Crystal Configuration Research Articles

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

Augmenting specific capacitance of ammonium vanadate cathode in aqueous zinc-ion batteries via barium doping directed by glutamic acid

Aqueous Zinc-Ion Batteries (AZIB), as a promising class of multivalent metal-ion batteries, have garnered attention for their exceptional safety and extremely high theoretical capacity. Despite these advantages, their adoption has been impeded by a notable capacity shortfall relative to Lithium-Ion Batteries (LIB). Addressing this challenge, our research leverages glutamic acid as a chelating agent to craft barium-doped ammonium vanadate nanoflowers through a hydrothermal approach, serving as an innovative AZIB cathode material. The incorporation of barium ions has notably expanded the doping distance from 9.817 Å to 12.900 Å, markedly diminishing the diffusion resistance of Zn2+ ions and unveiling a plethora of active sites. These structural enhancements have fostered accelerated ion transport and bolstered redox kinetics. Our fabricated cathode material exhibits exceptional reversibility during the redox transitions between V5+/V4+ and V3+ and the zinc ion doping process. Utilizing BNVO-3 as the cathode, which presents an ideal crystal configuration, the AZIB achieved near-perfect Coulombic efficiency. Impressively, at a current density of 0.1 A g-1, it achieved a remarkable peak discharge capacity of 384.91 mAh g-1. Furthermore, after 1500 cycles at 5A g−1, it maintained an impressive 92.9 % capacity retention. This study heralds a new era for barium-doped vanadium-based AZIB cathodes, characterized by their high stability, reversibility, and capacity.

Terahertz Spectra of Mannitol and Erythritol: A Joint Experimental and Computational Study.

Sugar substitutes, which generally refer to a class of food additives, mostly have vibration frequencies within the terahertz (THz) band. Therefore, THz technology can be used to analyze their molecular properties. To understand the characteristics of sugar substitutes, this study selected mannitol and erythritol as representatives. Firstly, PXRD and Raman techniques were used to determine the crystal structure and purity of mannitol and erythritol. Then, the THz time-domain spectroscopy (THz-TDS) system was employed to measure the spectral properties of the two sugar substitutes. Additionally, density functional theory (DFT) was utilized to simulate the crystal configurations of mannitol and erythritol. The experimental results showed good agreement with the simulation results. Finally, microfluidic chip technology was used to measure the THz spectroscopic properties of the two sugar substitutes in solution. A comparison was made between their solid state and aqueous solution state, revealing a strong correlation between the THz spectra of the two sugar substitutes in both states. Additionally, it was found that the THz spectrum of a substance in solution is related to its concentration. This study provides a reference for the analysis of sugar substitutes.

Constructing Alkyl Chain Modified FeII Spin Crossover Complexes through Complementary Pair Strategy

AbstractFour alkyl chains and cyclohexane modified FeII complexes [Fe(Ln)(L’)](ClO4)2⋅solv (n=1, 2, 3, 4) were synthesized and characterized. X‐ray diffraction study showed that these complexes were constituted by asymmetric mononuclear FeII entities, incorporating alkyl‐chain‐modified bppCOOH (2,6‐bis(1H‐pyrazol‐1‐yl)isonicotinic acid) ligands and 6,6’’‐2,6‐dimethoxyphenyl‐substituted terpy ligand (L’). Magnetic susceptibility measurements revealed that complexes 1, 2, and 3 were in the high spin state across the measured temperature range, whereas complex 4 displayed an incomplete spin crossover phenomenon, with a transition temperature (T1/2) at 240 K. Investigations into variable‐temperature structure and magneto‐structural correlations revealed that the integration of alkyl‐chain‐modified bipyridyl units fostered the π⋅⋅⋅π intra‐ and intermolecular interactions, contributing to distinct crystal stacking and spatial configurations in complex 4 when compared to its counterparts. These findings underscore the pivotal influence of intramolecular interactions on the FeII spin states and highlight the significance of designing flexible ligands for modulating spin‐crossover characteristics.

Multiphysics simulation study of thermal stress effects in nanoscale FinFETs heterogeneously integrated with GaN high-power device on silicon substrate

Heterogeneous integration enables high-density integration to improve system functionality, but meanwhile brings reliability concerns due to the intensification of temperature and thermal stress. However, research on thermal stress effects in nanoscale transistors within heterogeneous integrated circuit is still very limited up to now. Multiphysics computation for the heterogeneous integration of nanoscale p-FinFET with GaN high electron mobility transistor (HEMT) on silicon substrate is performed. Firstly, self-heating of GaN HEMT induced thermal stress is simulated. Then, thermal stress effects induced by the GaN HEMT on quantum transport in the FinFET at different locations are compared and analyzed, including the hole effective mass, hole average velocity, on/off-state current, and on-off ratio. Moreover, the impacts of crystal orientation configurations are further discussed. Simulation results show that the impact of thermal stress on FinFET is highly dependent on the Si crystal orientation and its location relative to GaN HEMT. Taking the FinFET with (001)/[110] confinement/transport orientation, which is at a distance of RFET and an angle of φ from the GaN HEMT as an example, thermal stress induces the significant reductions in Ion and Ioff of FinFET at φ = π/2 and φ = 3π/2, and the increases of Ion and Ioff in FinFET at φ = 0 and φ = π, but has small impact on FinFETs located diagonally to the GaN HEMT.

Topological Photonic Alloy.

We present the new concept of photonic alloy as a nonperiodic topological material. By mixing nonmagnetized and magnetized rods in a nonperiodic 2D photonic crystal configuration, we realized photonic alloys in the microwave regime. Our experimental findings reveal that the photonic alloy sustains nonreciprocal chiral edge states even at very low concentration of magnetized rods. The nontrivial topology and the associated edge states of these nonperiodic systems can be characterized by the winding of the reflection phase. Our results indicate that the threshold concentrations for the investigated system within the first nontrivial band gap to exhibit topological behavior approach zero in the thermodynamic limit for substitutional alloys, while the threshold remains nonzero for interstitial alloys. At low concentration, the system exhibits an inhomogeneous structure characterized by isolated patches of nonpercolating magnetic domains that are spaced far apart within a topologically trivial photonic crystal. Surprisingly, the system manifests chiral edge states despite a local breakdown of time-reversal symmetry rather than a global one. Photonic alloys represent a new category of disordered topological materials, offering exciting opportunities for exploring topological materials with adjustable gaps.

First principles investigation of Li[formula omitted]Si and Li[formula omitted]Sn alloys: Unraveling atomic-scale influences on material properties

Commercial batteries have currently reached their peak specific capacity, which proves insufficient for the ongoing global energy transition. Consequently, there has been a surge of interest in developing new materials over the last decade, especially those based on silicon (Si) and tin (Sn), known for their high capacity. Despite numerous publications highlighting the advantages of these materials, crucial questions remain regarding volume expansion that must be addressed to propose effective solutions and facilitate their widespread commercial application. In this study, density functional theory was employed to investigate the formation of LixM (M = Si, Sn). Our analysis delves into crystal (c-LixM), amorphous (a-LixM), and amorphous slab (s-LixM) configurations during structural optimization calculations, with the aim of comparing and contrasting relevant findings. The exploration encompasses energetic aspects, volume expansion, and electronic properties. The obtained data enables the simulation of lithiation potential curves for each structural type, directly comparable with experimental results of these materials functioning as anodes in lithium-ion batteries. Notably, the volume expansion of a-LixM exhibits non-linear behavior, correlating with characteristic plateaus in the voltage profile curves.

Modelization of extended axial field-of-view PET scanners to analyze the performance improvement

Positron Emission Tomography (PET) offers non-invasive insights into physiological processes. However, in clinical practice conventional PET scanners face limitations in comprehensive imaging due to their restricted axial field of view (FOV).This study explores the benefits and challenges of extending PET scanner AFOV using Monte Carlo simulation with GATE 9.1. The Biograph Vision Quadra scanner is a novel system based on the Digital Biograph Vision 600 scanner. Both devices use silicon photomultipliers and 3.2 x 3.2 × 20 mm Lutetium Oxyorthosilicate crystals (LSO). However, the 32 detector rings of the Quadra scanner enable a four-fold expansion in the Axial Field Of View (FOV) compared to Vision. As a result, higher sensitivity, and an enhancement of noise equivalent count rate and image quality are achieved. The purpose of this study is to analyze the effect of increasing the number of detector rings and the axial FOV on the scanner performance. To accomplish this, four different geometries are modeled using GATE (GEANT4 Application for Tomographic Emission). Based on the Biograph Vision 600 model, the length and the number of detector rings are gradually extended to reach the length of the Quadra scanner. Thus, four geometries with 8 (25.6 cm), 16 (51.2 cm), 24 (76.8 cm) and 32 (102.4 cm) detector rings are simulated, keeping the crystal configuration and the dimensions in the transaxial plane. The study evaluates sensitivity, Noise Equivalent Count Rate (NECR), and image quality parameters. Results indicate a significant increase in sensitivity and NECR with FOV extension, underscoring enhanced performance. However, artifact occurrence, particularly concentric circular patterns and background homogeneity changes, accentuates with extended AFOV. Normalization algorithms, particularly component-based normalization, mitigate these artifacts. This study contributes to the understanding of the advantages and limitations of extending PET scanner AFOV, offering insights into the effectiveness of component-based normalization for improving PET image quality.

Design of a pressure sensor based on the 1D ternary Octonacci photonic crystal configurations

Design of a pressure sensor based on the 1D ternary Octonacci photonic crystal configurations

Numerical analysis of microstructured optical fibers based on flint glass for ultra-high nonlinearity, low loss, and broadband dispersion compensation across telecom bands

This research investigates the potential of flint glass as a foundational material for photonic crystal configurations designed to achieve high nonlinear coefficients across various communication wavelengths. We explore dispersion management within telecom bands using flint glass-based micro-structured optical fibers, employing numerical analysis via the finite element method to assess optical properties. In this study, three different basic MOF structures (hexagonal, square, and octagonal) were created using flint glass background material rather of the commonly utilized fused silica material, and the numerically was assessed in contrast to prior studies and designs. Among the configurations studied, the octagonal arrangement (FGO-MOF) excels in dispersion compensation, achieving −136.6 ps/(nm.km) at 1.55 µm. Conversely, the hexagonal air hole ring cladding design (FGH-MOF) displays higher nonlinearity (770.5 W−1.km−1), a smaller effective area (1.115 µm2), and a high numerical aperture (0.6378). In contrast, the square air hole ring cladding optical fiber (FGS-MOF) exhibits low confinement loss (6.309 × 10−7 dB/cm) at 1.55 µm but with comparatively less favorable optical properties. Our study demonstrates that the hexagonal microstructured optical fiber with flint glass (FGH-MOF) offers superior performance in dispersion compensation, nonlinearity, and low loss within telecom bands. This finding suggests promising applications in high-bit-rate communication systems, biomedical sensing, and supercontinuum generation, presenting exciting avenues for further research and practical implementation.

Pressure Induces Six-fold Coordination for the Lighter Pnictides Phosphorus and Arsenic Triiodide.

In this study, we employ an evolutionary algorithm in conjunction with first-principles density functional theory (DFT) calculations to comprehensively investigate the structural transitions, electronic properties, and chemical bonding behaviors of XI3 compounds, where X denotes phosphorus (P) and arsenic (As), across a range of elevated pressures. Our computational analyses reveal a distinctive phenomenon occurring under compression, wherein the initially trigonal structures of PI3 (P 63) and AsI3 (R-3) undergo an intriguing transformation, leading to the emergence of six-coordinated monoclinic phases (C2/m) at 6 GPa and 2 GPa for PI3 and AsI3, respectively. These high-pressure phases exhibit their stability up to 10 GPa for PI3 and 12 GPa for AsI3. Notably, the resulting structures at elevated pressures bear striking resemblance to the widely recognized six-coordinated octahedral BiI3 crystal configuration observed at ambient conditions. Our investigation further underscores the pivotal role of pressure-induced reactivity of the lone-pair electrons in PI3 and AsI3, facilitating their enhanced stereochemical reactivity and thereby enabling higher six-fold coordination. Complementary analyses employing electron localization function (ELF) and density of states (DOS) effectively delineate the progression towards augmented coordination in PI3 and AsI3 with increasing pressure. While the phenomenon of heightened coordination is conventionally associated with heavier pnictide iodides such as SbI3 and BiI3 under ambient conditions due to heightened ionic character and relativistic effects in bismuth (Bi) and antimony (Sb), our findings accentuate that analogous structural transformations can also be induced in lighter elements like phosphorus (P) and arsenic (As) under the influence of pressure.

Analysis of Phase Mismatch for Mercurous Bromide-Based Non-Collinear AOTF Design in Spectral Imaging Applications.

The spectral and spatial characteristics of Acousto-Optic Tunable Filters (AOTFs), such as a tuning curve, spectral resolution, angular aperture, and diffraction efficiency, are determined by the device's acousto-optic crystal configuration and piezoelectric transducer. For high-throughput spectral imaging applications, it is essential to enlarge the spectral bandwidth and angular aperture during the design phase of AOTFs. Thus, phase mismatch due to incident angle or wavelength was studied analytically using phase diagrams in this paper. Additionally, a performance parameter analysis model was established based on the use of mercurous bromide crystals for large angular aperture AOTF device design, and the impact of crystal and transducer design parameters on the spectral bandwidth and angular aperture was evaluated. This also experimentally validates the diffraction capability of AOTFs made from mercurous bromide crystal, which possess a broad spectral transmission ability ranging from visible to long-wave infrared.

Antiferromagnetic Semiconductor BaMnO3 Hexagonal Perovskite with a Direct Bandgap.

The unique properties of direct bandgap semiconductors make it important to search for semiconductors exhibiting this phenomenon in perovskite materials. In this study, we employed first-principles calculations to investigate the crystal structures, magnetic configurations, and electronic properties of hexagonal perovskite BaMnO3 in its 4H and 6H phases. The results indicate that both structures exhibit antiferromagnetic characteristics, in which the Mn-O-Mn superexchange plays the dominant role in the 4H phase, although there is a competition between the Mn-Mn direct exchange interaction and the Mn-O-Mn superexchange interaction. In contrast, these two interactions exhibit harmonious coexistence in the 6H phase, and the two antiferromagnetic transitions occurring in the experimental phase should be related to the synergistic effect between them. Despite their different internal arrangements, they exhibit the same charge combination of Ba2+Mn4+O2-3. More importantly, both phases exhibit semiconductor properties with a direct bandgap, making it suitable to serve as an alternative material for photovoltaic and optoelectronic devices. In particular, the band gap of the 4H phase is just the right size to absorb visible light, and the 6H phase should be a potential candidate to absorb light in the ultraviolet region.

Determination of lutetium density in LYSO crystals: methodology and PET detector applications

Objective. Lutetium yttrium oxyorthosilicate (LYSO) scintillation crystals are used in positron emission tomography (PET) due to their high gamma attenuation, fair energy resolution, and fast scintillation decay time. The enduring presence of the 176Lu isotope, characterized by a half-life of 37.9 billion years, imparts a consistent radiation background (BG) profile that depends on the geometry and composition attributes of the LYSO crystals. Approach. In this work, we proposed a methodology for estimating the composition of LYSO crystals in cases where the exact Lutetium composition remains unknown. The connection between BG spectrum intensity and intrinsic radioactivity enables precise estimation of Lutetium density in LYSO crystal samples. This methodology was initially applied to a well-characterized LYSO crystal sample, yielding results closely aligned with the known composition. The composition estimation approach was extended to several samples of undisclosed LYSO crystals, encompassing single crystal and crystal array configurations. Furthermore, we model the background spectrum observed in the LYSO-based detector and validate the observed spectra via simulations. Main results. The estimated Lutetium composition exhibited adequate consistency across different samples of the same LYSO material, with variations of less than 1%. The result of the proposed approach coupled with the simulation successfully models the background radiation spectra in various LYSO-based detector geometries. Significance. The implications of this work extend to the predictive assessment of system behaviors and the autonomous configuration parameters governing LYSO-based detectors.

The origin of Calabi-Yau crystals in BPS states counting

We study the counting problem of BPS D-branes wrapping holomorphic cycles of a general toric Calabi-Yau manifold. We evaluate the Jeffrey-Kirwan residues for the flavoured Witten index for the supersymmetric quiver quantum mechanics on the worldvolume of the D-branes, and find that BPS degeneracies are described by a statistical mechanical model of crystal melting. For Calabi-Yau threefolds, we reproduce the crystal melting models long known in the literature. For Calabi-Yau fourfolds, however, we find that the crystal does not contain the full information for the BPS degeneracy and we need to explicitly evaluate non-trivial weights assigned to the crystal configurations. Our discussions treat Calabi-Yau threefolds and fourfolds on equal footing, and include discussions on elliptic and rational generalizations of the BPS states counting, connections to the mathematical definition of generalized Donaldson-Thomas invariants, examples of wall crossings, and of trialities in quiver gauge theories.

Effect of in-situ Zr doping on the crystallization behavior and electrochemical properties of cobalt-free layered LiNi0.8Mn0.2O2 cathode materials

Elemental doping is an effective strategy to overcome the degradation of the rate performance of cobalt-free layered cathode materials, which is attributable to the absence of cobalt. This study focuses on the implementation of a modified doping strategy, which entails in-situ coprecipitation to introduce 0.3 mol% Zr4+ as a dopant to these cathode materials. This approach enabled us to confirm that in-situ Zr4+ doping significantly impacted the crystallization behavior and electrochemical properties of these materials and this effect is not negligible. In particular, in-situ Zr4+ doping increased the crystallization temperature of the materials and broadened the spacing between the lithium layers while maintaining the original crystal configuration. The doped sample had the best cycling stability at the crystallization temperature of 800 °C (capacity retention of 80.03% after 200 cycles at the 1 C rate) and rate performance (discharge specific capacity of up to 161.6 mAh g−1 at the 5 C rate), whereas the original (undoped) sample delivered the best electrochemical performance at 780 °C (capacity retention of 74.29% after 200 cycles at the 1 C rate and discharge capacity at the 5 C rate of 154.57 mAh g−1).

Structural, thermal, surface, and electrical properties of Bi2O3 ceramics co–doped with Er–Ho–Tb rare earths

Face–centered cubic–Bi2O3 (δ–phase) material is a better ion conductor when compared to other types of solid electrolytes that have been declared in the literature due to its anion–defective crystal configuration, and hence it can be a promising solid electrolyte choice for intermediate temperature SOFC applications. In this research, Er–Ho–Tb co–doped Bi2O3 compounds were successfully synthesized by the solid–state reaction method and characterized using the XRD, TG & DTA, FPPT, and FE–SEM techniques. Apart from sample 4Er4Ho4Tb, each sample became stable with a cubic δ–phase at room temperature, according to XRD patterns. The DTA curves revealed no exothermic or endothermic peaks, implying a phase change in the constant heating cycle. The conductivity of Ho–rich compositions was higher than that of others, confirming the impact of cation polarizability on conductivity. In addition, at 700 °C, the sample 4Er8Ho4Tb with 1:2:1 content ratios had the highest conductivity of 0.29 S/cm. The porosity on the grain boundaries increased with doping, leading to higher grain boundary resistance, which could be responsible for the conductivity drop.

3D Diffusion of Water in Melt Inclusion‐Bearing Olivine Phenocrysts

AbstractOlivine‐hosted melt inclusions are an important archive of pre‐eruptive processes such as magma storage, mixing and subsequent ascent through the crust. However, this record can be modified by post‐entrapment diffusion of H+ through the olivine lattice. Existing studies often use spherical or 1D models to track melt inclusion dehydration that fail to account for complexities in geometry, diffusive anisotropy and sectioning effects. Here we develop a finite element 3D multiphase diffusion model for the dehydration of olivine‐hosted melt inclusions that includes natural crystal geometries and multiple melt inclusions. We use our 3D model to test the reliability of simplified analytical and numerical models (1D and 2D) using magma ascent conditions from the 1977 eruption of Seguam volcano, Alaska. We find that 1D models underestimate melt inclusion water loss, typically by ∼30%, and thus underestimate magma decompression rates, by up to a factor of 5, when compared to the 3D models. An anisotropic analytical solution that we present performs well and recovers decompression rates within a factor of 2, in the situations in which it is valid. 3D models that include multiple melt inclusions show that inclusions can shield each other and reduce the amount of water loss upon ascent. This shielding effect depends on decompression rate, melt inclusion size, and crystallographic direction. Our modeling approach shows that factors such as 3D crystal geometry and melt inclusion configuration can play an important role in constraining accurate decompression rates and recovering water contents in natural magmatic systems.

Regulating the distribution of iron active sites on γ-Fe2O3via Mn-modified α-Fe2O3 for NH3-SCR

Developing below 150 °C highly activity and broad reaction window catalysts has been challenging by using Fe-based catalysts for NH3-SCR. The octahedral Fe3+ (Fe3+Oh) sites exist in hematite (α-Fe2O3) and maghemite (γ-Fe2O3) are inactive for NH3-SCR due to the redox circle of Fe2+→Fe3+ reliance on the distribution of iron sites in crystal structure. Here we modified the α-Fe2O3 crystal structure by substituting part inactive Fe3+Oh sites with catalytically active Mn3+Oh sites, which promoted the formation of γ-Fe2O3 to generate the active tetrahedral Fe3+ (Fe3+Td) sites and enhanced the magnetism of the Fe1−yMnyOx. The strong Fe-O-Mn interaction established by crystal coordinative configurations not only boosted the formation of NO2 but also facilitated the Brønsted acid circle. Surprisingly, the Fe0.85Mn0.15Ox exhibited the superior low temperature NH3-SCR activity, with NOx conversion above 100% at 100–275 °C under a GHSV of 60000 h−1.

LkGraphene Nano-Derivatives in Pharmaceuticals and Biomedical Advancements: A Comprehensive Review

Abstract: The two-dimensional structure of graphene has a flat single layer of carbon molecules having a honeycomb crystal lattice configuration. Graphene possesses typical physicochemical characteristics such as elevated conductivity, wide-ranging surface area, good biocompatibility, and excellent mechanical properties. Due to their exceptional properties, graphene derivatives have significant implementations in many fields like electronics, environmental, chemical, pharmaceutical, and others. With its distinctive formation and biological characteristics, pharmaceutical and biomedical applications of graphene have gained the impressive interest of researchers and scientists over the past few years. The exceptional properties of graphene, such as its larger surface area, which is four times greater than other nanoparticles, represented it as a prior choice for drug delivery. Graphene derivatives are monolayer graphene, bilayer graphene, reduced Graphene Oxide (rGO), and Graphene Oxide (GO). This review focused on different pharmaceutical applications and the part of the progress made by different researchers on graphene and its derivatives in the distinct field of interest, like in the delivery of drugs, cancer therapy, gene delivery, antibacterial effect, biosensing, bioimaging, tissue engineering, and others.