Disorder Phase Transition Research Articles

Oxygen vacancy order–disorder transition process during topotactic filament formation in a perovskite oxide tracked by Raman microscopy and transmission electron microscopy

Vacancy-ordered perovskite oxides are attracting attention due to their diverse functions such as resistive switching, electrocatalytic activity, oxygen diffusivity, and ferroelectricity. It is important to clarify the chemical lattice strains arising from compositional changes and the associated vacancy order–disorder phase transitions at the atomic scale. Here, we elucidate the intermediate process of a topotactic phase transition in Ca-doped bismuth ferrite films consisting of alternating stacks of oxygen perovskite layers and a brownmillerite-type oxygen vacancy layer. We use Raman spectroscopy and transmission electron microscopy to closely examine the evolution of local strains exerted on the constituent sub-layers by electrochemical oxidation. A negative Raman chemical shift is observed during oxidation, which is linearly correlated with the local negative chemical expansivity of the oxygen layer. It seemingly contradicts with the general trend that oxides undergo lattice contraction upon oxidation. Oxygen vacancies initially confined in the vacancy layers can be understood to diffuse into the oxygen layers during melting of the ordered structure. The finding deepens our understanding of the electro-chemo-mechanical coupling of vacancy-ordered oxides.

Chirality hierarchical transfer in homochiral polymer crystallization under high-pressure CO2

Ordered phase transitions are commonly correlated to symmetry breaking, while disordered phase transitions are characterized by symmetry restoration. Nevertheless, this study demonstrates that these correlation relations are not always applicable in chiral polymers under high-pressure Carbon Dioxide. Without racemization, homochiral Poly (lactide acid) can generate two vortex-shaped dendritic crystals with opposite spiral chirality, and snowflake-shaped dendritic crystals without spiral chirality. The transition from homochiral molecules to achiral crystals signifies the chiral symmetry restoration during the ordering process. The primary elements responsible for the various hierarchical transfers of homochiral Poly (lactide acid) are related to chain tilt, surface stress, and frustrated structures of Poly (lactide acid) crystals. Here, we show the entropy impact of Carbon Dioxide can be utilized to programmatically regulate the morphological chirality of crystal superstructure and crystal form of homochiral Poly (lactide acid).

Synthesis, crystal structure study, characterization, and DFT investigation of a new nickel(II) complex, [dihomopiperazine nickel (II)] sulfate tetrahydrate

A new nickel (II) complex [NiL2](H2O)4(SO4), where L = 1,4-diazepane, has been synthesized by interaction between nickel sulfate and 1,4-diazepane. This complex crystallizes in the Pmcn orthorhombic unit cell with parameters a = 9.173(2) Å, b = 11.691(2) Å, c = 17.015(2) Å, V = 1824.9(5) Å3, and Z = 4. It possesses a mononuclear structure in which the central NiII atom is coordinated by four N atoms from two 1,4-diazepane ligands in a distorted square-planar geometry. In the crystal, the anions [SO4]2−, the cations [NiL2]2+, and the water molecules are held together by H-bonding to form a 2D supramolecular structure. Differential scanning calorimetry (DSC) results showed that this compound undergoes a reversible order–disorder phase transition at 486 K with a hysteresis of 32 K. In addition, electrical conductivity measurements showed that the complex has a conductivity value of 4.15 10−4 Ω−1cm−1 at 390 K. The Density Functional Theory (DFT) study results qualitatively supported the experimental data obtained by X-ray diffraction and thermogravimetric analysis (TGA).

Order–disorder phase transitions in front of the exit during human crowd evacuations

Human crowds often exhibit collective behaviors through self-organization, such as orderly queueing and disordered congestion at exits. Understanding the dynamic mechanisms behind these behaviors is crucial for pedestrian traffic management and the handling of mass crowds. Although current models and experiments have provided profound insights into ordered and disordered pedestrian groups separately, the transition mechanism from order to disorder within pedestrian crowds in front of exits remains unclear. In this study, a pedestrian queueing evacuation experiment was presented to demonstrate the phase transition process of pedestrian movement states as urgency levels in the environment change. We discovered the migration pattern of the phase transition point under evacuation control and identified different propagation modes of pedestrian velocity waves. Furthermore, a pedestrian motion model based on experimental data and observed phenomena was established. This model not only replicates the observed phenomena and regularities from the experiments but also reveals the quantitative phase transition mechanism of pedestrian movement under the influence of a single factor (i.e., urgency level or queueing ratio). Our findings hold significant implications for various domains, including pedestrian management, traffic control, and pedestrian dynamics.

Insights into the Jahn‐Teller Effect in Layered Oxide Cathode Materials for Potassium‐Ion Batteries

AbstractPotassium‐ion batteries (PIBs) have attracted increasing interest as promising alternatives to lithium‐ion batteries (LIBs) in large‐scale electrical energy storage systems due to the potential price advantages, abundant availability of potassium resources, and low standard redox potential of potassium. However, the pursuit of suitable cathode materials that exhibit desirable characteristics such as voltage platforms, high capacity, and long cycling stability is of utmost importance. Recently, layered transition‐metal oxides for PIBs offer great potential due to their high theoretical capacity, suitable voltage range, and eco‐friendliness. Nevertheless, the progress of KxMO2 cathodes in PIBs faces obstacles due to the detrimental effects of structural disorder and irreversible phase transitions caused by the Jahn‐Teller effect. This review provides a brief description of the origin and mechanism of the Jahn‐Teller effect, accompanied by the proposed principles to mitigate this phenomenon. In particular, the current status of KxMO2 cathodes for PIBs, is summarized highlighting the challenges posed by the Jahn‐Teller effect. Furthermore, promising strategies, such as composition modulation, synthesis approaches, and surface modification, are proposed to alleviate and suppress the Jahn‐Teller effect. These strategies offer valuable insights into the prospects of innovative cathode materials and provide a foundation for future research in the field of PIBs.

A tensor renormalization group analysis of an evolutionary game of competing Ising and Potts subgames

The temperature-induced phase transitions of an evolutionary game of competing Ising- and Potts-type coordination subgames are studied using the tensor renormalization group method proposed by Michael Levin and Cody P. Nave. Depending on the relative strength of the subgames, a continuous Ising order to disorder or a continuous Potts order to disorder or consecutive first-order Potts order to Ising order and continuous Ising order to disorder phase transitions are observed. In the game-theoretic interpretation of the model, these results imply that while both types of coordination can spread in the population at low noise levels, one of them will always be dominant in equilibrium. Under a relatively narrow set of circumstances, a small increase in noise can cause the population to suddenly switch from Ising-type coordination to Potts-type coordination. The results are in general qualitative and quantitative agreement with previous Monte Carlo simulation findings.

Criticality Controlling Mechanisms in Nematic Liquid Crystals

We theoretically study the generic mechanisms that could establish critical behavior in nematic liquid crystals (NLCs). The corresponding free energy density terms should exhibit linear coupling with the nematic order parameter and, via this coupling, enhance the nematic order. We consider both temperature- and pressure-driven, order–disorder phase transitions. We derive a scaled effective free energy expression that describes how qualitatively different mechanisms enforce critical behavior. Our main focus is on the impact of nanoparticles (NPs) in homogeneous NP-NLC mixtures. We illustrate that in the case of pressure-driven phase changes, lower concentrations are needed to impose critical point conditions in comparison with pure temperature variations.

Order–Disorder Phase Transitions in Fe81Ga19–RE Alloys (RE = Dy, Er, Tb, Yb) According to Neutron Diffraction Data

Order–Disorder Phase Transitions in Fe81Ga19–RE Alloys (RE = Dy, Er, Tb, Yb) According to Neutron Diffraction Data

Directed propaganda in the majority-rule model

Advertisement and propaganda have changed continuously in the past decades, mainly due to the people’s interactions at online platforms and social networks, and operate nowadays reaching a highly specific online audience instead targeting the masses. The impacts of this new media effect, oriented directly for a specific audience, are investigated on this study, in which we focus on the opinion evolution of agents in the majority-rule model, considering the presence of directed propaganda. We introduce p as the probability of a “positive” external propaganda and q as the probability to the agents follow the external propaganda. Our results show that the usual majority-rule model stationary state is reached, with a full consensus, only for two cases, namely when the external propaganda is absent or when the media favors only one of the two opinions. However, even for a small influence of external propaganda, the final state is reached with a majority opinion dominating the population. For the case in which the propaganda influence is strong enough among the agents, we show that the consensus cannot be reached at all, and we observe the polarization of opinions. In addition, we show through analytical and numerical results that the system undergoes an order–disorder phase transition that occurs at [Formula: see text] for the case [Formula: see text].

Collective behavior of self-propelled particles with heading estimation via focal observation

Animals, including humans, often achieve velocity alignment by observing their neighbors from their own perspective rather than form a bird’s-eye view. In this study, we explore a particular implementation of this idea, where particles estimate the heading of their neighbors based on their own focal view observations, thereby achieving velocity alignment. Two types of observations are used to estimate the heading of neighbors in this study: the relative position of neighbors at two adjacent moments, and the movement of the focal particle itself. Simulation results show that noise amplitude η arising during observations and the weight parameter s denoting the ratio of noise contained in the two types of observations can induce continuous order–disorder phase transition. The probability density distribution of the noise contained in different models is statistically analyzed, and results show that the type of phase transition mainly depends on the variance of the noise. Furthermore, an optimal value of s is found in our model that makes the model tolerate large noise amplitude. Our findings suggest that the focal view observation plays an important role in collective motion.

Improving Rate Performance by Inhibiting Jahn–Teller Effect in Mn‐Based Phosphate Cathode for Na‐Ion Batteries

AbstractManganese‐based phosphate cathodes are promising candidates for developing advanced sodium‐ion batteries, primarily driven by their reliable elemental abundance, low toxicity, and desirable cycling performance. However, the cooperative Jahn–Teller effect of Mn3+ will inevitably lead to structural disorder and irreversible phase transition, thus greatly harming the reversible capacity, rate, and cycling performance. Herein, a stable NASICON‐type Na3MnHf(PO4)3 cathode is demonstrated with a volume variation of 1.9% upon the process of Na+ extraction/insertion based on the robust Hf─O bond and symmetrical MnO6 octahedron. Moreover, making full use of the stepwise redox reactions of Mn2+/Mn3+/Mn4+, this cathode reveals excellent cycling stability with a capacity retention of 85.4% after 2500 cycles at 10 C. Matching with commercial hard carbon anodes, the assembled full cell keeps a capacity retention of 92.1% with the Coulombic efficiency close to 100% after 600 cycles at 1 C. The research promises opportunities for the structural amelioration of manganese‐based phosphate cathodes toward the application in high‐performance sodium‐ion batteries.

A tensor renormalization group analysis of the Blume–Capel model inspired by game theory

After showing that it can be parametrized as the elementary coordination game of evolutionary game theory, this paper analyzes the Blume–Capel model using the tensor renormalization group method introduced by Michael Levin and Cody P. Nave. The results obtained along the cross sections defined by the coordination game parametrization expand and corroborate earlier findings regarding the location, order, and critical properties of the order–disorder phase transitions in both the zero-field and non-zero-field versions of the Blume–Capel model.

Shock wave induced order to disorder type phase transition of cobalt chloride hexahydrate doped l-histidine hydrochloride monohydrate single crystal

The impact of supersonic shock waves upon materials is one of the fascinating areas of active research in material science. Phase transition behaviour of materials, when subjected to shock waves, is also of great interest in this field. In the present investigation, we have proved the impact of shock wave-induced order–disorder type phase transition of cobalt chloride hexahydrate doped L-histidine hydrochloride monohydrate single crystal. The test crystal was subjected to the corresponding shock pulse counts of 0, 1, 2, 3, and 4 with Mach number 1.7 until the third shock condition, there wasn't a phase change; however, in the fourth shocked condition, there was a phase transition of the order–disorder type noted. X-ray diffractometry, Raman spectroscopy, and UV–Visible spectroscopy are three different analytical techniques that have been used to confirm the aforementioned phase transitions. The order–disorder phase transition enables the investigation of novel aspects of a material's structural properties. The grown crystal had reacted to shock wave exposure in terms of the type of phase transition order–disorder.

Light‐Induced Dielectric Enhancement in a 2D Dion–Jacobson Type Perovskite Phase Transition Material

AbstractStimuli‐responsive materials, showing bistable behaviors between two distinct states under external stimuli, can be potentially applied as basic components of modern electrical and electronic devices. 2D hybrid perovskites hold a promise to switch and tune dielectric bistability based on their solid‐state phase transitions. Here, strong dielectric enhancements are successfully actualized by virtue of light illumination in a Dion–Jacobson (DJ) type 2D hybrid perovskite, (HDA)(MA)2Pb3Br10 (1, where HDA is 1,6‐hexanediammonium and MA is methylammonium). Upon heating, 1 exhibits an ordered–disordered phase transition ≈ 324 K (Tc), accompanying a transition from its low to high dielectric state. Strikingly, its light‐induced dielectric constant changes are greatly enhanced with a magnitude up to 250% near the Tc, superior to most traditional inorganic phase transition materials. This process closely relates to the photoexcited dielectric effect that is caused by the interband photo‐excitation. Benefitting from the stability of DJ‐type perovskite structure, the switching cycles of dielectric enhancement display operational stability with superior anti‐fatigue characteristics. As per the knowledge, the findings of this strong dielectric enhancement are unprecedented in the family of 2D DJ‐type hybrid perovskites, which will facilitate broad interest in exploiting new stimuli‐responsive materials to assemble high‐performance smart electronic devices.

Order–disorder phase transition between high- and low-Z′ crystal structures: crystallographic and non-linear optics study on transition

Order–disorder phase transition between high- and low-Z′ crystal structures: crystallographic and non-linear optics study on transition

Critical behavior of the fluctuation heat capacity near the glass transition of metallic glasses

The high-frequency shear modulus of five Zr-, Pd-, Cu-based conventional and two high-entropy bulk metallic glasses was measured in a wide temperature range up to the beginning of crystallization. Using these data and general thermodynamic relations, the “fluctuation” heat capacity ΔCf determined by local structural fluctuations in the defect regions is introduced and calculated. It is found that ΔCf temperature dependence for all metallic glasses has a large peak located slightly below or above the glass transition temperature but clearly lower than the crystallization onset temperature. The form of this peak resembles the characteristic λ-peak typical for order–disorder phase transitions. It is suggested that this ΔCf-peak reflects certain underlying critical phenomenon. The critical temperature T0 (peak temperature) and corresponding critical index α are determined. Averaged over all seven metallic glasses under investigation in the initial and relaxed states, the critical index <α>=0.26. The results obtained indicate that the fluctuations of thermal energy near the glass transition bear the marks of a continuous phase transition. However, the derived critical index is between those corresponding to a second-order phase transition (α≈0.1) and a critical transition characterized by a tricritical point (α≈0.5).

Magnetic Properties of CuCr1−xLaxS2 Thermoelectric Materials

The magnetic properties (magnetic susceptibility, magnetic moment) and Weiss constant for lanthanum-doped CuCr1−xLaxS2 (x = 0; 0.005; 0.01; 0.015; 0.03) solid solutions were studied using static magnetochemistry at 80–750 K. The samples were characterized by both powder X-ray diffraction and energy-dispersive X-ray spectroscopy. It was shown that synthesized samples are single-phased up to x ≤ 0.01. The presence of the additional phase in the solid solutions with x &gt; 0.015 caused deviation from the simple isovalent Cr3+→Ln3+ cationic substitution principle. It was found that magnetic susceptibility and the Weiss constant are significantly affected by both magnetic properties and lanthanum concentration for the solid solutions doped up to x = 0.01. The largest magnetic moment value of 3.88 µB was measured for the initial CuCrS2-matrix. The lowest value of 3.77 µB was measured for the CuCr0.99La0.01S2 solid solution. The lowest Weiss constant value of −147 K was observed for the initial matrix; the highest one was observed for CuCr0.99La0.01S2 (−139 K). The largest Seebeck coefficient value of 373 µV/K was measured for CuCr0.985La0.015S2 at 500 K; the obtained value was 3.3 times greater compared to the initial CuCrS2-matrix. The field dependence of the magnetic susceptibility allowed one to conclude the absence of ferromagnetic contributions in the total magnetic susceptibility of CuCr1−xLaxS2. The data on magnetic properties can be successfully utilized to investigate the limits of doping atom suitability and order–disorder phase transition temperature in CuCrS2-based solid solutions.

Electric polarization and magnetic properties of (NH4)1–xKxI (x = 0.05–0.17)

While all of the polymorphs of pure NH4I and KI are non-polar, we identify that (NH4)0.95K0.05I is ferroelectric and (NH4)0.87K0.13I and (NH4)0.83K0.17I are pyroelectric through measurements of their pyroelectric current and complex dielectric constant. The order to disorder phase transitions occur near 245 K. Magnetic susceptibility measurements indicate that the proton orbitals of the NH4+ continue to become ordered in the ground state in the (NH4)1–xKxI system up to x ≤ 0.17. The polar phases are proposed to stem from K+ ions disrupting the symmetry of proton-orbital-lattice interactions between the NH4+ and I– ions. Our work introduces a new pathway for the ordered phases of ammonium-based compounds to potentially become ferroelectric.

Bifunctional urea surface-modified high voltage LiNi0.5Mn1.5O4 cathode for enhanced electrochemical performance

Spinel LiNi0.5Mn1.5O4 (LNMO) cathode material has high specific energy density due to its high working voltage (4.7 V vs. Li/Li+). However, high voltage inevitably brings instability of the surface and interface layer properties and ultimately electrolyte decomposition and irreversible side reactions, which incurs structural degradation, capacity decline, and poor kinetics. Herein, a simple and novel surface modification strategy is proposed to obtain a bifunctional modification cathode material with carbon–nitrogen nanocoating and surface disorder phase transition, which is prepared through gas–solid heat treatment of pristine material and urea in a closed reactor. The surface disordered phase transition introduces favorable oxygen vacancies and synchronously constructs the fast diffusion channel of lithium ions, while the carbon–nitrogen nanocoating effectively alleviates the impedance growth of the electrode/electrolyte interface. Therefore, the surface modified U-LMNO exhibits an initial discharge capacity of 130.1 mAh g−1 at 0.2 C and a capacity retention rate of 95.1% after 200 cycles at 1 C, significantly superior to pristine P-LMNO. These results highlight the essentiality of high-voltage LNMO cathode material surface interface design and facilitate the development and commercialization of high-energy-density LNMO-based lithium-ion batteries.

Tri(2-furyl)phosphine-induced robust interphases for durable Nickel-rich Lithium-ion batteries

Ni-rich LiNixCoyMn1−x−yO2/graphite batteries with Ni ≥ 0.8 have aroused great interest in high-energy–density Li-ion batteries. However, their practical applications still face huge challenges owing to severe capacity fading on unstable cathodic solid electrolyte interfaces (SEI). Herein, we propose an advanced electrolyte additive, tri(2-furyl)phosphine (FuP), to induce the simultaneous formation of robust SEI films on cathode and anode surfaces. This interphase can significantly improve the cyclability of commercial LiNi0.8Co0.1Mn0.1O2/graphite pouch cells at 45 °C and reduce cell impedance during cycling. The capacity retention rate of the cells with the FuP-based electrolyte can reach 90 % after 600 cycles, which is considerably better than that of baseline batteries (70 %). Mechanistic studies indicate that FuP suppresses the formation of fragile Li2CO3 to generate more stable LiF, LixPOyFz, and additional organic phosphorus species on the electrode surface, thereby preventing cation disorder and irreversible phase transitions. These results provide a facile and efficient strategy for enhancing the performance of Ni-rich Li-ion batteries.