Crystal Configuration Research Articles

Analysis of a gas sensor based on one-dimensional photonic crystal structure with a designed defect cavity

A symmetric one-dimensional photonic crystal configuration with defect layer is proposed for an optical gas sensor based device application. Here, Silicon and Si3N4 are considered as materials of dielectric layers with zero value of extinction coefficient in the wavelength range of concern. The transmission of PC configuration is estimated using the transfer matrix approach in case of configuration with and without defect, and the infiltrated gas is treated as defect layer. On the basis of the defect mode’s wavelength, gas can be determined. In addition, quality factor and sensitivity of the device are improved due to the variation of refractive index of layer B, thickness of defect, angle of incidence and the number of unit cells on either side of defect layer. By making analysis of the effect of these parameters on the sensitivity and quality factor, interesting results have been obtained and conclusions drawn. We have also proposed and investigated a symmetric structure with defect made with a single material to improve optical sensing parameters. Further for the sake of comparison, the various gases are used to show improved sensing characteristics for respective gases, which can be used to determine gas. It is inferred that such refractive index optical sensor based on defect mode position is highly sensitive and offers precise optical sensing characteristics and possibly find applications in gas detection.

Crystal configuration and luminescence dynamics of highly efficient green-glimmering vanadate-based Ca9Gd(VO4)7: Er3+ nanomaterials pertinent for next-generation illumination applications

Crystal configuration and luminescence dynamics of highly efficient green-glimmering vanadate-based Ca9Gd(VO4)7: Er3+ nanomaterials pertinent for next-generation illumination applications

DETERMINATION OF THE ABSOLUTE CONFIGURATION OF MONOATOMIC CHIRAL CRYSTALS USING THREE-WAVE X-RAY DIFFRACTION

Many molecules and crystals are chiral, i.e., can exist as right- and left-handed mirror isomers. It is shown that the absolute configuration of monoatomic chiral crystals, including selenium, tellurium, and b-manganese, can be determined using multi-wavelength diffraction of circularly polarized X-ray radiation.

Carnauba Wax and Beeswax as Structuring Agents for Water-in-Oleogel Emulsions without Added Emulsifiers.

This research aims to explore the potential of waxes as ingredients in the formulation of food-grade water-in-oleogel emulsions without added emulsifiers. The effects of the wax type, wax concentration and water concentration were tested on systems containing exclusively water, sunflower oil, and wax. Beeswax and carnauba wax were used in the formulation of water-in-oleogel emulsions with 20%, 30% and 40% w/w of water. For the continuous phase, three different levels of wax were used, namely 50%, 100%, and 150% of the critical gelling concentration. More specifically, carnauba wax emulsions were prepared at 2.5%, 5.0% and 7.5% of wax, while concentrations of 0.75%, 1.5% and 2.25% of wax were utilized for the beeswax experiments. Samples were assessed over time regarding stability, rheology and microstructure (polarized light microscopy, cryo-scanning electron microscopy and confocal scanning laser microscopy). Our findings suggest that, if present in sufficient concentration, carnauba wax and beeswax can stabilize emulsions in the absence of additional added emulsifiers. The resulting systems were inherently different based on the wax used, as crystal morphology and droplet configurations are determined by wax type. The yield strain was dictated by the nature of the wax, while the complex modulus was mostly influenced by the wax concentration. To test the scaling-up potential, systems were crystallized in a pilot-scale scraped surface heat exchanger, resulting in notably smaller crystal sizes, reduced rigidity and a storage stability of over one year. These findings represent a starting point for the formulation of scalable water-in-oleogel emulsions without added emulsifiers.

Local Atomic Configurations in Intermetallic Crystals: Beyond the First Coordination Shell.

We have used a combined geometrical-topological approach to analyze 21,697 intermetallic crystal structures stored in the Inorganic Crystal Structure Database. Following a geometrical scheme of close packing of balls, we have considered the three most typical polyhedral atomic environments of the icosahedral, cuboctahedral, or twinned cuboctahedral shape as well as multi-shell (up to four shells) local atomic configurations (LACs) based on these cores in 10,657 unique crystal structure determinations. In total, half of intermetallic structures have been found to contain one of these configurations, with the icosahedral LACs being the most frequent. We have revealed that even a two-shell configuration strongly predetermines the overall connectivity (topological type) of an intermetallic crystal structure. The chemical and stoichiometric composition of the multi-shell LACs generally obeys the close-packing model: the number of atoms in the subsequent shells (Nk) varies around the value Nk = 10k2 + 2, which is valid for the same size atoms, to reach the densest packing for the kth shell. Deviations from the revealed regularities often indicate inconsistencies in the crystallographic information, unusual features of the structure, or the existence of more stable phases that can be used for the validation of experimental and modeling data.

Targeted Discovery of Low-Coordinated Crystal Structures via Tunable Particle Interactions

Particles interacting via isotropic, multiwell pair potentials have been shown to self-assemble into a range of crystal structures, yet how the characteristics of the underlying interaction potential give rise to the resultant structure remains largely unknown. We have thus developed a functional form for the interaction potential in which all features can be tuned independently. We perform continuous parameter space searches by systematically changing pairs of parameters, controlling the various features of the interaction potential. By enforcing a repulsive first well (controlling particle interactions of the first neighbor shell), we stimulate the formation of low-coordinated assemblies. We report the self-assembly of 20 previously unknown crystal structure types, 14 of which have low coordination numbers. Despite limiting the search to a small region of the vast parameter space of possible particle interactions, a wealth of complexity and symmetry is apparent within these crystal structures, which include clathrates with empty cages and low-symmetry structures. Our findings suggest that an unknown number of previously undiscovered crystal structure configurations are possible through self-assembly, which can serve as interesting design targets for soft condensed matter synthesis.

Evolution of phase structure and magnetic property with Mn content and heat treatment in Fe3-xMnxGa alloy

The evolution of structure and magnetic property with Mn content and different heat- treatment in Fe3-xMnxGa alloy has been investigated in this study. First-principles calculations suggest that the small energy difference between the different structures of Fe3Ga and Fe2MnGa alloys leads to the instability of them. The phase transformation for samples being quenched from 623 K, 883 K, 1073 K and the ribbons are studied with X-ray diffraction. Body-centered cubic (bcc), face-centered cubic (fcc) and hexagonal structures are observed and the schematic phase diagram is given in this paper. Together with the theoretical calculation moments for Fe3Ga and Fe2MnGa with different crystal structures and magnetic configurations, the magnetic properties are discussed. The saturation magnetization MS of bcc and hexagonal Fe3-xMnxGa samples at 5 K gradually decreases with increasing Mn content, which can be attributed to the increase of the fraction of Fe-Mn antiferromagnetic (AFM) coupling. In fcc Fe2MnGa, with the increase of quenching temperature from 623 K to 1073 K, more ferrimagnetic (FIM) coupling phase with higher energy is formed, showing a decrease of MS and unsaturation of magnetization under the test magnetic field in MH curve. A magnetic field induced AFM to FIM state transition is found in Fe2MnGa alloy with L12 type of atomic disorder when quenched from 1073 K. The tunable structure and magnetic properties make it has the potential applications in versatile material field.

Noble metal nanostructures for various applications

Noble metal nanostructures have been of immense research interest in the past few years because of their amazing properties. Noble metal nanostructures have exceptional electronic, optical, and catalytic properties, and show remarkable photoelectric activity. They have many technological and electrical applications in the electromechanical system as they connect the molecular circuits internally. Tuning of properties with the shape, size, and surface composition of crystal configuration is the unique property of noble metal nanostructures. Noble metal nanostructures when synthesized in controlled morphological conditions can be used in various fields. Controlled synthesis of noble metal nanostructures with specific morphologies, and low toxicity is emerging as an exciting new field with huge scope. Here we review the noble metal nanostructures and their applications in different fields like electro catalysis, clean energy, photo-thermal therapy, infrared biosensing, bioimaging etc. SERS or surface-enhanced Raman scattering is the emergent field of application of noble metal nanostructures. However the areas of application are extremely diverse but our main focus is on SERS (Surface Enhanced Raman Scattering), biosensing, and the latest advances in these fields. The fast-growing research in the field of noble metal nanostructures will open a modern era for the expansion of small and ultra-fast devices.

Polar Layered Bismuth‐Rich Oxyhalide Piezoelectrics Bi4O5X2 (XBr, I): Efficient Piezocatalytic Pure Water Splitting and Interlayer Anion‐Dependent Activity

AbstractPiezocatalytic pure water splitting for H2 evolution carries the virtues of efficacious utilization of mechanical energy, easy operation, and high value‐added products, while lacking desirable piezoelectrics for high chemical energy production. Here, two polar layered bismuth‐rich oxyhalides Bi4O5X2 (XBr, I) thin nanosheets (≈4 nm) are first exploited as efficient piezocatalysts to be capable of dissociating pure water. The unique asymmetrical layered structures of Bi4O5X2 (XBr, I) composed of the interleaved [Bi4O5]2+ layer and double X− ions slabs along the [1 0 1_] orientation cause large intrinsic dipole moment, excellent piezoelectricity and easy deformation. Without any cocatalyst and sacrificial agent, Bi4O5Br2 and Bi4O5I2 thin nanosheets display remarkable piezocatalytic H2 production rate of 1149.0 and 764.5 µmol g−1 h−1, respectively, standing among the best piezocatalysts, accompanied by H2O2 and hydroxyl radicals (·OH) as oxidative products. The smaller radius and higher electronegativity of interleaved Br than I cause a more strongly polar crystal structure in Bi4O5Br2, contributing to the higher piezocatalytic activity compared to Bi4O5I2. This study broadens the scope of piezoelectric materials applied to sustainable energy catalysis by efficiently converting mechanical energy and illustrates the importance of crystal configuration and composition in fabricating efficient piezocatalytic systems.

Formation Mechanism of Elemental Te Produced in Tellurite Glass Systems by Femtosecond Laser Irradiation.

The formation of elemental trigonal tellurium (t-Te) on tellurite glass surfaces exposed to femtosecondlaser pulses is discussed. Specifically, the underlying elemental crystallization phenomenon is investigated by altering laser parameters in common tellurite glass compositions under various ambient conditions. Elemental crystallization of t-Te by a single femtosecond laser pulse is unveiled by high-resolution imaging and analysis. The thermal diffusion model reveals the absence of lattice melting upon a single laser pulse, highlighting the complexity of the phase transformation. The typical cross-section displays three different crystal configurations over its depth, in which the overall thickness increases with each subsequent pulse. The effect of various controlled atmospheres shows the suppressing nature of the elemental crystallization, whereas the substrate temperature shows no significant impact on the nucleation of t-Te nanocrystals. This research gives new insight into the elemental crystallization of glass upon femtosecond laser irradiation and shows the potential to fabricate functional transparent electronic micro/nanodevices.

Engineering CeO2 configurations to regulate the CuOx dispersion and switch pathways of preferential CO oxidation

Constructing highly dispersed catalysts is of tremendous interest for catalysis. However, the mechanism and avenue to tune dispersive behavior and thus reactivity of supported catalysts is still facing challenges. Herein, we manipulate crystal plane-induced CeO2 configurations toward improved CuOx dispersion, and investigate the structural evolution and reaction intermediates during the CO preferential oxidation over CuOx/CeO2 catalysts. Results demonstrate that the optimal atomic arrangement appears on nanosphere-shaped CeO2 with exposed {111} and {100} facets in contrast to nanorod-shaped CeO2 exposed {100} and {110} facets and nanowire-shaped CeO2 exposed {110} facets. By combining theoretical simulations and systematic characterizations including in situ DRIFTS, in situ Raman spectra and XAFS, it reveals the optimal catalyst favors the formation of highly dispersed CuOx with surface-enriched Cu+, which is highly active site for catalysis. Furthermore, in situ Raman spectra provide direct evidence that the optimal support configuration facilitates the lattice oxygen extraction, thus promoting the carboxyl pathway.

Active basis choice for quantum key distribution with entangled states

Entangled quantum key distribution (QKD) is a promising way to generate pairs of unconditionally secret keys. In this paper we review possible realizations of entanglement-based QKD and assess their feasibility in terms of implementation complexity and provided security. We also propose a novel active basis choice approach that enables to use only one single-photon detector per user. The paper provides all necessary details including the required electro-optic crystal configurations to implement such a scheme experimentally.

Investigation on band gap mechanism and vibration attenuation characteristics of cantilever-beam-type power-exponent prismatic phononic crystal plates

This study proposes a novel phononic crystal (NPC) configuration composed of power-exponent prismatic phononic crystal (EPC) and cantilever beams to address the vibration problem of the ship plate structure. Through the dispersion curve, it is found that NPC has complete flexural band gaps of low-, medium-, and high-frequency. The medium-frequency and high-frequency band gaps are the coupled band gaps induced by local resonance under the superimposition between the resonance of cantilever beams and the energy concentration effect in the primary structure. It is found that the addition of cantilever beam can make EPC produce low-frequency, and medium-frequency band gaps and broaden high-frequency band gap. Changing the parameters of the cantilever beam can adjust the low-, medium-, and high-frequency band gaps at the same time. Changing the parameters of the power index prism can adjust the medium-frequency and high-frequency band gap without changing the low-frequency band gap. The present simulation and model tests validated the above conclusions. Compared with the traditional embedded ABH model, NPC cannot weaken the structural strength with greater flexibility in application, suggesting broad application prospects in ship structure engineering. The present research results can support the vibration control of ship structures.

High-power femtosecond regenerative amplifier based on Yb:CaYAlO4 dual-crystal configuration.

A thermal lens insensitive regenerative amplifier (RA) with a dual Yb:CaYAlO4 (Yb:CYA) crystal configuration for extending gain spectra is demonstrated for the first time, to the best of our knowledge. By orthogonalizing the orientation of two a-cut Yb:CYA crystals in one RA, the Q switched spectrum with a full width at half maximum of 15.4 nm is generated, which is 1.5 and 1.6 times of the Q switched spectral bandwidth with π- and σ-polarization, respectively. With chirped pulses injection, this RA can deliver laser pulses with an average power exceeding 10 W at the repetition rate of 20-800 kHz and pulse energy of 1.5 mJ at 1 kHz. This is the highest average power from the Yb:CYA RA to the best of our knowledge. Finally, compressed pulses of 163 fs with 92% overall efficiency are realized. Thanks to the heat insensitive cavity design and excellent thermodynamic properties of the Yb:CYA crystal, the output laser beam is close to the diffraction limit with an M2 value of 1.07 × 1.07.

Viewing high entropy alloys through glasses: Linkages between solid solution and glass phases in multicomponent alloys

High entropy alloys (HEAs) represent highly promising multicomponent crystals that form concentrated solid solutions (CSSs) and may violate traditional thermodynamic rules of mixing, ultimately leading to excellent physical properties. For a deeper understanding, we investigate seven CSSs, including Co-Cr-Ni-Fe-Mn elements, at experimentally relevant compositions and conditions, through molecular simulations, and we use 1-1 comparisons to corresponding glass state characteristics, attained through rapid cooling protocols. We determine the behavior of various structural features, including the configurational entropy for a set of CSSs in their crystalline and vitreous states numerically. We employ swap Monte Carlo (MC) simulations, in combination with the reversible scaling method, to efficiently compute the configurational entropy (${S}_{\text{conf}}$), and show that the entropic rule of mixing is not always adequate for predicting alloy formation. We study the stability and formability of crystalline solid solutions, as well as glasses, while following the thermodynamics of ${S}_{\text{conf}}$. An apparent entropic similarity between CSSs and corresponding glasses leads us to use a Kauzmann-like ansatz, relating the CSSs at ${S}_{\text{conf}}\ensuremath{\rightarrow}0$ with the emergence of a CSS order-disorder transition, at temperature ${T}_{OD}$. In the context of glasses, a comparison between kinetic and thermodynamic fragilities allows the association of sluggish diffusion onset to a drop in ${S}_{\text{conf}}$ at ${T}_{K}$. Analogously, we classify CSSs as ``strong'' or ``fragile'' in the sense of their ability to migrate across CSS crystal configurations at high temperatures, distinguishing its formability. We argue that the magnitude of ${T}_{OD}$ may be an excellent predictor of CSS single-phase stability, which appears to scale with well-known HEA predictors, in particular we notice that VEC and ${T}_{OD}$ have in relation to the others a significantly large Pearson correlation coefficient, much larger than most other observables (except $\mathrm{\ensuremath{\Delta}}{H}_{\text{mix}}$).

Effects of high-speed shear and double-enzymatic hydrolysis on the structural and physicochemical properties of rice porous starch

This study aimed to investigate the physicochemical properties of the rice porous starch (HSS-ES) prepared by high-speed shear combined with double-enzymatic (α-amylase and glucoamylase) hydrolysis, and to reveal their mechanism. The analyses of 1H NMR and amylose content showed that high-speed shear changed the molecular structure of starch and increased the amylose content (up to 20.42 ± 0.04 %). FTIR, XRD and SAXS spectra indicated that high-speed shear did not change the starch crystal configuration but caused a decrease in short-range molecular order and relative crystallinity (24.42 ± 0.06 %), and a loose semi-crystalline lamellar, which were beneficial to the followed double-enzymatic hydrolysis. Therefore, the HSS-ES displayed a superior porous structure and larger specific surface area (2.962 ± 0.002 m2/g) compared with double-enzymatic hydrolyzed porous starch (ES), resulting in the increase of water and oil absorption from 130.79 ± 0.50 % and 109.63 ± 0.71 % to 154.79 ± 1.14 % and 138.40 ± 1.18 %, respectively. In vitro digestion analysis showed that the HSS-ES had good digestive resistance derived from the higher content of slowly digestible and resistant starch. The present study suggested that high-speed shear as an enzymatic hydrolysis pretreatment significantly enhanced the pore formation of rice starch.

Semiconducting metamorphism in Cu2+ substituted structurally enriched SnO2 nanocrystals

The manuscript portrays structural, microstructural, and electrical characteristics of pristine and Cu2+ doped SnO2 nanocrystals [Sn(1-x)CuxO2 NCs, where x = 0, 0.05, and 0.10] synthesized using conventional sol–gel technique. X-ray diffraction (XRD) results revealed that all the compositions possess single phase tetragonal rutile-type crystal configuration with space group P4/2mnm as confirmed by Rietveld refinement studies. Microstructural characterizations depicted homogeneous grain distribution with well interlinked grains and it was observed that the average grain size decreased from 30.29 nm to 27.47 nm with increasing Cu2+ concentration and the findings were consistent with structural studies. The concentric rings marked with Miller planes (110), (101), (200), and (211) observed in Selected Area Electron Diffraction (SAED) pattern. Hall effect measurements depicted that the concentration and mobility decreased with Cu2+ thereby transforms the system from n-type semiconductor to p-type.

Определение порога напряжения и микроструктурных факторов, формирующих эффект нелинейной разгрузки магниевого сплава МА14 (ZK60)

Magnesium alloys are an ideal material for creating lightweight and durable modern transport systems, but their widespread use is limited due to some physical and chemical properties. This paper considers the effect of nonlinear elastic unloading of the MA14 (ZK60, Mg–5.4Zn–0.5Zr) magnesium alloy in a coarse-grained state after recrystallisation annealing. The study found that the nonlinearity of the unloading characteristic, is formed when reaching a certain threshold stress level. It is expected that the effect under the study is associated with the deformation behavior of the alloy, during which the twin structure formation according to the tensile twinning mechanism is observed. The sample material microstructure was determined, by scanning electron microscopy using electron backscattered diffraction analysis. Determination of the threshold stress, for the formation of unloading nonlinearity was carried out by two methods: 1) by the value of the loop area formed by the nonlinearity of the unloading mechanical characteristics and the repeated loading (mechanical hysteresis) characteristics, and 2) by analysing the acoustic emission recorded during failure strain. A comparison of the results obtained, allows suggesting that the unloading nonlinearity is caused by twinning in grains, in which an unfavorable configuration (low Schmidt factor), for dislocation slip is observed. Rotating the twinned crystal at an angle close to 90° does not contribute to an increase in the Schmidt factor and activation of dislocation slip systems to secure the deformed structure through the dislocation strengthening mechanism. With a subsequent decrease in the external stress, detwinning and partial restoration of the crystal lattice configuration occur.

Effect of Y2O3 content on densification, microstructure and mechanical properties of reaction sintered magnesium aluminate spinel

Dense magnesium aluminate (MgAl2O4) spinels were developed via single-stage solid-state reaction sintering method at 1550–1650oC using combinations of varied commercial grade reactants-three different sources of alumina and two different sources of magnesia. The effect of Y2O3 doping in the concentration range of 1–4 wt % on different spinel batches was studied. Y2O3 addition was found to favour the densification of all the spinels at all dopant concentrations and maximum densification was found for the 2 wt % Y2O3 containing spinel batches. Phase analysis of the Y2O3 containing batches revealed the presence of yttrium aluminum garnet (YAG, Y3Al5O12) at all the sintering temperatures. Owing to similar crystal structure isotropic configuration of YAG (cubic) as that of spinel (cubic), Y2O3 doping was found to favour densification of spinel. Microstructural investigation revealed that Y2O3 containing batches have a controlled grain structure as compared to the without additive batches. Also, 2 wt % Y2O3 containing spinel batches sintered at 1650oC revealed better mechanical properties such as cold modulus of rupture and strength retainment after thermal shock than that of the undoped spinel batches.

THE EFFECTS OF PARTICLE SIZE AND TEMPERATURE ON THE STABILITY AND LOCAL STRUCTURAL EVOLUTIONS OF AMORPHOUS BULK AND NANOPARTICLES OF THE FeNI3 ALLOYS

The effects of particle size (2-6 nm) and temperature (300-1900 K) on the stability and local structural evolutions of amorphous bulk and nanoparticles of the FeNi3 alloys have been studied by using classical molecular dynamics (MD) simulation method combined with embedded atom model (EAM) in Largescale Atomic/Molecular Massively Parallel Simulator (LAMMPS). The nanoparticles were obtained from the unstable amorphous bulk FeNi3 alloys. MD simulations have been performed for glassy FeNi3 intermetallic alloy by making use of pairwise interatomic interaction potentials and electron densities calculated via EAM method. The formation and evolution of structures and their stability have been analyzed at a wide temperature range (300-1900 K) by calculating radial distribution functions (RDF), interatomic distances (ID), coordination numbers (CN), core-to-surface concentration profiles, as well as Voronoi analysis. According to the results, although some deviations in the structural properties occurred during the heat treatment, the amorphous nanoparticles exhibited the same crystal structure and local atomic configuration with its bulk counterpart at room temperature.