadskiy Avenue 4, Simferopol, Crimea 95007 (Ukraine)], E-mail: frid@tnu.crimea.ua; Klevets, Ph.N.; Voytenko, A.P. [V.I. Vernadskiy Taurida National University, Vernadskiy Avenue 4, Simferopol, Crimea 95007 (Ukraine)

    2008-12-15

    Concentration-driven reorientation phase transitions in ultrathin magnetic films of FeCo alloy have been studied. It is established that, in addition to the easy-axis and easy-plane phases, a spatially inhomogeneous phase (domain structure), a canted phase, and also an 'in-plane easy-axis' phase can exist in the system. The realization of the last phase is associated with the competition between the single-ion anisotropy and the magnetoelastic interaction. The critical values of Co concentration corresponding to the phase transitions are evaluated, the types of phase transitions are determined, and the phase diagrams are constructed.

  12. First-principles study on the phase transition, elastic properties and electronic structure of Pt{sub 3}Al alloys under high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yanjun [Key Laboratory of Oil and Gas Equipment of Ministry of Education, Southwest Petroleum University, Chengdu, Sichuan 610500 (China); Huang, Huawei [National Key Laboratory for Nuclear Fuel and Materials, Nuclear Power of China, Chengdu, Sichuan 610041 (China); Pan, Yong, E-mail: yongpanyn@163.com [State Key Laboratory of Advanced Technologies for Comprehensive Utilization of Platinum Metals, Kunming 650106 (China); Zhao, Guanghui; Liang, Zheng [Key Laboratory of Oil and Gas Equipment of Ministry of Education, Southwest Petroleum University, Chengdu, Sichuan 610500 (China)

    2014-06-01

    Highlights: • The phase transition of Pt{sub 3}Al alloys occurs at 60 GPa. • The elastic modulus of Pt{sub 3}Al alloys increase with increasing pressure. • The cubic structure has good resistance to volume deformation under high pressure. • The pressure enhances the hybridization between Pt atom and Al atom. - Abstract: The phase transition, formation enthalpies, elastic properties and electronic structure of Pt{sub 3}Al alloys are studied using first-principle approach. The calculated results show that the pressure leads to phase transition from tetragonal structure to cubic structure at 60 GPa. With increasing pressure, the elastic constants, bulk modulus and shear modulus of these Pt{sub 3}Al alloys increase linearly and the bond lengths of Pt–Al metallic bonds and the peak at E{sub F} decrease. The cubic Pt{sub 3}Al alloy has excellent resistance to volume deformation under high pressure. We suggest that the phase transition is derived from the hybridization between Pt and Al atoms for cubic structure is stronger than that of tetragonal structure and forms the strong Pt–Al metallic bonds under high pressure.

  13. Analytic calculation of phase diagrams for solutions containingcolloids or globular proteins

    Energy Technology Data Exchange (ETDEWEB)

    Tavares, Frederico W.; Prausnitz, John M.

    2003-12-31

    Molecular thermodynamics is used to calculate phase diagrams for aqueous charged dipolar colloids or globular proteins. Because normal pressures are not important for condensed systems, here a phase diagram is a plot of temperature versus colloid concentration. Properties of the fluid phase are obtained from the random-phase approximation, whereas those for the solid phase correspond to a perfect crystal. Crystal structures considered are face-centered and body-centered cubic. For each phase, the Helmholtz energy is determined by the sum of a hard-sphere reference term and a perturbation term that uses a potential of mean force for pairs of charged, dipolar colloids that also interact through dispersion forces. In view of different screening effects on charge-charge repulsion and dipolar attraction, the net electrostatic term features an extremum at intermediate inic strengths leading to a non-monotonic dependence of the phase behavior on salt concentration. Illustrative phase diagrams are shown as a function of colloid charge, dipole momeng, and ionic strength of the aqueous medium. Calculated results show that the phase diagram is sensitive to the structure assumed for the solid phase.

  14. Deriving binary phase diagrams for chromonic materials in water mixtures via fluorescence spectroscopy: cromolyn and water.

    Science.gov (United States)

    Van Hecke, Gerald R; Karukstis, Kerry K; Rayermann, Scott

    2015-01-14

    We report here the first example of a new and novel method of determining the binary temperature-composition phase diagram of a chromonic material in water using its intrinsic fluorescence. Disodium cromoglycate, or cromolyn, is an anti-allergy medicine representative of a class of compounds known as the chromonics. We have discovered that cromolyn's fluorescence is very sensitive to the polarity, hence structure, of the phase it exhibits. The fluorescence signal shifts its wavelength maximum and its shape depending on whether the cromolyn is a single phase or in coexisting phases. Since the signal due to individual phases can be identified, the fluorescence signal can reveal the temperature-induced transitions between single phase and phase coexistence regions. By studying such fluorescence data for different compositions, an isobaric temperature-composition phase diagram may be constructed. We present here a phase diagram derived from fluorescence studies that is in agreement with previous determinations using other techniques. Our results suggest that the binary phase diagrams of other intrinsically fluorescent chromonic materials, such as perylene monoimide and bisimide derivatives used in organic optoelectronic devices, solar cells, and light-emitting diodes, can be studied in water using an analogous fluorescence approach.

  15. Phase diagrams of diblock copolymers in electric fields: a self-consistent field theory study.

    Science.gov (United States)

    Wu, Ji; Wang, Xianghong; Ji, Yongyun; He, Linli; Li, Shiben

    2016-04-21

    We investigated the phase diagrams of diblock copolymers in external electrostatic fields by using real-space self-consistent field theory. The lamella, cylinder, sphere, and ellipsoid structures were observed and analyzed by their segment distributions, which were arranged to two types of phase diagrams to examine the phase behavior in weak and strong electric fields. One type was constructed on the basis of Flory-Huggins interaction parameter and volume fraction. We identified an ellipsoid structure with a body-centered cuboid arrangement as a stable phase and discussed the shift of phase boundaries in the electric fields. The other type of phase diagrams was established on the basis of the dielectric constants of two blocks in the electric fields. We then determined the regions of ellipsoid phase in the phase diagrams to examine the influence of dielectric constants on the phase transition between ellipsoidal and hexagonally packed cylinder phases. A general agreement was obtained by comparing our results with those described in previous experimental and theoretical studies.

  16. Cold hydrogen EOS/phase diagram from DAC experiments to 300 GPa

    Science.gov (United States)

    Eremets, Mikhail

    2013-06-01

    Two new phases of hydrogen have been discovered at room temperature: phase IV above 220 GPa and phase V above 280 GPa. In the present work we studied these phases in a wide temperature range with the aid of Raman, infrared absorption, and electrical measurements at pressures up to 340 GPa. Also, we revised the I-III phase boundary and thus have built a new phase diagram of hydrogen. In particular, we established a new triple point at the phase diagram at 208 GPa and T = 308 K. Our new data further support the previous work that hydrogen is semiconductor in phase IV and most likely semimetal in phase V. M. I. Eremets, I. A. Troyan, A. Drozdov, Ph. Lerch, P. Naumov, Paul Scherrer, Institute, CH 5232 VILLIGEN-PSI, Switzerland.

  17. New phase diagrams for dense carbon-oxygen mixtures and white dwarf evolution

    CERN Document Server

    Althaus, Leandro G; Isern, Jordi; Córsico, Alejandro H; Bertolami, Marcelo M Miller

    2011-01-01

    Cool white dwarfs are reliable and independent stellar chronometers. The most common white dwarfs have carbon-oxygen dense cores. Consequently, the cooling ages of very cool white dwarfs sensitively depend on the adopted phase diagram of the carbon-oxygen binary mixture. A new phase diagram of dense carbon-oxygen mixtures appropriate for white dwarf interiors has been recently obtained using direct molecular dynamics simulations. In this paper, we explore the consequences of this phase diagram in the evolution of cool white dwarfs. To do this we employ a detailed stellar evolutionary code and accurate initial white dwarf configurations, derived from the full evolution of progenitor stars. We use two different phase diagrams, that of Horowitz et al. (2010), which presents an azeotrope, and the phase diagram of Segretain & Chabrier (1993), which is of the spindle form. We computed the evolution of 0.593 and 0.878M_sun white dwarf models during the crystallization phase, and we found that the energy released...

  18. Exploring the conformational space of chromatin fibers and their stability by numerical dynamic phase diagrams.

    Science.gov (United States)

    Stehr, René; Schöpflin, Robert; Ettig, Ramona; Kepper, Nick; Rippe, Karsten; Wedemann, Gero

    2010-03-17

    The three-dimensional structure of chromatin affects DNA accessibility and is therefore a key regulator of gene expression. However, the path of the DNA between consecutive nucleosomes, and the resulting chromatin fiber organization remain controversial. The conformational space available for the folding of the nucleosome chain has been analytically described by phase diagrams with a two-angle model, which describes the chain trajectory by a DNA entry-exit angle at the nucleosome and a torsion angle between consecutive nucleosomes. Here, a novel type of numerical phase diagrams is introduced that relates the geometric phase space to the energy associated with a given chromatin conformation. The resulting phase diagrams revealed differences in the energy landscape that reflect the probability of a given conformation to form in thermal equilibrium. Furthermore, we investigated the effects of entropy and additional degrees of freedom in the dynamic phase diagrams by performing Monte Carlo simulations of the initial chain trajectories. Using our approach, we were able to demonstrate that conformations that initially were geometrically impossible could evolve into energetically favorable states in thermal equilibrium due to DNA bending and torsion. In addition, dynamic phase diagrams were applied to identify chromatin fibers that reflect certain experimentally determined features.

  19. Influence of coupling with calculation of phase diagrams on microsegregation forming simulation of Al-4.5%Cu alloy

    Institute of Scientific and Technical Information of China (English)

    LIU Yong-gang; CHEN Guang; SUN Guo-xiong

    2006-01-01

    The effect of coupling with calculation of phase diagrams on microsegregation forming simulation was investigated. The traditional simplified phase diagram and calculated phase diagram were introduced into the numerical models respectively and simulation on microsegregation forming of the Al-4.5%Cu alloy ingot was also presented. The simulation results were both compared with the experiment results. The results show that the calculated sencondary arm spacing with these two kinds of phase diagram are almost the same because relationship between the coarsening model and the information of phase diagram is not close. The calculated eutectic phase volume fractions of different locations in the ingot coupled with different phase diagrams are discrepant. The calculated volume fractions are consistent with the experiment results when calculated phase diagram couples, but are far from the experiment results and obviously inacceptable when traditional simplified phase diagram couples. So, coupling with accurate calculated phase diagrams is very significant for microsegregation forming simulation since much information of the phase diagram is used in the models and it can improve the precision of simulation results.

  20. Modelling ruptures of buried high-pressure dense-phase CO2 pipelines in carbon capture and storage applications - Part II. A full-scale rupture

    OpenAIRE

    Wareing, CJ; Fairweather, M.; Falle, SAEG; Woolley, RM

    2015-01-01

    Carbon capture and storage (CCS) presents a short-term option for significantly reducing the amount of carbon dioxide (CO2) released into the atmosphere. National Grid initiated the COOLTRANS research programme to consider the CCS pipeline transportation of high-pressure dense-phase CO2, including the development and application of a mathematical model for predicting the sonic near-field dispersion of pure CO2 following pipeline venting or failure. In Part I (Wareing et al., 2015a) validation...

  1. Phase diagram of binary system C12Zn-C18Zn

    Institute of Scientific and Technical Information of China (English)

    Kezhong Wu; Xindong Wang; Xiaodi Liu

    2003-01-01

    The solid-solid phase transitions in the perovskite type layer materials (n-C12H25NH3)2ZnCl4 (C12Zn) and (n-C18H37NH3)2ZnCl4 (C18Zn) that are one kind of potential thermal storage material, were synthesized and, at the same time, a series of their mixtures C12Zn/C18Zn were prepared. The experimental binary phase diagram of C12Zn/C18Zn was established by means of differential scanning calorimetry (DSC) and X-ray diffraction. In the phase diagram a stable solid compound (n-C12H25NH3)(n-C18H37NH3)ZnCl4 (C12C18Zn) and two eutectoid invariants were observed. It is noticeable that the phase diagram contains solid solution ranges.

  2. Experimental evaluation and thermodynamic assessment of the LiF-LuF{sub 3} phase diagram

    Energy Technology Data Exchange (ETDEWEB)

    Santos, I.A. dos [Instituto de Pesquisas Energeticas e Nucleares, CP 11049, Butanta 05422-970, Sao Paulo, SP (Brazil); Klimm, D. [Leibniz Institute for Crystal Growth, Max-Born-Strasse 2, 12489 Berlin (Germany); Baldochi, S.L.; Ranieri, I.M. [Instituto de Pesquisas Energeticas e Nucleares, CP 11049, Butanta 05422-970, Sao Paulo, SP (Brazil)

    2013-01-20

    The phase diagram of the system LiF-LuF{sub 3} has been revised using thermal analysis. Specific heat capacity and enthalpy of phase transition and fusion were measured by differential scanning calorimetry for all compounds belonging to the system. A thermodynamic optimization of the LiF-LuF{sub 3} phase diagram was performed by fitting the Gibbs energy functions to the experimental data that were taken from the literature or measured in this work. Excess energy terms, which describe the effect of interaction between the two fluoride compounds in the liquid solution, were expressed by the Redlich-Kister polynomial function. The assessed phase diagram was in suitable agreement with the re-evaluated experimental data.

  3. Green material composites from renewable resources: Polymorphic transitions and phase diagram of beeswax/rosin resin

    Energy Technology Data Exchange (ETDEWEB)

    Gaillard, Yves [Mines-ParisTech., CEMEF, UMR CNRS 7635, 1 rue Claude Daunesse 06904 Sophia Antipolis cedex (France); Mija, Alice [University of Nice-Sophia Antipolis, Thermokinetic Group, Laboratory of Chemistry of Organic and Metallic Materials C.M.O.M., 06108 Nice Cedex 2 (France); Burr, Alain; Darque-Ceretti, Evelyne; Felder, Eric [Mines-ParisTech., CEMEF, UMR CNRS 7635, 1 rue Claude Daunesse 06904 Sophia Antipolis cedex (France); Sbirrazzuoli, Nicolas, E-mail: sbirrazz@unice.fr [University of Nice-Sophia Antipolis, Thermokinetic Group, Laboratory of Chemistry of Organic and Metallic Materials C.M.O.M., 06108 Nice Cedex 2 (France)

    2011-07-10

    Highlights: {yields} Blends of Rosin and beeswax are studied by DSC, XRD, and optical microscopy. {yields} The first phase diagram beeswax/rosin is established. {yields} Polymorphic transitions are identified and appear to be highly related to rosin content. - Abstract: Rosin and beeswax are two complex natural materials presenting numerous applications in paints, adhesives, varnishes or inks. Melted, they are particularly interesting for their adhesion properties. This paper establishes the first phase diagram beeswax/rosin blends. A systematic approach using X-ray diffraction (XRD), differential scanning calorimetry (DSC) and polarised optical microscopy (POM) has been performed in order to describe the crystallographic structure and the thermal properties of two materials, beeswax and rosin, and their blends. Indeed, melting, softening and crystallisation temperatures, polymorphic transitions but also crystalline index has been investigated. The resulting phase diagram reveals a complex behaviour in terms of phase transformation and time-dependent phenomenon mainly representative of the complex composition of beeswax.

  4. The topological pressure-temperature phase diagram of fluoxetine nitrate: monotropy unexpectedly turning into enantiotropy

    Science.gov (United States)

    Céolin, René; Rietveld, Ivo B.

    2017-04-01

    The phase behavior of pharmaceuticals is important for regulatory requirements and dosage form development. Racemic fluoxetine nitrate possesses two crystalline forms for which initial measurements indicated that they have a monotropic relationship with form I the only stable form. By constructing the topological pressure-temperature phase diagram, it has been shown that unexpectedly form II has a stable domain in the phase diagram and can be easily obtained by heating and grinding. The pressure necessary to obtain form II is only 11 MPa, which is much lower than most pressure used for tableting in the pharmaceutical industry.

  5. Phase Diagrams of Quasispecies Theory with Recombination and Horizontal Gene Transfer

    Science.gov (United States)

    Park, J.-M.; Deem, M. W.

    2007-02-01

    We consider how transfer of genetic information between individuals influences the phase diagram and mean fitness of both the Eigen and the parallel, or Crow-Kimura, models of evolution. In the absence of genetic transfer, these physical models of evolution consider the replication and point mutation of the genomes of independent individuals in a large population. A phase transition occurs, such that below a critical mutation rate an identifiable quasispecies forms. We show how transfer of genetic information changes the phase diagram and mean fitness and introduces metastability in quasispecies theory, via an analytic field theoretic mapping.

  6. Phase diagram and thermodynamic calculations of alkali and alkaline earth metal zirconates

    Energy Technology Data Exchange (ETDEWEB)

    Dash, S. [Bhabha Atomic Res. Centre, Bombay (India). Fuel Chem. Div.; Sood, D.D. [Bhabha Atomic Res. Centre, Bombay (India). Fuel Chem. Div.; Prasad, R. [Bhabha Atomic Res. Centre, Bombay (India). Fuel Chem. Div.

    1996-02-01

    The ternary phase diagrams and partial pressures of various gaseous species over the equilibrium phase fields have been calculated for the M-Zr-O (M=Li, Na, K, Rb, Cs, Sr and Ba) systems by using the SOLGASMIX-PV program, which computes equilibrium composition by direct minimization of the Gibbs energy of a system. The available experimental Gibbs energy data reported in the literature for binary and ternary compounds were used for these calculations. Where no data exist, values were estimated. These ternary phase diagrams are being reported for the first time, except for the lithium system. (orig.).

  7. Phase diagram and thermodynamic calculations of alkali and alkaline earth metal zirconates

    Science.gov (United States)

    Dash, Smruti; Sood, D. D.; Prasad, R.

    1996-02-01

    The ternary phase diagrams and partial pressures of various gaseous species over the equilibrium phase fields have been calculated for the MZrO (M = Li, Na, K, Rb, Cs, Sr and Ba) systems by using the SOLGASMIX-PV program, which computes equilibrium composition by direct minimization of the Gibbs energy of a system. The available experimental Gibbs energy data reported in the literature for binary and ternary compounds were used for these calculations. Where no data exist, values were estimated. These ternary phase diagrams are being reported for the first time, except for the lithium system.

  8. Isomorphs in the phase diagram of a model liquid without inverse power law repulsion

    DEFF Research Database (Denmark)

    Veldhorst, Arnold Adriaan; Bøhling, Lasse; Dyre, J. C.;

    2012-01-01

    It is demonstrated by molecular dynamics simulations that liquids interacting via the Buckingham potential are strongly correlating, i.e., have regions of their phase diagram where constant-volume equilibrium fluctuations in the virial and potential energy are strongly correlated. A binary...... Buckingham liquid is cooled to a viscous phase and shown to have isomorphs, which are curves in the phase diagram along which structure and dynamics in appropriate units are invariant to a good approximation. To test this, the radial distribution function, and both the incoherent and coherent intermediate...

  9. Phase Diagram of the Two-Dimensional Ising Model with Dipolar Interaction

    Institute of Scientific and Technical Information of China (English)

    SUN Gang; CHU Qian-Jin

    2001-01-01

    We treat the two-dimensional Ising model with the dipolar interaction by the numerical calculation under the restriction that the spin configurations are distributed with a 4 × 4 period. The phase diagram with respect to temperature and dipolar interaction strength is constructed. Most characters of the phase diagram are consistent with those obtained in the references by the Monte Carlo simulation, except that we find a new rectangle phase, which is ordered in the spin structure with the 1 × 2 rectangle.

  10. Phase diagrams of vortex matter with multi-scale inter-vortex interactions in layered superconductors

    Science.gov (United States)

    Meng, Qingyou; Varney, Christopher N.; Fangohr, Hans; Babaev, Egor

    2017-01-01

    It was recently proposed to use the stray magnetic fields of superconducting vortex lattices to trap ultracold atoms for building quantum emulators. This calls for new methods for engineering and manipulating of the vortex states. One of the possible routes utilizes type-1.5 superconducting layered systems with multi-scale inter-vortex interactions. In order to explore the possible vortex states that can be engineered, we present two phase diagrams of phenomenological vortex matter models with multi-scale inter-vortex interactions featuring several attractive and repulsive length scales. The phase diagrams exhibit a plethora of phases, including conventional 2D lattice phases, five stripe phases, dimer, trimer, and tetramer phases, void phases, and stable low-temperature disordered phases. The transitions between these states can be controlled by the value of an applied external field.

  11. Phase transition and optical properties of CaCl2 under high pressure by ab initio pseudopotential plane-wave calculations

    Science.gov (United States)

    Liu, Y. H.; Ma, Y. M.; He, Z.; Cui, T.; Liu, B. B.; Zou, G. T.

    2007-10-01

    We present a detailed investigation of CaCl2 under high pressure in CaCl2 (Pnnm,Z = 2) and α-PbO2 (Pbcn, Z = 4) phases, respectively. Theoretical calculations are performed by using the ab initio pseudopotential plane-wave method based on the density functional method. We estimate the transition pressure between the two phases by the crossing point of their enthalpies, which are equivalent to the Gibbs free energy at zero temperature, after optimizing the structures under high pressure. Our results show that the transition happens at about 2.9 GPa, which is in agreement with the experimental data. We calculate the structural parameters, charge transfers, bond structures, density of states and optical properties. The calculated results show that there are no charge transfers in CaCl2 structure under high pressure. It is found that the transitions from the Cl 3p to Ca 4s and Cl 3s to Ca 3p orbitals contribute mainly to the dielectric function. The optical properties of CaCl2 (Pnnm, Z = 2) do not vary much under pressure. However, some of the dispersion curves of optical constants in the α-PbO2 (Pbcn, Z = 4) phase are changed significantly under pressure.

  12. Phase transition and optical properties of CaCl{sub 2} under high pressure by ab initio pseudopotential plane-wave calculations

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Y H; Ma, Y M; He, Z; Cui, T; Liu, B B; Zou, G T [National Lab of Superhard Materials, Jilin University, Changchun 130012 (China)

    2007-10-24

    We present a detailed investigation of CaCl{sub 2} under high pressure in CaCl{sub 2} (Pnnm,Z = 2) and {alpha}-PbO{sub 2} (Pbcn, Z = 4) phases, respectively. Theoretical calculations are performed by using the ab initio pseudopotential plane-wave method based on the density functional method. We estimate the transition pressure between the two phases by the crossing point of their enthalpies, which are equivalent to the Gibbs free energy at zero temperature, after optimizing the structures under high pressure. Our results show that the transition happens at about 2.9 GPa, which is in agreement with the experimental data. We calculate the structural parameters, charge transfers, bond structures, density of states and optical properties. The calculated results show that there are no charge transfers in CaCl{sub 2} structure under high pressure. It is found that the transitions from the Cl 3p to Ca 4s and Cl 3s to Ca 3p orbitals contribute mainly to the dielectric function. The optical properties of CaCl{sub 2} (Pnnm, Z = 2) do not vary much under pressure. However, some of the dispersion curves of optical constants in the {alpha}-PbO{sub 2} (Pbcn, Z = 4) phase are changed significantly under pressure.

  13. Phase equilibrium at high pressure of heavy oil fraction in propane and n-butane; Equilibrio de fases em alta pressao de fracoes pesadas do petroleo em propano e n-butano

    Energy Technology Data Exchange (ETDEWEB)

    Canziani, Daniel B.; Ndiaye, Papa M. [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil); Oliveira, Jose V. de; Corazza, Marcos L. [Universidade Regional Integrada, Erechim, RS (Brazil)

    2008-07-01

    One of the biggest challenge of the oil industry is the preparation and adequacy of existing refineries for processing of heavy oil in large quantities. Specifically aims of this work is to measure phase equilibria date at high-pressure with systems involving GOP (Heavy Gasoil), RAT (Atmospheric Residue) and Marlim (crude oil) in n-butane and propane, using the static-synthetic method. The influence of the addition of methanol on the transition pressure is also investigated. With regard to tests made with the use of methanol as a co-solvent, those with higher levels of methanol (5% in mass fraction) had presented transition pressures a little higher than systems with 1% of methanol and systems without methanol. The systems without methanol showed similar pressures. All systems are PT diagrams of the type Lower Critical Solution Temperature (LCST). Among the solvents used the n-butane shown to be the most soluble for all solutes, in particular for the RAT. With the n-butane were observed only liquid-vapour equilibria, and with propane the liquid-liquid, liquid-liquid-vapour and liquid-liquid-fluid equilibria could be observed. The system Propane-5%Methanol-GOP presented liquid-liquid-vapour transitions, indicates be a diagram of the type V (according to the classification of van Konynenburg and Scott). (author)

  14. The phase diagram of scalar field theory on the fuzzy disc

    Energy Technology Data Exchange (ETDEWEB)

    Rea, Simone; Sämann, Christian [Maxwell Institute for Mathematical Sciences, Department of Mathematics,Heriot-Watt University,Colin Maclaurin Building, Riccarton, Edinburgh EH14 4AS (United Kingdom)

    2015-11-17

    Using a recently developed bootstrapping method, we compute the phase diagram of scalar field theory on the fuzzy disc with quartic even potential. We find three distinct phases with second and third order phase transitions between them. In particular, we find that the second order phase transition happens approximately at a fixed ratio of the two coupling constants defining the potential. We compute this ratio analytically in the limit of large coupling constants. Our results qualitatively agree with previously obtained numerical results.

  15. Morphology and phase diagram of comb block copolymer Am+1(BC)m.

    Science.gov (United States)

    Jiang, Zhibin; Wang, Rong; Xue, Gi

    2009-05-28

    The morphologies and the phase diagram of comb copolymer Am+1(BC)m are investigated by the self-consistent field theory. By changing the volume fractions of the blocks, the interaction parameters between the different blocks, and the side chain number, nine phases are found, including the two-colored lamellar phase, three-colored lamellar phase, hexagonal lattice phase, core shell hexagonal lattice phase, two interpenetrating tetragonal lattice, core shell tetragonal lattice, lamellar phase with beads inside, lamellar phase with alternating beads, and disordered phase. The phase diagrams are constructed for Am+1(BC)m with different side chain numbers of m=1, 2, 3, and 5. Due to the asymmetric topology of comb copolymer Am+1(BC)m, the phases and the diagrams are very different from linear ABC triblock copolymer or star ABC triblock copolymer. When the volume fraction of one of the blocks is the domination, the (core shell) hexagonal phase or two interpenetrating tetragonal lattice can form, depending on which block dominates and the interaction between the blocks. The (core shell) hexagonal phase easily forms at the corner of the block A (fA>or=0.5). The side chain number m affects the phase diagram largely due to the fact that the architecture of a comb copolymer is not invariant under the interchange between the three different monomers. Due to the connectivity of the blocks B and the inner blocks A, Am+1(BC)m comb copolymers with the longer main chain A or longer side chain with short block C, i.e., longer block B, are difficult to phase separate. The results are helpful to design nano- or biomaterials with complex architecture or tailor the phase behavior of comb copolymers.

  16. Phase diagram for a mixture of colloids and polymers with equal size

    NARCIS (Netherlands)

    Tuinier, R.; Smith, P.A.; Poon, W.C.K.; Egelhaaf, S.U.; Aarts, D.G.A.L.; Lekkerkerker, H.N.W.; Fleer, G.J.

    2008-01-01

    We present the phase diagram of a colloid-polymer mixture in which the radius a of the colloidal spheres is approximately the same as the radius R of a polymer coil (q=R/a1). A three-phase coexistence region is experimentally observed, previously only reported for colloid-polymer mixtures with small

  17. The phase diagram of the massive Gross-Neveu model, revisited

    CERN Document Server

    Schnetz, O; Urlichs, K; Schnetz, Oliver; Thies, Michael; Urlichs, Konrad

    2005-01-01

    The massive Gross-Neveu model is solved in the large N limit at finite temperature and chemical potential. The phase diagram features a kink-antikink crystal phase which was missed in previous works. Translated into the framework of condensed matter physics our results generalize the bipolaron lattice in non-degenerate conducting polymers to finite temperature.

  18. Two-Phase Critical Discharge of Initially Saturated or Subcooled Water Flowing in Sharp-Edgred Tubes at High Pressure

    Institute of Scientific and Technical Information of China (English)

    1995-01-01

    The transient critical flow experiment with sharp-deged tubes as the break geometries is conducted in high pressure convective circulation test loop of Xi'an Jiantong University.The initial Steady operation pressure is up to 22.0MPa.An empirical correlation was made to obtain the critical mass flow rates,the critical pressure ratio and the thermal nonequilibrium number were correlated as the functions of the tube length to tube diameter ratio L/D.The predicted critical mass flow rate gets a higher accureacy for short tubes with L/D 12.

  19. High Pressure Hydrogen from First Principles

    Science.gov (United States)

    Morales, M. A.

    2014-12-01

    Typical approximations employed in first-principles simulations of high-pressure hydrogen involve the neglect of nuclear quantum effects (NQE) and the approximate treatment of electronic exchange and correlation, typically through a density functional theory (DFT) formulation. In this talk I'll present a detailed analysis of the influence of these approximations on the phase diagram of high-pressure hydrogen, with the goal of identifying the predictive capabilities of current methods and, at the same time, making accurate predictions in this important regime. We use a path integral formulation combined with density functional theory, which allows us to incorporate NQEs in a direct and controllable way. In addition, we use state-of-the-art quantum Monte Carlo calculations to benchmark the accuracy of more approximate mean-field electronic structure calculations based on DFT, and we use GW and hybrid DFT to calculate the optical properties of the solid and liquid phases near metallization. We present accurate predictions of the metal-insulator transition on the solid, including structural and optical properties of the molecular phase. This work was supported by the U.S. Department of Energy at the Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and by LDRD Grant No. 13-LW-004.

  20. The Use of Computer Graphics to Teach Thermodynamic Phase Diagrams.

    Science.gov (United States)

    Naik, Chandrashekhar D.; And Others

    1985-01-01

    Describes an interactive graphics package which illustrates the phase behavior of binary mixtures. The package has been successfully used with graduate and undergraduate students in the chemical engineering curriculum at Cornell University. Features contributing to this success are noted. (JN)