Crystal Configuration Research Articles

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.

Fast Reconfigurable Phase Shifter Based on a Chiral Liquid Crystal Configuration

Fast Reconfigurable Phase Shifter Based on a Chiral Liquid Crystal Configuration

Generation of a Synthetic Database for the Optical Response of One-Dimensional Photonic Crystals Using Genetic Algorithms

This work proposes an optimization tool based on genetic algorithms for the inverse design of photonic crystals. Based on target reflectance, the algorithm generates a population of chromosomes where the genes represent the thickness of a layer of a photonic crystal. Each layer is independent of another. Therefore, the sequence obtained is a disordered configuration. In the genetic algorithm, two dielectric materials are first selected to generate the population. Throughout the simulation, the chromosomes are evaluated, crossed over, and mutated to find the best-fitted one based on an error function. The target reflectance was a perfect mirror in the visible region. As a result, it was found that obtaining photonic crystal configurations with a specific stop band with disordered arrangements is possible. The genetic information of the best-fitted individuals (layer sequence, optical response, and error) is stored in an h5 format. This method of generating artificial one-dimensional photonic crystal data can be used to train a neural network for solving the problem of the inverse design of any crystal with a specific optical response.

The Influence of Temperature Changes on the Rice Starch Structure and Digestive Characteristics: One and Two-Step Annealing.

This study investigated the effects of annealing on the structural and physicochemical properties of rice starch below the onset temperature (To) by 5 °C and 15 °C. The results revealed that annealing improved the gelatinization temperature of rice starch, decreased the swelling power, solubility, and paste viscosity of rice starch, and had no significant effects on the morphological structure and crystal configuration of rice starch. In one-step annealing, the annealing temperature of 60 °C is more conducive to the rearrangement of starch molecules, so its crystallinity, short-range ordered structure, and gelatinization temperature are higher than at 50 °C; however, its RDS, SDS, and RS contents will be increased. During the two-step annealing treatment, the temperature change is not conducive to the molecular chain rearrangement and to the formation of perfect crystalline structure, which increases the sensitivity of enzymes to starch, so the RDS content of starch increases significantly, while the RS content decreases.

Anisotropic correlations in higher manganese silicides

Anisotropic correlations are vital for understanding the thermoelectric transport properties of higher manganese silicides (HMSs). In this work, we establish the implications of anisotropy on thermoelectric performance by examining the orientational variants in melt-grown single crystal and directional configurations of spark plasma sintered polycrystalline specimens of HMS. Single crystal specimen aligned perpendicular to the c-axis (i.e., along the cleavage ab-plane) exhibited high electrical and thermal conductivity, while the maximum Seebeck coefficient was measured along the c-axis direction. Similarly, polycrystalline specimens exhibited a weakened anisotropy with an enhanced weighted mobility and reduced thermal conductivity than their monocrystal counterpart resulting in a relatively higher thermoelectric figure-of-merit (zT). The characteristic MnSi striations were found to be predominantly grown perpendicular to the c-axis in melt-grown single crystals while peritectic decomposition during sintering is commonly observed in sintered polycrystals thereby emanating an inherently disordered and modulated lattice structure in the synthesized HMS crystals. It was observed that the zT for single and polycrystalline HMSs could be erroneously estimated if charge and phonon transport properties are measured in different directions. This study offers newer insights into the structure-property relationships of HMSs and demonstrates the need for more careful considerations in addressing the anisotropic behavior and microstructural evolutions that prevails in HMS crystals.

Nonmonotonous temperature fluctuations of the orbital moment and spin-orbit coupling in multiferroic gallium ferrite thin films

Temperature dependent x-ray absorption spectroscopy and x-ray magnetic circular dichroism experiments were performed at the Fe ${L}_{2,3}$ edges to unveil the magnetic orbital moment and spin-orbit coupling (SOC) behavior in thin films of the multiferroic ${\mathrm{Ga}}_{0.6}{\mathrm{Fe}}_{1.4}{\mathrm{O}}_{3}$ (GFO) compound. A thorough analysis of the data evidenced a nonmonotonous behavior for both magnetic orbital moment and SOC with a minimum at approximately 120 K, accompanied with indications of disturbances of the magnetic exchange and electric field dipole. Resonant photoemission spectroscopy experiments performed at the Fe ${L}_{2,3}$ edges rendered an important modification of the crystal field configuration around this temperature value, pointing to a temperature-driven structural trigonal distortion. These instabilities can be compared to those observed in other iron oxides, in particular, during transitions such as the Verwey transition, with the difference that on GFO they do not have any impact on the macroscopic magnetic properties, such as the coercive field and the global magnetization. This work demonstrates that the absence of instabilities in magnetism at the macroscopic scale does not guarantee the absence of fluctuations at the atomic scale. Such atomic-scale fluctuations of the SOC are undoubtedly shown here and have an impact on the spin Hall magnetoresistance response of the films. This point is of importance for prospective applications of GFO in spin-orbitronics.

Continuous crystallization and its potential use in drug substance Manufacture: A review

Interest in the continuous manufacturing in the pharmaceutical industry for the production of Active Pharmaceutical Ingredients (API’s) has greatly increased in recent years. This has led to a variety of studies on continuous processing including a large number of studies in the area of continuous crystallization. While various potential crystallizer configurations exist, the vast majority of work in this area has focused around the Mixed Suspension Mixed Product Removal (MSMPR) crystallizer. In this review, MSMPR crystallizers will be described along with their use in continuous API manufacture.

Density-of-states similarity descriptor for unsupervised learning from materials data

We develop a materials descriptor based on the electronic density-of-states (DOS) and investigate the similarity of materials based on it. As an application example, we study the Computational 2D Materials Database (C2DB) that hosts thousands of two-dimensional materials with their properties calculated by density-functional theory. Combining our descriptor with a clustering algorithm, we identify groups of materials with similar electronic structure. We introduce additional descriptors to characterize these clusters in terms of crystal structures, atomic compositions, and electronic configurations of their members. This allows us to rationalize the found (dis)similarities and to perform an automated exploratory and confirmatory analysis of the C2DB data. From this analysis, we find that the majority of clusters consist of isoelectronic materials sharing crystal symmetry, but we also identify outliers, i.e., materials whose similarity cannot be explained in this way.

Slow-light effect in symmetry-reduced non-defect photonic crystals

In this study, a two-dimensional low-symmetric photonic crystal (PC) configuration with elliptical geometry is presented and its slow-light (SL) effect is investigated. Reducing the symmetry in the PC unit cell provides slow modes at the higher transverse electric bands. The calculated group index and the corresponding normalized bandwidth equal to {ng, BW}={63.56, 0.0065}. That corresponds to a value of figure of merit (FOM)=0.4344 defined by the product of the average group index and the normalized bandwidth, FOM=〈ng〉BW, which is comparable to the values available in literature. Tracing the whole edges of the Brillouin zone, strongly excited SL modes are observed only along Γ-X but not along Γ-X’ or Γ-M. That condition allows for the design of low-symmetric PC waveguides with finite thicknesses at the expense of lowering group index value. The SL effect is still obtained for the proposed low-symmetric PCs having finite thicknesses, which is numerically proved via finite-difference time-domain methods. It is important to note that non-dispersive SL Bloch modes exist through the non-zero k-vector components of Brillouin zone. Hence, such a defect-free (without either point- or line- defect) SL PC design may have a great potential for the use of compact photonic devices such as in optical switching and biochemical sensing applications.

First-principles study on high-pressure phases and compression properties of gold-bearing intermetallic compounds

Compared to elemental gold (Au), Au-based alloys have attracted wide attention for their economy and superior performance stemming from their distinctive physicochemical properties. The study of the structural characterization for alloy materials remains one of the fundamental issues associated with their future applications essentially. In this work, we theoretically explore some typical intermetallic compounds of Au-based alloys under high pressure, which has been an effective means to generate intriguing crystal configurations with unexpected behaviors. Our ab initio simulations find that Fd-3m-AuRb, Fd-3m-AuBa, and Fd-3m-AuLa become stable above ∼10 GPa, and Pmmn-AuAl becomes stable above ∼20 GPa. Further investigations of their compression behaviors reveal that the bulk moduli of Au-based alloys can be greatly reduced by combining alkali and alkaline earth metals. The present results have unraveled the high-pressure phases of Au-bearing compounds and provide insights for exploring their important compressibility that is strongly relevant to the containing non-Au elements.

Crystal configuration, spectroscopic and optical characteristics of Er3+ doped YAlO3 perovskites for advanced photonic appliances

Perovskite structural based Er (III) doped YAlO3 nanophosphors have been synthesized via cost-effective and simplistic urea assisted solution combustion (SC) synthetic route. The resulting products are well characterized by various structural and spectroscopic studies in detailed. Crystal structure has been elucidated by X-ray diffraction (XRD) and Rietveld refinement method. Prepared powdered samples are crystallized in orthorhombic crystal system having space group Pbnm (62). Energy dispersive X-ray (EDX) spectroscopic analysis is performed to evaluate the atomic (%) and weight (%) of constitute elements and their relative distribution through mapping profile. The most intense excitation peak centred at 378 nm is well harmonized with the distinctive wavelength of commercialized NUV based LED chips. Photoluminescence (PL) studies depicted green emissions of doped nanophosphors upon excitation at 378 nm wavelength. The most intense emission peak at 549 nm is accredited to 4S3/2 →4I15/2 electronic transition of the Er3+ ion. Moreover, PL data is exploited to obtain photometric parameters viz. color coordinates (x and y), color purity (%) and correlated color temperature (CCT), which robustly recommended for their usage as NUV based solid-state advance photonic appliances.

Defect absorption and emission for p-atic liquid crystals on cones.

We investigate the ground-state configurations of two-dimensional liquid crystals with p-fold rotational symmetry (p-atics) on fixed curved surfaces. We focus on the intrinsic geometry and show that isothermal coordinates are particularly convenient as they explicitly encode a geometric contribution to the elastic potential. In the special case of a cone with half-angle β, the apex develops an effective topological charge of -χ, where 2πχ=2π(1-sinβ) is the deficit angle of the cone, and a topological defect of charge σ behaves as if it had an effective topological charge Q_{eff}=(σ-σ^{2}/2) when interacting with the apex. The effective charge of the apex leads to defect absorption and emission at the cone apex as the deficit angle of the cone is varied. For total topological defect charge 1, e.g., imposed by tangential boundary conditions at the edge, we find that for a disk the ground-state configuration consists of p defects each of charge +1/p lying equally spaced on a concentric ring of radius d=(p-1/3p-1)^{1/2p}R, where R is the radius of the disk. In the case of a cone with tangential boundary conditions at the base, we find three types of ground-state configurations as a function of cone angle: (i) for sharp cones, all of the +1/p defects are absorbed by the apex; (ii) at intermediate cone angles, some of the +1/p defects are absorbed by the apex and the rest lie equally spaced along a concentric ring on the flank; and (iii) for nearly flat cones, all of the +1/p defects lie equally spaced along a concentric ring on the flank. Here the defect positions and the absorption transitions depend intricately on p and the deficit angle, which we analytically compute. We check these results with numerical simulations for a set of commensurate cone angles and find excellent agreement.

Ti:Sa Crystal Geometry Variation vs. Final Amplifiers of CPA Laser Systems Parameters

In this paper, the different Ti:Sapphire crystal configurations of the final amplifiers, depending on the Chirped Pulse Amplification laser system parameters, such as the repetition rates and pulse energy, are discussed. Restrictions placed on the final Ti:Sa amplifiers with a high repetition rate are discussed. The repetition rate of these systems is limited due to the crystal overheating, which leads to stress fracturing or significant beam distortion. The heating density threshold leading to stress fracturing was calculated and taken as the limit of the upper level of the possible pump average power. On the basis of these calculations, the highest repetition rates and corresponding thermolens focal distances were estimated for conventional crystal geometry of the most suitable thicknesses. It was demonstrated that conventional crystal shapes, such as a thin disc, can be used for systems with repetition rates below a few hundred Hz if several Joules of the output pulse energy are required. The rectangular thin crystal plate geometry was more suitable for Ti:Sa amplifiers with repetition rates above 1 kHz. Finally, the parameters of rectangular thin crystal plate Ti:Sa laser amplifier with an output energy above 3 J per pulse for a laser system with more than 100 TW pulse power and 1 kHz repetition rates are presented.

Study on the Bandgap Characteristics and Vibration-Reduction Mechanism of Symmetric Power-Exponent Prismatic Phononic Crystal Plates

In this paper, a symmetric power-exponent prismatic phononic crystal configuration was proposed for the vibration reduction of thin plate structures, and the mechanism of bandgap generation and the influencing factors of the band gaps were analyzed. The results showed that the proposed symmetric power-exponent prismatic phononic crystal structure has three complete band gaps of bending waves, where the width of the second band gap can go up to 1639 Hz. The band gaps of bending waves of the phononic crystal were verified using a combination of numerical simulations and experimental methods, and subsequently, the bandgap characteristics and energy-focusing effect of the phononic crystals were effectively used to suppress the bending vibration of the thin plate. With the increase in prismoid height of the structure, the width of the first band gap expanded, while the bandwidths of the other two band gaps narrowed down. It was observed that an increase in the power of the power-exponent prismoid would reduce the starting and ending frequencies of the band gaps, whereas an increase in the prismoid edge thickness would weaken the energy-focusing effect and narrow the band gaps gradually. Our research results provide a new technique and a pathway to realize vibration reduction in thin plate structures.

Abundant Dislocation Layered Double Hydroxides Synthesis by Molten Salt with Bound Water Boosting Oxygen Evolution.

Optimizing the adsorption free energy and promoting the active phase transition to further enhance the oxygen evolution reaction (OER) activity remain significant challenges. The adsorption free energy can be optimized by modulating the electronic structure and adjusting the crystal configuration. Meanwhile, the transformation of the active phase can be promoted by introducing strain energy. The theoretical calculations are conducted to verify the rational envisage. However, it is still a great obstacle to introducing strain into the electrocatalysts and avoiding destruction. The stress field caused by dislocation can realize both of the above. Hence, the molten salt with the bound water method is proposed and the abundant dislocation layered double hydroxides (D-NiFe LDH) are constructed. The in situ characterizations further verify the dislocations significantly affect the generation of the active phase and the state of electronic structure. Consequently, the D-NiFe LDH exhibits outstanding OER activity and obtains 10mA cm-2 , only requiring 199mV overpotential with fabulous stability (100mA cm-2 more than 24h). The work paves a new avenue for the rational introduction dislocations to optimize the crystal configuration and boost the active phase formation, significantly enhancing the OER performance.

Single-molecule study on the force-induced melting in syndiotactic polypropylene single crystals

Highly stereoregular syndiotactic polypropylene (s-PP) with high crystallinity and melting temperature has unique physical properties such as high impact resistance and transparency, which is closely related to the chain conformation and crystal structure of s-PP. However, the molecular mechanism underlying the mechanical properties remains unclear, because the complex amorphous-crystalline network and the diverse crystal structure limit the classical characterizations. Here, we investigate the single-molecule force-induced melting in the melt-prepared and solution-prepared s-PP single crystal by using atomic force microscopy (AFM)-based single molecule force spectroscopy (SMFS). Our results show that the mechanical stability slightly increases with the increase of crystal thickness and the crystal thickness also has a significant impact on the melting pathway. The comparison of the melting pathways of s-PP and isotactic polypropylene (i-PP) suggests that the syndiotactic structure and lower tacticity of s-PP will increase the chain friction during slide and therefore suppresses the αc relaxation in the crystal region. Moreover, the difference of the chain folding trajectory in sectors (100) and (010) shows no effect on the mechanical stability. However, the mechanical stability of form I structure was higher than that of form II.

Hysteresis-like phase transitions in quadrupole traps

In this paper, we consider the Coulomb crystals in linear ion trap with a nonlinear dissipative force induced by optical radiation. We discuss a relation between 2D and 3D ion crystals formation and the crystalline units’ initial conditions. A phase diagram of the Coulomb crystal configurations is constructed. We introduce a cross size and surface area metrics to define a Coulomb crystals dimension sensitivity to the initial conditions and show the hysteresis-like-type phase transition between 2D and 3D configurations.

CRYSTAL CONFIGURATION DEPENDENCE OF CSI(TL) SCINTILLATION DETECTORS ON ENVIRONMENTAL DOSE RATE MEASUREMENT.

The crystal configuration dependence of thallium-doped caesium iodide (CsI(Tl)) scintillation detectors was analysed on an ambient dose equivalent (H*(10)). H*(10) were systematically calculated in various crystal conditions for aspect ratios and sizes in a virtual environment contaminated by radionuclides to investigate directional characteristics by comparing the H*(10)s with the typical irradiation geometries in anterior-posterior (AP), lateral (LAT), rotational (ROT) and isotropic (ISO). The simulation revealed that H*(10) obviously changes according to the crystal configuration and cuboidal CsI(Tl) scintillation detectors with specific aspect ratios could be applied to environmental dose rate measurement without further changes in the calibration procedure.

Systematic Investigation on the Electrochemical Performance of Pristine Silver Metal–Organic Framework as the Efficient Electrode Material for Supercapacitor Application

The pristine silver metal–organic framework (Ag-MOF) is successfully synthesized by the one-pot synthesis method. It serves as the effective electrode material for supercapacitor application because of its excellent conductive frame network and electrochemical activities. The crystal structure, surface morphology, porosity, and chemical configuration of the Ag-MOF are studied and analyzed using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), Brunauer–Emmett–Teller (BET) theory, and X-ray photoelectron spectroscopy (XPS) analysis. The electrochemical behavior of the electrode material is determined using galvanostatic charge/discharge (GCD), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The aggregated platelike morphology of Ag-MOF provides more electrochemical active sites and shortens the pathway for ion intercalation/deintercalation which results in outstanding electrochemical performance. The maximum specific capacity of 606.2 C g–1 is achieved at a current density of 1 A g–1 in the three-electrode system. The asymmetric supercapacitor device delivers the maximum energy density of 48.69 W h kg–1 at a power density of 608.73 W kg–1. Furthermore, the fabricated device retains an attractive cyclic stability of 131.14% for 5000 cycles at a current density of 5 A g–1 claimed as the novel electrode material in the area of energy storage.

Spontaneous emission enhancement based on thin-film chalcogenide/fluoride one dimensional photonic crystal

We report the fabrication of a one-dimensional photonic crystal microcavity via co-evaporation with electron beam/thermal evaporation process, which, to the best of our knowledge, is the first rare-earth doped one-dimensional photonic crystal based on chalcogenide/fluoride thin films. The microcavity was made of a half-wave dysprosium doped Ga2Se3 layer sandwiched between two embedded Ga2Se3/YF3 distributed Bragg reflectors. Near infrared transmittance spectra indicated that the stopband region from 1090 nm to 1515 nm was formed and a cavity resonance centered at 1342 nm. A cavity quality factor of 153 was achieved resulting in a 53-fold enhancement in spontaneous emission intensity. This photonic crystal microcavity configuration offers a new route to mid-wavelength and long-wavelength infrared fluorescence enhancement, which has attracted considerable interest for potential applications, such as fluorescence-based imaging and biomedical sensing.