Crystal Configuration Research Articles

In-Plane Chirality Control of a Charge Density Wave by Means of Shear Stress.

The transition metal dichalcogenide 1T-TaS2 exhibits a Charge Density Wave(CDW) with in-plane chirality. Due to the rich phase diagram, the Ferro-Rotational Order (FRO) can be tuned by external stimuli. The FRO is studied by Angle-Resolved Photoelectron Spectroscopy (ARPES), Raman spectroscopy, and Selected Area Electron Diffraction (SAED). The in-plane chirality of the CDW is lost at the transition from Nearly-Commensurate (NC) to In-Commensurate (IC) phase and can be controlled by applying shear stress to the sample while cooling it through the transition from IC-CDW to NC-CDW. Based on these observations, a protocol is proposed to achieve reliable, non-volatile state switching of the FRO configuration in 1T-TaS2 bulk crystals. These results pave the way for new functional devices in which in-plane chirality can be set ondemand.

Manipulation of d-Orbital Electron Configurations in Nonplanar Fe-Based Electrocatalysts for Efficient Oxygen Reduction.

Manipulation of the spin state holds great promise to improve the electrochemical activity of transition metal-based catalysts. However, the underlying relationship between the nonplanar metal coordination environment and spin states remains to be explored. Herein, we report the precise regulation of nonplanar Fe atomic d-orbital energy level into an irregular tetrahedral crystal field configuration by introducing P atoms. With the increase of P coordination number, the spin magnetic moment decreases linearly from 3.8 μB to 0.2 μB, and the high spin content decreases linearly from 31% to 5%. Significantly, a volcanic curve between the spin states of Fe-based catalysts (Fe-NxPy) and oxygen reduction reaction (ORR) activity has been unequivocally established based on the thermodynamic results. Thus, the Fe-N3P1 catalyst with a 19% medium spin state experimentally exhibits the optimal reaction activity with a high half-wave potential of 0.92 V. These findings indicate that regulating electron spin moments through coordination engineering is a promising catalyst design strategy, providing important insights into spin catalysis.

Deciphering the structural origin for the remarkable CO oxidation activities of the CuO-based catalysts with diverse morphological CeO2 supports

In this work, octahedral, cubic, particle-like, spherical and rod-shaped nano-CeO2 supports were synthesized by hydrothermal method. CuO/CeO2 catalysts were then prepared via an ultrasonic-assisted impregnation method, employing these differently shaped CeO2 supports. The resulting catalysts were tested for their performance in CO oxidation. The findings revealed that the CuO active sites significantly influenced the oxygen storage and release capacity of CeO2, thereby improving its catalytic activity for low-temperature CO oxidation. The key factors affecting the CO oxidation performance of CuO/CeO2 catalysts with different CeO2 morphologies were investigated through various characterizations. It was found that the specific surface area was not the primary factor in determining catalytic activity. Instead, the exposed crystal planes played a crucial role. By adjusting the crystal plane exposure of CeO2, the supported 1CuO/CeO2 catalysts exhibited different crystal surface configurations. Notably, the 1CuO/CeO2-S catalyst, with exposed (100) and (110) crystal planes, and the 1CuO/CeO2-P catalyst, with exposed (111), (100), and (110) planes, exhibited higher surface defect concentrations. This increased defect concentration facilitated the formation of Cu+ species, enhancing the redox properties and further improving the overall catalytic performance of CO oxidation.

Temperature Induced, Reversible Switching of Ferro-Rotational Order Coupled to Superlattice Commensuralibity.

High-quality 1T-TaS2 crystals are investigated by angle-resolved photoelectron spectroscopy, Raman spectroscopy, and low-energy electron diffraction. The Ferro-Rotational Order (FRO) of the charge density wave switches configuration at the transition between the commensurate and the nearly commensurate phase. This process requires samples without built-in or externally induced strain. Moreover, temperature gradients generated by a focused laser beam can be employed in order to freeze the in-plane chirality. Based on such observations, we propose a protocol to obtain durable and nonvolatile state switching of the FRO configuration in bulk 1T-TaS2 crystals.

Investigation of an annular photonic crystal sensor for real-time monitoring of calcium carbonate scales in water distribution systems

This research exhibits a new configuration of photonic crystals known as annular photonic crystals (APCs) for real-time detection of calcium carbonate (CaCO3) scale in the water pipeline. The proposed sensor features a circular arrangement of porous silicon materials with varying levels of porosity. A central defect layer is incorporated into the design to capture the target analyte, allowing it to detect changes in the refractive index caused by scale formation. To analyze the reflectance spectrum of this structure, a modified transfer matrix method is utilized. An extensive optimization process is conducted based on the characteristics of the defect mode, focusing on various geometric parameters, including layer thickness, porosity levels, core circle radius, and structural periodicity, to achieve optimal sensor performance. The simulation outcomes revealed that at the optimized structure parameters, the sensor offers a remarkable QF, sensitivity, and FoM of 1215, 176.85 nm/RIU, and 350.5 1/RIU, respectively. Moreover, the proposed structure is simple, cost-effective, and compact, which makes it an ideal candidate for the detection of calcium carbonate scales formed in pipes and devices in water supply networks.

Nano and micro-structural complexity of nematic liquid crystal configurations

Of our interest are frustration-driven pattern generating mechanisms in systems which in bulk equilibrium display spatially homogeneous long-range orientational order in absence of perturbations. As testbed material, we select thermotropic nematic liquid crystals. In bulk, they exhibit weakly discontinuous order–disorder phase transformation on varying temperature where the ordered nematic phase features spatially uniform axial order along an arbitrary symmetry breaking direction. However, due to continuous symmetry breaking (CSB) the established order is extremely susceptible to various perturbations which are in real systems in general always present. We theoretically illustrate how diverse complex patterns could be excited. Particularly intriguing configurations could appear if topological defects are present that could be generated via CSB. Our analysis is based on a relatively simple Lebwohl-Lasher-type model in which we could get analytical insight into phenomena of our interest. Using it we illustrate history dependent early stage isotropic-nematic phase evolution and final patterns in presence of “impurities” (e.g., nanoparticles). We show how characteristic effective interaction characteristics predict qualitatively different emerging patterns. Our analysis is based on CSB which is ubiquitous in nature. Consequently, demonstrated mechanisms are expected to manifest also in other condensed matter systems whose ordered phase is formed via CSB. We illustrate how kinetics and impurities could impact key structural properties of the systems of our interest.

Crystal Structure and Electron Configuration of {MNO}8 Heme Complexes.

Although research on nitrosyl (NO) heme complexes and their one-electron reduced form, nitroxyl (or nitroxyl anion, NO-) derivatives, has been going on for decades, there are still disagreements about the electrical configuration of nitroxyl complexes, and the majority of the work on this topic is based on theoretical calculations. Following the initial nitroxyl iron porphyrin crystal structure, we present two further polymorphic forms of [CoCp2][Fe(TFPPBr8)(NO)]. Using the same completely halogenated porphyrin ligand, we also present two polymorphic forms of nitrosyl cobalt(II) complexes, which are another sort of {MNO}8 structure. In addition to the EXANES and EPR studies of these {FeNO}7 and {CoNO}8 complexes, the {FeNO}8 [CoCp2][Fe(TFPPBr8)(NO)] complex is also investigated by temperature-dependent Mössbauer experiments for the first time with the {FeNO}7 precursor as a control sample. The analysis of the Mössbauer and crystal structural parameters between these two types of {MNO}8 (M = Fe or Co) species and previously reported analogous ones allow us to conclude that the electronic configuration of [Fe(TFPPBr8)(NO)]- is best described as an intermediate between low-spin Fe(II)-NO- and Fe(I)-NO•.

Методы монохроматизации синхротронного излучения (обзор исследований)

The paper presents an analysis of studies related to the monochromatization of X-ray radiation (XR) at synchrotron radiation sources. A review of monochromators based on of X-ray diffraction on crystals is given, and the peculiarities of their technical realization are considered. The ideas about monochromators which include multilayer structures are examined. The authors also study technical problems arising during designing devices and its possible solutions. Introduction. The possibilities of using X-rays in scientific research are described. The high efficiency of synchrotron radiation sources is noted, and its characterization is given. Elementary information about diffraction of X-rays. The paper describes the properties of X-ray radiation and the possibilities of its using while studying various materials. Degree of monochromaticity. The degree of monochromaticity is an important characteristic of the synchrotron radiation (SR). Depending on the width of the wavelength band, “white”, “pink” and monochromatic beams are distinguished. Monochromators based on multilayer structures are used to obtain “pink” beams. Monochromatic radiation is formed using monocrystals. When conducting experiments with “white” beams, the monochromator is not used. The authors also describe the factors that violate the ideal fulfillment of the Wolf-Bragg condition and affect the degree of monochromaticity (heat, vibration). The reflectivity values at different beam grazing angles are noted to have different widths. Monochromators based on multilayer structures. Periodic structures combining thin layers of two heterogeneous materials make it possible to obtain “pink” beams. The wavelength bandwidth of such devices is one or two orders of magnitude greater than that of monochromators using crystals as optical elements. Configurations and geometry of optical elements. There are two types of X-ray diffraction on a crystal: Bragg and Laue diffraction. Bragg diffraction refers to reflective geometry, Laue diffraction is based on the passage of beams through the crystal. The section provides examples of monochromators with different configurations of crystals and X-ray mirrors. The arrangement of optical elements in a monochromator plays an important role in the geometry of the beam path. When designing monochromators, it is necessary to take into account the methods of fixation and orientation of the rotation axes of optical elements. Examples of monochromators with different configurations of crystals and X-ray mirrors are given. Focusing monochromators. It is possible to provide sagittal and meridional types of deformation by bending the optical element of the monochromator. Due to the curved crystal surface the beam is not only monochromatized but also subjected to focusing. Modern focusing monochromators are equipped with adaptivity elements allowing it to change the radius of curvature of the optical element. Examples of practical realization of such monochromators are presented. Thermal load of SR on optical elements. The SR is characterized by high brightness and a wide spectrum of emitted wavelengths. While operating optical elements of SR stations absorb a large amount of thermal power. The problems of heat dissipation have a fundamental influence on the quality of synchrotron radiation monochromatization. Additional information about monochromators. Examples of special design solutions for monochromators are given. Conclusion. The design of monochromators is relevant to the synchrotron radiation source 4+ “SKIF” under construction in Novosibirsk.

Electrically tunable metasurface in TN LC configuration with enhanced quality factor and metaatom-induced alignment.

Dynamic metasurface with subwavelength dimensions has emerged as a key optical technology in recent years. Although various active tuning mechanisms are being proposed, liquid crystal-based dynamic metasurface remains attractive due to its large index variation, electrical tunability, reliability, and mass fabricability. In this work, we report a dynamic metasurface for amplitude modulation in reflection, with twisted nematic liquid crystal configuration to reduce broadband reflection in the off state. The metasurface consists of coupled subwavelength grating fingers, which provide alignment for the liquid crystal without the need for an additional alignment material or process. The alignment of liquid crystal materials was examined between crossed polarizers, and the twist of nematic liquid crystal was confirmed. The coupled grating fingers exhibit a resonance quality factor of 27 at telecommunication wavelength and an amplitude modulation depth of 8 times of the minimum at 1630 nm. This work highlights the potential of liquid crystal-based tunable metasurface, combining polarization control via liquid crystal and spectrum control via metasurface. Furthermore, it also shows a way in which the interaction between liquid crystal and metasurface is used for an alignment layer-free cell assembly process.

Comparison on Hysteresis Loops and Dislocation Configurations in Fatigued Face-Centered Cubic Single Crystals

The aggregation and evolution of dislocations form different configurations, which are the preferred locations for fatigue crack initiation. To analyze the spatial distribution of the same dislocation configuration and the resulting configuration morphologies on different observation planes, several typical hysteresis loops and dislocation configurations in fatigued face-centered cubic single crystals with various orientations were compared. The crystal orientations of these specimens were determined by the electron back-scattering diffraction technique in a Cambridge S360 Scanning Electron Microscope. It is well known that dislocation ladder and wall structures, as well as patch and vein structures, are distributed on their respective observation planes, (12¯1) and (111). These correspond to the point defect direction and line defect direction of dislocations, respectively. Therefore, the wall structures on the (12¯1) and (111) planes consist of point defects and line defects, which can be defined as point walls and line walls, respectively. Furthermore, the walls on the (12¯1) plane consist of Persistent Slip Band ladders connected with each other, corresponding to the formation of deformation bands. The evolution of dislocation patterns follows a process from patch to ladder and from vein to wall. The formation of labyrinths and dislocation cells originates from the activation of different secondary slip systems. In one word, it can help us better understand the physical nature of metal fatigue and failure by studying the distribution and evolution of different configurations.

Bridging micro nature with macro behaviors for granular thermal mechanics

The connection between micro-level characteristics and macroscopic properties in granular heat transfer and mechanics is fundamental and crucial. This study proposes a novel discrete element approach incorporating granular heat transfer, contact bonding, and granular stress tensor models to investigate the mechanical and thermal responses of continuum media composed of constituent spheres. Eight benchmark tests were devised to bridge the long-standing gap between micro and macro properties in granular materials. Through these tests, the numerical solutions obtained from discrete element modeling match well with existing analytical or finite element solutions derived from continuum-based theory. This validation underscores the rationality and reliability of the granular heat transfer model, contact bonding model, and granular stress tensor model. Moreover, the study highlights the consistency between continuum-based theory and discontinuum-based theory. A minor distinction between continuum-based models and discrete element models emerges near the boundaries due to variations in the specification of boundary conditions. This discrepancy can be clarified by Saint-Venant's Principle, thus validating the accuracy of the microscale heat transfer and mechanics theory for granular materials. Five mono-disperse packing structures, including simple cubic (SC), body-centered cubic (BCC), face-centered cubic (FCC), hexagonal close packing (HCP), and random packing (Random), were further analyzed to examine their influence on heat transfer performance. Numerical results reveal that higher coordination numbers and solid volume fractions correspond to higher apparent thermal conductivity of granular assemblies, thus elucidating the connection between micro packing configurations and macroscopic heat transfer properties. The apparent thermal conductivity for different crystal configurations follows the sequence: HCP ≒ FCC > BCC ≒ Random > SC. To improve the accuracy and physical relevance of the proposed model, the effect of particle contact area needs to be further incorporated into the granular heat transfer model.

Garnet-structure phosphors with ultra-high color purity red emission for potential warm WLED and flexible-transparent displays

Red-emitting phosphors play a pivotal role in the field of lighting technologies. This study introduces an innovative class of Li6SrEu2Sb2O12 garnet-structured phosphors, distinguished by the resistance to concentration quenching. A comprehensive examination of the crystal structure, electronic configuration, and photoluminescence characteristics has been conducted. Notably, the doping Eu3+ ions and their doping concentrations barely affected the crystal structure and morphology, and the band gap slightly decreased as the doping concentration increased. Interestingly, the obtained samples exhibit an ultra-high color purity, good thermal stability (78.60 % at 423 K), and suitable internal photoluminescence quantum yield (44.18 %). Consequently, a phosphor-converted white LED has been successfully fabricated, which boasts an outstanding correlated color temperature of 3271 K. Beyond conventional application, this research also introduces the concept of innovative flexible-transparent displays harnessing the phosphor film. Overall, this work has synthesized a groundbreaking red-emitting phosphor, poised to enhance traditional lighting sources and potentially pave the way for new applications in the field of advanced optical displays.

A kind of single-phase full bandgaps phononic crystals and experimental evidence

The exceptional performance of locally resonant phononic crystals (PCs) in vibration attenuation and noise reduction within nuclear power plants has garnered widespread attention in scholarly circles. To address the need for improved predictive accuracy in substrate structures characterized by significant flexibility, a one-dimensional mechanical model rooted in the mass-spring chain paradigm has been established. This model offers a straightforward and accurate means of predicting the lower and upper frequencies of the initial bandgap within locally resonant phononic crystals. Moreover, the dynamic model elucidates modal characteristics and vibrational responses inherent to locally resonant phononic crystals. Utilizing the proposed model, a singular-phase phononic crystal structure boasting full bandgaps has been devised. This structure facilitates the omnidirectional acquisition of locally resonant bandgaps across an exceedingly low-frequency spectrum through the incorporation of cantilever beam elements. Such a design holds immense promise within the realm of large-scale mechanical vibration isolation. As a means of validation, steel samples embodying this phononic crystal model were fabricated. Experimental results demonstrated an insertion loss of approximately 18.67 dB, affirming the vibration isolation efficacy of the singular-phase phononic crystal configuration.

Lycium barbarum pulp addition improves the dough properties and gluten protein structure

This study investigated the effects of Lycium barbarum pulp (LBP) on the properties of mixed dough and gluten protein. The results showed that appropriate addition of LBP (5 %) significantly improved the performance of the dough, promoted the aggregation of gluten protein, enhanced the water binding ability, and delayed the gelatinization of starch during cooking. Compared with the control group, the peak temperature (Tp) of the LBP sample gradually increased from 63.23 °C to 65.56 °C, the expansion force reduced by about 21.56 %, the absolute Zeta potential lowered by about 18.4 %, and the α -helix content and β -folding increased by 32.36 % and 10.23 %, respectively, indicating the more orderly and stable overall structure. However, LBP did not change the crystal configuration of starch and still showed typical type A line diffraction. Moreover, the addition of LBP increased the polyphenol content, which further improved the antioxidant properties and provided the possibility to improve the health potential of the flour.

Ultrahigh-[formula omitted] Fano resonance in a cavity-waveguide coupled system based on second-order topological photonic crystals with elliptical holes

We present a novel configuration of second-order topological photonic crystal (SOTPC) comprising interconnected dielectric material with elliptical air holes. Based on this SOTPC design, we construct a topological corner state (TCS) cavity and a topological edge state (TES) waveguide. Through the coupling of the TCS cavity with the TES waveguide, we establish a topological cavity-waveguide coupled system (TCWCS) that exhibits an ultrasharp asymmetric topological Fano resonance. Numerical simulations demonstrate that the proposed TCWCS achieves an exceptionally high quality factor exceeding 108, surpassing previously reported results by several orders of magnitude. Moreover, the refractive index sensing application implemented with TCWCS shows a sensitivity of 278 nm/RIU and a figure of merit surpassing 107 1/RIU. Notably, our simulations reveal that the lineshape and quality factor of the Fano resonance, as well as the index sensing performance in the TCWCS, are highly robust against structural defects. The demonstrated capabilities of the TCWCS open up avenues for further exploration and development in the field of topological photonics based on our proposed SOTPC.

NH2(CH3)2CuCl3 Organic-Inorganic Hybrid Perovskite: Consideration to Crystal Structure, Thermodynamics, and Structural Molecular Dynamics.

The crystal structure of NH2(CH3)2CuCl3, an organic-inorganic hybrid perovskite, undergoes a phase transition from triclinic to monoclinic at the phase transition temperature T C of 287 K. We investigated the temperature dependencies of NMR chemical shifts and spin-lattice relaxation time T 1ρ to gain insights into the structural geometry and molecular dynamics during the transition from phase II to phase I at high temperatures. Analysis of the 1H and 13C NMR chemical shifts of the cation revealed a continuous change in the surrounding structural geometry with temperature, without any anomalous changes around T C. The sudden decrease in T 1ρ values from low to high temperatures indicated a significant variation in proton and carbon dynamics at T C, arising from the slowing motion of molecular dynamics across the phase transition. The activation energies E a obtained from the temperature dependence of T 1ρ for 1H and 13C were larger in phase I than in phase II. This suggests that molecular motions in phase II exhibit a higher degree of freedom compared to those in phase I, where they are more constrained. These findings on NH2(CH3)2CuCl3 are presented to enhance its potential applications by elucidating the crystal configuration and structural molecular dynamics of ABX3 type compound.

Inverse design of nonlinear phononic crystal configurations based on multi-label classification learning neural networks

Abstract Phononic crystals, as artificial composite materials, have sparked significant interest due to their novel characteristics that emerge upon the introduction of nonlinearity. Among these properties, second-harmonic features exhibit potential applications in acoustic frequency conversion, non-reciprocal wave propagation, and non-destructive testing. Precisely manipulating the harmonic band structure presents a major challenge in the design of nonlinear phononic crystals. Traditional design approaches based on parameter adjustments to meet specific application requirements are inefficient and often yield suboptimal performance. Therefore, this paper develops a design methodology using Softmax logistic regression and multi-label classification learning to inversely design the material distribution of nonlinear phononic crystals by exploiting information from harmonic transmission spectra. The results demonstrate that the neural network-based inverse design method can effectively tailor nonlinear phononic crystals with desired functionalities. This work establishes a mapping relationship between the band structure and the material distribution within phononic crystals, providing valuable insights into the inverse design of metamaterials.

Study on vibration bandgap characteristics of a cantilever beam type local resonance unit

This article proposes a novel phononic crystal configuration consisting of a through-hole cantilever beam and a mass block, and conducts numerical analysis and experimental verification on the bandgap characteristics of a two-dimensional periodic array plate containing this configuration. The results indicate that there are multiple bending wave band gaps in the proposed structure, and the formation of the bandgap is due to the coupling between elastic waves in the matrix and the resonance characteristics of the local resonant structure. The width of the bandgap is related to the coupling strength. Further research has also found that the proportion of effective mass of the mode is a criterion for determining whether the mode generates a bandgap. At the same time, the regulation of band gaps by the cell constants and geometric parameters of local resonance units was studied. Based on the above research, by improving the original local resonance structure, more abundant bandgap features were obtained, providing a feasible approach for the design of broadband bandgaps. Finally, the vibration transmission rate of the finite period structural plate was obtained through simulation calculations and experiments, and its attenuation frequency band was basically consistent with the bandgap range, indicating that the structure has good low-frequency vibration reduction performance, which has broad engineering application prospects in the field of vibration and noise reduction.

Influence of crystalline structure on creep resistance capability in semi-crystalline Polymers: A coarse-grained molecular dynamics study

In this study, we investigated the intrinsic correlation between the crystal configuration and persistent mechanical stability of semi-crystalline polymers. The creep resistances of microstructures with different grain sizes and the same crystallinity were evaluated using coarse-grained molecular dynamics simulations. It was demonstrated that under tensile loading at constant pressure, microstructures with larger grains have more pronounced resistance to molecular rearrangement and significantly delay creep deformation. The improved creep resistance can be attributed to two factors. First, larger crystal sizes result in an increased moment of inertia, reducing the angular velocity required for the rotational rearrangement of the crystalline phase. Second, the elongated crystalline stems enhance the resistance to intermolecular slippage, elevating the strain energy necessary to disrupt the crystalline structure. These findings reveal the molecular basis of creep resistance at the nanoscale and highlight the pivotal role of crystal morphology in enhancing the long-term mechanical integrity of polymers.

Cross-stacking crystal structural configuration of integrated cathode materials for proton-conducting solid oxide fuel cells

Cross-stacking crystal structural configuration of integrated cathode materials for proton-conducting solid oxide fuel cells