Absence Of Phase Transition Research Articles

Improving rechargeable magnesium batteries through dual cation co-intercalation strategy

The development of competitive rechargeable Mg batteries is hindered by the poor mobility of divalent Mg ions in cathode host materials. In this work, we explore the dual cation co-intercalation strategy to mitigate the sluggishness of Mg2+ in model TiS2 material. The strategy involves pairing Mg2+ with Li+ or Na+ in dual-salt electrolytes in order to exploit the faster mobility of the latter with the aim to reach better electrochemical performance. A combination of experiments and theoretical calculations details the charge storage and redox mechanism of co-intercalating cationic charge carriers. Comparative evaluation reveals that the redox activity of Mg2+ can be improved significantly with the help of the dual cation co-intercalation strategy, although the ionic radius of the accompanying monovalent ion plays a critical role on the viability of the strategy. More specifically, a significantly higher Mg2+ quantity intercalates with Li+ than with Na+ in TiS2. The reason being the absence of phase transition in the former case, which enables improved Mg2+ storage. Our results highlight dual cation co-intercalation strategy as an alternative approach to improve the electrochemical performance of rechargeable Mg batteries by opening the pathway to a rich playground of advanced cathode materials for multivalent battery applications.

Large Deviation Principle for Random Permutations

Abstract We derive a large deviation principle for random permutations induced by probability measures of the unit square, called permutons. These permutations are called $\mu $-random permutations. We also introduce and study a new general class of models of random permutations, called Gibbs permutation models, which combines and generalizes $\mu $-random permutations and the celebrated Mallows model for permutations. Most of our results hold in the general setting of Gibbs permutation models. We apply the tools that we develop to the case of $\mu $-random permutations conditioned to have an atypical proportion of patterns. Several results are made more concrete in the specific case of inversions. For instance, we prove the existence of at least one phase transition for a generalized version of the Mallows model where the base measure is non-uniform. This is in contrast with the results of Starr (2009, 2018) on the (standard) Mallows model, where the absence of phase transition, that is, phase uniqueness, was proven. Our results naturally lead us to investigate a new notion of permutons, called conditionally constant permutons, which generalizes both pattern-avoiding and pattern-packing permutons. We describe some properties of conditionally constant permutons with respect to inversions. The study of conditionally constant permutons for general patterns seems to be a new challenging problem.

Absence of phase transition in random language model

The random language model, proposed as a simple model of human languages, is defined by the averaged model of a probabilistic context-free grammar. This grammar expresses the process of sentence generation as a tree graph with nodes having symbols as variables. Previous studies proposed that a phase transition, which can be considered to represent the emergence of order in language, occurs in the random language model. We discuss theoretically that the analysis of the ``order parameter'' introduced in previous studies can be reduced to solving the maximum eigenvector of the transition probability matrix determined by a grammar. This helps analyze the distribution of a quantity determining the behavior of the order parameter and reveals that no phase transition occurs. Our results suggest the need to study a more complex model such as a probabilistic context-sensitive grammar, in order for phase transitions to occur.

Mechanical and thermal properties of RETaO4 (RE = Yb, Lu, Sc) ceramics with monoclinic-prime phase

As candidate thermal/environmental barrier coatings (T/EBCs), the structure characteristics and comprehensive properties of monoclinic-prime (m') RETaO4 (RE = Yb, Lu, Sc) with excellent Al2O3/SiO2 chemical compatibility are studied. Excellent thermal insulation protection will be provided by m'RETaO4 due to their low thermal conductivity (∼1.6 W m−1 K−1, 900 °C) and prominent thermal radiation resistance, which is much better than those of YSZ (∼2.5 W m−1 K−1, 1000 °C) and La2Zr2O7 (∼2.0 W m−1 K−1, 900 °C). The thermal expansion coefficients (TECs) are 3.0–8.0 × 10-6 K−1 (200−1200 °C), which is suitable for T/EBCs applications. Furthermore, absence of phase transition and extraordinary chemical compatibility with Al2O3/SiO2 up to 1500 °C indicate the potential application prospect. The documented governing mechanisms of m'RETaO4 properties will enable researchers to promote their application in the future investigation.

Thermodynamics of a Hierarchical Mixture of Cubes

We investigate a toy model for phase transitions in mixtures of incompressible droplets. The model consists of non-overlapping hypercubes in {mathbb {Z}}^d of sidelengths 2^j, jin {mathbb {N}}_0. Cubes belong to an admissible set {mathbb {B}} such that if two cubes overlap, then one is contained in the other. Cubes of sidelength 2^j have activity z_j and density rho _j. We prove explicit formulas for the pressure and entropy, prove a van-der-Waals type equation of state, and invert the density-activity relations. In addition we explore phase transitions for parameter-dependent activities z_j(mu ) = exp ( 2^{dj} mu - E_j). We prove a sufficient criterion for absence of phase transition, show that constant energies E_jequiv lambda lead to a continuous phase transition, and prove a necessary and sufficient condition for the existence of a first-order phase transition.

Facile preparation of Zn-doped hematite thin film as photocathode for solar hydrogen generation

A simple and cost-effective fabrication of the Zn-doped α-Fe2O3 thin film as a photocathode for solar hydrogen generation was proposed in this study. Transparent Zn-doped α-Fe2O3 films were prepared by a spin-coating process using nontoxic iron chloride as the iron precursor and zinc chloride as an acceptor dopant, and the thermal treatment at 550 °C in air subsequently followed up. X-ray diffraction and Raman spectroscopic characterizations suggest the α-phase to the Zn-doped hematite film, indicating that the incorporation of Zn into the Fe2O3 host lattice is carried out in the absence of phase transition. X-ray photoelectron spectroscopic study otherwise demonstrates the substitution of Fe3+ for Zn2+ in the Zn-doped α-Fe2O3 specimens. Mott-Schottky analysis shows that the Zn dopant functions as the hole acceptor and the carrier density is dictated by the concentration of the zinc precursor. Significantly, a notable cathodic photocurrent of −0.1 mA cm−2 is delivered by the Zn-doped α-Fe2O3 photocathode with a doping level of 10% in the photoelectrochemical measurement. Last but not least, the doping effect on the photo-activity of hematite is systematically investigated that in turn works as the blueprint for materials design in the solar application.

Structures of liquid selenium at high pressures

Ab initio molecular dynamics simulation in the framework of the density functional theory is applied for investigation of selenium in the region of the liquid–liquid phase transition. The usability of the method for the problem is examined. Thermodynamic, structural and electronic properties are investigated. The phase transition is not observed on phase diagram, and probably could not be. The structure and electronic analysis suggests that all points may belong to one phase. The absence of phase transition can be result of underestimation of atom attraction that is typical for the exchange-correlation functional chosen.

The crystal structure of sopcheite, Ag4Pd3Te4, from the Lukkulaisvaara intrusion, Karelia, Russia

The crystal structure of sopcheite, Ag 4 Pd 3 Te 4 , has been solved using single-crystal diffraction data for a crystal from the Lukkulaisvaara intrusion, Karelia. The crystal structure is orthorhombic, space group Cmca , a = 12.212(2) A, b = 6.138(2) A, c = 12.234(3) A, V = 917.1(4) A 3 and Z = 4. The refinement of the fully anisotropic model led to an R index of 6.47% for 413 unique reflections. Sopcheite crystallizes in a layered structure. The Pd(1) and Pd(2) atoms assume a nearly planar coordination by four Te atoms. Each of the [PdTe 4 ] rectangles shares two opposite Te–Te edges with adjacent rectangles forming six-membered rings with the shape of elongated hexagons. These hexagons are oriented parallel to (100) and form layers of a herringbone pattern. Silver atoms form four-membered rings [Ag 4 ] of almost square shape. The [Ag 4 ] rings are located approximately in the centre of elongated hexagons composed of [PdTe 4 ] rectangles. The crystal structure is stabilised by a number of metal–metal interactions. The crystal structure of the synthetic phase Ag 4 Pd 3 Te 4 was also determined by single-crystal X-ray diffraction (XRD). It corresponds to the structure of sopcheite from the Lukkulaisvaara intrusion. Electron backscatter diffraction data obtained on material from other reported sopcheite occurrences are entirely consistent with this structure model, which is however incompatible with the sole powder XRD pattern reported so far for sopcheite. Combined with the absence of phase transition in Ag 4 Pd 3 Te 4 up to its breakdown temperature, these results imply revision of the previously published crystallographic data of sopcheite.

Thermodynamical structure of AdS black holes in massive gravity with stringy gauge-gravity corrections

Motivated by gauge/gravity group in the low energy effective theory of the heterotic string theory and novel aspects of massive gravity in the context of lattice physics, the minimal coupling of Gauss–Bonnet-massive gravity with Born–Infeld electrodynamics is considered. At first, the metric function is calculated and then the geometrical properties of the solutions are investigated. It is found that there is an essential singularity at the origin and the intrinsic curvature is regular elsewhere. In addition, the effects of massive parameters are studied and black hole solutions with multi horizons are found in this gravity. Also, the conserved and thermodynamic quantities are calculated, and it is shown that the solutions satisfy the first law of thermodynamics. Furthermore, using heat capacity of these black holes, thermal stability and phase transitions are investigated. The variation of different parameters and related modifications on the (number of) phase transition are examined. Next, the critical behavior of the Gauss–Bonnet–Born–Infeld-massive black holes in the context of extended phase space is studied. It is shown how the variation of the different parameters affects the existence and absence of phase transition. Also, it is found that for specific values of different parameters, these black holes may enjoy the existence of a new type of phase transition which to our knowledge was not observed in black hole physics before.

75As-NQR study of the hybridization gap semiconductor CeOs4As12

We performed an 75As nuclear quadrupole resonance (NQR) measurement on CeOs4As12. The 75As-NQR spectrum shape demonstrates that the Ce-site filling fraction of our high-pressure synthesized sample is close to unity. A presence of the c — f hybridization gap is confirmed from the temperature dependence of the nuclear spin-lattice relaxation rate 1/T1. An increase of 1/T1 below ∼3 K indicates a development of the spin fluctuations. The 1/T1 for CeOs4As12 shows similar behavior as that for CeOs4Sb12 with different magnitude of the c — f hybridization gap. An absence of phase transition in CeOs4As12 may be caused by the increase of the c — f hybridization, which increases the gap magnitude and reduces the residual density of state inside the gap.

Neutron Reflectometry Studies Define Prion Protein N-terminal Peptide Membrane Binding

The prion protein (PrP), widely recognized to misfold into the causative agent of the transmissible spongiform encephalopathies, has previously been shown to bind to lipid membranes with binding influenced by both membrane composition and pH. Aside from the misfolding events associated with prion pathogenesis, PrP can undergo various posttranslational modifications, including internal cleavage events. Alpha- and beta-cleavage of PrP produces two N-terminal fragments, N1 and N2, respectively, which interact specifically with negatively charged phospholipids at low pH. Our previous work probing N1 and N2 interactions with supported bilayers raised the possibility that the peptides could insert deeply with minimal disruption. In the current study we aimed to refine the binding parameters of these peptides with lipid bilayers. To this end, we used neutron reflectometry to define the structural details of this interaction in combination with quartz crystal microbalance interrogation. Neutron reflectometry confirmed that peptides equivalent to N1 and N2 insert into the interstitial space between the phospholipid headgroups but do not penetrate into the acyl tail region. In accord with our previous studies, interaction was stronger for the N1 fragment than for the N2, with more peptide bound per lipid. Neutron reflectometry analysis also detected lengthening of the lipid acyl tails, with a concurrent decrease in lipid area. This was most evident for the N1 peptide and suggests an induction of increased lipid order in the absence of phase transition. These observations stand in clear contrast to the findings of analogous studies of Ab and α-synuclein and thereby support the possibility of a functional role for such N-terminal fragment-membrane interactions.

Flux-Grown Piezoelectric Materials: Application to α-Quartz Analogues

Using the slow-cooling method in selected MoO3-based fluxes, single-crystals of GeO2 and GaPO4 materials with an α-quartz-like structure were grown at high temperatures (T ≥ 950 °C). These piezoelectric materials were obtained in millimeter-size as well-faceted, visually colorless and transparent crystals. Compared to crystals grown by hydrothermal methods, infrared and Raman measurements revealed flux-grown samples without significant hydroxyl group contamination and thermal analyses demonstrated a total reversibility of the α-quartz ↔ β-cristobalite phase transition for GaPO4 and an absence of phase transition before melting for α-GeO2. The elastic constants CIJ (with I, J indices from 1 to 6) of these flux-grown piezoelectric crystals were experimentally determined at room and high temperatures. The ambient results for as-grown α-GaPO4 were in good agreement with those obtained from hydrothermally-grown samples and the two longitudinal elastic constants measured versus temperature up to 850 °C showed a monotonous evolution. The extraction of the ambient piezoelectric stress contribution e11 from the CD11 to CE11 difference gave for the piezoelectric strain coefficient d11 of flux-grown α-GeO2 crystal a value of 5.7(2) pC/N, which is more than twice that of α-quartz. As the α-quartz structure of GeO2 remained stable up to melting, a piezoelectric activity was observed up to 1000 °C.

Absence of phase transition in the XY-model on Menger sponge

We have performed a Monte Carlo study of the classical XY-model on a Menger sponge with the Wolff cluster algorithm (U. Wolff, 1989). The Menger sponge is a fractal object with infinite order of ramification and fractal dimension D=log(20)/log(3)=2.7268. From the dependence of the helicity modulus on system size and on boundary conditions, we conclude that there is no phase transition in the system at any finite temperature.

Phase stability of the two isomorphs monoclinic zirconia and hafnia under MeV ion irradiation

Zirconia and hafnia are known to exhibit similar phase transitions under temperature, pressure or swift heavy (i.e., GeV) ion irradiation. In the present study, both monoclinic zirconia and hafnia were irradiated with 5-MeV I ions in order to comprehend the underlying mechanism governing phase transition by low-energy ion irradiation. Surprisingly, it was found that, although monoclinic zirconia can easily transform to the tetragonal phase, monoclinic hafnia does not show any transition to the tetragonal structure even after irradiation with ∼19 displacements per atom. The absence of this phase transition in hafnia and its presence in zirconia clearly break the parallel between these two oxides in their response to intense excitation. Furthermore, this comparative study allowed severe constraints to be imposed on the possible mechanisms aimed at explaining phase transformation by low-energy ion irradiation. It is found that the monoclinic-to-tetragonal phase transition in these oxides is very likely driven by oxygen vacancies and occurs once their concentration reaches a certain value. The absence of phase transition in hafnia can thus be explained by the lower concentration level attained by these defects, owing to their higher diffusivity in this material. A similar mechanism can also be invoked to explain the remarkable phase stability of tetragonal zirconia under prolonged low-energy ion irradiation.

The absence of phase transition for the classical XY-model on Sierpiński pyramid with fractal dimension D=2

For the spin models with continuous symmetry on regular lattices and finite range of interactions, the lower critical dimension is d = 2. In two dimensions the classical XY-model displays Berezinskii–Kosterlitz–Thouless (BKT) transition associated with unbinding of topological defects (vortices and antivortices). We perform a Monte Carlo study of the classical XY-model on Sierpiński pyramids (SPs) whose fractal dimension is D = log 4/log 2 = 2 and the average coordination number per site is ≈ 7. The specific heat does not depend on the system size which indicates the absence of a long-range order. From the dependence of the helicity modulus on the cluster size and on boundary conditions, we draw a conclusion that in the thermodynamic limit there is no BKT transition at any finite temperature. This conclusion is also supported by our results for linear magnetic susceptibility. The lack of finite temperature phase transition is presumably caused by the finite order of ramification of SP.

A numerical test of a high-penetrability approximation for the one-dimensional penetrable-square-well model

The one-dimensional penetrable-square-well fluid is studied using both analytical tools and specialized Monte Carlo simulations. The model consists of a penetrable core characterized by a finite repulsive energy combined with a short-range attractive well. This is a many-body one-dimensional problem, lacking an exact analytical solution, for which the usual van Hove theorem on the absence of phase transition does not apply. We determine a high-penetrability approximation complementing a similar low-penetrability approximation presented in previous work. This is shown to be equivalent to the usual Debye-Hückel theory for simple charged fluids for which the virial and energy routes are identical. The internal thermodynamic consistency with the compressibility route and the validity of the approximation in describing the radial distribution function is assessed by a comparison against numerical simulations. The Fisher-Widom line separating the oscillatory and monotonic large-distance behaviors of the radial distribution function is computed within the high-penetrability approximation and compared with the opposite regime, thus providing a strong indication of the location of the line in all possible regimes. The high-penetrability approximation predicts the existence of a critical point and a spinodal line, but this occurs outside the applicability domain of the theory. We investigate the possibility of a fluid-fluid transition by the Gibbs ensemble Monte Carlo techniques, not finding any evidence of such a transition. Additional analytical arguments are given to support this claim. Finally, we find a clustering transition when Ruelle's stability criterion is not fulfilled. The consequences of these findings on the three-dimensional phase diagrams are also discussed.

Electric energy storage properties of poly(vinylidene fluoride)

High discharged energy density observed in poly(vinylidene fluoride) (PVDF) based copolymers has attracted considerable research interests in the past years. Crystalline properties exhibit great influence on their dielectric and energy storage properties. To understand how crystalline properties influence the energy storage properties of PVDF, PVDF films with three different crystal forms are investigated in this paper. It is shown that γ-PVDF is allowed to work under higher electric fields than α- and β-PVDF in the absence of phase transition in α-PVDF and early polarization saturation in β-PVDF. Consequently, γ-PVDF exhibits the highest energy density of 14 J/cm3 under 500 MV/m electric field.

Dynamical susceptibilities of the Falicov-Kimball model with correlated hopping: general approach

The Falicov-Kimball model with correlated hopping is studied in the limit of innite spatial dimensions. Dynamical susceptibilities are calculated using the generalization of the Dynamical Mean-Field Theory (DMFT), which is based on expansion over electron hopping around the single-site limit. A special case of semi-elliptic density of states and diagonal correlated hopping is considered numerically and the absence of phase transition for all temperatures except T = 0 is demonstrated, which corresponds to the known results.

Absence of phase transition in a magnetic field in the [formula omitted] Ising spin glass

We present dynamical magnetic properties in the presence of a static bias field on the 3d Ising spin glass (SG) Fe 0.55 Mn 0.45 TiO 3 . It exhibits critical dynamics only in zero field, suggesting that there is no Almeida–Thouless line for Ising SGs. Instead a dynamical crossover scenario, based on the real-space droplet picture, can explain the in-field magnetic properties. We also interpret the glassy nature of the field-cooled magnetization in accordance with the real-space picture.

On the Distribution and Gap Structure of Lee–Yang Zeros for the Ising Model: Periodic and Aperiodic Couplings

In this work, we present some results on the distribution of Lee–Yang zeros for the ferromagnetic Ising model on the rooted Cayley Tree (Bethe Lattice), assuming free boundary conditions, and in the one-dimensional lattice with periodic boundary conditions. In the case of the Cayley Tree, we derive the conditions that the interactions between spins must obey in order to ensure existence or absence of phase transition at finite temperature (T≠0). The results are first obtained for periodic interactions along the generations of the lattice. Then, using periodic approximants, we are also able to obtain results for aperiodic sequences generated by substitution rules acting on a finite alphabet. The particular examples of the Fibonacci and the Thue-Morse sequences are discussed. Most of the results are obtained for a Cayley Tree with arbitrary order d. We will be concerned in showing whether or not the zeros become dense in the whole unit circle of the fugacity variable. Regarding the one-dimensional Ising model, we derive a general treatment for the structure of gaps (regions free of Lee–Yang zeros) around the unit circle.