共查询到20条相似文献,搜索用时 15 毫秒
1.
Braga WS Kimura NM Luders DD Sampaio AR Santoro PA Palangana AJ 《The European physical journal. E, Soft matter》2007,24(3):247-250
The phase diagram is an interesting field of research, particularly in lyotropic liquid crystals (LLC). In this way, one of the most important phase diagrams of this LLC system was reported by Yu and Saupe. Two uniaxial (calamitic--N(C) and discotic--N(D)) and one biaxial nematic (N(B)) phases were determined by these authors. Furthermore, in this phase diagram the classical isotropic phase (I was observed at high temperature as well as a reentrant isotropic phase (I(RE)) which takes place at lower temperature. Later, this phase diagram was also studied by several authors and in all cases the I(RE)-N(C)-I phase transitions were not observed. In this work, we present a study of this phase diagram through digital image processing and refractometry optical techniques. The occurrence of these phase transitions is investigated and characterized. In addition, the order parameter is obtained based on the Vuks hypothesis from a particular point, in the range of the N(C) phase, where the absolute value of the optical birefringence (Deltan is maximum. 相似文献
2.
We calculate here the phase line equations using the mean field theory for the liquid-solid I - solid II phases in the ammonia close to the melting point. Our calculated phase line equations have been fitted to the experimental data. Our calculated phase diagram agrees very well with the experimentally obtained P-T phase diagram from the literature. 相似文献
3.
M. Beyer 《The European Physical Journal A - Hadrons and Nuclei》2003,18(2-3):471-473
From the viewpoint of statistical physics, nuclear matter is a strongly correlated many-particle system. Several regimes of the QCD phase diagram should exhibit strong correlations. Here I focus on three- and four-body correlations that might be important in the phase diagram.Received: 30 September 2002, Published online: 22 October 2003PACS:
21.65. + f Nuclear matter - 21.45. + v Few-body systems 相似文献
4.
A general phenomenological theory is presented for the phase behavior of ferromagnetic superconductors with spin-triplet electron Cooper pairing. The theory accounts in detail for the temperature-pressure phase diagram of ZrZn2, while the main features of the diagram for UGe2 are also described. Quantitative criteria are deduced for the U-type (type I) and Zr-type (type II) unconventional ferromagnetic superconductors with spin-triplet Cooper electron pairing. Some basic properties of quantum phase transitions are also elucidated. 相似文献
5.
Farid F. Abraham 《Physics Reports》1981,80(5):340-374
An extensive computer simulation investigation of the structure, thermodynamics and phase stability of the two-dimensional Lennard-Jones system is presented, with special emphasis on the low-pressure melting regime of the phase diagram. This investigation includes isobaric-isothermal Monte Carlo simulations of the various phases of the two-dimensional Lennard-Jones system and of the melting and vaporization processes in configuration space, the isodensity-isothermal Monte Carlo simulations of two-phase coexistence between crystal and liquid and between liquid and vapor, the determination of the phase diagram, the establishment of the thermodynamic melting temperature, and the determination of the physical significance of the Kosterlitz-Thouless-Feynman dislocation model for melting in relation to the stability of the crystalline phase. I conclude that th phase diagram of the Lennard-Jones system in two dimensions is qualitatively similar to that in three dimensions. Finally, I present a new simulation method for doing molecular dynamics at constant pressure and/or constant temperature, and employ this method to study the temporal-spatial evolution of two-dimensional melting and vaporization. 相似文献
6.
Hamilton JC 《Physical review letters》2002,88(12):126101
Overlayers on surfaces with square symmetry exhibit a huge variety of strain relief mechanisms. I present a simple 2D Frenkel-Kontorova model and calculate the associated zero temperature phase diagram which shows a transition from overlayers with square symmetry (and possible square dislocation patterns) to hexagonal symmetry. The phase diagram includes the experimentally observed clock-rotated phase. Local density approximation calculations suggested by the model show that a clean Ni(100) surface reconstructs from a bulk-terminated to a clock-rotated structure at biaxial compressive strains above 2.5%. 相似文献
7.
Batista CD 《Physical review letters》2002,89(16):166403
I show that a spontaneous electric polarization exists in the solution of the Falicov-Kimball model by mapping the strong coupling limit of this Hamiltonian into an xxz spin 1/2 model with a magnetic field. In this way, I determine the phase diagram of the strongly interacting model and show the existence of a transition to a mixed-valence regime containing two phases: an orbitally ordered state and a Bose-Einstein condensation of excitons with a built-in electric polarization. 相似文献
8.
E. N. Klimova M. -A. V. Zubkhadzhiev K. Yu. Dukaeva 《Bulletin of the Russian Academy of Sciences: Physics》2012,76(3):317-320
The nucleation of a new phase of a substance in a nonuniform stress field created during measurements of rigidity is considered.
The phase diagram of silicon containing the Si I, II, and V phases are considered. The high-pressure boundaries of the phases
formed near the indenter are found using the finite elements method. 相似文献
9.
Jochen Wambach 《Progress in Particle and Nuclear Physics》2008,61(1):290-296
I discuss pertinent aspects of the phase structure of strongly-interacting matter and their relation to the medium modifications of mesons. Special attention is paid to the critical endpoint in the phase diagram and the electromagnetic response in its vicinity. 相似文献
10.
《Physica B+C》1981,103(1):1-7
During the 1950s the present author had the benefit of studying with Wagner, Chipman, and Cohen, reading the work of Zener, Kubaschewski, Darken and Meijering, and having student colleagues such as Hillert, Hilliard and Cahn wiht whom one could argue and disagree. Notwithstanding the fact that all of these individuals contributed substantially to the author's appreciation of the interaction between thermochemistry and phase diagrams, none had a greater impact than J.L. Meijering. Although I did not meet him in person until 1967, I found that his 1950–1963 papers (listed below) and the extensive correspondence we conducted on lattice stability had the most profound influence on my own perception of the importance of phase diagram calculations. In this brief paper I hope to review Meijering's contribution to the development of our understanding of binary phase diagram characteristics, synthesis of ternary phase diagrams from the components binary diagrams, miscibility gap phenomena, magnetic contributions, and lattice stability. I will try to convince you of my own opinion that Meijering has been the most successful disciple of Van Laar in our time in enhancing the tradition of the Dutch school of thermodynamicists. 相似文献
11.
Resistively shunted junction dynamics is applied to the three-dimensional uniformly frustrated XY model with randomly perturbed couplings, as a model for driven steady states in a type-II superconductor with quenched point pinning. For a disorder strength p strong enough to produce a vortex glass in equilibrium, we map the phase diagram as a function of temperature T and uniform driving current I. Using finite size analysis and averaging over many realizations of quenched randomness we find a first-order melting T(m)(I) from a vortex line smectic to an anisotropic liquid. 相似文献
12.
J.A. Sauls 《物理学进展》2013,62(1):113-141
I review the principal theories that have been proposed for the superconducting phases of UPt3. The detailed H-T phase diagram places constraints on any theory for the multiple superconducting phases. Much attention has been given to the Ginzberg-Landau region of the phase diagram where the phase boundaries of three phases appear to meet at a tetracritical point. It has been argued that the existence of a tetracritical point for all field orientations eliminates the two-dimensional (2D) orbital representations coupled to a symmetry-breaking field (SBF) as a viable theory of these phases and favours either a theory based on two primary order parameters belonging to different irreducible representations that are accidentally degenerate, as described by Chen and Garg 1993, or a spin-triplet, orbital one-dimensional representation with non spin-orbit coupling in the pairing channel, as described by Machida and Ozaki 1991. I comment on the limitations of the models proposed so far for the superconducting phases of UPt3. I also find that a theory in which the order parameter belongs to an orbital 2D representation coupled to a SBF is a viable model for the phases of UPt3, based on the existing body of experimental data. Specifically, I show that the existing phase diagram (including an apparent tetracritical point for all field orientations), the anisotropy of the upper critical field over the full temperature range, the correlation between superconductivity and basal plane antiferromagnetism and the low-temperature power laws in the transport and thermodynamic properties can be explained qualitatively, and in many respects quantitatively, by an odd-parity E2u order parameter with a pair spin projection of zero along the ?c axis. The coupling of an antiferromagnetic moment to the superconducting order parameter acts as a SBF which is responsible for the apparent tetracritical point, in addition to the zero-field double transition. The new results presented here for the E2u representation are based on an analysis of the material parameters calculated within the Bardeen-Cooper-Schrieffer theory for the 2D representations, and a refinement of the SBF model given by Hess et al. (1989). I also discuss possible experiments to test the symmetry of the order parameter. 相似文献
13.
Clarke G Homan 《Journal of Physics and Chemistry of Solids》1975,36(11):1249-1254
The phase diagram of Bi has been studied by resistometric techniques in the temperature range of 30 to 300°K up to pressures of 140 kbars. Using the original Bridgman phase notation, the phase transitions I–II, II–III, I–III, III–IV and V–VI were observed. Two new phases, designated VIII and IX were observed in this region. The triple points occurring between I–II–III near 29.5 kbars and 160°K, between IV–V–VIII near 55 kbars and 240°K, between V–VI–VIII near 72 kbars and 255°K and between VI–VIII–IX near 135 kbars and 250°K. Earlier measurements were adjusted to the 1970 Drickamer pressure scale and compared to the present results. A phase diagram is proposed for pressures to 140 kbars. Calculations of the volume changes and latent heats of transformation are made near the triple points I–II–III, IV–V–VIII and V–VI–VIII using the measured volume changes of Bridgman for the I–II, IV–V and V–VI transitions. The latent heat associated with the III–IV transition was calculated using the volume data of Bridgman to be less than ? 2 cal/mol. 相似文献
14.
Ecker G. Paulus I. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1988,16(3):348-351
For pt.I see ibid., vol.16, no.3, p.342-7, June 1988. A physical model is presented of the development of a short cathode-anode vacuum arc, from the moment of electrode separation to the final state, a cathode-autonomous vacuum arc. Although the highly nonstationary initial phase is accessible only to qualitative reasoning, the analysis of the stationary arc is treated quantitatively, accounting for anode influence using an existence diagram. The cathode-autonomous phase is previously known in the literature. Results for the phase transitions, arc appearance, and arc motion agree qualitatively with previous observations (reported in Part I) 相似文献
15.
16.
Daniel Andre Pierre Figuiere Roger Fourme Michel Ghelfenstein Daniel Labarre Henri Szwarc 《Journal of Physics and Chemistry of Solids》1984,45(3):299-309
The first order phase diagram of thiophene has been determined from 217.5 to 298 K up to 4̃00 MPa. It shows that a high pressure phase which melts at room temperature is in fact Waddington et al.'s atmospheric pressure phase II and discloses a ~R ln2 entropy increment at the II→I phase transition. The structures of phases I and II have accordingly been investigated taking this relationship into account. For phase I, the best result is obtained for space group Cmca with 20 equiprobable molecular orientations. This leads us to assume that phase II is better described by space group Pnma with 10 molecular orientations. Finally, a metastable phase I′ can easily be obtained by cooling phase I at atmospheric pressure. Its unit cell is derived from that of I by multiplying parameter b by 2 and parameter c by 20: this can be considered as an a posteriori justification of the multiple-of-five number of molecular orientations in phases I and II. 相似文献
17.
Poilblanc D 《Physical review letters》2008,100(15):157206
I introduce a doped two-dimensional quantum dimer model describing a doped Mott insulator and retaining the original Fermi statistics of the electrons. This model shows a rich phase diagram including a d-wave hole-pair unconventional superconductor at small enough doping and a bosonic superfluid at large doping. The hole kinetic energy is shown to favor binding of topological defects to the bare fermionic holons turning them into bosons, in agreement with arguments based on resonating valence bond wave function. Results are discussed in the context of cuprate superconductors. 相似文献
18.
S. Mahdavifar 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,77(1):77-82
The ground state magnetic phase diagram of the
one-dimensional quantum compass model (QCM) is studied using the
numerical Lanczos method. A detailed numerical analysis of the low
energy excitation spectrum is presented. The energy gap and the
spin-spin correlation functions are calculated for finite chains.
Two kind of the magnetic long-range orders, the Néel
and a type of the stripe-antiferromagnet, in the ground state
phase diagram are identified. Based on the numerical analysis, the
first and second order quantum phase transitions in the ground
state phase diagram are identified. 相似文献
19.
For part I see DOI: 10.1016/j.physleta.2018.02.006. Size and density dependent quantum oscillations appear in Fermi gases under strong confinement and degeneracy conditions. We provide a universal recipe that explicitly separates oscillatory regime from non-oscillatory (stationary) one. A phase diagram representing stationary and oscillatory regimes on degeneracy-confinement space is proposed. Analytical expressions of phase transition interfaces are derived. The critical point, which separates entirely stationary and oscillatory regions, is determined and its dependencies on aspect ratios are examined for anisometric domains. Accuracy of the half-vicinity model and the phase diagram are verified through the quantum oscillations in electronic heat capacity and its ratio to entropy. 相似文献
20.
Lu Zhao-Xin 《Phase Transitions》2015,88(1):90-100
The phase diagram of a ferroelectric thin film is studied by using the usual mean-field approximation. The crossover features, from the ferroelectric-dominant phase diagram to the paraelectric-dominant phase diagram, for the physical parameters of the thin film are discussed. Special attention is devoted to the investigation of surface and bulk layers, and how to influence the crossover values of exchange interactions and transverse fields. 相似文献