Search

The emergence of order from initial disordered movement in self-propelled collective motion is an instance of nonequilibrium phase transition, which is known to be first order in the thermodynamic limit. Here, we introduce a multiplicative scalar noise model of collective motion as a modification of the original Vicsek model, which more closely mimics the particles' behavior. We allow for more individual movement in sparsely populated neighborhoods, the mechanism of which is not incorporated in the original Vicsek model. This is especially important in the low velocity and density regime where the probability of a clear neighborhood is relatively high. The modification, thus, removes the shortcoming of the Vicsek model in predicting continuous phase transition in this regime. The onset of collective motion in the proposed model is numerically studied in detail, indicating a first-order phase transition in both high and low velocity/density regimes for systems with comparatively smaller size which is computationally desirable. [ABSTRACT FROM AUTHOR]

Angiogenesis is a morphogenic process resulting in the formation of new blood vessels from pre-existing ones, usually in hypoxic micro-environments. The initial steps of angiogenesis depend on robust differentiation of oligopotent endothelial cells into the Tip and Stalk phenotypic cell fates, controlled by NOTCH-dependent cell-cell communication. The dynamics of spatial patterning of this cell fate specification are only partially understood. Here, by combining a controlled experimental angiogenesis model with mathematical and computational analyses, we find that the regular spatial Tip-Stalk cell patterning can undergo an order-disorder transition at a relatively high input level of a pro-angiogenic factor VEGF. The resulting differentiation is robust but temporally unstable for most cells, with only a subset of presumptive Tip cells leading sprout extensions. We further find that sprouts form in a manner maximizing their mutual distance, consistent with a Turing-like model that may depend on local enrichment and depletion of fibronectin. Together, our data suggest that NOTCH signaling mediates a robust way of cell differentiation enabling but not instructing subsequent steps in angiogenic morphogenesis, which may require additional cues and self-organization mechanisms. This analysis can assist in further understanding of cell plasticity underlying angiogenesis and other complex morphogenic processes.

Copyright of Precious Metals / Guijinshu is the property of Precious Metals Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the present study, Bi2O3 compositions co–doped with different rare earth oxides were synthesized for IT–SOFC units utilizing the solid–state reaction process under atmospheric conditions. The cubic δ-phase, an excellent ion conductor, was effectively stabilized in certain samples, with XRD patterns including only peaks of that phase. Compositions with more than 35% total dopant concentration exhibited multiple phase structures, particularly monoclinic α and R-phases. The diffraction peak for the (111) plane moved to greater diffraction angles as doping concentration increased, indicating the influence of multiple dopants on the structural features. The lack of both endothermic and exothermic peaks in the patterns proved that there is no phase transition. Arrhenius plots revealed that when overall dopant concentration increased, electrical conductivity dropped primarily because of a lack of cation polarizability. The highest conductivity measured at 750 °C was found to be 0.0228 S.cm–1, with a corresponding activation energy of 0.86 eV. The FE-SEM pictures confirmed that grain size was not uniform over the surface, and it shrank substantially as the total dopant concentration progressively increased, indicating enhanced microstrain in the lattice due to excessive doping. [ABSTRACT FROM AUTHOR]

Schizophyllan is a triple helical β‐1,3‐D‐glucan, and shows the cooperative order–disorder transition in the aqueous solution at the triple helix state. In this paper, the solvent stabilizing effects of two carboxylic acids, acetic acid and citric acid, on the cooperative order–disorder transition of aqueous schizophyllan solution were investigated from DSC and SEC‐MALS measurements. The transition temperature (Tr) was shifted to higher temperature with increasing the molar fraction of carboxylic acid in the mixture (x). The transition enthalpy (ΔHr) was increased with increasing x. These solvent stabilizing effects indicate that these carboxylic acid molecules were selectively associated with the branched side chains of schizophyllan to stabilize the ordered state. The composition dependencies of Tr and ΔHr were analyzed by the linear cooperative transition theory to estimate the association parameters between the side chains and carboxylic acid. The theoretical parameters obtained were compared with those for the other active substances for the transition to discuss the molecular interactions between the triple helix and carboxylic acid. [ABSTRACT FROM AUTHOR]

[Display omitted] Shear thickening of multimodal suspensions has proven difficult to understand because the rheology depends largely on the microscopic details of stress-induced frictional contacts at different particle size distributions (PSDs). Our discrete particle simulations below a critical volume fraction ϕ c over a broad range of shear rates and PSDs elucidate the basic mechanism of order–disorder transition. Around the theoretical optimal PSD (relative content of small particles ζ 1 = 0.26), particles order into a layered structure in the Newtonian regime. At the onset of shear thickening, this layered structure transforms to a disordered one, accompanied by an abrupt viscosity jump. Minor increase in large-large particle contacts after the order–disorder transition causes apparent increase in radial force along the compressional axis. Bidisperse suspensions with less regular but stable layered structure at ζ 1 = 0.50 show good fluidity in the shear thickening regime. This work shows that in inertial flows where particle collisions dominate, order–disorder transition could play an essential role in shear thickening for bidisperse suspensions. [ABSTRACT FROM AUTHOR]

Change of conformation or polarization of molecules is an expression of their functionality. If the two correlate, electric fields can change the conformation. In the case of endofullerene single-molecule magnets the conformation is linked to an electric and a magnetic dipole moment, and therefore magnetoelectric effects are envisoned. The interface system of one monolayer Sc2TbN@C80 on hexagonal boron nitride (h-BN) on Ni(111) has been studied. The molecular layer is hexagonally close packedbut incommensurate. With photoemission the polarization and the conformation of the molecules are addressed by the work function and angular intensity distributions. Valence band photoemission (ARPES) shows a temperature-induced energy shift of the C80 molecular orbitals that is parallel to a change in work function of 0.25 eV without charging the molecules. ARPES indicates a modification in molecular conformations between 30 and 300 K. This order–disorder transition involves a polarization change in the interface and is centered at 125 K as observed with high-resolution X-ray photoelectron spectroscopy (XPS). The temperature dependence is described with a thermodynamic model that accounts for disordering with an excitation energy of 74 meV into a high entropy ensemble. All experimental results are supported by density functional theory (DFT). [ABSTRACT FROM AUTHOR]

Order–disorder transitions are widely explored in various vortex structures in condensed matter physics, that is, in the type-II superconductors and Bose–Einstein condensates. In this study, the ordering of the polar vortex phase in [Pb(Zr0.4Ti0.6)O3]n/(SrTiO3)n (PZT/STO) superlattices is investigated through phase-field simulations. With a large tensile substrate strain, an antiorder vortex state (where the rotation direction of the vortex arrays in the neighboring ferroelectric layers are flipped) is discovered for short-period PZT/STO superlattice. The driving force is the induced in-plane polarization in the STO layers due to the large tensile epitaxial strain. Increasing the periodicity leads to antiorder to disorder transition, resulting from the high energy of the head-to-head/tail-to-tail domain structure in the STO layer. On the other hand, when the periodicity is kept constant in short-period superlattices, the order–disorder–antiorder transition can be engineered by mediating the substrate strain, due to the competition between the induction of out-of-plane (due to interfacial depolarization effect) and in-plane (due to strain) polarization in the STO layer. The 3D ordering of such polar vortices is still a topic of significant current interest and it is envisioned that this study will spur further interest toward the understanding of order–disorder transitions in ferroelectric topological structures.

Abstract Change of conformation or polarization of molecules is an expression of their functionality. If the two correlate, electric fields can change the conformation. In the case of endofullerene single‐molecule magnets the conformation is linked to an electric and a magnetic dipole moment, and therefore magnetoelectric effects are envisoned. The interface system of one monolayer Sc2TbN@C80 on hexagonal boron nitride (h‐BN) on Ni(111) has been studied. The molecular layer is hexagonally close packedbut incommensurate. With photoemission the polarization and the conformation of the molecules are addressed by the work function and angular intensity distributions. Valence band photoemission (ARPES) shows a temperature‐induced energy shift of the C80 molecular orbitals that is parallel to a change in work function of 0.25 eV without charging the molecules. ARPES indicates a modification in molecular conformations between 30 and 300 K. This order–disorder transition involves a polarization change in the interface and is centered at 125 K as observed with high‐resolution X‐ray photoelectron spectroscopy (XPS). The temperature dependence is described with a thermodynamic model that accounts for disordering with an excitation energy of 74 meV into a high entropy ensemble. All experimental results are supported by density functional theory (DFT).

Angiogenesis is a morphogenic process resulting in the formation of new blood vessels from pre-existing ones, usually in hypoxic micro-environments. The initial steps of angiogenesis depend on robust differentiation of oligopotent endothelial cells into the Tip and Stalk phenotypic cell fates, controlled by NOTCH-dependent cell–cell communication. The dynamics of spatial patterning of this cell fate specification are only partially understood. Here, by combining a controlled experimental angiogenesis model with mathematical and computational analyses, we find that the regular spatial Tip–Stalk cell patterning can undergo an order–disorder transition at a relatively high input level of a pro-angiogenic factor VEGF. The resulting differentiation is robust but temporally unstable for most cells, with only a subset of presumptive Tip cells leading sprout extensions. We further find that sprouts form in a manner maximizing their mutual distance, consistent with a Turing-like model that may depend on local enrichment and depletion of fibronectin. Together, our data suggest that NOTCH signaling mediates a robust way of cell differentiation enabling but not instructing subsequent steps in angiogenic morphogenesis, which may require additional cues and self-organization mechanisms. This analysis can assist in further understanding of cell plasticity underlying angiogenesis and other complex morphogenic processes.

We investigated pressure-induced order-disorder transition in the B-site-ordered double perovskite oxide La2CoRuO6. La2CoRuO6 crystallized in a double perovskite structure with rock-salt-type B-site ordering of Co2+ and Ru4+ ions in the sample synthesized under ambient-pressure and high-temperature (1373 K) conditions. The ambient-pressure B-site-ordered phase of La2CoRuO6 underwent phase transition from monoclinic to orthorhombic structure by treating high-pressure and high-temperature conditions of 8 GPa and 1373 K. Structure refinement based on the synchrotron X-ray powder diffraction data demonstrates that the B-site cationic ordering was completely destroyed in the high-pressure phase of La2CoRuO6, accompanied by a slight reduction in lattice volume (ΔV = −0.25%). X-ray absorption spectroscopy revealed that the valence states of Co2+ and Ru4+ were retained in the high-pressure phase, indicating that the primary driving force for the pressure-induced order-disorder transition in La2CoRuO6 is the negative PΔV term in the Gibbs free energy. The order-disorder transition pressure in La2CoRuO6 (8 GPa) was lower than that in isoelectronic oxide Y2CoRuO6 (15 GPa), suggesting that the compressibilities of A-site metal ions play a crucial role in the transition. The high-pressure disordered phase of La2CoRuO6 exhibited a short-range magnetic ordering below 22 K because of the absence of the cationic ordering, whereas the ambient-pressure ordered phase exhibited an antiferromagnetic long-range ordering below 25 K. [ABSTRACT FROM AUTHOR]

Schizophyllan is a high molecular weight β‐1,3‐D‐glucan having three β‐1,3‐D‐glucoses and one branched β‐1,6‐D‐glucose in the repeating unit. It dissolves as a triple helix in aqueous solutions but exhibits two separate order‐disorder transitions: a low temperature cooperative order‐disorder transition (CODT) related mainly to the side chains, and a high temperature transition involving triplex dissociation. The branched side chain can be oxidized selectively by periodate oxidation to form a dialdehyde. Subsequent reactions may produce different kinds of derivatives: a dicarboxylated derivative (sclerox), or a Smith‐degraded (reduced dialdehyde) derivative. These derivatives still dissolve in water as trimers but the CODT may be strongly modified, depending on degree of chemical modification. The CODT behavior is analyzed with linear cooperative transition (LCT) theory. These theoretical analyses indicate that only unmodified units of sclerox and Smith degraded derivatives contribute to the transition enthalpy. With increasing degree of chemical modification, the transition curve broadens and the transition temperature shifts to lower temperatures. This happens because contiguous sequences of ordered structures gradually shorten with increasing degree of chemical modification. Dimethyl sulfoxide and imidazole are further employed to investigate solvent effects of CODT for both schizophyllan and the chemically modified derivatives. These compounds are shown to favorably associate with the unmodified units to stabilize the ordered structures. [ABSTRACT FROM AUTHOR]

Neutron diffraction and total scattering are combined to investigate a series of single-phase 10-component compositionally complex fluorite-based oxides, [(Pr0.375Nd0.375Yb0.25)2(Ti0.5Hf0.25Zr0.25)2O7]1-x[(DyHoErNb) O7]x, denoted as 10CCFBOxNb. A long-range order-disorder transition (ODT) occurs at x = 0.81± 0.01 from the ordered pyrochlore to disordered defect fluorite. In contrast to ternary oxides, this ODT occurs abruptly without an observable two-phase region; moreover, the phase stability in 10CCFBOs deviates from the well-established criteria for simpler oxides. Rietveld refinements of neutron diffraction patterns suggest that this ODT occurs via the migration of oxygen anions from the position 48f to 8a, with a small final jump at the ODT; however, the 8a oxygen occupancy changes gradually (without an observable discontinuous jump). We further discover diffuse scattering in Nb-rich compositions, which suggests the presence of short-range order. Using small-box modelling, four compositions near ODT (x =0.75, 0.8, 0.85, and 1) can be better fitted by C2221 weberite ordering for the local polyhedral structure at nanoscale. Interestingly, 10CCFBO0.75Nb and 10CCFBO0.8Nb possess both long-range pyrochlore order and short-range weberite-type order, which can be understood from severe local distortion of the pyrochlore polyhedral structure. Thus, weberite-type short-range order emerges before the ODT, coexisting and interacting with long-range pyrochlore order. After the ODT, the long-range pyrochlore order vanishes but the short-range weberite-type order persists in the long-range disordered defect fluorite structure. Notably, a drop in the thermal conductivity coincides with emergence of the short-range order, instead of the long-range ODT. [ABSTRACT FROM AUTHOR]

The stability of solid-solution phases in FCC and BCC lattices was examined in multi-component alloys based on the CALPHAD technique using the compound energy formalism and regular solution model. From the thermodynamic calculations, it was found in ternary systems that the single solid-solution phase became stable around the equiatomic composition where the configurational entropy was the largest value. The transition temperature from the disordered phase to ordered phase(s) or miscibility gap(s) decreased with the increasing number of elements in the system. The order-disorder transition temperature on the FCC lattice was affected by the end member of the ordered phases existing at the equiatomic composition, whereas it was not significant for the order-disorder transition in the BCC lattice. The single solidsolution phase region at equiatomic compositions was affected by variations in the interaction parameters. In multi-component systems, the variations were averaged with increasing the number of elements in the system. This suggests that high-entropy alloys can afford a variety of elements. This study shows that the disordered state can be formed in multicomponent systems around the equiatomic composition and suggests clearly that due to the high-entropy effect, the solution phases are stabilized. [ABSTRACT FROM AUTHOR]

With the prosperity of high entropy alloys, short-range ordering is getting more and more attentions and regarded as the deciding role in the hardening or softening of solid solutions. In this work, the phase stability and mechanical properties of short-range ordered and disordered body-centered cubic (BCC) structures of W-X solid solutions (X = V, Nb, and Ta) are systematically investigated through a combination of first-principles calculation, cluster expansion and quasi-harmonic Debye formula. Based on the calculated heat of formation (Δ H f ), W-X solid solutions show a strong short-range ordering tendency, as those ordered structures have a lower Δ H f than the disordered ones. Generally, short-range ordering results in the decrease of the shear modulus to bulk modulus ratio (G/B) and hardness for W-V and W-Ta systems, while an increase for W-Nb system, manifesting solid-solution softening and hardening effect, respectively. The short-ranged ordered C11 b W 2 X phase exhibits a singularity in mechanical properties characterized by a higher G/B than solid solution phases compared to other ordered phases. The lattice distortion breaks the symmetric W-W bonds and leads to partial covalency in the W 2 X phases. Besides the increased brittleness, this distortion also causes the increase of ideal strength and the reduction of maximum tensile elongation of W 2 X. The effect of short-range ordering and lattice distortion on the hardening or softening of the W-X systems disappears after the order-disorder transition. The W-V and W-Ta phases have higher order-disorder transition temperature than W-Nb phase. Nevertheless, the transition temperature is relatively low in comparison to their melting points, signifying the important role in controlling the solute concentration at lower temperature. [Display omitted] • Strong short-range ordering tendency was found in W-X (V, Nb, Ta) solid solutions. • Solid-solution softening happens in W-V and W-Ta, while hardening in W-Nb systems. • Singularity in mechanical properties occurs in C11 b W 2 X after lattice distortion. • Ideal strength and electronic structure reveal the abnormal brittleness of C11 b W 2 X. • Order-disorder transition temperature of W-Nb is lower than W-V and W-Ta systems. [ABSTRACT FROM AUTHOR]

Folded proteins show a high degree of structural order and undergo (fairly constrained) collective motions related to their functions. On the other hand, intrinsically disordered proteins (IDPs), while lacking a well-defined three-dimensional structure, do exhibit some structural and dynamical ordering, but are less constrained in their motions than folded proteins. The larger structural plasticity of IDPs emphasizes the importance of entropically driven motions. Many IDPs undergo function-related disorder-to-order transitions driven by their interaction with specific binding partners. As experimental techniques become more sensitive and become better integrated with computational simulations, we are beginning to see how the modest structural ordering and large amplitude collective motions of IDPs endow them with an ability to mediate multiple interactions with different partners in the cell. To illustrate these points, here, we use Prostate-associated gene 4 (PAGE4), an IDP implicated in prostate cancer (PCa) as an example. We first review our previous efforts using molecular dynamics simulations based on atomistic AWSEM to study the conformational dynamics of PAGE4 and how its motions change in its different physiologically relevant phosphorylated forms. Our simulations quantitatively reproduced experimental observations and revealed how structural and dynamical ordering are encoded in the sequence of PAGE4 and can be modulated by different extents of phosphorylation by the kinases HIPK1 and CLK2. This ordering is reflected in changing populations of certain secondary structural elements as well as in the regularity of its collective motions. These ordered features are directly correlated with the functional interactions of WT-PAGE4, HIPK1-PAGE4 and CLK2-PAGE4 with the AP-1 signaling axis. These interactions give rise to repeated transitions between (high HIPK1-PAGE4, low CLK2-PAGE4) and (low HIPK1-PAGE4, high CLK2-PAGE4) cell phenotypes, which possess differing sensitivities to the standard PCa therapies, such as androgen deprivation therapy (ADT). We argue that, although the structural plasticity of an IDP is important in promoting promiscuous interactions, the modulation of the structural ordering is important for sculpting its interactions so as to rewire with agility biomolecular interaction networks with significant functional consequences.

Rare-earth uranates-RE6UO12 are synthesized by heating mixture of uranium oxide and rare-earth oxides in 1:6 ratio above 1273 K. These compounds stabilize in rhombohedral structure at ambient. High-pressure (HP) X-ray diffraction studies reveal that the compounds are stable at lower pressures, beyond which disorder is seen to originate and compound has a tendency to amporphize at very HPs. The a-axis of the lattice is found to be more rigid as compared to c-axis because of corner sharing polyhedra along a-axis. Anomalous compressibility behaviour is seen in Gd6UO12, where sharp decrease in the bulk modulus is observed. The behaviour is against the normal trend of compressibility in RE6UO12 compounds along rare-earth cation series. [ABSTRACT FROM AUTHOR]

The L 1 0 -FePt nanocrystals exhibit unique magnetic and catalytic properties, but suffer from the ordering difficulty. The addition of Cu can facilitate the L 1 0 -FePt ordering for some Fe–Pt–Cu alloys, however, the action mechanism is far from being well understood. In this work, a systematic study has been performed to the phase diagrams of the Fe–Pt–Cu system. The isothermal sections at 600 °C, 750 °C and 1000 °C, as well as the partial vertical sections of Fe 50 Pt 50 –Cu 50 Pt 50 and Fe 50 Pt 50 –Cu, were constructed. An emphasis has been paid to the L 1 0 -FePt phase, which has a wide composition range with a solid solubility of Cu up to 40.0 at% at 600 °C. Its order-disorder transition temperature decreases rapidly when deviating from 54 at% Pt, but at different lower rates along (FePt) 100- x Cu x and (Fe 50- x Cu x)Pt 50 with the increase of Cu. The ternary miscibility gap which originates from the Fe–Cu side has been studied by both experimental determinations and thermodynamic calculations. The results indicate that, at certain low temperatures, for instance 300 °C, the metastable miscibility gap can expand even up to 45 at% Pt, entering the L 1 0 -FePt phase region. An ordering transition mechanism of the L 1 0 -FePt phase stimulating by a two-phase separation was thus proposed. For a specially designed disordered Fe–Pt–Cu alloy, a metastable two-phase separation can take place firstly in the annealing process, driving the Cu atoms forming Cu-rich particles, leaving a large number of vacancies in the alloy, and consequently, accelerate the atomic diffusion and stimulate the subsequent L 1 0 ordering transition. These results will provide a new perspective for the composition design of Fe–Pt–Cu catalysts and magnetic recording media. [Display omitted] • Phase diagrams of the Fe–Pt–Cu system were critically determined. • Effects of Cu addition on the order-disorder transition of L 1 0 -FePt were well described. • Ternary miscibility gap of the Fe–Pt–Cu system in both stable and metastable states was established. • An ordering transition mechanism of L 1 0 -FePt phase stimulating by a two-phase separation was proposed for Fe–Pt–Cu alloys. [ABSTRACT FROM AUTHOR]

In this paper, the (Bi 2 O 3) 1–x–y (Tm 2 O 3) x (Yb 2 O 3) y ternary systems were successfully synthesized by the solid–state reaction method under air conditions. All powder compositions were then heat treated for 100 h at 750 °C to allow for partial substitution of dopant cations, Tm3+ and Yb3+, between host Bi3+ cations. Characterizations of fabricated compositions were carried out by XRD, TG and DTA, FPPT, and FE–SEM techniques. Stacked XRD patterns verified that all compositions included solely single–phase peaks, with the exception of Bi 0.92 Tm 0.04 Yb 0.04 O 1.5–δ and Bi 0.88 Tm 0.04 Yb 0.08 O 1.5–δ , whose patterns suggested mixed phases. The DTA curves, depending on temperature, detected the endothermic peaks at around 600 °C, implying that an order–disorder transition occurs in the anion sublattice of the doped crystal. At 700 °C, the conductivity of the Bi 0.88 Tm 0.08 Yb 0.04 O 1.5–δ system was found to be 0.432 S/cm, surpassing the conductivity of a single–doped (Bi 2 O 3) 0.80 (Er 2 O 3) 0.20 system, which had a value of 0.37 S/cm at the same temperature. • The cubic δ-phase with high ion conductivity became stable in the majority of fabricated compositions. • The magnified XRD patterns indicated a peak shift because of doping. • The DTA curves reveal the endothermic peaks at around 600 °C, signifying an order-disorder transition. • The highest conductivity is found to be 0.432 S/cm at 700 °C for the Bi 0.88 Tm 0.08 Yb 0.04 O 1.5–δ composition. • The order-disorder transition is noticeable on the Arrhenius plots at around 600 °C. [ABSTRACT FROM AUTHOR]

Pursuing novel thermal barrier–coating materials with lower thermal conductivity and high‐temperature stability can simultaneously improve the working efficiency and service temperature of a gas turbine. In this study, a series of high‐entropy RE2(Y0.2Yb0.2Nb0.2Ta0.2Ce0.2)2O7 (RE = La, Nd, Sm, Gd, Dy, and Er) oxides were prepared though solid‐state reaction. Through tuning the rare‐earth cations, an order–disorder transition occurs from certain partially ordered weberite structure (C2221) to disordered defective fluorite structure (Fm3¯$\bar{3}$m). All the high‐entropy RE2(Y0.2Yb0.2Nb0.2Ta0.2Ce0.2)2O7 oxides possess low thermal conductivity in the range of 0.91–1.34 W m−1 K−1 at room temperature, which can be attributed to increased lattice anharmonicity and disorder, resulting in additional phonon scattering. Herein, we proved that the incorporation of heterovalent cations at B‐sites in high‐entropy A2B2O7 crystals is an effective strategy to reduce the thermal conductivity without compromising the decrease of oxygen vacancy. Moreover, the high‐entropy RE2(Y0.2Yb0.2Nb0.2Ta0.2Ce0.2)2O7 oxides show the relatively higher thermal expansion coefficients of 10.3–10.7 × 10−6°C−1 and excellent phase stability at elevated temperatures. [ABSTRACT FROM AUTHOR]

The backbone of the Janus double-brush copolymer may break during long-term service, but whether this breakage affects the self-assembled phase state and microphase transitions of the material is still unknown. For the Janus double-brush copolymers with a periodicity in molecular architecture ranging from 1 to 10, the influences of the architectural periodicity on their phase diagrams and order–disorder transitions (ODT) were investigated by the self-consistent mean field theory (SCFT). In total, nine microphases with long-range order were found. By comparing the phase diagrams between copolymers of different periodicity, a decrease in periodicity or breakage along the copolymer backbone had nearly no influence on the phase diagrams unless the periodicity was too short to be smaller than 3. For copolymers with neutral backbones, a decrease in periodicity or breakage along the copolymer backbone reduced the critical segregation strengths of the whole copolymer at ODT. The equations for the critical segregation strengths at ODT, the architectural periodicity, and the volume fraction of the backbone were established for the Janus double-brush copolymers. The theoretical calculations were consistent with the previous theoretical, experimental, and simulation results. [ABSTRACT FROM AUTHOR]

Single-phase high-entropy alloys with compositionally disordered elemental arrangements have excellent strength, but show a serious embrittlement effect with increasing strength. Precipitation-hardened high-entropy alloys, such as those strengthened by L12-type ordered intermetallics, possess a superior synergy of strength and ductility. In this work, we employ first-principles calculations and thermodynamic simulations to explore the atomic interactions and order–disorder transitions in FeCoNiAl1−xTix high-entropy alloys. Our calculated results indicate that the atomic interactions depend on the atomic size of the alloy components. The thermodynamic stability behaviors of L12 binary intermetallics are quite diverse, while their atomic arrangements are short-range in FeCoNiAl1−xTix high-entropy alloys. Moreover, the order–disorder transition temperatures decrease with increasing Ti content in FeCoNiAl1−xTix high-entropy alloys, the characteristics of order–disorder transition from first-principles calculations are in line with experimental observations and CALPHAD simulations. The results of this work provide a technique strategy for proper control of the order–disorder transitions that can be used for further optimizing the microstructure characteristics as well as the mechanical properties of FeCoNiAl1−xTixhigh-entropy alloys. [ABSTRACT FROM AUTHOR]

The order-disorder transitions (ODT) of core-shell bottle brush copolymer and its structural isomers were investigated by dissipative particle dynamics simulations and theoretically by random phase approximation. Introducing a chain topology parameter λ which parametrizes linking points between M diblock chains each with N monomers, the degree of incompatibility at ODT ( (χ N) ODT ; χ being the Flory–Huggins interaction parameter between constituent monomers) was predicted as a function of chain topology parameter (λ) and the number of linked diblock chains per bottle brush copolymer (M). It was found that there exists an optimal chain topology about λ at which (χ N) ODT gets a minimum while the domain spacing remains nearly unchanged. The prediction provides a theoretical guideline for designing an optimal copolymer architecture capable of forming sub-10 nm periodic structures even with non-high χ components. [ABSTRACT FROM AUTHOR]

Mg2GeO4 is important as an analog for the ultrahigh-pressure behavior of Mg2SiO4, a major component of planetary interiors. In this study, we have investigated magnesium germanate to 275 GPa and over 2,000 K using a laser-heated diamond anvil cell combined with in situ synchrotron X-ray diffraction and density functional theory (DFT) computations. The experimental results are consistent with the formation of a phase with disordered Mg and Ge, in which germanium adopts eightfold coordination with oxygen: the cubic, Th3P4-type structure. DFT computations suggest partial Mg-Ge order, resulting in a tetragonal I42d structure indistinguishable from I43d Th3P4 in our experiments. If applicable to silicates, the formation of this highly coordinated and intrinsically disordered phase may have important implications for the interior mineralogy of large, rocky extrasolar planets. [ABSTRACT FROM AUTHOR]

Photoluminescence (PL) spectra of natural Cr3+ doped MgAl2O4 spinel from Tanzania were taken during its order-disorder transition (ODT) process. Samples were changed their disordered degree by quenching treatment. PL spectra were taken at the liquid nitrogen (LN) temperature (∼77 K) using a 532 nm laser excitation. Spectra from different states were compared with each other and R-line and N-line ratio was used to illustrate the disordered degree of spinel during ODT process. It can be used as a reference for other similar researches, such as spinel PL characterization of the other members of this group, ordered degree of synthetic spinel single crystal or ceramics materials, thermal history of spinel, and non-destructive identification of natural and heated spinel gemstones, spinel original distinguishing, further PL spectra analysis and XRD relationship research.

Unexpected inversion‐symmetry breaking was observed in the order–disorder phase transitions of [M(acac)2(abco)2] (1; M=Co2+, 2; Ni2+, acac−=2,4‐pentanedionato, abco=1‐azabicyclo‐[2.2.2]‐octane=quinuclidine) during heating. The isostructural, transition‐free complexes [M(acac)2(cabco)2] (3; M=Co2+, 4; Ni2+, cabco=3‐chloro‐1‐azabicyclo‐[2.2.2]‐octane=3‐chloroquinuclidine) were also studied for comparison. Complexes 1 and 2 crystallized in ordered phases in the centrosymmetric I2/m space group at 100 K, whereas they crystallized in disordered phases in the non‐symmetric I2 space group at 300 K. The 60° step rotation disordering of the abco ligands was observed in the electron density maps of 1 and 2, which was consistent with the transition enthalpies estimated by differential scanning calorimetry (DSC). Gradual phase transitions were observed for 1 and 2 by DSC and powder X‐ray diffraction (PXRD) at approximately 225 K. The inversion‐symmetry disordering was likely induced by the local pseudo‐symmetry of the abco ligands, increasing from trigonal to hexagonal and the increased steric repulsion pathways among them. [ABSTRACT FROM AUTHOR]

In this work, we study a model of asymmetric two-component lattice fermion system at half-filling, where particles of both species (distinguishable by, e.g., spin) can interact only via nearest-neighbor repulsion W. The analysis is performed on the Bethe lattice using the Hartree-Fock-type mean-field approximation, which is rigorous in the limit of high dimensions. At sufficiently low temperatures, both antiferromagnetic and charge orders (related to inhomogeneous distribution of particles with both spins) coexist in the system. We find that an order-disorder continuous transition occurs with increasing temperature. The transition temperature depends on the ratio t↑/t↓ of the hopping amplitudes of both fermion species (i.e., the asymmetry of the model). For fixed W, it is the biggest if one component is localized (e.g., t↑ = 0), and it decreases to its minimal value for the same hopping amplitudes (t↑ = t↓). Moreover, it increases with W for fixed t↑/t↓. Dependencies of order parameters with model parameters and temperature are also presented. [ABSTRACT FROM AUTHOR]

The paper considers the order-disorder transition in a sequence of two varieties of repeating units. It is shown that the reduced free energy converges to the limit at the chain length of more than 3000. The origination of the fine structure of differential melting curves, the order–disorder transition interval, and the behavior of the fraction of junctions between the ordered and disordered phases are considered. In the primary structure, the small-scale correlations are taken into account. [ABSTRACT FROM AUTHOR]

Disordered Pd–Fe alloys show a positive excess-volume effect, contrary to the predictions of the Iida–Guthrie model. The effect becomes larger at a composition of approximately Pd 0.5 Fe 0.5. The origin of the positive excess-volume effect was investigated by using first-principles calculations to study the electronic structures in the ordered and disordered states of Pd–Fe alloys with two different compositions, i.e., Pd 0.53 Fe 0.47 and Pd 0.75 Fe 0.25. The calculated partial density of states for the disordered state in Pd 0.53 Fe 0.47 indicates weakening of Pd metallic bonds because of fully occupied 4 d majority-spin states with enhanced anti-bonding characteristics, which cause an increase in the volume. In addition, the magneto-volume effect, which minimizes the increase in the electronic kinetic energy caused by exchange splitting, contributes to the positive excess volume. The calculated electronic states and those obtained from hard X-ray photoelectron spectra were consistent with each other. [Display omitted] [ABSTRACT FROM AUTHOR]

Effect of mixing dodecanethiol-capped Au nanoparticles (AuNPs) on the critical point of the liquid ordered ( L o ) to liquid disordered ( L d ) phase transition of myristic acid (MyA) Langmuir monolayer has been studied through quantitative evaluation of the two-dimensional patterns of AuNP clusters created through de-mixing and observed through Brewster angle microscopy. The critical temperature ( T c ), marked by the emergence of a Bethe lattice-like (BLL) pattern of ‘fingers’ and ‘arms’, was brought down from 38 ∘ C in pristine MyA monolayers to 28 and 10 ∘ C for 20 and 40% w/w AuNP concentrations. Analysis of the BLL at the length scales of these ‘fingers’ and ‘arms’ showed that the lowering of T c follows two different paths for the two concentrations, through a repulsive force for the lower and an attractive force for the higher concentration at the ‘fingers’ length scale, while at the scale of ‘arms’ the force between NPs is always repulsive. Based on the observations that the repulsive force operates at larger interparticle separation and the attractive one acts at smaller separations, we tentatively assign the first to be a dipolar repulsion and the second to be lipophilic force of quantum mechanical origin. We have also indicated qualitatively how this realignment of forces between nanoparticles can affect the lipophilic force between the hydrocarbon chains of the NP capping and those chains in the monolayer. [ABSTRACT FROM AUTHOR]

The ongoing electrification and miniaturization increase the quality demands on solder joints. A bottleneck for solder joint reliability can be the intermetallic Cu6Sn5 phase, which undergoes a phase transition, implying a volume change in a relevant temperature range. There are contradicting reports on the sign and magnitude of this volume change, which possibly implements stresses and cracks in solder joints. To clarify the characteristics of the phase transition, different samples were manufactured by applying industrial-like standards and isothermal heat treatments around the predicted phase transition temperature. Using x-ray diffraction, a coexistence of ordered η′ and disordered η was detected in samples treated at 438–445 K. The lattice parameters show that the volume of the disordered η phase is approximately 0.64–0.65% smaller than the one of the ordered η′ phase. A comparison with order–disorder transitions in structurally related phases shows that the volume change based on order–disorder transitions is normally of opposite sign and around 0.1–0.2%. Therefore, an effect of different compositions is considered responsible for the volume change. Adopting the exact composition Cu6Sn5 (Cu1.20Sn) for the η′ phase, it was estimated, based on density functional theory calculations from the literature, that the coexisting η phase assumes lower Cu content of Cu1.171Sn at 438 K and Cu1.174Sn at 445 K. In contrast, the lattice parameters of η′, generated at different temperatures, imply a largely temperature-independent composition of Cu1.20Sn. This leads to adjustments of the Cu-Sn phase diagram. [ABSTRACT FROM AUTHOR]

The temperature dependences of the damping constant and the relaxation time are calculated by using the Raman frequencies of a* and the lowest A1 (TO) phonons in the ferroelectric phase close to the ferroelectric-paraelectric transition in LiTaO3 (TC = 963 K). Both calculations are performed by considering the frequency as an order parameter for the pseudospin–phonon (PS) and the energy fluctuation (EF) models using the observed data from the literature. Values of the activation energies of this crystal are also deduced by using both models in this crystal. Our results show that the PS and EF models can describe the observed behavior adequately for the order–disorder transition in LiTaO3. [ABSTRACT FROM AUTHOR]

The temperature dependences of the damping constant and the relaxation time are calculated by using the Raman frequencies of a* and the lowest A1 (TO) phonons in the ferroelectric phase close to the ferroelectric-paraelectric transition in LiTaO3 (TC = 963 K). Both calculations are performed by considering the frequency as an order parameter for the pseudospin–phonon (PS) and the energy fluctuation (EF) models using the observed data from the literature. Values of the activation energies of this crystal are also deduced by using both models in this crystal. Our results show that the PS and EF models can describe the observed behavior adequately for the order–disorder transition in LiTaO3. [ABSTRACT FROM AUTHOR]

Through high-pressure, small-angle neutron scattering (SANS) and a random-phase approximation (RPA) theory based on a molecular model, we investigate the origin of the pressure responsiveness of a phase-segregating deuterated polystyrene-block-poly (2-ethyl hexyl acrylate) (d PS- b -PEHA) copolymer melt for use as a material for low-energy processing. The SANS intensities for the copolymer were measured over a temperature range at applied pressures between 0.1 and ∼83 MPa. The copolymer exhibited an order-disorder transition (ODT) and revealed baroplasticity, where its ODT was suppressed upon pressurization as Δ T O D T / Δ P ≈ -15.8 K/100 MPa to ease subsequent processing. Theory predicts that a disparity in the self interactions ε j j 's (Δ ε j j = ε P S − ε P E H A ) or a disparity in the compressibilities between blocks precisely yields the observed Δ T O D T / Δ P. The effective Flory-Huggins χ is argued to consist of the conventional enthalpic χ H and entropic χ S coming from Δ ε j j mediated by the copolymer bulk modulus. Pressure strengthens χ H due to densification, whereas the augmented bulk modulus reduces χ S. The diminution of χ S is shown to be the source of baroplasticity. Image 104 • Pressure response of a phase-segregating diblock copolymer melt is probed via high pressure small-angle neutron scattering. • Baroplasticity in the copolymer melt is investigated through a RPA theory combined with a molecular equation of state. • Observed baroplasticity is caused by disparity in self energies and the suppression of entropic part of c upon pressurization. [ABSTRACT FROM AUTHOR]

This study examines the self-assembly of colloidal particles with spherical dendritic brushes. The effective interaction between these particles was studied in Monte Carlo simulations of the Kremer–Grest model. Results confirmed the transferability of the effective potential at different temperatures. Using the potential of mean force obtained from Monte Carlo simulations, the structural formation of the system was studied in a three-dimensional system. The system is a crystalline state in the intermediate density range and exhibits re-entrant melting at much higher densities. Based on generalised local bond order analysis, a refined numerical method is proposed for analysing the structural formation of colloidal particles in three-dimensional systems. The numerical technique accurately reproduced the formation of the colloidal system. [ABSTRACT FROM AUTHOR]

Abstract Intermetallic γ-based titanium aluminides of Ti-45Al-7.5Nb have been subjected to high-pressure torsion (HPT) processing. Significant grain refinement has been achieved from ∼10 μm to ∼30 nm, leading to the improvement in both physical and mechanical properties. Complementary studies correlated the microstructure, phase transformation behavior and the enhancement of mechanical properties. Neutron and X-ray diffraction revealed that an ongoing order-disorder transformation occurs by HPT processing, resulting in large heterogeneous behavior between the surface-near and the median layers of the disk. While the γ-phase almost disappeared underneath the surface region, such order/disorder phase transformation consistently decreases towards the middle-thickness section of the samples. A low bulk texture index is consistent with grain rolling and swirling rather than slip deformation. Vickers micro-hardness indentation confirms the improvement of hardness from 308 H v to 605 H v. For the first time, the present work demonstrates heterogeneity in structural transformation, such as displacive transformation and order/disorder transformation, which can be compared to earlier reported inhomogeneity in mechanical properties and microstructure within bulk nanostructured materials that were processed by HPT. Graphical abstract Image 1 Highlights • Significant grain refinement is achieved in γ-based TiAl by HPT through 10 turns. • Neutron and X-ray analysis reveal order-disorder transformations in α 2 +γ TiAl by HPT. • High residual stresses remain within the γ-based TiAl disk after HPT. • A texture evolution is observed within the HPT-processed γ-based TiAl disk. • Evidence of heterogeneous deformation in a swirl flow has been revealed. [ABSTRACT FROM AUTHOR]

In this paper, Ce–Ho–Tb co–doped Bi 2 O 3 compositions were developed using the solid–state reaction method under atmospheric conditions. The XRD patterns confirm the stability of the cubic δ–phase in Ho and Tb–rich compositions but not in the Ce–rich ones, which consist of mixed phases, such as α and β. Peak shifting is additionally apparent in the magnified XRD diagram of primary peaks regarding the (111) diffraction plane, suggesting that the structural features change with doping. At 700 °C, the highest conductivity is found to be 0.30 S/cm for the composition 8Ce4Ho4Tb, and it is comparable to the single–doped (Bi 2 O 3) 0.80 (Er 2 O 3) 0.20 system at the same temperature. The FE–SEM images show the aggregation, particularly in images of Ce–rich compositions, implying that large cations have difficulty penetrating the lattice. The porosity over the surface is dense, particularly for Tb–rich compositions, indicating a decline in conductivity with doping. The cubic δ–phase of Bi 2 O 3 crystal, an excellent ion conductor, is capable of being stabilized at room temperature in Ho-rich compositions. Arrhenius plots of conductivity clearly show that the content ratios of 1:2:1, which is a specific ratio, play a key role in achieving the highest conductivity stable Bi 2 O 3 electrolytes. [Display omitted] • A high ion conductor, δ-Bi 2 O 3 phase was effectively stabilized in Ho and Tb-rich compositions. • The highest conductivity was determined to be 0.30 S/cm, which is greater than 20ESB electrolyte. • In several compositions, the order-disorder transition on the Arrhenius plots is noticeable. • The FE-SEM pictures revealed a local aggregation on the surface, particularly in the Ce-rich specimens. [ABSTRACT FROM AUTHOR]

Mechanical properties at elevated temperature, in modern alloys based on intermetallic phase Ni3Al are connected with phase composition, especially with proportion of ordered phase γ′ (L12) and disordered phase γ (A1). In this paper, analysis of one key systems for mentioned alloys - Ni-Al-Cr, is presented. A series of alloys with chemical composition originated from Ni-rich part of Ni-Al-Cr system was prepared. DTA thermal analysis was performed on all samples. Based on shape of obtained curves, characteristic for continuous order-disorder transition, places of course of phase boundaries γ′+γ / γ were determined. Moreover, temperature of melting and freezing of alloys were obtained. Results of DTA analysis concerning phase boundary γ′+γ / γ indicated agreement with results obtained by authors using calorimetric solution method.

The order–disorder temperature (To–d) of Ba[(Co0.6Zn0.4)1/3Nb2/3]O3 ceramics was determined via X-ray diffraction, Raman spectroscopy and differential thermal analysis, respectively. To–d was determined to be between 1425 and 1450 °C by a quenching method. The endothermic peak in the DTA curve shows the order–disorder transition. B2O3 was applied to tune the densification temperature (Ts) and tailor the microwave dielectric properties. The ordering degree and unloaded quality factor (Qf) are improved when Ts is reduced to 1400 °C at B2O3 content of 0.25 mol%. Ts is further decreased and the ordering degree and Qf are decreased when B2O3 content is increased to 0.5 mol%. The dielectric constant (εr) and temperature coefficient of resonant frequency (τf) decrease slightly with increasing B2O3 content. The optimum microwave dielectric properties (i.e., εr = 34.0, Qf = 50,400 GHz, τf = 5.5 × 10−6/°C) are obtained for the Ba[(Co0.6Zn0.4)1/3Nb2/3]O3-0.25 mol% B2O3 ceramics sintered at a lower temperature.

Phase transitions in the crystalline state of chiral sorbose were examined using precise heat capacity calorimetry and X-ray crystallography. The calorimetry established heat capacity below room temperature. Besides the known transition (main transition) at 199.5 K, the calorimetry detected plural thermal anomalies assignable to new phase transitions (around 210 K) and a glass transition (at ca. 120 K). The X-ray diffraction at low temperatures established the crystal structure of the lowest temperature phase. The identification of the broken symmetry upon the main transition solves an apparent contradiction that the structural disorder reported previously does not contribute seemingly to the symmetrization.