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Sample records for metastable phase diagram

  1. Modeling of metastable phase formation diagrams for sputtered thin films.

    Science.gov (United States)

    Chang, Keke; Music, Denis; To Baben, Moritz; Lange, Dennis; Bolvardi, Hamid; Schneider, Jochen M

    2016-01-01

    A method to model the metastable phase formation in the Cu-W system based on the critical surface diffusion distance has been developed. The driver for the formation of a second phase is the critical diffusion distance which is dependent on the solubility of W in Cu and on the solubility of Cu in W. Based on comparative theoretical and experimental data, we can describe the relationship between the solubilities and the critical diffusion distances in order to model the metastable phase formation. Metastable phase formation diagrams for Cu-W and Cu-V thin films are predicted and validated by combinatorial magnetron sputtering experiments. The correlative experimental and theoretical research strategy adopted here enables us to efficiently describe the relationship between the solubilities and the critical diffusion distances in order to model the metastable phase formation during magnetron sputtering.

  2. Multicritical phase diagrams of the Blume-Emery-Griffiths model with repulsive biquadratic coupling including metastable phases: the pair approximation and the path probability method with pair distribution

    International Nuclear Information System (INIS)

    Keskin, Mustafa; Erdinc, Ahmet

    2004-01-01

    As a continuation of the previously published work, the pair approximation of the cluster variation method is applied to study the temperature dependences of the order parameters of the Blume-Emery-Griffiths model with repulsive biquadratic coupling on a body centered cubic lattice. We obtain metastable and unstable branches of the order parameters besides the stable branches and phase transitions of these branches are investigated extensively. We study the dynamics of the model by the path probability method with pair distribution in order to make sure that we find and define the metastable and unstable branches of the order parameters completely and correctly. We present the metastable phase diagram in addition to the equilibrium phase diagram and also the first-order phase transition line for the unstable branches of the quadrupole order parameter is superimposed on the phase diagrams. It is found that the metastable phase diagram and the first-order phase boundary for the unstable quadrupole order parameter always exist at the low temperatures which are consistent with experimental and theoretical works

  3. Multicritical phase diagrams of the ferromagnetic spin-3/2 Blume-Emery-Griffiths model with repulsive biquadratic coupling including metastable phases: The cluster variation method and the path probability method with the point distribution

    Energy Technology Data Exchange (ETDEWEB)

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

    2008-01-15

    We study the thermal variations of the ferromagnetic spin-3/2 Blume-Emery-Griffiths (BEG) model with repulsive biquadratic coupling by using the lowest approximation of the cluster variation method (LACVM) in the absence and presence of the external magnetic field. We obtain metastable and unstable branches of the order parameters besides the stable branches and phase transitions of these branches are investigated extensively. The classification of the stable, metastable and unstable states is made by comparing the free energy values of these states. We also study the dynamics of the model by using the path probability method (PPM) with the point distribution in order to make sure that we find and define the metastable and unstable branches of the order parameters completely and correctly. We present the metastable phase diagrams in addition to the equilibrium phase diagrams in the (kT/J, K/J) and (kT/J, D/J) planes. It is found that the metastable phase diagrams always exist at the low temperatures, which are consistent with experimental and theoretical works.

  4. Multicritical phase diagrams of the ferromagnetic spin-3/2 Blume-Emery-Griffiths model with repulsive biquadratic coupling including metastable phases: The cluster variation method and the path probability method with the point distribution

    International Nuclear Information System (INIS)

    Keskin, Mustafa; Canko, Osman

    2008-01-01

    We study the thermal variations of the ferromagnetic spin-3/2 Blume-Emery-Griffiths (BEG) model with repulsive biquadratic coupling by using the lowest approximation of the cluster variation method (LACVM) in the absence and presence of the external magnetic field. We obtain metastable and unstable branches of the order parameters besides the stable branches and phase transitions of these branches are investigated extensively. The classification of the stable, metastable and unstable states is made by comparing the free energy values of these states. We also study the dynamics of the model by using the path probability method (PPM) with the point distribution in order to make sure that we find and define the metastable and unstable branches of the order parameters completely and correctly. We present the metastable phase diagrams in addition to the equilibrium phase diagrams in the (kT/J, K/J) and (kT/J, D/J) planes. It is found that the metastable phase diagrams always exist at the low temperatures, which are consistent with experimental and theoretical works

  5. Phase diagrams from ab-initio calculations: Re-W and Fe-B

    Energy Technology Data Exchange (ETDEWEB)

    Hammerschmidt, Thomas; Bialon, Arthur; Palumbo, Mauro; Fries, Suzana G.; Drautz, Ralf [ICAMS, Ruhr-Universitaet Bochum (Germany)

    2011-07-01

    The CALPHAD (CaLculation of Phase Diagrams) method relies on Gibbs energy databases and is of limited predictive power in cases where only limited experimental data is available for constructing the Gibbs energy databases. This is problematic for, e.g., the calculation of the phase transformation kinetics within phase field simulations that not only require the thermodynamic equilibrium data but also information on metastable phases. Such information is difficult to obtain directly from experiment but ab-initio calculations may supplement experimental databases as they comprise metastable phases and arbitrary chemical compositions. We present simulations for two prototypical systems: Re-W and Fe-B. For both systems we calculate the heat of formation for an extensive set of structures using ab-initio calculations and employ the total energies in CALPHAD in order to determine the corresponding phase diagrams. We account for the configurational entropy within the Bragg-Williams approximation and neglect the phenomenological excess-term that is commonly used in CALPHAD as well as the contribution of phonons and electronic excitations to the free energy. According to our calculations the complex intermetallic phases in Re-W are stabilized by the configurational entropy. For Fe-B, we calculate metastable and stable phase diagrams including recently predicted new stable phases.

  6. Stable, metastable, and kinetically trapped amyloid aggregate phases.

    Science.gov (United States)

    Miti, Tatiana; Mulaj, Mentor; Schmit, Jeremy D; Muschol, Martin

    2015-01-12

    Self-assembly of proteins into amyloid fibrils plays a key role in a multitude of human disorders that range from Alzheimer's disease to type II diabetes. Compact oligomeric species, observed early during amyloid formation, are reported as the molecular entities responsible for the toxic effects of amyloid self-assembly. However, the relation between early-stage oligomeric aggregates and late-stage rigid fibrils, which are the hallmark structure of amyloid plaques, has remained unclear. We show that these different structures occupy well-defined regions in a peculiar phase diagram. Lysozyme amyloid oligomers and their curvilinear fibrils only form after they cross a salt and protein concentration-dependent threshold. We also determine a boundary for the onset of amyloid oligomer precipitation. The oligomeric aggregates are structurally distinct from rigid fibrils and are metastable against nucleation and growth of rigid fibrils. These experimentally determined boundaries match well with colloidal model predictions that account for salt-modulated charge repulsion. The model also incorporates the metastable and kinetic character of oligomer phases. Similarities and differences of amyloid oligomer assembly to metastable liquid-liquid phase separation of proteins and to surfactant aggregation are discussed.

  7. Phase diagrams of superconducting materials: Metallurgy, fabrication, and applications

    International Nuclear Information System (INIS)

    Flukiger, R.

    1981-01-01

    Because a large number of investigations on superconducting material have been made on insufficiently characterized samples, and with temperature phase diagrams which contained serious errors, phase diagrams are studied. It is seen that the variation of critical temperature as a function of chemical composition for a given compound can be used as a supplementary tool in determining composition with greater accuracy. The consequent search for higher critical temperature value in specified materials has led to a new concept in determining high temperature phase diagrams. Most of this paper is devoted to the study of bulk binary, pseudobinary, or ternary superconductors at their equilibrium state. As will be shown in several cases, these data serve as standard values and are of great help in understanding the superconducting behavior in materials produced by non-equilibrium methods, i.e., splat-cooling, thin film preparation by either sputtering, co-evaporation, or CVD, and diffusion processes in multifilamentary composite wires. An example for the departure from thermal equilibrium is the retention of metastable composition by a fast quenching rate

  8. Novel phase diagram behavior and materials design in heterostructural semiconductor alloys.

    Science.gov (United States)

    Holder, Aaron M; Siol, Sebastian; Ndione, Paul F; Peng, Haowei; Deml, Ann M; Matthews, Bethany E; Schelhas, Laura T; Toney, Michael F; Gordon, Roy G; Tumas, William; Perkins, John D; Ginley, David S; Gorman, Brian P; Tate, Janet; Zakutayev, Andriy; Lany, Stephan

    2017-06-01

    Structure and composition control the behavior of materials. Isostructural alloying is historically an extremely successful approach for tuning materials properties, but it is often limited by binodal and spinodal decomposition, which correspond to the thermodynamic solubility limit and the stability against composition fluctuations, respectively. We show that heterostructural alloys can exhibit a markedly increased range of metastable alloy compositions between the binodal and spinodal lines, thereby opening up a vast phase space for novel homogeneous single-phase alloys. We distinguish two types of heterostructural alloys, that is, those between commensurate and incommensurate phases. Because of the structural transition around the critical composition, the properties change in a highly nonlinear or even discontinuous fashion, providing a mechanism for materials design that does not exist in conventional isostructural alloys. The novel phase diagram behavior follows from standard alloy models using mixing enthalpies from first-principles calculations. Thin-film deposition demonstrates the viability of the synthesis of these metastable single-phase domains and validates the computationally predicted phase separation mechanism above the upper temperature bound of the nonequilibrium single-phase region.

  9. Metastable and equilibrium phase diagrams of unconjugated bilirubin IXα as functions of pH in model bile systems: Implications for pigment gallstone formation

    Science.gov (United States)

    Berman, Marvin D.

    2014-01-01

    Metastable and equilibrium phase diagrams for unconjugated bilirubin IXα (UCB) in bile are yet to be determined for understanding the physical chemistry of pigment gallstone formation. Also, UCB is a molecule of considerable biomedical importance because it is a potent antioxidant and an inhibitor of atherogenesis. We employed principally a titrimetric approach to obtain metastable and equilibrium UCB solubilities in model bile systems composed of taurine-conjugated bile salts, egg yolk lecithin (mixed long-chain phosphatidylcholines), and cholesterol as functions of total lipid concentration, biliary pH values, and CaCl2 plus NaCl concentrations. Metastable and equilibrium precipitation pH values were obtained, and average pKa values of the two carboxyl groups of UCB were calculated. Added lecithin and increased temperature decreased UCB solubility markedly, whereas increases in bile salt concentrations and molar levels of urea augmented solubility. A wide range of NaCl and cholesterol concentrations resulted in no specific effects, whereas added CaCl2 produced large decreases in UCB solubilities at alkaline pH values only. UV-visible absorption spectra were consistent with both hydrophobic and hydrophilic interactions between UCB and bile salts that were strongly influenced by pH. Reliable literature values for UCB compositions of native gallbladder biles revealed that biles from hemolytic mice and humans with black pigment gallstones are markedly supersaturated with UCB and exhibit more acidic pH values, whereas biles from nonstone control animals and patients with cholesterol gallstone are unsaturated with UCB. PMID:25359538

  10. Formation of stable and metastable phases in reciprocal systems PbSe + MI2 = MSe + PbI2 (M = Hg, Mn, Sn)

    International Nuclear Information System (INIS)

    Odin, I.N.; Grin'ko, V.V.; Kozlovskij, V.F.; Safronov, E.V.; Gapanovich, M.V.

    2004-01-01

    Using data of differential thermal, X-ray phase and microstructural analyses, phase diagrams of reciprocal systems PbSe + MI 2 = MSe + PbI 2 (M=Hg (1), Mn (2), Sn (3)) were constructed. It was ascertained that the HgSe-PbI 2 diagonal in system 1 is stable. Transformations leading to crystallization of metastable ternary compound formed in the system PbSe-PbI 2 and metastable polytypes of lead iodide in systems 1 and 2 in the range of temperatures from 620 to 685 K were studied. New intermediate metastable phases in systems 1, 2 and 3 were prepared by melt quenching. Crystal lattice parameters of the phases crystallizing in the CdCl 2 structural type were defined [ru

  11. The liquid metastable miscibility gap in Cu-based systems

    DEFF Research Database (Denmark)

    Curiotto, S.; Greco, R.; Pryds, Nini

    2007-01-01

    Some Cu-based alloys, like Cu–Co, Cu–Fe and Cu–Co–Fe, display a liquid metastable miscibility gap. When the melt is undercooled below a certain temperature depending on the alloy composition, they present a separation in two liquid phases, followed by coagulation before dendritic solidification....... In order to predict the phase equilibria and the mechanisms of microstructure formation, a determination of the metastable monotectics in the phase diagrams is essential. This paper focuses on the up-to-date findings on the Cu–Co, Cu–Fe and Cu–Co–Fe metastable miscibility gap in the liquid phase...

  12. 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.

  13. Stable and metastable equilibrium states of the Zr-O system

    International Nuclear Information System (INIS)

    Versaci, R.A.; Abriata, J.P.; Garces, J.; Comision Nacional de Energia Atomica, San Carlos de Bariloche

    1987-01-01

    The precise knowledge of the phase diagrams is of fundamental importance for the comprehension of processes like soldering and thermal treatment. The Zr-O diagram has been widely studied, mainly in the zone corresponding to ZrO 2 . A critical analysis of the existing information about this diagram is presented. Furthermore, a lot of information about the phase equilibrium, metastable phase, crystal structure, thermodynamic properties and a possible diagram for pressures higher than one atmosphere is presented. (M.E.L.) [es

  14. Metastable and equilibrium phase diagrams of unconjugated bilirubin IXα as functions of pH in model bile systems: Implications for pigment gallstone formation.

    Science.gov (United States)

    Berman, Marvin D; Carey, Martin C

    2015-01-01

    Metastable and equilibrium phase diagrams for unconjugated bilirubin IXα (UCB) in bile are yet to be determined for understanding the physical chemistry of pigment gallstone formation. Also, UCB is a molecule of considerable biomedical importance because it is a potent antioxidant and an inhibitor of atherogenesis. We employed principally a titrimetric approach to obtain metastable and equilibrium UCB solubilities in model bile systems composed of taurine-conjugated bile salts, egg yolk lecithin (mixed long-chain phosphatidylcholines), and cholesterol as functions of total lipid concentration, biliary pH values, and CaCl2 plus NaCl concentrations. Metastable and equilibrium precipitation pH values were obtained, and average pKa values of the two carboxyl groups of UCB were calculated. Added lecithin and increased temperature decreased UCB solubility markedly, whereas increases in bile salt concentrations and molar levels of urea augmented solubility. A wide range of NaCl and cholesterol concentrations resulted in no specific effects, whereas added CaCl2 produced large decreases in UCB solubilities at alkaline pH values only. UV-visible absorption spectra were consistent with both hydrophobic and hydrophilic interactions between UCB and bile salts that were strongly influenced by pH. Reliable literature values for UCB compositions of native gallbladder biles revealed that biles from hemolytic mice and humans with black pigment gallstones are markedly supersaturated with UCB and exhibit more acidic pH values, whereas biles from nonstone control animals and patients with cholesterol gallstone are unsaturated with UCB. Copyright © 2015 the American Physiological Society.

  15. Ab initio calculation of the bcc Fe-Al phase diagram including magnetic interactions

    International Nuclear Information System (INIS)

    Gonzales-Ormeno, Pablo Guillermo; Petrilli, Helena Maria; Schoen, Claudio Geraldo

    2006-01-01

    The metastable phase diagram of the body-centered cubic-based ordering equilibria in the Fe-Al system has been calculated by the cluster expansion method, through the combination of the full potential-linear augmented plane wave and cluster variation methods. The results are discussed with reference to the effect of including the spin polarizations of Fe in the thermodynamic model

  16. Chalcogenides Metastability and Phase Change Phenomena

    CERN Document Server

    Kolobov, Alexander V

    2012-01-01

    A state-of-the-art description of metastability observed in chalcogenide alloys is presented with the accent on the underlying physics. A comparison is made between sulphur(selenium)-based chalcogenide glasses, where numerous photo-induced phenomena take place entirely within the amorphous phase, and tellurides where a reversible crystal-to-amorphous phase-change transformation is a major effect. Applications of metastability in devices¿optical memories and nonvolatile electronic phase-change random-access memories among others are discussed, including the latest trends. Background material essential for understanding current research in the field is also provided.

  17. Structural Properties and Thermodynamic Stability of Metastable Phases in the Zr-Nb and Ti-V Systems

    International Nuclear Information System (INIS)

    Aurelio, Gabriela

    2003-01-01

    analysis was applied to the data which involves a reference behaviour based on the composition and temperature dependence of the lattice parameters of the Ω and β phases.Such analysis leads to a consistent picture of the isothermal reactions occurring at high temperature which involve composition changes in the Ω and β phases.Using microanalysis techniques, these composition changes were directly determined in aged Zr-Nb alloys.Finally, the results in the present work open up the possibility of using neutron diffraction experiments to gain insight into the stable and metastable phase diagrams of the Zr-Nb and Ti-V systems

  18. Synthesis, thermal properties and recrystallization of ball-milled high Tc superconductors. (Topological stabilization of metastable phases)

    International Nuclear Information System (INIS)

    Schulz, R.; Lanteigne, J.; Simoneau, M.; Tessier, P.; Neste, A. van; Strom Olsen, J.O.

    1995-01-01

    Amorphous and nanocrystalline phases have been formed by ball-milling Y-Ba-Cu-O and Bi-Ca-Sr-Cu-O. The strong mechanical deformations induce disorder on the oxygen sublattice and on the cation sites. These order-disorder transformations often produce simple cubic perovskite structures. During recrystallization, the chemical order is restored. Small ordered regions nucleate, grow and produce particular metastable configurations which minimize the total elastic strain energy. The sequence of events giving rise to the various metastable phases has been followed by x-ray diffraction and differential scanning calorimetry and is explained in terms of free energy diagrams. The stress and strain fields associated with the Y-Ba disorder are calculated using the elastic properties of the Y-Ba-Cu-O superconductor. A simple model is proposed to explain the stability of the structures observed after thermal treatments. (orig.)

  19. Para-equilibrium phase diagrams

    International Nuclear Information System (INIS)

    Pelton, Arthur D.; Koukkari, Pertti; Pajarre, Risto; Eriksson, Gunnar

    2014-01-01

    Highlights: • A rapidly cooled system may attain a state of para-equilibrium. • In this state rapidly diffusing elements reach equilibrium but others are immobile. • Application of the Phase Rule to para-equilibrium phase diagrams is discussed. • A general algorithm to calculate para-equilibrium phase diagrams is described. - Abstract: If an initially homogeneous system at high temperature is rapidly cooled, a temporary para-equilibrium state may result in which rapidly diffusing elements have reached equilibrium but more slowly diffusing elements have remained essentially immobile. The best known example occurs when homogeneous austenite is quenched. A para-equilibrium phase assemblage may be calculated thermodynamically by Gibbs free energy minimization under the constraint that the ratios of the slowly diffusing elements are the same in all phases. Several examples of calculated para-equilibrium phase diagram sections are presented and the application of the Phase Rule is discussed. Although the rules governing the geometry of these diagrams may appear at first to be somewhat different from those for full equilibrium phase diagrams, it is shown that in fact they obey exactly the same rules with the following provision. Since the molar ratios of non-diffusing elements are the same in all phases at para-equilibrium, these ratios act, as far as the geometry of the diagram is concerned, like “potential” variables (such as T, pressure or chemical potentials) rather than like “normal” composition variables which need not be the same in all phases. A general algorithm to calculate para-equilibrium phase diagrams is presented. In the limit, if a para-equilibrium calculation is performed under the constraint that no elements diffuse, then the resultant phase diagram shows the single phase with the minimum Gibbs free energy at any point on the diagram; such calculations are of interest in physical vapor deposition when deposition is so rapid that phase

  20. Formation of metastable phases in magnesium–titanium system by high-pressure torsion and their hydrogen storage performance

    International Nuclear Information System (INIS)

    Edalati, Kaveh; Emami, Hoda; Staykov, Aleksandar; Smith, David J.; Akiba, Etsuo; Horita, Zenji

    2015-01-01

    No binary phases exist in the Mg–Ti binary equilibrium phase diagram and the two elements are totally immiscible even in liquid form. This study shows that four metastable phases (two with the bcc and fcc structures and two with the hcp structures) are formed in the Mg–Ti system by severe plastic deformation (SPD) through the process of high-pressure torsion (HPT). Investigation of hydrogenation properties reveals that these metastable phases are decomposed to pure Mg and Ti during heating before they can absorb the hydrogen in the form of ternary Mg–Ti hydrides. First-principles calculations show that the hydrogenation reaction should occur thermodynamically, and ternary Mg–Ti hydrides with the cubic structure should form at low temperature. However, the slow kinetics for this reaction appears to be the limiting step. Calculations show that the binding energy of hydrogen increases and the thermodynamic stability of hydrides undesirably increases by addition of Ti to Mg

  1. Metastable phases freezing from melts of reciprocal systems PbX + CdI2=CdX + PbI2 (X=S, Se, Te)

    International Nuclear Information System (INIS)

    Odin, I.N.; Chukichev, M.V.

    2001-01-01

    The transformations in the mutual PbX + CdI 2 =CdX + PbI 2 (X=S, Se, Te) systems leading to the crystallization of metastable polytypical modifications of lead iodide in metastable ternary compounds are studied for the first time. Microstructural and X-ray diffraction analyses were conducted. Their phase diagrams were constructed. The luminescence properties of the stable and metastable modifications of the lead iodide and the metastable compound Pb 4 SeI 6 were investigated. The lines 504 and 512 nm are noted in the 2H-PbI 2 cathodoluminescence spectra. The close lines - 508 and 516 nm provide for the 6R-PbI 2 modification. The metastable compound Pb 4 SeI 6 is characterized by the 769 and 868 nm lines [ru

  2. First-principles interatomic potentials for transition-metal aluminides. III. Extension to ternary phase diagrams

    Science.gov (United States)

    Widom, Mike; Al-Lehyani, Ibrahim; Moriarty, John A.

    2000-08-01

    Modeling structural and mechanical properties of intermetallic compounds and alloys requires detailed knowledge of their interatomic interactions. The first two papers of this series [Phys. Rev. B 56, 7905 (1997); 58, 8967 (1998)] derived first-principles interatomic potentials for transition-metal (TM) aluminides using generalized pseudopotential theory (GPT). Those papers focused on binary alloys of aluminum with first-row transition metals and assessed the ability of GPT potentials to reproduce and elucidate the alloy phase diagrams of Al-Co and Al-Ni. This paper addresses the phase diagrams of the binary alloy Al-Cu and the ternary systems Al-Co-Cu and Al-Co-Ni, using GPT pair potentials calculated in the limit of vanishing transition-metal concentration. Despite this highly simplifying approximation, we find rough agreement with the known low-temperature phase diagrams, up to 50% total TM concentration provided the Co fraction is below 25%. Full composition-dependent potentials and many-body interactions would be required to correct deficiencies at higher Co concentration. Outside this troublesome region, the experimentally determined stable and metastable phases all lie on or near the convex hull of a scatter plot of energy versus composition. We verify, qualitatively, reported solubility ranges extending binary alloys into the ternary diagram in both Al-Co-Cu and Al-Co-Ni. Finally, we reproduce previously conjectured transition-metal positions in the decagonal quasicrystal phase.

  3. CERPHASE: Computer-generated phase diagrams

    International Nuclear Information System (INIS)

    Ruys, A.J.; Sorrell, C.C.; Scott, F.H.

    1990-01-01

    CERPHASE is a collection of computer programs written in the programming language basic and developed for the purpose of teaching the principles of phase diagram generation from the ideal solution model of thermodynamics. Two approaches are used in the generation of the phase diagrams: freezing point depression and minimization of the free energy of mixing. Binary and ternary phase diagrams can be generated as can diagrams containing the ideal solution parameters used to generate the actual phase diagrams. Since the diagrams generated utilize the ideal solution model, data input required from the operator is minimal: only the heat of fusion and melting point of each component. CERPHASE is menu-driven and user-friendly, containing simple instructions in the form of screen prompts as well as a HELP file to guide the operator. A second purpose of CERPHASE is in the prediction of phase diagrams in systems for which no experimentally determined phase diagrams are available, enabling the estimation of suitable firing or sintering temperatures for otherwise unknown systems. Since CERPHASE utilizes ideal solution theory, there are certain limitations imposed on the types of systems that can be predicted reliably. 6 refs., 13 refs

  4. 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.

  5. Phase diagram of the Ge-rich of the Ba–Ge system and characterisation of single-phase BaGe4

    International Nuclear Information System (INIS)

    Prokofieva, Violetta K.; Pavlova, Lydia M.

    2014-01-01

    Highlights: • The Ba-Ge phase diagram for the range 50–100 at.% Ge was constructed. • Single-phase BaGe 4 grown by the Czochralski method was characterised. • A phenomenological model for a liquid-liquid phase transition is proposed. - Abstract: The Ba–Ge binary system has been investigated by several authors, but some uncertainties remain regarding phases with Ba/Ge ⩽ 2. The goal of this work was to resolve the uncertainty about the current phase diagram of Ba–Ge by performing DTA, X-ray powder diffraction, metallographic and chemical analyses, and measurements of the electrical conductivity and viscosity. The experimental Ba–Ge phase diagram over the composition range of 50–100 at.% Ge was constructed from the cooling curves and single-phase BaGe 4 grown by the Czochralski crystal pulling method was characterised. Semiconducting BaGe 4 crystallised peritectically from the liquid phase near the eutectic. In the liquid state, the caloric effects were observed in the DTA curves at 1050 °C where there are no definite phase lines in the Ba–Ge phase diagram. These effects are confirmed by significant changes in the viscosity and electrical conductivity of a Ba–Ge alloy with eutectic composition at this temperature. A phenomenological model based on two different approaches, a phase approach and a chemical approach, is proposed to explain the isothermal liquid–liquid phase transition observed in the Ba–Ge system from the Ge side. Our results suggest that this transition is due to the peritectic reactions in the liquid phase. This reversible phase transition results in the formation of precursors of various metastable clathrate phases and is associated with sudden changes in the structure of Ba–Ge liquid alloys. Characteristics of both first- and second-order phase transitions are observed. Charge transfer appears to play an important role in this transition

  6. First-principles interatomic potentials for transition-metal aluminides. III. Extension to ternary phase diagrams

    International Nuclear Information System (INIS)

    Widom, Mike; Al-Lehyani, Ibrahim; Moriarty, John A.

    2000-01-01

    Modeling structural and mechanical properties of intermetallic compounds and alloys requires detailed knowledge of their interatomic interactions. The first two papers of this series [Phys. Rev. B 56, 7905 (1997); 58, 8967 (1998)] derived first-principles interatomic potentials for transition-metal (TM) aluminides using generalized pseudopotential theory (GPT). Those papers focused on binary alloys of aluminum with first-row transition metals and assessed the ability of GPT potentials to reproduce and elucidate the alloy phase diagrams of Al-Co and Al-Ni. This paper addresses the phase diagrams of the binary alloy Al-Cu and the ternary systems Al-Co-Cu and Al-Co-Ni, using GPT pair potentials calculated in the limit of vanishing transition-metal concentration. Despite this highly simplifying approximation, we find rough agreement with the known low-temperature phase diagrams, up to 50% total TM concentration provided the Co fraction is below 25%. Full composition-dependent potentials and many-body interactions would be required to correct deficiencies at higher Co concentration. Outside this troublesome region, the experimentally determined stable and metastable phases all lie on or near the convex hull of a scatter plot of energy versus composition. We verify, qualitatively, reported solubility ranges extending binary alloys into the ternary diagram in both Al-Co-Cu and Al-Co-Ni. Finally, we reproduce previously conjectured transition-metal positions in the decagonal quasicrystal phase. (c) 2000 The American Physical Society

  7. Metastability in spin polarised Fermi gases and quasiparticle decays

    DEFF Research Database (Denmark)

    Sadeghzadeh, Kayvan; Bruun, Georg; Lobo, Carlos

    2011-01-01

    We investigate the metastability associated with the first order transition from normal to superfluid phases in the phase diagram of two-component polarised Fermi gases.We begin by detailing the dominant decay processes of single quasiparticles.Having determined the momentum thresholds of each...... the interaction strength at which a polarised phase of molecules becomes the groundstate, to the one at which the single quasiparticle groundstate changes character from polaronic to molecular. Our argument in terms of a Fermi sea of polarons naturally suggests their use as an experimental probe. We propose...... experiments to observe the threshold of the predicted region of metastability, the interaction strength at which the quasiparticle groundstate changes character, and the decay rate of polarons....

  8. Phase transformation of metastable cubic γ-phase in U-Mo alloys

    International Nuclear Information System (INIS)

    Sinha, V.P.; Hegde, P.V.; Prasad, G.J.; Dey, G.K.; Kamath, H.S.

    2010-01-01

    Over the past decade considerable efforts have been put by many fuel designers to develop low enriched uranium (LEU 235 ) base U-Mo alloy as a potential fuel for core conversion of existing research and test reactors which are running on high enriched uranium (HEU > 85%U 235 ) fuel and also for the upcoming new reactors. U-Mo alloy with minimum 8 wt% molybdenum shows excellent metastability with cubic γ-phase in cast condition. However, it is important to characterize the decomposition behaviour of metastable cubic γ-uranium in its equilibrium products for in reactor fuel performance point of view. The present paper describes the phase transformation behaviour of cubic γ-uranium phase in U-Mo alloys with three different molybdenum compositions (i.e. 8 wt%, 9 wt% and 10 wt%). U-Mo alloys were prepared in an induction melting furnace and characterized by X-ray diffraction (XRD) method for phase determination. Microstructures were developed for samples in as cast condition. The alloys were hot rolled in cubic γ-phase to break the cast structure and then they were aged at 500 o C for 68 h and 240 h, so that metastable cubic γ-uranium will undergo eutectoid decomposition to form equilibrium phases of orthorhombic α-uranium and body centered tetragonal U 2 Mo intermetallic compound. U-Mo alloy samples with different ageing history were then characterized by XRD for phase and development of microstructure.

  9. Energy barriers between metastable states in first-order quantum phase transitions

    Science.gov (United States)

    Wald, Sascha; Timpanaro, André M.; Cormick, Cecilia; Landi, Gabriel T.

    2018-02-01

    A system of neutral atoms trapped in an optical lattice and dispersively coupled to the field of an optical cavity can realize a variation of the Bose-Hubbard model with infinite-range interactions. This model exhibits a first-order quantum phase transition between a Mott insulator and a charge density wave, with spontaneous symmetry breaking between even and odd sites, as was recently observed experimentally [Landig et al., Nature (London) 532, 476 (2016), 10.1038/nature17409]. In the present paper, we approach the analysis of this transition using a variational model which allows us to establish the notion of an energy barrier separating the two phases. Using a discrete WKB method, we then show that the local tunneling of atoms between adjacent sites lowers this energy barrier and hence facilitates the transition. Within our simplified description, we are thus able to augment the phase diagram of the model with information concerning the height of the barrier separating the metastable minima from the global minimum in each phase, which is an essential aspect for the understanding of the reconfiguration dynamics induced by a quench across a quantum critical point.

  10. 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.

  11. Phase diagrams of the elements

    International Nuclear Information System (INIS)

    Young, D.A.

    1975-01-01

    A summary of the pressure-temperature phase diagrams of the elements is presented, with graphs of the experimentally determined solid-solid phase boundaries and melting curves. Comments, including theoretical discussion, are provided for each diagram. The crystal structure of each solid phase is identified and discussed. This work is aimed at encouraging further experimental and theoretical research on phase transitions in the elements

  12. Glass and liquid phase diagram of a polyamorphic monatomic system

    Science.gov (United States)

    Reisman, Shaina; Giovambattista, Nicolas

    2013-02-01

    We perform out-of-equilibrium molecular dynamics (MD) simulations of a monatomic system with Fermi-Jagla (FJ) pair potential interactions. This model system exhibits polyamorphism both in the liquid and glass state. The two liquids, low-density (LDL) and high-density liquid (HDL), are accessible in equilibrium MD simulations and can form two glasses, low-density (LDA) and high-density amorphous (HDA) solid, upon isobaric cooling. The FJ model exhibits many of the anomalous properties observed in water and other polyamorphic liquids and thus, it is an excellent model system to explore qualitatively the thermodynamic properties of such substances. The liquid phase behavior of the FJ model system has been previously characterized. In this work, we focus on the glass behavior of the FJ system. Specifically, we perform systematic isothermal compression and decompression simulations of LDA and HDA at different temperatures and determine "phase diagrams" for the glass state; these phase diagrams varying with the compression/decompression rate used. We obtain the LDA-to-HDA and HDA-to-LDA transition pressure loci, PLDA-HDA(T) and PHDA-LDA(T), respectively. In addition, the compression-induced amorphization line, at which the low-pressure crystal (LPC) transforms to HDA, PLPC-HDA(T), is determined. As originally proposed by Poole et al. [Phys. Rev. E 48, 4605 (1993)], 10.1103/PhysRevE.48.4605 simulations suggest that the PLDA-HDA(T) and PHDA-LDA(T) loci are extensions of the LDL-to-HDL and HDL-to-LDL spinodal lines into the glass domain. Interestingly, our simulations indicate that the PLPC-HDA(T) locus is an extension, into the glass domain, of the LPC metastability limit relative to the liquid. We discuss the effects of compression/decompression rates on the behavior of the PLDA-HDA(T), PHDA-LDA(T), PLPC-HDA(T) loci. The competition between glass polyamorphism and crystallization is also addressed. At our "fast rate," crystallization can be partially suppressed and the

  13. Cooperative photoinduced metastable phase control in strained manganite films

    Science.gov (United States)

    Zhang, Jingdi; Tan, Xuelian; Liu, Mengkun; Teitelbaum, S. W.; Post, K. W.; Jin, Feng; Nelson, K. A.; Basov, D. N.; Wu, Wenbin; Averitt, R. D.

    2016-09-01

    A major challenge in condensed-matter physics is active control of quantum phases. Dynamic control with pulsed electromagnetic fields can overcome energetic barriers, enabling access to transient or metastable states that are not thermally accessible. Here we demonstrate strain-engineered tuning of La2/3Ca1/3MnO3 into an emergent charge-ordered insulating phase with extreme photo-susceptibility, where even a single optical pulse can initiate a transition to a long-lived metastable hidden metallic phase. Comprehensive single-shot pulsed excitation measurements demonstrate that the transition is cooperative and ultrafast, requiring a critical absorbed photon density to activate local charge excitations that mediate magnetic-lattice coupling that, in turn, stabilize the metallic phase. These results reveal that strain engineering can tune emergent functionality towards proximal macroscopic states to enable dynamic ultrafast optical phase switching and control.

  14. Ring diagrams and phase transitions

    International Nuclear Information System (INIS)

    Takahashi, K.

    1986-01-01

    Ring diagrams at finite temperatures carry most infrared-singular parts among Feynman diagrams. Their effect to effective potentials are in general so significant that one must incorporate them as well as 1-loop diagrams. The author expresses these circumstances in some examples of supercooled phase transitions

  15. Stable and metastable phases in reciprocal systems PbSe + Ag2I2 Ag2Se + PbI2 and PbSe + CdI2 = CdSe + PbI2

    International Nuclear Information System (INIS)

    Odin, I.N.; Grin'ko, V.V.; Kozlovskij, V.F.; Safronov, E.V.

    2005-01-01

    Mutual system PbSe + Ag 2 I 2 = Ag 2 Se + PbI 2 is investigated. It is shown that diagonal Ag 2 Se-PbI 2 is stable. Liquidus surface and isothermal section at 633 K of phase diagram of PbSe-Ag 2 Se-PbI 2 system are built. Transformations directing to crystallization metastable ternary compound forming in PbSe-PbI 2 system and metastable polytype modifications of lead iodide in PbSe-Ag 2 Se-PbI 2 system at 620-685 K are studied. By hardening from molten state (1150-1220 K) new interstitial metastable phases crystallizing in CdCl 2 structural type are obtained in PbSe-Ag 2 Se-PbI 2 and PbSe + CdI 2 = CdSe + PbI 2 systems [ru

  16. Stable and metastable equilibria in PbSe + SnI2=SnSe + PbI2

    International Nuclear Information System (INIS)

    Odin, I.N.; Grin'ko, V.V.; Kozlovskij, V.F.; Demidova, E.D.

    2003-01-01

    T-x-y phase diagrams of the PbSe + SnI 2 =SnSe + PbI 2 mutual system (stable states) are plotted for the first time. It is shown that melt, solid solutions on the base of components of the mutual system and phase on the base of Sn 2 SeI 4 take part in phase equilibria. Transformations in the PbSe + SnI 2 =SnSe + PbI 2 mutual system leading to crystallization of metastable polytype modifications of lead iodides and metastable ternary compound forming in PbSe-PbI 2 system are investigated for the first time [ru

  17. Entropy-driven metastable defects in silicon

    International Nuclear Information System (INIS)

    Hamilton, B.; Peaker, A.R.; Pantelides, S.T.

    1989-01-01

    The known metastable defects are usually describable by a configuration coordinate diagram in which two energy minima are separated by a barrier. This diagram does not change with temperature and each configuration is stable over some temperature range. Here we report the observation of a novel metastability: A configuration change occurs spontaneously and abruptly at a critical temperature, giving rise to a discontinuous DLTS (deep level transient spectroscopy) spectrum. We propose that this phenomenon is a manifestation of entropy variations in the configurational space. (author) 12 refs., 4 figs

  18. Common phase diagram for low-dimensional superconductors

    International Nuclear Information System (INIS)

    Michalak, Rudi

    2003-01-01

    A phenomenological phase diagram which has been derived for high-temperature superconductors from NMR Knight-shift measurements of the pseudogap is compared to the phase diagram that is obtained for organic superconductors and spin-ladder superconductors, both low-dimensional systems. This is contrasted to the phase diagram of some Heavy Fermion superconductors, i.e. superconductors not constrained to a low dimensionality

  19. Growth kinetics of metastable (331) nanofacet on Au and Pt(110) surfaces

    International Nuclear Information System (INIS)

    Ndongmouo, U.T.; Houngninou, E.; Hontinfinde, F.

    2006-12-01

    A theoretical epitaxial growth model with realistic barriers for surface diffusion is investigated by means of kinetic Monte Carlo simulations to study the growth modes of metastable (331) nanofacets on Au and Pt(110) surfaces. The results show that under experimental atomic fluxes, the (331) nanofacets grow by 2D nucleation at low temperature in the submonolayer regime. A metastable growth phase diagram that can be useful to experimentalists is presented and looks similar to the one found for the stationary growth of the bcc(001) surface in the kinetic 6-vertex model. (author)

  20. Phase diagram of classical electronic bilayers

    International Nuclear Information System (INIS)

    Ranganathan, S; Johnson, R E

    2006-01-01

    Extensive molecular dynamics calculations have been performed on classical, symmetric electronic bilayers at various values of the coupling strength Γ and interlayer separation d to delineate its phase diagram in the Γ-d plane. We studied the diffusion, the amplitude of the main peak of the intralayer static structure factor and the peak positions of the intralayer pair correlation function with the aim of defining equivalent signatures of freezing and constructing the resulting phase diagram. It is found that for Γ greater than 75, crystalline structures exist for a certain range of interlayer separations, while liquid phases are favoured at smaller and larger d. It is seen that there is good agreement between our phase diagram and previously published ones

  1. Phase diagram of classical electronic bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Ranganathan, S [Department of Physics, Royal Military College of Canada, Kingston, Ontario K7K 7B4 (Canada); Johnson, R E [Department of Mathematics and Computer Science, Royal Military College of Canada, Kingston, Ontario K7K 7B4 (Canada)

    2006-04-28

    Extensive molecular dynamics calculations have been performed on classical, symmetric electronic bilayers at various values of the coupling strength {gamma} and interlayer separation d to delineate its phase diagram in the {gamma}-d plane. We studied the diffusion, the amplitude of the main peak of the intralayer static structure factor and the peak positions of the intralayer pair correlation function with the aim of defining equivalent signatures of freezing and constructing the resulting phase diagram. It is found that for {gamma} greater than 75, crystalline structures exist for a certain range of interlayer separations, while liquid phases are favoured at smaller and larger d. It is seen that there is good agreement between our phase diagram and previously published ones.

  2. Lattice and Phase Diagram in QCD

    International Nuclear Information System (INIS)

    Lombardo, Maria Paola

    2008-01-01

    Model calculations have produced a number of very interesting expectations for the QCD Phase Diagram, and the task of a lattice calculations is to put these studies on a quantitative grounds. I will give an overview of the current status of the lattice analysis of the QCD phase diagram, from the quantitative results of mature calculations at zero and small baryochemical potential, to the exploratory studies of the colder, denser phase.

  3. Phase transition in metastable perovskite Pb(AlNb)0,5O3

    International Nuclear Information System (INIS)

    Zhabko, T.E.; Olekhnovich, N.M.; Shilin, A.D.

    1987-01-01

    Dielectric properties of metastable perovskite Pb(AlNb) 0.5 O 3 and X-ray temperature investigations of both perovskite and pyrochlore modifications of the given compound are studied. Samples with the perovskite structure are prepared from the pyrochlorephase at 4-5 GPa pressure and 1170-1270 K. Ferroelectric phase transition is shown to occur in the metastable perovskite phase Pb(AlNb) 0.5 O 3 at 170 K

  4. The binary (solid + liquid) phase diagrams of (caprylic or capric acid) + (1-octanol or 1-decanol)

    International Nuclear Information System (INIS)

    Carareto, Natália D.D.; Castagnaro, Thamires; Costa, Mariana C.; Meirelles, Antonio J.A.

    2014-01-01

    Highlights: • SLE of mixtures of caprylic acid, (capric acid + 1-octanol), 1-decanol were studied. • Experimental data were obtained through DSC and Stepscan DSC. • Systems presented eutectic and peritectic points. • Liquidus line was modeled using Margules and NRTL models. • Solid phase was modeled using the Slaughter and Doherty approach. - Abstract: In the present study the phase diagrams of four (fatty acid + fatty alcohol) binary mixtures composed of caprylic (C8O2) or capric acid (C10O2) + 1-octanol (C8OH) or 1-decanol (C10OH) were obtained by differential scanning calorimetry (DSC). Eutectic and peritectic reactions occurred in the systems. In standard DSC analyses of the (C8O2 + C10OH) and (C10O2 + C8OH) systems, an exothermic transition occurs in association with the melting of a metastable phase. A Stepscan DSC method was used in order to avoid the formation of this metastable phase during the heating of the mixtures. The approach suggested by Slaughter and Doherty (1995) [24] was used for modeling the solid phase, and the Margules 2-suffix, Margules 3-suffix and NRTL models were applied for calculating the activity coefficients of the liquid phase. The best modeling results were obtained using the Margules-3-suffix with an average deviation between experimental and calculated values ranging from T = (0.3 to 0.9) K

  5. A new approach to establish both stable and metastable phase equilibria for fcc ordered/disordered phase transition: application to the Al–Ni and Ni–Si systems

    International Nuclear Information System (INIS)

    Yuan Xiaoming; Zhang Lijun; Du Yong; Xiong Wei; Tang Ying; Wang Aijun; Liu Shuhong

    2012-01-01

    Both two-sublattice (2SL) and four-sublattice (4SL) models in the framework of the compound energy formalism can be used to describe the fcc ordered/disordered transitions. When transferring the parameters of 2SL disregarding the metastable ordered states into those of 4SL, inconsistence in either stable or metastable phase diagrams could appear, as detected in both Al–Ni and Ni–Si systems. To avoid such a kind of drawback, this behavior was analyzed and investigated in the Ni–Si and Al–Ni systems with the aid of first–principle calculations. Furthermore, a new approach considering both the stable and metastable fcc ordered phase equilibria deduced from the first–principles calculations was proposed to perform a reliable thermodynamic modeling for the fcc ordered/disordered transition. The Ni–Si system was then thermodynamically assessed using the presently proposed approach. The good agreement between the calculation and experiments demonstrates the reliability of the proposed approach. It is expected that the approach is valid for other systems showing complex ordered/disordered transitions. - Highlights: ► We discuss the drawbacks of order/disorder modeling in the Ni–Si and Al–Ni systems. ► We perform ab initio calculation of thermodynamic properties in the Ni–Si system. ► A CALPHAD–type approach is proposed to model the fcc ordered/disordered transition. ► The Ni–Si system was thermodynamically assessed using the new approach.

  6. 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.

  7. Estimated D2--DT--T2 phase diagram in the three-phase region

    International Nuclear Information System (INIS)

    Souers, P.C.; Hickman, R.G.; Tsugawa, R.T.

    1976-01-01

    A composite of experimental eH 2 -D 2 phase-diagram data at the three-phase line is assembled from the literature. The phase diagram is a smooth cigar shape without a eutectic point, indicating complete miscibility of liquid and solid phases. Additional data is used to estimate the D 2 -T 2 , D 2 DT, and DT-T 2 binary phase diagrams. These are assembled into the ternary D 2 -DT-T 2 phase diagram. A surface representing the chemical equilibrium of the three species is added to the phase diagram. At chemical equilibrium, it is estimated that 50-50 liquid D-T at 19.7 0 K is in equilibrium with 42 mole percent T vapor and 54 percent T solid. Infrared spectroscopy is suggested as a means of component analysis of liquid and solid mixtures

  8. Phase diagram of an extended Agassi model

    Science.gov (United States)

    García-Ramos, J. E.; Dukelsky, J.; Pérez-Fernández, P.; Arias, J. M.

    2018-05-01

    Background: The Agassi model [D. Agassi, Nucl. Phys. A 116, 49 (1968), 10.1016/0375-9474(68)90482-X] is an extension of the Lipkin-Meshkov-Glick (LMG) model [H. J. Lipkin, N. Meshkov, and A. J. Glick, Nucl. Phys. 62, 188 (1965), 10.1016/0029-5582(65)90862-X] that incorporates the pairing interaction. It is a schematic model that describes the interplay between particle-hole and pair correlations. It was proposed in the 1960s by D. Agassi as a model to simulate the properties of the quadrupole plus pairing model. Purpose: The aim of this work is to extend a previous study by Davis and Heiss [J. Phys. G: Nucl. Phys. 12, 805 (1986), 10.1088/0305-4616/12/9/006] generalizing the Agassi model and analyze in detail the phase diagram of the model as well as the different regions with coexistence of several phases. Method: We solve the model Hamiltonian through the Hartree-Fock-Bogoliubov (HFB) approximation, introducing two variational parameters that play the role of order parameters. We also compare the HFB calculations with the exact ones. Results: We obtain the phase diagram of the model and classify the order of the different quantum phase transitions appearing in the diagram. The phase diagram presents broad regions where several phases, up to three, coexist. Moreover, there is also a line and a point where four and five phases are degenerated, respectively. Conclusions: The phase diagram of the extended Agassi model presents a rich variety of phases. Phase coexistence is present in extended areas of the parameter space. The model could be an important tool for benchmarking novel many-body approximations.

  9. Ferroelectric Phase Diagram of PVDF:PMMA

    OpenAIRE

    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 were made by melting, ice quenching, and subsequent annealing above the glass transition temperature of PMMA, close to the melting temperature of PVDF. Addition of PMMA suppresses the crystallizatio...

  10. Novel criterion for formation of metastable phase from undercooled melt

    International Nuclear Information System (INIS)

    Kuribayashi, Kazuhiko; Nagashio, Kosuke; Niwata, Kenji; Kumar, M.S. Vijaya; Hibiya, Taketoshi

    2007-01-01

    Undercooling a melt facilitates the preferential nucleation of a metastable phase. In the present study, the formation of metastable phases from undercooled melts was considered from the viewpoint of the competitive nucleation criterion. The classical nucleation theory shows us that the most critical factor for forming a critical nucleus is the interface free energy σ. Furthermore, Spaepen's negentropic model on σ generated the role of the scaling factor α that depends on the polyhedral order in the liquid and solid phases prominent in simple liquids such as the melt of monoatomic metals. In ionic materials such as oxides, however, in which oxygen polyhedrons including a cation at their center are the structural units both in the solid and liquid phases, the entropy of fusion, rather than α, can be expected to become dominant in the determination of σ. In accordance with this idea, using REFeO 3 as the model material (where RE denotes rare-earth elements) the entropy-undercooling regime criterion was proposed and verified

  11. Phase diagram of spiking neural networks.

    Science.gov (United States)

    Seyed-Allaei, Hamed

    2015-01-01

    In computer simulations of spiking neural networks, often it is assumed that every two neurons of the network are connected by a probability of 2%, 20% of neurons are inhibitory and 80% are excitatory. These common values are based on experiments, observations, and trials and errors, but here, I take a different perspective, inspired by evolution, I systematically simulate many networks, each with a different set of parameters, and then I try to figure out what makes the common values desirable. I stimulate networks with pulses and then measure their: dynamic range, dominant frequency of population activities, total duration of activities, maximum rate of population and the occurrence time of maximum rate. The results are organized in phase diagram. This phase diagram gives an insight into the space of parameters - excitatory to inhibitory ratio, sparseness of connections and synaptic weights. This phase diagram can be used to decide the parameters of a model. The phase diagrams show that networks which are configured according to the common values, have a good dynamic range in response to an impulse and their dynamic range is robust in respect to synaptic weights, and for some synaptic weights they oscillates in α or β frequencies, independent of external stimuli.

  12. 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.

  13. A Three-dimensional Topological Model of Ternary Phase Diagram

    International Nuclear Information System (INIS)

    Mu, Yingxue; Bao, Hong

    2017-01-01

    In order to obtain a visualization of the complex internal structure of ternary phase diagram, the paper realized a three-dimensional topology model of ternary phase diagram with the designed data structure and improved algorithm, under the guidance of relevant theories of computer graphics. The purpose of the model is mainly to analyze the relationship between each phase region of a ternary phase diagram. The model not only obtain isothermal section graph at any temperature, but also extract a particular phase region in which users are interested. (paper)

  14. Understanding metastable phase transformation during crystallization of RDX, HMX and CL-20: experimental and DFT studies.

    Science.gov (United States)

    Ghosh, Mrinal; Banerjee, Shaibal; Shafeeuulla Khan, Md Abdul; Sikder, Nirmala; Sikder, Arun Kanti

    2016-09-14

    Multiphase growth during crystallization severely affects deliverable output of explosive materials. Appearance and incomplete transformation of metastable phases are a major source of polymorphic impurities. This article presents a methodical and molecular level understanding of the metastable phase transformation mechanism during crystallization of cyclic nitramine explosives, viz. RDX, HMX and CL-20. Instantaneous reverse precipitation yielded metastable γ-HMX and β-CL-20 which undergo solution mediated transformation to the respective thermodynamic forms, β-HMX and ε-CL-20, following 'Ostwald's rule of stages'. However, no metastable phase, anticipated as β-RDX, was evidenced during precipitation of RDX, which rather directly yielded the thermodynamically stable α-phase. The γ→β-HMX and β→ε-CL-20 transformations took 20 and 60 minutes respectively, whereas formation of α-RDX was instantaneous. Density functional calculations were employed to identify the possible transition state conformations and to obtain activation barriers for transformations at wB97XD/6-311++G(d,p)(IEFPCM)//B3LYP/6-311G(d,p) level of theory. The computed activation barriers and lattice energies responsible for transformation of RDX, HMX and CL-20 metastable phases to thermodynamic ones conspicuously supported the experimentally observed order of phase stability. This precise result facilitated an understanding of the occurrence of a relatively more sensitive and less dense β-CL-20 phase in TNT based melt-cast explosive compositions, a persistent and critical problem unanswered in the literature. The crystalline material recovered from such compositions revealed a mixture of β- and ε-CL-20. However, similar compositions of RDX and HMX never showed any metastable phase. The relatively long stability with the highest activation barrier is believed to restrict complete β→ε-CL-20 transformation during processing. Therefore a method is suggested to overcome this issue.

  15. Metastable equilibrium for the quaternary system containing with lithium+potassium+magnesium+chloride in aqueous solution at 323K

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Xudong; Yin, Qinghong; Jiang, Dongbo; Zeng, Ying [Chengdu University of Technology, Chengdu (China)

    2014-06-15

    The metastable equilibrium of the system contained with lithium, potassium, magnesium, and chloride in aqueous system was investigated at 323 K using an isothermal evaporation method. The isothermal experimental data and physicochemical properties, such as density and refractive index of the equilibrated solution, were determined. With the experimental results, the stereo phase diagram, the projected phase diagram, the water content diagram and the physicochemical properties versus composition diagrams were constructed. The projected phase diagram consists of three invariant points, seven univariant curves and five crystallization fields corresponding to single salts potassium chloride (KCl), lithium chloride monohydrate (LiCl·H{sub 2}O), bischofite (MgCl{sub 2}·6H{sub 2}O) and two double salts lithium carnallite (LiCl·MgCl{sub 2}·7H{sub 2}O) and potassium carnallite (KCl·MgCl{sub 2}·6H{sub 2}O). Salt KCl has the largest crystallization region; it contains almost 95% of the general crystallization field.

  16. Planktic foraminifera form their shells via metastable carbonate phases.

    Science.gov (United States)

    Jacob, D E; Wirth, R; Agbaje, O B A; Branson, O; Eggins, S M

    2017-11-02

    The calcium carbonate shells of planktic foraminifera provide our most valuable geochemical archive of ocean surface conditions and climate spanning the last 100 million years, and play an important role in the ocean carbon cycle. These shells are preserved in marine sediments as calcite, the stable polymorph of calcium carbonate. Here, we show that shells of living planktic foraminifers Orbulina universa and Neogloboquadrina dutertrei originally form from the unstable calcium carbonate polymorph vaterite, implying a non-classical crystallisation pathway involving metastable phases that transform ultimately to calcite. The current understanding of how planktic foraminifer shells record climate, and how they will fare in a future high-CO 2 world is underpinned by analogy to the precipitation and dissolution of inorganic calcite. Our findings require a re-evaluation of this paradigm to consider the formation and transformation of metastable phases, which could exert an influence on the geochemistry and solubility of the biomineral calcite.

  17. Thermochemical and phase diagram studies of the Sn-Zn-Ni system

    International Nuclear Information System (INIS)

    Gandova, V.D.; Broz, P.; Bursik, J.; Vassilev, G.P.

    2011-01-01

    Highlights: → Sn-Zn-Ni phase diagram in the vicinity of the Sn-Zn system. → Unidentified compositions (UX1-UX4) are repeatedly observed. → This indicates up to 6 ternary compounds in the system. → A ternary eutectic reaction at around 190 o C is found. - Abstract: The phase diagram Sn-Zn-Ni was studied by means of DSC and electron microprobe analysis. The samples were positioned in three isopleth sections with nickel contents of 0.04 (section 1), 0.08 (section 2) and 0.12 (section 3) mole fractions. The mole fractions of Sn corresponding to the particular sections were as follows: from 0.230 to 0.768 (section 1), from 0.230 to 0.736 (section 2); from 0.220 to 0.704 (section 3). Mixtures of pure metals were sealed under vacuum in quartz ampoules and annealed at 350 o C. The solid phases identified in the samples were: γ-(i.e. Ni 5 Zn 21 ), (Zn) and the ternary phase T1. Unidentified compositions were observed. One of them: UX1 (X Ni = 0.071 ± 0.005, X Sn = 0.439 ± 0.009 and X Zn = 0.490 ± 0.010) might indicate another (stable or metastable) ternary compound (T3) in the system Sn-Zn-Ni. Considering the data obtained by combining DSC with microstructure observations, the studied alloys could be divided in two groups (A and B). A ternary eutectic reaction at around 190 o C is common for the A-group alloys. The phases taking part in this reaction are, probably, Ni 5 Zn 21 , (Zn), (βSn) and liquid. B-group samples do not show ternary eutectic reaction and are also characterized by the presence of the ternary compound T1 (absent in the A-group alloys). Four other groups of thermal arrests were registered (TA 1 -TA 4 ). It was found that TA 2 peaks were characteristic for most of the A-group samples, while TA 1 peaks were registered with all B-group samples.

  18. Omega phase in materials

    International Nuclear Information System (INIS)

    Sikka, S.K.; Vohra, Y.K.; Chidambaram, R.

    1982-01-01

    The subject is covered in sections, entitled: introduction; occurrence and some systematics of omega phase (omega phase in Ti, Zr and Hf under high pressures; omega phase in Group IV transition metal alloys; omega in other systems; omega embryos at high temperatures); crystallography (omega structure; relationship of ω-structure to bcc (β) and hcp (α) structures); physical properties; kinetics of formation, synthesis and metastability of omega phase (kinetics of α-ω transformation under high pressures; kinetics of β-ω transformation; synthesis and metastability studies); electronic structure of omega phase (electronic structure models; band structure calculations; theoretical results and experimental studies); electronic basis for omega phase stability (unified phase diagram; stability of omega phase); omega phase formation under combined thermal and pressure treatment in alloys (Ti-V alloys under pressure - a prototype case study; P-X phase diagrams for alloys; transformation mechanisms and models for diffuse omega phase (is omega structure a charge density distortion of the bcc phase; nature of incommensurate ω-structure and models for diffuse scattering); conclusion. (U.K.)

  19. Random matrix models for phase diagrams

    International Nuclear Information System (INIS)

    Vanderheyden, B; Jackson, A D

    2011-01-01

    We describe a random matrix approach that can provide generic and readily soluble mean-field descriptions of the phase diagram for a variety of systems ranging from quantum chromodynamics to high-T c materials. Instead of working from specific models, phase diagrams are constructed by averaging over the ensemble of theories that possesses the relevant symmetries of the problem. Although approximate in nature, this approach has a number of advantages. First, it can be useful in distinguishing generic features from model-dependent details. Second, it can help in understanding the 'minimal' number of symmetry constraints required to reproduce specific phase structures. Third, the robustness of predictions can be checked with respect to variations in the detailed description of the interactions. Finally, near critical points, random matrix models bear strong similarities to Ginsburg-Landau theories with the advantage of additional constraints inherited from the symmetries of the underlying interaction. These constraints can be helpful in ruling out certain topologies in the phase diagram. In this Key Issues Review, we illustrate the basic structure of random matrix models, discuss their strengths and weaknesses, and consider the kinds of system to which they can be applied.

  20. Calculation of Fe–B–V ternary phase diagram

    International Nuclear Information System (INIS)

    Homolová, Viera; Kroupa, Aleš; Výrostková, Anna

    2012-01-01

    Highlights: ► Phase diagram of Fe–B–V system was modelled by CALPHAD method. ► Database for thermodynamic calculations for Fe–B–V system was created. ► The new ternary phase was found in 67Fe–18B–15V [in at.%] alloy. - Abstract: The phase equilibria of the Fe–B–V ternary system are studied experimentally and theoretically in this paper. Phase diagram of the system was modelled by CALPHAD method. Boron was modelled as an interstitial element in the FCC and BCC solid solutions. The calculations of isothermal sections of phase diagram are compared with our experimental results at 903 and 1353 K and with available literature experimental data. New ternary phase (with chemical composition 28Fe32V40B in at.%) was found in 67Fe–18B–15V alloy [in at.%]. Further experimental studies for the determination of exact nature of the ternary phase including crystallographic information are necessary.

  1. Phase diagrams of diluted transverse Ising nanowire

    International Nuclear Information System (INIS)

    Bouhou, S.; Essaoudi, I.; Ainane, A.; Saber, M.; Ahuja, R.; Dujardin, F.

    2013-01-01

    In this paper, the phase diagrams of diluted Ising nanowire consisting of core and surface shell coupling by J 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

  2. Phase diagram of the disordered Bose-Hubbard model

    International Nuclear Information System (INIS)

    Gurarie, V.; Pollet, L.; Prokof'ev, N. V.; Svistunov, B. V.; Troyer, M.

    2009-01-01

    We establish the phase diagram of the disordered three-dimensional Bose-Hubbard model at unity filling which has been controversial for many years. The theorem of inclusions, proven by Pollet et al. [Phys. Rev. Lett. 103, 140402 (2009)] states that the Bose-glass phase always intervenes between the Mott insulating and superfluid phases. Here, we note that assumptions on which the theorem is based exclude phase transitions between gapped (Mott insulator) and gapless phases (Bose glass). The apparent paradox is resolved through a unique mechanism: such transitions have to be of the Griffiths type when the vanishing of the gap at the critical point is due to a zero concentration of rare regions where extreme fluctuations of disorder mimic a regular gapless system. An exactly solvable random transverse field Ising model in one dimension is used to illustrate the point. A highly nontrivial overall shape of the phase diagram is revealed with the worm algorithm. The phase diagram features a long superfluid finger at strong disorder and on-site interaction. Moreover, bosonic superfluidity is extremely robust against disorder in a broad range of interaction parameters; it persists in random potentials nearly 50 (!) times larger than the particle half-bandwidth. Finally, we comment on the feasibility of obtaining this phase diagram in cold-atom experiments, which work with trapped systems at finite temperature.

  3. 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.

  4. 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.

  5. Magnetic Phase Diagram of α-RuCl3

    Science.gov (United States)

    Sears, Jennifer; Kim, Young-June; Zhao, Yang; Lynn, Jeffrey

    The layered honeycomb material α-RuCl3 is thought to possess unusual magnetic interactions including a strong bond-dependent Kitaev term, offering a potential opportunity to study a material near a well understood spin liquid phase. Although this material orders magnetically at low temperatures and is thus not a realization of a Kitaev spin liquid, it does show a broad continuum of magnetic excitations reminiscent of that expected for the spin liquid phase. It has also been proposed that a magnetic field could destabilize the magnetic order in this material and induce a transition into a spin liquid phase. Low temperature magnetization and specific heat measurements in this material have suggested a complex magnetic phase diagram with multiple unidentified magnetic phases present at low temperature. This has provided motivation for our work characterizing the magnetic transitions and phase diagram in α-RuCl3. I will present detailed bulk measurements combined with magnetic neutron diffraction measurements to map out the phase diagram and identify the various phases present.

  6. Solid gas reaction phase diagram under high gas pressure

    International Nuclear Information System (INIS)

    Ishizaki, K.

    1992-01-01

    This paper reports that to evaluate which are the stable phases under high gas pressure conditions, a solid-gas reaction phase diagram under high gas pressure (HIP phase diagram) has been proposed by the author. The variables of the diagram are temperature, reactant gas partial pressure and total gas pressure. Up to the present time the diagrams have been constructed using isobaric conditions. In this work, the stable phases for a real HIP process were evaluated assuming an isochoric condition. To understand the effect of the total gas pressure on stability is of primary importance. Two possibilities were considered and evaluated, those are: the total gas pressure acts as an independent variable, or it only affects the fugacity values. The results of this work indicate that the total gas pressure acts as an independent variable, and in turn also affects the fugacity values

  7. 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.

  8. Metastable phases in Zr-Excel alloy and their stability under heavy ion (Kr{sup 2+}) irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Hongbing, E-mail: 12hy1@queensu.ca [Department of Mechanical and Materials Engineering, Queen' s University, Kingston, ON, K7L 3N6 (Canada); Zhang, Ken; Yao, Zhongwen [Department of Mechanical and Materials Engineering, Queen' s University, Kingston, ON, K7L 3N6 (Canada); Kirk, Mark A. [Material Science Division Argonne National Laboratory, Argonne, IL, 60439 (United States); Long, Fei; Daymond, Mark R. [Department of Mechanical and Materials Engineering, Queen' s University, Kingston, ON, K7L 3N6 (Canada)

    2016-02-15

    Zr-Excel alloy (Zr-3.5Sn-0.8Nb-0.8Mo, wt.%) has been proposed as a candidate material of pressure tubes in the CANDU-SCWR design. It is a dual-phase alloy containing primary hcp α-Zr and metastable bcc β-Zr. Metastable hexagonal ω-Zr phase could form in β-Zr as a result of aging during the processing of the tube. A synchrotron X-ray study was employed to study the lattice properties of the metastable phases in as-received Zr-Excel pressure tube material. In situ heavy ion (1 MeV Kr{sup 2+}) irradiations were carried out at 200 °C and 450 °C to emulate the stability of the metastable phase under a reactor environment. Quantitative Chemi-STEM EDS analysis was conducted on both un-irradiated and irradiated samples to investigate alloying element redistribution induced by heavy ion irradiation. It was found that no decomposition of β-Zr was observed under irradiation at both 200 °C and 450 °C. However, ω-Zr particles experienced shape changes and shrinkage associated with enrichment of Fe at the β/ω interface during 200 °C irradiation but not at 450 °C. There is a noticeable increase in the level of Fe in the α matrix after irradiation at both 200 °C and 450 °C. The concentrations of Nb, Mo and Fe are increased in the ω phase but decreased in the β phase at 200 °C. The stability of metastable phases under heavy ion irradiation associated with elemental redistribution is discussed.

  9. 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

  10. Unified Phase Diagram for Iron-Based Superconductors.

    Science.gov (United States)

    Gu, Yanhong; Liu, Zhaoyu; Xie, Tao; Zhang, Wenliang; Gong, Dongliang; Hu, Ding; Ma, Xiaoyan; Li, Chunhong; Zhao, Lingxiao; Lin, Lifang; Xu, Zhuang; Tan, Guotai; Chen, Genfu; Meng, Zi Yang; Yang, Yi-Feng; Luo, Huiqian; Li, Shiliang

    2017-10-13

    High-temperature superconductivity is closely adjacent to a long-range antiferromagnet, which is called a parent compound. In cuprates, all parent compounds are alike and carrier doping leads to superconductivity, so a unified phase diagram can be drawn. However, the properties of parent compounds for iron-based superconductors show significant diversity and both carrier and isovalent dopings can cause superconductivity, which casts doubt on the idea that there exists a unified phase diagram for them. Here we show that the ordered moments in a variety of iron pnictides are inversely proportional to the effective Curie constants of their nematic susceptibility. This unexpected scaling behavior suggests that the magnetic ground states of iron pnictides can be achieved by tuning the strength of nematic fluctuations. Therefore, a unified phase diagram can be established where superconductivity emerges from a hypothetical parent compound with a large ordered moment but weak nematic fluctuations, which suggests that iron-based superconductors are strongly correlated electron systems.

  11. Unified Phase Diagram for Iron-Based Superconductors

    Science.gov (United States)

    Gu, Yanhong; Liu, Zhaoyu; Xie, Tao; Zhang, Wenliang; Gong, Dongliang; Hu, Ding; Ma, Xiaoyan; Li, Chunhong; Zhao, Lingxiao; Lin, Lifang; Xu, Zhuang; Tan, Guotai; Chen, Genfu; Meng, Zi Yang; Yang, Yi-feng; Luo, Huiqian; Li, Shiliang

    2017-10-01

    High-temperature superconductivity is closely adjacent to a long-range antiferromagnet, which is called a parent compound. In cuprates, all parent compounds are alike and carrier doping leads to superconductivity, so a unified phase diagram can be drawn. However, the properties of parent compounds for iron-based superconductors show significant diversity and both carrier and isovalent dopings can cause superconductivity, which casts doubt on the idea that there exists a unified phase diagram for them. Here we show that the ordered moments in a variety of iron pnictides are inversely proportional to the effective Curie constants of their nematic susceptibility. This unexpected scaling behavior suggests that the magnetic ground states of iron pnictides can be achieved by tuning the strength of nematic fluctuations. Therefore, a unified phase diagram can be established where superconductivity emerges from a hypothetical parent compound with a large ordered moment but weak nematic fluctuations, which suggests that iron-based superconductors are strongly correlated electron systems.

  12. Photoelectrochemical properties of orthorhombic and metastable phase SnS nanocrystals synthesized by a facile colloidal method

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Po-Chia [Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan, ROC (China); Huang, Jow-Lay [Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan, ROC (China); Department of Chemical and Materials Engineering, National University of Kaohsiung, Kaohsiung 81148, Taiwan, ROC (China); Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 70101, Taiwan, ROC (China); Wang, Sheng-Chang; Shaikh, Muhammad Omar [Department of Mechanical Engineering, Southern Taiwan University of Science and Technology, Tainan 710, Taiwan, ROC (China); Lin, Chia-Yu [Department of Chemical Engineering, National Cheng Kung University, Tainan 701, Taiwan, ROC (China)

    2015-12-01

    SnS of orthorhombic (OR) and metastable (SnS) phases were synthesized by using a simple and facile colloidal method. The tin precursor was synthesized using tin oxide (SnO) and oleic acid (OA), while the sulfur precursor was prepared using sulfur powder (S) and oleyamine (OLA). The sulfur precursor was injected into the tin precursor and the prepared SnS nanocrystals were precipitated at a final reaction temperature of 180 °C. The results show that hexamethyldisilazane (HMDS) can be successfully used as a surfactant to synthesize monodisperse 20 nm metastable SnS nanoparticles, while OR phase SnS nanosheets were obtained without HMDS. The direct bandgap observed for the metastable SnS phase is higher (1.66 eV) as compared to the OR phase (1.46 eV). The large blueshift in the direct bandgap of metastable SnS is caused by the difference in crystal structure. The blueshift in the direct band gap value for OR-SnS could be explained by quantum confinement in two dimensions in the very thin nanosheets. SnS thin films used as a photo anode in a photoelectrochemical (PEC) cell were prepared by spin coating on the fluorine-doped tin oxide (FTO) substrates. The photocurrent density of the SnS (metastable SnS)/FTO and SnS (OR)/FTO are 191.8 μA/cm{sup 2} and 57.61 μA/cm{sup 2} at an applied voltage of − 1 V at 150 W, respectively. These narrow band gap and low cost nanocrystals can be used for applications in future optoelectronic devices. - Highlights: • A facile method to synthesize two different phases of SnS having different morphological and optical properties. • The phases and morphologies of SnS nanocrystal can be controlled by adding capping surfactant hexamethyldisilazane (HMDS). • As we know, this is the first metastable SnS photoanode for application in a photoelectrochemical cell.

  13. 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

  14. Phase shifts of the paired wings of butterfly diagrams

    International Nuclear Information System (INIS)

    Li Kejun; Liang Hongfei; Feng Wen

    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. (research papers)

  15. 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)

  16. Defect phase diagram for doping of Ga2O3

    Science.gov (United States)

    Lany, Stephan

    2018-04-01

    For the case of n-type doping of β-Ga2O3 by group 14 dopants (C, Si, Ge, Sn), a defect phase diagram is constructed from defect equilibria calculated over a range of temperatures (T), O partial pressures (pO2), and dopant concentrations. The underlying defect levels and formation energies are determined from first-principles supercell calculations with GW bandgap corrections. Only Si is found to be a truly shallow donor, C is a deep DX-like (lattice relaxed donor) center, and Ge and Sn have defect levels close to the conduction band minimum. The thermodynamic modeling includes the effect of association of dopant-defect pairs and complexes, which causes the net doping to decline when exceeding a certain optimal dopant concentration. The optimal doping levels are surprisingly low, between about 0.01% and 1% of cation substitution, depending on the (T, pO2) conditions. Considering further the stability constraints due to sublimation of molecular Ga2O, specific predictions of optimized pO2 and Si dopant concentrations are given. The incomplete passivation of dopant-defect complexes in β-Ga2O3 suggests a design rule for metastable doping above the solubility limit.

  17. Magnetic phase diagrams of UNiGe

    International Nuclear Information System (INIS)

    Nakotte, H.; Hagmusa, I.H.; Klaasse, J.C.P.; Hagmusa, I.H.; Klaasse, J.C.P.

    1997-01-01

    UNiGe undergoes two magnetic transitions in zero field. Here, the magnetic diagrams of UNiGe for B parallel b and B parallel c are reported. We performed temperatures scans of the magnetization in static magnetic fields up to 19.5T applied along the b and c axes. For both orientations 3 magnetic phases have been identified in the B-T diagrams. We confirmed the previously reported phase boundaries for B parallel c, and in addition we determined the location of the phase boundaries for B parallel b. We discuss a possible relationship of the two zero-field antiferromagnetic phases (commensurate: T<42K; incommensurate: 42K< T<50K) and the field-induced phase, which, at low temperatures, occurs between 18 and 25T or 4 and 10T for B parallel b or B parallel c, respectively. Finally, we discuss the field dependence of the electronic contribution γ to the specific heat for B parallel c up to 17.5T, and we find that its field dependence is similar to the one found in more itinerant uranium compounds

  18. On the phase diagram of non-spherical nanoparticles

    CERN Document Server

    Wautelet, M; Hecq, M

    2003-01-01

    The phase diagram of nanoparticles is known to be a function of their size. In the literature, this is generally demonstrated for cases where their shape is spherical. Here, it is shown theoretically that the phase diagram of non-spherical particles may be calculated from the spherical case, at the same surface area/volume ratio, both with and without surface segregation, provided the surface tension is considered to be isotropic.

  19. Two new Np--Ga phases: α-NpGa2 and metastable m-NpGa2

    International Nuclear Information System (INIS)

    Giessen, B.C.; Elliott, R.O.

    1976-01-01

    Following an earlier study of metastable Np-rich Np--Ga alloys, rapidly quenched Np--Ga alloys with 63 to 80 at. pct. Ga were prepared and studied. Two new NpGa 2 phases, both with an AlB 2 type structure, were found: α-NpGa 2 , with a = 4.246A, c = 4.060A, c/a = 0.956, and m-NpGa 2 , with a = 4.412A, c = 3.642A, c/a = 0.825. While m-NpGa 2 was observed only in very fast quenched (splat cooled) samples and appears to be metastable, α-NpGa 2 is probably an equilibrium phase. In a splat cooled alloy with 75 at. pct. Ga, another, unidentified, metastable phase was observed. Crystal chemical discussions of atomic volumes, interatomic distances and axial ratios are given; the volume difference between the two forms of NpGa 2 is correlated with a valence change of Np

  20. Evolution of metastable phases in silicon during nanoindentation: mechanism analysis and experimental verification

    Energy Technology Data Exchange (ETDEWEB)

    Mylvaganam, K [Centre for Advanced Materials Technology, University of Sydney, NSW 2006 (Australia); Zhang, L C [School of Mechanical and Manufacturing Engineering, University of New South Wales, NSW 2052 (Australia); Eyben, P; Vandervorst, W [IMEC, Kapeldreef 75, B-3001 Leuven (Belgium); Mody, J, E-mail: k.mylvaganam@usyd.edu.a, E-mail: Liangchi.zhang@unsw.edu.a, E-mail: eyben@imec.b, E-mail: jamody@imec.b, E-mail: vdvorst@imec.b [KU Leuven, Electrical Engineering Department, INSYS, Kasteelpark Arenberg 10, B-3001 Leuven (Belgium)

    2009-07-29

    This paper explores the evolution mechanisms of metastable phases during the nanoindentation on monocrystalline silicon. Both the molecular dynamics (MD) and the in situ scanning spreading resistance microscopy (SSRM) analyses were carried out on Si(100) orientation, and for the first time, experimental verification was achieved quantitatively at the same nanoscopic scale. It was found that under equivalent indentation loads, the MD prediction agrees extremely well with the result experimentally measured using SSRM, in terms of the depth of the residual indentation marks and the onset, evolution and dimension variation of the metastable phases, such as {beta}-Sn. A new six-coordinated silicon phase, Si-XIII, transformed directly from Si-I was discovered. The investigation showed that there is a critical size of contact between the indenter and silicon, beyond which a crystal particle of distorted diamond structure will emerge in between the indenter and the amorphous phase upon unloading.

  1. Phase relationships in Cu-rich corner of the Cu-Cr-Zr phase diagram

    International Nuclear Information System (INIS)

    Zeng, K.J.; Haemaelaeinen, M.; Lilius, K.

    1995-01-01

    In the available experimental information on the Cu-Cr-Zr ternary system, there exist different opinions concerning the phase relationships in the Cu-rich corner of Cu-Cr-Zr phase diagram. Glazov et al. and Zakharov et al. investigated the Cu-rich corner of the Cu-Cr-Zr phase diagram within the composition range up to 3.5 Cr and 3.5 Zr (wt. %). A quasi-eutectic reaction L → (Cu) + αCr 2 Zr was observed to occur at 1,020 C and several isothermal sections were constructed within the temperature range from 600 to 1,000 C to show the (Cu)-αCr 2 Zr two phase equilibrium. Therefore, a pseudobinary Cu-Cr 2 Zr system was supposed. Afterwards, Dawakatsu et al, Fedorov et al, and Kuznetsov et al studied the cu-rich corner of the phase diagram in a wider composition range up to 5 Cr and 20 Zr (at.%). Contrary to Glazov et al. and Zakharov et al., they found no Cr 2 Zr phase in their samples. Hence, the pseudobinary Cu-Cr 2 Zr system does not exist. In this study an experimental investigation is presented on the phase relationships in Cu-rich corner of the Cu-Cr-Zr phase diagram at 940 C in order to clear up the confusion

  2. Refined phase diagram of boron nitride

    International Nuclear Information System (INIS)

    Solozhenko, V.; Turkevich, V.Z.

    1999-01-01

    The equilibrium phase diagram of boron nitride thermodynamically calculated by Solozhenko in 1988 has been now refined on the basis of new experimental data on BN melting and extrapolation of heat capacities of BN polymorphs into high-temperature region using the adapted pseudo-Debye model. As compared with the above diagram, the hBN left-reversible cBN equilibrium line is displaced by 60 K toward higher temperatures. The hBN-cBN-L triple point has been calculated to be at 3480 ± 10 K and 5.9 ± 0.1 GPa, while the hBN-L-V triple point is at T = 3400 ± 20 K and p = 400 ± 20 Pa, which indicates that the region of thermodynamic stability of vapor in the BN phase diagram is extremely small. It has been found that the slope of the cBN melting curve is positive whereas the slope of hBN melting curve varies from positive between ambient pressure and 3.4 GPa to negative at higher pressures

  3. 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.

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

    Directory of Open Access Journals (Sweden)

    Mohanty Bedangadas

    2014-03-01

    Full Text Available 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.

  5. Metastable Amyloid Phases and their Conversion to Mature Fibrils

    Science.gov (United States)

    Muschol, Martin; Miti, Tatiana; Mulaj, Mentor; Schmit, Jeremy

    Self-assembly of proteins into amyloid fibrils plays a key role in both functional biological responses and pathogenic disorders which include Alzheimer's disease and type II diabetes. Amyloid fibril assembly frequently generates compact oligomeric and curvilinear polymeric intermediates which are implicated to be toxic to cells. Yet, the relation between these early-stage oligomeric aggregates and late-stage rigid fibrils, which are the hallmark structure of amyloid plaques, has remained unclear. Our measurements indicate that lysozyme amyloid oligomers and their curvilinear fibrils only form after crossing a salt and protein concentration dependent threshold. These oligomeric aggregates are structurally distinct from rigid fibrils and are metastable against nucleation and growth of rigid fibrils. Our experimental transition boundaries match well with colloidal model predictions accounting for salt-modulated charge repulsion. We also report our preliminary findings on the mechanism by which these metastable oligomeric phases are converted into stable amyloid fibrils.

  6. Re-determination of succinonitrile (SCN) camphor phase diagram

    Science.gov (United States)

    Teng, Jing; Liu, Shan

    2006-04-01

    Low-melting temperature transparent organic materials have been extensively used to study the pattern formation and microstructure evolution. It proves to be very challenging to accurately determine the phase diagram since there is no viable way to measure the composition microscopically. In this paper, we presented the detailed experimental characterization of the phase diagram of succinonitrile (SCN)-camphor binary system. Differential scanning calorimetry, a ring-heater, and the directional solidification technique have been combined to determine the details of the phase diagram by using the purified materials. The advantages and disadvantages have been discussed for the different experimental techniques. SCN and camphor constitute a simple binary eutectic system with the eutectic composition at 23.6 wt% camphor and eutectic temperature at 37.65 °C. The solidus and the solubility of the SCN base solid solution have been precisely determined for the first time in this binary system.

  7. CALPHAD calculation of phase diagrams : a comprehensive guide

    CERN Document Server

    Saunders, N; Miodownik, A P

    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-equilibrium phase transformations are also reviewed.

  8. Phase formation in contact of dissimilar metals

    Energy Technology Data Exchange (ETDEWEB)

    Savvin, V S; Kazachkova, Yu A; Povzner, A A [Ural State Technical University-UPI, Mira st., 19, A-203, Yekaterinburg 620002 (Russian Federation)], E-mail: savvin-vs@yandex.ru

    2008-02-15

    Formation and growth of intermediate phases in contact of the crystalline samples forming a two-component eutectic system is considered. It is shown that during the competition to a growing liquid phase the intermediate solid phases cannot grow by diffusion. The alternative is formation of metastable areas of a liquid phase. Measurements of liquid layers extent in Pb-Bi and In-Bi systems have allowed to define the composition of liquid on interface where formation of metastable liquid is possible. The results show that the concentration interval of a liquid layer corresponds to a stable constitution diagram. In order to explain the experimental results the hypothesis according to which the intermediate solid phases are formed as a result of precipitation from metastable melt is considered. The experimental confirmation of formation and crystallization of a metastable liquid is the fact that intergrowth of the samples forming system with an intermetallic phase at temperatures below the temperature of fusion of the most low-melting eutectic is observed. The possibility of the processes concerned with the occurrence of metastable areas of a liquid is showed by means of computer imitation.

  9. The phase diagram of KNO3-KClO3

    International Nuclear Information System (INIS)

    Zhang Xuejun; Tian Jun; Xu Kangcheng; Gao Yici

    2004-01-01

    The binary phase diagram of KNO 3 -KClO 3 is studied by means of differential scanning calorimetry (DSC) and high-temperature X-ray diffraction. The limited solid solutions, K(NO 3 ) 1-x (ClO 3 ) x (0 3 ) 1-x (ClO 3 ) x (0.90 3 -based solid solutions and KClO 3 -based solid solutions phase, respectively. For KNO 3 -based solid solutions, KNO 3 ferroelectric phase can be stable from 423 to 223 K as a result of substituting of NO 3 by ClO 3 -radicals. The temperatures for solidus and liquidus have been determined based on limited solid solutions. Two models, Henrian solution and regular solution theory for KNO 3 -based (α) phase and KClO 3 -based (β) phase, respectively, are employed to reproduce solidus and liquidus of the phase diagram. The results are in good agreement with the DSC data. The thermodynamic properties for α and β solid solutions have been derived from an optimization procedure using the experimental data. The calculated phase diagram and optimized thermodynamic parameters are thermodynamically self-consistent

  10. Phase transformations in ion-mixed metastable (GaSb)1/sub 1 -x/(Ge2)/sub x/ semiconducting alloys

    International Nuclear Information System (INIS)

    Cadien, K.C.; Muddle, B.C.; Greene, J.E.

    1984-01-01

    Low energy (75--175 eV) Ar + ion bombardment during film deposition has been used to produce well-mixed amorphous GaSb/Ge mixtures which, when annealed, transform first to single phase polycrystalline metastable (GaSb)/sub 1-x/(Ge 2 )/sub x/ alloys before eventually transforming to the equilibrium two-phase state. At 500 0 C, for example, the annealing time t/sub a/ required for the amorphous to crystalline metastable (ACM) transformation was approx.10 min, while t/sub a/ for the crystalline metastable to equilibrium (CME) transformation was >6 h. The exothermic enthalpy of crystallization and the onset temperature of the ACM transition were determined as a function of alloy composition using differential thermal analysis. The thermodynamic data was then used to calculate the surface energy per unit area sigma of the amorphous/metastable-crystal interface. sigma was found to exhibit a minimum between x = 0.3 and 0.4. The driving energy for the transition from the crystalline metastable state to the equilibrium two-phase state was of the order of 0.12 kJ cm -3 while the activation barrier was approx.19 kJ cm -3 . Thus, the metastable alloys, which had average grain sizes of 100--200 nm and a lattice constant which varied linearly with x, exhibited good thermal and temporal stability

  11. Conformational properties of rigid-chain amphiphilic macromolecules : The phase diagram

    NARCIS (Netherlands)

    Markov, V. A.; Vasilevskaya, V. V.; Khalatur, P. G.; ten Brinke, G.; Khokhlov, A. R.

    The coil-globule transition in rigid-chain amphiphilic macromolecules was studied by means of computer simulation, and the phase diagrams for such molecules in the solvent quality-persistence length coordinates were constructed. It was shown that the type of phase diagram depends to a substantial

  12. Analyzing phase diagrams and phase transitions in networked competing populations

    Science.gov (United States)

    Ni, Y.-C.; Yin, H. P.; Xu, C.; Hui, P. M.

    2011-03-01

    Phase diagrams exhibiting the extent of cooperation in an evolutionary snowdrift game implemented in different networks are studied in detail. We invoke two independent payoff parameters, unlike a single payoff often used in most previous works that restricts the two payoffs to vary in a correlated way. In addition to the phase transition points when a single payoff parameter is used, phase boundaries separating homogeneous phases consisting of agents using the same strategy and a mixed phase consisting of agents using different strategies are found. Analytic expressions of the phase boundaries are obtained by invoking the ideas of the last surviving patterns and the relative alignments of the spectra of payoff values to agents using different strategies. In a Watts-Strogatz regular network, there exists a re-entrant phenomenon in which the system goes from a homogeneous phase into a mixed phase and re-enters the homogeneous phase as one of the two payoff parameters is varied. The non-trivial phase diagram accompanying this re-entrant phenomenon is quantitatively analyzed. The effects of noise and cooperation in randomly rewired Watts-Strogatz networks are also studied. The transition between a mixed phase and a homogeneous phase is identify to belong to the directed percolation universality class. The methods used in the present work are applicable to a wide range of problems in competing populations of networked agents.

  13. Phase diagram of supercooled water confined to hydrophilic nanopores

    Science.gov (United States)

    Limmer, David T.; Chandler, David

    2012-07-01

    We present a phase diagram for water confined to cylindrical silica nanopores in terms of pressure, temperature, and pore radius. The confining cylindrical wall is hydrophilic and disordered, which has a destabilizing effect on ordered water structure. The phase diagram for this class of systems is derived from general arguments, with parameters taken from experimental observations and computer simulations and with assumptions tested by computer simulation. Phase space divides into three regions: a single liquid, a crystal-like solid, and glass. For large pores, radii exceeding 1 nm, water exhibits liquid and crystal-like behaviors, with abrupt crossovers between these regimes. For small pore radii, crystal-like behavior is unstable and water remains amorphous for all non-zero temperatures. At low enough temperatures, these states are glasses. Several experimental results for supercooled water can be understood in terms of the phase diagram we present.

  14. 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

  15. Phase diagram of nuclear 'pasta' and its uncertainties in supernova cores

    International Nuclear Information System (INIS)

    Sonoda, Hidetaka; Watanabe, Gentaro; Sato, Katsuhiko; Yasuoka, Kenji; Ebisuzaki, Toshikazu

    2008-01-01

    We examine the model dependence of the phase diagram of inhomogeneous nulcear matter in supernova cores using the quantum molecular dynamics (QMD). Inhomogeneous matter includes crystallized matter with nonspherical nuclei--''pasta'' phases--and the liquid-gas phase-separating nuclear matter. Major differences between the phase diagrams of the QMD models can be explained by the energy of pure neutron matter at low densities and the saturation density of asymmetric nuclear matter. We show the density dependence of the symmetry energy is also useful to understand uncertainties of the phase diagram. We point out that, for typical nuclear models, the mass fraction of the pasta phases in the later stage of the collapsing cores is higher than 10-20%

  16. Defect phase diagram for doping of Ga2O3

    Directory of Open Access Journals (Sweden)

    Stephan Lany

    2018-04-01

    Full Text Available For the case of n-type doping of β-Ga2O3 by group 14 dopants (C, Si, Ge, Sn, a defect phase diagram is constructed from defect equilibria calculated over a range of temperatures (T, O partial pressures (pO2, and dopant concentrations. The underlying defect levels and formation energies are determined from first-principles supercell calculations with GW bandgap corrections. Only Si is found to be a truly shallow donor, C is a deep DX-like (lattice relaxed donor center, and Ge and Sn have defect levels close to the conduction band minimum. The thermodynamic modeling includes the effect of association of dopant-defect pairs and complexes, which causes the net doping to decline when exceeding a certain optimal dopant concentration. The optimal doping levels are surprisingly low, between about 0.01% and 1% of cation substitution, depending on the (T, pO2 conditions. Considering further the stability constraints due to sublimation of molecular Ga2O, specific predictions of optimized pO2 and Si dopant concentrations are given. The incomplete passivation of dopant-defect complexes in β-Ga2O3 suggests a design rule for metastable doping above the solubility limit.

  17. 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.

  18. Phase stabilities at a glance: Stability diagrams of nickel dipnictides

    International Nuclear Information System (INIS)

    Bachhuber, F.; Rothballer, J.; Weihrich, R.; Söhnel, T.

    2013-01-01

    In the course of the recent advances in chemical structure prediction, a straightforward type of diagram to evaluate phase stabilities is presented based on an expedient example. Crystal structures and energetic stabilities of dipnictides NiPn 2 (Pn = N, P, As, Sb, Bi) are systematically investigated by first principles calculations within the framework of density functional theory using the generalized gradient approximation to treat exchange and correlation. These dipnictides show remarkable polymorphism that is not yet understood systematically and offers room for the discovery of new phases. Relationships between the concerned structures including the marcasite, the pyrite, the arsenopyrite/CoSb 2 , and the NiAs 2 types are highlighted by means of common structural fragments. Electronic stabilities of experimentally known and related AB 2 structure types are presented graphically in so-called stability diagrams. Additionally, competing binary phases are taken into consideration in the diagrams to evaluate the stabilities of the title compounds with respect to decomposition. The main purpose of the stability diagrams is the introduction of an image that enables the estimation of phase stabilities at a single glance. Beyond that, some of the energetically favored structure types can be identified as potential new phases

  19. A popular metastable omega phase in body-centered cubic steels

    Energy Technology Data Exchange (ETDEWEB)

    Ping, D.H., E-mail: ping.de-hai@nims.go.jp [National Institute for Materials Science, Sengen 1-2-1, Tsukuba 305-0047 (Japan); Geng, W.T., E-mail: geng@ustb.edu.cn [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China)

    2013-05-15

    Steel remains to be one of the most common structural materials in the world as human civilization advances from the Iron Age to the ongoing Silicon Age. Our knowledge of its microstructure evolution and structure–performance relationship is nevertheless still incomplete. We report the observation and characterization of a long ignored metastable phase formed in steels with body-centered cubic (bcc) structure using both transmission electron microscopy and density functional theory calculations. This ω phase has a hexagonal structure and coherent interface with the matrix: a{sub ω} = √2 × a{sub bcc} and c{sub ω} = √3/2 × a{sub bcc}. It is 3.6% smaller in volume and 0.18 eV higher in energy than bcc-Fe, with atoms in alternating close- and loose-packed layers couple anti-ferromagnetically. Carbon plays a crucial role in promoting bcc to ω transformation. At a concentration higher than 4 at.% they tend to segregate from the bcc matrix to the ω-phase; at about 14 at.%, they can induce bcc to ω transformation; and finally at 25 at.%, they stabilize the ω phase as ω-Fe{sub 3}C. The ω phase in bcc Fe can serve as sinks for vacancies, H, and He atoms, leading to improved resistance of martensitic steels to irradiation damage. - Highlights: ► A long-ignored metastable ω phase in body-centered cubic (bcc) steel. ► The ω phase has hexagonal structure with lattice parameters a{sub ω} = √2 × a{sub bcc} and c{sub ω} = √3/2 × a{sub bcc}. ► Carbon enrichment is found to play a crucial role on the bcc-to-ω phase transformation. ► The ω phase is strongly related to the martensitic transformation and twinning structure. ► The ω phase in bcc Fe can serve as sinks for vacancies, H, and He atoms.

  20. Phase diagram of the ABC model with nonconserving processes

    International Nuclear Information System (INIS)

    Lederhendler, A; Cohen, O; Mukamel, D

    2010-01-01

    The three species ABC model of driven particles on a ring is generalized to include vacancies and particle-nonconserving processes. The model exhibits phase separation at high densities. For equal average densities of the three species, it is shown that although the dynamics is local, it obeys detailed balance with respect to a Hamiltonian with long-range interactions, yielding a nonadditive free energy. The phase diagrams of the conserving and nonconserving models, corresponding to the canonical and grand-canonical ensembles, respectively, are calculated in the thermodynamic limit. Both models exhibit a transition from a homogeneous to a phase-separated state, although the phase diagrams are shown to differ from each other. This conforms with the expected inequivalence of ensembles in equilibrium systems with long-range interactions. These results are based on a stability analysis of the homogeneous phase and exact solution of the continuum equations of the models. They are supported by Monte Carlo simulations. This study may serve as a useful starting point for analyzing the phase diagram for unequal densities, where detailed balance is not satisfied and thus a Hamiltonian cannot be defined

  1. 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.

  2. 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…

  3. Phase diagrams for surface alloys

    DEFF Research Database (Denmark)

    Christensen, Asbjørn; Ruban, Andrei; Stoltze, Per

    1997-01-01

    We discuss surface alloy phases and their stability based on surface phase diagrams constructed from the surface energy as a function of the surface composition. We show that in the simplest cases of pseudomorphic overlayers there are four generic classes of systems, characterized by the sign...... is based on density-functional calculations using the coherent-potential approximation and on effective-medium theory. We give self-consistent density-functional results for the segregation energy and surface mixing energy for all combinations of the transition and noble metals. Finally we discuss...

  4. Magnetic phase diagram of a nanocone

    International Nuclear Information System (INIS)

    Suarez, O; Vargas, P; Escrig, J; Landeros, P; Albir, D; Laroze, D

    2008-01-01

    In this work we analyze the magnetic properties of truncated conical nanoparticles. Based on the continuous magnetic model we find expressions for the total energy in three different magnetic configurations. Finally, we calculate the magnetic phase diagram as function of the geometrical parameters.

  5. Magnetic phase diagram of a nanocone

    Energy Technology Data Exchange (ETDEWEB)

    Suarez, O; Vargas, P [Departamento de Fisica, Universidad Tecnica Federico Santa MarIa, P. O. Box 110-V, Valparaiso (Chile); Escrig, J; Landeros, P; Albir, D [Universidad de Santiago de Chile, Depatamento de Fisica, Casilla 307, Correo 2, Santiago (Chile); Laroze, D [Instituto de Fisica, Pontificia Universidad Catolica de Valparaiso, P. O. Box 4059, Valparaiso (Chile)], E-mail: omar.suarez@postgrado.usm.cl

    2008-11-01

    In this work we analyze the magnetic properties of truncated conical nanoparticles. Based on the continuous magnetic model we find expressions for the total energy in three different magnetic configurations. Finally, we calculate the magnetic phase diagram as function of the geometrical parameters.

  6. On the question of calculation methods of phase diagrams

    International Nuclear Information System (INIS)

    Vasil'ev, M.V.

    1983-01-01

    The technique of determining interaction parameters of components of binary alloys is suggested. U-Mo and Cu-Al systems are used as example with the aid of experimental state diagrams. It is shown that the search for new regularities is necessary with the aim of analytical description of state diagrams and forecast of the shape of phase equilibria curves in real systems. Optimum combinations of experimental investigations with the aim of reliable determination of supporting points and forecasting possibilities of typical equations can considerably decrease the volume of experimental work when preparing state diagrams, in cases of repeated state diagrams of more reliable state diagrams with the application of more advanced methods of investigation. The translation of state diagrams from geometric to analytical language with the use of typical equations opens up new possibilities for establishing a compact information bank for state diagrams

  7. Applications of phase diagrams in metallurgy and ceramics

    International Nuclear Information System (INIS)

    Carter, G.C.

    1978-03-01

    The workshop represents an effort to coordinate and reinforce the current efforts on compilation of phase diagrams of alloys and ceramics. Many research groups and individual scientists throughout the world are concerned with phase equilibrium data. Specialized expertise exists in small institutions as well as large laboratories. If this talent can be effecively utilized through a cooperative effort, the needs for such data can be met. The Office of Standard Reference Data, which serves as the program management office for the National Standard Reference Data System, is eager to work with all groups concerned with this problem. Through a cooperative international effort we can carry out a task which has become too large for an individual. Volume 2 presents computational techniques for phase diagram construction

  8. Phase Diagram of the Ethylene Glycol-Dimethylsulfoxide System

    Science.gov (United States)

    Solonina, I. A.; Rodnikova, M. N.; Kiselev, M. R.; Khoroshilov, A. V.; Shirokova, E. V.

    2018-05-01

    The phase diagram of ethylene glycol (EG)-dimethylsulfoxide (DMSO) system is studied in the temperature range of +25 to -140°C via differential scanning calorimetry. It is established that the EG-DMSO system is characterized by strong overcooling of the liquid phase, a glass transition at -125°C, and the formation of a compound with the composition of DMSO · 2EG. This composition has a melting temperature of -60°C, which is close to those of neighboring eutectics (-75 and -70°C). A drop in the baseline was observed in the temperature range of 8 to -5°C at DMSO concentrations of 5-50 mol %, indicating the existence of a phase separation area in the investigated system. The obtained data is compared to the literature data on the H2O-DMSO phase diagram.

  9. Thermal stability and phase transformation of metastable phases in Zr-Nb

    International Nuclear Information System (INIS)

    Aurelio, G.; Fernandez Guillermet, Armando

    2003-01-01

    The lattice parameters of the bcc (β) and (Ω) phases occurring metastability in a series of Zr-rich Zr-Nb alloys have been determined at and above room temperature (TR) using neutron diffraction techniques. In the first place, the effect of temperature changes upon the lattice parameters of the β and Ω phases in alloys with 10 and 18 at. % Nb was monitored using neutron thermo-diffraction. A method of analysis is applied to the data, which involve a confrontation between the observed structural properties and an idealized -or 'reference'- behavior (RB) which admits a simple mathematical description. A generalized form of the law of Vegard is adopted as RB for the β phase, whereas a specific RB is proposed for the Ω structure. The experimental data are well accounted for by this interpretation scheme, leading to a picture of the isothermal reactions occurring at high temperature, which involves the transfer of Nb from the Ω to the β phase. Finally, the neutron diffraction data on the Ω phase is combined with an electron microscopy study for the alloy with 10 at. % Nb aged at 773 K, which provides information on the composition of this phase and its evolution towards thermodynamic equilibrium. (author)

  10. On a metastable vacuum burning phenomenon

    International Nuclear Information System (INIS)

    Berezin, V.A.; Tkachev, I.I.; Kuzmin, V.A.; AN SSSR, Moscow. Inst. Yadernykh Issledovanij)

    1983-02-01

    Equations of motion of an interface between two phases with arbitrary equations of state are obtained. It is found that there may take place a process of metastable vacuum burning. It is shown that under some conditions the process of the new phase bubble expansion is described by the detonation wave equations. Possible cosmological consequences of the metastable phase burning effect are briefly discussed. (author)

  11. Phase diagram of a Lennard-Jones solid

    International Nuclear Information System (INIS)

    Choi, Y.; Ree, T.; Ree, F.H.

    1993-01-01

    A phase diagram of a Lennard-Jones solid at kT/ε≥0.8 is constructed by our recent perturbation theory. It shows the stability of the face-centered-cubic phase except within a small pressure and temperature domain, where the hexagonal-close packed phase may occur. The theory predicts anharmonic contributions to the Helmholtz free energy (important to the crystal stability) in good agreement with Monte Carlo data

  12. 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.

  13. 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 report...

  14. Investigation of binary solid phases by calorimetry and kinetic modelling

    NARCIS (Netherlands)

    Matovic, M.

    2007-01-01

    The traditional methods for the determination of liquid-solid phase diagrams are based on the assumption that the overall equilibrium is established between the phases. However, the result of the crystallization of a liquid mixture will typically be a non-equilibrium or metastable state of the

  15. 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. (c) 2010 Elsevier Inc. All rights reserved.

  16. Phase diagram Fe-Sn-Sr. New experimental results

    International Nuclear Information System (INIS)

    Nieva, N; Jimenez, M.J; Gomez, A; Corvalan Moya, C; Arias, D

    2012-01-01

    Zr-based alloys are widely used in nuclear industry due to their specific characteristics. The information of the phase diagrams of the ternary system Fe-Zr-Sn is scarce. In this work we investigate, in a experimental way, the central and the Fe-Sn binary adjacent regions of the Fe-Sn-Zr Gibbs triangle at the temperature of 800 o C. For the experimental work, a set of seven ternary alloys was designed, produced and examined by different complementary techniques. There were performed two types of heat treatments: one of medium and another of long duration. We present a new proposal for the 800 o C isothermal section. The boundaries of the identified phases and the fields of one, two and three phases are indicated in the diagram

  17. T- P Phase Diagram of Nitrogen at High Pressures

    Science.gov (United States)

    Algul, G.; Enginer, Y.; Yurtseven, H.

    2018-05-01

    By employing a mean field model, calculation of the T- P phase diagram of molecular nitrogen is performed at high pressures up to 200 GPa. Experimental data from the literature are used to fit a quadratic function in T and P, describing the phase line equations which have been derived using the mean field model studied here for N 2, and the fitted parameters are determined. Our model study gives that the observed T- P phase diagram can be described satisfactorily for the first-order transitions between the phases at low as well as high pressures in nitrogen. Some thermodynamic quantities can also be predicted as functions of temperature and pressure from the mean field model studied here and they can be compared with the experimental data.

  18. Melting in Two-Dimensional Lennard-Jones Systems: Observation of a Metastable Hexatic Phase

    International Nuclear Information System (INIS)

    Chen, K.; Kaplan, T.; Mostoller, M.

    1995-01-01

    Large scale molecular dynamics simulations of two-dimensional melting have been carried out using a recently revised Parrinello-Rahman scheme on massively parallel supercomputers. A metastable state is observed between the solid and liquid phases in Lennard-Jones systems of 36 864 and 102 400 atoms. This intermediate state shows the characteristics of the hexatic phase predicted by the theory of Kosterlitz, Thouless, Halperin, Nelson, and Young

  19. Exact ground-state phase diagrams for the spin-3/2 Blume-Emery-Griffiths model

    Energy Technology Data Exchange (ETDEWEB)

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

    2008-05-15

    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 J<0, respectively, on the diatomic lattice and have found the conditions for the existence of uniform and intermediate or non-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.

  20. The effective QCD phase diagram and the critical end point

    Directory of Open Access Journals (Sweden)

    Alejandro Ayala

    2015-08-01

    Full Text Available We study the QCD phase diagram on the temperature T and quark chemical potential μ plane, modeling the strong interactions with the linear sigma model coupled to quarks. The phase transition line is found from the effective potential at finite T and μ taking into account the plasma screening effects. We find the location of the critical end point (CEP to be (μCEP/Tc,TCEP/Tc∼(1.2,0.8, where Tc is the (pseudocritical temperature for the crossover phase transition at vanishing μ. This location lies within the region found by lattice inspired calculations. The results show that in the linear sigma model, the CEP's location in the phase diagram is expectedly determined solely through chiral symmetry breaking. The same is likely to be true for all other models which do not exhibit confinement, provided the proper treatment of the plasma infrared properties for the description of chiral symmetry restoration is implemented. Similarly, we also expect these corrections to be substantially relevant in the QCD phase diagram.

  1. Critical point analysis of phase envelope diagram

    International Nuclear Information System (INIS)

    Soetikno, Darmadi; Siagian, Ucok W. R.; Kusdiantara, Rudy; Puspita, Dila; Sidarto, Kuntjoro A.; Soewono, Edy; Gunawan, Agus Y.

    2014-01-01

    Phase diagram or phase envelope is a relation between temperature and pressure that shows the condition of equilibria between the different phases of chemical compounds, mixture of compounds, and solutions. Phase diagram is an important issue in chemical thermodynamics and hydrocarbon reservoir. It is very useful for process simulation, hydrocarbon reactor design, and petroleum engineering studies. It is constructed from the bubble line, dew line, and critical point. Bubble line and dew line are composed of bubble points and dew points, respectively. Bubble point is the first point at which the gas is formed when a liquid is heated. Meanwhile, dew point is the first point where the liquid is formed when the gas is cooled. Critical point is the point where all of the properties of gases and liquids are equal, such as temperature, pressure, amount of substance, and others. Critical point is very useful in fuel processing and dissolution of certain chemicals. Here in this paper, we will show the critical point analytically. Then, it will be compared with numerical calculations of Peng-Robinson equation by using Newton-Raphson method. As case studies, several hydrocarbon mixtures are simulated using by Matlab

  2. Critical point analysis of phase envelope diagram

    Energy Technology Data Exchange (ETDEWEB)

    Soetikno, Darmadi; Siagian, Ucok W. R. [Department of Petroleum Engineering, Institut Teknologi Bandung, Jl. Ganesha 10, Bandung 40132 (Indonesia); Kusdiantara, Rudy, E-mail: rkusdiantara@s.itb.ac.id; Puspita, Dila, E-mail: rkusdiantara@s.itb.ac.id; Sidarto, Kuntjoro A., E-mail: rkusdiantara@s.itb.ac.id; Soewono, Edy; Gunawan, Agus Y. [Department of Mathematics, Institut Teknologi Bandung, Jl. Ganesha 10, Bandung 40132 (Indonesia)

    2014-03-24

    Phase diagram or phase envelope is a relation between temperature and pressure that shows the condition of equilibria between the different phases of chemical compounds, mixture of compounds, and solutions. Phase diagram is an important issue in chemical thermodynamics and hydrocarbon reservoir. It is very useful for process simulation, hydrocarbon reactor design, and petroleum engineering studies. It is constructed from the bubble line, dew line, and critical point. Bubble line and dew line are composed of bubble points and dew points, respectively. Bubble point is the first point at which the gas is formed when a liquid is heated. Meanwhile, dew point is the first point where the liquid is formed when the gas is cooled. Critical point is the point where all of the properties of gases and liquids are equal, such as temperature, pressure, amount of substance, and others. Critical point is very useful in fuel processing and dissolution of certain chemicals. Here in this paper, we will show the critical point analytically. Then, it will be compared with numerical calculations of Peng-Robinson equation by using Newton-Raphson method. As case studies, several hydrocarbon mixtures are simulated using by Matlab.

  3. Mapping Isobaric Aging onto the Equilibrium Phase Diagram

    DEFF Research Database (Denmark)

    Niss, Kristine

    2017-01-01

    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...

  4. Phase diagrams of laser-processed nanoparticles of brass

    Energy Technology Data Exchange (ETDEWEB)

    Kazakevich, P.V. [Wave Research Center of A.M. Prokhorov General Physics Institute of the Russian Academy of Sciences 38, Vavilov Street, 119991 Moscow (Russian Federation); Simakin, A.V. [Wave Research Center of A.M. Prokhorov General Physics Institute of the Russian Academy of Sciences 38, Vavilov Street, 119991 Moscow (Russian Federation); Shafeev, G.A. [Wave Research Center of A.M. Prokhorov General Physics Institute of the Russian Academy of Sciences 38, Vavilov Street, 119991 Moscow (Russian Federation); Monteverde, F. [Electron Microscopy Unit, Materia Nova, Avenue Copernic 1, B-7000 Mons (Belgium); Wautelet, M. [Condensed Matter Physics, University of Mons-Hainaut, 23, Avenue Maistriau, B-7000 Mons (Belgium)]. E-mail: michel.wautelet@umh.ac.be

    2007-07-31

    Nanoparticles of brass are prepared by ablation of a brass target in ethanol using radiation of a copper-vapor laser at various laser fluences. The nanoparticles are characterized by TEM and optical spectroscopy. The multipulse laser irradiation leads to formation both the nanoparticles in liquid and well-ordered micro-structures on a surface of a target. It is revealed that both the morphology and absorption spectra of brass nanoparticles depend on presence of the micro-structures. Nanoparticles with the various phase diagrams are formed from a flat brass surface and from the same surface with micro-structures. The results are compared with a model of phase diagrams, in which size and composition effects are taken into account.

  5. Low-pressure phase diagram of crystalline benzene from quantum Monte Carlo

    Energy Technology Data Exchange (ETDEWEB)

    Azadi, Sam, E-mail: s.azadi@ucl.ac.uk [Departments of Physics and Astronomy, University College London, Thomas Young Center, London Centre for Nanotechnology, London WC1E 6BT (United Kingdom); Cohen, R. E. [Extreme Materials Initiative, Geophysical Laboratory, Carnegie Institution for Science, Washington, DC 20015 (United States); Department of Earth- and Environmental Sciences, Ludwig Maximilians Universität, Munich 80333 (Germany); Department of Physics and Astronomy, University College London, London WC1E 6BT (United Kingdom)

    2016-08-14

    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 P2{sub 1}/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 P2{sub 1}/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.

  6. Na-Si binary phase diagram and solution growth of silicon crystals

    International Nuclear Information System (INIS)

    Morito, H.; Yamada, T.; Ikeda, T.; Yamane, H.

    2009-01-01

    In the present study, a Na-Si binary phase diagram was first presented from the results of differential thermal analysis and X-ray diffraction. Based on the phase diagram, we performed low-temperature formation of single crystals, film and porous bulk of Si by vaporizing Na from a Na-Si melt at 800 or 900 deg. C.

  7. 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.

  8. 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.)

  9. Phase diagram and quench dynamics of the cluster-XY spin chain.

    Science.gov (United States)

    Montes, Sebastián; Hamma, Alioscia

    2012-08-01

    We study the complete phase space and the quench dynamics of an exactly solvable spin chain, the cluster-XY model. In this chain, the cluster term and the XY couplings compete to give a rich phase diagram. The phase diagram is studied by means of the quantum geometric tensor. We study the time evolution of the system after a critical quantum quench using the Loschmidt echo. The structure of the revivals after critical quantum quenches presents a nontrivial behavior depending on the phase of the initial state and the critical point.

  10. Quantum corrections for the phase diagram of systems with competing order

    Science.gov (United States)

    Silva, N. L., Jr.; Continentino, Mucio A.; Barci, Daniel G.

    2018-06-01

    We use the effective potential method of quantum field theory to obtain the quantum corrections to the zero temperature phase diagram of systems with competing order parameters. We are particularly interested in two different scenarios: regions of the phase diagram where there is a bicritical point, at which both phases vanish continuously, and the case where both phases coexist homogeneously. We consider different types of couplings between the order parameters, including a bilinear one. This kind of coupling breaks time-reversal symmetry and it is only allowed if both order parameters transform according to the same irreducible representation. This occurs in many physical systems of actual interest like competing spin density waves, different types of orbital antiferromagnetism, elastic instabilities of crystal lattices, vortices in a multigap SC and also applies to describe the unusual magnetism of the heavy fermion compound URu2Si2. Our results show that quantum corrections have an important effect on the phase diagram of systems with competing orders.

  11. Quantum corrections for the phase diagram of systems with competing order.

    Science.gov (United States)

    Silva, N L; Continentino, Mucio A; Barci, Daniel G

    2018-06-06

    We use the effective potential method of quantum field theory to obtain the quantum corrections to the zero temperature phase diagram of systems with competing order parameters. We are particularly interested in two different scenarios: regions of the phase diagram where there is a bicritical point, at which both phases vanish continuously, and the case where both phases coexist homogeneously. We consider different types of couplings between the order parameters, including a bilinear one. This kind of coupling breaks time-reversal symmetry and it is only allowed if both order parameters transform according to the same irreducible representation. This occurs in many physical systems of actual interest like competing spin density waves, different types of orbital antiferromagnetism, elastic instabilities of crystal lattices, vortices in a multigap SC and also applies to describe the unusual magnetism of the heavy fermion compound URu 2 Si 2 . Our results show that quantum corrections have an important effect on the phase diagram of systems with competing orders.

  12. Phase diagram of the ternary Zr-Ti-Sn system

    International Nuclear Information System (INIS)

    Arias, D.; Gonzalez Camus, M.

    1987-01-01

    It is well known that Ti stabilizes the high temperature cubic phase of Zr and that Sn stabilizes the low temperature hexagonal phase of Zr. The effect of Sn on the Zr-Ti diagram has been studied in the present paper. Using high purity metals, nine different alloys have been prepared, with 4-32 at % Ti, 0.7-2.2 at % Sn and Zr till 100%. Resistivity and optical and SEM metallography techniques have been employed. Effect of some impurities have been analyzed. The results are discussed and different isothermic sections of the ternary Zr-Ti-Sn diagram are presented. (Author) [es

  13. Mapping Isobaric Aging onto the Equilibrium Phase Diagram.

    Science.gov (United States)

    Niss, Kristine

    2017-09-15

    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.

  14. Phase diagram and structural evolution of tin/indium (Sn/In) nanosolder particles: from a non-equilibrium state to an equilibrium state.

    Science.gov (United States)

    Shu, Yang; Ando, Teiichi; Yin, Qiyue; Zhou, Guangwen; Gu, Zhiyong

    2017-08-31

    A binary system of tin/indium (Sn/In) in the form of nanoparticles was investigated for phase transitions and structural evolution at different temperatures and compositions. The Sn/In nanosolder particles in the composition range of 24-72 wt% In were synthesized by a surfactant-assisted chemical reduction method under ambient conditions. The morphology and microstructure of the as-synthesized nanoparticles were analyzed by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and X-ray diffraction (XRD). HRTEM and SAED identified InSn 4 and In, with some Sn being detected by XRD, but no In 3 Sn was observed. The differential scanning calorimetry (DSC) thermographs of the as-synthesized nanoparticles exhibited an endothermic peak at around 116 °C, which is indicative of the metastable eutectic melting of InSn 4 and In. When the nanosolders were subjected to heat treatment at 50-225 °C, the equilibrium phase In 3 Sn appeared while Sn disappeared. The equilibrium state was effectively attained at 225 °C. A Tammann plot of the DSC data of the as-synthesized nanoparticles indicated that the metastable eutectic composition is about 62% In, while that of the DSC data of the 225 °C heat-treated nanoparticles yielded a eutectic composition of 54% In, which confirmed the attainment of the equilibrium state at 225 °C. The phase boundaries estimated from the DSC data of heat-treated Sn/In nanosolder particles matched well with those in the established Sn-In equilibrium phase diagram. The phase transition behavior of Sn/In nanosolders leads to a new understanding of binary alloy particles at the nanoscale, and provides important information for their low temperature soldering processing and applications.

  15. Characterization of Cr-rich Cr-Sb multilayer films: Syntheses of a new metastable phase using modulated elemental reactants

    International Nuclear Information System (INIS)

    Regus, Matthias; Mankovsky, Sergiy; Polesya, Svitlana; Kuhn, Gerhard; Ditto, Jeffrey; Schürmann, Ulrich; Jacquot, Alexandre; Bartholomé, Kilian; Näther, Christian; Winkler, Markus; König, Jan D.; Böttner, Harald; Kienle, Lorenz; Johnson, David C.; Ebert, Hubert; Bensch, Wolfgang

    2015-01-01

    The new metastable compound Cr 1+x Sb with x up to 0.6 has been prepared via a thin film approach using modulated elemental reactants and investigated by in-situ X-ray reflectivity, X-ray diffraction, differential scanning calorimetry, energy dispersive X-ray analysis as well as transmission electron microscopy and atomic force microscopy. The new Cr-rich antimonide crystallizes in a structure related to the Ni 2 In-type structure, where the crystallographic position (1/3, 2/3, 3/4) is partially occupied by excess Cr. The elemental layers of the pristine material interdiffused significantly before Cr 1+x Sb crystallized. A change in the activation energy was observed for the diffusion process when crystal growth starts. First-principles electronic structure calculations provide insight into the structural stability, magnetic properties and resistivity of Cr 1+x Sb. - Graphical abstract: 1 amorphous multilayered film 2 interdiffused amorphous film 3 metastable crystalline phase 4 thermodynamic stable phase (and by-product). - Highlights: • Interdiffusion of amorphous Cr and Sb occurs before crystallization. • Crystallization of a new metastable phase Cr 1.6 Sb in Ni 2 In-type structure. • The new Cr-rich phase shows half-metallic behavior

  16. Structures, phase stabilities, and electrical potentials of Li-Si battery anode materials

    KAUST Repository

    Tipton, William W.; Bealing, Clive R.; Mathew, Kiran; Hennig, Richard G.

    2013-01-01

    of composition, and a genetic algorithm coupled to density-functional theory searches the Li-Si binary phase diagram for small-cell, metastable crystal structures. Calculations of the phonon densities of states using density-functional perturbation theory

  17. Phase diagram of strongly correlated Fermi systems

    International Nuclear Information System (INIS)

    Zverev, M.V.; Khodel', V.A.; Baldo, M.

    2000-01-01

    Phase transitions in uniform Fermi systems with repulsive forces between the particles caused by restructuring of quasiparticle filling n(p) are analyzed. It is found that in terms of variables, i.e. density ρ, nondimensional binding constant η, phase diagram of a strongly correlated Fermi system for rather a wide class of interactions reminds of a puff-pastry pie. Its upper part is filled with fermion condensate, the lower one - with normal Fermi-liquid. They are separated by a narrow interlayer - the Lifshits phase, characterized by the Fermi multibound surface [ru

  18. Low-temperature thermal expansion of metastable intermetallic Fe-Cr phases

    International Nuclear Information System (INIS)

    Gorbunoff, A.; Levin, A.A.; Meyer, D.C.

    2009-01-01

    The thermal expansion coefficients (TEC) of metastable disordered intermetallic Fe-Cr phases formed in thin Fe-Cr alloy films prepared by an extremely non-equilibrium method of the pulsed laser deposition are studied. The lattice parameters of the alloys calculated from the low-temperature wide-angle X-ray diffraction (WAXRD) patterns show linear temperature dependencies in the temperature range 143-293 K and a deviation from the linearity at lower temperatures. The linear thermal expansion coefficients determined from the slopes of the linear portions of the temperature-lattice parameter dependencies differ significantly from phase to phase and from the values expected for the body-centered cubic (b.c.c.) Fe 1-x Cr x solid solutions. Strain-crystallite size analysis of the samples is performed. Predictions about the Debye temperature and the mechanical properties of the alloys are made.

  19. (α,η) phase diagrams in tilted chiral smectics

    International Nuclear Information System (INIS)

    Rjili, M.; Marcerou, J.P.; Gharbi, A.; Othman, T.

    2013-01-01

    The polymorphism of tilted chiral smectics liquid crystals is incredibly rich and encompasses many subphases such as SmC A ⁎ ; SmC Fi1 ⁎ ; SmC Fi2 ⁎ ; SmC ⁎ ; SmC α ⁎ . 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 (α,η) plane where α is local angular parameter and η 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 5 ⁎ and the SmC 6 ⁎ ones. However, it should be emphasized that the details of predicted phase diagram are strongly dependent on the compound studied.

  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. Magnetic phase diagram of HoxTm1-x alloys

    DEFF Research Database (Denmark)

    Sarthour, R.S.; Cowley, R.A.; Ward, R.C.C.

    2000-01-01

    The magnetic phase diagram of the competing anisotropy system, Ho/Tm, has been determined by neutron-scattering techniques and the results compared with calculations based on a mean-field model. The crystal-field interactions in Ho favor alignment of the magnetic moments in the basal plane whereas......, with long-range order, were identified and the magnetic phase diagram, including a pentacritical point, determined. A mean-field model was used to explain the results and the results are in good agreement with the experimental results....... in Tm they favor alignment along the c axis. Single-crystal alloys were grown with molecular-beam epitaxy techniques in Oxford. The components of the magnetic moment alone the c direction and in the basal plane were determined from the neutron-scattering measurements. Five distinct magnetic phases...

  2. Thermodynamic study of CVD-ZrO2 phase diagrams

    International Nuclear Information System (INIS)

    Torres-Huerta, A.M.; Vargas-Garcia, J.R.; Dominguez-Crespo, M.A.; Romero-Serrano, J.A.

    2009-01-01

    Chemical vapor deposition (CVD) of zirconium oxide (ZrO 2 ) from zirconium acetylacetonate Zr(acac) 4 has been thermodynamically investigated using the Gibbs' free energy minimization method and the FACTSAGE program. Thermodynamic data Cp o , ΔH o and S o for Zr(acac) 4 have been estimated using the Meghreblian-Crawford-Parr and Benson methods because they are not available in the literature. The effect of deposition parameters, such as temperature and pressure, on the extension of the region where pure ZrO 2 can be deposited was analyzed. The results are presented as calculated CVD stability diagrams. The phase diagrams showed two zones, one of them corresponds to pure monoclinic phase of ZrO 2 and the other one corresponds to a mix of monoclinic phase of ZrO 2 and graphite carbon.

  3. Exploring the Nuclear Phase Diagram with Beam Energy Scans

    International Nuclear Information System (INIS)

    Horvat, Stephen

    2017-01-01

    The nuclear phase diagram is mapped using beam energy scans of relativistic heavy-ion collisions. This mapping is possible because different collision energies develop along different trajectories through the phase diagram. High energy collisions will evolve though a crossover phase transition according to lattice QCD, but lower collision energies may traverse a first order phase transition. There are hints for this first order phase transition and its critical endpoint, but further measurements and theoretical guidance is needed. In addition to mapping the phase transition, beam energy scans allow us to see if we can turn off the signatures of deconfinement. If an observable is a real signature for the formation of the deconfined state called quark-gluon plasma, then it should turn off at sufficiently low collision energies. In this summary talk I will show the current state of the field using beam energy scan results from RHIC and SPS, I will show where precise theoretical guidance is needed for understanding recent measurements, and I will motivate the need for more data and new measurements from FAIR, NICA, RHIC, and the SPS. (paper)

  4. Transportation properties of amorphous state InSb and its metastable middle phase

    International Nuclear Information System (INIS)

    Cao Xiaowen

    1990-09-01

    The variation of the substrate temperature induces the metal-semiconductor transition in the condensation InSb films at low temperatrue. The electron conduction is dominant in the metal-type amorphous InSb and the hole in semiconductor-type one. In the metal-type amorphous InSb the electron-electron is correlated under the field above 0.1T in the temperature region of liquid nitrogen. The structure relaxation leads to not only the increase of the short range order but also the change of electron structure in metal-type amorphous InSb. The first conductance jump originates mainly from the increase of Hall mobility of the carrier, i.e. the increase of the short range order, and the system relaxes from the liquid-like to the lattice-like amorphous state. The three types of the crystallization phase transition for the metal-type amorphous InSb present obviously different transportation behaviours. Both metal-type amorphous state and metastable middle phase of InSb all are one of superconducting system with the lowest carrier concentration (n 0 ∼10 18 cm -3 ). Superconducting T c of the metastable middle phase is related to the state density near Fermi surface, i.e. the higher T c corresponds to the higher state density. The quasi-two-dimensional structure is favourable to superconductivity

  5. Thermodynamic analysis of 6xxx series Al alloys: Phase fraction diagrams

    Directory of Open Access Journals (Sweden)

    Cui S.

    2018-01-01

    Full Text Available Microstructural evolution of 6xxx Al alloys during various metallurgical processes was analyzed using accurate thermodynamic database. Phase fractions of all the possible precipitate phases which can form in the as-cast and equilibrium states of the Al-Mg-Si-Cu-Fe-Mn-Cr alloys were calculated over the technically useful composition range. The influence of minor elements such as Cu, Fe, Mn, and Cr on the amount of each type of precipitate in the as-cast and equilibrium conditions were analyzed. Phase fraction diagrams at 500 °C were mapped in the composition range of 0-1.1 wt.% Mg and 0-0.7 wt.% Si to investigate the as-homogenized microstructure. In addition, phase fraction diagram of Mg2Si at 177 °C was mapped to understand the microstructure after final annealing of 6xxx Al alloy. Based on the calculated diagrams, the design strategy of 6xxx Al alloy to produce highest strength due to Mg2Si is discussed.

  6. Evaluated phase diagrams of binary metal-tellurium systems of the D-block transition elements

    International Nuclear Information System (INIS)

    Chattopadhyay, G.; Bharadwaj, S.R.

    1989-01-01

    The binary phase diagrams of metal-tellurium systems for twenty seven d-block transition elements have been critically evaluated. Complete phase diagrams are presented for the elements, chromium, manganese, iron, cobalt, nickel, copper, molybdenum, palladium, silver, lanthanum, platinum and gold, whereas, for scandium, titanium, vanadium, yttrium, zirconium, niobium, technitium, ruthenium, rhodium, hafnium, tantalum, tungsten , rhenium, osmium and iridium, the phase diagrams are incomplete and tentative. (author). 20 refs., 27 tabs., 27 figs

  7. HgTe-CdTe phase diagrams calculation by RAS model

    International Nuclear Information System (INIS)

    Hady, A.A.A.

    1986-11-01

    The model of Regular Associated Solutions (RAS) for binary solution, which extended onto the ternary solution was used for Mercury-Cadnium-Tellurim phase diagrams calculations. The function of dissociation parameters is used here as a function of temperature and it is independent of composition. The ratio of mole fractions has a weak dependence on temperature and is not neglected. The calculated liquidus binary temperature and the experimental one are so fitted to give the best values of parameters used to calculate the HgTe-CdTe phase diagrams. (author)

  8. How little data is enough? Phase-diagram analysis of sparsity-regularized X-ray computed tomography

    DEFF Research Database (Denmark)

    Jørgensen, Jakob Sauer; Sidky, E. Y.

    2015-01-01

    We introduce phase-diagram analysis, a standard tool in compressed sensing (CS), to the X-ray computed tomography (CT) community as a systematic method for determining how few projections suffice for accurate sparsity-regularized reconstruction. In CS, a phase diagram is a convenient way to study...... and express certain theoretical relations between sparsity and sufficient sampling. We adapt phase-diagram analysis for empirical use in X-ray CT for which the same theoretical results do not hold. We demonstrate in three case studies the potential of phase-diagram analysis for providing quantitative answers...... measurements does not lead to improved performance compared with standard structured sampling patterns. Finally, we show preliminary results of how well phase-diagram analysis can predict the sufficient number of projections for accurately reconstructing a large-scale image of a given sparsity by means...

  9. Sedimentation stacking diagram of binary colloidal mixtures and bulk phases in the plane of chemical potentials

    International Nuclear Information System (INIS)

    Heras, Daniel de las; Schmidt, Matthias

    2015-01-01

    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. (paper)

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

    International Nuclear Information System (INIS)

    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

  11. Phase diagram of ammonium nitrate

    Energy Technology Data Exchange (ETDEWEB)

    Dunuwille, Mihindra; Yoo, Choong-Shik, E-mail: csyoo@wsu.edu [Department of Chemistry and Institute for Shock Physics, Washington State University, Pullman, Washington 99164 (United States)

    2013-12-07

    Ammonium Nitrate (AN) is a fertilizer, yet becomes an explosive upon a small addition of chemical impurities. The origin of enhanced chemical sensitivity in impure AN (or AN mixtures) is not well understood, posing significant safety issues in using AN even today. To remedy the situation, we have carried out an extensive study to investigate the phase stability of AN and its mixtures with hexane (ANFO–AN mixed with fuel oil) and Aluminum (Ammonal) at high pressures and temperatures, using diamond anvil cells (DAC) and micro-Raman spectroscopy. The results indicate that pure AN decomposes to N{sub 2}, N{sub 2}O, and H{sub 2}O at the onset of the melt, whereas the mixtures, ANFO and Ammonal, decompose at substantially lower temperatures. The present results also confirm the recently proposed phase IV-IV{sup ′} transition above 17 GPa and provide new constraints for the melting and phase diagram of AN to 40 GPa and 400°C.

  12. Phase diagram of ammonium nitrate

    International Nuclear Information System (INIS)

    Dunuwille, Mihindra; Yoo, Choong-Shik

    2013-01-01

    Ammonium Nitrate (AN) is a fertilizer, yet becomes an explosive upon a small addition of chemical impurities. The origin of enhanced chemical sensitivity in impure AN (or AN mixtures) is not well understood, posing significant safety issues in using AN even today. To remedy the situation, we have carried out an extensive study to investigate the phase stability of AN and its mixtures with hexane (ANFO–AN mixed with fuel oil) and Aluminum (Ammonal) at high pressures and temperatures, using diamond anvil cells (DAC) and micro-Raman spectroscopy. The results indicate that pure AN decomposes to N 2 , N 2 O, and H 2 O at the onset of the melt, whereas the mixtures, ANFO and Ammonal, decompose at substantially lower temperatures. The present results also confirm the recently proposed phase IV-IV ′ transition above 17 GPa and provide new constraints for the melting and phase diagram of AN to 40 GPa and 400°C

  13. Phase diagram of the mean field model of simplicial gravity

    International Nuclear Information System (INIS)

    Bialas, P.; Burda, Z.; Johnston, D.

    1999-01-01

    We discuss the phase diagram of the balls in boxes model, with a varying number of boxes. The model can be regarded as a mean-field model of simplicial gravity. We analyse in detail the case of weights of the form p(q) = q -β , which correspond to the measure term introduced in the simplicial quantum gravity simulations. The system has two phases: elongated (fluid) and crumpled. For β ε (2, ∞) the transition between these two phases is first-order, while for β ε (1, 2) it is continuous. The transition becomes softer when β approaches unity and eventually disappears at β = 1. We then generalise the discussion to an arbitrary set of weights. Finally, we show that if one introduces an additional kinematic bound on the average density of balls per box then a new condensed phase appears in the phase diagram. It bears some similarity to the crinkled phase of simplicial gravity discussed recently in models of gravity interacting with matter fields

  14. Phase diagram of two-component bosons on an optical lattice

    International Nuclear Information System (INIS)

    Altman, Ehud; Hofstetter, Walter; Demler, Eugene; Lukin, Mikhail D

    2003-01-01

    We present a theoretical analysis of the phase diagram of two-component bosons on an optical lattice. A new formalism is developed which treats the effective spin interactions in the Mott and superfluid phases on the same footing. Using this new approach we chart the phase boundaries of the broken spin symmetry states up to the Mott to superfluid transition and beyond. Near the transition point, the magnitude of spin exchange can be very large, which facilitates the experimental realization of spin-ordered states. We find that spin and quantum fluctuations have a dramatic effect on the transition, making it first order in extended regions of the phase diagram. When each species is at integer filling, an additional phase transition may occur, from a spin-ordered insulator to a Mott insulator with no broken symmetries. We determine the phase boundaries in this regime and show that this is essentially a Mott transition in the spin sector

  15. Exact ground-state phase diagrams for the spin-3/2 Blume-Emery-Griffiths model

    International Nuclear Information System (INIS)

    Canko, Osman; Keskin, Mustafa; Deviren, Bayram

    2008-01-01

    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 J 0 and J<0, respectively, the conditions for the existence of uniform and intermediate phases have also been found

  16. ({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.

  17. Calculation of Fe-B-V ternary phase diagram

    Czech Academy of Sciences Publication Activity Database

    Homolová, V.; Kroupa, Aleš; Výrostková, A.

    2012-01-01

    Roč. 520, APR (2012), s. 30-35 ISSN 0925-8388 R&D Projects: GA ČR(CZ) GAP108/10/1908 Institutional support: RVO:68081723 Keywords : phase diagram * thermodynamic modelling Subject RIV: BJ - Thermodynamics Impact factor: 2.390, year: 2012

  18. Calculation of binary phase diagrams between the actinide elements, rare earth elements, and transition metal elements

    International Nuclear Information System (INIS)

    Selle, J.E.

    1992-01-01

    Attempts were made to apply the Kaufman method of calculating binary phase diagrams to the calculation of binary phase diagrams between the rare earths, actinides, and the refractory transition metals. Difficulties were encountered in applying the method to the rare earths and actinides, and modifications were necessary to provide accurate representation of known diagrams. To calculate the interaction parameters for rare earth-rare earth diagrams, it was necessary to use the atomic volumes for each of the phases: liquid, body-centered cubic, hexagonal close-packed, and face-centered cubic. Determination of the atomic volumes of each of these phases for each element is discussed in detail. In some cases, empirical means were necessary. Results are presented on the calculation of rare earth-rare earth, rare earth-actinide, and actinide-actinide diagrams. For rare earth-refractory transition metal diagrams and actinide-refractory transition metal diagrams, empirical means were required to develop values for the enthalpy of vaporization for rare earth elements and values for the constant (C) required when intermediate phases are present. Results of using the values determined for each element are presented

  19. Regularization dependence on phase diagram in Nambu–Jona-Lasinio model

    International Nuclear Information System (INIS)

    Kohyama, H.; Kimura, D.; Inagaki, T.

    2015-01-01

    We study the regularization dependence on meson properties and the phase diagram of quark matter by using the two flavor Nambu–Jona-Lasinio model. The model also has the parameter dependence in each regularization, so we explicitly give the model parameters for some sets of the input observables, then investigate its effect on the phase diagram. We find that the location or the existence of the critical end point highly depends on the regularization methods and the model parameters. Then we think that regularization and parameters are carefully considered when one investigates the QCD critical end point in the effective model studies

  20. Temperature-field phase diagram of extreme magnetoresistance.

    Science.gov (United States)

    Fallah Tafti, Fazel; Gibson, Quinn; Kushwaha, Satya; Krizan, Jason W; Haldolaarachchige, Neel; Cava, Robert Joseph

    2016-06-21

    The recent discovery of extreme magnetoresistance (XMR) in LaSb introduced lanthanum monopnictides as a new platform to study this effect in the absence of broken inversion symmetry or protected linear band crossing. In this work, we report XMR in LaBi. Through a comparative study of magnetotransport effects in LaBi and LaSb, we construct a temperature-field phase diagram with triangular shape that illustrates how a magnetic field tunes the electronic behavior in these materials. We show that the triangular phase diagram can be generalized to other topological semimetals with different crystal structures and different chemical compositions. By comparing our experimental results to band structure calculations, we suggest that XMR in LaBi and LaSb originates from a combination of compensated electron-hole pockets and a particular orbital texture on the electron pocket. Such orbital texture is likely to be a generic feature of various topological semimetals, giving rise to their small residual resistivity at zero field and subject to strong scattering induced by a magnetic field.

  1. Electron Number-Based Phase Diagram of Pr1 -xLaCex CuO4 -δ and Possible Absence of Disparity between Electron- and Hole-Doped Cuprate Phase Diagrams

    Science.gov (United States)

    Song, Dongjoon; Han, Garam; Kyung, Wonshik; Seo, Jeongjin; Cho, Soohyun; Kim, Beom Seo; Arita, Masashi; Shimada, Kenya; Namatame, Hirofumi; Taniguchi, Masaki; Yoshida, Y.; Eisaki, H.; Park, Seung Ryong; Kim, C.

    2017-03-01

    We performed annealing and angle resolved photoemission spectroscopy studies on electron-doped cuprate Pr1 -xLaCex CuO4 -δ (PLCCO). It is found that the optimal annealing condition is dependent on the Ce content x . The electron number (n ) is estimated from the experimentally obtained Fermi surface volume for x =0.10 , 0.15 and 0.18 samples. It clearly shows a significant and annealing dependent deviation from the nominal x . In addition, we observe that the pseudo-gap at hot spots is also closely correlated with n ; the pseudogap gradually closes as n increases. We established a new phase diagram of PLCCO as a function of n . Different from the x -based one, the new phase diagram shows similar antiferromagnetic and superconducting phases to those of hole doped ones. Our results raise a possibility for absence of disparity between the phase diagrams of electron- and hole-doped cuprates

  2. 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

    Conspectus Molecular crystals are chemists' solids in the sense that their structures and properties can be understood in terms of those of the constituent molecules merely perturbed by a crystalline environment. They form a large and important class of solids including ices of atmospheric species, drugs, explosives, and even some organic optoelectronic materials and supramolecular assemblies. Recently, surprisingly simple yet extremely efficient, versatile, easily implemented, and systematically accurate electronic structure methods for molecular crystals have been developed. The methods, collectively referred to as the embedded-fragment scheme, divide a crystal into monomers and overlapping dimers and apply modern molecular electronic structure methods and software to these fragments of the crystal that are embedded in a self-consistently determined crystalline electrostatic field. They enable facile applications of accurate but otherwise prohibitively expensive ab initio molecular orbital theories such as Møller-Plesset perturbation and coupled-cluster theories to a broad range of properties of solids such as internal energies, enthalpies, structures, equation of state, phonon dispersion curves and density of states, infrared and Raman spectra (including band intensities and sometimes anharmonic effects), inelastic neutron scattering spectra, heat capacities, Gibbs energies, and phase diagrams, while accounting for many-body electrostatic (namely, induction or polarization) effects as well as two-body exchange and dispersion interactions from first principles. They can fundamentally alter the role of computing in the studies of molecular crystals in the same way ab initio molecular orbital theories have transformed research practices in gas-phase physical chemistry and synthetic chemistry in the last half century. In this Account, after a brief summary of formalisms and algorithms, we discuss applications of these methods performed in our group as compelling

  3. 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.

  4. Use of isoconcentrational phase diagrams for prediction of amorphization of binary systems

    International Nuclear Information System (INIS)

    Lazarev, A.I.; Belashchenko, D.K.

    1992-01-01

    Based on the application of isoconcentrational diagrams of phase equilibria of liquid with solid solutions of various crystal structures the thermodynamic method was considered for prediction of concentration ranges of amorphization in binary systems.To confirm the applicability of the thermodynamic criterion in practice caclulations of phase diagrams were accomplished for complex binary eutectic systems (Hf-Be, Zr-Be) with the known concentration ranges of amorphization

  5. Phase diagram for interacting Bose gases

    International Nuclear Information System (INIS)

    Morawetz, K.; Maennel, M.; Schreiber, M.

    2007-01-01

    We propose a modified form of the inversion method in terms of a self-energy expansion to access the phase diagram of the Bose-Einstein transition. The dependence of the critical temperature on the interaction parameter is calculated. This is discussed with the help of a condition for Bose-Einstein condensation in interacting systems which follows from the pole of the T matrix in the same way as from the divergence of the medium-dependent scattering length. A many-body approximation consisting of screened ladder diagrams is proposed, which describes the Monte Carlo data more appropriately. The specific results are that a non-self-consistent T matrix leads to a linear coefficient in leading order of 4.7, the screened ladder approximation to 2.3, and the self-consistent T matrix due to the effective mass to a coefficient of 1.3 close to the Monte Carlo data

  6. Using reweighting and free energy surface interpolation to predict solid-solid phase diagrams

    Science.gov (United States)

    Schieber, Natalie P.; Dybeck, Eric C.; Shirts, Michael R.

    2018-04-01

    Many physical properties of small organic molecules are dependent on the current crystal packing, or polymorph, of the material, including bioavailability of pharmaceuticals, optical properties of dyes, and charge transport properties of semiconductors. Predicting the most stable crystalline form at a given temperature and pressure requires determining the crystalline form with the lowest relative Gibbs free energy. Effective computational prediction of the most stable polymorph could save significant time and effort in the design of novel molecular crystalline solids or predict their behavior under new conditions. In this study, we introduce a new approach using multistate reweighting to address the problem of determining solid-solid phase diagrams and apply this approach to the phase diagram of solid benzene. For this approach, we perform sampling at a selection of temperature and pressure states in the region of interest. We use multistate reweighting methods to determine the reduced free energy differences between T and P states within a given polymorph and validate this phase diagram using several measures. The relative stability of the polymorphs at the sampled states can be successively interpolated from these points to create the phase diagram by combining these reduced free energy differences with a reference Gibbs free energy difference between polymorphs. The method also allows for straightforward estimation of uncertainties in the phase boundary. We also find that when properly implemented, multistate reweighting for phase diagram determination scales better with the size of the system than previously estimated.

  7. Models with short- and long-range interactions: the phase diagram and the reentrant phase

    International Nuclear Information System (INIS)

    Dauxois, Thierry; Lori, Leonardo; Ruffo, Stefano; De Buyl, Pierre

    2010-01-01

    We study the phase diagram of two different Hamiltonians with competing local, nearest-neighbour, and mean-field couplings. The first example corresponds to the HMF Hamiltonian with an additional short-range interaction. The second example is a reduced Hamiltonian for dipolar layered spin structures, with a new feature with respect to the first example: the presence of anisotropies. The two examples are solved in both the canonical and the microcanonical ensemble using a combination of the min–max method with the transfer operator method. The phase diagrams present typical features of systems with long-range interactions: ensemble inequivalence, negative specific heat and temperature jumps. Moreover, for a given range of parameters, we report the signature of phase reentrance. This can also be interpreted as the presence of azeotropy with the creation of two first-order phase transitions with ensemble inequivalence, as one parameter is varied continuously

  8. A metastable HCP intermetallic phase in Cu-Al bilayer films

    Energy Technology Data Exchange (ETDEWEB)

    Cha, Limei

    2006-07-01

    obtain the temperature range in which the HCP metastable phase will be stable. According to the XRD measurements, it is found that the metastable HCP phase exists below 120 C. (orig.)

  9. Monte Carlo study of the phase diagram for the two-dimensional Z(4) model

    International Nuclear Information System (INIS)

    Carneiro, G.M.; Pol, M.E.; Zagury, N.

    1982-05-01

    The phase diagram of the two-dimensional Z(4) model on a square lattice is determined using a Monte Carlo method. The results of this simulation confirm the general features of the phase diagram predicted theoretically for the ferromagnetic case, and show the existence of a new phase with perpendicular order. (Author) [pt

  10. Structures, phase stabilities, and electrical potentials of Li-Si battery anode materials

    KAUST Repository

    Tipton, William W.

    2013-05-28

    The Li-Si materials system holds promise for use as an anode in Li-ion battery applications. For this system, we determine the charge capacity, voltage profiles, and energy storage density solely by ab initio methods without any experimental input. We determine the energetics of the stable and metastable Li-Si phases likely to form during the charging and discharging of a battery. Ab initio molecular dynamics simulations are used to model the structure of amorphous Li-Si as a function of composition, and a genetic algorithm coupled to density-functional theory searches the Li-Si binary phase diagram for small-cell, metastable crystal structures. Calculations of the phonon densities of states using density-functional perturbation theory for selected structures determine the importance of vibrational, including zero-point, contributions to the free energies. The energetics and local structural motifs of these metastable Li-Si phases closely resemble those of the amorphous phases, making these small unit cell crystal phases good approximants of the amorphous phase for use in further studies. The charge capacity is estimated, and the electrical potential profiles and the energy density of Li-Si anodes are predicted. We find, in good agreement with experimental measurements, that the formation of amorphous Li-Si only slightly increases the anode potential. Additionally, the genetic algorithm identifies a previously unreported member of the Li-Si binary phase diagram with composition Li5Si2 which is stable at 0 K with respect to previously known phases. We discuss its relationship to the partially occupied Li7Si3 phase. © 2013 American Physical Society.

  11. Phase diagram of Fe1-xCox ultrathin film

    International Nuclear Information System (INIS)

    Fridman, Yu.A.; Klevets, Ph.N.; Voytenko, A.P.

    2008-01-01

    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. Cu–Ni nanoalloy phase diagram – Prediction and experiment

    Czech Academy of Sciences Publication Activity Database

    Sopoušek, J.; Vřešťál, J.; Pinkas, J.; Brož, P.; Buršík, Jiří; Stýskalík, A.; Škoda, D.; Zobač, O.; Lee, J.

    2014-01-01

    Roč. 45, June (2014), s. 33-39 ISSN 0364-5916 Institutional support: RVO:68081723 Keywords : nanoalloy * phase diagram * thermodynamic modeling Subject RIV: BJ - Thermodynamics Impact factor: 1.370, year: 2014

  13. Exploration of the phase diagram of liquid water in the low-temperature metastable region using synthetic fluid inclusions

    DEFF Research Database (Denmark)

    Qiu, Chen; Krüger, Yves; Wilke, Max

    2016-01-01

    water with a density of 0.921 kg/m3 remains in a homogeneous state during cooling down to the temperaure of −30.5 °C, where it is transformed into ice whose density corresponds to zero pressure. iii) ice melting. Ice melting temperatures of up to 6.8 °C were measured in absence of the vapour bubble, i......We present new experimental data of the low-temperature metastable region of liquid water derived from high-density synthetic fluid inclusions (996−916 kg/m3) in quartz. Microthermometric measurements include: i) Prograde (upon heating) and retrograde (upon cooling) liquid-vapour homogenisation. We...

  14. The QCD Phase Diagram: Large Nc, Quarkyonic Matter and the Triple Point

    International Nuclear Information System (INIS)

    McLerran, L.

    2010-01-01

    I discuss the phase diagram of QCD in the large N c limit. Qarkyonic Matter is described. The properties of QCD matter as measured in the abundance of produced particles are shown to be consistent with this phase diagram. A possible triple point of Hadronic Matter, Deconfined Matter and Quarkyonic Matter is shown to explain various behaviors of ratios of particle abundances seen in CERN fixed target experiments. (author)

  15. Pseudo-ternary phase diagram in the Na2O-Na2O2-NaOH system

    International Nuclear Information System (INIS)

    Saito, Jun-ichi; Tendo, Masayuki; Aoto, Kazumi

    1997-10-01

    Generally, the phase diagrams are always used to understand the present state of compounds at certain temperature. In order to understand the corrosion behavior of structural material for FBR by main sodium compounds (Na 2 O, Na 2 O 2 and NaOH), it is very important to comprehend the phase diagrams of their compounds. However, only Na 2 O-NaOH pseudo-binary phase diagram had been investigated previously in this system. There is no study of other pseudo-binary or ternary phase diagrams in the Na 2 O-Na 2 O 2 -NaOH system. In this study, in order to clarify the present states of their compounds at certain temperatures, the pseudo-binary and ternary phase diagrams in the Na 2 O-Na 2 O 2 -NaOH system were prepared. A series of thermal analyses with binary and ternary component system has been carried out using the differential scanning calorimetry (DSC). The liquidus temperature and ternary eutectic temperatures were confirmed by these measurements. The beneficial indications for constructing phase diagrams were obtained from these experiments. On the basis of these results, the interaction parameters between compounds which were utilized for the Thermo-Calc calculation were optimized. Thermo-Calc is one of thermodynamic calculation software. Consequently the accurate pseudo-binary and ternary phase diagrams were indicated using the optimized parameters. (author)

  16. Phase diagram and transport properties for hydrogen-helium fluid planets

    International Nuclear Information System (INIS)

    Stevenson, D.J.; Salpeter, E.E.

    1977-01-01

    Hydrogen and helium are the major constituents of Jupiter and Saturn, and phase transitions can have important effects on the planetary structure. In this paper, the relevant phase diagrams and microscopic transport properties are analyzed in detail. The following paper (Paper II) applies these results to the evolution and present dynamic structure of the Jovian planets.Pure hydrogen is first discussed, especially the nature of the molecular-metallic transition and the melting curves for the two phases. It is concluded that at the temperatures and pressures of interest (Tapprox. =10 4 K, Papprox. =1--10 Mbar), both phases are fluid, but the transition between them might nevertheless be first-order. The insulator-metal transition in helium occurs at a much higher pressure (approx.70 Mbars) and is not of interest.The phase diagrams for both molecular and metallic hydrogen-helium mixtures are discussed. In the metallic mixture, calculations indicate a miscibility gap for T9 or approx. =10 4 K. Immiscibility in the molecular mixture is more difficult to predict but almost certainly occurs at much lower temperatures. A fluid-state model is constructed which predicts the likely topology of the three-dimensional phase diagram. The greater solubility of helium in the molecular phase leads to the prediction that the He/H mass ratio is typically twice as large in the molecular phase as in the coexisting metallic phase. Under these circumstances a ''density inversion'' is possible in which the molecular phase becomes more dense than the metallic phase.The partitioning of minor constituents is also considered: The deuterium/hydrogen mass ratio is essentially the same for all coexisting hydrogen-helium phases, at least for T> or approx. =5000 K. The partitioning of H 2 O, CH 4 , and NH 3 probably favors the molecular (or helium-rich) phase. Substances with high conduction electron density (e.g., Al) may partition into the metallic phase

  17. Bicontinuous Phases in Diblock Copolymer/Homopolymer Blends: Simulation and Self-Consistent Field Theory

    KAUST Repository

    Martínez-Veracoechea, Francisco J.

    2009-03-10

    A combination of particle-based simulations and self-consistent field theory (SCFT) is used to study the stabilization of multiple ordered bicontinuous phases in blends of a diblock copolymer (DBC) and a homopolymer. The double-diamond phase (DD) and plumber\\'s nightmare phase (P) were spontaneously formed in the range of homopolymer volume fraction simulated via coarse-grained molecular dynamics. To the best of our knowledge, this is the first time that such phases have been obtained in continuum-space molecular simulations of DBC systems. Though tentative phase boundaries were delineated via free-energy calculations, macrophase separation could not be satisfactorily assessed within the framework of particle-based simulations. Therefore, SCFT was used to explore the DBC/homopolymer phase diagram in more detail, showing that although in many cases two-phase coexistence of a DBC-rich phase and a homopolymer-rich phase does precede the stability of complex bicontinuous phases the DD phase can be stable in a relatively wide region of the phase diagram. Whereas the P phase was always metastable with respect to macrophase separation under the thermodynamic conditions explored with SCFT, it was sometimes nearly stable, suggesting that full stability could be achieved in other unexplored regions of parameter space. Moreover, even the predicted DD- and P-phase metastability regions were located significantly far from the spinodal line, suggesting that these phases could be observed in experiments as "long-lived" metastable phases under those conditions. This conjecture is also consistent with large-system molecular dynamics simulations that showed that the time scale of mesophase formation is much faster than that of macrophase separation. © 2009 American Chemical Society.

  18. The phase diagram of ammonium nitrate

    Science.gov (United States)

    Chellappa, Raja S.; Dattelbaum, Dana M.; Velisavljevic, Nenad; Sheffield, Stephen

    2012-08-01

    The pressure-temperature (P-T) phase diagram of ammonium nitrate (AN) [NH4NO3] has been determined using synchrotron x-ray diffraction (XRD) and Raman spectroscopy measurements. Phase boundaries were established by characterizing phase transitions to the high temperature polymorphs during multiple P-T measurements using both XRD and Raman spectroscopy measurements. At room temperature, the ambient pressure orthorhombic (Pmmn) AN-IV phase was stable up to 45 GPa and no phase transitions were observed. AN-IV phase was also observed to be stable in a large P-T phase space. The phase boundaries are steep with a small phase stability regime for high temperature phases. A P-V-T equation of state based on a high temperature Birch-Murnaghan formalism was obtained by simultaneously fitting the P-V isotherms at 298, 325, 446, and 467 K, thermal expansion data at 1 bar, and volumes from P-T ramping experiments. Anomalous thermal expansion behavior of AN was observed at high pressure with a modest negative thermal expansion in the 3-11 GPa range for temperatures up to 467 K. The role of vibrational anharmonicity in this anomalous thermal expansion behavior has been established using high P-T Raman spectroscopy.

  19. Metastable Structural Phases of Metals in Columns IVB to Vib, and Rows 4 TO 6 OF the Periodic Table

    Science.gov (United States)

    Nnolim, Neme; Tyson, Trevor

    2002-03-01

    Total energy calculations as a function of strain along the direction have been carried out for the bcc metals V, Nb, Ta, Cr, Mo and W, and the hcp metals Ti, Zr and Hf, all in the block of the periodic table defined by columns IVB to VIB, and rows 4 to 6. Since strain along the direction corresponds to variation of the c lattice constant with respect to the a lattice constant, the total energy per unit cell has being calculated as a function of the c/a ratio. The highly accurate FP-LAPW (Full Potential Linearized Augmented Plane Wave) band structure method in the DFT (Density Functional Theory) formalism has been used for the calculations. In all cases except for the hcp column IVB elements, Zr, Hf and Ti, a metastable state was predicted from the calculations. Electronic properties are computed for all structures and are correlated with electrical and mechanical properties of metastable phases that have been observed experimentally. Properties of metastable phases, which were predicted in this work but which as of yet have not been observed experimentally, have also been predicted. Special attention is paid to the phases of tantalum and calculated transport properties are used to show that the observed high resistivity of the beta phase of tantalum relative to the alpha bcc phase cannot be explained solely by simple tetragonal distortions of the bcc phase.

  20. A few proofs for nonexistence of the metastable states

    International Nuclear Information System (INIS)

    Blazjevski, Atanas

    2007-01-01

    This paper is the bigger part of one until now unpublished author's work, whose title is 'A few proofs for nonexistence of the metastable states'. Because of a big volume of the work, the problems of supersaturated (metastable) steam which appears at the following of slightly, superheated, saturated or wet steam in the convergent and Laval nozzles will be discussed in the main. This steam is mentioned in the literature as one between of the strongest proofs for existence of metastable states in the substances. In this work the steam is not one -phase gaseous metastable steam, as it was thought until now, but yat it is nonequilibrium wet steam in which during the expanding process in the nozzles extreme small particles condensate, consisted of two, three or only few agglomerated molecules are formed which stay in heat, mechanical and internal nonequilibrium with the rest of the expanding gaseous phase of the steam. It means, that this steam, which is called a supersaturated or metastable steam, in fact does not exist in reality because it is nothing else but only nonequilibrium wet steam consisted of tho phases: the expanding gaseous phase of the steam in the nozzle and the mentioned small and nonequilibrium particles condensate which are formed there...

  1. Ti α - ω phase transformation and metastable structure, revealed by the solid-state nudged elastic band method

    Science.gov (United States)

    Zarkevich, Nikolai; Johnson, Duane D.

    Titanium is on of the four most utilized structural metals, and, hence, its structural changes and potential metastable phases under stress are of considerable importance. Using DFT+U combined with the generalized solid-state nudged elastic band (SS-NEB) method, we consider the pressure-driven transformation between Ti α and ω phases, and find an intermediate metastable body-centered orthorhombic (bco) structure of lower density. We verify its stability, assess the phonons and electronic structure, and compare computational results to experiment. Interestingly, standard density functional theory (DFT) yields the ω phase as the Ti ground state, in contradiction to the observed α phase at low pressure and temperature. We correct this by proper consideration of the strongly correlated d-electrons, and utilize DFT+U method in the SS-NEB to obtain the relevant transformation pathway and structures. We use methods developed with support by the U.S. Department of Energy (DE-FG02-03ER46026 and DE-AC02-07CH11358). Ames Laboratory is operated for the DOE by Iowa State University under Contract DE-AC02-07CH11358.

  2. From MIPS to Vicsek: A comprehensive phase diagram for self-propelled rods

    Science.gov (United States)

    Shi, Xiaqing

    Self-propelled rods interacting by volume exclusion is one of the simplest active matter systems. Despite years of effort, no comprehensive picture of their phase diagram is available. Furthermore, results on explicit rods are so far largely disconnected from those obtained on the relatively better understood cases of motility induced phase separation (MIPS) of (usually) isotropic active particles, and from our current knowledge of Vicsek-style aligning point particles. In this talk, I will present a complete phase diagram of a generic model of self-propelled rods and show how it is connected to both MIPS and Vicsek worlds.

  3. Dynamic phase transition in the kinetic spin-32 Blume-Capel model: Phase diagrams in the temperature and crystal-field interaction plane

    International Nuclear Information System (INIS)

    Keskin, Mustafa; Canko, Osman; Deviren, Bayram

    2007-01-01

    We analyze, within a mean-field approach, the stationary states of the kinetic spin-32 Blume-Capel (BC) model by the Glauber-type stochastic dynamics and subject to a time-dependent oscillating external magnetic field. The dynamic phase transition (DPT) points are obtained by investigating the behavior of the dynamic magnetization as a function of temperature and as well as calculating the Liapunov exponent. Phase diagrams are constructed in the temperature and crystal-field interaction plane. We find five fundamental types of phase diagrams for the different values of the reduced magnetic field amplitude parameter (h) in which they present a disordered, two ordered phases and the coexistences phase regions. The phase diagrams also exhibit a dynamic double-critical end point for 0 5.06

  4. Phase diagram study of a dimerized spin-S zig–zag ladder

    International Nuclear Information System (INIS)

    Matera, J M; Lamas, C A

    2014-01-01

    The phase diagram of a frustrated spin-S zig–zag ladder is studied through different numerical and analytical methods. We show that for arbitrary S, there is a family of Hamiltonians for which a fully-dimerized state is an exact ground state, being the Majumdar–Ghosh point for a particular member of the family. We show that the system presents a transition between a dimerized phase to a Néel-like phase for S = 1/2, and spiral phases can appear for large S. The phase diagram is characterized by means of a generalization of the usual mean field approximation. The novelty in the present implementation is to consider the strongest coupled sites as the unit cell. The gap and the excitation spectrum is analyzed through the random phase approximation. Also, a perturbative treatment to obtain the critical points is discussed. Comparisons of the results with numerical methods like the Density Matrix Renormalization Group are also presented. (paper)

  5. How little data is enough? Phase-diagram analysis of sparsity-regularized X-ray computed tomography.

    Science.gov (United States)

    Jørgensen, J S; Sidky, E Y

    2015-06-13

    We introduce phase-diagram analysis, a standard tool in compressed sensing (CS), to the X-ray computed tomography (CT) community as a systematic method for determining how few projections suffice for accurate sparsity-regularized reconstruction. In CS, a phase diagram is a convenient way to study and express certain theoretical relations between sparsity and sufficient sampling. We adapt phase-diagram analysis for empirical use in X-ray CT for which the same theoretical results do not hold. We demonstrate in three case studies the potential of phase-diagram analysis for providing quantitative answers to questions of undersampling. First, we demonstrate that there are cases where X-ray CT empirically performs comparably with a near-optimal CS strategy, namely taking measurements with Gaussian sensing matrices. Second, we show that, in contrast to what might have been anticipated, taking randomized CT measurements does not lead to improved performance compared with standard structured sampling patterns. Finally, we show preliminary results of how well phase-diagram analysis can predict the sufficient number of projections for accurately reconstructing a large-scale image of a given sparsity by means of total-variation regularization.

  6. P-T-x phase diagrams of MeF-UF4(Me=Li-Cs) systems

    International Nuclear Information System (INIS)

    Korenev, Yu.M.; Rykov, A.N.; Varkov, M.V.; Novoselova, A.V.

    1988-01-01

    Vapor composition and general pressure at three-phase equilibria in the MeF-UF 4 (Me=Li-Cs) systems are calculated using the values of independent component activities obtained earlier together with the data on fusibility diagrams. P-T and T-x projections of phase diagrams of these systems are constructed

  7. Chemically exfoliated Mo S2 layers: Spectroscopic evidence for the semiconducting nature of the dominant trigonal metastable phase

    Science.gov (United States)

    Pal, Banabir; Singh, Anjali; Sharada, G.; Mahale, Pratibha; Kumar, Abhinav; Thirupathaiah, S.; Sezen, H.; Amati, M.; Gregoratti, Luca; Waghmare, Umesh V.; Sarma, D. D.

    2017-11-01

    A metastable trigonal phase, existing only as small patches on a chemically exfoliated few-layered, thermodynamically stable 1 H phase of Mo S2 , is believed to critically influence the properties of Mo S2 -based devices. The electronic structure of this metastable phase is little understood in the absence of a direct experimental investigation of its electronic properties, complicated further by conflicting claims from theoretical investigations. We address this issue by investigating the electronic structure of this minority phase in chemically exfoliated Mo S2 few-layered systems by enhancing its contributions with the use of highly spatially resolved (≤120 nm resolution) photoemission spectroscopy and Raman spectroscopy in conjunction with state-of-the-art electronic structure calculations. Based on these results, we establish that the ground state of this phase, arrived at by the chemical exfoliation of Mo S2 using the usual Li intercalation technique, is a small gap (˜90 ±40 meV ) semiconductor in contrast to most claims in the literature; we also identify the specific trigonal structure it has among many suggested ones.

  8. Phase Diagrams of the Aqueous Two-Phase Systems of Poly(ethylene glycol/Sodium Polyacrylate/Salts

    Directory of Open Access Journals (Sweden)

    Adalberto Pessoa Junior

    2011-03-01

    Full Text Available Aqueous two-phase systems consisting of polyethylene glycol (PEG, sodium polyacrylate (NaPAA, and a salt have been studied. The effects of the polymer size, salt type (NaCl, Na2SO4, sodium adipate and sodium azelate and salt concentrations on the position of the binodal curve were investigated. The investigated PEG molecules had a molar mass of 2,000 to 8,000 g/mol, while that of NaPAA was 8,000 g/mol. Experimental phase diagrams, and tie lines and calculated phase diagrams, based on Flory-Huggins theory of polymer solutions are presented. Due to strong enthalpic and entropic balancing forces, the hydrophobicity of the added salt has a strong influence on the position of the binodal, which could be reproduced by model calculations.

  9. 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

  10. Phase diagram of Pr-P system

    International Nuclear Information System (INIS)

    Mironov, K.E.

    1981-01-01

    An area of the Pr-P system, adjoining to the Pr ordinate, is plotted up by the DTA method. Presence of P solid solution in Pr is established. Data on thermal stability of PrP, PrP 2 , PrP 5 and PrP 7 are generalized. The diagram of phase transformations in Pr-P system is plotted up proceeding from the whole complex of the data, presented. A supposition is made on a possible formation of solid solutions between the highest polyphosphide and phosphorus [ru

  11. First-Order Transitions and the Magnetic Phase Diagram of CeSb

    DEFF Research Database (Denmark)

    Lebech, Bente; Clausen, Kurt Nørgaard; Vogt, O.

    1980-01-01

    might exist in the magnetic phase diagram of CeSb at 16K for a field of approximately 0.3 T. The present study concludes that the transitions from the paramagnetic to the magnetically ordered states are of first order for fields below 0.8 T. Within the experimental accuracy no change has been observed......The high-temperature (14-17K) low-magnetic field (0-0.8 T) region of the phase diagram of the anomalous antiferromagnet CeSb has been reinvestigated by neutron diffraction in an attempt to locate a possible tricritical point. Previous neutron diffraction studies indicated that a tricritical point...

  12. Pseudo-critical point in anomalous phase diagrams of simple plasma models

    Science.gov (United States)

    Chigvintsev, A. Yu; Iosilevskiy, I. L.; Noginova, L. Yu

    2016-11-01

    Anomalous phase diagrams in subclass of simplified (“non-associative”) Coulomb models is under discussion. The common feature of this subclass is absence on definition of individual correlations for charges of opposite sign. It is e.g. modified OCP of ions on uniformly compressible background of ideal Fermi-gas of electrons OCP(∼), or a superposition of two non-ideal OCP(∼) models of ions and electrons etc. In contrast to the ordinary OCP model on non-compressible (“rigid”) background OCP(#) two new phase transitions with upper critical point, boiling and sublimation, appear in OCP(∼) phase diagram in addition to the well-known Wigner crystallization. The point is that the topology of phase diagram in OCP(∼) becomes anomalous at high enough value of ionic charge number Z. Namely, the only one unified crystal- fluid phase transition without critical point exists as continuous superposition of melting and sublimation in OCP(∼) at the interval (Z 1 points at both boundary values Z = Z 1 ≈ 35.5 and Z = Z 2 ≈ 40.0. It should be stressed that critical isotherm is exactly cubic in both these pseudo-critical points. In this study we have improved our previous calculations and utilized more complicated model components equation of state provided by Chabrier and Potekhin (1998 Phys. Rev. E 58 4941).

  13. The phase diagram of solid hydrogen at high pressure: A challenge for first principles calculations

    Science.gov (United States)

    Azadi, Sam; Foulkes, Matthew

    2015-03-01

    We present comprehensive results for the high-pressure phase diagram of solid hydrogen. We focus on the energetically most favorable molecular and atomic crystal structures. To obtain the ground-state static enthalpy and phase diagram, we use semi-local and hybrid density functional theory (DFT) as well as diffusion quantum Monte Carlo (DMC) methods. The closure of the band gap with increasing pressure is investigated utilizing quasi-particle many-body calculations within the GW approximation. The dynamical phase diagram is calculated by adding proton zero-point energies (ZPE) to static enthalpies. Density functional perturbation theory is employed to calculate the proton ZPE and the infra-red and Raman spectra. Our results clearly demonstrate the failure of DFT-based methods to provide an accurate static phase diagram, especially when comparing insulating and metallic phases. Our dynamical phase diagram obtained using fully many-body DMC calculations shows that the molecular-to-atomic phase transition happens at the experimentally accessible pressure of 374 GPa. We claim that going beyond mean-field schemes to obtain derivatives of the total energy and optimize crystal structures at the many-body level is crucial. This work was supported by the UK engineering and physics science research council under Grant EP/I030190/1, and made use of computing facilities provided by HECTOR, and by the Imperial College London high performance computing centre.

  14. Ferromagnetic quantum criticality: New aspects from the phase diagram of LaCrGe3

    Science.gov (United States)

    Taufour, Valentin; Kaluarachchi, Udhara S.; Bud'ko, Sergey L.; Canfield, Paul C.

    2018-05-01

    Recent theoretical and experimental studies have shown that ferromagnetic quantum criticality is always avoided in clean systems. Two possibilities have been identified. In the first scenario, the ferromagnetic transition becomes of the first order at a tricritical point before being suppressed. A wing structure phase diagram is observed indicating the possibility of a new type of quantum critical point under magnetic field. In a second scenario, a transition to a modulated magnetic phase occurs. Our recent studies on the compound LaCrGe3 illustrate a third scenario where not only a new magnetic phase occurs, but also a change of order of the transition at a tricritical point leading to a wing-structure phase diagram. Careful experimental study of the phase diagram near the tricritical point also illustrates new rules near this type of point.

  15. Uhlenbeck-Ford model: Phase diagram and corresponding-states analysis

    Science.gov (United States)

    Paula Leite, Rodolfo; Santos-Flórez, Pedro Antonio; de Koning, Maurice

    2017-09-01

    Using molecular dynamics simulations and nonequilibrium thermodynamic-integration techniques we compute the Helmholtz free energies of the body-centered-cubic (bcc), face-centered-cubic (fcc), hexagonal close-packed, and fluid phases of the Uhlenbeck-Ford model (UFM) and use the results to construct its phase diagram. The pair interaction associated with the UFM is characterized by an ultrasoft, purely repulsive pair potential that diverges logarithmically at the origin. We find that the bcc and fcc are the only thermodynamically stable crystalline phases in the phase diagram. Furthermore, we report the existence of two reentrant transition sequences as a function of the number density, one featuring a fluid-bcc-fluid succession and another displaying a bcc-fcc-bcc sequence near the triple point. We find strong resemblances to the phase behavior of other soft, purely repulsive systems such as the Gaussian-core model (GCM), inverse-power-law, and Yukawa potentials. In particular, we find that the fcc-bcc-fluid triple point and the phase boundaries in its vicinity are in good agreement with the prediction supplied by a recently proposed corresponding-states principle [J. Chem. Phys. 134, 241101 (2011), 10.1063/1.3605659; Europhys. Lett. 100, 66004 (2012), 10.1209/0295-5075/100/66004]. The particularly strong resemblance between the behavior of the UFM and GCM models are also discussed.

  16. Highly Accurate Calculations of the Phase Diagram of Cold Lithium

    Science.gov (United States)

    Shulenburger, Luke; Baczewski, Andrew

    The phase diagram of lithium is particularly complicated, exhibiting many different solid phases under the modest application of pressure. Experimental efforts to identify these phases using diamond anvil cells have been complemented by ab initio theory, primarily using density functional theory (DFT). Due to the multiplicity of crystal structures whose enthalpy is nearly degenerate and the uncertainty introduced by density functional approximations, we apply the highly accurate many-body diffusion Monte Carlo (DMC) method to the study of the solid phases at low temperature. These calculations span many different phases, including several with low symmetry, demonstrating the viability of DMC as a method for calculating phase diagrams for complex solids. Our results can be used as a benchmark to test the accuracy of various density functionals. This can strengthen confidence in DFT based predictions of more complex phenomena such as the anomalous melting behavior predicted for lithium at high pressures. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. DOE's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  17. Experiments on state selection and Penning ionisation with fast metastable rare gas atoms

    International Nuclear Information System (INIS)

    Kroon, J.P.C.

    1985-01-01

    This thesis describes experiments with metastable He/Ne atoms. The experiments are performed in a crossed beam machine. Two different sources are used for the production of metastable atoms: a source for the production of metastable atoms in the thermal energy range and a hollow cathode arc for the production of metastable atoms in the superthermal energy range (1-7 eV). The progress made in the use of the hollow cathode arc is described as well as the experimental set-up. The rare gas energy-level diagram is characterized by two metastable levels. By optical pumping it is possible to select a single metastable level, both for He and Ne. For the case of He this is done by a recently built He quenchlamp which selectively quenches the metastable 2 1 S level population. In the thermal energy range the quenching is complete; in the superthermal energy range the 2 1 S level population is only partly quenched. For the optical pumping of Ne* atoms a cw dye laser is used. New experiments have been started on the measurement, in a crossed beam machine, of the fluorescence caused by inelastic collisions where metastable atoms are involved. The He* + Ne system is used as a pilot study for these experiments. The He-Ne laser is based on this collision system. (Auth.)

  18. Thermodynamic study of CVD-ZrO{sub 2} phase diagrams

    Energy Technology Data Exchange (ETDEWEB)

    Torres-Huerta, A.M., E-mail: atorresh@ipn.m [Research Center for Applied Science and Advanced Technology, Altamira-IPN, Altamira C.P.89600 Tamaulipas (Mexico); Vargas-Garcia, J.R. [Dept of Metallurgical Eng., ESIQIE-IPN, Mexico 07300 D.F. (Mexico); Dominguez-Crespo, M.A. [Research Center for Applied Science and Advanced Technology, Altamira-IPN, Altamira C.P.89600 Tamaulipas (Mexico); Romero-Serrano, J.A. [Dept of Metallurgical Eng., ESIQIE-IPN, Mexico 07300 D.F. (Mexico)

    2009-08-26

    Chemical vapor deposition (CVD) of zirconium oxide (ZrO{sub 2}) from zirconium acetylacetonate Zr(acac){sub 4} has been thermodynamically investigated using the Gibbs' free energy minimization method and the FACTSAGE program. Thermodynamic data Cp{sup o}, DELTAH{sup o} and S{sup o} for Zr(acac){sub 4} have been estimated using the Meghreblian-Crawford-Parr and Benson methods because they are not available in the literature. The effect of deposition parameters, such as temperature and pressure, on the extension of the region where pure ZrO{sub 2} can be deposited was analyzed. The results are presented as calculated CVD stability diagrams. The phase diagrams showed two zones, one of them corresponds to pure monoclinic phase of ZrO{sub 2} and the other one corresponds to a mix of monoclinic phase of ZrO{sub 2} and graphite carbon.

  19. Temperature-dependent pitch and phase diagram for incommensurate XY spins in a slab geometry

    International Nuclear Information System (INIS)

    Collins, M.; Saslow, W.M.

    1996-01-01

    Strain-engineered Heisenberg antiferromagnets recently have been produced by controlling the layer thickness of MnSe/ZnTe superlattices. Neutron-scattering studies reveal a spiral that tends to untwist with increasing temperature. To simulate this system, we employ an XY model with nearest- and second-nearest neighbor antiferromagnetic interactions. The bulk mean-field phase diagram has four possible phases, for the full range of the exchange constants. Monte Carlo calculations are performed for a slab geometry, using an algorithm that allows the system to choose incommensurate boundary conditions. The phase diagram is constructed by monitoring the spiral pitch as a function of temperature for a range of exchange constants. For appropriate exchange constants, good agreement is obtained with experiment. From the mean-field phase diagram it appears that strain engineering an NaCl structure in a superlattice configuration might produce a type of spiral phase, and an associated antiferromagnetic-to-spiral phase transition. copyright 1996 The American Physical Society

  20. Studies on the phase diagram of Pb-Mo-O system

    International Nuclear Information System (INIS)

    Aiswarya, P.M.; Ganesan, Rajesh; Gnanasekaran, T.

    2014-01-01

    Liquid lead and Lead-Bismuth Eutectic (LBE) alloy are considered as spallation target and coolant in the accelerator driven systems and as candidate coolant in advanced nuclear reactors. Corrosion of the structural steel components in these liquid metal coolants can be minimized by the insitu formation of passive oxide layer on the steel surface under controlled oxygen concentration. A detailed knowledge of phase diagrams of Pb-M-O and Bi-M-O (M = Fe, Cr, Mo) systems and data on thermochemical properties of the ternary compounds of these systems are required for better understanding of composition and stability of these passive oxide films. In the present work, studies have been carried out to establish the ternary phase diagram of Pb-Mo-O system

  1. Canonical phase diagrams of the 1D Falicov-Kimball model at T = O

    Science.gov (United States)

    Gajek, Z.; Jȩdrzejewski, J.; Lemański, R.

    1996-02-01

    The Falicov-Kimball model of spinless quantum electrons hopping on a 1-dimensional lattice and of immobile classical ions occupying some lattice sites, with only intrasite coupling between those particles, have been studied at zero temperature by means of well-controlled numerical procedures. For selected values of the unique coupling parameter U the restricted phase diagrams (based on all the periodic configurations of localized particles (ions) with period not greater than 16 lattice constants, typically) have been constructed in the grand-canonical ensemble. Then these diagrams have been translated into the canonical ensemble. Compared to the diagrams obtained in other studies our ones contain more details, in particular they give better insight into the way the mixtures of periodic phases are formed. Our study has revealed several families of new characteristic phases like the generalized most homogeneous and the generalized crenel phases, a first example of a structural phase transition and a tendency to build up an additional symmetry - the hole-particle symmetry with respect to the ions (electrons) only, as U decreases.

  2. The phase diagrams of a ferromagnetic thin film in a random magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Zaim, N.; Zaim, A., E-mail: ah_zaim@yahoo.fr; Kerouad, M., E-mail: m.kerouad@fs-umi.ac.ma

    2016-10-07

    In this paper, the magnetic properties and the phase diagrams of a ferromagnetic thin film with a thickness N in a random magnetic field (RMF) are investigated by using the Monte Carlo simulation technique based on the Metropolis algorithm. The effects of the RMF and the surface exchange interaction on the critical behavior are studied. A variety of multicritical points such as tricritical points, isolated critical points, and triple points are obtained. It is also found that the double reentrant phenomenon can appear for appropriate values of the system parameters. - Highlights: • Phase diagrams of a ferromagnetic thin film are examined by the Monte Carlo simulation. • The effect of the random magnetic field on the magnetic properties is studied. • Different types of the phase diagrams are obtained. • The dependence of the magnetization and susceptibility on the temperature are investigated.

  3. Stabilization of metastable tetragonal zirconia nanocrystallites by surface modification

    DEFF Research Database (Denmark)

    Nielsen, Mette Skovgaard; Almdal, Kristoffer; Lelieveld, A. van

    2011-01-01

    Metastable tetragonal zirconia nanocrystallites were studied in humid air and in water at room temperature (RT). A stabilizing effect of different surfactants on the tetragonal phase was observed. Furthermore, the phase stability of silanized metastable tetragonal zirconia nanocrystallites was te...... exposure to humidity. Only silanes and phosphate esters of these were able to stabilize the tetragonal phase in water. Even as small amounts of silanes as 0.25 silane molecule per nm2 are able to stabilize the tetragonal phase in water at RT. Aminopropyl trimethoxy silane and γ...

  4. High-pressure phase diagrams of liquid CO2 and N2

    Science.gov (United States)

    Boates, Brian; Bonev, Stanimir

    2011-06-01

    The phase diagrams of liquid CO2 and N2 have been investigated using first-principles theory. Both materials exhibit transitions to conducting liquids at high temperatures (T) and relatively modest pressures (P). Furthermore, both liquids undergo polymerization phase transitions at pressures comparable to their solid counterparts. The liquid phase diagrams have been divided into several regimes through a detailed analysis of changes in bonding, as well as structural and electronic properties for pressures and temperatures up to 200 GPa and 10 000 K, respectively. Similarities and differences between the high- P and T behavior of these fluids will be discussed. Calculations of the Hugoniot are in excellent agreement with available experimental data. Work supported by NSERC, LLNL, and the Killam Trusts. Prepared by LLNL under Contract DE-AC52-07NA27344.

  5. Phase diagram and tricritical behavior of an metamagnet in uniform and random fields

    International Nuclear Information System (INIS)

    Liang Yaqiu; Wei Guozhu; Xu Xiaojuan; Song Guoli

    2010-01-01

    A two-sublattice Ising metamagnet in both uniform and random fields is studied within the mean-field approach based on Bogoliubov's inequality for the Gibbs free energy. We show that the qualitative features of the phase diagrams are dependent on the parameters of the model and the uniform field values. The tricritical point and reentrant phenomenon can be observed on the phase diagram. The reentrance is due to the competition between uniform and random interactions.

  6. A proposed phase equilibrium diagram for Pt-Zr system

    International Nuclear Information System (INIS)

    Arias, D.E.; Gribaudo, L.

    1993-01-01

    A revision of the phase diagram of the Pt-Zr system is presented using up to date information from recent publications. The proposed change concerning the invariant transformation in the Pt-rich zone is supported by simplified thermodynamic evaluations. (author). 12 refs., 1 fig

  7. Quest for the QCD phase diagram in extreme environments

    Energy Technology Data Exchange (ETDEWEB)

    Fukushima, Kenji, E-mail: fuku@rk.phys.keio.ac.jp [Keio University, Department of Physics (Japan)

    2013-03-15

    We review the state-of-the-art status of the research on the phase diagram of QCD matter out of quarks and gluons. Our discussions particularly include the extreme environments such as the high temperature, the high baryon density, and the strong magnetic field.

  8. Polariton condensation phase diagram in wide-band-gap planar microcavities: GaN versus ZnO

    Science.gov (United States)

    Jamadi, O.; Réveret, F.; Mallet, E.; Disseix, P.; Médard, F.; Mihailovic, M.; Solnyshkov, D.; Malpuech, G.; Leymarie, J.; Lafosse, X.; Bouchoule, S.; Li, F.; Leroux, M.; Semond, F.; Zuniga-Perez, J.

    2016-03-01

    The polariton condensation phase diagram is compared in GaN and ZnO microcavities grown on mesa-patterned silicon substrate. Owing to a common platform, these microcavities share similar photonic properties with large quality factors and low photonic disorder, which makes it possible to determine the optimal spot diameter and to realize a thorough phase diagram study. Both systems have been investigated under the same experimental conditions. The experimental results and the subsequent analysis reveal clearly that longitudinal optical phonons have no influence in the thermodynamic region of the condensation phase diagram, while they allow a strong (slight) decrease of the polariton lasing threshold in the trade-off zone (kinetic region). Phase diagrams are compared with numerical simulations using Boltzmann equations, and are in satisfactory agreement. A lower polariton lasing threshold has been measured at low temperature in the ZnO microcavity, as is expected due to a larger Rabi splitting. This study highlights polariton relaxation mechanisms and their importance in polariton lasing.

  9. Pseudo-critical point in anomalous phase diagrams of simple plasma models

    International Nuclear Information System (INIS)

    Chigvintsev, A Yu; Iosilevskiy, I L; Noginova, L Yu

    2016-01-01

    Anomalous phase diagrams in subclass of simplified (“non-associative”) Coulomb models is under discussion. The common feature of this subclass is absence on definition of individual correlations for charges of opposite sign. It is e.g. modified OCP of ions on uniformly compressible background of ideal Fermi-gas of electrons OCP(∼), or a superposition of two non-ideal OCP(∼) models of ions and electrons etc. In contrast to the ordinary OCP model on non-compressible (“rigid”) background OCP(#) two new phase transitions with upper critical point, boiling and sublimation, appear in OCP(∼) phase diagram in addition to the well-known Wigner crystallization. The point is that the topology of phase diagram in OCP(∼) becomes anomalous at high enough value of ionic charge number Z . Namely, the only one unified crystal- fluid phase transition without critical point exists as continuous superposition of melting and sublimation in OCP(∼) at the interval ( Z 1 < Z < Z 2 ). The most remarkable is appearance of pseudo-critical points at both boundary values Z = Z 1 ≈ 35.5 and Z = Z 2 ≈ 40.0. It should be stressed that critical isotherm is exactly cubic in both these pseudo-critical points. In this study we have improved our previous calculations and utilized more complicated model components equation of state provided by Chabrier and Potekhin (1998 Phys. Rev. E 58 4941). (paper)

  10. Multicritical phase diagrams of the antiferromagnetic spin-3/2 Blume-Capel model

    Energy Technology Data Exchange (ETDEWEB)

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

    2006-04-24

    The antiferromagnetic spin-3/2 Blume-Capel model in an external magnetic field is investigated, and the phase diagrams are obtained in detail by using the cluster variation method. The model exhibits distinct critical regions, including the first-order, second-order and special points: two double critical points, a critical end point, a tricritical point and a zero-temperature critical point. The new phase diagram topology is also found that was not obtained previously. Comparison of the results with those of other studies on this, and closely related systems, is made.

  11. Multicritical phase diagrams of the antiferromagnetic spin-3/2 Blume-Capel model

    International Nuclear Information System (INIS)

    Keskin, Mustafa; Ali Pinar, M.; Erdinc, Ahmet; Canko, Osman

    2006-01-01

    The antiferromagnetic spin-3/2 Blume-Capel model in an external magnetic field is investigated, and the phase diagrams are obtained in detail by using the cluster variation method. The model exhibits distinct critical regions, including the first-order, second-order and special points: two double critical points, a critical end point, a tricritical point and a zero-temperature critical point. The new phase diagram topology is also found that was not obtained previously. Comparison of the results with those of other studies on this, and closely related systems, is made

  12. A new experimental phase diagram investigation of Cu-Sb.

    Science.gov (United States)

    Fürtauer, Siegfried; Flandorfer, Hans

    The binary system Cu-Sb is a constituent system that is studied in investigations of technically important ternary and quaternary alloy systems (e.g., casting alloys and lead-free solders). Although this binary system has been thoroughly investigated over the last century, there are still some uncertainties regarding its high-temperature phases. Thus, parts of its phase diagram have been drawn with dashed lines in reviews published in the literature. The aim of this work was to resolve these uncertainties in the current phase diagram of Cu-Sb by performing XRD, SEM-EDX, EPMA, and DTA. The results from thermal analysis agreed well with those given in the literature, although some modifications due to the invariant reaction temperatures were necessary. In particular, reactions located on the Cu-rich side of the nonquenchable high-temperature β phase (BiF 3 -type) left considerable scope for interpretation. Generally, the structural descriptions of the various binary phases given in the literature were verified. The range of homogeneity of the ε phase (Cu 3 Ti type) was found to be higher on the Sb-rich side. Most of the reaction temperatures were verified, but a few had to be revised, such as the eutectoid reaction [Formula: see text] at 440 °C (found to occur at 427 °C in this work) and the eutectoid reaction [Formula: see text] at 400 °C (found to occur at 440 °C in this work). Further phase transformations that had previously only been estimated were confirmed, and their characteristic temperatures were determined.

  13. 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.

  14. Dynamic phase transition in the kinetic spin-32 Blume-Capel model: Phase diagrams in the temperature and crystal-field interaction plane

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-06-15

    We analyze, within a mean-field approach, the stationary states of the kinetic spin-32 Blume-Capel (BC) model by the Glauber-type stochastic dynamics and subject to a time-dependent oscillating external magnetic field. The dynamic phase transition (DPT) points are obtained by investigating the behavior of the dynamic magnetization as a function of temperature and as well as calculating the Liapunov exponent. Phase diagrams are constructed in the temperature and crystal-field interaction plane. We find five fundamental types of phase diagrams for the different values of the reduced magnetic field amplitude parameter (h) in which they present a disordered, two ordered phases and the coexistences phase regions. The phase diagrams also exhibit a dynamic double-critical end point for 05.06.

  15. Magnetic phase diagram of Ce2Fe17 under high pressures in high magnetic fields

    International Nuclear Information System (INIS)

    Ishikawa, Fumihiro; Goto, Tsuneaki; Fujii, Hironobu

    2003-01-01

    The magnetization of Ce 2 Fe 17 was precisely measured under high pressures up to 1.2 GPa in magnetic fields up to 18 T. The magnetic phase diagram in the B-T plane is determined at 0, 0.3, 0.4, 0.6, 0.9 and 1.2 GPa. At 0 GPa, five magnetic phases exist and the application of high pressure produces two additional magnetic phases. The shape of the phase diagram changes drastically with increasing pressure

  16. Tight-binding calculation of Ti-Rh--type phase diagram

    International Nuclear Information System (INIS)

    Sluiter, M.; Turchi, P.; Fu Zezhong; de Fontaine, D.

    1988-01-01

    Tight-binding electronic band-structure calculations were combined with a free-energy expression from a statistical mechanical method called the cluster-variation method. The effective pair interactions used in the cluster-variation calculation were evaluated by the generalized perturbation method. Only d orbitals were included and the numbers of d electrons per atom were taken to be three for the pure A element and eight for the pure B. A phase diagram was constructed incorporating, for the first time, both fcc and bcc lattices and their simple-ordered superstructures. The calculated diagram agreed reasonably well with those determined empirically for Ti-Rh or Ti-Ir

  17. Phase diagrams of the ternary alloy with a single-ion anisotropy in the mean-field approximation

    International Nuclear Information System (INIS)

    Dely, J.; Bobak, A.

    2006-01-01

    The phase diagram of the AB p C 1-p ternary alloy consisting of Ising spins S A =32, S B =2, and S C =52 is investigated by the use of a mean-field theory based on the Bogoliubov inequality for the Gibbs free energy. The effect of the single-ion anisotropy on the phase diagrams is discussed by changing values of the parameters in the model Hamiltonian and comparison is made with the recently reported finite-temperature phase diagrams for the ternary alloy having spin S B =1

  18. A new stochastic cellular automaton model on traffic flow and its jamming phase transition

    International Nuclear Information System (INIS)

    Sakai, Satoshi; Nishinari, Katsuhiro; Iida, Shinji

    2006-01-01

    A general stochastic traffic cellular automaton (CA) model, which includes the slow-to-start effect and driver's perspective, is proposed in this paper. It is shown that this model includes well-known traffic CA models such as the Nagel-Schreckenberg model, the quick-start model and the slow-to-start model as specific cases. Fundamental diagrams of this new model clearly show metastable states around the critical density even when the stochastic effect is present. We also obtain analytic expressions of the phase transition curve in phase diagrams by using approximate flow-density relations at boundaries. These phase transition curves are in excellent agreement with numerical results

  19. Topological phase diagram of superconducting carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Milz, Lars; Marganska-Lyzniak, Magdalena; Grifoni, Milena [Institut I - Theoretische Physik Universitaet Regensburg (Germany)

    2016-07-01

    The topological superconducting phase diagram of superconducting carbon nanotubes is discussed. Under the assumption of a short-ranged pairing potential, there are two spin-singlet states: an s-wave and an exotic p + ip-wave that are possible because of the special structure of the honeycomb lattice. The consequences for the possible presence of Majorana edge states in carbon nanotubes are addressed. In particular, regions in the magnetic field-chemical potential plane possibly hosting localized Majorana modes are discussed.

  20. Gd5(SixGe1−x)4 system – updated phase diagram

    International Nuclear Information System (INIS)

    Melikhov, Yevgen; Hadimani, R.L.; Raghunathan, Arun

    2015-01-01

    Gd 5 (Si x Ge 1−x ) 4 for 0.41phase transition between the two. In this range, the magnetic moment vs. magnetic field (MH) isotherms measured just above the first order transition temperature carry information about all magnetic and structural transitions. Here, the Curie–Weiss law was applied to the paramagnetic portions of the MH isotherms which allowed identification of the second order magnetic phase transition temperature of the monoclinic phase, a region where the second order transition does not occur due to the existence of the first order transition. The calculated second order phase transition temperatures of the monoclinic phase were added to the existing phase diagram. The completed magnetic-structural phase diagram carries now all the information including the magnetic transition temperatures of both monoclinic and orthorhombic phases. It was also found that the magnetic transition temperature of the monoclinic phase and the first order transition temperature are interrelated. - Highlights: • Magnetocaloric Gd 5 (Si x Ge 1−x ) 4 for 0.41phase transition suppresses second order transition of monoclinic phase. • Curie–Weiss law and Arrott Plot technique were used to analyse M vs. H isotherms. • Second order phase transition temperatures of the monoclinic phase were estimated. • Magnetic-structural phase diagram Gd 5 (Si x Ge 1−x ) 4 for 0.41

  1. A metastable liquid melted from a crystalline solid under decompression

    Science.gov (United States)

    Lin, Chuanlong; Smith, Jesse S.; Sinogeikin, Stanislav V.; Kono, Yoshio; Park, Changyong; Kenney-Benson, Curtis; Shen, Guoyin

    2017-01-01

    A metastable liquid may exist under supercooling, sustaining the liquid below the melting point such as supercooled water and silicon. It may also exist as a transient state in solid-solid transitions, as demonstrated in recent studies of colloidal particles and glass-forming metallic systems. One important question is whether a crystalline solid may directly melt into a sustainable metastable liquid. By thermal heating, a crystalline solid will always melt into a liquid above the melting point. Here we report that a high-pressure crystalline phase of bismuth can melt into a metastable liquid below the melting line through a decompression process. The decompression-induced metastable liquid can be maintained for hours in static conditions, and transform to crystalline phases when external perturbations, such as heating and cooling, are applied. It occurs in the pressure-temperature region similar to where the supercooled liquid Bi is observed. Akin to supercooled liquid, the pressure-induced metastable liquid may be more ubiquitous than we thought.

  2. Experimental investigation of the Al-Y phase diagram

    International Nuclear Information System (INIS)

    Liu Shuhong; Du Yong; Xu Honghui; He Cuiyun; Schuster, Julius C.

    2006-01-01

    The Al-Y phase diagram has been reinvestigated with 16 key alloys over its whole composition range by means of differential thermal analysis, X-ray diffraction, optical microscopy, and scanning electron microscopy with energy dispersive X-ray techniques. The existence of five intermetallic phases, Al 3 Y, Al 2 Y, AlY, Al 2 Y 3 , and AlY 2 , has been confirmed. Al 2 Y and Al 2 Y 3 melt congruently at 1490 ± 2 and 1105 ± 2 deg. C, respectively. Al 3 Y, AlY, and AlY 2 are formed via the peritectic reactions L + Al 2 Y ↔ Al 3 Y at 980 ± 2 deg. C, L + Al 2 Y ↔ AlY at 1138 ± 2 deg. C, and L + Al 2 Y 3 ↔ AlY 2 at 977 ± 2 deg. C, respectively. Three eutectic reactions L ↔ (Al) + Al 3 Y at 637 ± 2 deg. C, L ↔ AlY + Al 2 Y 3 at 1081 ± 2 deg. C, and L ↔ AlY 2 + (αY) at 955 ± 2 deg. C , are observed. The previously reported Al 3 Y 5 , AlY 3 compounds were not found. A revised Al-Y phase diagram is presented mainly based on the present experimental results

  3. Silver nanoplates with ground or metastable structures obtained from template-free two-phase aqueous/organic synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Zhelev, Doncho V., E-mail: dontcho.jelev@nih.gov; Zheleva, Tsvetanka S. [Army Research Laboratory, 2800 Adelphi, Maryland 20783 (United States)

    2014-01-28

    Silver has unique electrical, catalytic, and plasmonic characteristics and has been widely sought for fabrication of nanostructures. The properties of silver nanostructures are intimately coupled to the structure of silver crystals. Two crystal structures are known for silver: the stable (ground) state cubic face centered 3C-Ag structure and the metastable hexagonal 4H-Ag structure. Recently, Chackraborty et al. [J. Phys.: Condens. Matter 23, 325401 (2011)] discovered a low density, highly reactive metastable hexagonal 2H-Ag structure accessible during electrodeposition of silver nanowires in porous anodic alumina templates. This 2H-Ag structure has enhanced electrical and catalytic characteristics. In the present work we report template-free synthesis of silver nanoplates with the metastable 2H-Ag crystal structure, which appears together with the ground 3C-Ag and the metastable 4H-Ag structures in a two-phase solution synthesis with citric acid as the capping agent. The capacity of citric acid to stabilize both the stable and the metastable structures is explained by its preferential binding to the close packed facets of Ag crystals, which are the (111) planes for 3C-Ag and the (0001) planes for 4H-Ag and 2H-Ag. Nanoplate morphology and structure are characterized using scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. The synthesized nanoplates have thickness from 15 to 17 nm and edge length from 1 to 10 μm. Transmission electron microscopy selected area electron diffraction is used to uniquely identify and distinguish between nanoplates with 2H-Ag or 4H-Ag or 3C-Ag structures.

  4. Formation of metastable and equilibrium phases in the decomposition of the β solid solution in Zr alloys

    International Nuclear Information System (INIS)

    Zakharova, M.I.; Kirov, S.A.; Khundzhua, A.G.

    1978-01-01

    The decomposition of the β solid solution is studied in Zr-Nb alloys with adding Mo, Al, V, Fe by the methods of electron microscopy and X-ray diffraction on single crystals. The intermetallic compounds forming during crystallization of the alloys do not influence the precipitation of the ω- and α-phases during ageing. In the local regions of foils prepared by electropolishing after ageing the formation of the metastable f.c.c. phase and in some cases the inverse transformation of two phase state to the parent phase is observed. (author)

  5. Steady state creep during metastable phase transition in Al-16 wt% Ag and Al-16 wt% Ag-0.1 wt% Zr alloys

    Energy Technology Data Exchange (ETDEWEB)

    Deaf, G.H.; Youssef, S.B.; Mahmoud, M.A. [Ain Shams Univ., Cairo (Egypt). Dept. of Physics

    1998-08-16

    The early stages of decomposition of Guinier-Preston zones (G.P. zones) in Al-16 wt% Ag and Al-16 wt% Ag-0.1 wt% Zr alloys were investigated through creep measurements and electron microscopy observations. It was found that the strengthening and softening of the alloys has been achieved during the formation of metastable phases (G.P. zones and {gamma}`-phase) in the ageing temperature range (428 to 498 K). TEM investigations confirmed that the addition of zirconium to the Al-Ag alloy accelerates the formation and coarsening of the metastable phases. The mean values of activation energy of both alloys were found to be equal to that quoted for precipitate-dislocation interactions. (orig.) 23 refs.

  6. From phase transitions to the topological renaissance. Comment on "Topodynamics of metastable brains" by Arturo Tozzi et al.

    Science.gov (United States)

    Somogyvári, Zoltán; Érdi, Péter

    2017-07-01

    The neural topodynamics theory of Tozzi et al. [13] has two main foci: metastable brain dynamics and the topological approach based on the Borsuk-Ulam theorem (BUT). Briefly, metastable brain dynamics theory hypothesizes that temporary stable synchronization and desynchronization of large number of individual dynamical systems, formed by local neural circuits, are responsible for coding of complex concepts in the brain and sudden changes of these synchronization patterns correspond to operational steps. But what dynamical network could form the substrate for this metastable dynamics, capable of entering into a combinatorially high number of metastable synchronization patterns and exhibit rapid transient changes between them? The general problem is related to the discrimination between ;Black Swans; and ;Dragon Kings;. While BSs are related to the theory of self-organized criticality, and suggests that high-impact extreme events are unpredictable, Dragon-kings are associated with the occurrence of a phase transition, whose emergent organization is based on intermittent criticality [9]. Widening the limits of predictability is one of the big open problems in the theory and practice of complex systems (Sect. 9.3 of Érdi [2]).

  7. Phase diagram of a modified Lennard-Jones system

    International Nuclear Information System (INIS)

    Sakagami, Takahiro; Fuchizaki, Kazuhiro

    2010-01-01

    The well-known Lennard-Jones potential is modified in such a way that it smoothly vanishes at a certain distance. A system whose interparticle interaction is given by such a potential is referred to as a modified Lennard-Jones system, and is served as a standard system describing simple solids and fluids. A phase diagram is determined based on the free energies obtained through thermodynamic integration.

  8. Thermodynamics and phase diagrams of the plutonium-uranium, uranium-zirconium, plutonium-zirconium and plutonium-uranium-zirconium systems

    International Nuclear Information System (INIS)

    Agarwal, R.; Venugopal, V.

    2004-05-01

    Thermodynamic and phase diagram data reported in literature for the binaries, Pu-U, Pu-Zr and U-Zr , were compiled and optimised to calculate Gibbs energies of all the binary phases of these systems. Lukas program was used to carry out these optimisations, where, thermodynamic and phase diagram data of all the binary phases of a binary system were optimised simultaneously. Gibbs energy sets thus calculated were used to compare our results with the experimental and calculated phase diagram and thermodynamic data reponed in the literature. The Gibbs energies of the binary systems were then compiled together to define Pu-U-Zr ternary system. (author)

  9. Magnetic phase diagram of a frustrated spin ladder

    Science.gov (United States)

    Sugimoto, Takanori; Mori, Michiyasu; Tohyama, Takami; Maekawa, Sadamichi

    2018-04-01

    Frustrated spin ladders show magnetization plateaux depending on the rung-exchange interaction and frustration defined by the ratio of first and second neighbor exchange interactions in each chain. This paper reports on its magnetic phase diagram. Using the variational matrix-product state method, we accurately determine phase boundaries. Several kinds of magnetization plateaux are induced by the frustration and the strong correlation among quasiparticles on a lattice. The appropriate description of quasiparticles and their relevant interactions are changed by a magnetic field. We find that the frustration differentiates the triplet quasiparticle from the singlet one in kinetic energy.

  10. Phase diagrams for systems Cu2S-AIIS (AII=Mg, Ca, Sr, Ba)

    International Nuclear Information System (INIS)

    Andreev, O.V.; Sikerina, N.V.; Solov'eva, A.V.

    2005-01-01

    By the methods of physicochemical analysis phase diagrams of Cu 2 S-A II S (A II =Mg, Ca, Sr, Ba) systems are studied. The system Cu 2 S-SrS is of eutectic type with eutectic coordinates 1095 K and 21.5 mol.% of SrS. Solubility of SrS in Cu 2 S is 2 mol.% at 1095 K. Regularities of phase diagram changes of Cu 2 S-A II S (A II =Mg, Ca, Sr, Ba) system are determined. Thermodynamic analysis is done [ru

  11. In-field X-ray and neutron diffraction studies of re-entrant charge-ordering and field induced metastability in La0.175Pr0.45Ca0.375MnO3-δ

    Science.gov (United States)

    Sharma, Shivani; Shahee, Aga; Yadav, Poonam; da Silva, Ivan; Lalla, N. P.

    2017-11-01

    Low-temperature high-magnetic field (2 K, 8 T) (LTHM) powder X-ray diffraction (XRD) and time of flight powder neutron diffraction (NPD), low-temperature transmission electron microscopic (TEM), and resistivity and magnetization measurements have been carried out to investigate the re-entrant charge ordering (CO), field induced structural phase transitions, and metastability in phase-separated La0.175Pr0.45Ca0.375MnO3-δ (LPCMO). Low-temperature TEM and XRD studies reveal that on cooling under zero-field, paramagnetic Pnma phase transforms to P21/m CO antiferromagnetic (AFM) insulating phase below ˜233 K. Unlike reported literature, no structural signature of CO AFM P21/m to ferromagnetic (FM) Pnma phase-transition during cooling down to 2 K under zero-field was observed. However, the CO phase was found to undergo a re-entrant transition at ˜40 K. Neutron diffraction studies revealed a pseudo CE type spin arrangement of the observed CO phase. The low-temperature resistance, while cooled under zero-field, shows insulator to metal like transition below ˜105 K with minima at ˜25 K. On application of field, the CO P21/m phase was found to undergo field-induced transition to FM Pnma phase, which shows irreversibility on field removal below ˜40 K. Zero-field warming XRD and NPD studies reveal that field-induced FM Pnma phase is a metastable phase, which arise due to the arrest of kinetics of the first-order phase transition of FM Pnma to CO-AFM P21/m phase, below 40 K. Thus, a strong magneto-structural coupling is observed for this system. A field-temperature (H-T) phase-diagram has been constructed based on the LTHM-XRD, which matches very nicely with the reported H-T phase-diagram constructed based on magnetic measurements. Due to the occurrence of gradual growth of the re-entrant CO phase and the absence of a clear structural signature of phase-separation of CO-AFM P21/m and FM Pnma phases, the H-T minima in the phase-diagram of the present LPCMO sample has been

  12. Investigation of phase diagrams for cylindrical Ising nanotube using cellular automata

    Science.gov (United States)

    Astaraki, M.; Ghaemi, M.; Afzali, K.

    2018-05-01

    Recent developments in the field of applied nanoscience and nanotechnology have heightened the need for categorizing various characteristics of nanostructures. In this regard, this paper establishes a novel method to investigate magnetic properties (phase diagram and spontaneous magnetization) of a cylindrical Ising nanotube. Using a two-layer Ising model and the core-shell concept, the interactions within nanotube has been modelled. In the model, both ferromagnetic and antiferromagnetic cases have been considered. Furthermore, the effect of nanotube's length on the critical temperature is investigated. The model has been simulated using cellular automata approach and phase diagrams were constructed for different values of inter- and intra-layer couplings. For the antiferromagnetic case, the possibility of existence of compensation point is observed.

  13. P-T phase diagram of a holographic s+p model from Gauss-Bonnet gravity

    International Nuclear Information System (INIS)

    Nie, Zhang-Yu; Zeng, Hui

    2015-01-01

    In this paper, we study the holographic s+p model in 5-dimensional bulk gravity with the Gauss-Bonnet term. We work in the probe limit and give the Δ-T phase diagrams at three different values of the Gauss-Bonnet coefficient to show the effect of the Gauss-Bonnet term. We also construct the P-T phase diagrams for the holographic system using two different definitions of the pressure and compare the results.

  14. Phase diagram of a QED-cavity array coupled via a N-type level scheme

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Jiasen; Rossini, Davide [CNR, NEST, Scuola Normale Superiore and Istituto di Nanoscienze, Pisa (Italy); Fazio, Rosario [CNR, NEST, Scuola Normale Superiore and Istituto di Nanoscienze, Pisa (Italy); National University of Singapore, Center for Quantum Technologies, Singapore (Singapore)

    2015-01-01

    We study the zero-temperature phase diagram of a one-dimensional array of QED cavities where, besides the single-photon hopping, an additional coupling between neighboring cavities is mediated by an N-type four-level system. By varying the relative strength of the various couplings, the array is shown to exhibit a variety of quantum phases including a polaritonic Mott insulator, a density-wave and a superfluid phase. Our results have been obtained by means of numerical density-matrix renormalization group calculations. The phase diagram was obtained by analyzing the energy gaps for the polaritons, as well as through a study of two-point correlation functions. (orig.)

  15. Calculation of superalloy phase diagrams. IV

    International Nuclear Information System (INIS)

    Kaufman, L.; Nesor, H.

    1975-01-01

    Explicit descriptions of the Fe--Mo, Fe--W, Fe--Nb, W--Cr and Ti--W binary systems have been developed in line with lattice stability, thermochemical and phase diagram data. These descriptions, along with similar results derived previously, have been employed to calculate isothermal sections in the Cr--Al--Fe, Fe--Mo--Cr, Fe--W--Cr, Ni--Al--Co, Nb--Ti--W, Ti--W--Mo, Cr--W--Mo, Ni--Mo--W, and Ni--W--Ti systems for comparison with experimental results. The effects of carbon impurities on miscibility gap formation in the Ti--W, Nb--Ti--W, Ti--W--Mo and Cr--W--Mo systems are discussed

  16. Zr-Fe-Sn Ternary System Phase Diagrams- New Experimental Results

    International Nuclear Information System (INIS)

    Nieva, N; Gomez, A; Arias, D

    2004-01-01

    New experimental results for the Zr-Fe-Sn ternary system are presented in this paper. The phases present and equilibrium relations for the 900 o C isothermal on the central zone of the Gibbs triangle are analysed. A set of ternary alloys was designed and obtained, and they were analysed by semi quantitative SEM- EDS, XRD, and metallographic samples. The resulting ternary phase diagrams are presented here (JCH)

  17. 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

    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...... 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...

  18. Investigation of binary solid phases by calorimetry and kinetic modelling

    OpenAIRE

    Matovic, M.

    2007-01-01

    The traditional methods for the determination of liquid-solid phase diagrams are based on the assumption that the overall equilibrium is established between the phases. However, the result of the crystallization of a liquid mixture will typically be a non-equilibrium or metastable state of the solid. For a proper description of the crystallization process the equilibrium approach is insufficient and a kinetic approach is actually required. In this work, we show that during slow crystallizatio...

  19. Ground state phase diagram of extended attractive Hubbard model

    International Nuclear Information System (INIS)

    Robaszkiewicz, S.; Chao, K.A.; Micnas, R.

    1980-08-01

    The ground state phase diagram of the extended Hubbard model with intraatomic attraction has been derived in the Hartree-Fock approximation formulated in terms of the Bogoliubov variational approach. For a given value of electron density, the nature of the ordered ground state depends essentially on the sign and the strength of the nearest neighbor coupling. (author)

  20. Automated discovery and construction of surface phase diagrams using machine learning

    International Nuclear Information System (INIS)

    Ulissi, Zachary W.; Singh, Aayush R.; Tsai, Charlie

    2016-01-01

    Surface phase diagrams are necessary for understanding surface chemistry in electrochemical catalysis, where a range of adsorbates and coverages exist at varying applied potentials. These diagrams are typically constructed using intuition, which risks missing complex coverages and configurations at potentials of interest. More accurate cluster expansion methods are often difficult to implement quickly for new surfaces. We adopt a machine learning approach to rectify both issues. Using a Gaussian process regression model, the free energy of all possible adsorbate coverages for surfaces is predicted for a finite number of adsorption sites. Our result demonstrates a rational, simple, and systematic approach for generating accurate free-energy diagrams with reduced computational resources. Finally, the Pourbaix diagram for the IrO_2(110) surface (with nine coverages from fully hydrogenated to fully oxygenated surfaces) is reconstructed using just 20 electronic structure relaxations, compared to approximately 90 using typical search methods. Similar efficiency is demonstrated for the MoS_2 surface.

  1. Formation, structure and magnetism of the metastable defect fluorite phases AVO3.5+x (A=In, Sc)

    International Nuclear Information System (INIS)

    Shafi, Shahid P.; Lundgren, Rylan J.; Cranswick, Lachlan M.D.; Bieringer, Mario

    2007-01-01

    We report the preparation and stability of ScVO 3.5+x and the novel phase InVO 3.5+x . AVO 3.5+x (A=Sc, In) defect fluorite structures are formed as metastable intermediates during the topotactic oxidation of AVO 3 bixbyites. The oxidation pathway has been studied in detail by means of thermogravimetric/differential thermal analysis and in-situ powder X-ray diffraction. The oxidation of the bixbyite phase follows a topotactic pathway at temperatures between 300 and 400 deg. C in air/carbon dioxide. The range of accessible oxygen stoichiometries for the AVO 3.5+x structures following this pathway are 0.00≤x≤0.22. Rietveld refinements against powder X-ray and neutron data revealed that InVO 3.54 and ScVO 3.70 crystallize in the defect fluorite structure in space group Fm-3 m (227) with a=4.9863(5) and 4.9697(3)A, respectively with A 3+ /V 4+ disorder on the (4a) cation site. Powder neutron diffraction experiments indicate clustering of oxide defects in all samples. Bulk magnetic measurements showed the presence of V 4+ and the absence of magnetic ordering at low temperatures. Powder neutron diffraction experiments confirmed the absence of a long range ordered magnetic ground state. - Graphical abstract: Topotactic oxidation of AVO 3 bixbyite to AVO 3.5 defect fluorite structure followed by in-situ powder X-ray diffraction. The upper structural diagram shows a six coordinated (A/V)-O 6 fragment in bixbyite, the lower structure illustrates the same seven-fold coordinated (A/V)-O 7 cubic environment in the defect fluorite structure

  2. A general analytical equation for phase diagrams of an N-layer ferroelectric thin film with two surface layers

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Z X; Teng, B H; Rong, Y H; Lu, X H; Yang, X [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China)], E-mail: phytbh@163.com

    2010-03-15

    Within the framework of effective-field theory with correlations, the phase diagrams of an N-layer ferroelectric thin film with two surface layers are studied by the differential operator technique based on the spin-1/2 transverse Ising model. A general analytical equation for the phase diagram of a ferroelectric thin film with arbitrary layer number as well as exchange interactions and transverse fields is derived, and then the effects of exchange interactions and transverse fields on phase diagrams are discussed for an arbitrary layer number N. Meanwhile, the crossover features, from the ferroelectric-dominant phase diagram (FPD) to the paraelectric-dominant phase diagram (PPD), for various parameters of an N-layer ferroelectric thin film with two surface layers are investigated. As a result, an N-independent common intersection point equation is obtained, and the three-dimensional curved surfaces for the crossover values are constructed. In comparison with the usual mean-field approximation, the differential operator technique with correlations reduces to some extent the ferroelectric features of a ferroelectric thin film.

  3. 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.

  4. Dark energy in six nearby galaxy flows: Synthetic phase diagrams and self-similarity

    Science.gov (United States)

    Chernin, A. D.; Teerikorpi, P.; Dolgachev, V. P.; Kanter, A. A.; Domozhilova, L. M.; Valtonen, M. J.; Byrd, G. G.

    2012-09-01

    Outward flows of galaxies are observed around groups of galaxies on spatial scales of about 1 Mpc, and around galaxy clusters on scales of 10 Mpc. Using recent data from the Hubble Space Telescope (HST), we have constructed two synthetic velocity-distance phase diagrams: one for four flows on galaxy-group scales and the other for two flows on cluster scales. It has been shown that, in both cases, the antigravity produced by the cosmic dark-energy background is stronger than the gravity produced by the matter in the outflow volume. The antigravity accelerates the flows and introduces a phase attractor that is common to all scales, corresponding to a linear velocity-distance relation (the local Hubble law). As a result, the bundle of outflow trajectories mostly follow the trajectory of the attractor. A comparison of the two diagrams reveals the universal self-similar nature of the outflows: their gross phase structure in dimensionless variables is essentially independent of their physical spatial scales, which differ by approximately a factor of 10 in the two diagrams.

  5. Phase diagram of the Fe-Sn-Zr system at 800 °C

    International Nuclear Information System (INIS)

    Nieva, N.; Corvalán, C.; Jiménez, M.J.; Gómez, A.; Arreguez, C.; Joubert, J.-M.; Arias, D.

    2017-01-01

    New experimental results on the Fe-Sn-Zr phase diagram at 800 °C are presented, particularly in the central, Fe rich and Sn rich regions of the Gibbs triangle. Seven ternary alloys were designed, produced and examined by different techniques: optical and scanning electron microscopy, semi-quantitative microanalysis, quantitative microanalysis and X-ray diffraction. The results of this work and previous experimental data were used to determine the phase diagram section at 800 °C which contains at least five ternary compounds: Fe 6 Sn 6 Zr, Y, X′, θ and C36. - Highlights: •A phase diagram of Fe-Sn-Zr system at 800 °C is proposed. •The isothermal section of Fe-Sn-Zr system at 800 °C and that at 900 °C determined previously allow reliable extrapolations at low temperatures. •The study at different temperatures (900 °C and 800 °C in this case) is highly desirable because it allows the separation between enthalpic and entropic effects in a future Calphad modelling.

  6. Phase diagram of the Fe-Sn-Zr system at 800 °C

    Energy Technology Data Exchange (ETDEWEB)

    Nieva, N. [Laboratorio de Física del Sólido, Departamento de Física, Facultad de Ciencias Exactas y Tecnología, Universidad Nacional de Tucumán (Argentina); Corvalán, C., E-mail: corvalan@cnea.gov.ar [Gerencia de Materiales, Comisión Nacional de Energía Atómica Argentina (CNEA), Universidad Nacional de Tres de Febrero, Argentina, CONICET, Consejo Nacional de Ciencia y Técnica (Argentina); Jiménez, M.J. [IFISUR, CONICET, Departamento de Física, Universidad Nacional del Sur, Bahía Blanca (Argentina); Gómez, A. [Grupo LMFAE – PPFAE, Centro Atómico Ezeiza, Comisión Nacional de Energía Atómica (Argentina); Arreguez, C. [Laboratorio de Física del Sólido, Departamento de Física, Facultad de Ciencias Exactas y Tecnología, Universidad Nacional de Tucumán (Argentina); Joubert, J.-M. [Chimie Métallurgique des Terres Rares (CMTR), Institut de Chimie et des Matériaux Paris-Est (ICMPE), CNRS, Université Paris-Est Créteil, 2-8 rue Henri Dunant, 94320 Thiais Cedex (France); Arias, D. [Instituto de Tecnología J. Sabato, Universidad Nacional de San Martín-CNEA (Argentina)

    2017-04-15

    New experimental results on the Fe-Sn-Zr phase diagram at 800 °C are presented, particularly in the central, Fe rich and Sn rich regions of the Gibbs triangle. Seven ternary alloys were designed, produced and examined by different techniques: optical and scanning electron microscopy, semi-quantitative microanalysis, quantitative microanalysis and X-ray diffraction. The results of this work and previous experimental data were used to determine the phase diagram section at 800 °C which contains at least five ternary compounds: Fe{sub 6}Sn{sub 6}Zr, Y, X′, θ and C36. - Highlights: •A phase diagram of Fe-Sn-Zr system at 800 °C is proposed. •The isothermal section of Fe-Sn-Zr system at 800 °C and that at 900 °C determined previously allow reliable extrapolations at low temperatures. •The study at different temperatures (900 °C and 800 °C in this case) is highly desirable because it allows the separation between enthalpic and entropic effects in a future Calphad modelling.

  7. Phase diagrams of ferroelectric nanocrystals strained by an elastic matrix

    Science.gov (United States)

    Nikitchenko, A. I.; Azovtsev, A. V.; Pertsev, N. A.

    2018-01-01

    Ferroelectric crystallites embedded into a dielectric matrix experience temperature-dependent elastic strains caused by differences in the thermal expansion of the crystallites and the matrix. Owing to the electrostriction, these lattice strains may affect polarization states of ferroelectric inclusions significantly, making them different from those of a stress-free bulk crystal. Here, using a nonlinear thermodynamic theory, we study the mechanical effect of elastic matrix on the phase states of embedded single-domain ferroelectric nanocrystals. Their equilibrium polarization states are determined by minimizing a special thermodynamic potential that describes the energetics of an ellipsoidal ferroelectric inclusion surrounded by a linear elastic medium. To demonstrate the stability ranges of such states for a given material combination, we construct a phase diagram, where the inclusion’s shape anisotropy and temperature are used as two parameters. The ‘shape-temperature’ phase diagrams are calculated numerically for PbTiO3 and BaTiO3 nanocrystals embedded into representative dielectric matrices generating tensile (silica glass) or compressive (potassium silicate glass) thermal stresses inside ferroelectric inclusions. The developed phase maps demonstrate that the joint effect of thermal stresses and matrix-induced elastic clamping of ferroelectric inclusions gives rise to several important features in the polarization behavior of PbTiO3 and BaTiO3 nanocrystals. In particular, the Curie temperature displays a nonmonotonic variation with the ellipsoid’s aspect ratio, being minimal for spherical inclusions. Furthermore, the diagrams show that the polarization orientation with respect to the ellipsoid’s symmetry axis is controlled by the shape anisotropy and the sign of thermal stresses. Under certain conditions, the mechanical inclusion-matrix interaction qualitatively alters the evolution of ferroelectric states on cooling, inducing a structural transition

  8. Effective-field theory for dynamic phase diagrams of the kinetic spin-3/2 Blume–Capel model under a time oscillating longitudinal field

    Energy Technology Data Exchange (ETDEWEB)

    Ertaş, Mehmet [Department of Physics, Erciyes University, 38039 Kayseri (Turkey); Kocakaplan, Yusuf [Institute of Science, Erciyes University, 38039 Kayseri (Turkey); Keskin, Mustafa, E-mail: keskin@erciyes.edu.tr [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2013-12-15

    Dynamic phase diagrams are presented for the kinetic spin-3/2 Blume–Capel model under a time oscillating longitudinal field by use of the effective-field theory with correlations. The dynamic equation of the average magnetization is obtained for the square lattice by utilizing the Glauber-type stochastic process. Dynamic phase diagrams are presented in the reduced temperature and the magnetic field amplitude plane. We also investigated the effect of longitudinal field frequency. Finally, the discussion and comparison of the phase diagrams are given. - Highlights: • Dynamic behaviors in the spin-3/2 Blume–Capel system is investigated by the effective-field theory based on the Glauber-type stochastic dynamics. • The dynamic phase transitions and dynamic phase diagrams are obtained. • The effects of the longitudinal field frequency on the dynamic phase diagrams of the system are investigated. • Dynamic phase diagrams exhibit several ordered phases, coexistence phase regions and several critical points as well as a re-entrant behavior.

  9. Effective-field theory for dynamic phase diagrams of the kinetic spin-3/2 Blume–Capel model under a time oscillating longitudinal field

    International Nuclear Information System (INIS)

    Ertaş, Mehmet; Kocakaplan, Yusuf; Keskin, Mustafa

    2013-01-01

    Dynamic phase diagrams are presented for the kinetic spin-3/2 Blume–Capel model under a time oscillating longitudinal field by use of the effective-field theory with correlations. The dynamic equation of the average magnetization is obtained for the square lattice by utilizing the Glauber-type stochastic process. Dynamic phase diagrams are presented in the reduced temperature and the magnetic field amplitude plane. We also investigated the effect of longitudinal field frequency. Finally, the discussion and comparison of the phase diagrams are given. - Highlights: • Dynamic behaviors in the spin-3/2 Blume–Capel system is investigated by the effective-field theory based on the Glauber-type stochastic dynamics. • The dynamic phase transitions and dynamic phase diagrams are obtained. • The effects of the longitudinal field frequency on the dynamic phase diagrams of the system are investigated. • Dynamic phase diagrams exhibit several ordered phases, coexistence phase regions and several critical points as well as a re-entrant behavior

  10. Low-temperature phase diagram of YbBiPt

    International Nuclear Information System (INIS)

    Movshovich, R.; Lacerda, A.; Canfield, P.C.; Thompson, J.D.; Fisk, Z.

    1994-01-01

    Resistivity measurements are reported on the cubic heavy-fermion compound YbBiPt at ambient and hydrostatic pressures to ∼19 kbar and in magnetic fields to 1 T. The phase transition at T c =0.4 K is identified by a sharp rise in resistivity. That feature is used to build low-temperature H-T and P-T phase diagrams. The phase boundary in the H-T plane follows the weak-coupling BCS expression remarkably well from T c to T c /4, while small hydrostatic pressure of ∼1 kbar suppresses the low-temperature phase entirely. These effects of hydrostatic pressure and magnetic field on the phase transition are consistent with an spin-density-wave (SDW) formation in a very heavy electron band at T=0.4 K. Outside of the SDW phase at low temperature, hydrostatic pressure increases the T 2 coefficient of resistivity, signaling an increase in heavy-fermion correlations with hydrostatic pressure. The residual resistivity decreases with pressure, contrary to trends in other Yb heavy-fermion compounds

  11. E-T phase diagram of an antiferroelectric liquid crystal with re-entrand smectic C* phase

    Czech Academy of Sciences Publication Activity Database

    Na, Y.-H.; Naruse, Y.; Fukuda, N.; Orihara, H.; Fajar, A.; Hamplová, Věra; Kašpar, Miroslav; Glogarová, Milada

    2008-01-01

    Roč. 364, č. 1 (2008), s. 13-19 ISSN 0015-0193 Institutional research plan: CEZ:AV0Z10100520 Keywords : phase diagram * liquid crystals * dielectric measurements * electric field Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.562, year: 2008

  12. 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.

  13. Determining the phase diagram of lithium via ab initio calculation and ramp compression

    Science.gov (United States)

    Shulenburger, Luke; Seagle, Chris; Haill, Thomas; Harding, Eric

    2015-06-01

    Diamond anvil cell experiments have shown elemental lithium to have an extraordinarily complex phase diagram under pressure exhibiting numerous solid phases at pressures below 1 Mbar, as well as a complicated melting behavior. We explore this phase diagram utilizing a combination of quantum mechanical calculations and ramp compression experiments performed on Sandia National Laboratories' Z-machine. We aim to extend our knowledge of the high pressure behavior to moderate temperatures at pressures above 50 GPa with a specific focus on the melt line above 70 GPa. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the US Dept of Energy's Natl. Nuclear Security Administration under Contract DE-AC04-94AL85000.

  14. A novel series of isoreticular metal organic frameworks: Realizing metastable structures by liquid phase epitaxy

    KAUST Repository

    Liu, Jinxuan; Lukose, Binit; Shekhah, Osama; Arslan, Hasan Kemal; Weidler, Peter; Gliemann, Hartmut; Brä se, Stefan; Grosjean, Sylvain; Godt, Adelheid; Feng, Xinliang; Mü llen, Klaus; Magdau, Ioan-Bogdan; Heine, Thomas; Wö ll, Christof

    2012-01-01

    A novel class of metal organic frameworks (MOFs) has been synthesized from Cu-acetate and dicarboxylic acids using liquid phase epitaxy. The SURMOF-2 isoreticular series exhibits P4 symmetry, for the longest linker a channel-size of 3 3 nm2 is obtained, one of the largest values reported for any MOF so far. High quality, ab-initio electronic structure calculations confirm the stability of a regular packing of (Cu++) 2-carboxylate paddle-wheel planes with P4 symmetry and reveal, that the SURMOF-2 structures are in fact metastable, with a fairly large activation barrier for the transition to the bulk MOF-2 structures exhibiting a lower, twofold (P2 or C2) symmetry. The theoretical calculations also allow identifying the mechanism for the low-temperature epitaxial growth process and to explain, why a synthesis of this highly interesting, new class of high-symmetry, metastable MOFs is not possible using the conventional solvothermal process.

  15. A novel series of isoreticular metal organic frameworks: Realizing metastable structures by liquid phase epitaxy

    KAUST Repository

    Liu, Jinxuan

    2012-12-04

    A novel class of metal organic frameworks (MOFs) has been synthesized from Cu-acetate and dicarboxylic acids using liquid phase epitaxy. The SURMOF-2 isoreticular series exhibits P4 symmetry, for the longest linker a channel-size of 3 3 nm2 is obtained, one of the largest values reported for any MOF so far. High quality, ab-initio electronic structure calculations confirm the stability of a regular packing of (Cu++) 2-carboxylate paddle-wheel planes with P4 symmetry and reveal, that the SURMOF-2 structures are in fact metastable, with a fairly large activation barrier for the transition to the bulk MOF-2 structures exhibiting a lower, twofold (P2 or C2) symmetry. The theoretical calculations also allow identifying the mechanism for the low-temperature epitaxial growth process and to explain, why a synthesis of this highly interesting, new class of high-symmetry, metastable MOFs is not possible using the conventional solvothermal process.

  16. 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

    to polynomials of the form κ(X)=A(X)+B(X)(T-Tm)+C(X)(T-Tm)2, where Tm is the intermediate temperature of the measured temperature range and X, the mole fraction of KHSO4. The possible role of this binary system as a catalyst solvent is also discussed. (C) 2005 Elsevier B.V. All rights reserved.......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...

  17. Phase diagram studies for microencapsulation of pharmaceuticals using cellulose acetate trimellitate.

    Science.gov (United States)

    Sanghvi, S P; Nairn, J G

    1991-04-01

    Phase diagrams were prepared to indicate the region of microcapsule formation for the following system: cellulose acetate trimellitate, light mineral oil, and the solvent mixture (acetone:ethanol), using chloroform as the hardening agent. The effect of sorbitan monoleate, sorbitan monolaurate, and sorbitan trioleate on the region of the phase diagram for the formation of microcapsules was investigated. The results indicate that microcapsules are readily formed when the polymer concentration is in the 0.5-1.5% range and the solvent concentration is in the 5-10% range. Aggregation of microcapsules was minimized by using lower solvent concentration. Low concentrations of sorbitan monooleate in mineral oil (less than or equal to 1%) gave products that had smoother coats and more uniform particle size. Surfactants with low hydrophile:lipophile balance produced larger regions on the phase diagram for microencapsulation compared with a surfactant with higher hydrophile:lipophile balance. A mechanism for microencapsulation is described. Tartrazine microcapsules produced using different concentrations of surfactant were tested for dissolution characteristics in both acidic and neutral conditions. Tartrazine-containing microcapsules prepared by using 3% sorbitan monooleate had the lowest release in acidic conditions. The effect of surfactant and formulation concentration on microcapsule size was studied by analyzing the particle size distribution for both blank and tartrazine-containing microcapsules. The smallest microcapsule size was obtained when the sorbitan monooleate concentration was 3%. It appears that there is an upper limit for the surfactant concentration that could be used to achieve successful microencapsulation.

  18. Neutron-diffraction studies of the nuclear magnetic phase diagram of copper

    DEFF Research Database (Denmark)

    Annila, A.J.; Clausen, Kurt Nørgaard; Oja, A.S.

    1992-01-01

    We have studied the spontaneous antiferromagnetic (AF) order in the nuclear spin system of copper by use of neutron-diffraction experiments at nanokelvin temperatures. Copper is an ideal model system as a nearest-neighbor-dominated spin-3/2 fcc antiferromagnet. The phase diagram has been investig......We have studied the spontaneous antiferromagnetic (AF) order in the nuclear spin system of copper by use of neutron-diffraction experiments at nanokelvin temperatures. Copper is an ideal model system as a nearest-neighbor-dominated spin-3/2 fcc antiferromagnet. The phase diagram has been...... investigated by measuring the magnetic-field dependence of the (100) reflection, characteristic of a type-I AF structure, and of a Bragg peak at (0 2/3 2/3). The results suggest the presence of high-field (100) phases at 0.12 less-than-or-equal-to B less-than-or-equal-to B(c) almost-equal-to 0.26 mT, for B...... compared with results of earlier susceptibility measurements in order to identify the translational periods of the three previously found antiferromagnetic phases for B parallel-to [100]. Recent theoretical work has yielded results in agreement with our experimental data....

  19. Thermochemical and phase diagram studies of the Sn–Zn–Ni system

    Czech Academy of Sciences Publication Activity Database

    Gandova, V.D.; Brož, P.; Buršík, Jiří; Vassilev, G.P.

    2011-01-01

    Roč. 524, 1-2 (2011), s. 47-55 ISSN 0040-6031 Institutional research plan: CEZ:AV0Z20410507 Keywords : DSC * solders * Sn-Zn-Ni phase diagram Subject RIV: BJ - Thermodynamics Impact factor: 1.805, year: 2011

  20. Dynamic phase transitions and dynamic phase diagrams of the spin-2 Blume-Capel model under an oscillating magnetic field within the effective-field theory

    Energy Technology Data Exchange (ETDEWEB)

    Ertas, Mehmet [Department of Physics, Erciyes University, 38039 Kayseri (Turkey); Institute of Science, Erciyes University, 38039 Kayseri (Turkey); Deviren, Bayram [Department of Physics, Nevsehir University, 50300 Nevsehir (Turkey); Keskin, Mustafa, E-mail: keskin@erciyes.edu.tr [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2012-03-15

    The dynamic phase transitions are studied in the kinetic spin-2 Blume-Capel model under a time-dependent oscillating magnetic field using the effective-field theory with correlations. The effective-field dynamic equation for the average magnetization is derived by employing the Glauber transition rates and the phases in the system are obtained by solving this dynamic equation. The nature (first- or second-order) of the dynamic phase transition is characterized by investigating the thermal behavior of the dynamic magnetization and the dynamic phase transition temperatures are obtained. The dynamic phase diagrams are constructed in the reduced temperature and magnetic field amplitude plane and are of seven fundamental types. Phase diagrams contain the paramagnetic (P), ferromagnetic-2 (F{sub 2}) and three coexistence or mixed phase regions, namely the F{sub 2}+P, F{sub 1}+P and F{sub 2}+F{sub 1}+P, which strongly depend on the crystal-field interaction (D) parameter. The system also exhibits the dynamic tricritical behavior. - Highlights: Black-Right-Pointing-Pointer Dynamic phase transitions are studied in spin-2 BC model using EFT. Black-Right-Pointing-Pointer Dynamic phase diagrams are constructed in (T/zJ, h/zJ) plane. Black-Right-Pointing-Pointer Seven fundamental types of dynamic phase diagrams are found in the system. Black-Right-Pointing-Pointer System exhibits dynamic tricritical behavior.

  1. Stability conditions and phase diagrams for two-component Fermi gases with population imbalance

    International Nuclear Information System (INIS)

    Chen Qijin; He Yan; Chien, C.-C.; Levin, K.

    2006-01-01

    Superfluidity in atomic Fermi gases with population imbalance has recently become an exciting research focus. There is considerable disagreement in the literature about the appropriate stability conditions for states in the phase diagram throughout the BCS to Bose-Einstein condensation crossover. Here we discuss these stability conditions for homogeneous polarized superfluid phases, and compare with recent alternative proposals. The requirement of a positive second-order partial derivative of the thermodynamic potential with respect to the fermionic excitation gap Δ (at fixed chemical potentials) is demonstrated to be equivalent to the positive definiteness of the particle number susceptibility matrix. In addition, we show the positivity of the effective pair mass constitutes another nontrivial stability condition. These conditions determine the (local) stability of the system towards phase separation (or other ordered phases). We also study systematically the effects of finite temperature and the related pseudogap on the phase diagrams defined by our stability conditions

  2. Temperature gradient method for lipid phase diagram construction using time-resolved x-ray diffraction

    International Nuclear Information System (INIS)

    Caffrey, M.; Hing, F.S.

    1987-01-01

    A method that enables temperature-composition phase diagram construction at unprecedented rates is described and evaluated. The method involves establishing a known temperature gradient along the length of a metal rod. Samples of different compositions contained in long, thin-walled capillaries are positioned lengthwise on the rod and equilibrated such that the temperature gradient is communicated into the sample. The sample is then moved through a focused, monochromatic synchrotron-derived x-ray beam and the image-intensified diffraction pattern from the sample is recorded on videotape continuously in live-time as a function of position and, thus, temperature. The temperature at which the diffraction pattern changes corresponds to a phase boundary, and the phase(s) existing (coexisting) on either side of the boundary can be identified on the basis of the diffraction pattern. Repeating the measurement on samples covering the entire composition range completes the phase diagram. These additional samples can be conveniently placed at different locations around the perimeter of the cylindrical rod and rotated into position for diffraction measurement. Temperature-composition phase diagrams for the fully hydrated binary mixtures, dimyristoylphosphatidylcholine (DMPC)/dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylethanolamine (DPPE)/DPPC, have been constructed using the new temperature gradient method. They agree well with and extend the results obtained by other techniques. In the DPPE/DPPC system structural parameters as a function of temperature in the various phases including the subgel phase are reported. The potential limitations of this steady-state method are discussed

  3. Revision of the Ge–Ti phase diagram and structural stability of the new phase Ge4Ti5

    International Nuclear Information System (INIS)

    Bittner, Roland W.; Colinet, Catherine; Tedenac, Jean-Claude; Richter, Klaus W.

    2013-01-01

    Highlights: •New compound Ge 4 Ti 5 found by experiments and by DFT ground state calculations. •Enthalpies of formation calculated for different Ge–Ti compounds. •Modifications of the Ge–Ti phase diagram suggested. -- Abstract: The binary phase diagram Ge–Ti was investigated experimentally by powder X-ray diffraction, scanning electron microscopy including EDX analysis, and differential thermal analysis. Total energies of the compounds GeTi 3 , GeTi 2 , Ge 3 Ti 5 , Ge 4 Ti 5 , Ge 5 Ti 6 , GeTi and Ge 2 Ti were calculated for various structure types employing electronic density-functional theory (DFT). Experimental studies as well as electronic calculations show the existence of a new phase Ge 4 Ti 5 (Ge 4 Sm 5 -type, oP36, Pnma) which is formed in a solid state reaction Ge 3 Ti 5 + Ge 5 Ti 6 = Ge 4 Ti 5 . In addition, a significant homogeneity range was observed for the compound Ge 3 Ti 5 and the composition of the liquid phase in the eutectic reaction L = Ge + Ge 2 Ti was found to be at significant higher Ge-content (97.5 at.% Ge) than reported in previous studies. Based on these new results, a modified phase diagram Ge–Ti is suggested. The zero-temperature lattice parameters and the formation enthalpies determined by DTF calculations were found to be in good agreement with experimental data

  4. Dynamic vortex-phase diagram of MgB2 single crystals near the peak-effect region

    International Nuclear Information System (INIS)

    Kim, Heon-Jung; Lee, Hyun-Sook; Kang, Byeongwon; Chowdhury, P.; Kim, Kyung-Hee; Park, Min-Seok; Lee, Sung-Ik

    2006-01-01

    The dynamic vortex-phase diagram of MgB 2 single crystals has been constructed by using voltage noise characteristics. Between the onset (H on ) and the peak (H p ) magnetic fields, crossovers from a state with large noises to a noise-free state were observed with increasing current while above H p , a reverse behavior was found. We will discuss the dynamic vortex phase diagram and the possible origins of the crossovers

  5. 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.

  6. Phase diagram of the Kondo-Heisenberg model on honeycomb lattice with geometrical frustration

    Science.gov (United States)

    Li, Huan; Song, Hai-Feng; Liu, Yu

    2016-11-01

    We calculated the phase diagram of the Kondo-Heisenberg model on a two-dimensional honeycomb lattice with both nearest-neighbor and next-nearest-neighbor antiferromagnetic spin exchanges, to investigate the interplay between RKKY and Kondo interactions in the presence of magnetic frustration. Within a mean-field decoupling technology in slave-fermion representation, we derived the zero-temperature phase diagram as a function of Kondo coupling J k and frustration strength Q. The geometrical frustration can destroy the magnetic order, driving the original antiferromagnetic (AF) phase to non-magnetic valence bond solids (VBS). In addition, we found two distinct VBS. As J k is increased, a phase transition from AF to Kondo paramagnetic (KP) phase occurs, without the intermediate phase coexisting AF order with Kondo screening found in square lattice systems. In the KP phase, the enhancement of frustration weakens the Kondo screening effect, resulting in a phase transition from KP to VBS. We also found a process to recover the AF order from VBS by increasing J k in a wide range of frustration strength. Our work may provide predictions for future experimental observation of new processes of quantum phase transitions in frustrated heavy-fermion compounds.

  7. Nature of metastable amorphous-to-crystalline reversible phase transformations in GaSb

    Energy Technology Data Exchange (ETDEWEB)

    Kalkan, B. [Advanced Light Source, Lawrence Berkeley Laboratory, Berkeley, California 20015 (United States); Edwards, T. G.; Sen, S. [Department of Chemical Engineering and Materials Science, University of California, Davis, California 95616 (United States); Raoux, S. [IBM T. J. Watson Research Center, Yorktown Heights, New York 10598 (United States)

    2013-08-28

    The structural, thermodynamic, and kinetic aspects of the transformations between the metastable amorphous and crystalline phases of GaSb are investigated as a function of pressure at ambient temperature using synchrotron x-ray diffraction experiments in a diamond anvil cell. The results are consistent with the hypothesis that the pressure induced crystallization of amorphous GaSb into the β-Sn crystal structure near ∼5 GPa is possibly a manifestation of an underlying polyamorphic phase transition between a semiconducting, low density and a metallic, high density amorphous (LDA and HDA, respectively) phases. In this scenario, the large differences in the thermal crystallization kinetics between amorphous GaSb deposited in thin film form by sputtering and that prepared by laser melt quenching may be related to the relative location of the glass transition temperature of the latter in the pressure-temperature (P-T) space with respect to the location of the critical point that terminate the LDA ↔ HDA transition. The amorphous →β-Sn phase transition is found to be hysteretically reversible as the β-Sn phase undergoes decompressive amorphization near ∼2 GPa due to the lattice instabilities that give rise to density fluctuations in the crystal upon decompression.

  8. Nature of metastable amorphous-to-crystalline reversible phase transformations in GaSb

    Science.gov (United States)

    Kalkan, B.; Edwards, T. G.; Raoux, S.; Sen, S.

    2013-08-01

    The structural, thermodynamic, and kinetic aspects of the transformations between the metastable amorphous and crystalline phases of GaSb are investigated as a function of pressure at ambient temperature using synchrotron x-ray diffraction experiments in a diamond anvil cell. The results are consistent with the hypothesis that the pressure induced crystallization of amorphous GaSb into the β-Sn crystal structure near ˜5 GPa is possibly a manifestation of an underlying polyamorphic phase transition between a semiconducting, low density and a metallic, high density amorphous (LDA and HDA, respectively) phases. In this scenario, the large differences in the thermal crystallization kinetics between amorphous GaSb deposited in thin film form by sputtering and that prepared by laser melt quenching may be related to the relative location of the glass transition temperature of the latter in the pressure-temperature (P-T) space with respect to the location of the critical point that terminate the LDA ↔ HDA transition. The amorphous → β-Sn phase transition is found to be hysteretically reversible as the β-Sn phase undergoes decompressive amorphization near ˜2 GPa due to the lattice instabilities that give rise to density fluctuations in the crystal upon decompression.

  9. Nature of metastable amorphous-to-crystalline reversible phase transformations in GaSb

    International Nuclear Information System (INIS)

    Kalkan, B.; Edwards, T. G.; Sen, S.; Raoux, S.

    2013-01-01

    The structural, thermodynamic, and kinetic aspects of the transformations between the metastable amorphous and crystalline phases of GaSb are investigated as a function of pressure at ambient temperature using synchrotron x-ray diffraction experiments in a diamond anvil cell. The results are consistent with the hypothesis that the pressure induced crystallization of amorphous GaSb into the β-Sn crystal structure near ∼5 GPa is possibly a manifestation of an underlying polyamorphic phase transition between a semiconducting, low density and a metallic, high density amorphous (LDA and HDA, respectively) phases. In this scenario, the large differences in the thermal crystallization kinetics between amorphous GaSb deposited in thin film form by sputtering and that prepared by laser melt quenching may be related to the relative location of the glass transition temperature of the latter in the pressure-temperature (P-T) space with respect to the location of the critical point that terminate the LDA ↔ HDA transition. The amorphous →β-Sn phase transition is found to be hysteretically reversible as the β-Sn phase undergoes decompressive amorphization near ∼2 GPa due to the lattice instabilities that give rise to density fluctuations in the crystal upon decompression

  10. Groundstate fidelity phase diagram of the fully anisotropic two-leg spin-½ XXZ ladder

    Science.gov (United States)

    Li, Sheng-Hao; Shi, Qian-Qian; Batchelor, Murray T.; Zhou, Huan-Qiang

    2017-11-01

    The fully anisotropic two-leg spin-\\tfrac{1}{2} XXZ ladder model is studied in terms of an algorithm based on the tensor network (TN) representation of quantum many-body states as an adaptation of projected entangled pair states to the geometry of translationally invariant infinite-size quantum spin ladders. The TN algorithm provides an effective method to generate the groundstate wave function, which allows computation of the groundstate fidelity per lattice site, a universal marker to detect phase transitions in quantum many-body systems. The groundstate fidelity is used in conjunction with local order and string order parameters to systematically map out the groundstate phase diagram of the ladder model. The phase diagram exhibits a rich diversity of quantum phases. These are the ferromagnetic, stripe ferromagnetic, rung singlet, rung triplet, Néel, stripe Néel and Haldane phases, along with the two XY phases XY1 and XY2.

  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. Phase diagram of nanoscale alloy particles used for vapor-liquid-solid growth of semiconductor nanowires.

    Science.gov (United States)

    Sutter, Eli; Sutter, Peter

    2008-02-01

    We use transmission electron microscopy observations to establish the parts of the phase diagram of nanometer sized Au-Ge alloy drops at the tips of Ge nanowires (NWs) that determine their temperature-dependent equilibrium composition and, hence, their exchange of semiconductor material with the NWs. We find that the phase diagram of the nanoscale drop deviates significantly from that of the bulk alloy, which explains discrepancies between actual growth results and predictions on the basis of the bulk-phase equilibria. Our findings provide the basis for tailoring vapor-liquid-solid growth to achieve complex one-dimensional materials geometries.

  13. Metastable State Diamond Growth and its Applications to Electronic Devices.

    Science.gov (United States)

    Jeng, David Guang-Kai

    Diamond which consists of a dense array of carbon atoms joined by strong covalent bonds and formed into a tetrahedral crystal structure has remarkable mechanical, thermal, optical and electrical properties suitable for many industrial applications. With a proper type of doping, diamond is also an ideal semiconductor for high performance electronic devices. Unfortunately, natural diamond is rare and limited by its size and cost, it is not surprising that people continuously look for a synthetic replacement. It was believed for long time that graphite, another form of carbon, may be converted into diamond under high pressure and temperature. However, the exact condition of conversion was not clear. In 1939, O. I. Leipunsky developed an equilibrium phase diagram between graphite and diamond based on thermodynamic considerations. In the phase diagram, there is a low temperature (below 1000^ circC) and low pressure (below 1 atm) region in which diamond is metastable and graphite is stable, therefore establishes the conditions for the coexistence of the two species. Leipunsky's pioneer work opened the door for diamond synthesis. In 1955, the General Electric company (GE) was able to produce artificial diamond at 55k atm pressure and a temperature of 2000^ circC. Contrary to GE, B. Derjaguin and B. V. Spitzyn in Soviet Union, developed a method of growing diamonds at 1000^circC and at a much lower pressure in 1956. Since then, researchers, particularly in Soviet Union, are continuously looking for methods to grow diamond and diamond film at lower temperatures and pressures with slow but steady progress. It was only in the early 80's that the importance of growing diamond films had attracted the attentions of researchers in the Western world and in Japan. Recent progress in plasma physics and chemical vapor deposition techniques in integrated electronics technology have pushed the diamond growth in its metastable states into a new era. In this research, a microwave plasma

  14. Phase diagram of the Dirac spectrum at nonzero chemical potential

    International Nuclear Information System (INIS)

    Osborn, J. C.; Splittorff, K.; Verbaarschot, J. J. M.

    2008-01-01

    The Dirac spectrum of QCD with dynamical fermions at nonzero chemical potential is characterized by three regions: a region with a constant eigenvalue density, a region where the eigenvalue density shows oscillations that grow exponentially with the volume and the remainder of the complex plane where the eigenvalue density is zero. In this paper we derive the phase diagram of the Dirac spectrum from a chiral Lagrangian. We show that the constant eigenvalue density corresponds to a pion condensed phase while the strongly oscillating region is given by a kaon condensed phase. The normal phase with nonzero chiral condensate but vanishing Bose condensates coincides with the region of the complex plane where there are no eigenvalues.

  15. 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.

  16. Cyclic cosmology, conformal symmetry and the metastability of the Higgs

    Science.gov (United States)

    Bars, Itzhak; Steinhardt, Paul J.; Turok, Neil

    2013-10-01

    Recent measurements at the LHC suggest that the current Higgs vacuum could be metastable with a modest barrier (height ( GeV)4) separating it from a ground state with negative vacuum density of order the Planck scale. We note that metastability is problematic for standard bang cosmology but is essential for cyclic cosmology in order to end one cycle, bounce, and begin the next. In this Letter, motivated by the approximate scaling symmetry of the standard model of particle physics and the primordial large-scale structure of the universe, we use our recent formulation of the Weyl-invariant version of the standard model coupled to gravity to track the evolution of the Higgs in a regularly bouncing cosmology. We find a band of solutions in which the Higgs field escapes from the metastable phase during each big crunch, passes through the bang into an expanding phase, and returns to the metastable vacuum, cycle after cycle after cycle. We show that, due to the effect of the Higgs, the infinitely cycling universe is geodesically complete, in contrast to inflation.

  17. Cyclic cosmology, conformal symmetry and the metastability of the Higgs

    International Nuclear Information System (INIS)

    Bars, Itzhak; Steinhardt, Paul J.; Turok, Neil

    2013-01-01

    Recent measurements at the LHC suggest that the current Higgs vacuum could be metastable with a modest barrier (height (10 10–12 GeV) 4 ) separating it from a ground state with negative vacuum density of order the Planck scale. We note that metastability is problematic for standard bang cosmology but is essential for cyclic cosmology in order to end one cycle, bounce, and begin the next. In this Letter, motivated by the approximate scaling symmetry of the standard model of particle physics and the primordial large-scale structure of the universe, we use our recent formulation of the Weyl-invariant version of the standard model coupled to gravity to track the evolution of the Higgs in a regularly bouncing cosmology. We find a band of solutions in which the Higgs field escapes from the metastable phase during each big crunch, passes through the bang into an expanding phase, and returns to the metastable vacuum, cycle after cycle after cycle. We show that, due to the effect of the Higgs, the infinitely cycling universe is geodesically complete, in contrast to inflation

  18. High-pressure phase transition and phase diagram of gallium arsenide

    Science.gov (United States)

    Besson, J. M.; Itié, J. P.; Polian, A.; Weill, G.; Mansot, J. L.; Gonzalez, J.

    1991-09-01

    Under hydrostatic pressure, cubic GaAs-I undergoes phase transitions to at least two orthorhombic structures. The initial phase transition to GaAs-II has been investigated by optical-transmittance measurements, Raman scattering, and x-ray absorption. The structure of pressurized samples, which are retrieved at ambient, has been studied by x-ray diffraction and high-resolution diffraction microscopy. Various criteria that define the domain of stability of GaAs-I are examined, such as the occurrence of crystalline defects, the local variation in atomic coordination number, or the actual change in crystal structure. These are shown not to occur at the same pressure at 300 K, the latter being observable only several GPa above the actual thermodynamic instability pressure of GaAs-I. Comparison of the evolution of these parameters on increasing and decreasing pressure locates the thermodynamic transition region GaAs-I-->GaAs-II at 12+/-1.5 GPa and at 300 K that is lower than generally reported. The use of thermodynamic relations around the triple point, and of regularities in the properties of isoelectronic and isostructural III-V compounds, yields a phase diagram for GaAs which is consistent with this value.

  19. Simple model for the dynamics towards metastable states

    International Nuclear Information System (INIS)

    Meijer, P.H.E.; Keskin, M.; Bodegom, E.

    1986-01-01

    Circumstances under which a quenched system will freeze in a metastable state are studied in simple systems with long-range order. The model used is the time-dependent pair approximation, based on the most probable path (MPP) method. The time dependence of the solution is shown by means of flow diagrams. The fixed points and other features of the differential equations in time are independent of the choice of the rate constants. It is explained qualitatively how the system behaves under varying descending temperatures: the role of the initial conditions, the dependence on the quenching rate, and the response to precooling

  20. Phase Diagram of a Simple Model for Fractional Topological Insulator

    Science.gov (United States)

    Chen, Hua; Yang, Kun

    2012-02-01

    We study a simple model of two species of (or spin-1/2) fermions with short-range intra-species repulsion in the presence of opposite (effetive) magnetic field, each at filling factor 1/3. In the absence of inter-species interaction, the ground state is simply two copies of the 1/3 Laughlin state, with opposite chirality. Due to the overall time-reversal symmetry, this is a fractional topological insulator. We show this phase is stable against moderate inter-species interactions. However strong enough inter-species repulsion leads to phase separation, while strong enough inter-species attraction drives the system into a superfluid phase. We obtain the phase diagram through exact diagonalization caluclations. Nature of the fractional topological insluator-superfluid phase transition is discussed using an appropriate Chern-Simons-Ginsburg-Landau effective field theory.

  1. Equilibrium triple point pressure and pressure-temperature phase diagram of polyethylene

    NARCIS (Netherlands)

    Hikosaka, M.; Tsukijima, K.; Rastogi, S.; Keller, A.

    1992-01-01

    The equil. triple point and pressure and temp. phase diagrams of polyethylene were obtained by in situ optical microscopic and x-ray observations of the melting temp. of hexagonal and orthorhombic isolated extended-chain single crystals at high pressure. The melting temps. of extended-chain crystals

  2. Dynamic phase transition in the kinetic spin-1 Blume-Capel model: Phase diagrams in the temperature and crystal-field interaction plane

    International Nuclear Information System (INIS)

    Keskin, M.; Canko, O.; Temizer, U.

    2007-01-01

    Within a mean-field approach, the stationary states of the kinetic spin-1 Blume-Capel model in the presence of a time-dependent oscillating external magnetic field is studied. The Glauber-type stochastic dynamics is used to describe the time evolution of the system and obtain the mean-field dynamic equation of motion. The dynamic phase-transition points are calculated and phase diagrams are presented in the temperature and crystal-field interaction plane. According to the values of the magnetic field amplitude, three fundamental types of phase diagrams are found: One exhibits a dynamic tricritical point, while the other two exhibit a dynamic zero-temperature critical point

  3. Dynamic phase diagrams of a cylindrical Ising nanowire in the presence of a time dependent magnetic field

    International Nuclear Information System (INIS)

    Kantar, Ersin; Ertaş, Mehmet; Keskin, Mustafa

    2014-01-01

    The dynamic phase diagrams of a cylindrical Ising nanowire in the presence of a time dependent magnetic field are obtained by using the effective-field theory with correlations based on the Glauber-type stochastic dynamics. According to the values of interaction parameters, a number of interesting properties have been found in the dynamic phase diagrams, such as many dynamic critical points (tricritical point, double critical end point, critical end point, zero temperature critical point, multicritical point, tetracritical point, and triple point) as well as reentrant phenomena. - Highlights: • The cylindrical Ising nanowire is investigated within the Glauber dynamics based on EFT. • The time variations of average order parameters to find phases are studied. • The dynamic phase diagrams are found for the different interaction parameters. • The system displays the critical points as well as a reentrant behavior

  4. Dynamic phase diagrams of a cylindrical Ising nanowire in the presence of a time dependent magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Kantar, Ersin; Ertaş, Mehmet, E-mail: mehmetertas@erciyes.edu.tr; Keskin, Mustafa

    2014-06-01

    The dynamic phase diagrams of a cylindrical Ising nanowire in the presence of a time dependent magnetic field are obtained by using the effective-field theory with correlations based on the Glauber-type stochastic dynamics. According to the values of interaction parameters, a number of interesting properties have been found in the dynamic phase diagrams, such as many dynamic critical points (tricritical point, double critical end point, critical end point, zero temperature critical point, multicritical point, tetracritical point, and triple point) as well as reentrant phenomena. - Highlights: • The cylindrical Ising nanowire is investigated within the Glauber dynamics based on EFT. • The time variations of average order parameters to find phases are studied. • The dynamic phase diagrams are found for the different interaction parameters. • The system displays the critical points as well as a reentrant behavior.

  5. Magnetic structures, phase diagram and spin waves of magneto-electric LiNiPO4

    DEFF Research Database (Denmark)

    Jensen, Thomas Bagger Stibius

    2007-01-01

    LiNiPO4 is a magneto-electric material, having co-existing antiferromagnetic and ferroelectric phases when suitable magnetic fields are applied at low temperatures. Such systems have received growing interest in recent years, but the nature of the magneticelectric couplings is yet to be fully...... through the last three years, it is not the primary subject of this thesis. The objective of the phD project has been to provide groundwork that may be beneficiary to future studies of LiNiPO4. More specifically, we have mapped out the magnetic HT phase diagram with magnetic fields below 14.7 T applied...... along the crystallographic c-axis, determined the magnetic structures for the phases in the phase diagram, and have set up a spin model Hamiltonian describing the spin wave dynamics and estimating the relevant magnetic interactions....

  6. Ammonia-water phase diagram and its implications for icy satellites

    International Nuclear Information System (INIS)

    Johnson, M.L.; Nicol, M.

    1986-01-01

    A Holzapfel-type diamond anvil cell is used to determine the NH 3 - H 2 O phase diagram in the region from 0 to 33 mole percent NH 3 , 240 to 370 K, and 0 to 5 GPa. The following phases were identified: liquid; water ices Ih, III, V, VI, VII, and VIII; ammonia monohydrate, NH 3 .H 2 O; and ammonia dihydrate NH 3 . 2 H 2 O. Ammonia dihydrate becomes prominent at moderate pressures (less than 1 GPa), with planetologically significant implications, including the possibility of layering in Titan's magma ocean

  7. New Wang-Landau approach to obtain phase diagrams for multicomponent alloys

    Science.gov (United States)

    Takeuchi, Kazuhito; Tanaka, Ryohei; Yuge, Koretaka

    2017-10-01

    We develop an approach to apply the Wang-Landau algorithm to multicomponent alloys in a semi-grand-canonical ensemble. Although the Wang-Landau algorithm has great advantages over conventional sampling methods, there are few applications to alloys. This is because calculating compositions in a semi-grand-canonical ensemble via the Wang-Landau algorithm requires a multidimensional density of states in terms of total energy and compositions, and constructing it is difficult from the viewpoints of both implementation and computational cost. In this study, we develop a simple approach to calculate the alloy phase diagram based on the Wang-Landau algorithm, and show that a number of one-dimensional densities of states could lead to compositions in a semi-grand-canonical ensemble as a multidimensional density of states could. Finally, we apply the present method to Cu-Au and Pd-Rh alloys and confirm that the present method successfully describes the phase diagram with high efficiency, validity, and accuracy.

  8. Isomerizations of the Nitromethane Radical Cation in the Gas Phase

    DEFF Research Database (Denmark)

    Egsgaard, Helge; Carlsen, Lars; Elbel, Susanne

    1986-01-01

    The concurrent isomerizations of the nitromethane radical cation to its aci-nitromethane and methylnitrite isomers, respectively, has been established based on metastable ion studies and collision activation mass spectrometry. The energy diagram for the ionized nitromethane/aci-nitromethane tauto......The concurrent isomerizations of the nitromethane radical cation to its aci-nitromethane and methylnitrite isomers, respectively, has been established based on metastable ion studies and collision activation mass spectrometry. The energy diagram for the ionized nitromethane...

  9. Phase diagram of the Hubbard model with arbitrary band filling: renormalization group approach

    International Nuclear Information System (INIS)

    Cannas, Sergio A.; Cordoba Univ. Nacional; Tsallis, Constantino.

    1991-01-01

    The finite temperature phase diagram of the Hubbard model in d = 2 and d = 3 is calculated for arbitrary values of the parameter U/t and chemical potential μ using a quantum real space renormalization group. Evidence for a ferromagnetic phase at low temperatures is presented. (author). 15 refs., 5 figs

  10. Phase diagram of incoherently driven strongly correlated photonic lattices

    Science.gov (United States)

    Biella, Alberto; Storme, Florent; Lebreuilly, José; Rossini, Davide; Fazio, Rosario; Carusotto, Iacopo; Ciuti, Cristiano

    2017-08-01

    We explore theoretically the nonequilibrium photonic phases of an array of coupled cavities in presence of incoherent driving and dissipation. In particular, we consider a Hubbard model system where each site is a Kerr nonlinear resonator coupled to a two-level emitter, which is pumped incoherently. Within a Gutzwiller mean-field approach, we determine the steady-state phase diagram of such a system. We find that, at a critical value of the intercavity photon hopping rate, a second-order nonequilibrium phase transition associated with the spontaneous breaking of the U(1 ) symmetry occurs. The transition from an incompressible Mott-like photon fluid to a coherent delocalized phase is driven by commensurability effects and not by the competition between photon hopping and optical nonlinearity. The essence of the mean-field predictions is corroborated by finite-size simulations obtained with matrix product operators and corner-space renormalization methods.

  11. Phase Diagram in a Random Mixture of Two Antiferromagnets with Competing Spin Anisotropies. I

    Science.gov (United States)

    Someya, Yoshiko

    1981-12-01

    The phase diagram of a random mixture of two antiferromagnets with competing spin anisotropies (A1-xBx) has been analyzed by extending the theory of Matsubara and Inawashiro, and Oguchi and Ishikawa. In the model assumed, the anisotropy energies are expressed by the anisotropic exchange interactions. According to this formulation, it has been shown that the concentration dependence of TN becomes a function of \\includegraphics{dummy.eps}, where P, Q=A, B; SP is a magnitude of P-spin, and JPQη is a η component of exchange integral between P- and Q-spin). Further, the phase boundary between an AF phase and an OAF (oblique antiferromagnetic) phase at T{=}0 K has been shown to be determined by α({\\equiv}SB/SA), if \\includegraphics{dummy.eps} are given. The obtained phase diagrams for Fe1-xCoxCl2, K2Mn1-xFexF4 and Fe1-xCoxCl2\\cdot2H2O are compared with the experimental ones.

  12. Effects of the randomly distributed magnetic field on the phase diagrams of the Ising Nanowire II: Continuous distributions

    International Nuclear Information System (INIS)

    Akıncı, Ümit

    2012-01-01

    The effect of the random magnetic field distribution on the phase diagrams and ground state magnetizations of the Ising nanowire has been investigated with effective field theory with correlations. Gaussian distribution has been chosen as a random magnetic field distribution. The variation of the phase diagrams with that distribution parameters has been obtained and some interesting results have been found such as disappearance of the reentrant behavior and first order transitions which appear in the case of discrete distributions. Also for single and double Gaussian distributions, ground state magnetizations for different distribution parameters have been determined which can be regarded as separate partially ordered phases of the system. - Highlights: ► We give the phase diagrams of the Ising nanowire under the continuous randomly distributed magnetic field. ► Ground state magnetization values obtained. ► Different partially ordered phases observed.

  13. Searching for high magnetization density in bulk Fe: the new metastable Fe-6 phase

    Energy Technology Data Exchange (ETDEWEB)

    Umemoto, K; Himmetoglu, B; Wang, JP; Wentzcovitch, RM; Cococcioni, M

    2014-11-26

    We report the discovery of a new allotrope of iron by first principles calculations. This phase has Pmn2(1) symmetry, a six-atom unit cell (hence the name Fe-6), and the highest magnetization density (M-s) among all the known crystalline phases of iron. Obtained from the structural optimizations of the Fe3C-cementite crystal upon carbon removal, Pmn2(1) Fe-6 is shown to result from the stabilization of a ferromagnetic FCC phase, further strained along the Bain path. Although metastable from 0 to 50 GPa, the new phase is more stable at low pressures than the other well-known HCP and FCC allotropes and smoothly transforms into the FCC phase under compression. If stabilized to room temperature, for example, by interstitial impurities, Fe-6 could become the basis material for high M-s rare-earth-free permament magnets and high-impact applications such as light-weight electric engine rotors or high-density recording media. The new phase could also be key to explaining the enigmatic high M-s of Fe16N2, which is currently attracting intense research activity.

  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. Metastability at the Yield-Stress Transition in Soft Glasses

    Directory of Open Access Journals (Sweden)

    Matteo Lulli

    2018-05-01

    Full Text Available We study the solid-to-liquid transition in a two-dimensional fully periodic soft-glassy model with an imposed spatially heterogeneous stress. The model we consider consists of droplets of a dispersed phase jammed together in a continuous phase. When the peak value of the stress gets close to the yield stress of the material, we find that the whole system intermittently tunnels to a metastable “fluidized” state, which relaxes back to a metastable “solid” state by means of an elastic-wave dissipation. This macroscopic scenario is studied through the microscopic displacement field of the droplets, whose time statistics displays a remarkable bimodality. Metastability is rooted in the existence, in a given stress range, of two distinct stable rheological branches, as well as long-range correlations (e.g., large dynamic heterogeneity developed in the system. Finally, we show that a similar behavior holds for a pressure-driven flow, thus suggesting possible experimental tests.

  16. Metastability at the Yield-Stress Transition in Soft Glasses

    Science.gov (United States)

    Lulli, Matteo; Benzi, Roberto; Sbragaglia, Mauro

    2018-04-01

    We study the solid-to-liquid transition in a two-dimensional fully periodic soft-glassy model with an imposed spatially heterogeneous stress. The model we consider consists of droplets of a dispersed phase jammed together in a continuous phase. When the peak value of the stress gets close to the yield stress of the material, we find that the whole system intermittently tunnels to a metastable "fluidized" state, which relaxes back to a metastable "solid" state by means of an elastic-wave dissipation. This macroscopic scenario is studied through the microscopic displacement field of the droplets, whose time statistics displays a remarkable bimodality. Metastability is rooted in the existence, in a given stress range, of two distinct stable rheological branches, as well as long-range correlations (e.g., large dynamic heterogeneity) developed in the system. Finally, we show that a similar behavior holds for a pressure-driven flow, thus suggesting possible experimental tests.

  17. Aggregation of flexible polyelectrolytes: Phase diagram and dynamics.

    Science.gov (United States)

    Tom, Anvy Moly; Rajesh, R; Vemparala, Satyavani

    2017-10-14

    Similarly charged polymers in solution, known as polyelectrolytes, are known to form aggregated structures in the presence of oppositely charged counterions. Understanding the dependence of the equilibrium phases and the dynamics of the process of aggregation on parameters such as backbone flexibility and charge density of such polymers is crucial for insights into various biological processes which involve biological polyelectrolytes such as protein, DNA, etc. Here, we use large-scale coarse-grained molecular dynamics simulations to obtain the phase diagram of the aggregated structures of flexible charged polymers and characterize the morphology of the aggregates as well as the aggregation dynamics, in the presence of trivalent counterions. Three different phases are observed depending on the charge density: no aggregation, a finite bundle phase where multiple small aggregates coexist with a large aggregate and a fully phase separated phase. We show that the flexibility of the polymer backbone causes strong entanglement between charged polymers leading to additional time scales in the aggregation process. Such slowing down of the aggregation dynamics results in the exponent, characterizing the power law decay of the number of aggregates with time, to be dependent on the charge density of the polymers. These results are contrary to those obtained for rigid polyelectrolytes, emphasizing the role of backbone flexibility.

  18. 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.

  19. Application Of Empirical Phase Diagrams For Multidimensional Data Visualization Of High Throughput Microbatch Crystallization Experiments.

    Science.gov (United States)

    Klijn, Marieke E; Hubbuch, Jürgen

    2018-04-27

    Protein phase diagrams are a tool to investigate cause and consequence of solution conditions on protein phase behavior. The effects are scored according to aggregation morphologies such as crystals or amorphous precipitates. Solution conditions affect morphological features, such as crystal size, as well as kinetic features, such as crystal growth time. Common used data visualization techniques include individual line graphs or symbols-based phase diagrams. These techniques have limitations in terms of handling large datasets, comprehensiveness or completeness. To eliminate these limitations, morphological and kinetic features obtained from crystallization images generated with high throughput microbatch experiments have been visualized with radar charts in combination with the empirical phase diagram (EPD) method. Morphological features (crystal size, shape, and number, as well as precipitate size) and kinetic features (crystal and precipitate onset and growth time) are extracted for 768 solutions with varying chicken egg white lysozyme concentration, salt type, ionic strength and pH. Image-based aggregation morphology and kinetic features were compiled into a single and easily interpretable figure, thereby showing that the EPD method can support high throughput crystallization experiments in its data amount as well as its data complexity. Copyright © 2018. Published by Elsevier Inc.

  20. Phase diagram as a function of temperature and magnetic field for magnetic semiconductors

    OpenAIRE

    Gonzalez, I.; Castro, J.; Baldomir, D.

    2002-01-01

    Using an extension of the Nagaev model of phase separation (E.L. Nagaev, and A.I. Podel'shchikov, Sov. Phys. JETP, 71 (1990) 1108), we calculate the phase diagram for degenerate antiferromagnetic semiconductors in the T-H plane for different current carrier densities. Both, wide-band semiconductors and 'double-exchange' materials, are investigated.

  1. Phase diagram as a function of temperature and magnetic field for magnetic semiconductors

    Science.gov (United States)

    González, I.; Castro, J.; Baldomir, D.

    2002-10-01

    Using an extension of the Nagaev model of phase separation [E. L. Nagaev and A. I. Podel'shchikov, Sov. Phys. JETP, 71, 1108 (1990)] we calculate the phase diagram for degenerate antiferromagnetic semiconductors in the T-H plane for different current carrier densities. Both wide-band semiconductors and double-exchange materials are investigated.

  2. Experimental investigation and thermodynamic calculations of the Bi–In–Ni phase diagram

    International Nuclear Information System (INIS)

    Premović, Milena; Minić, Duško; Manasijević, Dragan; Ćosović, Vladan; Živković, Dragana; Dervišević, Irma

    2015-01-01

    Highlights: • Calculated constitutive binary system based on literature data. • Experimentally determined (DTA) temperatures of phase transformations compared with analytical calculation. • Definition of several vertical sections. • Calculated horizontal section, confirmed by experimental SEM–EDS and XRD method. • Calculated liquidus surface projection and determined invariant reaction occurred in ternary Bi–In–Ni system. - Abstract: Phase diagram of the Bi–In–Ni ternary system was investigated using differential thermal analysis (DTA), scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS), and X-ray powder diffraction (XRD) analysis. Experimentally obtained results were compared with the results of thermodynamic calculation of phase equilibria based on calculation of phase diagram (CALPHAD) method and literature data. Phase transition temperatures of alloys with overall compositions along three selected vertical sections In–Bi 0.8 Ni 0.2 , x(Bi) = 0.6 and Bi–In 0.5 Ni 0.5 were measured by DTA. Liquidus temperatures were experimentally determined and compared with the results of thermodynamic calculation. Identification of coexisting phases in samples equilibrated at 100 °C, 300 °C and 350 °C was carried out using SEM–EDS and XRD methods. The obtained results were compared with the calculated isothermal sections of the Bi–In–Ni ternary system at corresponding temperatures. Calculated liquidus projection and invariant equilibria of the Bi–In–Ni ternary system were presented

  3. Quantum mechanical look at the radioactive-like decay of metastable dark energy

    Energy Technology Data Exchange (ETDEWEB)

    Szydlowski, Marek [Jagiellonian University, Astronomical Observatory, Krakow (Poland); Jagiellonian University, Mark Kac Complex Systems Research Centre, Krakow (Poland); Stachowski, Aleksander [Jagiellonian University, Astronomical Observatory, Krakow (Poland); Urbanowski, Krzysztof [University of Zielona Gora, Institute of Physics, Zielona Gora (Poland)

    2017-12-15

    We derive the Shafieloo, Hazra, Sahni and Starobinsky (SHSS) phenomenological formula for the radioactive-like decay of metastable dark energy directly from the principles of quantum mechanics. To this aim we use the Fock-Krylov theory of quantum unstable states. We obtain deeper insight on the decay process as having three basic phases: the phase of radioactive decay, the next phase of damping oscillations, and finally the phase of power-law decay. We consider the cosmological model with matter and dark energy in the form of decaying metastable dark energy and study its dynamics in the framework of non-conservative cosmology with an interacting term determined by the running cosmological parameter. We study the cosmological implications of metastable dark energy and estimate the characteristic time of ending of the radioactive-like decay epoch to be 2.2 x 10{sup 4} of the present age of the Universe. We also confront the model with astronomical data which show that the model is in good agreement with the observations. Our general conclusion is that we are living in the epoch of the radioactive-like decay of metastable dark energy which is a relict of the quantum age of the Universe. (orig.)

  4. High pressure cosmochemistry applied to major planetary interiors: Experimental studies. [phase diagram for the ammonia water system

    Science.gov (United States)

    Nicol, M. F.; Johnson, M.; Schwake, A.

    1983-01-01

    Progress is reported in the development of the P-T-X diagram for 0 less than or = X less than or = 0.50 and in the development of techniques for measuring adiabats of phases of NH3-H2O. The partial phase diagram is presented, investigations of the compositions of ammonia ices are described, and methods for obtaining the infrared spectra of ices are discussed.

  5. Phase diagram of a bosonic ladder with two coupled chains

    International Nuclear Information System (INIS)

    Luthra, Meetu Sethi; Mishra, Tapan; Pai, Ramesh V.; Das, B. P.

    2008-01-01

    We study a bosonic ladder with two coupled chains using the finite-size density-matrix renormalization group method. We show that in a commensurate bosonic ladder the critical on-site interaction (U C ) for the superfluid to Mott insulator transition gets larger as the interchain hopping (t perpendicular ) increases. We analyze this quantum phase transition and obtain the phase diagram in the t perpendicular -U plane. We also consider the asymmetric case where the on-site interactions are different in the two chains and have shown that the system as a whole will not be in the Mott insulator phase unless both the chains have on-site interactions greater than the critical value

  6. Towards construction of quasi-binary UAI3-USi3 phase diagram

    International Nuclear Information System (INIS)

    Rafailov, Gennady; Uziel, Asaf; White, Avner; Meshi, Louisa; Dahan, Itzhak

    2014-01-01

    Ternary U-Al-Si system has been extensively investigated due to the high potential of Uranium alloyed with Silicon as low-enriched fuel. Another interest in the U-Al-Si ternary system originates from the use of Aluminum alloy, where Silicon is a major alloying element, as U-fuel cladding. In this system, UAl3 and USi3 phases are of special importance. Since UAl3 and USi3 are isostructural and follow the Hume-Rothery rules closely, it would be expected that their quasi-binary phase diagram will be isomorphous. However, previous studies have shown that this system does not display complete liquid and solid solubility. Moreover, conflicting results were reported regarding the phases found . In current work, several compositions were cast and then heat-treated in order to reach equilibrium for subsequent characterization of Si-rich part of the USi3-UAl3 quasi-binary phase diagram. The as-cast and heat-treated alloys were characterized by scanning and transmission electron microscopy and X-ray diffraction (XRD) methods. Quantitative results were obtained from Rietveld analysis performed on XRD data. The results show that the ordered U(Si,Al)3 phase, identified in an earlier study of the Al-rich region is present also in the Si-rich region (studied in present research). Furthermore, ordered phase exhibited substantial stability over quite large range of compositions and temperature. Our results unambiguously point out that this quasi-binary system contains an order-disorder transformation and not a miscibility gap at low temperatures in the studied range of compositions

  7. Quantum phase diagram of the integrable px+ipy fermionic superfluid

    DEFF Research Database (Denmark)

    Rombouts, Stefan; Dukelsky, Jorge; Ortiz, Gerardo

    2010-01-01

    transition, separating a strong-pairing from a weak-pairing phase. The mean-field solution allows to connect these results to other models with px+ipy pairing order. We define an experimentally accessible characteristic length scale, associated with the size of the Cooper pairs, that diverges......We determine the zero-temperature quantum phase diagram of a px+ipy pairing model based on the exactly solvable hyperbolic Richardson-Gaudin model. We present analytical and large-scale numerical results for this model. In the continuum limit, the exact solution exhibits a third-order quantum phase...... at the transition point, indicating that the phase transition is of a confinement-deconfinement type without local order parameter. We propose an experimental measurement to detect the transition. We show that this phase transition is not limited to the px+ipy pairing model but can be found in any representation...

  8. Magnetic phase diagram of ErGe 1-xSi x (0

    Science.gov (United States)

    Thuéry, P.; El Maziani, F.; Clin, M.; Schobinger-Papamantellos, P.; Buschow, K. H. J.

    1993-10-01

    The composition-temperature magnetic phase diagram of ErGe 1- xSi x (0 0.40. For 0.17 ≥ x ≤ 0.55, a first-order transition occurs as function of the temperature between these two phases. For x ≥ 0.65, a lock-in transition takes place at TIC, leading from the wavevector ( k' x,0, k' z) to (1/2,0,1/2), as was already observed in ErSi. Finally, for x < 0.17 or 0.55 < x < 0.65, the wavevectors of the incommensurate phases characterized by (0,0, kz) or ( k' x,0, k' z) respectively remain unchanged in the whole temperature range below TN. For x≥0.65, a small amount of a magnetic phase characterized by the wavevector (0,0, 1/2) coexists with the main phases, below a Néel temperature T' N slightly lower than TN. In all cases, the erbium magnetic moments are colinear along the orthorhombic α-axis; the arrangement of the moments in the commensurate phases is the same as in ErSi and the incommensurate orderings correspond to sine-wave amplitude modulations. A brief account on the theoretical interpretation of this phase diagram is finally given.

  9. Persistence of metastable vortex lattice domains in MgB2 in the presence of vortex motion.

    Science.gov (United States)

    Rastovski, C; Schlesinger, K J; Gannon, W J; Dewhurst, C D; DeBeer-Schmitt, L; Zhigadlo, N D; Karpinski, J; Eskildsen, M R

    2013-09-06

    Recently, extensive vortex lattice metastability was reported in MgB2 in connection with a second-order rotational phase transition. However, the mechanism responsible for these well-ordered metastable vortex lattice phases is not well understood. Using small-angle neutron scattering, we studied the vortex lattice in MgB2 as it was driven from a metastable to the ground state through a series of small changes in the applied magnetic field. Our results show that metastable vortex lattice domains persist in the presence of substantial vortex motion and directly demonstrate that the metastability is not due to vortex pinning. Instead, we propose that it is due to the jamming of counterrotated vortex lattice domains which prevents a rotation to the ground state orientation.

  10. Metastable Phase Separation and Concomitant Solute Redistribution of Liquid Fe-Cu-Sn Ternary Alloy

    International Nuclear Information System (INIS)

    Xiao-Mei, Zhang; Wei-Li, Wang; Ying, Ruan; Bing-Bo, Wei

    2010-01-01

    Liquid Fe-Cu-Sn ternary alloys with lower Sn contents are usually assumed to display a peritectic-type solidification process under equilibrium condition. Here we show that liquid Fe 47.5 Cu 47.5 Sn 5 ternary alloy exhibits a metastable immiscibility gap in the undercooling range of 51–329 K (0.19T L ). Macroscopic phase separation occurs once undercooling exceeds 196 K and causes the formation of a floating Fe-rich zone and a descending Cu-rich zone. Solute redistribution induces the depletion of Sn concentration in the Fe-rich zone and its enrichment in the Cu-rich zone. The primary Fe phase grows dendritically and its growth velocity increases with undercooling until the appearance of notable macrosegregation, but will decrease if undercooling further increases beyond 236 K. The microsegregation degrees of both solutes in Fe and Cu phases vary only slightly with undercooling. (condensed matter: structure, mechanical and thermal properties)

  11. Correlation between viscous-flow activation energy and phase diagram in four systems of Cu-based alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ning Shuang [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Jinan 250061 (China); Bian Xiufang, E-mail: xfbian@sdu.edu.c [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Jinan 250061 (China); Ren Zhenfeng [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Jinan 250061 (China)

    2010-09-01

    Activation energy is obtained from temperature dependence of viscosities by means of a fitting to the Arrhenius equation for liquid alloys of Cu-Sb, Cu-Te, Cu-Sn and Cu-Ag systems. We found that the changing trend of activation energy curves with concentration is similar to that of liquidus in the phase diagrams. Moreover, a maximum value of activation energy is in the composition range of the intermetallic phases and a minimum value of activation energy is located at the eutectic point. The correlation between the activation energy and the phase diagrams has been further discussed.

  12. Constitutive modeling of metastable austenitic stainless steel (CD-rom)

    NARCIS (Netherlands)

    Perdahcioglu, Emin Semih; Geijselaers, Hubertus J.M.; Huetink, Han; Boisse, P.

    2008-01-01

    A stress-update algorithm is developed for austenitic metastable steels which undergo phase evolution during deformation. The material initially comprises only the soft and ductile austenite phase which due to the phenomenon of mechanically induced martensitic transformation, transforms completely

  13. Molecular Simulation of the Phase Diagram of Methane Hydrate: Free Energy Calculations, Direct Coexistence Method, and Hyperparallel Tempering.

    Science.gov (United States)

    Jin, Dongliang; Coasne, Benoit

    2017-10-24

    Different molecular simulation strategies are used to assess the stability of methane hydrate under various temperature and pressure conditions. First, using two water molecular models, free energy calculations consisting of the Einstein molecule approach in combination with semigrand Monte Carlo simulations are used to determine the pressure-temperature phase diagram of methane hydrate. With these calculations, we also estimate the chemical potentials of water and methane and methane occupancy at coexistence. Second, we also consider two other advanced molecular simulation techniques that allow probing the phase diagram of methane hydrate: the direct coexistence method in the Grand Canonical ensemble and the hyperparallel tempering Monte Carlo method. These two direct techniques are found to provide stability conditions that are consistent with the pressure-temperature phase diagram obtained using rigorous free energy calculations. The phase diagram obtained in this work, which is found to be consistent with previous simulation studies, is close to its experimental counterpart provided the TIP4P/Ice model is used to describe the water molecule.

  14. Ground-state phase diagram of an (S, S') = (1, 2) spin-alternating chain with competing single-ion anisotropies

    International Nuclear Information System (INIS)

    Tonegawa, T; Okamoto, K; Sakai, T; Kaburagi, M

    2009-01-01

    Employing various numerical methods, we determine the ground-state phase diagram of an (S, S') = (1, 2) spin-alternating chain with antiferromagnetic nearest-neighboring exchange interactions and uniaxial single-ion anisotropies. The resulting phase diagram consists of eight kinds of phases including two phases which accompany the spontaneous breaking of the translational symmetry and a ferrimagnetic phase in which the ground-state magnetization varies continuously with the uniaxial single-ion anisotropy constants for the S=1 and S =2 spins. The appearance of these three phases is attributed to the competition between the uniaxial single-ion anisotropies of both spins.

  15. Metastable phase transformation and hcp-ω transformation pathways in Ti and Zr under high hydrostatic pressures

    International Nuclear Information System (INIS)

    Gao, Lei; Ding, Xiangdong; Sun, Jun; Lookman, Turab; Salje, E. K. H.

    2016-01-01

    The energy landscape of Zr at high hydrostatic pressure suggests that its transformation behavior is strongly pressure dependent. This is in contrast to the known transition mechanism in Ti, which is essentially independent of hydrostatic pressure. Generalized solid-state nudged elastic band calculations at constant pressure shows that α-Zr transforms like Ti only at the lowest pressure inside the stability field of ω-phase. Different pathways apply at higher pressures where the energy landscape contains several high barriers so that metastable states are expected, including the appearance of a transient bcc phase at ca. 23 GPa. The global driving force for the hcp-ω transition increases strongly with increasing pressure and reaches 23.7 meV/atom at 23 GPa. Much of this energy relates to the excess volume of the hcp phase compared with its ω phase.

  16. Metastable phase transformation and hcp-ω transformation pathways in Ti and Zr under high hydrostatic pressures

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Lei; Ding, Xiangdong, E-mail: dingxd@mail.xjtu.edu.cn, E-mail: ekhard@esc.cam.ac.uk; Sun, Jun [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Lookman, Turab [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Salje, E. K. H., E-mail: dingxd@mail.xjtu.edu.cn, E-mail: ekhard@esc.cam.ac.uk [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ (United Kingdom)

    2016-07-18

    The energy landscape of Zr at high hydrostatic pressure suggests that its transformation behavior is strongly pressure dependent. This is in contrast to the known transition mechanism in Ti, which is essentially independent of hydrostatic pressure. Generalized solid-state nudged elastic band calculations at constant pressure shows that α-Zr transforms like Ti only at the lowest pressure inside the stability field of ω-phase. Different pathways apply at higher pressures where the energy landscape contains several high barriers so that metastable states are expected, including the appearance of a transient bcc phase at ca. 23 GPa. The global driving force for the hcp-ω transition increases strongly with increasing pressure and reaches 23.7 meV/atom at 23 GPa. Much of this energy relates to the excess volume of the hcp phase compared with its ω phase.

  17. Thermal properties and reliability of eutectic mixture of stearic acid-acetamide as phase change material for latent heat storage

    International Nuclear Information System (INIS)

    Ma, Guixiang; Han, Lipeng; Sun, Jinhe; Jia, Yongzhong

    2017-01-01

    Highlights: • The system of stearic acid-acetamide binary mixtures were studied as phase change material. • The eutectic mixtures featured low melting temperatures and high latent heats of fusion for latent heat storage. • Solid-liquid phase diagrams for the system were constructed. • Negligible change in stability after 500 heating/cooling cycles. - Abstract: The thermal properties and reliability of the stearic acid (SA) with acetamide (AC) binary mixture were characterized using differential scanning calorimetry (DSC), powder X-ray diffraction (XRD), thermogravimetric analysis (TG) and Fourier transform infrared spectroscopy (FT-IR). The phase diagrams for the SA-AC binary mixture with AC in the metastable and the stable form were constructed. The eutectic system with stable AC is 0.604 mol fraction SA, and displayed a melting temperature (T m ) of 64.55 °C and latent heat of melting (ΔH m ) of 193.87 J·g −1 . The eutectic systems with metastable AC are 0.397 and 0.604 mol fraction SA. The melting temperatures are 62.23 °C and 62.54 °C, and latent heats of fusion are 222.10 J·g −1 and 194.28 J·g −1 , respectively. Following accelerated thermal cycling tests, TG and FT-IR analysis indicate that the eutectic mixture (χ SA = 0.397) with the metastable AC has good cyclic and thermal stability. The results show that the SA-AC eutectic mixture use as phase change material (PCM) possess good prospect for low temperature thermal energy storage (TES) applications.

  18. Optimization and calculation of the MCl-ZnCl2 (M = Li, Na, K) phase diagrams

    International Nuclear Information System (INIS)

    Romero-Serrano, Antonio; Hernandez-Ramirez, Aurelio; Cruz-Ramirez, Alejandro; Hallen-Lopez, Manuel; Zeifert, Beatriz

    2010-01-01

    An earlier structural model for binary silicate melts and glasses is extended to zinc chloride-alkali metal chloride systems. The evaluation of the available thermodynamic and phase diagrams data for the MCl-ZnCl 2 (M = Li, Na, K) binary systems have been carried out using the structural model for the liquid phase. This thermodynamic model is based on the assumption that each alkali chloride produces the depolymerization of ZnCl 2 network with a characteristic free-energy change. A least-squares optimization program permits all available thermodynamic and phase diagram data to be optimized simultaneously. In this manner, data for these binary systems have been analysed and represented with a small number of parameters.

  19. Stability limit of liquid water in metastable equilibrium with subsaturated vapors.

    Science.gov (United States)

    Wheeler, Tobias D; Stroock, Abraham D

    2009-07-07

    A pure liquid can reach metastable equilibrium with its subsaturated vapor across an appropriate membrane. This situation is analogous to osmotic equilibrium: the reduced chemical potential of the dilute phase (the subsaturated vapor) is compensated by a difference in pressure between the phases. To equilibrate with subsaturated vapor, the liquid phase assumes a pressure that is lower than its standard vapor pressure, such that the liquid phase is metastable with respect to the vapor phase. For sufficiently subsaturated vapors, the liquid phase can even assume negative pressures. The appropriate membrane for this metastable equilibrium must provide the necessary mechanical support to sustain the difference in pressure between the two phases, limit nonhomogeneous mechanisms of cavitation, and resist the entry of the dilutant (gases) into the pure phase (liquid). In this article, we present a study of the limit of stability of liquid water--the degree of subsaturation at which the liquid cavitates--in this metastable state within microscale voids embedded in hydrogel membranes. We refer to these structures as vapor-coupled voids (VCVs). In these VCVs, we observed that liquid water cavitated when placed in equilibrium with vapors of activity aw,vapairhumiditynucleation theory or molecular simulations (Pcav=-140 to -180 MPa). To determine the cause of the disparity between the observed and predicted stability limit, we examine experimentally the likelihood of several nonhomogeneous mechanisms of nucleation: (i) heterogeneous nucleation caused by hydrophobic patches on void walls, (ii) nucleation caused by the presence of dissolved solute, (iii) nucleation caused by the presence of pre-existing vapor nuclei, and (iv) invasion of air through the hydrogel membrane into the voids. We conclude that, of these possibilities, (i) and (ii) cannot be discounted, whereas (iii) and (iv) are unlikely to play a role in determining the stability limit.

  20. The Prognosis of the Phase Equilibrium Diagram of the System Al-Cu-Si

    Directory of Open Access Journals (Sweden)

    Florentina Cziple

    2007-10-01

    Full Text Available The paper presents a model for establishing the mathematical functions of the liquidus and solidus curves, from the binary diagrams Al-Si, Si-Cu, Cu-Al and their use in the prognosis of the phase equilibrium diagram from the ternary system Al-Cu-Si. We have studied the model of the non-ideal liquid solution of the regular type. The calculus and graphic plotting of the equations for the binary systems has been performed on the computer

  1. Extended skyrmion lattice scattering and long-time memory in the chiral magnet Fe1 -xCoxSi

    Science.gov (United States)

    Bannenberg, L. J.; Kakurai, K.; Qian, F.; Lelièvre-Berna, E.; Dewhurst, C. D.; Onose, Y.; Endoh, Y.; Tokura, Y.; Pappas, C.

    2016-09-01

    Small angle neutron scattering measurements on a bulk single crystal of the doped chiral magnet Fe1 -xCoxSi with x =0.3 reveal a pronounced effect of the magnetic history and cooling rates on the magnetic phase diagram. The extracted phase diagrams are qualitatively different for zero and field cooling and reveal a metastable skyrmion lattice phase outside the A phase for the latter case. These thermodynamically metastable skyrmion lattice correlations coexist with the conical phase and can be enhanced by increasing the cooling rate. They appear in a wide region of the phase diagram at temperatures below the A phase but also at fields considerably smaller or higher than the fields required to stabilize the A phase.

  2. Two-phase regime in the magnetic field-temperature phase diagram of a type-II superconductor

    International Nuclear Information System (INIS)

    Adams, L.L.A.; Halterman, Klaus; Valls, Oriol T.; Goldman, A.M.

    2004-01-01

    The magnetic field and temperature dependencies of the magnetic moments of superconducting crystals of V 3 Si have been studied. In a constant magnetic field and at temperatures somewhat below the superconducting transition temperature, the moments are hysteretic in temperature. However, the magnetic moment-magnetic field isotherms are reversible and exhibit features that formally resemble the pressure-volume isotherms of the liquid-gas transition. This suggests the existence of a first-order phase transition, a two-phase regime, and a critical point in the superconducting phase diagram. The two phases are disordered vortex configurations with the same magnetization, but with different vortex densities. The entropy change, determined from the data using the Clausius-Clapeyron equation, is consistent with estimates based on the difference in the vortex densities of the two phases

  3. Two-phase regime in the magnetic field-temperature phase diagram of a type-II superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Adams, L.L.A.; Halterman, Klaus; Valls, Oriol T.; Goldman, A.M

    2004-01-01

    The magnetic field and temperature dependencies of the magnetic moments of superconducting crystals of V{sub 3}Si have been studied. In a constant magnetic field and at temperatures somewhat below the superconducting transition temperature, the moments are hysteretic in temperature. However, the magnetic moment-magnetic field isotherms are reversible and exhibit features that formally resemble the pressure-volume isotherms of the liquid-gas transition. This suggests the existence of a first-order phase transition, a two-phase regime, and a critical point in the superconducting phase diagram. The two phases are disordered vortex configurations with the same magnetization, but with different vortex densities. The entropy change, determined from the data using the Clausius-Clapeyron equation, is consistent with estimates based on the difference in the vortex densities of the two phases.

  4. Strain hardening of cold-rolled lean-alloyed metastable ferritic-austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Papula, Suvi [Aalto University School of Engineering, Department of Mechanical Engineering, P.O. Box 14200, FI-00076 Aalto (Finland); Anttila, Severi [Centre for Advanced Steels Research, University of Oulu, P.O. Box 4200, 90014 Oulu (Finland); Talonen, Juho [Outokumpu Oyj, P.O. Box 245, FI-00181 Helsinki (Finland); Sarikka, Teemu; Virkkunen, Iikka; Hänninen, Hannu [Aalto University School of Engineering, Department of Mechanical Engineering, P.O. Box 14200, FI-00076 Aalto (Finland)

    2016-11-20

    Mechanical properties and strain hardening of two pilot-scale lean-alloyed ferritic-austenitic stainless steels having metastable austenite phase, present at 0.50 and 0.30 volume fractions, have been studied by means of tensile testing and nanoindentation. These ferritic-austenitic stainless steels have high strain-hardening capacity, due to the metastable austenite phase, which leads to an improved uniform elongation and higher tensile strength in comparison with most commercial lean duplex stainless steels. According to the results, even as low as 0.30 volume fraction of austenite seems efficient for achieving nearly 40% elongation. The austenite phase is initially the harder phase, and exhibits more strain hardening than the ferrite phase. The rate of strain hardening and the evolution of the martensite phase were found to depend on the loading direction: both are higher when strained in the rolling direction as compared to the transverse direction. Based on the mechanical testing, characterization of the microstructure by optical/electron microscopy, magnetic balance measurements and EBSD texture analysis, this anisotropy in mechanical properties of the cold-rolled metastable ferritic-austenitic stainless steels can be explained by the elongated dual-phase microstructure, fiber reinforcement effect of the harder austenite phase and the presence and interplay of rolling textures in the two phases.

  5. Oxidation phase growth diagram of vanadium oxides film fabricated by rapid thermal annealing

    Institute of Scientific and Technical Information of China (English)

    Tamura KOZO; Zheng-cao LI; Yu-quan WANG; Jie NI; Yin HU; Zheng-jun ZHANG

    2009-01-01

    Thermal evaporation deposited vanadium oxide films were annealed in air by rapid thermal annealing (RTP). By adjusting the annealing temperature and time, a series of vanadium oxide films with various oxidation phases and surface morphologies were fabricated, and an oxidation phase growth diagram was established. It was observed that different oxidation phases appear at a limited and continuous annealing condition range, and the morphologic changes are related to the oxidation process.

  6. Cyclic cosmology, conformal symmetry and the metastability of the Higgs

    Energy Technology Data Exchange (ETDEWEB)

    Bars, Itzhak [Department of Physics and Astronomy, University of Southern California, Los Angeles, CA 90089-0484 (United States); Steinhardt, Paul J., E-mail: steinh@princeton.edu [California Institute of Technology, Pasadena, CA 91125 (United States); Department of Physics and Princeton Center for Theoretical Physics, Princeton University, Princeton, NJ 08544 (United States); Turok, Neil [Perimeter Institute for Theoretical Physics, Waterloo, ON N2L 2Y5 (Canada)

    2013-10-07

    Recent measurements at the LHC suggest that the current Higgs vacuum could be metastable with a modest barrier (height (10{sup 10–12} GeV){sup 4}) separating it from a ground state with negative vacuum density of order the Planck scale. We note that metastability is problematic for standard bang cosmology but is essential for cyclic cosmology in order to end one cycle, bounce, and begin the next. In this Letter, motivated by the approximate scaling symmetry of the standard model of particle physics and the primordial large-scale structure of the universe, we use our recent formulation of the Weyl-invariant version of the standard model coupled to gravity to track the evolution of the Higgs in a regularly bouncing cosmology. We find a band of solutions in which the Higgs field escapes from the metastable phase during each big crunch, passes through the bang into an expanding phase, and returns to the metastable vacuum, cycle after cycle after cycle. We show that, due to the effect of the Higgs, the infinitely cycling universe is geodesically complete, in contrast to inflation.

  7. Studies on the QCD Phase Diagram at SPS and FAIR

    International Nuclear Information System (INIS)

    Blume, Christoph

    2013-01-01

    A review of results of the energy scan program at the CERN-SPS by the NA49 experiment is given. Presented are observables related to the search for a critical point in the QCD phase diagram and for the onset of deconfinement. Furthermore, the ongoing experimental program of NA61 at the CRRN-SPS and the plans of the CBM experiment at FAIR are discussed.

  8. Au-Ni nanoparticles: Phase diagram prediction, synthesis, characterization, and thermal stability

    Czech Academy of Sciences Publication Activity Database

    Sopoušek, J.; Kryštofová, A.; Premovic, M.; Zobač, O.; Postlerová, S.; Brož, P.; Buršík, Jiří

    2017-01-01

    Roč. 58, SEP (2017), s. 25-33 ISSN 0364-5916 R&D Projects: GA ČR(CZ) GA17-12844S; GA ČR(CZ) GA17-15405S Institutional support: RVO:68081723 Keywords : nanoalloy * CALPHAD * phase diagram Subject RIV: BJ - Thermodynamics OBOR OECD: Thermodynamics Impact factor: 1.600, year: 2016

  9. Modelling the continuous cooling transformation diagram of engineering steels using neural networks. Part I. Phase regions

    Energy Technology Data Exchange (ETDEWEB)

    Wolk, P.J. van der; Wang, J. [Delft Univ. of Technology (Netherlands); Sietsma, J.; Zwaag, S. van der [Delft Univ. of Technology, Lab. for Materials Science (Netherlands)

    2002-12-01

    A neural network model for the calculation of the phase regions of the continuous cooling transformation (CCT) diagram of engineering steels has been developed. The model is based on experimental CCT diagrams of 459 low-alloy steels, and calculates the CCT diagram as a function of composition and austenitisation temperature. In considering the composition, 9 alloying elements are taken into account. The model reproduces the original diagrams rather accurately, with deviations that are not larger than the average experimental inaccuracy of the experimental diagrams. Therefore, it can be considered an adequate alternative to the experimental determination of the CCT diagram of a certain steel within the composition range used. The effects of alloying elements can be quantified, either individually or in combination, with the model. Nonlinear composition dependencies are observed. (orig.)

  10. Global mean-field phase diagram of the spin-1 Ising ferromagnet in a random crystal field

    Science.gov (United States)

    Borelli, M. E. S.; Carneiro, C. E. I.

    1996-02-01

    We study the phase diagram of the mean-field spin-1 Ising ferromagnet in a uniform magnetic field H and a random crystal field Δi, with probability distribution P( Δi) = pδ( Δi - Δ) + (1 - p) δ( Δi). We analyse the effects of randomness on the first-order surfaces of the Δ- T- H phase diagram for different values of the concentration p and show how these surfaces are affected by the dilution of the crystal field.

  11. Consitutive modeling of metastable austenitic stainless steel

    NARCIS (Netherlands)

    Perdahcioglu, Emin Semih; Perdahcioglu, Emin Semih

    2008-01-01

    Metastable austenitic stainless steels combine high formability and high strength, which are generally opposing properties in materials. This property is a consequence of the martensitic phase transformation that takes place during deformation. This transformation is purely mechanically induced

  12. Phase diagram, thermodynamic investigations, and modelling of systems relevant to lithium-ion batteries

    International Nuclear Information System (INIS)

    Fuertauer, Siegfried; Beutl, Alexander; Flanorfer, Hans; Henriques, David; Giel, Hans; Markus, Thorsten

    2017-01-01

    This article reports on two consecutive joint projects titled ''Experimental Thermodynamics and Phase Relations of New Electrode Materials for Lithium-Ion Batteries'', which were performed in the framework of the WenDeLIB 1473 priority program ''Materials with new Design for Lithium Ion Batteries''. Hundreds of samples were synthesized using experimental techniques specifically developed to deal with highly reactive lithium and lithium-containing compounds to generate electrochemical, phase diagram and crystal structure data in the Cu-Li, Li-Sn, Li-Sb, Cu-Li-Sn, Cu-Li-Sb and selected oxide systems. The thermochemical and phase diagram data were subsequently used to develop self-consistent thermodynamic descriptions of several binary systems. In the present contribution, the experimental techniques, working procedures, results and their relevance to the development of new electrode materials for lithium ion batteries are discussed and summarized. The collaboration between the three groups has resulted in more than fifteen (15) published articles during the six-year funding period.

  13. Phase diagram, thermodynamic investigations, and modelling of systems relevant to lithium-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Fuertauer, Siegfried; Beutl, Alexander; Flanorfer, Hans [Vienna Univ. (Austria). Dept. of Inorganic Chemistry - Functional Materials; Li, Dajian; Cupid, Damian [Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen (Germany). Inst. for Applied Materials - Applied Materials Physics (IAM-AWP); Henriques, David; Giel, Hans; Markus, Thorsten [Mannheim Univ. of Applied Sciences (Germany). Inst. for Thermo- and Fluiddynamics

    2017-11-15

    This article reports on two consecutive joint projects titled ''Experimental Thermodynamics and Phase Relations of New Electrode Materials for Lithium-Ion Batteries'', which were performed in the framework of the WenDeLIB 1473 priority program ''Materials with new Design for Lithium Ion Batteries''. Hundreds of samples were synthesized using experimental techniques specifically developed to deal with highly reactive lithium and lithium-containing compounds to generate electrochemical, phase diagram and crystal structure data in the Cu-Li, Li-Sn, Li-Sb, Cu-Li-Sn, Cu-Li-Sb and selected oxide systems. The thermochemical and phase diagram data were subsequently used to develop self-consistent thermodynamic descriptions of several binary systems. In the present contribution, the experimental techniques, working procedures, results and their relevance to the development of new electrode materials for lithium ion batteries are discussed and summarized. The collaboration between the three groups has resulted in more than fifteen (15) published articles during the six-year funding period.

  14. Towards the QCD phase diagram

    CERN Document Server

    De Forcrand, Philippe; Forcrand, Philippe de; Philipsen, Owe

    2006-01-01

    We summarize our recent results on the phase diagram of QCD with N_f=2+1 quark flavors, as a function of temperature T and quark chemical potential \\mu. Using staggered fermions, lattices with temporal extent N_t=4, and the exact RHMC algorithm, we first determine the critical line in the quark mass plane (m_{u,d},m_s) where the finite temperature transition at \\mu=0 is second order. We confirm that the physical point lies on the crossover side of this line. Our data are consistent with a tricritical point at (m_{u,d},m_s) = (0,\\sim 500) MeV. Then, using an imaginary chemical potential, we determine in which direction this second-order line moves as the chemical potential is turned on. Contrary to standard expectations, we find that the region of first-order transitions shrinks in the presence of a chemical potential, which is inconsistent with the presence of a QCD critical point at small chemical potential. The emphasis is put on clarifying the translation of our results from lattice to physical units, and ...

  15. Urea-temperature phase diagrams capture the thermodynamics of denatured state expansion that accompany protein unfolding

    Science.gov (United States)

    Tischer, Alexander; Auton, Matthew

    2013-01-01

    We have analyzed the thermodynamic properties of the von Willebrand factor (VWF) A3 domain using urea-induced unfolding at variable temperature and thermal unfolding at variable urea concentrations to generate a phase diagram that quantitatively describes the equilibrium between native and denatured states. From this analysis, we were able to determine consistent thermodynamic parameters with various spectroscopic and calorimetric methods that define the urea–temperature parameter plane from cold denaturation to heat denaturation. Urea and thermal denaturation are experimentally reversible and independent of the thermal scan rate indicating that all transitions are at equilibrium and the van't Hoff and calorimetric enthalpies obtained from analysis of individual thermal transitions are equivalent demonstrating two-state character. Global analysis of the urea–temperature phase diagram results in a significantly higher enthalpy of unfolding than obtained from analysis of individual thermal transitions and significant cross correlations describing the urea dependence of and that define a complex temperature dependence of the m-value. Circular dichroism (CD) spectroscopy illustrates a large increase in secondary structure content of the urea-denatured state as temperature increases and a loss of secondary structure in the thermally denatured state upon addition of urea. These structural changes in the denatured ensemble make up ∼40% of the total ellipticity change indicating a highly compact thermally denatured state. The difference between the thermodynamic parameters obtained from phase diagram analysis and those obtained from analysis of individual thermal transitions illustrates that phase diagrams capture both contributions to unfolding and denatured state expansion and by comparison are able to decipher these contributions. PMID:23813497

  16. Numerical transfer-matrix study of a model with competing metastable states

    DEFF Research Database (Denmark)

    Fiig, T.; Gorman, B.M.; Rikvold, P.A.

    1994-01-01

    transition. A recently developed transfer-matrix formalism is applied to the model to obtain complex-valued ''constrained'' free-energy densities f(alpha). For particular eigenvectors of the transfer matrix, the f(alpha) exhibit finite-rangescaling behavior in agreement with the analytically continued...... 'metastable free-energy density This transfer-matrix approach gives a free-energy cost of nucleation that supports the proportionality relation for the decay rate of the metastable phase T proportional to\\Imf alpha\\, even in cases where two metastable states compete. The picture that emerges from this study...

  17. Nucleation of metastable aragonite CaCO3 in seawater.

    Science.gov (United States)

    Sun, Wenhao; Jayaraman, Saivenkataraman; Chen, Wei; Persson, Kristin A; Ceder, Gerbrand

    2015-03-17

    Predicting the conditions in which a compound adopts a metastable structure when it crystallizes out of solution is an unsolved and fundamental problem in materials synthesis, and one which, if understood and harnessed, could enable the rational design of synthesis pathways toward or away from metastable structures. Crystallization of metastable phases is particularly accessible via low-temperature solution-based routes, such as chimie douce and hydrothermal synthesis, but although the chemistry of the solution plays a crucial role in governing which polymorph forms, how it does so is poorly understood. Here, we demonstrate an ab initio technique to quantify thermodynamic parameters of surfaces and bulks in equilibrium with an aqueous environment, enabling the calculation of nucleation barriers of competing polymorphs as a function of solution chemistry, thereby predicting the solution conditions governing polymorph selection. We apply this approach to resolve the long-standing "calcite-aragonite problem"--the observation that calcium carbonate precipitates as the metastable aragonite polymorph in marine environments, rather than the stable phase calcite--which is of tremendous relevance to biomineralization, carbon sequestration, paleogeochemistry, and the vulnerability of marine life to ocean acidification. We identify a direct relationship between the calcite surface energy and solution Mg:Ca [corrected] ion concentrations, showing that the calcite nucleation barrier surpasses that of metastable aragonite in solutions with Mg:Ca ratios consistent with modern seawater, allowing aragonite to dominate the kinetics of nucleation. Our ability to quantify how solution parameters distinguish between polymorphs marks an important step toward the ab initio prediction of materials synthesis pathways in solution.

  18. Phase diagrams of Pr-C system

    International Nuclear Information System (INIS)

    Eremenko, V.N.; Velikanova, T.Ya.; Gordijchuk, O.V.

    1988-01-01

    Results of the X-ray phase, metallographic and high-temperature differential thermal analysis are used for the first time to plot a diagram of the Pr-C system state. Carbides are formed in the system: Pr 2 C 3 with the bcc-structure of the Pu 2 C 3 type and with the period a 0 = 0.85722+-0.00026 within the phase region + 2 C 3 >, a 0 0.86078+-0.00016 nm - within the region 2 C 3 >+α-PrC 2 ; dimorphous PrC 2 : α-PrC 2 with the bct-structure of the CaC 2 type and periods a 0.38517+-0.00011, c 0 = 0.64337+-0.00019 nm; β-PrC 2 with the fcc-structure, probably, of KCN type. Dicarbide melts congruently at 2320 grad. C, forming eutectics with graphite at 2254+-6 grad. C and composition of 71.5% (at.)C. It is polymorphously transformed in the phase region 2 C 3 > + 2 > at 1145+-4 grad. C, and in the region 2 >+C at 1134+-4 grad. C. Sesquicarbide melts incongruently at 1545+-4 grad. C. The eutectic reaction L ↔ + 2 C 3 > occurs at 800+-4 grad. C, the eutectic composition ∼ 15% (at.)C. The temperature of the eutectoid reaction ↔ + 2 C 3 > is 675+-6 grad C. The limiting carbon solubility in β-Pr is about 8 and in α-Pr it is about 5% (at.)

  19. An investigation of the Pd-Ag-Ru-Gd quaternary system phase diagram

    International Nuclear Information System (INIS)

    Zhang Kanghou; Xu Yun

    2005-01-01

    On the basis of the Ag-Pd-Gd, Ag-Ru-Gd and Pd-Ru-Gd ternary systems, the partial phase diagram of Pd-Ag-Ru-Gd (Gd 3 Gd and Ag 51 Gd 14 ; five two-phase regions: Pd(Ag) + (Ru), Pd(Ag) + Ag 51 Gd 14 (Ru) + Ag 51 Gd 14 , Pd(Ag) + Pd 3 Gd and (Ru) + Pd 3 Gd; three three-phase regions: Pd(Ag) + Pd 3 Gd + (Ru), Pd(Ag) + Ag 51 Gd 14 + (Ru) and (Ru) + Ag 51 Gd 14 + Pd 3 Gd; one four-phase region Pd(Ag) + (Ru) + Ag 51 Gd 14 + Pd 3 Gd. No new quaternary intermetallic phase has been found

  20. Metastable growth of pure wurtzite InGaAs microstructures.

    Science.gov (United States)

    Ng, Kar Wei; Ko, Wai Son; Lu, Fanglu; Chang-Hasnain, Connie J

    2014-08-13

    III-V compound semiconductors can exist in two major crystal phases, namely, zincblende (ZB) and wurtzite (WZ). While ZB is thermodynamically favorable in conventional III-V epitaxy, the pure WZ phase can be stable in nanowires with diameters smaller than certain critical values. However, thin nanowires are more vulnerable to surface recombination, and this can ultimately limit their performances as practical devices. In this work, we study a metastable growth mechanism that can yield purely WZ-phased InGaAs microstructures on silicon. InGaAs nucleates as sharp nanoneedles and expand along both axial and radial directions simultaneously in a core-shell fashion. While the base can scale from tens of nanometers to over a micron, the tip can remain sharp over the entire growth. The sharpness maintains a high local surface-to-volume ratio, favoring hexagonal lattice to grow axially. These unique features lead to the formation of microsized pure WZ InGaAs structures on silicon. To verify that the WZ microstructures are truly metastable, we demonstrate, for the first time, the in situ transformation from WZ to the energy-favorable ZB phase inside a transmission electron microscope. This unconventional core-shell growth mechanism can potentially be applied to other III-V materials systems, enabling the effective utilization of the extraordinary properties of the metastable wurtzite crystals.

  1. Determination of phase diagrams via computer simulation: methodology and applications to water, electrolytes and proteins

    International Nuclear Information System (INIS)

    Vega, C; Sanz, E; Abascal, J L F; Noya, E G

    2008-01-01

    In this review we focus on the determination of phase diagrams by computer simulation, with particular attention to the fluid-solid and solid-solid equilibria. The methodology to compute the free energy of solid phases will be discussed. In particular, the Einstein crystal and Einstein molecule methodologies are described in a comprehensive way. It is shown that both methodologies yield the same free energies and that free energies of solid phases present noticeable finite size effects. In fact, this is the case for hard spheres in the solid phase. Finite size corrections can be introduced, although in an approximate way, to correct for the dependence of the free energy on the size of the system. The computation of free energies of solid phases can be extended to molecular fluids. The procedure to compute free energies of solid phases of water (ices) will be described in detail. The free energies of ices Ih, II, III, IV, V, VI, VII, VIII, IX, XI and XII will be presented for the SPC/E and TIP4P models of water. Initial coexistence points leading to the determination of the phase diagram of water for these two models will be provided. Other methods to estimate the melting point of a solid, such as the direct fluid-solid coexistence or simulations of the free surface of the solid, will be discussed. It will be shown that the melting points of ice Ih for several water models, obtained from free energy calculations, direct coexistence simulations and free surface simulations agree within their statistical uncertainty. Phase diagram calculations can indeed help to improve potential models of molecular fluids. For instance, for water, the potential model TIP4P/2005 can be regarded as an improved version of TIP4P. Here we will review some recent work on the phase diagram of the simplest ionic model, the restricted primitive model. Although originally devised to describe ionic liquids, the model is becoming quite popular to describe the behavior of charged colloids

  2. Experimental investigation and thermodynamic calculations of the Ag–Bi–Ga phase diagram

    International Nuclear Information System (INIS)

    Minić, Duško; Premović, Milena; Manasijević, Dragan; Ćosović, Vladan; Živković, Dragana; Marković, Aleksandar

    2015-01-01

    Phase diagram of the Ag–Bi–Ga ternary system was investigated using differential thermal analysis (DTA), scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS), and x-ray powder diffraction (XRD) methods. Experimentally obtained results were compared with the results of thermodynamic prediction of phase equilibria based on calculation of phase diagram (CALPHAD) method. Phase transition temperatures of alloys with overall compositions along three selected vertical sections Ag–Bi 50 Ga 50 , Bi–Ag 50 Ga 50 and Ga–Ag 50 Bi 50 were measured by DTA. Liquidus temperatures were experimentally determined and compared with the results of thermodynamic calculation. Identification of coexisting phases in samples equilibrated at 200 °C was carried out using SEM-EDS and XRD methods. Obtained results were compared with the calculated isothermal section of the Ag–Bi–Ga ternary system at corresponding temperature. Calculated liquidus projection and invariant equilibria of the Ag–Bi–Ga ternary system were presented. The obtained values were found to be in a close agreement. - Highlights: • Calculated constitutive binary system based on literature data. • Experimentally determined (DTA) temperatures of phase transformations compared with analytical calculation. • Definition of three vertical sections Ag–Bi 50 Ga 50 , Bi–Ag 50 Ga 50 and Ga–Ag 50 Bi 50 . • Calculated horizontal section at 200 °C, confirmed by experimental SEM-EDS and XRD method. • Calculated liquidus surface projection and determined invariant reaction occurred in ternary Ag–Bi–Ga system

  3. Evaluating the phase diagram of superconductors with asymmetric spin populations

    International Nuclear Information System (INIS)

    Mannarelli, Massimo; Nardulli, Giuseppe; Ruggieri, Marco

    2006-01-01

    The phase diagram of a nonrelativistic fermionic system with imbalanced state populations interacting via a short-range S-wave attractive interaction is analyzed in the mean-field approximation. We determine the energetically favored state for different values of the mismatch between the two Fermi spheres in the weak- and strong-coupling regimes considering both homogeneous and nonhomogeneous superconductive states. We find that the homogeneous superconductive phase persists for values of the population imbalance that increase with increasing coupling strength. In the strong-coupling regime and for large population differences the energetically stable homogeneous phase is characterized by one gapless mode. We also find that the inhomogeneous superconductive phase characterized by the condensate Δ(x)∼Δ exp(iq·x) is energetically favored in a range of values of the chemical-potential mismatch that shrinks to zero in the strong-coupling regime

  4. Equilibrium phase diagram of the Ag-Au-Pb ternary system

    International Nuclear Information System (INIS)

    Hassam, S.; Bahari, Z.

    2005-01-01

    The phase diagram of the ternary system Ag-Au-Pb has been established using differential thermal analysis and X-ray powder diffraction analysis. Four vertical sections were studied: X Pb = 0.40, X Au /X Pb = 1/3, X Ag /X Au = 4/1 and X Ag /X Au = 1/1. Two ternary transitory peritectics and one ternary eutectic were characterized. A schematic representation of the ternary equilibria is given

  5. Phase diagram of a symmetric electron–hole bilayer system: a variational Monte Carlo study

    Science.gov (United States)

    Sharma, Rajesh O.; Saini, L. K.; Prasad Bahuguna, Bhagwati

    2018-05-01

    We study the phase diagram of a symmetric electron–hole bilayer system at absolute zero temperature and in zero magnetic field within the quantum Monte Carlo approach. In particular, we conduct variational Monte Carlo simulations for various phases, i.e. the paramagnetic fluid phase, the ferromagnetic fluid phase, the anti-ferromagnetic Wigner crystal phase, the ferromagnetic Wigner crystal phase and the excitonic phase, to estimate the ground-state energy at different values of in-layer density and inter-layer spacing. Slater–Jastrow style trial wave functions, with single-particle orbitals appropriate for different phases, are used to construct the phase diagram in the (r s , d) plane by finding the relative stability of trial wave functions. At very small layer separations, we find that the fluid phases are stable, with the paramagnetic fluid phase being particularly stable at and the ferromagnetic fluid phase being particularly stable at . As the layer spacing increases, we first find that there is a phase transition from the ferromagnetic fluid phase to the ferromagnetic Wigner crystal phase when d reaches 0.4 a.u. at r s   =  20, and before there is a return to the ferromagnetic fluid phase when d approaches 1 a.u. However, for r s   Wigner crystal is stable over the considered range of r s and d. We also find that as r s increases, the critical layer separations for Wigner crystallization increase.

  6. Phase diagram of a symmetric electron-hole bilayer system: a variational Monte Carlo study.

    Science.gov (United States)

    Sharma, Rajesh O; Saini, L K; Bahuguna, Bhagwati Prasad

    2018-05-10

    We study the phase diagram of a symmetric electron-hole bilayer system at absolute zero temperature and in zero magnetic field within the quantum Monte Carlo approach. In particular, we conduct variational Monte Carlo simulations for various phases, i.e. the paramagnetic fluid phase, the ferromagnetic fluid phase, the anti-ferromagnetic Wigner crystal phase, the ferromagnetic Wigner crystal phase and the excitonic phase, to estimate the ground-state energy at different values of in-layer density and inter-layer spacing. Slater-Jastrow style trial wave functions, with single-particle orbitals appropriate for different phases, are used to construct the phase diagram in the (r s , d) plane by finding the relative stability of trial wave functions. At very small layer separations, we find that the fluid phases are stable, with the paramagnetic fluid phase being particularly stable at [Formula: see text] and the ferromagnetic fluid phase being particularly stable at [Formula: see text]. As the layer spacing increases, we first find that there is a phase transition from the ferromagnetic fluid phase to the ferromagnetic Wigner crystal phase when d reaches 0.4 a.u. at r s   =  20, and before there is a return to the ferromagnetic fluid phase when d approaches 1 a.u. However, for r s   Wigner crystal is stable over the considered range of r s and d. We also find that as r s increases, the critical layer separations for Wigner crystallization increase.

  7. Computational phase diagrams of noble gas hydrates under pressure

    Energy Technology Data Exchange (ETDEWEB)

    Teeratchanan, Pattanasak, E-mail: s1270872@sms.ed.ac.uk; Hermann, Andreas, E-mail: a.hermann@ed.ac.uk [Centre for Science at Extreme Conditions and SUPA, School of Physics and Astronomy, The University of Edinburgh, Edinburgh EH9 3FD (United Kingdom)

    2015-10-21

    We present results from a first-principles study on the stability of noble gas-water compounds in the pressure range 0-100 kbar. Filled-ice structures based on the host water networks ice-I{sub h}, ice-I{sub c}, ice-II, and C{sub 0} interacting with guest species He, Ne, and Ar are investigated, using density functional theory (DFT) with four different exchange-correlation functionals that include dispersion effects to various degrees: the non-local density-based optPBE-van der Waals (vdW) and rPW86-vdW2 functionals, the semi-empirical D2 atom pair correction, and the semi-local PBE functional. In the He-water system, the sequence of stable phases closely matches that seen in the hydrogen hydrates, a guest species of comparable size. In the Ne-water system, we predict a novel hydrate structure based on the C{sub 0} water network to be stable or at least competitive at relatively low pressure. In the Ar-water system, as expected, no filled-ice phases are stable; however, a partially occupied Ar-C{sub 0} hydrate structure is metastable with respect to the constituents. The ability of the different DFT functionals to describe the weak host-guest interactions is analysed and compared to coupled cluster results on gas phase systems.

  8. Magnetization plateaus and phase diagrams of the Ising model on the Shastry–Sutherland lattice

    Energy Technology Data Exchange (ETDEWEB)

    Deviren, Seyma Akkaya, E-mail: sadeviren@nevsehir.edu.tr

    2015-11-01

    The magnetization properties of a two-dimensional spin-1/2 Ising model on the Shastry–Sutherland lattice are studied within the effective-field theory (EFT) with correlations. The thermal behavior of the magnetizations is investigated in order to characterize the nature (the first- or second-order) of the phase transitions as well as to obtain the phase diagrams of the model. The internal energy, specific heat, entropy and free energy of the system are also examined numerically as a function of the temperature in order to confirm the stability of the phase transitions. The applied field dependence of the magnetizations is also examined to find the existence of the magnetization plateaus. For strong enough magnetic fields, several magnetization plateaus are observed, e.g., at 1/9, 1/8, 1/3 and 1/2 of the saturation. The phase diagrams of the model are constructed in two different planes, namely (h/|J|, |J′|/|J|) and (h/|J|, T/|J|) planes. It was found that the model exhibits first- and second-order phase transitions; hence tricitical point is also observed in additional to the zero-temperature critical point. Moreover the Néel order (N), collinear order (C) and ferromagnetic (F) phases are also found with appropriate values of the system parameters. The reentrant behavior is also obtained whenever model displays two Néel temperatures. These results are compared with some theoretical and experimental works and a good overall agreement has been obtained. - Highlights: • Magnetization properties of spin-1/2 Ising model on SS lattice are investigated. • The magnetization plateaus of the 1/9, 1/8, 1/3 and 1/2 are observed. • The phase diagrams of the model are constructed in two different planes. • The model exhibits the tricitical and zero-temperature critical points. • The reentrant behavior is obtained whenever model displays two Neel temperatures.

  9. Isothermal α″ formation in β metastable titanium alloys

    International Nuclear Information System (INIS)

    Aeby-Gautier, E.; Settefrati, A.; Bruneseaux, F.; Appolaire, B.; Denand, B.; Dehmas, M.; Geandier, G.; Boulet, P.

    2013-01-01

    Highlights: ► Isothermal kinetics of orthorhombic α″ formation is characterized by HEXRD. ► Cell parameters of parent and product phases are obtained. ► Partitioning of solutes during the transformation and the ageing is discussed. -- Abstract: Thanks to time resolved high energy X-ray diffraction, isothermal decomposition of β metastable phase was studied, directly after solution treatment in the β temperature range, for temperatures ranging from 300 to 450 °C for two beta metastable alloys (Ti 17 and Ti 5553). The formation of an orthorhombic α″ phase is clearly identified at the beginning of the transformation whatever the alloy studied. If transformation occurs at the higher temperature an evolution of α″ is observed toward the hexagonal α phase. The phase amounts and the mean cell parameters of each phase were quantified by the Rietveld refinement method. The obtained cell parameters evolutions and the orthorhombicity of α″ are discussed. Moreover, the orthorhombicity of α″ compared to that obtained for stress induced martensite may indicate a slight partitioning of solutes in isothermal α″

  10. Isothermal α″ formation in β metastable titanium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Aeby-Gautier, E., E-mail: Elisabeth.Gautier@mines.inpl-nancy.fr [Institut Jean Lamour, UMR CNRS Nancy Université, UPVM 7198, Nancy (France); Settefrati, A. [Institut Jean Lamour, UMR CNRS Nancy Université, UPVM 7198, Nancy (France); Airbus Operations, Materials and Processes, Toulouse (France); Bruneseaux, F. [Institut Jean Lamour, UMR CNRS Nancy Université, UPVM 7198, Nancy (France); Appolaire, B. [Laboratoire d’Etudes des Microstructures ONERA – CNRS Chatillon (France); Denand, B.; Dehmas, M.; Geandier, G.; Boulet, P. [Institut Jean Lamour, UMR CNRS Nancy Université, UPVM 7198, Nancy (France)

    2013-11-15

    Highlights: ► Isothermal kinetics of orthorhombic α″ formation is characterized by HEXRD. ► Cell parameters of parent and product phases are obtained. ► Partitioning of solutes during the transformation and the ageing is discussed. -- Abstract: Thanks to time resolved high energy X-ray diffraction, isothermal decomposition of β metastable phase was studied, directly after solution treatment in the β temperature range, for temperatures ranging from 300 to 450 °C for two beta metastable alloys (Ti 17 and Ti 5553). The formation of an orthorhombic α″ phase is clearly identified at the beginning of the transformation whatever the alloy studied. If transformation occurs at the higher temperature an evolution of α″ is observed toward the hexagonal α phase. The phase amounts and the mean cell parameters of each phase were quantified by the Rietveld refinement method. The obtained cell parameters evolutions and the orthorhombicity of α″ are discussed. Moreover, the orthorhombicity of α″ compared to that obtained for stress induced martensite may indicate a slight partitioning of solutes in isothermal α″.

  11. Phase diagrams for an ideal gas mixture of fermionic atoms and bosonic molecules

    DEFF Research Database (Denmark)

    Williams, J. E.; Nygaard, Nicolai; Clark, C. W.

    2004-01-01

    We calculate the phase diagrams for a harmonically trapped ideal gas mixture of fermionic atoms and bosonic molecules in chemical and thermal equilibrium, where the internal energy of the molecules can be adjusted relative to that of the atoms by use of a tunable Feshbach resonance. We plot...... diagrams obtained in recent experiments on the Bose-Einstein condensation to Bardeen-Cooper-Schrieffer crossover, in which the condensate fraction is plotted as a function of the initial temperature of the Fermi gas measured before a sweep of the magnetic field through the resonance region....

  12. Cluster Mean-Field Approach to the Steady-State Phase Diagram of Dissipative Spin Systems

    Directory of Open Access Journals (Sweden)

    Jiasen Jin

    2016-07-01

    Full Text Available We show that short-range correlations have a dramatic impact on the steady-state phase diagram of quantum driven-dissipative systems. This effect, never observed in equilibrium, follows from the fact that ordering in the steady state is of dynamical origin, and is established only at very long times, whereas in thermodynamic equilibrium it arises from the properties of the (free energy. To this end, by combining the cluster methods extensively used in equilibrium phase transitions to quantum trajectories and tensor-network techniques, we extend them to nonequilibrium phase transitions in dissipative many-body systems. We analyze in detail a model of spin-1/2 on a lattice interacting through an XYZ Hamiltonian, each of them coupled to an independent environment that induces incoherent spin flips. In the steady-state phase diagram derived from our cluster approach, the location of the phase boundaries and even its topology radically change, introducing reentrance of the paramagnetic phase as compared to the single-site mean field where correlations are neglected. Furthermore, a stability analysis of the cluster mean field indicates a susceptibility towards a possible incommensurate ordering, not present if short-range correlations are ignored.

  13. Asymmetric simple exclusion process with position-dependent hopping rates: Phase diagram from boundary-layer analysis.

    Science.gov (United States)

    Mukherji, Sutapa

    2018-03-01

    In this paper, we study a one-dimensional totally asymmetric simple exclusion process with position-dependent hopping rates. Under open boundary conditions, this system exhibits boundary-induced phase transitions in the steady state. Similarly to totally asymmetric simple exclusion processes with uniform hopping, the phase diagram consists of low-density, high-density, and maximal-current phases. In various phases, the shape of the average particle density profile across the lattice including its boundary-layer parts changes significantly. Using the tools of boundary-layer analysis, we obtain explicit solutions for the density profile in different phases. A detailed analysis of these solutions under different boundary conditions helps us obtain the equations for various phase boundaries. Next, we show how the shape of the entire density profile including the location of the boundary layers can be predicted from the fixed points of the differential equation describing the boundary layers. We discuss this in detail through several examples of density profiles in various phases. The maximal-current phase appears to be an especially interesting phase where the boundary layer flows to a bifurcation point on the fixed-point diagram.

  14. c-T phase diagram and Landau free energies of (AgAu)55 nanoalloy via neural-network molecular dynamic simulations.

    Science.gov (United States)

    Chiriki, Siva; Jindal, Shweta; Bulusu, Satya S

    2017-10-21

    For understanding the structure, dynamics, and thermal stability of (AgAu) 55 nanoalloys, knowledge of the composition-temperature (c-T) phase diagram is essential due to the explicit dependence of properties on composition and temperature. Experimentally, generating the phase diagrams is very challenging, and therefore theoretical insight is necessary. We use an artificial neural network potential for (AgAu) 55 nanoalloys. Predicted global minimum structures for pure gold and gold rich compositions are lower in energy compared to previous reports by density functional theory. The present work based on c-T phase diagram, surface area, surface charge, probability of isomers, and Landau free energies supports the enhancement of catalytic property of Ag-Au nanoalloys by incorporation of Ag up to 24% by composition in Au nanoparticles as found experimentally. The phase diagram shows that there is a coexistence temperature range of 70 K for Ag 28 Au 27 compared to all other compositions. We propose the power spectrum coefficients derived from spherical harmonics as an order parameter to calculate Landau free energies.

  15. Sintering of YBaCu0, implications of the phase diagram

    International Nuclear Information System (INIS)

    Gervais, M.; Douy, A.; Dubois, B.; Coutures, J.P.; Odier, P.

    1989-01-01

    The motivations of this experimental work are to underline the implications between the phases diagram constitution and the sintering of YBaCu0 superconductors. This preliminary work is focussed on the solid → liquid transformations of this system, in the vicinity of the (123) phase. Two transformations are observed at 915 and 935 0 C depending of the composition of the compound. They both have an important role on the sintering process and the chemical homogeneity of the ceramic. No such transformations seems to occur in the domain (123)-(211)-BaCu0 2 , the sintered sample has therefore a better chemical homogeneity [fr

  16. Color superconductivity. Phase diagrams and Goldstone bosons in the color-flavor locked phase

    Energy Technology Data Exchange (ETDEWEB)

    Kleinhaus, Verena

    2009-04-29

    The phase diagram of strongly interacting matter is studied with great experimental and theoretical effort and is one of the most fascinating research areas in modern particle physics. It is believed that color superconducting phases, in which quarks form Cooper pairs, appear at very high densities and low temperatures. Such phases could appear in the cores of neutron stars. In this work color superconducting phases are studied within the Nambu-Jona-Lasinio model. First of all, the phase diagram of neutral matter in beta equilibrium is calculated for two different diquark couplings. To this end, we determine the dynamical quark masses self-consistently together with the order parameters of color superconductivity. The interplay between neutrality and quark masses results in an interesting phase structure, in particular for the smaller diquark coupling. In the following, we additionally include a conserved lepton number to map the situation in the first few seconds of the evolution of a protoneutron star when neutrinos are trapped. This has a huge influence on the phase structure and favors the 2SC phase compared to the CFL phase. In the second part of this work we concentrate on the CFL phase which is characterized by a special symmetry breaking pattern. The properties of the resulting nine pseudoscalar Goldstone bosons (GB) are studied by solving the Bethe-Salpeter equation for quark-quark scattering. The GB are the lowest-lying excitations in the CFL phase and therefore play an important role for the thermodynamics of the system. The properties of the GB can also be described by the low-energy effective theory (LEET) for the CFL phase. There the respective low-energy constants are derived for asymptotically high densities where the strong force is weak and can be treated perturbatively. Our aim is the comparison of our results with these predictions, on the one hand to check our model in the weak-coupling limit and on the other hand to derive information about

  17. Color superconductivity: Phase diagrams and Goldstone bosons in the color-flavor locked phase

    International Nuclear Information System (INIS)

    Kleinhaus, Verena

    2009-01-01

    The phase diagram of strongly interacting matter is studied with great experimental and theoretical effort and is one of the most fascinating research areas in modern particle physics. It is believed that color superconducting phases, in which quarks form Cooper pairs, appear at very high densities and low temperatures. Such phases could appear in the cores of neutron stars. In this work color superconducting phases are studied within the Nambu-Jona-Lasinio model. First of all, the phase diagram of neutral matter in beta equilibrium is calculated for two different diquark couplings. To this end, we determine the dynamical quark masses self-consistently together with the order parameters of color superconductivity. The interplay between neutrality and quark masses results in an interesting phase structure, in particular for the smaller diquark coupling. In the following, we additionally include a conserved lepton number to map the situation in the first few seconds of the evolution of a protoneutron star when neutrinos are trapped. This has a huge influence on the phase structure and favors the 2SC phase compared to the CFL phase. In the second part of this work we concentrate on the CFL phase which is characterized by a special symmetry breaking pattern. The properties of the resulting nine pseudoscalar Goldstone bosons (GB) are studied by solving the Bethe-Salpeter equation for quark-quark scattering. The GB are the lowest-lying excitations in the CFL phase and therefore play an important role for the thermodynamics of the system. The properties of the GB can also be described by the low-energy effective theory (LEET) for the CFL phase. There the respective low-energy constants are derived for asymptotically high densities where the strong force is weak and can be treated perturbatively. Our aim is the comparison of our results with these predictions, on the one hand to check our model in the weak-coupling limit and on the other hand to derive information about

  18. Revision of the Ge–Ti phase diagram and structural stability of the new phase Ge{sub 4}Ti{sub 5}

    Energy Technology Data Exchange (ETDEWEB)

    Bittner, Roland W. [University of Vienna, Department of Inorganic Chemistry/Materials Chemistry, Währingerstraße 42, 1090 Wien (Austria); Colinet, Catherine [Science et Ingénierie des Matériaux et Procédés, Grenoble INP, UJF, CNRS, 38402 Saint Martin d’Hères Cedex (France); Tedenac, Jean-Claude [Institut de Chimie Moléculaire et des Matériaux I.C.G., UMR-CNRS 5253, Université Montpellier II, Place E. Bataillon, 34095 Montpellier Cedex 5 (France); Richter, Klaus W., E-mail: klaus.richter@univie.ac.at [University of Vienna, Department of Inorganic Chemistry/Materials Chemistry, Währingerstraße 42, 1090 Wien (Austria)

    2013-11-15

    Highlights: •New compound Ge{sub 4}Ti{sub 5} found by experiments and by DFT ground state calculations. •Enthalpies of formation calculated for different Ge–Ti compounds. •Modifications of the Ge–Ti phase diagram suggested. -- Abstract: The binary phase diagram Ge–Ti was investigated experimentally by powder X-ray diffraction, scanning electron microscopy including EDX analysis, and differential thermal analysis. Total energies of the compounds GeTi{sub 3}, GeTi{sub 2}, Ge{sub 3}Ti{sub 5}, Ge{sub 4}Ti{sub 5}, Ge{sub 5}Ti{sub 6}, GeTi and Ge{sub 2}Ti were calculated for various structure types employing electronic density-functional theory (DFT). Experimental studies as well as electronic calculations show the existence of a new phase Ge{sub 4}Ti{sub 5} (Ge{sub 4}Sm{sub 5}-type, oP36, Pnma) which is formed in a solid state reaction Ge{sub 3}Ti{sub 5} + Ge{sub 5}Ti{sub 6} = Ge{sub 4}Ti{sub 5}. In addition, a significant homogeneity range was observed for the compound Ge{sub 3}Ti{sub 5} and the composition of the liquid phase in the eutectic reaction L = Ge + Ge{sub 2}Ti was found to be at significant higher Ge-content (97.5 at.% Ge) than reported in previous studies. Based on these new results, a modified phase diagram Ge–Ti is suggested. The zero-temperature lattice parameters and the formation enthalpies determined by DTF calculations were found to be in good agreement with experimental data.

  19. Comparison of forcefields for molecular dynamics simulations of hydrocarbon phase diagrams

    Science.gov (United States)

    Pisarev, V. V.; Zakharov, S. A.

    2018-01-01

    Molecular dynamics calculations of vapor-liquid equilibrium of methane-n-butane mixture are performed. Three force-field models are tested: the TraPPE-UA united-atom forcefield, LOPLS-AA all-atom forcefield and a fully flexible version of the TraPPE-EH all-atom forcefield. All those forcefields reproduce well the composition of liquid phase in the mixture as a function of pressure at the 300 K isotherm, while significant discrepancies from experimental data are observed in the saturated vapor compositions with OPLS-AA and TraPPE-UA forcefields. The best agreement with the experimental phase diagram is found with TraPPE-EH forcefield which accurately reproduces compositions of both liquid and vapor phase. This forcefield can be recommended for simulation of two-phase hydrocarbon systems.

  20. Orientation dependence of phase diagrams and physical properties in epitaxial Ba0.6Sr0.4TiO3 films

    Science.gov (United States)

    Qiu, J. H.; Zhao, T. X.; Chen, Z. H.; Yuan, N. Y.; Ding, J. N.

    2018-04-01

    Orientation dependence of phase diagrams and physical properties of Ba0.6Sr0.4TiO3 films are investigated by using a phenomenological Landau-Devonshire theory. New ferroelectric phases, such as the tetragonal a1 phase and the orthorhombic a2 c phase in (110) oriented film and the monoclinic MA phase in (111) oriented film, appear in the "misfit strain-temperature" phase diagrams as compared with (001) oriented film. Moreover, the phase diagrams of (110) and (111) oriented films are more complex than that of (001) oriented film due to the nonlinear coupling terms appeared in the thermodynamic potential. The dielectric and piezoelectric properties largely depend on the misfit strain and orientation. (111) oriented film has the better piezoelectric property than (110) oriented film. Furthermore, the compressive misfit strain is prone to induce the larger piezoelectric property than tensile misfit strain.

  1. Phase diagram and equation of state of TiH2 at high pressures and high temperatures

    International Nuclear Information System (INIS)

    Endo, Naruki; Saitoh, Hiroyuki; Machida, Akihiko; Katayama, Yoshinori; Aoki, Katsutoshi

    2013-01-01

    Highlights: ► We determined the phase diagram of TiH 2 at high pressures and high temperatures. ► Compression induced stain inhibited the phase transition from the bct to fcc phase. ► The phase boundary was appropriately determined using a sample with heat treatment. ► The high temperature Birch–Murnaghan equation of state of fcc TiH 2 was firstly determined. - Abstract: We determined the phase diagram and the equation of state (EoS) of TiH 2 at high pressures up to 8.7 GPa and high temperatures up to 600 °C by in situ synchrotron radiation X-ray diffraction measurements. Compression induced strain inhibited the phase transition from the low-temperature bct phase to the high-temperature fcc phase, making the phase diagram difficult to determine. However, heating around 600 °C relieved the strain, and the phase boundary between the bct and fcc phases was elucidated. The phase transition temperature at ambient pressure increased from around room temperature to 200 °C at 8.7 GPa. The high temperature Birch–Murnaghan EoS was determined for the fcc phase. With the pressure derivative of the bulk modulus K′ 0 = 4.0, the following parameters were obtained: ambient bulk modulus K 0 = 97.7 ± 0.2 GPa, ambient unit cell of the fcc phase V 0 = 88.57 ± 0.02 Å 3 , temperature derivative of the bulk modulus at constant pressure (∂K/∂T) P = −0.01 ± 0.02, and volumetric thermal expansivity α = a + bT with a = 2.62 ± 1.4 × 10 −5 and b = 5.5 ± 4.5 × 10 −8 . K 0 of fcc TiH 2 was close to those for pure Ti and bct TiH 2 reported in previous studies.

  2. Simple method for the calculation and use of CVD phase diagrams with applications to the Ti-B-Cl-H system, 1200 to 8000K

    International Nuclear Information System (INIS)

    Randich, E.; Gerlach, T.M.

    1980-03-01

    A simple method for calculating multi-component gas-solid equilibrium phase diagrams for chemical vapor deposition (CVD) systems is presented. The method proceeds in three steps: dtermination of stable solid assemblages, evaluation of gas-solid stability relations, and calcuation of conventional phase diagrams using a new free energy minimization technique. The phase diagrams can be used to determine (1) bulk compositions and phase fields accessible by CVD techniques; (2) expected condensed phases for various starting gas mixtures; and (3) maximum equilibrium yields for specific CVD process variables. The three step thermodynamic method is used to calcuate phase diagrams for the example CVD system Ti-B-Cl-H at 1200 and 800 0 K. Examples of applications of the diagrams for yield optimization and experimental accessibility studies are presented and discussed. Experimental verification of the TiB 2 + Gas/Gas phase field boundary at 1200 0 K, H/Cl = 1 confirms the calculated boundary and indicates that equilibrium is nearly and rapidly approached under laboratory conditions

  3. Optimization and calculation of the MCl-ZnCl{sub 2} (M = Li, Na, K) phase diagrams

    Energy Technology Data Exchange (ETDEWEB)

    Romero-Serrano, Antonio, E-mail: romeroipn@hotmail.com [Metallurgy and Materials Department, Instituto Politecnico Nacional-ESIQIE, Apdo. P. 118-431, 07051 Mexico, D.F. (Mexico); Hernandez-Ramirez, Aurelio, E-mail: aurelioh@hotmail.com [Metallurgy and Materials Department, Instituto Politecnico Nacional-ESIQIE, Apdo. P. 118-431, 07051 Mexico, D.F. (Mexico); Cruz-Ramirez, Alejandro, E-mail: alcruzr@ipn.mx [Metallurgy and Materials Department, Instituto Politecnico Nacional-ESIQIE, Apdo. P. 118-431, 07051 Mexico, D.F. (Mexico); Hallen-Lopez, Manuel, E-mail: j_hallen@yahoo.com [Metallurgy and Materials Department, Instituto Politecnico Nacional-ESIQIE, Apdo. P. 118-431, 07051 Mexico, D.F. (Mexico); Zeifert, Beatriz, E-mail: bzeifert@yahoo.com [Metallurgy and Materials Department, Instituto Politecnico Nacional-ESIQIE, Apdo. P. 118-431, 07051 Mexico, D.F. (Mexico)

    2010-10-20

    An earlier structural model for binary silicate melts and glasses is extended to zinc chloride-alkali metal chloride systems. The evaluation of the available thermodynamic and phase diagrams data for the MCl-ZnCl{sub 2} (M = Li, Na, K) binary systems have been carried out using the structural model for the liquid phase. This thermodynamic model is based on the assumption that each alkali chloride produces the depolymerization of ZnCl{sub 2} network with a characteristic free-energy change. A least-squares optimization program permits all available thermodynamic and phase diagram data to be optimized simultaneously. In this manner, data for these binary systems have been analysed and represented with a small number of parameters.

  4. The phase diagrams of KCaF3 and NaMgF3 by ab initio simulations

    Science.gov (United States)

    Jakymiw, Clément; Vočadlo, Lidunka; Dobson, David P.; Bailey, Edward; Thomson, Andrew R.; Brodholt, John P.; Wood, Ian G.; Lindsay-Scott, Alex

    2018-04-01

    ABF3 compounds have been found to make valuable low-pressure analogues for high-pressure silicate phases that are present in the Earth's deep interior and that may also occur in the interiors of exoplanets. The phase diagrams of two of these materials, KCaF3 and NaMgF3, have been investigated in detail by static ab initio computer simulations based on density functional theory. Six ABF3 polymorphs were considered, as follows: the orthorhombic perovskite structure (GdFeO3-type; space group Pbnm); the orthorhombic CaIrO3 structure ( Cmcm; commonly referred to as the "post-perovskite" structure); the orthorhombic Sb2S3 and La2S3 structures (both Pmcn); the hexagonal structure previously suggested in computer simulations of NaMgF3 ( P63/ mmc); the monoclinic structure found to be intermediate between the perovskite and CaIrO3 structures in CaRhO3 ( P21/ m). Volumetric and axial equations of state of all phases considered are presented. For KCaF3, as expected, the perovskite phase is shown to be the most thermodynamically stable at atmospheric pressure. With increasing pressure, the relative stability of the KCaF3 phases then follows the sequence: perovskite → La2S3 structure → Sb2S3 structure → P63/ mmc structure; the CaIrO3 structure is never the most stable form. Above about 2.6 GPa, however, none of the KCaF3 polymorphs are stable with respect to dissociation into KF and CaF2. The possibility that high-pressure KCaF3 polymorphs might exist metastably at 300 K, or might be stabilised by chemical substitution so as to occur within the standard operating range of a multi-anvil press, is briefly discussed. For NaMgF3, the transitions to the high-pressure phases occur at pressures outside the normal range of a multi-anvil press. Two different sequences of transitions had previously been suggested from computer simulations. With increasing pressure, we find that the relative stability of the NaMgF3 phases follows the sequence: perovskite → CaIrO3 structure → Sb2

  5. Tuning the phase diagrams: the miscibility studies of multilactate liquid crystalline compounds

    Czech Academy of Sciences Publication Activity Database

    Bubnov, Alexej; Tykarska, M.; Hamplová, Věra; Kurp, K.

    2016-01-01

    Roč. 89, č. 9 (2016), s. 885-893 ISSN 0141-1594 R&D Projects: GA ČR GA13-14133S; GA MŠk(CZ) LD14007; GA ČR GA15-02843S Grant - others:EU - ICT(XE) COST Action IC1208 Institutional support: RVO:68378271 Keywords : miscibility study * binary mixture * polar smectic phase * lactic acid derivative * miscibility study * phase diagram * self-assembling behaviour Subject RIV: JJ - Other Materials Impact factor: 1.060, year: 2016

  6. Electron band theory predictions and the construction of phase diagrams

    International Nuclear Information System (INIS)

    Watson, R.E.; Bennett, L.H.; Davenport, J.W.; Weinert, M.

    1985-01-01

    The a priori theory of metals is yielding energy results which are relevant to the construction of phase diagrams - to the solution phases as well as to line compounds. There is a wide range in the rigor of the calculations currently being done and this is discussed. Calculations for the structural stabilities (fcc vs bcc vs hcp) of the elemental metals, quantities which are employed in the constructs of the terminal phases, are reviewed and shown to be inconsistent with the values currently employed in such constructs (also see Miodownik elsewhere in this volume). Finally, as an example, the calculated heats of formation are compared with experiment for PtHf, IrTa and OsW, three compounds with the same electron to atom ratio but different bonding properties

  7. Phase diagram and magnetic relaxation phenomena in Cu2OSeO3

    Science.gov (United States)

    Qian, F.; Wilhelm, H.; Aqeel, A.; Palstra, T. T. M.; Lefering, A. J. E.; Brück, E. H.; Pappas, C.

    2016-08-01

    We present an investigation of the magnetic-field-temperature phase diagram of Cu2OSeO3 based on dc magnetization and ac susceptibility measurements covering a broad frequency range of four orders of magnitude, from very low frequencies reaching 0.1 Hz up to 1 kHz. The experiments were performed in the vicinity of Tc=58.2 K and around the skyrmion lattice A phase. At the borders between the different phases the characteristic relaxation times reach several milliseconds and the relaxation is nonexponential. Consequently the borders between the different phases depend on the specific criteria and frequency used and an unambiguous determination is not possible.

  8. A model for metastable magnetism in the hidden-order phase of URu2Si2

    Science.gov (United States)

    Boyer, Lance; Yakovenko, Victor M.

    2018-01-01

    We propose an explanation for the experiment by Schemm et al. (2015) where the polar Kerr effect (PKE), indicating time-reversal symmetry (TRS) breaking, was observed in the hidden-order (HO) phase of URu2Si2. The PKE signal on warmup was seen only if a training magnetic field was present on cool-down. Using a Ginzburg-Landau model for a complex order parameter, we show that the system can have a metastable ferromagnetic state producing the PKE, even if the HO ground state respects TRS. We predict that a strong reversed magnetic field should reset the PKE to zero.

  9. Modelling the material behaviour of metastable stainless

    NARCIS (Netherlands)

    Datta, K.; Geijselaers, Hubertus J.M.; Post, J.; Beyer, J.; Huetink, Han; Cesar de Sa, Jose M.A.; Santos, Abel D.

    2007-01-01

    Metastable austenitic stainless steels are designed to be thermodynamically unstable such that deformation even at room temperatures can bring about a change in the phase of face centred cubic austenite to either hexagonal close packed martensite and/or to body centred cubic martensite. This solid

  10. Correlation between thermodynamic anomalies and pathways of ice nucleation in supercooled water

    International Nuclear Information System (INIS)

    Singh, Rakesh S.; Bagchi, Biman

    2014-01-01

    The well-known classical nucleation theory (CNT) for the free energy barrier towards formation of a nucleus of critical size of the new stable phase within the parent metastable phase fails to take into account the influence of other metastable phases having density/order intermediate between the parent metastable phase and the final stable phase. This lacuna can be more serious than capillary approximation or spherical shape assumption made in CNT. This issue is particularly significant in ice nucleation because liquid water shows rich phase diagram consisting of two (high and low density) liquid phases in supercooled state. The explanations of thermodynamic and dynamic anomalies of supercooled water often invoke the possible influence of a liquid-liquid transition between two metastable liquid phases. To investigate both the role of thermodynamic anomalies and presence of distinct metastable liquid phases in supercooled water on ice nucleation, we employ density functional theoretical approach to find nucleation free energy barrier in different regions of phase diagram. The theory makes a number of striking predictions, such as a dramatic lowering of nucleation barrier due to presence of a metastable intermediate phase and crossover in the dependence of free energy barrier on temperature near liquid-liquid critical point. These predictions can be tested by computer simulations as well as by controlled experiments

  11. Phase diagram of a lattice of pancake vortex molecules

    International Nuclear Information System (INIS)

    Tanaka, Y.; Crisan, A.; Shivagan, D.D.; Iyo, A.; Shirage, P.M.; Tokiwa, K.; Watanabe, T.; Terada, N.

    2009-01-01

    On a superconducting bi-layer with thickness much smaller than the penetration depth, λ, a vortex molecule might form. A vortex molecule is composed of two fractional vortices and a soliton wall. The soliton wall can be regarded as a Josephson vortex missing magnetic flux (degenerate Josephson vortex) due to an incomplete shielding. The magnetic energy carried by fractional vortices is less than in the conventional vortex. This energy gain can pay a cost to form a degenerate Josephson vortex. The phase diagram of the vortex molecule is rich because of its rotational freedom.

  12. Hydration Phase Diagram of Clay Particles from Molecular Simulations.

    Science.gov (United States)

    Honorio, Tulio; Brochard, Laurent; Vandamme, Matthieu

    2017-11-07

    Adsorption plays a fundamental role in the behavior of clays. Because of the confinement between solid clay layers on the nanoscale, adsorbed water is structured in layers, which can occupy a specific volume. The transition between these states is intimately related to key features of clay thermo-hydro-mechanical behavior. In this article, we consider the hydration states of clays as phases and the transition between these states as phase changes. The thermodynamic formulation supporting this idea is presented. Then, the results from grand canonical Monte Carlo simulations of sodium montmorillonite are used to derive hydration phase diagrams. The stability analysis presented here explains the coexistence of different hydration states at clay particle scale and improves our understanding of the irreversibilities of clay thermo-hydro-mechanical behavior. Our results provide insights into the mechanics of the elementary constituents of clays, which is crucial for a better understanding of the macroscopic behavior of clay-rich rocks and soils.

  13. Thermodynamic study of sodium-iron oxides. Part 2. Ternary phase diagram of the Na-Fe-O system

    International Nuclear Information System (INIS)

    Huang, Jintao; Furukawa, Tomohiro; Aoto, Kazumi

    2003-01-01

    Studies on ternary phase diagrams of the Na-Fe-O system have been carried out from the thermodynamic point of view. Thermodynamic data of main ternary Na-Fe oxides Na 4 FeO 3 (s), Na 3 FeO 3 (s), Na 5 FeO 4 (s) and Na 8 Fe 2 O 7 (s) have been assessed. A user database has been created by reviewing literature data together with recent DSC and vapor pressure measurements by the present authors. New ternary phase diagrams of the Na-Fe-O system have been constructed from room temperature to 1000K. Stable conditions of the ternary oxides at 800K were presented in predominance diagram as functions of oxygen pressure and sodium pressure

  14. The NaNO2-NaNO3 system – a revised phase diagram

    DEFF Research Database (Denmark)

    Berg, Rolf W.; Kerridge, D.H.; Larsen, Peter Halvor

    2004-01-01

    Three earlier determinations of the phase diagram of the sodium nitrite/sodium nitrate binary system resulted in considerably different conclusions, ranging from simple eutectic to continuous solid solution types, together with different sub-solidus lines. Recent melting enthalpy measurements hav...

  15. Experimental investigation and thermodynamic calculations of the Ag–Bi–Ga phase diagram

    Energy Technology Data Exchange (ETDEWEB)

    Minić, Duško, E-mail: dminic65@open.telekom.rs [University in Priština, Faculty of Technical Science, Kos. Mitrovica (Serbia); Premović, Milena [University in Priština, Faculty of Technical Science, Kos. Mitrovica (Serbia); Manasijević, Dragan [University of Belgrade, Technical Faculty, Bor (Serbia); Ćosović, Vladan [University of Belgrade, Institute of Chemistry, Technology and Metallurgy, Belgrade (Serbia); Živković, Dragana [University of Belgrade, Technical Faculty, Bor (Serbia); Marković, Aleksandar [University in Priština, Faculty of Technical Science, Kos. Mitrovica (Serbia)

    2015-10-15

    Phase diagram of the Ag–Bi–Ga ternary system was investigated using differential thermal analysis (DTA), scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS), and x-ray powder diffraction (XRD) methods. Experimentally obtained results were compared with the results of thermodynamic prediction of phase equilibria based on calculation of phase diagram (CALPHAD) method. Phase transition temperatures of alloys with overall compositions along three selected vertical sections Ag–Bi{sub 50}Ga{sub 50}, Bi–Ag{sub 50}Ga{sub 50} and Ga–Ag{sub 50}Bi{sub 50} were measured by DTA. Liquidus temperatures were experimentally determined and compared with the results of thermodynamic calculation. Identification of coexisting phases in samples equilibrated at 200 °C was carried out using SEM-EDS and XRD methods. Obtained results were compared with the calculated isothermal section of the Ag–Bi–Ga ternary system at corresponding temperature. Calculated liquidus projection and invariant equilibria of the Ag–Bi–Ga ternary system were presented. The obtained values were found to be in a close agreement. - Highlights: • Calculated constitutive binary system based on literature data. • Experimentally determined (DTA) temperatures of phase transformations compared with analytical calculation. • Definition of three vertical sections Ag–Bi{sub 50}Ga{sub 50}, Bi–Ag{sub 50}Ga{sub 50} and Ga–Ag{sub 50}Bi{sub 50}. • Calculated horizontal section at 200 °C, confirmed by experimental SEM-EDS and XRD method. • Calculated liquidus surface projection and determined invariant reaction occurred in ternary Ag–Bi–Ga system.

  16. Phase diagrams of a nonequilibrium mixed spin-3/2 and spin-2 Ising system in an oscillating magnetic field

    International Nuclear Information System (INIS)

    Keskin, Mustafa; Polat, Yasin

    2009-01-01

    The phase diagrams of the nonequilibrium mixed spin-3/2 and spin-2 Ising ferrimagnetic system on square lattice under a time-dependent external magnetic field are presented by using the Glauber-type stochastic dynamics. The model system consists of two interpenetrating sublattices of spins σ=3/2 and S=2, and we take only nearest-neighbor interactions between pairs of spins. The system is in contact with a heat bath at absolute temperature T abs and the exchange of energy with the heat bath occurs via one-spin flip of the Glauber dynamics. First, we investigate the time variations of average order parameters to find the phases in the system and then the thermal behavior of the dynamic order parameters to obtain the dynamic phase transition (DPT) points as well as to characterize the nature (first- or second-order) phase transitions. The dynamic phase diagrams are presented in two different planes. Phase diagrams contain paramagnetic (p), ferrimagnetic (i 1 , i 2 , i 3 ) phases, and three coexistence or mixed phase regions, namely i 1 +p, i 2 +p and i 3 +p mixed phases that strongly depend on interaction parameters.

  17. Phase diagrams of a nonequilibrium mixed spin-3/2 and spin-2 Ising system in an oscillating magnetic field

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-12-15

    The phase diagrams of the nonequilibrium mixed spin-3/2 and spin-2 Ising ferrimagnetic system on square lattice under a time-dependent external magnetic field are presented by using the Glauber-type stochastic dynamics. The model system consists of two interpenetrating sublattices of spins {sigma}=3/2 and S=2, and we take only nearest-neighbor interactions between pairs of spins. The system is in contact with a heat bath at absolute temperature T{sub abs} and the exchange of energy with the heat bath occurs via one-spin flip of the Glauber dynamics. First, we investigate the time variations of average order parameters to find the phases in the system and then the thermal behavior of the dynamic order parameters to obtain the dynamic phase transition (DPT) points as well as to characterize the nature (first- or second-order) phase transitions. The dynamic phase diagrams are presented in two different planes. Phase diagrams contain paramagnetic (p), ferrimagnetic (i{sub 1}, i{sub 2}, i{sub 3}) phases, and three coexistence or mixed phase regions, namely i{sub 1}+p, i{sub 2}+p and i{sub 3}+p mixed phases that strongly depend on interaction parameters.

  18. Magnetic phase diagram of UNi2Si2 under magnetic field and high-pressure

    International Nuclear Information System (INIS)

    Honda, F.; Oomi, G.; Svoboda, P.; Syshchenko, A.; Sechovsky, V.; Khmelevski, S.; Divis, M.; Andreev, A.V.; Takeshita, N.; Mori, N.; Menovsky, A.A.

    2001-01-01

    Measurements of electrical resistance under high pressure and neutron diffraction in high-magnetic field of single crystalline UNi 2 Si 2 have been performed. We have found the analogy between the p-T and B-T magnetic phase diagrams. It is also found that the propagation vector q Z of incommensurate antiferromagnetic phase decreases with increasing magnetic field. A new pronounced pressure-induced incommensurate-commensurate magnetic phase transition has been detected

  19. Magnetic phase diagram of UNi.sub.2./sub.Si.sub.2./sub. under pressure

    Czech Academy of Sciences Publication Activity Database

    Syshchenko, O.; Khmelevski, S.; Diviš, M.; Sechovský, V.; Honda, F.; Oomi, G.; Andreev, Alexander V.; Kamarád, Jiří; Šebek, Josef; Menovsky, A. A.

    2001-01-01

    Roč. 304, - (2001), s. 477-482 ISSN 0921-4526 R&D Projects: GA ČR GA106/99/0183 Institutional research plan: CEZ:AV0Z1010914 Keywords : U intermetallics * antiferromagnetism * magnetic phase diagram * electrical resistivity * pressure effects on magnetic phases * axial Ising model Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.663, year: 2001

  20. Experimental study of the ternary Ag-Cu-In phase diagram

    International Nuclear Information System (INIS)

    Bahari, Zahra; Elgadi, Mohamed; Rivet, Jacques; Dugue, Jerome

    2009-01-01

    The phase diagram of the Ag-Cu-In system was investigated using powder X-ray diffraction (XRD), differential scanning calorimetry (DSC) and electron probe microanalysis (EPMA). Two isothermal sections (at 510 and 607 deg. C) and 15 isopletic sections were studied. The results showed seven ternary peritectics, one ternary eutectic and one ternary metatectic. A complete reaction scheme was constructed, the valleys were drawn and the liquidus surfaces were derived from DSC data in the entire composition range.

  1. Experimental study of the ternary Ag-Cu-In phase diagram

    Energy Technology Data Exchange (ETDEWEB)

    Bahari, Zahra [Laboratoire de chimie physique et minerale, Faculte des sciences pharmaceutiques et biologiques, Universite Paris Descartes, avenue de l' Observatoire, 75006 Paris (France); Laboratoire de chimie du solide mineral (LCSM), Faculte des sciences, Universite Mohamed 1er, Route Sidi Maafa, B.P. 524, Oujda, Maroc (Morocco); Elgadi, Mohamed [Laboratoire de chimie du solide mineral (LCSM), Faculte des sciences, Universite Mohamed 1er, Route Sidi Maafa, B.P. 524, Oujda, Maroc (Morocco); Rivet, Jacques [Laboratoire de chimie physique et minerale, Faculte des sciences pharmaceutiques et biologiques, Universite Paris Descartes, avenue de l' Observatoire, 75006 Paris (France); Dugue, Jerome [Laboratoire de chimie physique et minerale, Faculte des sciences pharmaceutiques et biologiques, Universite Paris Descartes, avenue de l' Observatoire, 75006 Paris (France)], E-mail: jerome.dugue@univ-paris5.fr

    2009-05-27

    The phase diagram of the Ag-Cu-In system was investigated using powder X-ray diffraction (XRD), differential scanning calorimetry (DSC) and electron probe microanalysis (EPMA). Two isothermal sections (at 510 and 607 deg. C) and 15 isopletic sections were studied. The results showed seven ternary peritectics, one ternary eutectic and one ternary metatectic. A complete reaction scheme was constructed, the valleys were drawn and the liquidus surfaces were derived from DSC data in the entire composition range.

  2. Phase diagram of Se-CaIn4Se7 system

    International Nuclear Information System (INIS)

    Musaeva, R.I.; Aliev, I.I; Ismailova, F.I; Aliev, A.A

    2011-01-01

    Full text: The Se-CaIn 4 Se 7 system has been studied using methods of differential thermal analysis, X-ray diffraction, micro structural analysis, density measurements and its phase diagram has been constructed. It has been established that the section Se-CaIn 4 Se 7 is a quasibinary section of the ternary system Ca-In-Se. At room temperature, on the basis of CaIn 2 Se 4 and Se no solid solution has been found

  3. Phase diagram for the Kuramoto model with van Hemmen interactions.

    Science.gov (United States)

    Kloumann, Isabel M; Lizarraga, Ian M; Strogatz, Steven H

    2014-01-01

    We consider a Kuramoto model of coupled oscillators that includes quenched random interactions of the type used by van Hemmen in his model of spin glasses. The phase diagram is obtained analytically for the case of zero noise and a Lorentzian distribution of the oscillators' natural frequencies. Depending on the size of the attractive and random coupling terms, the system displays four states: complete incoherence, partial synchronization, partial antiphase synchronization, and a mix of antiphase and ordinary synchronization.

  4. Phase diagram of carbon and the factors limiting the quantity and size of natural diamonds

    Science.gov (United States)

    Blank, Vladimir D.; Churkin, Valentin D.; Kulnitskiy, Boris A.; Perezhogin, Igor A.; Kirichenko, Alexey N.; Denisov, Viktor N.; Erohin, Sergey V.; Sorokin, Pavel B.; Popov, Mikhail Yu

    2018-03-01

    Phase diagrams of carbon, and those focusing on the graphite-to-diamond transitional conditions in particular, are of great interest for fundamental and applied research. The present study introduces a number of experiments carried out to convert graphite under high-pressure conditions, showing a formation of stable phase of fullerene-type onions cross-linked by sp3-bonds in the 55-115 GPa pressure range instead of diamonds formation (even at temperature 2000-3000 K) and the already formed diamonds turn into carbon onions. Our results refute the widespread idea that diamonds can form at any pressure from 2.2 to 1000 GPa. The phase diagram built within this study allows us not only to explain the existing numerous experimental data on the formation of diamond from graphite, but also to make assumptions about the conditions of its growth in Earth’s crust.

  5. ± J D-vector spin glass phase diagram and critical behaviour

    International Nuclear Information System (INIS)

    Coutinho, S.; Lyra, M.L.

    1988-01-01

    The phase diagram and the correlation length exponents of the ± J D-Vector Spin-Glass model are studied in the framework of the real space mean field renormalization group method. The boundary between the spin-glass (SG) and the ferromagnetic (F) phases is obtained from the renormalization flow equations and shows a reentrant behaviour over the SG region. This re-entrance increases smoothly with the coordination number. Analytical expressions for the thermal and the correlation length exponents are calculated straight forwardly for all fixed points and figures are presented and compared with availables results from other methods and data. (author) [pt

  6. 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.

  7. Proton dynamics and the phase diagram of dense water ice.

    Science.gov (United States)

    Hernandez, J-A; Caracas, R

    2018-06-07

    All the different phases of water ice between 2 GPa and several megabars are based on a single body-centered cubic sub-lattice of oxygen atoms. They differ only by the behavior of the hydrogen atoms. In this study, we investigate the dynamics of the H atoms at high pressures and temperatures in water ice from first-principles molecular dynamics simulations. We provide a detailed analysis of the O-H⋯O bonding dynamics over the entire stability domain of the body-centered cubic (bcc) water ices and compute transport properties and vibrational density-of-states. We report the first ab initio evidence for a plastic phase of water and we propose a coherent phase diagram for bcc water ices compatible with the two groups of melting curves and with the multiple anomalies reported in ice VII around 15 GPa.

  8. Thin film phase diagram of iron nitrides grown by molecular beam epitaxy

    Science.gov (United States)

    Gölden, D.; Hildebrandt, E.; Alff, L.

    2017-01-01

    A low-temperature thin film phase diagram of the iron nitride system is established for the case of thin films grown by molecular beam epitaxy and nitrided by a nitrogen radical source. A fine-tuning of the nitridation conditions allows for growth of α ‧ -Fe8Nx with increasing c / a -ratio and magnetic anisotropy with increasing x until almost phase pure α ‧ -Fe8N1 thin films are obtained. A further increase of nitrogen content below the phase decomposition temperature of α ‧ -Fe8N (180 °C) leads to a mixture of several phases that is also affected by the choice of substrate material and symmetry. At higher temperatures (350 °C), phase pure γ ‧ -Fe4N is the most stable phase.

  9. Effect of elastic compliances and higher order Landau coefficients on the phase diagram of single domain epitaxial Pb(Zr,TiO3 (PZT thin films

    Directory of Open Access Journals (Sweden)

    M. Mtebwa

    2014-12-01

    Full Text Available We report the qualitative study of the influence of both elastic compliances and higher order terms of Landau free energy potential on the phase diagram of Pb(Zr0.5Ti0.5O3 thin films by using a single domain Landau theory. Although the impact of elastic compliances and higher order terms of the Landau free energy potential on the phase diagram of ferroelectric thin films are known, the sensitivity of the phase diagram of PZT thin film on these parameters have not been reported. It is demonstrated that, while values of elastic compliances affect the positions of the phase boundaries including phase transition temperature of the cubic phase; higher order terms can potentially introduce an a1a2-phase previously predicted in PbTiO3 phase diagram.

  10. Assessment of the thermodynamic properties and phase diagram of the Bi–Pd system

    Czech Academy of Sciences Publication Activity Database

    Vřešťál, J.; Pinkas, J.; Watson, A.; Scott, A.; Houserová, Jana; Kroupa, Aleš

    2006-01-01

    Roč. 30, č. 1 (2006), s. 14-17 ISSN 0364-5916 R&D Projects: GA MŠk(CZ) OC 531.002 Institutional research plan: CEZ:AV0Z2041904 Keywords : phase diagram * thermodynamic modelling Subject RIV: BJ - Thermodynamics Impact factor: 1.432, year: 2006

  11. Comprehensive phase diagram of two-dimensional space charge doped Bi2Sr2CaCu2O8+x.

    Science.gov (United States)

    Sterpetti, Edoardo; Biscaras, Johan; Erb, Andreas; Shukla, Abhay

    2017-12-12

    The phase diagram of hole-doped high critical temperature superconductors as a function of doping and temperature has been intensively studied with chemical variation of doping. Chemical doping can provoke structural changes and disorder, masking intrinsic effects. Alternatively, a field-effect transistor geometry with an electrostatically doped, ultra-thin sample can be used. However, to probe the phase diagram, carrier density modulation beyond 10 14  cm -2 and transport measurements performed over a large temperature range are needed. Here we use the space charge doping method to measure transport characteristics from 330 K to low temperature. We extract parameters and characteristic temperatures over a large doping range and establish a comprehensive phase diagram for one-unit-cell-thick BSCCO-2212 as a function of doping, temperature and disorder.

  12. APPLICATION OF VORONOI DIAGRAM TO MASK-BASED INTERCEPTING PHASE-SPACE MEASUREMENTS

    Energy Technology Data Exchange (ETDEWEB)

    Halavanau, A. [Fermilab; Ha, G. [POSTECH

    2017-05-19

    Intercepting multi-aperture masks (e.g. pepper pot or multislit mask) combined with a downstream transversedensity diagnostics (e.g. based on optical transition radiation or employing scintillating media) are commonly used for characterizing the phase space of charged particle beams and the associated emittances. The required data analysis relies on precise calculation of the RMS sizes and positions of the beamlets originated from the mask which drifted up to the analyzing diagnostics. Voronoi diagram is an efficient method for splitting a plane into subsets according to the distances between given vortices. The application of the method to analyze data from pepper pot and multislit mask based measurement is validated via numerical simulation and applied to experimental data acquired at the Argonne Wakefield Accelerator (AWA) facility. We also discuss the application of the Voronoi diagrams to quantify transverselymodulated beams distortion.

  13. Capability of X-ray diffraction for the study of microstructure of metastable thin films

    Directory of Open Access Journals (Sweden)

    David Rafaja

    2014-11-01

    Full Text Available Metastable phases are often used to design materials with outstanding properties, which cannot be achieved with thermodynamically stable compounds. In many cases, the metastable phases are employed as precursors for controlled formation of nanocomposites. This contribution shows how the microstructure of crystalline metastable phases and the formation of nanocomposites can be concluded from X-ray diffraction experiments by taking advantage of the high sensitivity of X-ray diffraction to macroscopic and microscopic lattice deformations and to the dependence of the lattice deformations on the crystallographic direction. The lattice deformations were determined from the positions and from the widths of the diffraction lines, the dependence of the lattice deformations on the crystallographic direction from the anisotropy of the line shift and the line broadening. As an example of the metastable system, the supersaturated solid solution of titanium nitride and aluminium nitride was investigated, which was prepared in the form of thin films by using cathodic arc evaporation of titanium and aluminium in a nitrogen atmosphere. The microstructure of the (Ti,AlN samples under study was tailored by modifying the [Al]/[Ti] ratio in the thin films and the surface mobility of the deposited species.

  14. Assessment of thermodynamic properties and phase diagram in the Ag–In–Pd system

    Czech Academy of Sciences Publication Activity Database

    Zemanová, A.; Semenova, O.; Kroupa, Aleš; Vřešťál, J.; Chandrasekaran, K.; Richter, K. W.; Ipser, H.

    2007-01-01

    Roč. 15, č. 1 (2007), s. 77-84 ISSN 0966-9795 R&D Projects: GA MŠk(CZ) OC 532.001 Institutional research plan: CEZ:AV0Z20410507 Keywords : phase diagrams * ternary alloy systems * prediction Subject RIV: BJ - Thermodynamics Impact factor: 2.219, year: 2007

  15. Suppression of metastable-phase inclusion in N-polar (0001¯) InGaN/GaN multiple quantum wells grown by metalorganic vapor phase epitaxy

    International Nuclear Information System (INIS)

    Shojiki, Kanako; Iwabuchi, Takuya; Kuboya, Shigeyuki; Choi, Jung-Hun; Tanikawa, Tomoyuki; Hanada, Takashi; Katayama, Ryuji; Matsuoka, Takashi; Usami, Noritaka

    2015-01-01

    The metastable zincblende (ZB) phase in N-polar (0001 ¯ ) (−c-plane) InGaN/GaN multiple quantum wells (MQWs) grown by metalorganic vapor phase epitaxy is elucidated by the electron backscatter diffraction measurements. From the comparison between the −c-plane and Ga-polar (0001) (+c-plane), the −c-plane MQWs were found to be suffered from the severe ZB-phase inclusion, while ZB-inclusion is negligible in the +c-plane MQWs grown under the same growth conditions. The ZB-phase inclusion is a hurdle for fabricating the −c-plane light-emitting diodes because the islands with a triangular shape appeared on a surface in the ZB-phase domains. To improve the purity of stable wurtzite (WZ)-phase, the optimum conditions were investigated. The ZB-phase is dramatically eliminated with decreasing the V/III ratio and increasing the growth temperature. To obtain much-higher-quality MQWs, the thinner InGaN wells and the hydrogen introduction during GaN barriers growth were tried. Consequently, MQWs with almost pure WZ phase and with atomically smooth surface have been demonstrated

  16. Phase diagram of structure of radial electric field in helical plasmas

    International Nuclear Information System (INIS)

    Toda, S.; Itoh, K.

    2002-01-01

    A set of transport equations in toroidal helical plasmas is analyzed, including the bifurcation of the radial electric field. Multiple solutions of E r for the ambipolar condition induces domains of different electric polarities. A structure of the domain interface is analyzed and a phase diagram is obtained in the space of the external control parameters. The region of the reduction of the anomalous transport is identified. (author)

  17. Decadal variability and metastability in the Southern Hemisphere

    Science.gov (United States)

    O'Kane, Terence; Risbey, James; Franzke, Christian; Horenko, Illia; Monselesan, Didier

    2014-05-01

    An examination of systematic changes in the metastability of the southern hemisphere 500hPa circulation is performed using both cluster analysis techniques and split flow blocking indices. The cluster methodology is a purely data-driven approach for parametrisation whereby a multi-scale approximation to non-stationary dynamical processes is achieved through optimal sequences of locally stationary fast Vector Auto-Regressive Factor (VARX) processes and some slow (or persistent) hidden process switching between them. Comparison is made with blocking indices commonly used in weather forecasting and climate analysis to identify dynamically relevant metastable regimes in the 500hPa circulation in both reanalysis and AMIP model data sets. Our analysis characterises the metastable regime in both reanalysis and model data sets prior to 1978 as positive and negative phases of a hemispheric mid-latitude blocking state with the Southern Annular Mode (SAM) associated with a transition state. Post 1978, SAM emerges as a true metastable state replacing the negative phase of the hemispheric blocking pattern. The hidden state frequency of occurrences exhibits strong trends. The blocking pattern dominates in the early 1980s then gradually decreases. There is a corresponding increase in the SAM frequency of occurrence. This trend is largely evident in the reanalysis summer and spring but was not evident in the AMIP data set. Non-stationary cluster analysis was then further used to identify the Southern Oceans response to the systematic changes in the mid-latitude atmospheric circulation and identify dynamical regimes associated with subsurface thermocline anomalies which were found to teleconnect the Pacific and Atlantic regions of the Antarctic Circumpolar Current (ACC).

  18. Bifurcation and phase diagram of turbulence constituted from three different scale-length modes

    Energy Technology Data Exchange (ETDEWEB)

    Itoh, S.-I.; Kitazawa, A.; Yagi, M. [Kyushu Univ., Research Inst. for Applied Mechanics, Kasuga, Fukuoka (Japan); Itoh, K. [National Inst. for Fusion Science, Toki, Gifu (Japan)

    2002-04-01

    Cases where three kinds of fluctuations having the different typical scale-lengths coexist are analyzed, and the statistical theory of strong turbulence in inhomogeneous plasmas is developed. Statistical nonlinear interactions between fluctuations are kept in the analysis as the renormalized drag, statistical noise and the averaged drive. The nonlinear interplay through them induces a quenching or suppressing effect, even if all the modes are unstable when they are analyzed independently. Variety in mode appearance takes place: one mode quenches the other two modes, or one mode is quenched by the other two modes, etc. The bifurcation of turbulence is analyzed and a phase diagram is drawn. Phase diagrams with cusp type catastrophe and butterfly type catastrophe are obtained. The subcritical bifurcation is possible to occur through the nonlinear interplay, even though each one is supercritical turbulence when analyzed independently. Analysis reveals that the nonlinear stability boundary (marginal point) and the amplitude of each mode may substantially shift from the conventional results of independent analyses. (author)

  19. The coupling of thermochemistry and phase diagrams for group III-V semiconductor systems. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, T.J.

    1998-07-21

    The project was directed at linking the thermochemical properties of III-V compound semiconductors systems with the reported phase diagrams. The solid-liquid phase equilibrium problem was formulated and three approaches to calculating the reduced standard state chemical potential were identified and values were calculated. In addition, thermochemical values for critical properties were measured using solid state electrochemical techniques. These values, along with the standard state chemical potentials and other available thermochemical and phase diagram data, were combined with a critical assessment of selected III-V systems. This work was culminated with a comprehensive assessment of all the III-V binary systems. A novel aspect of the experimental part of this project was the demonstration of the use of a liquid encapsulate to measure component activities by a solid state emf technique in liquid III-V systems that exhibit high vapor pressures at the measurement temperature.

  20. Considerations Concerning Matrix Diagram Transformations Associated with Mathematical Model Study of a Three-phase Transformer

    Directory of Open Access Journals (Sweden)

    Mihaela Poienar

    2014-09-01

    Full Text Available The clock hour figure mathematical model of a threephase transformer can be expressed, in the most plain form, through a 3X3 square matrix, called code matrix. The lines position reflect the modification in the high voltage windings terminal and the columns position reflect the modification in the low voltage winding terminal. The main changes on the transformer winding terminal are: the circular permutation of connection between windings; terminal supply reversal; reverse direction for the phase winding wrapping; reversal the beginning with the end for a phase winding; the connection conversion from N in Z between phase winding or inverse. The analytical form of these changes actually affect the configuration of the mathematical model expressed through a transformations diagram proposed and analyzed in two ways: bipolar version and unipolar version (fanwise. In the end of the paper are presented about the practical exploitation of the transformations diagram.

  1. Preparation of meta-stable phases of barium titanate by Sol-hydrothermal method

    Directory of Open Access Journals (Sweden)

    Mahalakshmi Selvaraj

    2015-11-01

    Full Text Available Two low-cost chemical methods of sol–gel and the hydrothermal process have been strategically combined to fabricate barium titanate (BaTiO3 nanopowders. This method was tested for various synthesis temperatures (100 °C to 250 °C employing barium dichloride (BaCl2 and titanium tetrachloride (TiCl4 as precursors and sodium hydroxide (NaOH as mineralizer for synthesis of BaTiO3 nanopowders. The as-prepared BaTiO3 powders were investigated for structural characteristics using x-ray diffraction (XRD, scanning electron microscopy (SEM and transmission electron microscopy (TEM. The overall analysis indicates that the hydrothermal conditions create a gentle environment to promote the formation of crystalline phase directly from amorphous phase at the very low processing temperatures investigated. XRD analysis showed phase transitions from cubic - tetragonal - orthorhombic - rhombohedral with increasing synthesis temperature and calculated grain sizes were 34 – 38 nm (using the Scherrer formula. SEM and TEM analysis verified that the BaTiO3 nanopowders synthesized by this method were spherical in shape and about 114 - 170 nm in size. The particle distribution in both SEM and TEM shows that as the reaction temperature increases from 100 °C to 250 °C, the particles agglomerate. Selective area electron diffraction (SAED shows that the particles are crystalline in nature. The study shows that choosing suitable precursor and optimizing pressure and temperature; different meta-stable (ferroelectric phases of undoped BaTiO3 nanopowders can be stabilized by the sol-hydrothermal method.

  2. Study on mutual diffusion and phase diagram in the Ni-Ta system

    International Nuclear Information System (INIS)

    Pimenov, V.N.; Ugaste, Yu.Eh.; Akkushkarova, K.A.

    1977-01-01

    The mutual diffusion in the Ni-Ta system has been investigated with a view of refining the constitutional diagram. The mutual diffusion factors and their effective values in the various phases and the diffusion activation energies are calculated. Given are the dependences of the phase growth constants and the mutual diffusion factors upon the temperature. The existence of five new phases Ta 2 Ni, TaNi, TaNi 2 , TaNi 3 , TaNi 8 has been discovered in the range of temperatures between 1150 and 1300 deg C. It is established that all the phases have a small concentration range of existence. It is noted that the diffusion characteristics in the phases (mutual diffusion factor and activation energy) differ widely, but fail to correlate with their melting points

  3. Localization of metastable atom beams with optical standing waves: nanolithography at the heisenberg limit

    Science.gov (United States)

    Johnson; Thywissen; Dekker; Berggren; Chu; Younkin; Prentiss

    1998-06-05

    The spatially dependent de-excitation of a beam of metastable argon atoms, traveling through an optical standing wave, produced a periodic array of localized metastable atoms with position and momentum spreads approaching the limit stated by the Heisenberg uncertainty principle. Silicon and silicon dioxide substrates placed in the path of the atom beam were patterned by the metastable atoms. The de-excitation of metastable atoms upon collision with the surface promoted the deposition of a carbonaceous film from a vapor-phase hydrocarbon precursor. The resulting patterns were imaged both directly and after chemical etching. Thus, quantum-mechanical steady-state atom distributions can be used for sub-0.1-micrometer lithography.

  4. New mean-field calculations for the phase diagram of the Annni model

    International Nuclear Information System (INIS)

    Tome, T.; Salinas, S.R.A.

    1987-01-01

    A variational procedure, with the inclusion of some spin fluctuations, to go beyond the standard layer-by-layer mean-field calculations for the T-p phase diagram of the ANNNI model is used. The high temperature region is studied analytically. The transition lines meet smoothly at the Lifshitz point, which is an inflection point of the second-order paramagnetic border. At low temperature, these numerical resuls confirm the stability of the main commensurate phases and show a quantitative trend towards the preductions f the Monte Carlo analyses. (author) [pt

  5. Multicritical dynamical phase diagrams of the kinetic Blume-Emery-Griffiths model with repulsive biquadratic coupling in an oscillating field

    Energy Technology Data Exchange (ETDEWEB)

    Temizer, Umuet [Department of Physics, Bozok University, 66100 Yozgat (Turkey); Kantar, Ersin [Institute of Science, Erciyes University, 38039 Kayseri (Turkey); Keskin, Mustafa [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)], E-mail: keskin@erciyes.edu.tr; Canko, Osman [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2008-06-15

    We study, within a mean-field approach, the stationary states of the kinetic Blume-Emery-Griffiths model with repulsive biquadratic coupling under the presence of a time-varying (sinusoidal) magnetic field. We employ the Glauber-type stochastic dynamics to construct set of dynamic equations of motion. The behavior of the time dependence of the order parameters and the behavior of the average order parameters in a period, which is also called the dynamic order parameters, as functions of the reduced temperature are investigated. The dynamic phase transition points are calculated and phase diagrams are presented in the reduced magnetic field amplitude and reduced temperature plane. The dynamical transition from one regime to the other can be of first- or second order depending on the region in the phase diagram. According to the values of the crystal field interaction or single-ion anisotropy constant and biquadratic exchange constant, we find 20 fundamental types of phase diagrams which exhibit many dynamic critical points, such as tricritical points, zero-temperature critical points, double critical end points, critical end point, triple point and multicritical point. Moreover, besides a disordered and ordered phases, seven coexistence phase regions exist in the system.

  6. The pressure-temperature phase diagram of pressure induced organic superconductors β-(BDA-TTP){2}MCl{4} (M = Ga, Fe)

    Science.gov (United States)

    Choi, E. S.; Graf, D.; Brooks, J. S.; Yamada, J.; Tokumoto, M.

    2004-04-01

    We investigate the pressure-temperature phase diagram of β -(BDA-TTP){2}MCl{4} (M=Ga, Fe), which shows a metal-insulator (MI) transition around 120 K at ambient pressure. By applying pressure, the insulating phase is suppressed. When the pressure is higher than 5.5 kbar, the superconducting phase appears in both salts with Tc ˜ 3 K for M=Ga and 2.2 K for M=Fe. We also observed Shubnikov-de Haas (SdH) oscillations at high magnetic field in both salts, where the SdH frequencies are found to be very similar each other. Key words. organic superconductor, pressure, phase diagram.

  7. Evaluating the Liquid Liquid Phase Transition Hypothesis of Supercoooled Water

    Science.gov (United States)

    Limmer, David; Chandler, David

    2011-03-01

    To explain the anomalous behavior of supercooled water it has been conjectured that buried within an experimentally inaccessible region of liquid water's phase diagram there exists a second critical point, which is the terminus of a first order transition line between two distinct liquid phases. The so-called liquid-liquid phase transition (LLPT) has since generated much study, though to date there is no consensus on its existence. In this talk, we will discuss our efforts to systematically study the metastable phase diagram of supercooled water through computer simulation. By employing importance-sampling techniques, we have calculated free energies as a function of the density and long-range order to determine unambiguously if two distinct liquid phases exist. We will argue that, contrary to the LLPT hypothesis, the observed phenomenology can be understood as a consequence of the limit of stability of the liquid far away from coexistence. Our results suggest that homogeneous nucleation is the cause of the increased fluctuations present upon supercooling. Further we will show how this understanding can be extended to explain experimental observations of hysteresis in confined supercooled water systems.

  8. Low-frequency phase diagram of irradiated graphene and a periodically driven spin-1/2 X Y chain

    Science.gov (United States)

    Mukherjee, Bhaskar; Mohan, Priyanka; Sen, Diptiman; Sengupta, K.

    2018-05-01

    We study the Floquet phase diagram of two-dimensional Dirac materials such as graphene and the one-dimensional (1D) spin-1/2 X Y model in a transverse field in the presence of periodic time-varying terms in their Hamiltonians in the low drive frequency (ω ) regime where standard 1 /ω perturbative expansions fail. For graphene, such periodic time-dependent terms are generated via the application of external radiation of amplitude A0 and time period T =2 π /ω , while for the 1D X Y model, they result from a two-rate drive protocol with a time-dependent magnetic field and nearest-neighbor couplings between the spins. Using the adiabatic-impulse method, whose predictions agree almost exactly with the corresponding numerical results in the low-frequency regime, we provide several semianalytic criteria for the occurrence of changes in the topology of the phase bands (eigenstates of the evolution operator U ) of such systems. For irradiated graphene, we point out the role of the symmetries of the instantaneous Hamiltonian H (t ) and the evolution operator U behind such topology changes. Our analysis reveals that at low frequencies, topology changes of irradiated graphene phase bands may also happen at t =T /3 and2 T /3 (apart from t =T ) showing the necessity of analyzing the phase bands of the system for obtaining its phase diagrams. We chart out the phase diagrams at t =T /3 ,2 T /3 ,and T , where such topology changes occur, as a function of A0 and T using exact numerics, and compare them with the prediction of the adiabatic-impulse method. We show that several characteristics of these phase diagrams can be analytically understood from results obtained using the adiabatic-impulse method and point out the crucial contribution of the high-symmetry points in the graphene Brillouin zone to these diagrams. We study the modes that can appear at the edges of a finite-width strip of graphene and show that the change in the number of such modes agrees with the change in the

  9. Dynamic phase transition and multicritical dynamic phase diagrams of the kinetic spin-3/2 Blume Emery Griffiths model with repulsive biquadratic coupling under a time-dependent oscillating external field

    Science.gov (United States)

    Deviren, Bayram; Keskin, Mustafa; Canko, Osman

    2008-03-01

    We extend our recent paper [O. Canko, B. Deviren, M. Keskin, J. Phys.: Condens. Mater 118 (2006) 6635] to present a study, within a mean-field approach, the stationary states of the kinetic spin-3/2 Blume-Emery-Griffiths model with repulsive biquadratic interaction under the presence of a time varying (sinusoidal) magnetic field. We found that the dynamic phase diagrams of the present work exhibit more complex, richer and more topological different types of phase diagrams than our recent paper. Especially, the obtained dynamic phase diagrams show the ferrimagnetic ( i) phase in addition to the ferromagnetic ±3/2 ( f), ferromagnetic ±1/2 ( f), antiquadrupolar or staggered ( a) and disordered ( d) phases, and the f+i, f+d, i+d, f+i+d, a+d and/or f+i+a coexistence regions in addition to the f+f, f+d, f+a, f+d and/or f+a+d coexistence regions, depending on interaction parameters. Moreover, the phase diagrams exhibit dynamic zero-temperature critical, critical end, double critical end, multicritical, and/or pentacritical special points in addition to the dynamic tricritical, double critical end point, triple, quadruple and/or tetracritical special points that depending on the interaction parameters.

  10. Hydrogen in niobium, tantalum, and vanadium: Structures, phase diagrams, and morphologies

    International Nuclear Information System (INIS)

    Schober, T.

    1978-07-01

    The paper discusses basic aspects of the reactions between the metals niobium, tantalum, vanadium, and hydrogen or deuterium. After an introduction to problems of preparation experimental technqiues for the investigation of hydrides are presented. The possible hydride structures are discussed. With vanadium, there are great differences between the structures of hydrides and deuterides. Detailed mention is also made of recent measurements of the NGH, TaH, VH, and VD phase diagrams. (orig./WBU) [de

  11. Phase diagrams of a nonequilibrium mixed spin-1/2 and spin-2 Ising ferrimagnetic system under a time-dependent oscillating magnetic field

    International Nuclear Information System (INIS)

    Keskin, M.; Canko, O.; Gueldal, S.

    2009-01-01

    We present phase diagrams for a nonequilibrium mixed spin-1/2 and spin-2 Ising ferrimagnetic system on a square lattice in the presence of a time dependent oscillating external magnetic field. We employ the Glauber transition rates to construct the mean-field dynamical equations. The time variation of the average magnetizations and the thermal behavior of the dynamic magnetizations are investigated, extensively. The nature (continuous or discontinuous) of the transitions is characterized by studying the thermal behaviors of the dynamic magnetizations. The dynamic phase transition points are obtained and the phase diagrams are presented in two different planes. Phase diagrams contain paramagnetic (p) and ferrimagnetic (i) phases, and one coexistence or mixed phase region, namely the i+p, that strongly depend on interaction parameters. The system exhibits the dynamic tricritical point and the reentrant behaviors.

  12. Phase diagrams of a nonequilibrium mixed spin-1/2 and spin-2 Ising ferrimagnetic system under a time-dependent oscillating magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Keskin, M., E-mail: keskin@erciyes.edu.t [Department of Physics, Erciyes University, 38039 Kayseri (Turkey); Canko, O. [Department of Physics, Erciyes University, 38039 Kayseri (Turkey); Gueldal, S. [Institute of Science, Erciyes University, 38039 Kayseri (Turkey)

    2009-12-14

    We present phase diagrams for a nonequilibrium mixed spin-1/2 and spin-2 Ising ferrimagnetic system on a square lattice in the presence of a time dependent oscillating external magnetic field. We employ the Glauber transition rates to construct the mean-field dynamical equations. The time variation of the average magnetizations and the thermal behavior of the dynamic magnetizations are investigated, extensively. The nature (continuous or discontinuous) of the transitions is characterized by studying the thermal behaviors of the dynamic magnetizations. The dynamic phase transition points are obtained and the phase diagrams are presented in two different planes. Phase diagrams contain paramagnetic (p) and ferrimagnetic (i) phases, and one coexistence or mixed phase region, namely the i+p, that strongly depend on interaction parameters. The system exhibits the dynamic tricritical point and the reentrant behaviors.

  13. Vortex phase diagram and vortex dynamics at low temperature in a thick a-MgxB1-x film

    International Nuclear Information System (INIS)

    Okuma, S.; Kohara, M.

    2007-01-01

    We report on the equilibrium vortex phase diagram and vortex dynamics at low temperature T in a thick amorphous (a-)Mg x B 1-x film based on the measurements of the dc resistivity ρ and time (t)-dependent component of the flux-flow voltage, δV(t), respectively. Both ρ(T) in perpendicular fields and the vortex phase diagram are qualitatively similar to those for the a-Mo x Si 1-x films, in which evidence for the quantum-vortex-liquid (QVL) phase has been obtained. In either material system we observe anomalous vortex flow with the asymmetric distribution of δV(t) in the QVL phase, suggesting that the anomalous flow is a universal phenomenon commonly observed for disordered amorphous films, independent of material

  14. Topological Phase Diagrams of Bulk and Monolayer TiS2−xTex

    KAUST Repository

    Zhu, Zhiyong

    2013-02-12

    With the use of ab initio calculations, the topological phase diagrams of bulk and monolayer TiS2−xTex are established. Whereas bulk TiS2−xTex shows two strong topological phases [1;(000)] and [1;(001)] for 0.44phases in three and two dimensions simultaneously.

  15. Topological Phase Diagrams of Bulk and Monolayer TiS2−xTex

    KAUST Repository

    Zhu, Zhiyong; Cheng, Yingchun; Schwingenschlö gl, Udo

    2013-01-01

    With the use of ab initio calculations, the topological phase diagrams of bulk and monolayer TiS2−xTex are established. Whereas bulk TiS2−xTex shows two strong topological phases [1;(000)] and [1;(001)] for 0.44phases in three and two dimensions simultaneously.

  16. A re-examination of thermodynamic modelling of U-Ru binary phase diagram

    Energy Technology Data Exchange (ETDEWEB)

    Wang, L.C.; Kaye, M.H., E-mail: matthew.kaye@uoit.ca [University of Ontario Institute of Technology, Oshawa, ON (Canada)

    2015-07-01

    Ruthenium (Ru) is one of the more abundant fission products (FPs) both in fast breeder reactors and thermal reactors. Post irradiation examinations (PIE) show that both 'the white metallic phase' (MoTc-Ru-Rh-Pd) and 'the other metallic phase' (U(Pd-Rh-Ru)3) are present in spent nuclear fuels. To describe this quaternary system, binary subsystems of uranium (U) with Pd, Rh, and Ru are necessary. Presently, only the U-Ru system has been thermodynamically described but with some problems. As part of research on U-Ru-Rh-Pd quaternary system, an improved consistent thermodynamic model describing the U-Ru binary phase diagram has been obtained. (author)

  17. A partial isothermal section at 1000 ˚C of Al-Mn-Fe phase diagram in vicinity of Taylor phase and decagonal quasicrystal

    Czech Academy of Sciences Publication Activity Database

    Priputen, P.; Černíčková, I.; Lejček, Pavel; Janičkovič, D.; Janovec, J.

    2016-01-01

    Roč. 37, č. 2 (2016), 130-134 ISSN 1547-7037 R&D Projects: GA ČR GBP108/12/G043 Institutional support: RVO:68378271 Keywords : aluminium alloys * equilibria * experimental phase * intermetallics * isothermal section * phase diagram Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.938, year: 2016

  18. On the superconducting phase diagram of high Tc superconductors

    International Nuclear Information System (INIS)

    de la Cruz, F.

    1990-01-01

    The tendency of oxide superconductors to show granularity has been pointed out since the beginning of research on superconductivity in this type of materials. Nevertheless, only very recently the full phase diagram and characteristics of the grains have been determined. In this paper, the authors review and discuss the different critical fields and their relation to the transport of superconducting current. The superconducting response of single crystals of High Tc superconductors is discussed. Special attention is devoted to the behavior of the vortex lattice and, in particular, to the recent discovery of the quenching of H c1 in YBaCuO, several degrees below Tc

  19. Defect phase diagram for doping of Ga2O3

    OpenAIRE

    Stephan Lany

    2018-01-01

    For the case of n-type doping of β-Ga2O3 by group 14 dopants (C, Si, Ge, Sn), a defect phase diagram is constructed from defect equilibria calculated over a range of temperatures (T), O partial pressures (pO2), and dopant concentrations. The underlying defect levels and formation energies are determined from first-principles supercell calculations with GW bandgap corrections. Only Si is found to be a truly shallow donor, C is a deep DX-like (lattice relaxed donor) center, and Ge and Sn have d...

  20. Numerical insights into the phase diagram of p-atic membranes with spherical topology

    DEFF Research Database (Denmark)

    Hansen, Allan Grønhøj; Ramakrishnan, N.; Sunil Kumar, P. B.

    2017-01-01

    Abstract.: The properties of self-avoiding p-atic membranes restricted to spherical topology have been studied by Monte Carlo simulations of a triangulated random surface model. Spherically shaped p-atic membranes undergo a Kosterlitz-Thouless transition as expected with topology induced mutually...... of disclinations. We confirm the proposed buckling of disclinations in the p-atic ordered phase, while the expected associated disordering (crumpling) transition at low bending rigidities is absent in the phase diagram. Graphical abstract: [Figure not available: see fulltext.]...

  1. Phase Diagrams of Some Sodium and Potassium Salts In Light and Heavy Water

    Energy Technology Data Exchange (ETDEWEB)

    Holmberg, K E

    1968-12-15

    Phase diagrams for fluorides, chlorides, bromides, iodides, nitrates, sulphates and carbonates of sodium and potassium with D{sub 2}O and H{sub 2}O have been determined in the range from eutectic temperature to 60 deg C. Generally the relative solubility is less in D{sub 2}O, but there are some exceptions in cases of a hydrate as the solid phase. The freezing point depression for freezing of ice is often somewhat smaller in the case of D{sub 2}O.

  2. Assessment of the thermodynamic properties and phase diagram of the Bi-Pd system

    Czech Academy of Sciences Publication Activity Database

    Vřešťál, Jan; Pinkas, J.; Watson, A.; Scott, A.; Houserová, Jana; Kroupa, Aleš

    2006-01-01

    Roč. 30, č. 1 (2006), s. 14-17 ISSN 0364-5916 R&D Projects: GA MŠk OC 531.001; GA MŠk OC 531.002 Institutional research plan: CEZ:AV0Z20410507 Keywords : phase diagram * ab initio calculations * calorimetry Subject RIV: BJ - Thermodynamics Impact factor: 1.432, year: 2006

  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 organic crystal paracetamol

    International Nuclear Information System (INIS)

    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. (paper)

  5. Phase diagram of dense two-color QCD within lattice simulations

    Directory of Open Access Journals (Sweden)

    Braguta V.V.

    2017-01-01

    Full Text Available We present the results of a low-temperature scan of the phase diagram of dense two-color QCD with Nf = 2 quarks. The study is conducted using lattice simulation with rooted staggered quarks. At small chemical potential we observe the hadronic phase, where the theory is in a confining state, chiral symmetry is broken, the baryon density is zero and there is no diquark condensate. At the critical point μ = mπ/2 we observe the expected second order transition to Bose-Einstein condensation of scalar diquarks. In this phase the system is still in confinement in conjunction with nonzero baryon density, but the chiral symmetry is restored in the chiral limit. We have also found that in the first two phases the system is well described by chiral perturbation theory. For larger values of the chemical potential the system turns into another phase, where the relevant degrees of freedom are fermions residing inside the Fermi sphere, and the diquark condensation takes place on the Fermi surface. In this phase the system is still in confinement, chiral symmetry is restored and the system is very similar to the quarkyonic state predicted by SU(Nc theory at large Nc.

  6. Studies on the phase diagram of LiBr-SrBr2 system

    International Nuclear Information System (INIS)

    Mahendran, K.H.; Sujatha, K.; Sridharan, R.; Gnanasekaran, T.

    2003-01-01

    Binary LiBr-SrBr 2 system was investigated using differential scanning calorimetry (DSC) and the equilibrium phases at different compositions were identified using X-ray diffraction (XRD). This system has a compound LiSr 2 Br 5 , and exhibits a eutectic reaction between this compound and LiBr at 434 deg. C and the eutectic has a composition of 35 mol% SrBr 2 . The compound LiSr 2 Br 5 undergoes peritectic decomposition at 484 deg. C. From the DSC and XRD results, phase diagram of the LiBr-SrBr 2 system is constructed

  7. Collisional interaction between metastable neon atoms

    International Nuclear Information System (INIS)

    Drunen, Wouter Johannes van

    2008-01-01

    In this thesis, the study of cold gases of neon atoms in different metastable states is described. It contains measurements of the collisional parameters for both the 3s[3/2] 2 and the 3s'[1/2] 0 metastable state and the dependence of the inelastic loss on external fields. Furthermore, the investigation of frequency dependent laser-induced collisions, and the possibility to excite photoassociation resonances is presented. For the measurements described here, neon atoms have been confined in a magnetooptical trap, in a magnetostatic trap, or in an optical dipole trap, respectively. By laser cooling inside the magnetic trap, atomic samples with more than 95 percent occupation of the magnetic substate m J = +2 could be prepared. They have a typical temperature of 0.5 mK, central densities up to 10 11 cm -3 , and a central phase-space density of up to 2.2.10 -7 . After loading the optical dipole trap from the magnetic trap, 2.5.10 6 atoms with typical temperatures of 0.1 mK, and central densities up to 5.10 10 cm -3 were trapped. By evaporative cooling of the atoms in the magnetic trap we could increase the phase-space density by a factor of 200 to 5.10 -5 . Investigating the frequency dependence of laser-induced collisions did not reveal an experimental signature for the excitation of photoassociation resonances. For the 3 D 3 line a frequency dependence of laser enhanced Penning ionization was observed. Measurement of the two-body loss coefficient as function of the magnetic field showed a field dependence of the inelastic loss. These losses increase towards both small and large offset fields. The implementation of an optical dipole trap allowed us to trap the 3 P 0 metastable state. From the trap loss measurements we determined the two-body loss coefficient of the 3 P 0 metastable state for both bosonic isotopes 20 Ne and 22 Ne. For 20 Ne we obtained β=6 +5 -4 .10 -10 cm 3 /s and for 22 Ne β = 11 +7 -6 .10 -10 cm 3 /s. (orig.)

  8. Thermodynamic modeling of the CeO{sub 2}–CoO nano-phase diagram

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sung S., E-mail: sungkim@wow.hongik.ac.kr

    2014-03-05

    Highlights: • The CeO{sub 2}–CoO nano-phase diagram was modeled thermodynamically. • The surface energies of the solution phases were modeled with Butler’s equation. • The present work agreed with the experimental work on the nanoparticle sintering. -- Abstract: A nano-phase diagram of the CeO{sub 2}–CoO system was modeled thermodynamically with experimental data available in the literatures. The surface energies of CeO{sub 2} and CoO unavailable in the literatures were estimated reasonably on the thermodynamic basis. Butler’s model was used to describe the surface energy and the surface composition of the solution phases and then the nano interaction parameters on the particle radius were assessed through the multiple linear regression method. A consistent set of optimized interaction parameters in the present system was derived for describing the Gibbs energy of liquid, fluorite, and halite solution phases as a function of particle radius. The eutectic temperatures calculated in the present work interpreted well the experimental data for the unusual low sintering temperature of the nanoparticles with the tri-modal particle size distribution. Furthermore, with the aid of the present result, the microstructure evolution in the CGO–CoO system during the nanoparticle sintering was described reasonably. It is concluded that the present modeling will be a good guide for the condition of the liquid phase sintering to obtain the rapid densification of the nanoparticles at lower temperatures.

  9. Dynamic phase diagrams of the Ising metamagnet in an oscillating magnetic field within the effective-field theory

    Energy Technology Data Exchange (ETDEWEB)

    Deviren, Bayram [Department of Physics, Nevsehir University, 50300 Nevsehir (Turkey); Institute of Science, Erciyes University, 38039 Kayseri (Turkey); Keskin, Mustafa, E-mail: keskin@erciyes.edu.t [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2010-07-12

    Dynamic aspects of a two-sublattice Ising metamagnet on honeycomb, square and hexagonal lattices under the presence of a time-dependent oscillating external magnetic field are studied by using the effective-field theory with correlations. The set of effective-field dynamic equations is derived by employing Glauber transition rates. The phases in the system are obtained by solving these dynamic equations. The thermal behavior of the dynamic staggered magnetization, the hysteresis loop area and correlation are investigated in order to characterize the nature of the dynamic transitions and to obtain dynamic phase transition temperatures. The phase diagrams are constructed in two different planes, and exhibit dynamic tricritical behavior, which strongly depends on interaction parameters. In order to investigate the spin correlation effect on the dynamic phase diagrams of the system, the results are also given within the framework of the dynamic mean-field approximation.

  10. Dynamic phase diagrams of the Ising metamagnet in an oscillating magnetic field within the effective-field theory

    International Nuclear Information System (INIS)

    Deviren, Bayram; Keskin, Mustafa

    2010-01-01

    Dynamic aspects of a two-sublattice Ising metamagnet on honeycomb, square and hexagonal lattices under the presence of a time-dependent oscillating external magnetic field are studied by using the effective-field theory with correlations. The set of effective-field dynamic equations is derived by employing Glauber transition rates. The phases in the system are obtained by solving these dynamic equations. The thermal behavior of the dynamic staggered magnetization, the hysteresis loop area and correlation are investigated in order to characterize the nature of the dynamic transitions and to obtain dynamic phase transition temperatures. The phase diagrams are constructed in two different planes, and exhibit dynamic tricritical behavior, which strongly depends on interaction parameters. In order to investigate the spin correlation effect on the dynamic phase diagrams of the system, the results are also given within the framework of the dynamic mean-field approximation.

  11. Phase Transformation of Metastable Austenite in Steel during Nano indentation

    International Nuclear Information System (INIS)

    Ahn, Taehong; Lee, Sung Bo; Han, Heung Nam; Park, Kyungtae

    2013-01-01

    These can produce geometrical softening accompanied by a sudden displacement excursion during load-controlled nanoindentation, which referred to in the literature as a pop-in. In this study, phase transformation of metastable austenite to stress-induced ε martensite which causes pop-ins during nanoindentation of steel will be reported and discussed. This study investigated the relationship between pop-in behavior of austenite in the early stage of nanoindentation and formation of ε martensite based on microstructural analyses. The load-displacement curve obtained from nanoindentation revealed stepwise pop-ins in the early stage of plastic deformation. From analyses of high resolution TEM images, a cluster of banded structure under the indent turned out a juxtaposition of (111) planes of γ austenite and (0001) planes of ε martensite. The calculation of displacement along indentation axis for (111) slip system by formation of ε martensite showed that geometrical softening can also occur by ε martensite formation when considering that the stress-induced ε martensite transformation is the predominant deformation mode in the early stage of plastic deformation and its monopartial nature as well. These microstructural investigations strongly suggest that the pop-in behavior in the early stage of plastic deformation of austenite is closely related to the formation of ε martensite

  12. Phase Transformation of Metastable Austenite in Steel during Nano indentation

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, Taehong [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Lee, Sung Bo; Han, Heung Nam [Seoul National Univ., Seoul (Korea, Republic of); Park, Kyungtae [Hanbat National Univ., Daejeon (Korea, Republic of)

    2013-05-15

    These can produce geometrical softening accompanied by a sudden displacement excursion during load-controlled nanoindentation, which referred to in the literature as a pop-in. In this study, phase transformation of metastable austenite to stress-induced ε martensite which causes pop-ins during nanoindentation of steel will be reported and discussed. This study investigated the relationship between pop-in behavior of austenite in the early stage of nanoindentation and formation of ε martensite based on microstructural analyses. The load-displacement curve obtained from nanoindentation revealed stepwise pop-ins in the early stage of plastic deformation. From analyses of high resolution TEM images, a cluster of banded structure under the indent turned out a juxtaposition of (111) planes of γ austenite and (0001) planes of ε martensite. The calculation of displacement along indentation axis for (111) slip system by formation of ε martensite showed that geometrical softening can also occur by ε martensite formation when considering that the stress-induced ε martensite transformation is the predominant deformation mode in the early stage of plastic deformation and its monopartial nature as well. These microstructural investigations strongly suggest that the pop-in behavior in the early stage of plastic deformation of austenite is closely related to the formation of ε martensite.

  13. On the solid–liquid phase diagrams of binary mixtures of even saturated fatty alcohols: Systems exhibiting peritectic reaction

    Energy Technology Data Exchange (ETDEWEB)

    Carareto, Natália D.D. [EXTRAE, Department of Food Engineering, Food Engineering Faculty, University of Campinas, UNICAMP, CEP 13083-862 Campinas, SP (Brazil); Santos, Adenílson O. dos [Social Sciences, Health and Technology Center, University of Maranhão, UFMA, CEP 65900-410 Imperatriz, MA (Brazil); Rolemberg, Marlus P. [Institute of Science and Technology, University of Alfenas, UNIFAL, Rodovia José AurélioVilela, CEP 37715400 Poços de Caldas, MG (Brazil); Cardoso, Lisandro P. [Institute of Physics GlebWataghin, University of Campinas, UNICAMP, C.P. 6165, CEP 13083-970 Campinas, SP (Brazil); Costa, Mariana C. [School of Applied Science, University of Campinas, UNICAMP, CEP 13484-350 Limeira, SP (Brazil); Meirelles, Antonio J.A., E-mail: tomze@fea.unicamp.br [EXTRAE, Department of Food Engineering, Food Engineering Faculty, University of Campinas, UNICAMP, CEP 13083-862 Campinas, SP (Brazil)

    2014-08-10

    Highlights: • SLE of binary mixtures of saturated fatty alcohols was studied. • Experimental data were obtained using DSC and stepscan DSC. • Microscopy and X-ray diffraction used as complementary techniques. • Systems presented eutectic, peritectic and metatectic points. - Abstract: The solid–liquid phase diagrams of the following binary mixtures of even saturated fatty alcohols are reported in the literature for the first time: 1-octanol (C8OH) + 1-decanol (C10OH), 1-decanol + 1-dodecanol (C12OH), 1-dodecanol + 1-hexadecanol (C16OH) and 1-tetradecanol (C14OH) + 1-octadecanol (C18OH). The phase diagrams were obtained by differential scanning calorimetry (DSC) using a linear heating rate of 1 K min{sup −1} and further investigated by using a stepscan DSC method. X-ray diffraction (XRD) and polarized light microscopy were also used to complement the characterization of the phase diagrams which have shown a complex global behavior, presenting not only peritectic and eutectic reactions, but also the metatectic reaction and partial immiscibility on solid state.

  14. On the solid–liquid phase diagrams of binary mixtures of even saturated fatty alcohols: Systems exhibiting peritectic reaction

    International Nuclear Information System (INIS)

    Carareto, Natália D.D.; Santos, Adenílson O. dos; Rolemberg, Marlus P.; Cardoso, Lisandro P.; Costa, Mariana C.; Meirelles, Antonio J.A.

    2014-01-01

    Highlights: • SLE of binary mixtures of saturated fatty alcohols was studied. • Experimental data were obtained using DSC and stepscan DSC. • Microscopy and X-ray diffraction used as complementary techniques. • Systems presented eutectic, peritectic and metatectic points. - Abstract: The solid–liquid phase diagrams of the following binary mixtures of even saturated fatty alcohols are reported in the literature for the first time: 1-octanol (C8OH) + 1-decanol (C10OH), 1-decanol + 1-dodecanol (C12OH), 1-dodecanol + 1-hexadecanol (C16OH) and 1-tetradecanol (C14OH) + 1-octadecanol (C18OH). The phase diagrams were obtained by differential scanning calorimetry (DSC) using a linear heating rate of 1 K min −1 and further investigated by using a stepscan DSC method. X-ray diffraction (XRD) and polarized light microscopy were also used to complement the characterization of the phase diagrams which have shown a complex global behavior, presenting not only peritectic and eutectic reactions, but also the metatectic reaction and partial immiscibility on solid state

  15. Phase diagram of a polarized Fermi gas across a Feshbach resonance in a potential trap

    International Nuclear Information System (INIS)

    Yi, W.; Duan, L.-M.

    2006-01-01

    We map out the detailed phase diagram of a trapped ultracold Fermi gas with population imbalance across a wide Feshbach resonance. We show that under the local density approximation, the properties of the atoms in any (anisotropic) harmonic traps are universally characterized by three dimensionless parameters: the normalized temperature, the dimensionless interaction strength, and the population imbalance. We then discuss the possible quantum phases in the trap, and quantitatively characterize their phase boundaries in various typical parameter regions

  16. Hydrothermal synthesis and characterization of a two-dimensional piperazinium cobalt–zinc phosphate via a metastable one-dimensional phase

    International Nuclear Information System (INIS)

    Torre-Fernández, Laura; Khainakova, Olena A.; Espina, Aránzazu; Amghouz, Zakariae; Khainakov, Sergei A.; Alfonso, Belén F.; Blanco, Jesús A.; García, José R.; García-Granda, Santiago

    2015-01-01

    A two-dimensional piperazinium cobalt–zinc phosphate, formulated as (C 4 N 2 H 12 ) 1.5 (Co 0.6 Zn 0.4 ) 2 (HPO 4 ) 2 (PO 4 )·H 2 O (2D), was synthesized under hydrothermal conditions. The crystal structure was determined using single-crystal X-ray diffraction data (monoclinic P2 1 /c, a=8.1165(3) Å, b=26.2301(10) Å, c=8.3595(4) Å, and β=110.930(5)°) and the hydrogen atom positions were optimized by DFT calculations. A single-crystal corresponding to one-dimensional metastable phase, (C 4 N 2 H 12 )Co 0.3 Zn 0.7 (HPO 4 ) 2 ·H 2 O (1D), was also isolated and the crystal structure was determined (monoclinic P2 1 /c, a=8.9120(6) Å, b=14.0290(1) Å, c=12.2494(5) Å, and β=130.884(6)°). The bulk was characterized by chemical (C–H–N) analysis, powder X-ray diffraction (PXRD), powder X-ray thermodiffractometry (HT-XRD), transmission electron microscopy (STEM(DF)-EDX and EFTEM), and thermal analysis (TG/SDTA-MS), including activation energy data of its thermal decomposition. The magnetic susceptibility and magnetization measurements show no magnetic ordering down to 4 K. - Graphical abstract: Hydrothermal synthesis and structural characterization of a two-dimensional piperazinium cobalt–zinc phosphate, (C 4 N 2 H 12 ) 1.5 (Co 0.6 Zn 0.4 ) 2 (HPO 4 ) 2 (PO 4 )·H 2 O (2D), have been reported. The crystal structure of a one-dimensional piperazinium cobalt–zinc phosphate, (C 4 N 2 H 12 )Co 0.3 Zn 0.7 (HPO 4 ) 2 ·H 2 O (1D) a metastable phase during the hydrothermal synthesis, was also determined. The thermal behavior of 2D compound is strongly dependent on the selected heating rate and the magnetic susceptibility and magnetization measurements show no magnetic ordering down to 4 K. - Highlights: • A 2D piperazinium cobalt–zinc phosphate has been synthesized and characterized. • Crystal structure of 1D metastable phase was also determined. • Thermal behavior of 2D compound is strongly dependent on the selected heating rate. • Magnetic

  17. Analytical Determining Of The Steinmetz Equivalent Diagram Elements Of Single-Phase Transformer

    Directory of Open Access Journals (Sweden)

    T. Aly Saandy

    2015-08-01

    Full Text Available This article presents to an analytical calculation methodology of the Steinmetz Equivalent Diagram Elements applied to the prediction of Eddy current loss in a single-phase transformer. Based on the electrical circuit theory the active and reactive powers consumed by the core are expressed analytically in function of the electromagnetic parameters as resistivity permeability and the geometrical dimensions of the core. The proposed modeling approach is established with the duality parallel series. The equivalent diagram elements empirically determined by Steinmetz are analytically expressed using the expressions of the no loaded transformer consumptions. To verify the relevance of the model validations both by simulations with different powers and measurements were carried out to determine the resistance and reactance of the core. The obtained results are in good agreement with the theoretical approach and the practical results.

  18. Reduced temperature phase diagrams of the silver-rare earths binary systems

    International Nuclear Information System (INIS)

    Ferro, R.; Delfino, S.; Capelli, R.; Borsese, A.

    1975-01-01

    Phase equilibria of the silver-rare earth binary systems have been reported in ''reduced temperature'' diagrams (the ''reduced temperature'' being defined as the ratio between a characteristic temperature of the Agsub(x)R.E. phase and the melting temperature of the corresponding R.E. metal, both in 0 K). The smooth trends of the various characteristic reduced temperatures, when plotted against the R.E. atomic number, have been demonstrated. On passing from the light- to the heavy-rare-earths, a correlation has been found between the crossing of these curves and other phenomena, such as the disappearing of the Ag 5 R.E. phases from incongruently, to congruently melting compounds. The trends of the reduced-temperature curves have been briefly discussed in terms of the treatment suggested by Gschneidner together with the volumetric data known for the different Agsub(x)R.E. phases. In addition, the characteristic data of the 1:1 AgR.E. compounds have been compared with those of the analogous AuR.E. phases. (Auth.)

  19. Magnetic transition phase diagram of cobalt clusters electrodeposited on HOPG: Experimental and micromagnetic modelling study

    Energy Technology Data Exchange (ETDEWEB)

    Rivera, M., E-mail: mrivera@fisica.unam.m [Imperial College London, Department of Chemistry, South Kensington Campus, London SW7 2AZ (United Kingdom); Rios-Reyes, C.H. [Universidad Autonoma Metropolitana-Azcapotzalco, Departamento de Materiales, Av. San Pablo 180, Col. Reynosa Tamaulipas, C.P. 02200, Mexico D.F. (Mexico); Universidad Autonoma del Estado de Hidalgo, Centro de Investigaciones Quimicas, Mineral de la Reforma, Hidalgo, C.P. 42181 (Mexico); Mendoza-Huizar, L.H. [Universidad Autonoma del Estado de Hidalgo, Centro de Investigaciones Quimicas, Mineral de la Reforma, Hidalgo, C.P. 42181 (Mexico)

    2011-04-15

    The magnetic transition from mono- to multidomain magnetic states of cobalt clusters electrodeposited on highly oriented pyrolytic graphite electrodes was studied experimentally using Magnetic Force Microscopy. From these images, it was found that the critical size of the magnetic transition is dominated by the height rather than the diameter of the aggregate. This experimental behavior was found to be consistent with a theoretical single-domain ferromagnetic model that states that a critical height limits the monodomain state. By analyzing the clusters magnetic states as a function of their dimensions, magnetic exchange constant and anisotropy value were obtained and used to calculate other magnetic properties such as the exchange length, magnetic wall thickness, etc. Finally, a micromagnetic simulation study correctly predicted the experimental magnetic transition phase diagram. - Research highlights: > Electrodeposition of cobalt clusters. > Mono to multidomain magnetic transition. > Magnetic phase diagram.

  20. Magnetic transition phase diagram of cobalt clusters electrodeposited on HOPG: Experimental and micromagnetic modelling study

    International Nuclear Information System (INIS)

    Rivera, M.; Rios-Reyes, C.H.; Mendoza-Huizar, L.H.

    2011-01-01

    The magnetic transition from mono- to multidomain magnetic states of cobalt clusters electrodeposited on highly oriented pyrolytic graphite electrodes was studied experimentally using Magnetic Force Microscopy. From these images, it was found that the critical size of the magnetic transition is dominated by the height rather than the diameter of the aggregate. This experimental behavior was found to be consistent with a theoretical single-domain ferromagnetic model that states that a critical height limits the monodomain state. By analyzing the clusters magnetic states as a function of their dimensions, magnetic exchange constant and anisotropy value were obtained and used to calculate other magnetic properties such as the exchange length, magnetic wall thickness, etc. Finally, a micromagnetic simulation study correctly predicted the experimental magnetic transition phase diagram. - Research highlights: → Electrodeposition of cobalt clusters. →Mono to multidomain magnetic transition. → Magnetic phase diagram.

  1. T-p phase diagrams and the barocaloric effect in materials with successive phase transitions

    Science.gov (United States)

    Gorev, M. V.; Bogdanov, E. V.; Flerov, I. N.

    2017-09-01

    An analysis of the extensive and intensive barocaloric effect (BCE) at successive structural phase transitions in some complex fluorides and oxyfluorides was performed. The high sensitivity of these compounds to a change in the chemical pressure allows one to vary the succession and parameters of the transformations (temperature, entropy, baric coefficient) over a wide range and obtain optimal values of the BCE. A comparison of different types of schematic T-p phase diagrams with the complicated T( p) dependences observed experimentally shows that in some ranges of temperature and pressure the BCE in compounds undergoing successive transformations can be increased due to a summation of caloric effects associated with distinct phase transitions. The maximum values of the extensive and intensive BCE in complex fluorides and oxyfluorides can be realized at rather low pressure (0.1-0.3 GPa). In a narrow temperature range around the triple points conversion from conventional BCE to inverse BCE is observed, which is followed by a gigantic change of both \\vertΔ S_BCE\\vert and \\vertΔ T_AD\\vert .

  2. The equilibrium phase diagram of the magnesium-copper-yttrium system

    International Nuclear Information System (INIS)

    Mezbahul-Islam, Mohammad; Kevorkov, Dmytro; Medraj, Mamoun

    2008-01-01

    Thermodynamic modelling of the Mg-Cu-Y system is carried out as a part of thermodynamic database construction for Mg alloys. This system is being modelled for the first time using the modified quasichemical model which considers the presence of short range ordering in the liquid. A self-consistent thermodynamic database for the Mg-Cu-Y system was constructed by combining the thermodynamic descriptions of the constituent binaries, Mg-Cu, Cu-Y, and Mg-Y. All the three binaries have been re-optimized based on the experimental phase equilibrium and thermodynamic data available in the literature. The constructed database is used to calculate and predict thermodynamic properties, the binary phase diagrams and liquidus projections of the ternary Mg-Cu-Y system. The current calculation results are in good agreement with the experimental data reported in the literature

  3. Overview of the phase diagram of ionic magnetic colloidal dispersions

    International Nuclear Information System (INIS)

    Cousin, F.; Dubois, E.; Cabuil, V.; Boue, F.; Perzynski, R.

    2001-01-01

    We study ionic magnetic colloidal dispersions, which are constituted of γ-Fe 2 O 3 nanoparticles dispersed in water, and stabilized with electrostatic interparticle repulsion. The phase diagram PV versus Φ (P: osmotic pressure, V: particle volume, Φ: particle volume fraction) is explored, especially in the range of high Π and high Φ. The osmotic pressure P of the colloidal dispersion is known either by a measurement either because it is imposed during the sample preparation by osmotic compression. The structure of the colloidal dispersion is determined from Small Angle Neutron Scattering. Two regimes can be distinguished. At high pressure, fluid and solid phases can exist. Their structure is governed by strong electrostatic repulsion, the range of which is here evaluated. At low pressure, gas, liquid and glassy solids can exist. Their structure results from a sticky hard sphere potential. (author)

  4. Phase diagram of power law and Lennard-Jones systems: Crystal phases

    International Nuclear Information System (INIS)

    Travesset, Alex

    2014-01-01

    An extensive characterization of the low temperature phase diagram of particles interacting with power law or Lennard-Jones potentials is provided from Lattice Dynamical Theory. For power law systems, only two lattice structures are stable for certain values of the exponent (or softness) (A15, body centered cube (bcc)) and two more (face centered cubic (fcc), hexagonal close packed (hcp)) are always stable. Among them, only the fcc and bcc are equilibrium states. For Lennard-Jones systems, the equilibrium states are either hcp or fcc, with a coexistence curve in pressure and temperature that shows reentrant behavior. The hcp solid never coexists with the liquid. In all cases analyzed, for both power law and Lennard-Jones potentials, the fcc crystal has higher entropy than the hcp. The role of anharmonic terms is thoroughly analyzed and a general thermodynamic integration to account for them is proposed

  5. Wave packet dynamics, time scales and phase diagram in the IBM-Lipkin-Meshkov-Glick model

    Science.gov (United States)

    Castaños, Octavio; de los Santos, Francisco; Yáñez, Rafael; Romera, Elvira

    2018-02-01

    We derive the phase diagram of a scalar two-level boson model by studying the equilibrium and stability properties of its energy surface. The plane of control parameters is enlarged with respect to previous studies. We then analyze the time evolution of wave packets centered around the ground state at various quantum phase transition boundary lines. In particular, classical and revival times are computed numerically.

  6. Phase diagram of N = 2 superconformal field theories and bifurcation sets in catastrophe theory

    International Nuclear Information System (INIS)

    Kei Ito.

    1989-08-01

    Phase diagrams of N=2 superconformal field theories are mapped out. It is shown that they coincide with bifurcation sets in catastrophe theory. The results are applied to the determination of renormalization group flows triggered by a combination of two or more relevant operators. (author). 13 refs, 2 figs

  7. A partial phase diagram of Pt-rich Pt-Mn alloys

    CERN Document Server

    Sembiring, T; Ohshima, K I; Ota, K; Shishido, T

    2002-01-01

    We have performed the X-ray and electron diffraction studies to reconstruct a partial phase diagram of Pt-rich Pt-Mn alloys in the composition range of 10 to 35 at.% Mn. Electrical resistivity measurement was also used for determining the order-disorder transition temperature in Pt-14.2 at.% Mn alloy. The phase boundary between Cu sub 3 Au type and ABC sub 6 type ordered structures is established, in which the latter has been found recently by the present [J.Phys. Soc. Jpn. 71 (2002) 681]. In the ABC sub 6 type ordered phase, superlattice reflections both at 1/2 1/2 1/2 and its equivalent position (L-point) and at 100, 110 and their equivalent positions (X-point) appear in the composition range from 12.5 to 14.4 at.% Mn below 682degC. In the Cu sub 3 Au type ordered phase, diffuse maxima at L-point appear in the composition range from 15.9 to 19.7 at.% Mn in addition to the superlattice reflections at X-point. The Cu sub 3 Au type ordered structure is found to be stable in the composition range from 19.7 to 3...

  8. Supersymmetry breaking metastable vacua in runaway quiver gauge theories

    CERN Document Server

    Garcia-Etxebarria, Inaki; Uranga, Angel M

    2007-01-01

    In this paper we consider quiver gauge theories with fractional branes whose infrared dynamics removes the classical supersymmetric vacua (DSB branes). We show that addition of flavors to these theories (via additional non-compact branes) leads to local meta-stable supersymmetry breaking minima, closely related to those of SQCD with massive flavors. We simplify the study of the one-loop lifting of the accidental classical flat directions by direct computation of the pseudomoduli masses via Feynman diagrams. This new approach allows to obtain analytic results for all these theories. This work extends the results for the $dP_1$ theory in hep-th/0607218. The new approach allows to generalize the computation to general examples of DSB branes, and for arbitrary values of the superpotential couplings.

  9. Diagram of state of stiff amphiphilic macromolecules

    NARCIS (Netherlands)

    Markov, Vladimir A.; Vasilevskaya, Valentina V.; Khalatur, Pavel G.; ten Brinke, Gerrit; Khokhlov, Alexei R.

    2007-01-01

    We studied coil-globule transitions in stiff-chain amphiphilic macromolecules via computer modeling and constructed phase diagrams for such molecules in terms of solvent quality and persistence length. We showed that the shape of the phase diagram essentially depends on the macromolecule degree of

  10. Thermodynamic studies of mixtures for topical anesthesia: Lidocaine-salol binary phase diagram

    Energy Technology Data Exchange (ETDEWEB)

    Lazerges, Mathieu [Laboratoire de Chimie Physique (EA 4066), Faculte des Sciences Pharmaceutiques et Biologiques, Universite Paris Descartes, 4 Avenue de l' Observatoire, 75270 Paris Cedex 06 (France); Rietveld, Ivo B., E-mail: ivo.rietveld@parisdescartes.fr [Laboratoire de Chimie Physique (EA 4066), Faculte des Sciences Pharmaceutiques et Biologiques, Universite Paris Descartes, 4 Avenue de l' Observatoire, 75270 Paris Cedex 06 (France); Corvis, Yohann; Ceolin, Rene; Espeau, Philippe [Laboratoire de Chimie Physique (EA 4066), Faculte des Sciences Pharmaceutiques et Biologiques, Universite Paris Descartes, 4 Avenue de l' Observatoire, 75270 Paris Cedex 06 (France)

    2010-01-10

    The lidocaine-salol binary system has been investigated by differential scanning calorimetry, direct visual observations, and X-ray powder diffraction, resulting in a temperature-composition phase diagram with a eutectic equilibrium. The eutectic mixture, found at 0.423 {+-} 0.007 lidocaine mole-fraction, melts at 18.2 {+-} 0.5 {sup o}C with an enthalpy of 17.3 {+-} 0.5 kJ mol{sup -1}. This indicates that the liquid phase around the eutectic composition is stable at room temperature. Moreover, the undercooled liquid mixture does not easily crystallize. The present binary mixture exhibits eutectic behavior similar to the prilocaine-lidocaine mixture in the widely used EMLA topical anesthetic preparation.

  11. Thermodynamic studies of mixtures for topical anesthesia: Lidocaine-salol binary phase diagram

    International Nuclear Information System (INIS)

    Lazerges, Mathieu; Rietveld, Ivo B.; Corvis, Yohann; Ceolin, Rene; Espeau, Philippe

    2010-01-01

    The lidocaine-salol binary system has been investigated by differential scanning calorimetry, direct visual observations, and X-ray powder diffraction, resulting in a temperature-composition phase diagram with a eutectic equilibrium. The eutectic mixture, found at 0.423 ± 0.007 lidocaine mole-fraction, melts at 18.2 ± 0.5 o C with an enthalpy of 17.3 ± 0.5 kJ mol -1 . This indicates that the liquid phase around the eutectic composition is stable at room temperature. Moreover, the undercooled liquid mixture does not easily crystallize. The present binary mixture exhibits eutectic behavior similar to the prilocaine-lidocaine mixture in the widely used EMLA topical anesthetic preparation.

  12. Magnetic phase diagram of Ba3CoSb2O9 as determined by ultrasound velocity measurements

    Science.gov (United States)

    Quirion, G.; Lapointe-Major, M.; Poirier, M.; Quilliam, J. A.; Dun, Z. L.; Zhou, H. D.

    2015-07-01

    Using high-resolution sound velocity measurements we have obtained a very precise magnetic phase diagram of Ba3CoSb2O9 , a material that is considered to be an archetype of the spin-1/2 triangular-lattice antiferromagnet. Results obtained for the field parallel to the basal plane (up to 18 T) show three phase transitions, consistent with predictions based on simple two-dimensional isotropic Heisenberg models and previous experimental investigations. The phase diagram obtained for the field perpendicular to the basal plane clearly reveals an easy-plane character of this compound and, in particular, our measurements show a single first-order phase transition at Hc 1=12.0 T which can be attributed to a spin flop between an umbrella-type configuration and a coplanar V -type order where spins lie in a plane perpendicular to the a b plane. At low temperatures, softening of the lattice within some of the ordered phases is also observed and may be a result of residual spin fluctuations.

  13. Another dimension to metamorphic phase equilibria: the power of interactive movies for understanding complex phase diagram sections

    Science.gov (United States)

    Moulas, E.; Caddick, M. J.; Tisato, N.; Burg, J.-P.

    2012-04-01

    The investigation of metamorphic phase equilibria, using software packages that perform thermodynamic calculations, involves a series of important assumptions whose validity can often be questioned but are difficult to test. For example, potential influences of deformation on phase relations, and modification of effective reactant composition (X) at successive stages of equilibrium may both introduce significant uncertainty into phase diagram calculations. This is generally difficult to model with currently available techniques, and is typically not well quantified. We present here a method to investigate such phenomena along pre-defined Pressure-Temperature (P-T) paths, calculating local equilibrium via Gibbs energy minimization. An automated strategy to investigate complex changes in the effective equilibration composition has been developed. This demonstrates the consequences of specified X modification and, more importantly, permits automated calculation of X changes that are likely along the requested path if considering several specified processes. Here we describe calculations considering two such processes and show an additional example of a metamorphic texture that is difficult to model with current techniques. Firstly, we explore the assumption that although water saturation and bulk-rock equilibrium are generally considered to be valid assumptions in the calculation of phase equilibria, the saturation of thermodynamic components ignores mechanical effects that the fluid/melt phase can impose on the rock, which in turn can modify the effective equilibrium composition. Secondly, we examine how mass fractionation caused by porphyroblast growth at low temperatures or progressive melt extraction at high temperatures successively modifies X out of the plane of the initial diagram, complicating the process of determining best-fit P-T paths for natural samples. In particular, retrograde processes are poorly modeled without careful consideration of prograde

  14. Investigation on U - O - Na, Pu - O - Na and U,Pu - O - Na phase diagrams

    International Nuclear Information System (INIS)

    Pillon, S.

    1989-03-01

    The thermochemical interaction between the nuclear fuel (uranium and plutonium mixed oxides) and the sodium has been investigated and particularly the three phase diagrams: U - O - Na; Pu - O - Na; U,Pu - O - Na. High temperature neutron diffraction, microcalorimetry and powder X-ray diffraction were used for the characterization of the compounds synthetized. This study allowed to complete the knowledge about each of these diagrams and to measure some physical and thermal properties on the compounds. The limits on the modelization of the fuel-sodium interaction are discussed from the results of the UO 2 - Na reaction [fr

  15. Electrically induced metastability in SI-GaAs studied by positron lifetime spectroscopy

    International Nuclear Information System (INIS)

    Luo, Y.L.; Beling, C.D.; Fung, S.; Ling, C.C.; Lui, M.K.; Mui, W.K.

    2001-01-01

    Recently, a room temperature electrically induced metastability in semi-insulating (SI)-GaAs has been reported in which the normally high resistance state of SI-GaAs converts into a low resistance state when breakdown electric fields are applied to the metal/Si-GaAs/metal system. The low resistance state persists when the electric field is lowered below the breakdown bias and as such may thus be considered as metastable state of the material. To clarify whether the high field breakdown has its origins in some atomic configurational change induced through high energy electron collisions we have employed positron lifetime spectroscopy. Lifetime spectra that have been taken at the same bias in both the high current and low current phases show that the positron lifetime in the metastable state has no change within the experimental error from that of the normal state, thus suggesting that the metastability is most likely of purely electronic origin. (orig.)

  16. Modelling of phase diagrams and thermodynamic properties using Calphad method – Development of thermodynamic databases

    Czech Academy of Sciences Publication Activity Database

    Kroupa, Aleš

    2013-01-01

    Roč. 66, JAN (2013), s. 3-13 ISSN 0927-0256 R&D Projects: GA MŠk(CZ) OC08053 Institutional support: RVO:68081723 Keywords : Calphad method * phase diagram modelling * thermodynamic database development Subject RIV: BJ - Thermodynamics Impact factor: 1.879, year: 2013

  17. Thermodynamic Calculations of Ternary Polyalcohol and Amine Phase Diagrams for Thermal Energy Storage Materials

    Science.gov (United States)

    Shi, Renhai

    Organic polyalcohol and amine globular molecular crystal materials as phase change materials (PCMs) such as Pentaglycerine (PG-(CH3)C(CH 2OH)3), Tris(hydroxymethyl)aminomethane (TRIS-(NH2)C(CH 2OH)3), 2-amino-2methyl-1,3-propanediol (AMPL-(NH2)(CH3)C(CH2OH)2), and neopentylglycol (NPG-(CH3)2C(CH2OH) 2) can be considered to be potential candidates for thermal energy storage (TES) applications such as waste heat recovery, solar energy utilization, energy saving in buildings, and electronic device management during heating or cooling process in which the latent heat and sensible heat can be reversibly stored or released through solid state phase transitions over a range of temperatures. In order to understand the polymorphism of phase transition of these organic materials and provide more choice of materials design for TES, binary systems have been studied to lower the temperature of solid-state phase transition for the specific application. To our best knowledge, the study of ternary systems in these organic materials is limited. Based on this motivation, four ternary systems of PG-TRIS-AMPL, PG-TRIS-NPG, PG-AMPL-NPG, and TRIS-AMPL-NPG are proposed in this dissertation. Firstly, thermodynamic assessment with CALPHAD method is used to construct the Gibbs energy functions into thermodynamic database for these four materials based on available experimental results from X-Ray Diffraction (XRD) and Differential Scanning Calorimetry (DSC). The phase stability and thermodynamic characteristics of these four materials calculated from present thermodynamic database with CALPHAD method can match well the present experimental results from XRD and DSC. Secondly, related six binary phase diagrams of PG-TRIS, PG-AMPL, PG-NPG, TRIS-AMPL, TRIS-NPG, and AMPL-NPG are optimized with CALPHAD method in Thermo-Calc software based on available experimental results, in which the substitutional model is used and excess Gibbs energy is expressed with Redlich-Kister formalism. The

  18. Using CCT Diagrams to Optimize the Composition of an As-Rolled Dual-Phase Steel

    Science.gov (United States)

    Coldren, A. Phillip; Eldis, George T.

    1980-03-01

    A continuous-cooling transformation (CCT) diagram study was conducted for the purpose of optimizing the composition of a Mn-Si-Cr-Mo as-rolled dual-phase (ARDP) steel. The individual effects of chromium, molybdenum, and silicon on the allowable cooling rates were determined. On the basis of the CCT diagram study and other available information, an optimum composition was selected. Data from recent mill trials at three steel companies, involving steels with compositions in or near the newly recommended range, are presented and compared with earlier mill trial data. The comparison shows that the optimized composition is highly effective in making the steel's properties more uniform and reproducible in the as-rolled condition.

  19. Transport properties and phase diagram of UNi2Si2

    International Nuclear Information System (INIS)

    Ning, Y.B.; Garrett, J.D.; Datars, W.R.; McMaster Univ., Hamilton, ON

    1992-01-01

    The resistivity and Hall coefficient of single-crystal UNi 2 Si 2 have been studied in detail for the temperature range 4.2-300 K. The resistivity of UNi 2 Si 2 is largely due to magnetic scattering and the phonon scattering contribution is estimated to be about 14% at room temperature. At low temperatures, the resistivity can be described by a gapped spin-wave model plus a T 2 term. The temperature dependence of the Hall coefficient is accounted for by a theoretical model invoking skew scattering of conduction electrons by localized magnetic moments. Among the three magnetic phase transition temperatures, the two lower ones are found to be magnetic field dependent and shift with the field applied along the tetragonal c axis. Using the resistivity measurement in an applied magnetic field, a field-temperature phase diagram of UNi 2 Si 2 is presented. (author)

  20. Nonequilibrium phase diagram of a one-dimensional quasiperiodic system with a single-particle mobility edge

    Science.gov (United States)

    Purkayastha, Archak; Dhar, Abhishek; Kulkarni, Manas

    2017-11-01

    We investigate and map out the nonequilibrium phase diagram of a generalization of the well known Aubry-André-Harper (AAH) model. This generalized AAH (GAAH) model is known to have a single-particle mobility edge which also has an additional self-dual property akin to that of the critical point of the AAH model. By calculating the population imbalance, we get hints of a rich phase diagram. We also find a fascinating connection between single particle wave functions near the mobility edge of the GAAH model and the wave functions of the critical AAH model. By placing this model far from equilibrium with the aid of two baths, we investigate the open system transport via system size scaling of nonequilibrium steady state (NESS) current, calculated by fully exact nonequilibrium Green's function (NEGF) formalism. The critical point of the AAH model now generalizes to a `critical' line separating regions of ballistic and localized transport. Like the critical point of the AAH model, current scales subdiffusively with system size on the `critical' line (I ˜N-2 ±0.1 ). However, remarkably, the scaling exponent on this line is distinctly different from that obtained for the critical AAH model (where I ˜N-1.4 ±0.05 ). All these results can be understood from the above-mentioned connection between states near the mobility edge of the GAAH model and those of the critical AAH model. A very interesting high temperature nonequilibrium phase diagram of the GAAH model emerges from our calculations.

  1. Metastability in Field Theory and Statistical Mechanics

    International Nuclear Information System (INIS)

    Carvalho, C.A. de.

    1984-01-01

    After a phase transition analysis which can occur in the framework of a scalar field theory, at finite temperature and in presence of a external field, possibles metastable situations are studied and also how is their relationship with the transitions. In both cases it is used a semiclassical approximation to the theory which, in Statistical Mechanics, corresponds to the droplet-bubble model. (L.C.) [pt

  2. Formation of metastable tetragonal zirconia nanoparticles: Competitive influence of the dopants and surface state

    Energy Technology Data Exchange (ETDEWEB)

    Gorban, Oksana, E-mail: matscidep@aim.com [Donetsk Institute for Physics and Engineering named after A.A. Galkin of the NAS of Ukraine, Nauki av. 46, Kyiv 03680 (Ukraine); Synyakina, Susanna; Volkova, Galina; Gorban, Sergey; Konstantiova, Tetyana [Donetsk Institute for Physics and Engineering named after A.A. Galkin of the NAS of Ukraine, Nauki av. 46, Kyiv 03680 (Ukraine); Lyubchik, Svetlana, E-mail: s_lyubchik@yahoo.com [REQUIMTE, Universida de Nova de Lisboa, 2829-516 Caparica (Portugal)

    2015-12-15

    The effect of the surface modification of the nanoparticles of amorphous and crystalline partially stabilized zirconia by fluoride ions on stability of the metastable tetragonal phase was investigated. Based on the DSC, titrimetry and FTIR spectroscopy data it was proven that surface modification of the xerogel resulted from an exchange of the fluoride ions with the basic OH groups. The effect of the powder pre-calcination temperature before modification on the formation of metastable tetragonal phase in partially stabilized zirconia was investigated. It was shown that the main factor of tetragonal zirconia stabilization is the state of nanoparticles surface at pre-crystallization temperatures.

  3. Determination of the magnetocaloric entropy change in the presence of phase separation and metastability: The case of Eu0.58Sr0.42MnO3

    International Nuclear Information System (INIS)

    Guillou, F.; Hardy, V.; Fruchart, D.; Zawilski, B.

    2014-01-01

    The magnetocaloric effect (MCE) in the manganite Eu 0.58 Sr 0.42 MnO 3 was derived by different methods, in a field range very sensitive to the phenomenon of phase separation. It turns out that a strong scatter in the MCE features was observed. When the applied field is less than the field required to complete the transition, it is found that the MCE can be strongly overestimated by “standard” indirect measurements. A way to properly estimate the MCE around a first order transition in the presence of phase separation and metastability is proposed. - Highlights: • The entropy change was investigated in an oxide with pronounced metastable effects. • A strong scatter is observed among results derived from several indirect methods. • It is found that even the calorimetric approach can be proned to artefacts. • A method is proposed to evaluate a “real” magnetocaloric entropy change

  4. FIRST-PRINCIPLES PHASE DIAGRAM OF THE Ce-Th SYSTEM

    International Nuclear Information System (INIS)

    Landa, A; Soderlind, P

    2005-01-01

    Actinide physics has seen a remarkable focus the last decade or so due to the combination of improved experimental diamond-anvil-cell techniques and the development of fast computers and more advanced theory. All f-electron systems are expected to have multiphase phase diagrams due to the sensitivity of the f-electron band to external influences such as pressure and temperature. For instance, compression of an f-electron metal generally causes the occupation of f-states to change due to the shift of these bands relative to others. This can in some cases, as in the Ce-Th system, cause the crystal to adopt a lower symmetry structure at elevated pressures. Here we study the phase stabilities of Ce, Th, and the Ce-Th system as a function of compression. Theoretically, both Ce and Th metals are rather well described within the DFT, although a proper treatment of the Ce-Th alloys has not yet been presented. In the present paper we revisit this problem by applying the modern theory of random alloys based on the coherent potential approximation (CPA)

  5. Magnetic phase diagrams from non-collinear canonical band theory

    DEFF Research Database (Denmark)

    Shallcross, Sam; Nordstrom, L.; Sharma, S.

    2007-01-01

    A canonical band theory of non-collinear magnetism is developed and applied to the close packed fcc and bcc crystal structures. This is a parameter-free theory where the crystal and magnetic symmetry and exchange splitting uniquely determine the electronic bands. In this way, we are able...... hybridization, and on this basis we are able to analyze the microscopic reasons behind the occurrence of non-collinear magnetism in the elemental itinerant magnets....... to construct phase diagrams of magnetic order for the fcc and bcc lattices. Several examples of non-collinear magnetism are seen to be canonical in origin, in particular, that of gamma-Fe. In this approach, the determination of magnetic stability results solely from changes in kinetic energy due to spin...

  6. Phase Diagram and Electronic Structure of Praseodymium and Plutonium

    Directory of Open Access Journals (Sweden)

    Nicola Lanatà

    2015-01-01

    Full Text Available We develop a new implementation of the Gutzwiller approximation in combination with the local density approximation, which enables us to study complex 4f and 5f 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.

  7. Combinatorial materials synthesis and high-throughput screening: an integrated materials chip approach to mapping phase diagrams and discovery and optimization of functional materials.

    Science.gov (United States)

    Xiang, X D

    Combinatorial materials synthesis methods and high-throughput evaluation techniques have been developed to accelerate the process of materials discovery and optimization and phase-diagram mapping. Analogous to integrated circuit chips, integrated materials chips containing thousands of discrete different compositions or continuous phase diagrams, often in the form of high-quality epitaxial thin films, can be fabricated and screened for interesting properties. Microspot x-ray method, various optical measurement techniques, and a novel evanescent microwave microscope have been used to characterize the structural, optical, magnetic, and electrical properties of samples on the materials chips. These techniques are routinely used to discover/optimize and map phase diagrams of ferroelectric, dielectric, optical, magnetic, and superconducting materials.

  8. Optimization of the thermodynamic properties and phase diagrams of P2O5-containing systems

    Science.gov (United States)

    Hudon, Pierre; Jung, In-Ho

    2014-05-01

    P2O5 is an important oxide component in the late stage products of numerous igneous rocks such as granites and pegmatites. Typically, P2O5 combines with CaO and crystallizes in the form of apatite, while in volatile-free conditions, Ca-whitlockite is formed. In spite of their interest, the thermodynamic properties and phase diagrams of P2O5-containg systems are not well known yet. In the case of the pure P2O5 for example, no experimental thermodynamic data are available for the liquid and the O and O' solid phases. As a result, we re-evaluated all the thermodynamic and phase diagram data of the P2O5 unary system [1]. Optimization of the thermodynamic properties and phase diagrams of the binary P2O5 systems was then performed including the Li2O-, Na2O-, MgO-, CaO-, BaO-, MnO-, FeO-, Fe2O3-, ZnO-, Al2O3-, and SiO2-P2O5 [2] systems. All available thermodynamic and phase equilibrium data were simultaneously reproduced in order to obtain a set of model equations for the Gibbs energies of all phases as functions of temperature and composition. In particular, the Gibbs energy of the liquid solution was described using the Modified Quasichemical Model [3-5] implemented in the FactSage software [6]. Thermodynamic modeling of the Li2O-Na2O-K2O-MgO-CaO-FeO-Fe2O3-Al2O3-SiO2 system, which include many granite-forming minerals such as nepheline, leucite, pyroxene, melilite, feldspar and spinel is currently in progress. [1] Jung, I.-H., Hudon, P. (2012) Thermodynamic assessment of P2O5. J. Am. Ceram. Soc., 95 (11), 3665-3672. [2] Rahman, M., Hudon, P. and Jung, I.-H. (2013) A coupled experimental study and thermodynamic modeling of the SiO2-P2O5 system. Metall. Mater. Trans. B, 44 (4), 837-852. [3] Pelton, A.D. and Blander, M. (1984) Computer-assisted analysis of the thermodynamic properties and phase diagrams of slags. Proc. AIME Symp. Metall. Slags Fluxes, TMS-AIME, 281-294. [4] Pelton, A.D. and Blander, M. (1986) Thermodynamic analysis of ordered liquid solutions by a modified

  9. Understanding agent-based models of financial markets: A bottom-up approach based on order parameters and phase diagrams

    Science.gov (United States)

    Lye, Ribin; Tan, James Peng Lung; Cheong, Siew Ann

    2012-11-01

    We describe a bottom-up framework, based on the identification of appropriate order parameters and determination of phase diagrams, for understanding progressively refined agent-based models and simulations of financial markets. We illustrate this framework by starting with a deterministic toy model, whereby N independent traders buy and sell M stocks through an order book that acts as a clearing house. The price of a stock increases whenever it is bought and decreases whenever it is sold. Price changes are updated by the order book before the next transaction takes place. In this deterministic model, all traders based their buy decisions on a call utility function, and all their sell decisions on a put utility function. We then make the agent-based model more realistic, by either having a fraction fb of traders buy a random stock on offer, or a fraction fs of traders sell a random stock in their portfolio. Based on our simulations, we find that it is possible to identify useful order parameters from the steady-state price distributions of all three models. Using these order parameters as a guide, we find three phases: (i) the dead market; (ii) the boom market; and (iii) the jammed market in the phase diagram of the deterministic model. Comparing the phase diagrams of the stochastic models against that of the deterministic model, we realize that the primary effect of stochasticity is to eliminate the dead market phase.

  10. Phase Diagrams of Three-Dimensional Anderson and Quantum Percolation Models Using Deep Three-Dimensional Convolutional Neural Network

    Science.gov (United States)

    Mano, Tomohiro; Ohtsuki, Tomi

    2017-11-01

    The three-dimensional Anderson model is a well-studied model of disordered electron systems that shows the delocalization-localization transition. As in our previous papers on two- and three-dimensional (2D, 3D) quantum phase transitions [J. Phys. Soc. Jpn. 85, 123706 (2016), 86, 044708 (2017)], we used an image recognition algorithm based on a multilayered convolutional neural network. However, in contrast to previous papers in which 2D image recognition was used, we applied 3D image recognition to analyze entire 3D wave functions. We show that a full phase diagram of the disorder-energy plane is obtained once the 3D convolutional neural network has been trained at the band center. We further demonstrate that the full phase diagram for 3D quantum bond and site percolations can be drawn by training the 3D Anderson model at the band center.

  11. Universal scattering response across the type-II Weyl semimetal phase diagram

    Science.gov (United States)

    Rüßmann, P.; Weber, A. P.; Glott, F.; Xu, N.; Fanciulli, M.; Muff, S.; Magrez, A.; Bugnon, P.; Berger, H.; Bode, M.; Dil, J. H.; Blügel, S.; Mavropoulos, P.; Sessi, P.

    2018-02-01

    The discovery of Weyl semimetals represents a significant advance in topological band theory. They paradigmatically enlarged the classification of topological materials to gapless systems while simultaneously providing experimental evidence for the long-sought Weyl fermions. Beyond fundamental relevance, their high mobility, strong magnetoresistance, and the possible existence of even more exotic effects, such as the chiral anomaly, make Weyl semimetals a promising platform to develop radically new technology. Fully exploiting their potential requires going beyond the mere identification of materials and calls for a detailed characterization of their functional response, which is severely complicated by the coexistence of surface- and bulk-derived topologically protected quasiparticles, i.e., Fermi arcs and Weyl points, respectively. Here, we focus on the type-II Weyl semimetal class in which we find a stoichiometry-dependent phase transition from a trivial to a nontrivial regime. By exploring the two extreme cases of the phase diagram, we demonstrate the existence of a universal response of both surface and bulk states to perturbations. We show that quasiparticle interference patterns originate from scattering events among surface arcs. Analysis reveals that topologically nontrivial contributions are strongly suppressed by spin texture. We also show that scattering at localized impurities can generate defect-induced quasiparticles sitting close to the Weyl point energy. These give rise to strong peaks in the local density of states, which lift the Weyl node, significantly altering the pristine low-energy spectrum. Remarkably, by comparing the WTe2 and the MoTe2 cases we found that scattering response and topological transition are not directly linked. Visualizing the existence of a universal microscopic response to scattering has important consequences for understanding the unusual transport properties of this class of materials. Overall, our observations provide

  12. A metastable helium trap for atomic collision physics

    International Nuclear Information System (INIS)

    Colla, M.; Gulley, R.; Uhlmann, L.; Hoogerland, M.D.; Baldwin, K.G.H.; Buckman, S.J.

    1999-01-01

    Full text: Metastable helium in the 2 3 S state is an important species for atom optics and atomic collision physics. Because of its large internal energy (20eV), long lifetime (∼8000s) and large collision cross section for a range of processes, metastable helium plays an important role in atmospheric physics, plasma discharges and gas laser physics. We have embarked on a program of studies on atom-atom and electron-atom collision processes involving cold metastable helium. We confine metastable helium atoms in a magneto-optic trap (MOT), which is loaded by a transversely collimated, slowed and 2-D focussed atomic beam. We employ diode laser tuned to the 1083 nm (2 3 S 1 - 2 3 P2 1 ) transition to generate laser cooling forces in both the loading beam and the trap. Approximately 10 million helium atoms are trapped at temperatures of ∼ 1mK. We use phase modulation spectroscopy to measure the trapped atomic density. The cold, trapped atoms can collide to produce either atomic He + or molecular He 2 + ions by Penning Ionisation (PI) or Associative Ionisation (AI). The rate of formation of these ions is dependant upon the detuning of the trapping laser from resonance. A further laser can be used to connect the 2 3 S 1 state to another higher lying excited state, and variation of the probe laser detuning used to measure interatomic collision potential. Electron-atom collision processes are studied using a monochromatic electron beam with a well defined spatial current distribution. The total trap loss due to electron collisions is measured as a function of electron energy. Results will be presented for these atomic collision physics measurements involving cold, trapped metastable helium atoms. Copyright (1999) Australian Optical Society

  13. Collisional interaction between metastable neon atoms

    Energy Technology Data Exchange (ETDEWEB)

    Drunen, Wouter Johannes van

    2008-07-07

    In this thesis, the study of cold gases of neon atoms in different metastable states is described. It contains measurements of the collisional parameters for both the 3s[3/2]{sub 2} and the 3s'[1/2]{sub 0} metastable state and the dependence of the inelastic loss on external fields. Furthermore, the investigation of frequency dependent laser-induced collisions, and the possibility to excite photoassociation resonances is presented. For the measurements described here, neon atoms have been confined in a magnetooptical trap, in a magnetostatic trap, or in an optical dipole trap, respectively. By laser cooling inside the magnetic trap, atomic samples with more than 95 percent occupation of the magnetic substate m{sub J} = +2 could be prepared. They have a typical temperature of 0.5 mK, central densities up to 10{sup 11} cm{sup -3}, and a central phase-space density of up to 2.2.10{sup -7}. After loading the optical dipole trap from the magnetic trap, 2.5.10{sup 6} atoms with typical temperatures of 0.1 mK, and central densities up to 5.10{sup 10} cm{sup -3} were trapped. By evaporative cooling of the atoms in the magnetic trap we could increase the phase-space density by a factor of 200 to 5.10{sup -5}. Investigating the frequency dependence of laser-induced collisions did not reveal an experimental signature for the excitation of photoassociation resonances. For the {sup 3}D{sub 3} line a frequency dependence of laser enhanced Penning ionization was observed. Measurement of the two-body loss coefficient as function of the magnetic field showed a field dependence of the inelastic loss. These losses increase towards both small and large offset fields. The implementation of an optical dipole trap allowed us to trap the {sup 3}P{sub 0} metastable state. From the trap loss measurements we determined the two-body loss coefficient of the {sup 3}P{sub 0} metastable state for both bosonic isotopes {sup 20}Ne and {sup 22}Ne. For {sup 20}Ne we obtained {beta}=6{sup +5}{sub

  14. Multicritical phase diagrams of the spin-((3)/(2)) Blume-Emery-Griffiths model on the Bethe lattice using the recursion method

    International Nuclear Information System (INIS)

    Ekiz, Cesur; Albayrak, Erhan; Keskin, Mustafa.

    2003-01-01

    The multicritical behaviour of the spin-((3)/(2)) Blume-Emery-Griffiths model with bilinear and biquadratic exchange interactions and single-ion crystal field is studied on the Bethe lattice by introducing two-sublattices A and B within the exact recursion equations. Exact expressions for the free energy, the Curie or second-order phase transition temperatures, as well as for the magnetization and quadrupolar moment order parameters are obtained. The general procedure of investigation of critical properties is discussed and phase diagrams are obtained, in particular, for negative biquadratic couplings. The phase diagram of the model exhibits a rich variety of behaviours. Results are compared with other approximate methods

  15. Phase diagram of Rydberg atoms with repulsive van der Waals interaction

    International Nuclear Information System (INIS)

    Osychenko, O. N.; Astrakharchik, G. E.; Boronat, J.; Lutsyshyn, Y.; Lozovik, Yu. E.

    2011-01-01

    We report a quantum Monte Carlo calculation of the phase diagram of bosons interacting with a repulsive inverse sixth power pair potential, a model for assemblies of Rydberg atoms in the local van der Waals blockade regime. The model can be parametrized in terms of just two parameters, the reduced density and temperature. Solidification happens to the fcc phase. At zero temperature, the transition density is found with the diffusion Monte Carlo method at density ρ=3.9 ((ℎ/2π) 2 /mC 6 ) 3/4 , where C 6 is the strength of the interaction. The solidification curve at nonzero temperature is studied with the path-integral Monte Carlo approach and is compared with transitions in corresponding harmonic and classical crystals. Relaxation mechanisms are considered in relation to present experiments.

  16. Chimera and modulated drift states in a ring of nonlocally coupled oscillators with heterogeneous phase lags

    Science.gov (United States)

    Choe, Chol-Ung; Kim, Ryong-Son; Ri, Ji-Song

    2017-09-01

    We consider a ring of phase oscillators with nonlocal coupling strength and heterogeneous phase lags. We analyze the effects of heterogeneity in the phase lags on the existence and stability of a variety of steady states. A nonlocal coupling with heterogeneous phase lags that allows the system to be solved analytically is suggested and the stability of solutions along the Ott-Antonsen invariant manifold is explored. We present a complete bifurcation diagram for stationary patterns including the uniform drift and modulated drift states as well as chimera state, which reveals that the stable modulated drift state and a continuum of metastable drift states could occur due to the heterogeneity of the phase lags. We verify our theoretical results using the direct numerical simulations of the model system.

  17. Structure and phase behavior of a confined nanodroplet composed of the flexible chain molecules.

    Science.gov (United States)

    Kim, Soon-Chul; Kim, Eun-Young; Seong, Baek-Seok

    2011-04-28

    A polymer density functional theory has been employed for investigating the structure and phase behaviors of the chain polymer, which is modelled as the tangentially connected sphere chain with an attractive interaction, inside the nanosized pores. The excess free energy of the chain polymer has been approximated as the modified fundamental measure-theory for the hard spheres, the Wertheim's first-order perturbation for the chain connectivity, and the mean-field approximation for the van der Waals contribution. For the value of the chemical potential corresponding to a stable liquid phase in the bulk system and a metastable vapor phase, the flexible chain molecules undergo the liquid-vapor transition as the pore size is reduced; the vapor is the stable phase at small volume, whereas the liquid is the stable phase at large volume. The wide liquid-vapor coexistence curve, which explains the wide range of metastable liquid-vapor states, is observed at low temperature. The increase of temperature and decrease of pore size result in a narrowing of liquid-vapor coexistence curves. The increase of chain length leads to a shift of the liquid-vapor coexistence curve towards lower values of chemical potential. The coexistence curves for the confined phase diagram are contained within the corresponding bulk liquid-vapor coexistence curve. The equilibrium capillary phase transition occurs at a higher chemical potential than in the bulk phase.

  18. Radiation-stimulated phase in titanium dihydride TiH1.95

    International Nuclear Information System (INIS)

    Khidirov, I.; Mukhtarova, N.N.; Baktibaev, K.O.; Getmanskiy, V.V.

    2001-01-01

    In titanium dihydride TiH 1.95 γ-irradiation has been shown by X-ray and neutron-diffraction methods to stimulate the phase transition FCC→VCT at doses ≥3·10 10 R and irradiation temperature ≅100 d eg C. The space group of the formed phase is D 4h 17 -14/mmm, its lattice parameters a m =0.3161 nm, c m =0.4418 nm are related to parameters of the initial (FCC) phase by relations a m ≅a k /2 1/2 , c m ≅a k . It was established that the phase obtained is metastable, it relaxes at the temperatures ≥37 d eg C and transforms into the stable FCC phase that corresponds to the equilibrium phase diagram of Ti-H system. The temperature of the phase transition increases by influence of γ-quanta, the radiation-stimulated phase differs from thermostimulated one by a larger unit cell and a smaller degree of tetragonal distortion. (author)

  19. Phase diagrams of site diluted ferromagnetic thin film

    International Nuclear Information System (INIS)

    Hamedoun, M.; Bouslykhane, K.; Bakrim, H.; Hourmatallah, A.; Benzakour, N.; Masrour, R.

    2006-01-01

    The phase transition properties of Ising, classical XY and Heisenberg of diluted ferromagnetic thin film are studied by the method of exact high-temperature series expansions extrapolated with the Pade approximants method. The reduced critical temperature τ c of the diluted ferromagnetic thin films is studied as a function of film thickness L and the exchange interactions in the bulk J b , in the surface J s and between surface and nearest-neighbour layer J - bar . It is found that τ c increases with the exchange interactions of surface and L. The magnetic phase diagram (τ c versus dilution x) is obtained. A critical value of the surface exchange interaction above which the surface magnetism appears is obtained. The dependence of the critical parameter of surface reduced coupling R 2 c as a function of the dilution x and the ratio of the exchange interaction between the surface and nearest-neighbour layer to the bulk one R 1 for the three studied models has been investigated. The percolation threshold is defined as the concentration x p at which τ c =0. The obtained values are x p ∼0.2 in the bulk and x p ∼0.4 at the surface

  20. Phase Diagram of Kob-Andersen-Type Binary Lennard-Jones Mixtures

    Science.gov (United States)

    Pedersen, Ulf R.; Schrøder, Thomas B.; Dyre, Jeppe C.

    2018-04-01

    The binary Kob-Andersen (KA) Lennard-Jones mixture is the standard model for computational studies of viscous liquids and the glass transition. For very long simulations, the viscous KA system crystallizes, however, by phase separating into a pure A particle phase forming a fcc crystal. We present the thermodynamic phase diagram for KA-type mixtures consisting of up to 50% small (B ) particles showing, in particular, that the melting temperature of the standard KA system at liquid density 1.2 is 1.028(3) in A particle Lennard-Jones units. At large B particle concentrations, the system crystallizes into the CsCl crystal structure. The eutectic corresponding to the fcc and CsCl structures is cutoff in a narrow interval of B particle concentrations around 26% at which the bipyramidal orthorhombic PuBr3 structure is the thermodynamically stable phase. The melting temperature's variation with B particle concentration at two constant pressures, as well as at the constant density 1.2, is estimated from simulations at pressure 10.19 using isomorph theory. Our data demonstrate approximate identity between the melting temperature and the onset temperature below which viscous dynamics appears. Finally, the nature of the solid-liquid interface is briefly discussed.

  1. Metastable states of plasma particles close to a charged surface

    Energy Technology Data Exchange (ETDEWEB)

    Shavlov, A. V., E-mail: shavlov@ikz.ru [The Institute of the Earth Cryosphere, RAS Siberian branch, 625000, P.O. 1230, Tyumen (Russian Federation); Tyumen State Oil and Gas University, 38, Volodarskogo St., 625000, Tyumen (Russian Federation); Dzhumandzhi, V. A. [The Institute of the Earth Cryosphere, RAS Siberian branch, 625000, P.O. 1230, Tyumen (Russian Federation)

    2015-09-15

    The free energy of the plasma particles and the charged surface that form an electroneutral system is calculated on the basis of the Poisson-Boltzmann equation. It is shown that, owing to correlation of light plasma particles near the charged surface and close to heavy particles of high charge, there can be metastable states in plasma. The corresponding phase charts of metastable states of the separate components of plasma, and plasma as a whole, are constructed. These charts depend on temperature, the charge magnitude, the size of the particles, and the share of the charge of the light carriers out of the total charge of the plasma particles.

  2. Method of non-interacting thermodynamic calculation of binary phase diagrams containing p disordered phases with variable composition and q phases with constant composition at (p, q) ≤ 10

    International Nuclear Information System (INIS)

    Udovskij, A.L.; Karpushkin, V.N.; Nikishina, E.A.

    1991-01-01

    Method of non-interacting thermodynamic calculation of state diagram of binary systems contacting p disordered phases with variable composition and q phases with constant composition for (p, q) ≤ 10 case is developed. Determination of all possible solutions of phase equilibrium equations is realized in the method. Certain application examples of computer-realized method of T-x thermodynamic calculation using PC for Cr-W, Ni-W, Ni-Al, Ni-Re binary systems are given

  3. Hydrothermal synthesis and characterization of a two-dimensional piperazinium cobalt–zinc phosphate via a metastable one-dimensional phase

    Energy Technology Data Exchange (ETDEWEB)

    Torre-Fernández, Laura; Khainakova, Olena A. [Departamentos de Química Física y Analítica y Química Orgánica e Inorgánica, Universidad de Oviedo-CINN, 33006 Oviedo (Spain); Espina, Aránzazu [Servicios Científico Técnicos, Universidad de Oviedo, 33006 Oviedo (Spain); Amghouz, Zakariae, E-mail: amghouz.uo@uniovi.es [Servicios Científico Técnicos, Universidad de Oviedo, 33006 Oviedo (Spain); Khainakov, Sergei A. [Servicios Científico Técnicos, Universidad de Oviedo, 33006 Oviedo (Spain); Alfonso, Belén F.; Blanco, Jesús A. [Departamento de Física, Universidad de Oviedo, 33007 Oviedo (Spain); García, José R.; García-Granda, Santiago [Departamentos de Química Física y Analítica y Química Orgánica e Inorgánica, Universidad de Oviedo-CINN, 33006 Oviedo (Spain)

    2015-05-15

    A two-dimensional piperazinium cobalt–zinc phosphate, formulated as (C{sub 4}N{sub 2}H{sub 12}){sub 1.5}(Co{sub 0.6}Zn{sub 0.4}){sub 2}(HPO{sub 4}){sub 2}(PO{sub 4})·H{sub 2}O (2D), was synthesized under hydrothermal conditions. The crystal structure was determined using single-crystal X-ray diffraction data (monoclinic P2{sub 1}/c, a=8.1165(3) Å, b=26.2301(10) Å, c=8.3595(4) Å, and β=110.930(5)°) and the hydrogen atom positions were optimized by DFT calculations. A single-crystal corresponding to one-dimensional metastable phase, (C{sub 4}N{sub 2}H{sub 12})Co{sub 0.3}Zn{sub 0.7}(HPO{sub 4}){sub 2}·H{sub 2}O (1D), was also isolated and the crystal structure was determined (monoclinic P2{sub 1}/c, a=8.9120(6) Å, b=14.0290(1) Å, c=12.2494(5) Å, and β=130.884(6)°). The bulk was characterized by chemical (C–H–N) analysis, powder X-ray diffraction (PXRD), powder X-ray thermodiffractometry (HT-XRD), transmission electron microscopy (STEM(DF)-EDX and EFTEM), and thermal analysis (TG/SDTA-MS), including activation energy data of its thermal decomposition. The magnetic susceptibility and magnetization measurements show no magnetic ordering down to 4 K. - Graphical abstract: Hydrothermal synthesis and structural characterization of a two-dimensional piperazinium cobalt–zinc phosphate, (C{sub 4}N{sub 2}H{sub 12}){sub 1.5}(Co{sub 0.6}Zn{sub 0.4}){sub 2}(HPO{sub 4}){sub 2}(PO{sub 4})·H{sub 2}O (2D), have been reported. The crystal structure of a one-dimensional piperazinium cobalt–zinc phosphate, (C{sub 4}N{sub 2}H{sub 12})Co{sub 0.3}Zn{sub 0.7}(HPO{sub 4}){sub 2}·H{sub 2}O (1D) a metastable phase during the hydrothermal synthesis, was also determined. The thermal behavior of 2D compound is strongly dependent on the selected heating rate and the magnetic susceptibility and magnetization measurements show no magnetic ordering down to 4 K. - Highlights: • A 2D piperazinium cobalt–zinc phosphate has been synthesized and characterized. • Crystal

  4. Diagram Techniques in Group Theory

    Science.gov (United States)

    Stedman, Geoffrey E.

    2009-09-01

    Preface; 1. Elementary examples; 2. Angular momentum coupling diagram techniques; 3. Extension to compact simple phase groups; 4. Symmetric and unitary groups; 5. Lie groups and Lie algebras; 6. Polarisation dependence of multiphoton processes; 7. Quantum field theoretic diagram techniques for atomic systems; 8. Applications; Appendix; References; Indexes.

  5. Formation of metastable cubic phase in Ce{sub 100−x}Al{sub x} (x=45, 50) alloys and their thermal and magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Idzikowski, Bogdan, E-mail: idzi@ifmpan.poznan.pl [Institute of Molecular Physics, Polish Academy of Sciences, M. Smoluchowskiego 17, 60-179 Poznań (Poland); Centre for Advanced Materials and Smart Structures, Polish Academy of Sciences, Okólna 2, 50-422 Wrocław (Poland); Śniadecki, Zbigniew [Institute of Molecular Physics, Polish Academy of Sciences, M. Smoluchowskiego 17, 60-179 Poznań (Poland); Centre for Advanced Materials and Smart Structures, Polish Academy of Sciences, Okólna 2, 50-422 Wrocław (Poland); Puźniak, Roman [Institute of Physics, Polish Academy of Sciences, Aleja Lotników 32/46, 02-668 Warszawa (Poland); Kaczorowski, Dariusz [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wrocław (Poland); Centre for Advanced Materials and Smart Structures, Polish Academy of Sciences, Okólna 2, 50-422 Wrocław (Poland)

    2017-01-01

    Ce{sub 100−x}Al{sub x} (x=45 and 50) alloys were synthesized by rapid quenching technique in the form of ribbons composed of nanocrystalline phase of CeAl with the ClCs-type structure (Pm-3m space group) embedded in an amorphous matrix. The cubic CeAl phase is known as metastable with random distribution of Ce and Al atoms in the unit cell. The crystalline volume fraction is about 7.5% in Ce{sub 55}Al{sub 45} and 3% in Ce{sub 50}Al{sub 50}. The alloy Ce{sub 55}Al{sub 45} shows better thermal stability than Ce{sub 50}Al{sub 50}, indicated by higher effective activation energy and higher crystallization temperature. Small off-stoichiometry in Ce{sub 55}Al{sub 45} results in degrading the glass forming ability and promotes formation of the cubic CeAl phase, as confirmed by magnetic measurements. In both alloys, the Ce ions are in stable trivalent state and order magnetically near 20 K. Another magnetic phase transition close to 10 K was found for Ce{sub 50}Al{sub 50} and was attributed to the presence of the well-known stable orthorhombic CeAl phase. To the best of our knowledge, the magnetic behavior of the CeAl cubic phase is reported here for the first time. - Highlights: • Synthesis of metastable cubic CeAl phase by rapid quenching. • The Ce ions in Ce{sub 55}Al{sub 45} and Ce{sub 50}Al{sub 50} are in stable trivalent state. • Magnetic transition near 10 K connected with the orthorhombic CeAl phase. • Phase transition at about 20 K originates from the cubic CeAl phase.

  6. 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.

  7. Decomposition of the metastable phase γU in U-7% and U-7% Mo-0.9% Pt

    International Nuclear Information System (INIS)

    Arico, Sergio F.; Gribaudo, Luis M.

    2004-01-01

    The 'Reduced Enrichment for Research and Test Reactors' is an international project for the development of a nuclear fuel with high density in uranium capable to get a great neutron flux with good capacity for being reprocessed. One of the candidates is a fuel containing U-Mo alloy powder, as bcc metastable phase γ, dispersed in Al powder. In order to know the influence of Pt as a stabilizing element two U-7 wt.% Mo alloys are studied, one of them with 0.9 wt.% Pt. They were fabricated in an arc furnace and both homogenized in composition during 2 h at 1000 C degrees. Then, isothermal treatments at 480, 430 and 350 C degrees were performed at times between 1 and 177 h. The decomposition of the γ phase was studied by metallography and X-ray diffraction analysis. Adding Pt, the start of the decomposition of the γ phase is delayed, but the initial grain size of the alloys is an important variable which has also to be considered. (author) [es

  8. Operations space diagram for ECRH and ECCD

    DEFF Research Database (Denmark)

    Bindslev, H.

    2004-01-01

    at the design phase. At the operations phase it may also prove useful in setting up experimental scenarios by showing operational possibilities, avoiding the need for survey type ray-tracing at the initial planning stages. The diagram may also serve the purpose of communicating operational possibilities to non......A Clemmov-Mullaly-Allis (CMA) type diagram, the ECW-CMA diagram, for representing the operational possibilities of electron cyclotron heating and current drive (ECRH/ECCD) systems for fusion plasmas is presented. In this diagram, with normalized density and normalized magnetic field coordinates......, the parameter range in which it is possible to achieve a given task (e.g. O-mode current drive for stabilizing a neoclassical tearing mode) appears as a region. With also the Greenwald density limit shown, this diagram condenses the information on operational possibilities, facilitating the overview required...

  9. 450 {sup o}C isothermal section of the Fe-Zn-Si ternary phase diagram

    Energy Technology Data Exchange (ETDEWEB)

    Su, Xuping [Inst. of Materials Research, School of Mechanical Engineering, Xiangtan Univ., Xiangtan, Hunan (China); Univ. of Toronto, Dept. of Materials Science and Engineering, Toronto, Ontario (Canada); Tang, Nai-Yong [Cominco Ltd., Product Technology Centre, Mississauga, Ontario (Canada); Toguri, J.M. [Univ. of Toronto, Dept. of Materials Science and Engineering, Toronto, Ontario (Canada)

    2001-07-01

    The 450 {sup o}C isothermal section of the Fe-Zn-Si ternary phase diagram has been determined experimentally using optical microscopy, scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS) and X-ray diffractometry. The focus of the work has been concentrated on the Zn-rich corner which is relevant to general galvanizing. The present study has confirmed the existence of the equilibrium state between the liquid, the {zeta} phase and the FeSi phase. This three phase equilibrium state prevents the equilibrium between the liquid and the {delta} phase suggested by some researchers. Experimental results indicate that Si solubility in all four binary Zn-Fe compounds is limited. The Fe solubility in molten Zn was found to decrease with increasing Si content in the melt. The liquid phase boundary was determined using a model based phenomenological approach. (author)

  10. Stress-temperature phase diagram of a ferromagnetic Ni-Mn-Ga shape memory alloy

    International Nuclear Information System (INIS)

    Chernenko, V.A.; Pons, J.; Cesari, E.; Ishikawa, K.

    2005-01-01

    A sequence of thermally and stress-induced intermartensitic transformations has been found in a Ni 52.0 Mn 24.4 Ga 23.6 single crystal, which have been confirmed by transmission electron microscopy through in situ cooling experiments. The stress-strain-temperature behavior under compression along the P and P crystallographic directions has also been studied for this compound and a stress-temperature phase diagram has been established

  11. Abnormal gas-liquid-solid phase transition behaviour of water observed with in situ environmental SEM.

    Science.gov (United States)

    Chen, Xin; Shu, Jiapei; Chen, Qing

    2017-04-24

    Gas-liquid-solid phase transition behaviour of water is studied with environmental scanning electron microscopy for the first time. Abnormal phenomena are observed. At a fixed pressure of 450 Pa, with the temperature set to -7 °C, direct desublimation happens, and ice grows continuously along the substrate surface. At 550 Pa, although ice is the stable phase according to the phase diagram, metastable liquid droplets first nucleate and grow to ~100-200 μm sizes. Ice crystals nucleate within the large sized droplets, grow up and fill up the droplets. Later, the ice crystals grow continuously through desublimation. At 600 Pa, the metastable liquid grows quickly, with some ice nuclei floating in it, and the liquid-solid coexistence state exists for a long time. By lowering the vapour pressure and/or increasing the substrate temperature, ice sublimates into vapour phase, and especially, the remaining ice forms a porous structure due to preferential sublimation in the concave regions, which can be explained with surface tension effect. Interestingly, although it should be forbidden for ice to transform into liquid phase when the temperature is well below 0 °C, liquid like droplets form during the ice sublimation process, which is attributed to the surface tension effect and the quasiliquid layers.

  12. Production method of carbamazepine/saccharin cocrystal particles by using two solution mixing based on the ternary phase diagram

    Science.gov (United States)

    Kudo, Shoji; Takiyama, Hiroshi

    2014-04-01

    In the pharmaceutical field, improvement of drug solubility is required, and an interest in cocrystals is growing. Crystallization methods for industrial production of cocrystals have not been developed enough whereas many cocrystals have been prepared in order to find a new crystal form by screening in the laboratory. The objective of this study was the development of the crystallization method which is useful for the industrial production of cocrystal particles based on the phase diagram. A cocrystal of carbamazepine and saccharin was selected as a model substance. The ternary phase diagram of carbamazepine and saccharin in methanol at 303 K was measured. A cocrystallization method of mixing two kinds of different eutectic solutions was designed based on the ternary phase diagram. In order to adjust the cocrystallization conditions, the determination method of the driving force for cocrystal deposition such as supersaturation based on mass balance was proposed. The cocrystal particles were obtained under all the conditions of the five mixing ratios. From these experimental results, the relationship between the supersaturation and the induction time for nucleation was confirmed as well as conventional crystallization. In conclusion, the crystallization method for industrial production of cocrystal particles including the determination of the supersaturation was suggested.

  13. 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.

  14. Phase diagrams of exceptional and supersymmetric lattice gauge theories

    International Nuclear Information System (INIS)

    Wellegehausen, Bjoern-Hendrik

    2012-01-01

    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 2 , that has a trivial centre. To investigate G 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.

  15. Fast production of Bose-Einstein condensates of metastable helium

    Science.gov (United States)

    Bouton, Q.; Chang, R.; Hoendervanger, A. L.; Nogrette, F.; Aspect, A.; Westbrook, C. I.; Clément, D.

    2015-06-01

    We report on the Bose-Einstein condensation of metastable 4He atoms using a hybrid approach, consisting of a magnetic quadrupole and an optical dipole trap. In our setup we cross the phase transition with 2 ×106 atoms, and we obtain pure condensates of 5 ×105 atoms in the optical trap. This approach to cooling 4He provides enhanced cycle stability, large optical access to the atoms and results in the production of a condensate every 6 s—a factor 2 faster than the state of the art. This speed-up will significantly reduce the data acquisition time needed for the measurement of many particle correlations, made possible by the ability of metastable helium atoms to be detected individually.

  16. Influence of the inter-ion interaction on the phase diagrams of the 1D Falicov-Kimball system

    Science.gov (United States)

    Gajek, Z.; Lemański, R.

    2004-05-01

    A model of itinerant, spinless electrons interacting with ions via the on-site Coulomb potential U, modified by the inter-ionic nearest-neighbour interaction V, is studied on the one-dimensional infinite lattice. Only periodical configurations of the ions with a limited number of lattice sites in a unit cell and their mixtures are taken into account. Phases whose energies reach minimum values for given electron and ion chemical potentials are selected and depicted for a set of model parameters. Then the results are translated into the ion density-electron density canonical phase diagrams and summarized in the electrondensity-U plane. The diagrams clearly show how various kinds of charge ordering evolve with V, starting from V=0 case, that represents the standard Falicov-Kimball model discussed previously.

  17. Influence of the inter-ion interaction on the phase diagrams of the 1D Falicov-Kimball system

    International Nuclear Information System (INIS)

    Gajek, Z.; Lemanski, R.

    2004-01-01

    A model of itinerant, spinless electrons interacting with ions via the on-site Coulomb potential U, modified by the inter-ionic nearest-neighbour interaction V, is studied on the one-dimensional infinite lattice. Only periodical configurations of the ions with a limited number of lattice sites in a unit cell and their mixtures are taken into account. Phases whose energies reach minimum values for given electron and ion chemical potentials are selected and depicted for a set of model parameters. Then the results are translated into the ion density-electron density canonical phase diagrams and summarized in the electron density-U plane. The diagrams clearly show how various kinds of charge ordering evolve with V, starting from V=0 case, that represents the standard Falicov-Kimball model discussed previously

  18. Influence of the inter-ion interaction on the phase diagrams of the 1D Falicov-Kimball system

    Energy Technology Data Exchange (ETDEWEB)

    Gajek, Z. E-mail: gajek@int.pan.wroc.pl; Lemanski, R

    2004-05-01

    A model of itinerant, spinless electrons interacting with ions via the on-site Coulomb potential U, modified by the inter-ionic nearest-neighbour interaction V, is studied on the one-dimensional infinite lattice. Only periodical configurations of the ions with a limited number of lattice sites in a unit cell and their mixtures are taken into account. Phases whose energies reach minimum values for given electron and ion chemical potentials are selected and depicted for a set of model parameters. Then the results are translated into the ion density-electron density canonical phase diagrams and summarized in the electron density-U plane. The diagrams clearly show how various kinds of charge ordering evolve with V, starting from V=0 case, that represents the standard Falicov-Kimball model discussed previously.

  19. Approaching the Type-II Dirac Point and Concomitant Superconductivity in Pt-doping Stabilized Metastable 1T-phase IrTe2

    OpenAIRE

    Fei, Fucong; Bo, Xiangyan; Wang, Pengdong; Ying, Jianghua; Chen, Bo; Liu, Qianqian; Zhang, Yong; Sun, Zhe; Qu, Fanming; Zhang, Yi; Li, Jian; Song, Fengqi; Wan, Xiangang; Wang, Baigeng; Wang, Guanghou

    2017-01-01

    Topological semimetal is a topic of general interest in material science. Recently, a new kind of topological semimetal called type-II Dirac semimetal with tilted Dirac cones is discovered in PtSe2 family. However, the further investigation is hindered due to the huge energy difference from Dirac points to Fermi level and the irrelevant conducting pockets at Fermi surface. Here we characterize the optimized type-II Dirac dispersions in a metastable 1T phase of IrTe2. Our strategy of Pt doping...

  20. Scheil-Gulliver Constituent Diagrams

    Science.gov (United States)

    Pelton, Arthur D.; Eriksson, Gunnar; Bale, Christopher W.

    2017-06-01

    During solidification of alloys, conditions often approach those of Scheil-Gulliver cooling in which it is assumed that solid phases, once precipitated, remain unchanged. That is, they no longer react with the liquid or with each other. In the case of equilibrium solidification, equilibrium phase diagrams provide a valuable means of visualizing the effects of composition changes upon the final microstructure. In the present study, we propose for the first time the concept of Scheil-Gulliver constituent diagrams which play the same role as that in the case of Scheil-Gulliver cooling. It is shown how these diagrams can be calculated and plotted by the currently available thermodynamic database computing systems that combine Gibbs energy minimization software with large databases of optimized thermodynamic properties of solutions and compounds. Examples calculated using the FactSage system are presented for the Al-Li and Al-Mg-Zn systems, and for the Au-Bi-Sb-Pb system and its binary and ternary subsystems.