Coupling Phase Diagram Research Articles

Coupled phase diagram study and thermodynamic modeling of the Na2O-B2O3-ZnO system

The Phase diagram of ternary Na2O-B2O3-ZnO system was investigated for the first time using the classical equilibration/quenching method and differential thermal analysis followed by the phase analysis using the Electron Probe Micro-Analysis (EPMA) and X-Ray Diffraction (XRD). The isothermal phase diagrams of this ternary system at 900, 1000 and 1100 °C were determined, and the melting temperatures of two ternary compounds were investigated using Differential Thermal Analysis (DTA). The thermodynamic modeling of ternary Na2O-B2O3-ZnO system was carried out based on the present ternary phase diagram data and the optimized model parameters of binary systems. Thermodynamic models with optimized model parameters were used to predict the phase diagram of the ternary Na2O-B2O3-ZnO system.

Antiferromagnetically ordered topological semimetals in Hubbard model with spin-orbit coupling

We examine the possible existence of Dirac semimetal with magnetic order in a two-dimensional system with a nonsymmorphic symmetry by using the Hartree–Fock mean-field theory within the Hubbard model. We locate the region in the second-neighbor spin–orbit coupling vs Hubbard interaction phase diagram, where such a state is stabilized. The edge states for the ribbons along two orthogonal directions concerning the orientation of in-plane magnetic moments are obtained. Finally, the effect of the in-plane magnetic field, which results in the stabilization of the Weyl semimetallic (WSM) state, and the nature of the edge states corresponding to the WSM state for ribbon geometries are also explored.

Anisotropic exchange coupling and ground state phase diagram of Kitaev compound YbOCl

Rare-earth chalcohalide REChX (RE = rare earth; Ch = O, S, Se, Te; X = F, Cl, Br, I) is a newly reported family of Kitaev spin liquid candidates. The family offers a platform where a strong spin-orbit coupling meets a van der Waals layered and undistorted honeycomb spin lattice, which outputs highly anisotropic exchange couplings required by the Kitaev model. YbOCl is the first single crystal of the family we grew, with a size up to ~ 15 mm. We have performed magnetization and high magnetic field electron spin resonance measurements from 2 to 300 K. We develop the mean-field scenario for the anisotropic spin system, with which we are able to well describe the experiments and reliably determine the fundamental parameters. The self-consistent simulations give the anisotropic spin-exchange interactions of $J_{\pm}$ (~ -0.3 K) and $J_{zz}$ (~ 1.6 K), and g factors of $g_{ab}$ (~ 3.4) and $g_{c}$ (~ 2.9). Based on the spin-exchange interactions, we employ the exact diagonalization method to work out the ground state phase diagram of YbOCl in terms of the off-diagonal exchange couplings. The phase diagram hosting rich magnetic phases including the spin-disordered one, sheds light on the novel magnetic properties of the family, particularly the Kitaev physics.

Trions in twisted bilayer graphene

The strong coupling phase diagram of magic angle twisted bilayer graphene (TBG) predicts a series of exact one particle charge $\pm 1$ gapped excitations on top of the integer-filled ferromagnetic ground-states. Finite-size exact diagonalization studies showed that these are the lowest charge $\pm 1$ excitations in the system (for $10$nm screening length), with the exception of charge $+1$ at filling $-1$ in the chiral limit. In the current paper we show that this "trion bound state", a $3$-particle, charge $1$ excitation of the insulating ferromagnetic ground-state of the projected Hamiltonian of TBG is the lowest charge $+1$ overall excitation at $\nu=-1$, and also for some large ($\approx 20$nm) screening lengths at $\nu=-2$ in the chiral limit and with very small binding energy. At other fillings, we show that trion bound states do exist, but only for momentum ranges that do not cover the entire moir\'e Brillouin zone. The trion bound states (at different momenta) exist for finite parameter range $w_0/w_1$ but they all disappear in the continuum far below the realistic values of $w_0/w_1= 0.8$. We find the conditions for the existence of the trion bound state, a good variational wavefunction for it, and investigate its behavior for different screening lengths, at all integer fillings, on both the electron and hole sides.

Coupled experimental phase diagram study and thermodynamic optimization of the Na2O–B2O3–Fe2O3 system in air

Coupled key phase diagram experiment and thermodynamic optimization of the Na2O–B2O3–Fe2O3 system were carried out. Liquidus in the Na2O–B2O3–Fe2O3 system in air was experimentally determined at 1173, 1273, 1373, and 1473 K using a classical quenching method followed by Electron Probe Micro-Analyzer (EPMA) and X-Ray Diffraction (XRD) phase analysis. Based on the new phase diagram data and available literature data, the thermodynamic optimizations of binary B2O3–Fe2O3 system and ternary Na2O–B2O3–Fe2O3 (Na2O < 50 mol%) system in air were carried out. All the reliable experimental phase diagram data were reproduced within an experimental error limit. Thermodynamic properties and phase diagrams of the ternary Na2O–B2O3–Fe2O3 (Na2O < 50 mol %) in air were predicted from the thermodynamic models with optimized model parameters.

Coupled Thermodynamics and Phase Diagram Analysis of Gas-Duct Concretion Formation in Pyro-Processing Ironmaking and Steelmaking Dust

In recent years, the steel industry has accumulated approximately 100 million tons of dust annually, severely threatening the environment. Rotary kiln technology is one of the main industrial methods used to process this dust. However, some substances in flue gas congeal on the cooling wall of the gas duct and seriously affect production. In this study, the properties and formation mechanisms of the coagulum were investigated on the basis of experimental and thermodynamic analyses. The experimental results showed that the coagulum is mainly composed of chlorides (KCl, NaCl, and ZnCl2), oxides (ZnO, FeO), and carbon, with three structures: lumps, fibers, and particles. Based on a thermodynamic analysis, a reasonable explanation was proposed to clarify the formation mechanism. The liquid phase (a eutectic system of KCl–NaCl–ZnCl2), dendrites (KCl, NaCl), and particles (ZnO, FeO, C) were found to act as binders, stiffeners, and aggregates in the coagulum, respectively, constituting a composite structure. Liquids acting as binders are essential for coagulum formation, and dendrites and particles strengthen this effect. Furthermore, the eutectic system of chlorides plays a crucial role in coagulum formation. The results of the present study offer a theoretical understanding of gas-duct coagulation and will provide guidance for adopting alleviation measures.

Pair correlations in the normal phase of an attractive Fermi gas

In a recent paper (2019 Phys. Rev. A 99, 053617), the total number of fermion pairs in a spin-balanced two-component Fermi gas of 6Li atoms was experimentally probed in the normal phase above the superfluid critical temperature, in order to investigate the sectors of pseudogap and preformed-pair in the temperature–coupling phase diagram. Here, we present a theoretical account of these experimental results in terms of an ab initio self-consistent t-matrix calculation, which emphasizes the role of the pair-correlation function between opposite-spin fermions at equilibrium. Good agreement is found between the available experimental data and the theoretical results obtained with no adjustable parameter.

Coupled Experimental Study and Thermodynamic Modeling of the MgO-MnO-Mn2O3-Ti2O3-TiO2 System

A coupled phase diagram experiment and thermodynamic modeling of the MgO-MnO-Mn2O3-Ti2O3-TiO2 system at 1 bar total pressure is presented. High temperature equilibration and quenching experiments followed by the phase analysis using electron probe microanalysis and X-ray diffraction were performed to obtain complex phase equilibria between solid solutions and liquid phase in air. Low temperature phases during quenching was inevitable in some samples which lead to inaccuracy in the experimental data. The molten oxide phase was described by using the Modified Quasichemical Model, which considers short-range ordering in liquid state, and the Gibbs energies of the extensive solid solutions (pseudobrookite, ilmenite and spinel) were described using the Compound Energy Formalism based on their crystal structures. A set of optimized model parameters of all phases was obtained, which reproduces all the reliable experimental data within experimental error limits from 25 °C to above the liquidus temperatures over the entire range of composition at air atmosphere. The model can also predict the phase equilibria in the range of oxygen partial pressures from metallic saturation to air. The complex phase relationships in the system have been elucidated for the first time and the database of the model parameters can be used with FactSage software to calculate any phase diagrams and thermodynamic properties of the MgO-MnO-Mn2O3-Ti2O3-TiO2 system.

A coupled phase diagram experimental study and thermodynamic optimization of the Li2O-CaO-Al2O3 and Li2O-CaO-SiO2 systems, and prediction of the phase diagrams of the Li2O-CaO-Al2O3-SiO2 system

A coupled experimental phase diagram study and thermodynamic modeling of the Li2O-CaO-Al2O3 and Li2O-CaO-SiO2 systems was conducted at 1 atm total pressure. Differential scanning calorimetry (DSC) measurements were performed in the Li2O-CaO-Al2O3 and Li2O-CaO-SiO2 systems. In addition, the phase relations in the Li2O-CaO-Al2O3 system were determined by equilibration/quenching experiments at 1643 and 1743 K, and the phases were characterized with X-ray diffraction (XRD) and Electron-probe micro analysis-wavelength dispersive spectroscopy (EPMA-WDS). The absence of ternary compounds or solid solutions was confirmed. Congruent melting of Li2CaSiO4 compound in the Li2O-CaO-SiO2 system was determined at 1350 ± 5 K. Thermodynamic optimization of the Li2O-CaO-Al2O3 and Li2O-CaO-SiO2 systems was carried out based on new phase diagram experiments and critically evaluated literature data. The phase diagrams of the quaternary Li2O-CaO-Al2O3-SiO2 system were predicted using the thermodynamic models with optimized model parameters.

Coupled experimental phase diagram study and thermodynamic optimization of the Li2O–MgO–SiO2 system

AbstractA coupled key phase diagram study and critical evaluation and optimization of all available experimental data of the Li2O–MgO–SiO2 system was performed to obtain a set of Gibbs energy functions to reproduce all the reliable phase equilibria and thermodynamic data. Differential scanning calorimetry measurements and equilibration/quenching experiments were performed in the Li2SiO3–MgO and Li4SiO4–Mg2SiO4 sections, respectively, using sealed Pt capsules to prevent the volatile loss of Li. According to the present experimental results, Li2MgSiO4 is the only compound present in the Li4SiO4–Mg2SiO4 isopleth, which shows a peritectic melting at 1465 ± 6°C (1738 ± 6 K). The Modified Quasichemical Model, which considers short‐range ordering in the melt, was employed to describe the thermodynamic properties of the liquid phase. The Li4SiO4–Li2MgSiO4 and Mg2SiO4‐rich solid solutions were modeled using the Compound Energy Formalism.

Coupled experimental phase diagram study and thermodynamic modeling of the Li2O-Na2O-SiO2 system

A coupled experimental phase diagram study and thermodynamic modeling of the Li2O-Na2O-SiO2 system was conducted at 1atm total pressure. Differential scanning calorimetry (DSC) measurements and equilibrium/quenching experiments along the Na2SiO3-Li4SiO4 isopleth were conducted using sealed Pt or Au-Pd crucibles to obtain the phase diagram data in the alkali-rich region. It is found that Li3NaSiO4 is the only compound present in the ternary system. Using all available and reliable phase diagram data in the literature and the present new phase diagram results, the thermodynamic optimization of the Li2O-Na2O-SiO2 system was carried out to obtain a set of Gibbs energy functions for the liquid phase and all solid phases to reproduce the phase equilibria of the present system.

Coupled phase diagram experiments and thermodynamic optimization of the binary Li2O-MgO and Li2O-CaO systems and ternary Li2O-MgO-CaO system

Abstract A key phase diagram study of the Li2O-MgO and Li2O-CaO systems at 1 atm was performed using equilibration/quenching experiments and differential scanning calorimetry measurements with sealed 90Pt-10Rh crucibles. In particular, the eutectic temperatures of both systems and the solubility of Li2O in solid MgO and CaO were properly measured for the first time. The eutectic temperatures of the Li2O-MgO and Li2O-CaO systems were determined to be 1696 ± 6 K (1423 ± 6 °C) and 1617 ± 6 K (1344 ± 6 °C), respectively. A solubility of 2.6 mol% (1.9 wt%) Li2O in solid MgO was measured at 1743 K (1470 °C) and no detectable solubility of Li2O in solid CaO was determined. The present experimental results were employed for the thermodynamic modeling of the binary Li2O-MgO and Li2O-CaO systems. The phase diagrams for the binary Li2O-MgO and Li2O-CaO systems were constructed for the first time, and the phase diagram of the ternary Li2O-MgO-CaO system was predicted from the binary descriptions.

Polarised black holes in ABJM

We numerically construct asymptotically AdS4 solutions to Einstein-Maxwell-dilaton theory. These have a dipolar electrostatic potential turned on at the conformal boundary {S}^2times {mathrm{mathbb{R}}}_t . We find two classes of geometries: AdS soliton solutions that encode the full backreaction of the electric field on the AdS geometry without a horizon, and neutral black holes that are “polarised” by the dipolar potential. For a certain range of the electric field mathrm{mathcal{E}} , we find two distinct branches of the AdS soliton that exist for the same value of mathrm{mathcal{E}} . For the black hole, we find either two or four branches depending on the value of the electric field and horizon temperature. These branches meet at critical values of the electric field and impose a maximum value of mathrm{mathcal{E}} that should be reflected in the dual field theory. For both the soliton and black hole geometries, we study boundary data such as the stress tensor. For the black hole, we also consider horizon observables such as the entropy. At finite temperature, we consider the Gibbs free energy for both phases and determine the phase transition between them. We find that the AdS soliton dominates at low temperature for an electric field up to the maximum value. Using the gauge/gravity duality, we propose that these solutions are dual to deformed ABJM theory and compute the corresponding weak coupling phase diagram.

Modelling of thermodynamic properties of NdBr3–MBr (M=Li–Cs) pseudobinary systems

The phase diagrams of NdBr3–MBr (M=Li…Cs) pseudobinary systems measured by different authors show discrepancies. Therefore in the present work mentioned systems have been re-examined and the compatibility of their phase diagrams have been evaluated. The dependences of mixing enthalpies on NdBr3 mole fraction, heat capacities of M3NdBr6 intermediate compounds (M=Li…Cs) formed in the investigated systems and evaluated phase diagrams have been used for optimization of coupled phase diagrams. The experimental data have been used to predict of an unknown thermodynamic properties of M2NdBr5 and MNd2Br7 (M=Li…Cs) intermediate compounds. The Associate Model of the liquid phase has been applied and the dependence of mixing entropy on NdBr3 mole fraction for the set of the phase diagrams have been found. The amount of the main associate {3M++NdBr63−} in each system has been estimated.

Manipulation of Dy-Mn coupling and ferrielectric phase diagram of DyMn2O5: The effect of Y substitution of Dy

DyMn2O5 is an extraordinary example in the family of multiferroic manganites and it accommodates both the 4f and 3d magnetic ions with strong Dy-Mn (4f-3d) coupling. The electric polarization origin is believed to arise not only from the Mn spin interactions but also from the Dy-Mn coupling. Starting from proposed scenario on ferrielectricity in DyMn2O5 where the exchange-strictions associated with the Mn3+-Mn4+-Mn3+ blocks and Dy3+-Mn4+-Dy3+ blocks generate the two ferroelectric sublattices, we perform a set of characterizations on the structure, magnetism, and electric polarization of Dy1-xYxMn2O5 in order to investigate the roles of Dy-Mn coupling in manipulating the ferrielectricity. It is revealed that the non-magnetic Y substitution of Dy suppresses gradually the Dy3+ spin ordering and the Dy-Mn coupling. Consequently, the ferroelectric sublattice generated by the exchange striction associated with the Dy3+-Mn4+-Dy3+ blocks is destabilized, but the ferroelectric sublattice generated by the exchange striction associated with the Mn3+-Mn4+-Mn3+ blocks remains less perturbed, enabling the ferrielectricity-ferroelectricity transitions with the Y substitution. A phenomenological ferrielectric domain model is suggested to explain the polarization reversal induced by the Y substitution. The present work presents a possible scenario of the multiferroic mechanism in not only DyMn2O5 but probably also other RMn2O5 members with strong 4f-3d coupling.

P-wave pairing in a two-component Fermi system with unequal population: Weak-coupling BCS to strong-coupling BEC regimes

We explore p-wave pairing in a single-channel two-component Fermi system with unequal population near Feshbach resonance. Our analytical and numerical study reveal a rich superfluid (SF) ground state structure as a function of imbalance. In addition to the state $\Delta_{\pm 1} \propto Y_{1\pm 1}$, a multitude of ``mixed'' SF states formed of linear combinations of $Y_{1m}$'s give global energy minimum under a phase stability condition; these states exhibit variation in energy with the relative phase between the constituent gap amplitudes. States with local energy minimum are also obtained. We provide a geometric representation of the states. A $T$=0 polarization vs. p-wave coupling phase diagram is constructed across the BEC-BCS regimes. With increased polarization, the global minimum SF state may undergo a quantum phase transition to the local minimum SF state.

Overview of large N QCD with chemical potential at weak and strong coupling

In this note we summarize the results from a longer article on obtaining the QCD phase diagram as a function of the temperature and chemical potential at large Nc and large Nf in the weak coupling limit λ → 0, and the strong coupling limit λ → ∞. The weak coupling phase diagram is obtained from the Polyakov line order parameter, and the quark number, calculated using 1-loop perturbation theory for QCD formulated on S1 × S3. The strong coupling phase diagram is obtained from the same observables calculated at leading order in the lattice strong coupling and hopping parameter expansions. We show that the matrix models in these two limits agree at temperatures and chemical potentials which are not too high, such that observables in the strongly-coupled theory can be obtained from the observables in the weakly-coupled theory, and vice versa, using a simple transformation of variables.

P-WAVE PAIRING IN FERMI SYSTEMS WITH UNEQUAL POPULATION NEAR FESHBACH RESONANCE

We explore p-wave pairing in a single-channel two-component Fermi system with unequal population near Feshbach resonance. Our analytical and numerical study reveal a rich superfluid (SF) ground state structure as a function of imbalance. In addition to the state Δ±1 ∝ Y1±1, a multitude of “mixed” SF states formed of linear combinations of Y1m's give global energy minimum under a phase stability condition; these states exhibit variation in energy with the relative phase between the constituent gap amplitudes. States with local energy minimum are also obtained. We provide a geometric representation of the states. A T = 0 polarization vs. p-wave coupling phase diagram is constructed across the BEC-BCS regimes. With increased polarization, the global minimum SF state may undergo a quantum phase transition to the local minimum SF state.

𝒩 = 4 SYM onS3with near critical chemical potentials

We study the N = 4 theory at weak coupling, on a three sphere in the grand canonical ensemble with R symmetry chemical potentials. We focus attention on near critical values for the chemical potentials, above which the classical theory has no ground state. By computing a one loop effective potential for the light degrees of freedom in this regime, we show the existence of flat directions of complex dimension N, 2N and 3N for one, two and three critical chemical potentials respectively; these correspond to one half, one quarter and one-eighth BPS states becoming light respectively at the critical values. At small finite temperature we show that the chemical potentials can be continued beyond their classical limiting values to yield a deconfined metastable phase with lifetime diverging in the large N limit. Our low temperaure analysis complements the high temperature metastability found by Yamada and Yaffe. The resulting phase diagram at weak coupling bears a striking resemblance to the strong coupling phase diagram for charged AdS black holes. Our analysis also reveals subtle qualitative differences between the two regimes.

Phase Diagram of Spinless Fermions on an Anisotropic Triangular Lattice at Half-filling

The strong coupling phase diagram of the spinless fermions on the anisotropic triangular lattice at half-filling is presented. The geometry of inter-site Coulomb interactions rules the phase diagram. Unconventional charge ordered phases are detected which are the recently reported pinball liquid and the striped chains. Both are induced by the quantum dynamics out of classical disordered states and afford extremely correlated metallic states and the particular domain wall-type of excitations, respectively. The disorder once killed by the quantum effect revives at the finite temperature, which is discussed in the terms of the organic $\theta$-ET$_2X$.