Thermal Phase Diagram Research Articles

Mean field study of the mixed Ising model in a random crystal field

The magnetic properties of a mixed Ising ferrimagnetic system, in which the two interacting sublattices have spins σ , ( ± 1 / 2 ) and spins S , ( ± 1 , 0 ) in the presence of a random crystal field, have been studied with the mean field approach. The obtained results show the existence of some interesting phenomena, such as the appearance of a new ferrimagnetic phase, namely, partly ferrimagnetic phase ( m σ = 1 2 , m S = − 1 2 ) and consequently the existence of four topologically different types of phase diagrams. Furthermore, compensation behaviour and re-entrant phenomenon are found for appropriate ranges of crystal field. Thermal magnetization behaviour and phase diagrams have been discussed in detail.

Phases ofN=∞QCD-like gauge theories onS3×S1and nonperturbative orbifold-orientifold equivalences

We study the phase diagrams of $N=\ensuremath{\infty}$ vectorlike, asymptotically free gauge theories as a function of volume, on ${S}^{3}\ifmmode\times\else\texttimes\fi{}{S}^{1}$. The theories of interest are the ones with fermions in two index representations [adjoint, (anti)symmetric, and bifundamental abbreviated as QCD(adj), QCD(AS/S), and QCD(BF)], and are interrelated via orbifold or orientifold projections. The phase diagrams reveal interesting phenomena such as disentangled realizations of chiral and center symmetry, confinement without chiral symmetry breaking, zero temperature chiral transitions, and in some cases, exotic phases which spontaneously break the discrete symmetries such as $C$, $P$, $T$ as well as $CPT$. In a regime where the theories are perturbative, the deconfinement temperature in SYM, and QCD(AS/S/BF) coincide. The thermal phase diagrams of thermal orbifold QCD(BF), orientifold QCD(AS/S), and $\mathcal{N}=1$ SYM coincide, provided charge conjugation symmetry for QCD(AS/S) and ${\mathbb{Z}}_{2}$ interchange symmetry of the QCD(BF) are not broken in the phase continuously connected to the ${\mathbb{R}}^{4}$ limit. When the ${S}^{1}$ circle is endowed with periodic boundary conditions, the (nonthermal) phase diagrams of orbifold and orientifold QCD are still the same, however, both theories possess chirally symmetric phases which are absent in $\mathcal{N}=1$ SYM. The match and mismatch of the phase diagrams depending on the spin structure of fermions along the ${S}^{1}$ circle is naturally explained in terms of the necessary and sufficient symmetry realization conditions which determine the validity of the nonperturbative orbifold-orientifold equivalence.

Thermal, Conductivity, NMR, and Raman Spectroscopic Measurements and Phase Diagram of the Cs2S2O7−CsHSO4 System

The conductivity of the binary system Cs2S2O7−CsHSO4 has been measured at 20 different molten compositions in the full composition range and in the temperature range 430−750 K. From the obtained liquidus−solidus phase transition temperatures, the phase diagram has been constructed. It is of the simple eutectic type with the composition X(CsHSO4) = 0.86 and temperature of fusion of 470 K for the eutectic. The previously unpublished temperature of fusion of CsHSO4 was found to be 491.7 K. The experimental phase diagram is in good accordance with a calculated diagram based on measured thermodynamic properties of the pure compounds and the heat of liquid−liquid mixing measured for X(CsHSO4) = 0.5 and 1.0. 133Cs and 17O NMR spectra and Raman spectra of the liquid Cs2S2O7−CsHSO4 system indicate the presence of a temperature sensitive equilibrium 2HSO4- ⇌ S2O72- + H2O where the water molecules are strongly associated in the melt. Fast exchange reactions take place between the species present, leading to the observed 17O NMR single line with an averaged chemical shift. Super-ionic and thermodynamic stable phases and the temperatures of phase transitions have been identified from the NMR measurements on CsHSO4, Cs2S2O7, and Cs2S2O7−CsHSO4 mixtures. For 11 selected compositions covering the entire composition range of the Cs2S2O7−CsHSO4 binary system, the conductivity of the molten state has been expressed by equations 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 is the initial mol fraction of CsHSO4.

Theoretical study of phase transition in type II superconductors with Pauli paramagnetic effect in high magnetic field

High-field phase diagram of type II superconductors with paramagnetic depairing effect is examined through a theoretical argument and a numerical simulation of a Ginzburg–Landau model with a negative quartic term. Our results strongly suggest, contrary to the argument based on magnetization data in CeCoIn 5, that the first-order transition at H c2( T) in the mean field (MF) approximation is reflected in real systems merely as a crossover and that the thermal phase diagram is similar to that in the ordinary case where the MF transition is of second order.

Relationship between the Crystallographic Structure of Electrodeposited Fe-P Alloy Film and its Thermal Equilibrium Phase Diagram

The crystallographic structures and surface morphologies of Fe–P binary alloy films electrodeposited at different bath concentrations and different electrodeposition conditions have been studied in detail by means of XRD, HRTEM and SEM. The crystallization sequences of deposited films under the heat-treatment were analyzed with the help of XRD. The crystallographic structures of Fe–P deposited films were also compared with the Fe–P thermal equilibrium phase diagram. The results indicate that the crystallographic structures of Fe–P deposited films gradually change from crystalline to amorphous phase with increasing P content in the deposited films. The deposited film exists as α-Fe supersaturated solid solution when the P compositions in deposited film are below 20.5 at%, whereas it exists as a homogenous amorphous phase when the P compositions in the deposited films are from 22.2 at% to 30.1 at%. Accordingly, the composition of boundary between the crystalline and homogenous amorphous regions can be determined at about 21.4 at% P content.

Thermal phase diagrams of columnar liquid crystals

In order to understand the possible sequence of transitions from the disordered columnar phase to the helical phase in hexa(hexylthio)triphenylene (HHTT), we study a three-dimensional planar model with octupolar interactions inscribed on a triangular lattice of columns. We obtain thermal phase diagrams using a mean-field approximation and Monte Carlo simulations. These two approaches give similar results, namely, in the quasi one-dimensional regime, as the temperature is lowered, the columns order with a linear polarization, whereas helical phases develop at lower temperatures. The helicity patterns of the helical phases are determined by the exact nature of the frustration in the system, itself related to the octupolar nature of the molecules.

Solid–vapor phase boundary of carbon at low temperature and low pressure

We have investigated the thermal equilibrium phase diagram of carbon in a condition of low temperature and low pressure which is relevant to diamond film growth from vapor phase. All the molecules in a chamber of a finite volume are assumed to be fully activated and decomposed into single atoms so that the system may be considered as a mixture of carbon vapor and atomic hydrogen gas equilibrated with a solid phase of carbon. By calculating the carbon chemical potentials for both solid and gas phase, sublimation curve in the presence of partial pressure of atomic hydrogen gas has been obtained. The phase boundary of the equilibrium vapor pressure turns out to be a lower limit of recent many studies on diamond film growth by chemical vapor deposition method.

Cu1—xAgxInSe2 Solid Solutions

CuInSe 2 , AgInSe 2 , ternary compounds and Cu 1-x Ag x InSe 2 solid solutions were synthesized by one-temperature method. The composition and structure of indicated materials were established by chemical and X-ray analysis methods, lattice constants, values of σ positional parameter and bond lengths were also calculated. Temperatures of phase transformations were determined by differential thermal analysis (DTA) method and phase diagram of AgInSe 2 -CuInSe 2 system was built which is characterized by small crystallization interval and presence of solid state transformations throughout the concentration interval.

Cu1xAgxInSe2 Solid Solutions

CuInSe2, AgInSe2, ternary compounds and Cu1—xAgxInSe2 solid solutions were synthesized by one-temperature method. The composition and structure of indicated materials were established by chemical and X-ray analysis methods, lattice constants, values of σ positional parameter and bond lengths were also calculated. Temperatures of phase transformations were determined by differential thermal analysis (DTA) method and phase diagram of AgInSe2-CuInSe2 system was built which is characterized by small crystallization interval and presence of solid state transformations throughout the concentration interval.

Thermal phase diagram of a model Hamiltonian for columnar phases of liquid crystals

We present the phase diagram and critical properties of a coupled $XY$-Ising model on a triangular lattice using the mean-field approximation, the Migdal-Kadanoff scheme of renormalization group and Monte-Carlo simulations. The topology of the phase diagram is similar for the three techniques, with the appearance of a phase with $XY$ order and Ising disorder. The results suggest a line of transitions belonging to the 2D-Ising universality class in contrast with previous data indicating a new universality class. This model is relevant to the columnar phases of discotic liquid crystals [such as hexa(hexylthio)triphenylene (HHTT)] in the limit of weak intercolumn coupling.

Small concentrations of alamethicin induce a cubic phase in bulk phosphatidylethanolamine mixtures

Under normal conditions, excess water dispersions of liquid crystalline 1,2-dielaidoyl- sn-glycero-3-phosphoethanolamine (DEPE) are known to convert from a liquid crystalline lamellar (L α) to inverse hexagonal (H II) phase at about 60°C. The nonlamellar phase behavior of lipid systems is also known to depend on the monolayer spontaneous curvature. The single-channel activity of alamethicin in black lipid bilayer membranes has been shown to be dependent upon the lipid composition of the membrane. Since the monolayer spontaneous curvature properties (e.g., the monolayer spontaneous curvature, curvature coefficients and bilayer thickness) vary with lipid composition, the single-channel activity of alamethicin presumably also correlates with the monolayer spontaneous curvature properties. Accordingly, we reasoned that if alamethicin couples to the curvature properties of a lipid film, then the curvature properties must, in turn, be perturbed by the presence of alamethicin and that this perturbation should be observable in the lipid phase behavior. Here X-ray diffraction and NMR are used to show that the presence of as little as 1% alamethicin introduces a large region of cubic phase into the thermal phase diagram. This suggests that perturbation of the nonlamellar phase behavior of a lipid system may be a method to survey different channel-forming molecules for possible behavior that indicates that the ion channel is sensitive to the monolayer spontaneous curvature properties.

Thermal behaviour and phase diagram for the RDX/NQ binary system

The phase diagram and thermal decomposition for binary mixtures of cyclotrimethylenetrinitramine (RDX) and nitroguanidine (NQ) were investigated by DSC and using a microscope with a heat stage (MHS). The eutectic compositions of the RDX/NQ binary system were obained by constructing a special phase diagram for the relation of the apparent fusion heat with the composition. The DSC results were confirmed by the phase diagram of liquidus temperature vs. composition constructed from MHS data.

Thermal phase transition in mixed action SU (3) lattice gauge theory and Wilson fermion thermodynamics

Abstract We study the thermal phase diagram of pure SU(3) lattice gauge theory with fundamental and adjoint couplings. We improve previous estimates of the position of the bulk transition line and determine the thermal deconfinement transition lines for N t = 2, 4, 6, and 8. The endpoint of the bulk transition line ( β f , β a ) = (4.00(7), 2.06(8)) improves upon earlier estimates obtained using smaller lattice sizes. For N t > 4 the deconfinement transition line splits cleanly away from the bulk transition line. With increasing N t the thermal deconfinement transition lines shift to increasingly weaker coupling, joining onto the bulk transition line at increasingly larger β a in a pattern consistent with the usual universality picture of lattice gauge theories. We also discuss the possible consequences of an induced adjoint term from the fermionic determinant and determine this induced term numerically with a microcanonical demon method for two flavors of dynamical Wilson fermions.

SU(3) lattice gauge theory with adjoint action at nonzero temperature

We study the thermal phase diagram of pure SU(3) gauge theory with fundamental and adjoint couplings. We improve previous estimates of the position of the bulk transition line and determine the thermal deconfinement transition lines for N t = 2, 4, 6, and 8. For N t > 4 the deconfinement transition line splits cleanly away from the bulk transition line. With increasing N t the thermal deconfinement transition lines shift to increasingly weaker coupling, joining onto the bulk transition line at increasingly larger β a in a pattern consistent with the usual universality picture of lattice gauge theories.

Phase segregation in blends of linear with branched polyethylene: the effect of varying the molecular weight of the linear polymer

This paper reports investigations into the phase behaviour of six blend systems containing linear with branched polyethylenes. Five systems used linear polyethylenes of differing molecular weight blended with the same branched polyethylene. The sixth system involved a branched polyethylene of lower branch content and shorter branches. The main experimental methods used were differential scanning calorimetry and transmission electron microscopy. Very good agreement was found between results obtained from both experimental methods. The phase diagrams deduced are of the same general form, all but one showing liquid-liquid phase separation in the melt with both upper and lower critical temperatures. This phase separation is most extensive where the molecular weight of the linear polymer is highest. At the other extreme, for a linear component of molecular weight of 2155, no liquid-liquid phase separation is observed. Of the two branched polyethylenes, that with the higher branch content is more prone to phase separation. These results lead us to conclude that the phase diagram found previously for a similar blend pair is not unique since the various systems studied here all give similar thermal results, morphologies and phase diagrams.

Monte Carlo calculation of thermal desorption spectra: Application to CO/Ru(001)

The thermal desorption spectrum and phase diagram for the triangular lattice gas model with strong repulsive 1NN and weak attractive 2NN interaction are calculated using Monte Carlo method and the transition state rate theory. Starting from an extreme case of the hard hexagon model, the magnitudes of the interactions are varied to reach a good coincidence with the experimental desorption spectrum of CO/Ru(001). The calculated spectrum describes well the characteristic zero-order (-like) behavior and asymmetric sharp peak observed in experiment, which are known to arise from the critical point in the model. Also, calculation of the phase diagram confirms that the tricritical temperature appears in the same magnitude with the 2NN interaction, kT t ≈ ¦ϵ 2¦. The determined 1NN and 2NN interaction energies, ϵ 1 ≈ 8 to 10 kJ mol , ϵ 2 ≈ −1.6 to −1.2 kJ mol , are about t than those estimated previously by the isosteric Arrhenius analysis of the experimental desorption spectrum.

Thermal conductivity, heat capacity and phase diagram of cyclooctanol in liquid, solid and glassy crystal states under high pressure

Using the transient hot-wire method, thermal conductivity and heat capacity per unit volume are measured for solid and liquid phases and glassy crystal states of cyclooctanol, and information is provided on the phase diagram under high pressure. A new solid phase (III) is detected and characterized as a normal crystal phase, whereas all other solid phases (I, II, IV, V) are characterized as plastic crystal phases. We find evidence that the plastic crystal phases I, II and IV could each be the source for a distinct glassy crystal state. It is argued for phase II that its possession of both a low thermal conductivity and a low dielectric permittivity could be accounted for by assuming restricted reorientational motion of the molecules. The unusual (although small) decrease of thermal conductivity observed through the glassy to plastic crystal transitions may indicate that phonons can couple to reorientational motion in the plastic crystal phases I, II and IV.

金属材料へのイオン注入

Ion implantation is a unique technique for creating non-equilibrium phase surfaces or films, since atomic injection and atomic mixing can be effected at low temperatures without the restrictions of thermal diffusion or equilibrium phase diagrams. In this report we describe how ion implantation, including ion irradiation, can modify the microstructures of metals and synthesize specific structures such as metastable precipitates, amorphous phases, and quasicrystal phases. The application of ion implantation to surface and film modification to control the physical and chemical properties of the materials is also reviewd.

Role of decomposition products in the thermal phase diagram behavior of dibenzoyl peroxide single crystals

Role of decomposition products in the thermal phase diagram behavior of dibenzoyl peroxide single crystals

Effects of supercooling in the initial solidification of PbTe-SnTe solid solutions

Deviations from compositions anticipated by the thermal equilibrium phase diagram have been observed in Bridgman-grown crystals of Pb 1− x Sn x Te, in the first to freeze region of the boule. A set of experiments were conducted to determine the extent of thermal supercooling of Pb 1− x Sn x Te in a Bridgman-like configuration. The results of the compositional profiles and the supercooling measurements are consistent with a diffusionless transformation occurring at the onset of solidification and the length of uncontrolled growth is inversely related to the temperature gradient of the furnace.