Proposed Phase Diagram Research Articles

Understanding Ion Distribution and Diffusion in Solid Polymer Electrolytes.

Solid polymer electrolytes (SPEs)─polymer melts with added salts─exhibit ion conduction and high mechanical properties, and are thus promising materials for future energy storage devices. The ion conductivity in an SPE is intricately connected to the salt ion distribution in the polymer matrix. The relationship between ion diffusion and ion distribution in SPEs remains unresolved. Here, we conduct coarse-grained molecular dynamics simulations and establish correlations between ion distribution and transport for a phenomenological SPE model. We propose phase diagrams of SPEs as a function of ion pair size, ion concentration, and the Bjerrum length of the material. A crossover from a discrete ion aggregate to a percolated ion aggregate is demonstrated as a function of ion pair size for low ion concentration in the SPE. The ion diffusion shows a strong correlation with its size, as has been found experimentally. The work provides important design strategies for controlling the ion distribution and enhancing ion conductivity in a polymer matrix.

Where is the Quantum Spin Nematic?

We provide strong evidence of the spin-nematic state in a paradigmatic ferro-antiferromagnetic J_{1}-J_{2} model using analytical and density-matrix renormalization group methods. In zero field, the attraction of spin-flip pairs leads to a first-order transition and no nematic state, while pair repulsion at larger J_{2} stabilizes the nematic phase in a narrow region near the pair-condensation field. A devil's staircase of multipair condensates is conjectured for weak pair attraction. A suppression of the spin-flip gap by many-body effects leads to an order-of-magnitude contraction of the nematic phase compared to naïve expectations. The proposed phase diagram should be broadly valid.

Vacuum arc melted and heat treated AlCoCrFeNiTiX based high-entropy alloys: Thermodynamic and microstructural investigations

The AlCoCrFeNi alloy system is one of the commonly studied high-entropy alloys (HEA). The additional elements like Ti affect the properties of HEAs. In order to predict these effects on the microstructure and the properties of HEAs, a suitable phase diagram is needed. The phase diagrams can be plotted by using thermodynamic software and databases. But experimental studies should be done to control whether this phase diagram is suitable or not. The aim of this study is to propose a phase diagram suitable for the AlCoCrFeNiTiX system by using ThermoCalc software and to compare it with the experimental results. In this work, HEAs were produced by a vacuum arc melting (VAM) method followed by a heat treatment (H-T) process. The stoichiometric amount of Ti was varied-(X = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0). Its effects on the microstructure evaluations and phase transformations in HEAs were investigated. The H-T processes were realized at different temperatures and cooling conditions. The thermodynamic investigations were performed to predict the phases present within as-cast (AC) and heat-treated (HT) HEAs by using Thermo-Calc 2021a Software and its TCHEA4 database. The Calculation of Phase Diagram (CALPHAD) studies were also utilized to plot the phase diagrams for the AlCoCrFeNiTiX system under both equilibrium and non-equilibrium cooling conditions. AC and HT HEAs were characterized by various techniques: scanning electron microscope (SEM) with an energy dispersive spectrometer (EDS), X-ray diffractometer (XRD), differential thermal analysis (DTA), and differential scanning calorimetry (DSC). The phases and the microstructures of AC HEAs were detected as similar to the theoretically obtained alloys under non-equilibrium cooling conditions. While the phases and the microstructures of HT HEAs were detected as similar to the theoretically obtained alloys under equilibrium cooling conditions. As a result, the target alloy composition and production process can be designed depending on the desired properties using the proposed phase diagrams. For example, if the Sigma phase is not desired in the structure, HEAs with Ti1.1 and above contents should be studied.

Thermodynamic investigation of Co–Cr alloys, III: Thermo-analytical measurements using DSC and DTA techniques

Abstract Several Co–Cr alloys have been investigated by Differential Scanning Calorimetry (DSC) as well as by Differential Thermal Analysis (DTA) in the temperature range 298 – 1823 K. The compositional range investigated was from 0 to 87 wt.% Cr with special attention given to alloys with low Cr contents, i. e. 0 to 10 wt.% Cr. From the DSC measurements molar heat capacity values, phase transformation temperatures, enthalpies of transformation and Curie transition temperatures were derived. From the DTA measurements, the melting temperatures and melting enthalpies were evaluated. The trends obtained were compared with the results for pure Co as well as the proposed phase diagram reported in literature.

A computational framework for evaluating the role of mobility on the propagation of epidemics on point processes.

This paper is focused on SIS (Susceptible-Infected-Susceptible) epidemic dynamics (also known as the contact process) on populations modelled by homogeneous Poisson point processes of the Euclidean plane, where the infection rate of a susceptible individual is proportional to the number of infected individuals in a disc around it. The main focus of the paper is a model where points are also subject to some random motion. Conservation equations for moment measures are leveraged to analyze the stationary regime of the point processes of infected and susceptible individuals. A heuristic factorization of the third moment measure is then proposed to obtain simple polynomial equations allowing one to derive closed form approximations for the fraction of infected individuals in the steady state. These polynomial equations also lead to a phase diagram which tentatively delineates the regions of the space of parameters (population density, infection radius, infection and recovery rate, and motion rate) where the epidemic survives and those where there is extinction. A key take-away from this phase diagram is that the extinction of the epidemic is not always aided by a decrease in the motion rate. These results are substantiated by simulations on large two dimensional tori. These simulations show that the polynomial equations accurately predict the fraction of infected individuals when the epidemic survives. The simulations also show that the proposed phase diagram accurately predicts the parameter regions where the mean survival time of the epidemic increases (resp. decreases) with motion rate.

Entropy-Induced Multivalley Band Structures Improve Thermoelectric Performance in p-Cu7P(SxSe1-x)6 Argyrodites.

Searching for novel low-cost and eco-friendly materials for energy conversion is a good way to provide widespread utilization of thermoelectric technologies. Herein, we report the thermal behavior, phase equilibria data, and thermoelectric properties for the promising argyrodite-based Cu7P(SxSe1-x)6 thermoelectrics. Alloying of Cu7PSe6 with Cu7PS6 provides a continuous solid solution over the whole compositional range, as shown in the proposed phase diagram for the Cu7PS6-Cu7PSe6 system. As a member of liquid-like materials, the investigated Cu7P(SxSe1-x)6 solid solutions possess a dramatically low lattice thermal conductivity, as low as ∼0.2-0.3 W m-1 K-1, over the entire temperature range. Engineering the configurational entropy of the material by introducing more elements stabilizes the thermoelectrically beneficial high-symmetry γ-phase and promotes the multivalley electronic structure of the valence band. As a result, a remarkable improvement of the Seebeck coefficient and a reduction of electrical resistivity were observed for the investigated alloys. The combined effect of the extremely low lattice thermal conductivity and enhanced power factor leads to the significant enhancement of the thermoelectric figure of merit ZT up to ∼0.75 at 673 K for the Cu7P(SxSe1-x)6 (x = 0.5) sample with the highest configurational entropy, which is around twice higher compared with the pure selenide and almost four times higher than sulfide. This work not only demonstrates the large potential of Cu7P(SxSe1-x)6 materials for energy conversion but also promotes sulfide argyrodites as earth-abundant and environmentally friendly materials for energy conversion.

Evidence on the quantum critical point in EuTiO3–SrTiO3 solid solution

EuTiO3 (ETO) and SrTiO3 (STO) are the two well-known analogous quantum paralelectric materials. In the present study, we synthesized Eu1-xSrxTiO3 for various values of x (0 < x < 1) by solid state reaction method. X-ray diffraction (XRD) measurement performed on the synthesized samples confirmed the cubic structure with tetragonal distortion for Eu rich samples. The phase purity of the synthesized samples was also confirmed by the X-ray measurements. X-ray photoelectron spectra were measured to show that the valence state of Eu is in 2+ states. The dielectric and magnetic properties of Eu1-xSrxTiO3 samples were systematically studied. The dielectric constant against temperature for pure ETO shows sudden drop at Neel temperature 5.3 K confirming the coupling between electric and magnetic polarization. The magnetization value remains constant below the Neel temperature for ETO and Eu0.8Sr0.2TiO3 samples while others show paramagnetic behavior. The magneto dielectric effect shows a huge value of around 5% at 2 K for ETO and abruptly drops by Sr doping. The proposed phase diagram with the magnetic and dielectric data of Eu1-xSrxTiO3 suggests a quantum critical point around the composition of Eu0.7Sr0.3TiO3.

Analysis of the relief of MCF-7 tumor cells during apoptisis on the basis of phase-contrast images obtained by laser interference microscopy

Data on the surface topography of the cell makes it possible to predict its behavior and is an indicator to assess whether it is in a state of apoptosis, that is, in a state of death due to the activation of intracellular reactions; this state of a cell occurs both during normal development and as a result of a pathological process. A universal method for recording the state of the relief of the cell and its other mechanobiological parameters has not been developed, and therefore laser interference microscopy is promising for this purpose. The aim of this work is to evaluate the state of the surface of tumor cells during the apoptotic changes in breast cancer cells by analyzing the phase contrast (phase) images obtained by laser interference microscopy. The object of the study is the cells of the MCF-7 line (epithelial-like adenocarcinoma of the human mammary gland) in a native state and in a state of induced apoptosis under the action of doxorubicin. The analysis of the cell surface involves interpretation of data on the optical thickness of cells and their morphology through the construction of isolines. Based on the analysis of phase images of cells, their general morphometric parameters were determined. Visualization of optical data and their interpretation was performed using the ImageJ-Fiji software. According to the Wilcoxnon-Mann-Whitney test, the samples under study are significantly different in maximum diameter, perimeter, and sphericity coefficient. Based on the analysis of isolinear images, a diagram of the phase state of cells in a native state and in a state of apoptosis was constructed. According to the diagram, the cross-sectional area of apoptotic cells is generally much smaller than the cross-sectional area of native cells at the same height levels. The characteristics of cells within the framework of the proposed phase diagram are consistent with the morphological cell apoptosis signs, which are recorded using classical microscopic methods. The construction of the diagrams of the state of cells according to the parameters of their relief holds promise for assessing the cellular behavior, predicting it, as well as for analyzing the effect of drugs and therapeutic methods on pathological cells.

Lubricated contact model for numerical simulations of suspensions

Discrete granular models are a natural choice when simulating dense suspensions, when the small distances between the particles lead to dominant contributions by lubrication and contact forces. In such case one can get rid of the costly resolution of Navier-Stokes equations, using closed form expressions for lubrication terms. However, those terms diverge when two hard spheres approach contact, and there are issues when integrating them directly with the finite precision of floating point calculations. In this paper, we introduce a visco-elasto-plastic interaction model for suspended spheres, which combines lubrication and elastic-frictional contact behaviour depending on surface roughness. An integration scheme is proposed for that model. Unlike earlier methods, the scheme enables an unconditionally stable time-integration of the interactions. The case of perfectly smooth spheres (null roughness), namely, is integrated correctly. The theoretical results are well reproduced in benchmark tests on two-sphere systems: one sphere sedimenting on one other and two spheres in a shear flow. From these benchmark tests, we propose phase diagrams showing the interplay between viscosity, roughness and stiffness. The second test case highlights the origin of non-reversibility particle trajectories. It is controlled by the particle roughness for rigid particles, and by the particle deformation when the capillary number is higher than the relative roughness.

Perovskite BiFeO3–BaTiO3 Ferroelectrics: Engineering Properties by Domain Evolution and Thermal Depolarization Modification

AbstractBismuth ferrite (BFO)‐based ceramics with large electromechanical response are important in electronic device applications. To better understand their physical mechanisms, a new phase diagram established by temperature dependence of dielectric properties, temperature dependence of piezoelectric coefficient, and the evolution of their properties is proposed to explain the contribution of piezoelectric and strain response by comparing ferroelectric (FE) and relaxor ferroelectric (RFE) compositions. The FE components with macrodomains have large piezoelectric constant (d33 of 412 pC/N) at high temperature. The RFE components with nanodomains possess giant strain response (Suni = 0.37%) at 180 °C. Combined with in situ and ex situ techniques, the physical mechanisms behind the enhancement of these properties are explored. Macrodomains and multipolar phase coexistence contribute to the piezoelectricity improvement. Nanodomains and an unstable depolarization temperature (Td) region engineer the strain enhancement, which can promote electric‐field‐induced domain switching, lattice strain, and irreversible phase transition. In particular, the Td region of BiFeO3‐based ceramics has been ignored for several years, although it is actually an effective medium to engineer properties. The proposed phase diagram and dynamic model can be used to well understand the structural origins of large electromechanical properties in BFO‐based ceramics, which can give some guidance to explore materials with excellent properties for different applications.

Vacuum structure of bifundamental gauge theories at finite topological angles

We discuss possible vacuum structures of SU(n) × SU(n) gauge theories with bifundamental matters at finite θ angles. In order to give a precise constraint, a mixed ’t Hooft anomaly is studied in detail by gauging the center ℤn one-form symmetry of the bifundamental gauge theory. We propose phase diagrams that are consistent with the con-straints, and also give a heuristic explanation of the result based on the dual superconductor scenario of confinement.

Point defects stabilise cubic Mo-N and Ta-N

We employ ab initio calculations to investigate energetics of point defects in metastable rocksalt cubic Ta-N and Mo-N. Our results reveal a strong tendency to off-stoichiometry, i.e. defected structures are surprisingly predicted to be more stable than perfect ones with metal-to-nitrogen stoichiometry. Despite the similarity of Ta-N and Mo-N systems in exhibiting this unusual behaviour, we also point out their crucial differences. While Ta-N significantly favours metal vacancies, Mo-N exhibits similar energies of formation regardless of the vacancy type (VMo, VN) as long as their concentration is below . The overall lowest energies of formation were obtained for and , which are hence predicted to be the most stable compositions. To account for various experimental conditions during synthesis, we further evaluated the phase stability as a function of chemical potential of individual species. The proposed phase diagrams reveal four stable compositions, , , and , in the case of Mo-N and nine stable compositions in the case of Ta-N indicating the important role of metal under-stoichiometry, since and significantly dominate the diagram. This is particularly important for understanding and designing experiments using non-equilibrium deposition techniques. Finally, we discuss the role of defect ordering and estimate a cubic lattice parameter as a function of defect contents and put them in the context of existing literature theoretical and experimental data.

Tensional acoustomechanical soft metamaterials.

We create acoustomechanical soft metamaterials whose response to uniaxial tensile stressing can be easily tailored by programming acoustic wave inputs, resulting in force versus stretch curves that exhibit distinct monotonic, s-shape, plateau and non-monotonic snapping behaviors. We theoretically demonstrate this unique metamaterial by considering a thin soft material sheet impinged by two counter-propagating ultrasonic wave inputs across its thickness and stretched by an in-plane uniaxial tensile force. We establish a theoretical acoustomechanical model to describe the programmable mechanics of such soft metamaterial, and introduce the first- and second-order tangential stiffness of its force versus stretch curve to boundary different behaviors that appear during deformation. The proposed phase diagrams for the underlying nonlinear mechanics show promising prospects for designing tunable and switchable photonic/phononic crystals and microfluidic devices that harness snap-through instability.

Interface versus bulk gelation and UCST in hydrophobically assembled TX-100 molecular gels

Abstract Herein, we report on a supramolecular TX-100-based molecular gel, which self assembles largely due to hydrophobic interactions, and we clearly distinguish between surface versus bulk gelation mechanism. The phase diagram of these salt-free solutions, and their gels were characterized by dynamic light scattering (DLS), viscometry, rheology, and surface tension methods to map their microstructure, and thermo-viscoelastic properties. We demonstrate the spontaneous evolution of several hierarchical, but self-assembled soft matter phases starting from a homogeneous aqueous solution as it was gradually cooled from 60 °C to room temperature (20 °C). The Cole-Cole plot profile (loss versus storage modulus plot) indicated that this suspension produced the following three phases: (i) for [TX-100] 60% (v/v), heterogeneous melt. The system exhibited a clear UCST separating the sol and gel domains, and the proposed phase diagram embodied all the observed phases. The gelation time, and the free-energy of gelation were determined from surface tension, and viscosity measurements, they revealed that the self-assembly, and network formation at the air-liquid interface occurred at least 200 s later than the bulk, a behaviour that was anomalous. The gelation phenomenon was discussed through homogeneous nucleation and growth model where the interfacial surface and volume free-energy governed the gelation kinetics. The gel state was dominated by structured water (characterized by Raman band at 3200 cm−1), whereas both in the solution, and in the melt phase there was propensity of partially structured water. It was concluded that aqueous TX-100 dispersions can yield a variety of soft matter phases rich in hierarchy, and dynamics, much of which is not probed hitherto.

Phase diagram for passive electromagnetic scatterers.

With the conservation of power, a phase diagram defined by amplitude square and phase of scattering coefficients for each spherical harmonic channel is introduced as a universal map for any passive electromagnetic scatterers. Physically allowable solutions for scattering coefficients in this diagram clearly show power competitions among scattering and absorption. It also illustrates a variety of exotic scattering or absorption phenomena, from resonant scattering, invisible cloaking, to coherent perfect absorber. With electrically small core-shell scatterers as an example, we demonstrate a systematic method to design field-controllable structures based on the allowed trajectories in this diagram. The proposed phase diagram and inverse design can provide tools to design functional electromagnetic devices.

Phase diagram of a non-Abelian Aubry-André-Harper model withp-wave superfluidity

We theoretically study a one-dimensional quasi-periodic Fermi system with topological $p$-wave superfluidity, which can be deduced from a topologically non-trivial tight-binding model on the square lattice in a uniform magnetic field and subject to a non-Abelian gauge field. The system may be regarded a non-Abelian generalization of the well-known Aubry-Andr\'e-Harper model. We investigate its phase diagram as functions of the strength of the quasi-disorder and the amplitude of the $p$-wave order parameter, through a number of numerical investigations, including a multifractal analysis. There are four distinct phases separated by three critical lines, i.e., two phases with all extended wave-functions (I and IV), a topologically trivial phase (II) with all localized wave-functions and a critical phase (III) with all multifractal wave-functions. The phase I is related to the phase IV by duality. It also seems to be related to the phase II by duality. Our proposed phase diagram may be observable in current cold-atom experiments, in view of simulating non-Abelian gauge fields and topological insulators/superfluids with ultracold atoms.

Thermodynamically Consistent p–T Phase Diagram of Boron Oxide B2O3 by in Situ Probing and Thermodynamic Analysis

Although boron oxide B2O3 is an archetypical glass-forming substance of large industrial and fundamental importance, its phase diagram remains controversial. In the present work, the p−T phase diagram of B2O3 has been constructed based on in situ experimental data up to 8 GPa and 1900 K and thermodynamic analysis. In contrast to the previous studies, the proposed phase diagram represents only thermodynamic equilibria (reversible transformations in experiments) between crystalline (α, β) and liquid states, not influenced by kinetic phenomena.

The drag on a vibrated intruder moving in the confined granular media

In this paper, we investigate the drag on an intruder moving in confined granular media based on a discrete element method when its self-induced vibration perpendicular to its moving direction occurs. The influence of vibrating parameters on its dynamical properties is mainly considered. With the enhancing intruder's vibration, we find that the dependence of drag force on its moving velocity exhibits different regimes and then a dimensionless acceleration is proposed as a more intrinsic vibrating parameter determining the drag-velocity relationship, which gradually changes from quadratic to linear with the increase of dimensionless acceleration. The criticality of this parameter is also discussed based on a proposed phase diagram. Finally, our simulating results suggest that, once the dimensionless acceleration exceeds its critical value from below, the evolution of force chains near the intruder exhibits a similar feature, which may account for a stable linear dependence of the drag force on its velocity.

Phase diagrams of forced magnetic reconnection in Taylor’s model

Recent progress in the understanding of how externally driven magnetic reconnection evolves is organized in terms of parameter space diagrams. These diagrams are constructed using four pivotal dimensionless parameters: the Lundquist number $S$, the magnetic Prandtl number $P_{m}$, the amplitude of the boundary perturbation $\hat{{\it\Psi}}_{0}$, and the perturbation wave number $\hat{k}$. This new representation highlights the parameter regions of a given system in which the magnetic reconnection process is expected to be distinguished by a specific evolution. Contrary to previously proposed phase diagrams, the diagrams introduced here take into account the dynamical evolution of the reconnection process and are able to predict slow or fast reconnection regimes for the same values of $S$ and $P_{m}$, depending on the parameters that characterize the external drive, which have not been considered until now. These features are crucial to understanding the onset and evolution of magnetic reconnection in diverse physical systems.

Thermal properties and structure of zinc–manganese metaphosphate glasses

The thermal properties and some physical characteristics of the metaphosphate glassy system xMnO–(50−x)ZnO–50P2O5 were studied. Homogeneous glasses were obtained in the whole concentration range between Zn(PO3)2 and Mn(PO3)2. The metaphosphate structure of the glasses was confirmed by Raman spectroscopy. The manganese was found to have a high-spin d5-configuration in the glassy network, i.e., Mn(II), and the presence of a small amount of Mn(III) explained the purple color of the glasses, as confirmed by electron absorption spectroscopy. Thermoanalytical properties were studied by differential scanning calorimetry, thermomechanical analysis and differential thermal analysis. The phase diagram of the zinc–manganese metaphosphate system was proposed based on thermal analysis results and X-ray diffraction analysis of crystalline phases obtained after crystallization of undercooled melt. An eutectic composition was found close to 8 mol% MnO, while compositions with MnO content over 15 mol% form substitutional solid solutions. Some other properties as compositional dependence of glass transition temperature, thermal expansion coefficient and density were discussed on the basis of proposed phase diagram.