Lattice Planes Research Articles

Effect of symmetry reduction on the magnetic properties of LnIr[formula omitted]Si[formula omitted] polymorphs

Many tetragonal compounds LnIr2Si2 (Ln = lanthanoid) occur in two polymorphous phases and are therefore well suited to study the relationship between crystal structure and magnetic properties. We have grown GdIr2Si2 single crystals of both polymorphs from a high-temperature indium flux and investigated their anisotropic magnetic properties. The higher symmetric form with the ThCr2Si2 structure (space group I4/mmm) orders antiferromagnetically at TN=87K while for the lower symmetric compound in the CaBe2Ge2 structure (space group P4/nmm) we determined a much lower Néel temperature TN=12K. Our magnetic characterization of the single crystals reveals that for both compounds the magnetic moments are aligned in the a−a plane of the tetragonal lattice, but that the change of the symmetry strongly effects the inplane alignment of the moment orientation. For Ln=Er and Ho, we confirmed the existence of LnIr2Si2 in the space group P4/nmm. The magnetic properties of these lower symmetric compounds are in remarkable difference to their related compounds in the space group I4/mmm.

Flat-Band-Induced Anomalous Anisotropic Charge Transport and Orbital Magnetism in Kagome Metal CoSn.

For solids, the dispersionless flat band has long been recognized as an ideal platform for achieving intriguing quantum phases. However, experimental progress in revealing flat-band physics has so far been achieved mainly in artificially engineered systems represented as magic-angle twisted bilayer graphene. Here, we demonstrate the emergence of flat-band-dominated anomalous transport and magnetic behaviors in CoSn, a paramagnetic kagome-lattice compound. By combination of angle-resolved photoemission spectroscopy measurements and first-principles calculations, we reveal the existence of a kagome-lattice-derived flat band right around the Fermi level. Strikingly, the resistivity within the kagome lattice plane is more than one order of magnitude larger than the interplane one, in sharp contrast with conventional (quasi-) two-dimensional layered materials. Moreover, the magnetic susceptibility under the out-of-plane magnetic field is found to be much smaller as compared with the in-plane case, which is revealed to be arising from the introduction of a unique orbital diamagnetism. Systematic analyses reveal that these anomalous and giant anisotropies can be reasonably attributed to the unique properties of flat-band electrons, including large effective mass and self-localization of wave functions. Our results broaden the already fascinating flat-band physics, and demonstrate the feasibility of exploring them in natural solid-state materials in addition to artificial ones.

High-throughput calculation of atomic planar density for compounds

A large collection of element-wise planar densities for compounds obtained from the Materials Project is calculated using brute force computational geometry methods, where the planar density is given by the total fractional area of atoms intersecting a supercell's crystallographic plane divided by the area of the supercell's crystallographic plane. It is demonstrated that the element-wise maximum lattice plane densities can be useful as machine learning features. The methods described here are implemented in an open-source Mathematica package hosted at https://github.com/sgbaird/LatticePlane.

Investigation into the catalytic roles of oxygen vacancies during gaseous styrene degradation process via CeO2 catalysts with four different morphologies

CeO2 catalysts with four different morphologies (sphere, rod, octahedral and cube) were successfully synthesized under hydrothermal conditions and showed quite different thermocatalytic activities for gaseous styrene degradation. Unexpectedly, even though its main exposed lattice plane was (111), spherical CeO2 (CeO2-S), presented the highest styrene catalytic degradation activity (T90 =184 ℃) with a styrene degradation rate of 1.36 × 10−3 molstyrene g−1 h−1 at 200 ℃ that was approximately 12 times higher than that of cubic CeO2. A comprehensive structural characterization and mechanistic study found that the four CeO2 samples exhibit different degrees of lattice distortion and different oxygen vacancy concentrations. CeO2-S has the greatest lattice distortion, resulting in abundant oxygen vacancies. Oxygen vacancies were identified to be the main active sites through increasing reactive oxygen generation. Meanwhile, styrene was activated by adsorption of oxygen vacancies. Based on the results of in-situ DRIFTS and XPS measurements, 18O2 isotope tracing experiment and DFT theoretical calculations, the superior thermocatalytic performance of CeO2-S can be attributed to the lesser accumulation of intermediates on its surface, which follows the Langmuir-Hinshelwood (L-H) mechanism (low temperature) and the Mars-van Krevelen (MVK) mechanism (high temperature). In addition, no obvious decrease was observed in the activity of the CeO2-S catalyst for styrene degradation at 210 °C in the presence of water vapor, which is beneficial for the actual industrial application.

Spherical-periodic order and relevant short-range structural units in simple crystal structures

Since crystals grow from liquid and glassy states, the liquid structure feature may also exist in the pair-correlation functions of crystalline systems. The present article addresses the spherical-periodic order derived from Friedel oscillations in the pair-correlation functions of simple crystal structures such as face-centered cubic, hexagonal close-packed, and body-centered cubic structures. In these simple crystal structures, the resonance lattice planes, corresponding to the strong peaks in reciprocal space, give the Friedel wavelengths using their interplanar spacings, which are {111} and {200} for the face-centered cubic structure, {100}, {002}, and {101} for the hexagonal close-packed structure, and {110} for the body-centered cubic structure. After being scaled with the Friedel wavelengths corresponding to the most intense diffraction peaks, the pair-correlation functions all show atomic density maxima within the spherical-periodic zones. From such a spherical-periodic picture of any simple crystal structure, it is possible to identify a charge-neutral and mean-density local atomic entity that serves as the molecule-like structural unit of the whole structure. Examples in Cu-Zn, Co-Cr, and β-Ti alloys are provided to show how to interpret the compositions of simple-crystal-based industrial alloys.

In-situ investigation of strain relaxation in an Al/Si–MMC using high energy synchrotron radiation

AbstractThermal and mechanical loading induce phase specific strains/stresses in MMCs. At elevated temperature part of the phase-specific strains/stresses relax. The relaxation of the phase-specific strains/stresses is determined by in-situ experiments using white high-energy synchrotron radiation. The experiments reveal that such time-resolved strain measurements are possible and that short-time phenomena can be accessed using white high-energy synchrotron radiation. The elastic strain relaxation behavior is similar for all lattice planes accessed. The influence of the temperature on the characteristic relaxation time is determined. The characteristic relaxation time appears to be independent of the amount of plastic deformation the sample suffers before strain/stress relaxation.

Characterization of the fcc/bcc orientation relationship by EBSD using pole figures and variants

Abstract The orientation relationship (OR) between fcc and bcc lattices are described by crystallographic fundamentals using the example of Kurdjumov–Sachs (K–S) and Nishiyama–Wassermann (N–W). Complete pole figures containing all variants will be used to distinguish even between slightly different ORs. EBSD on iron meteorites and duplex steel has been used to analyse a large number of crystal orientations with regard to a high statistical significance and a high probability to capture all variants in a single measurement. It is shown that the use of fixed OR models like K–S, N–W, Bain, Pitsch, or Greninger–Troiano does not satisfacturally reflect the observed experimental pole distributions. It is not convenient to use high-indexed lattice planes and directions to describe the small deviations from the given models. The Euler subspace representation offers a readily comprehensible tool to get an idea about the characteristic of the experimentally detected OR.

Plumeria alba-Mediated Green Synthesis of Silver Nanoparticles Exhibits Antimicrobial Effect and Anti-Oncogenic Activity against Glioblastoma U118 MG Cancer Cell Line.

Plumeria alba (P. alba) is a small laticiferous tree with promising medicinal properties. Green synthesis of nanoparticles is eco-friendly, cost-effective, and non-hazardous compared to chemical and physical synthesis methods. Current research aiming to synthesize silver nanoparticles (AgNPs) from the leaf extract of P. alba (P- AgNPs) has described its physiochemical and pharmacological properties in recognition of its therapeutic potential as an anticancer and antimicrobial agent. These biogenic synthesized P-AgNPs were physiochemically characterized by ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscope (TEM), atomic force microscopy (AFM), X-ray diffractometry (XRD), and zeta potential analysis. Antimicrobial activity was investigated against Escherichia coli, Pseudomonas aeruginosa, Enterobacter aerogenes, Enterococcus faecalis, Bacillus subtilis, Streptococcus pneumoniae, Candida albicans, and Candida glabrata. Anticancer activity against glioblastoma U118 MG cancer lines was investigated using an MTT assay, and apoptosis activity was determined by flow cytometry. UV–visible spectroscopic analysis portrayed surface plasmon resonance at 403 nm of synthesized P-AgNPs, and FTIR suggested the presence of amines, alkanes, and phenol molecules that could be involved in reduction and capping processes during AgNPs formation. Synthesized particles were spherical in shape and poly-dispersed with an average particle size of 26.43 nm and a poly-dispersity index (PDI) of 0.25 with a zeta potential value of −24.6 mV, ensuring their stability. The lattice plane values confirm the crystalline nature as identified by XRD. These P-AgNPs exhibited potential antimicrobial activity against selected human pathogenic microbes. Additionally, the in vitro MTT assay results showed its effective anticancer activity against the glioma U118 MG cancer cell line with an IC50 value of 9.77 µg/mL AgNPs by initiating apoptosis as identified by a staining study with flow cytometric Annexin V–Fluorescein Isothiocyanate (FITC) and Propidium Iodide (PI). Thus, P. alba AgNPs can be recommended for further pharmacological and other biological research. To conclude, the current investigation developed an eco-friendly AgNPs synthesis using P. alba leaf extract with potential cytotoxic and antibacterial capacity, which can therefore be recommended as a new strategy to treat different human diseases.

Resonant coherent excitation and energy loss of slow channeling helium ions in AlN

By performing real-time time-dependent density-functional theory dynamic simulations, we report a velocity-dependent charge resonance on slow initial bare ions when channeling through the rocksalt crystalline AlN. Such charge resonance is accompanied by tremendously enhanced stopping at narrow velocity windows, which is attributed to the depletion in electronic screening by bound electrons, when the formation of defect state on projectile is depressed dramatically by the periodical field from lattice arrangement. The enhancement of stopping is not found in simulations with initial neutral incident ion, suggesting the effect of such charge resonance process mainly resides in the charge accumulation during the preequilibrium state, while making marginal influence on the excitation of bound state charge. We also investigated the charge resonance with revised lattice parameter, confirming the periodic atomic arrangement of lattice plane along ion trajectory is the main cause of such charge resonance.

Biosynthesis of Silver Nanoparticles by Polysaccharide of Leucaena leucocephala Seeds and Their Anticancer, Antifungal Properties and as Preservative of Composite Milk Sample

The AgNPs were synthesized using water-soluble polysaccharides extracted from the Leucaena leucocephala seeds. The UV-visible spectrum of the AgNPs showed a sharp absorption peak at 448 nm. The XRD analysis showed four major peaks of the crystalline AgNPs with planes of a face-centered cubic lattice of silver. The EDS spectrum showed a strong signal peak at ~3 keV. TEM and SEM observations showed the spherical shape of AgNPs with no particle agglomeration, and the size ranged from 8 to 20 nm. AgNPs were highly stable at -14.2 mV by zeta potential measurement. AgNPs showed significant anticancer activity against the cell lines of breast cancer, liver carcinoma, and colon carcinoma with the I C 50 value of 22.5, 12.3, and 8.9 μg mL-1, respectively. AgNPs at 900 μg mL-1 exhibited considerable antifungal activity against ten fungal pathogens. Water-soluble polysaccharide has the ability to synthesize AgNPs keeping strong antitumor, antifungal activities. The AgNPs can slow down spoilage of composite milk samples at different temperatures. In addition, the accuracy of milk-IR-analyses was not affected by different concentrations of AgNPs.

Lattice-Resolution, Dynamic Imaging of Hydrogen Absorption into Bimetallic AgPd Nanoparticles.

Palladium's strong reactivity and absorption affinity to H2 makes it a prime material for hydrogen-based technologies. Alloying of Pd has been used to tune its mechanical stability, catalytic activity, and absorption thermodynamics. However, atomistic mechanisms of hydrogen dissociation and intercalation are informed predominantly by theoretical calculations, owing to the difficulty in imaging dynamic metal-gas interactions at the atomic scale. Here, we use in situ environmental high resolution transmission electron microscopy to directly track the hydrogenation-induced lattice expansion within AgPd triangular nanoprisms. We investigate the thermodynamics of the system at the single particle level and show that, contrary to pure Pd nanoparticles, the AgPd system exhibits α/β coexistence within single crystalline nanoparticles in equilibrium; the nanoparticle system also moves to a solid-solution loading mechanism at lower Ag content than bulk. By tracking the lattice expansion in real time during a phase transition, we see surface-limited β phase growth, as well as rapid reorientation of the α/β interface within individual particles. This secondary rate corresponds to the speed with which the β phase can restructure and, according to our atomistic calculations, emerges from lattice strain minimization. We also observe no preferential nucleation at the sharpest nanoprism corners, contrary to classical nucleation theory. Our results achieve atomic lattice plane resolution─crucial for exploring the role of crystal defects and single atom sites on catalytic hydrogen splitting and absorption.

Direct van deer Waals epitaxy of multiband-emitting InGaN-based LEDs on graphene for phosphor-free white light illumination

The white light-emitting diodes (LEDs), a kind of representative multiband light emitters, which are generally manufactured by coating phosphor with InGaN-based blue LED chips, are widely used in illumination and display. However, the degradation and wavelength-conversion loss of phosphor are still issues which shorten the life of these LEDs. Herein, we demonstrate a convenient way to fabricate phosphor-free multiband-emitting LEDs without any external process or additional dielectric interlayers, utilizing only graphene as substrate for direct van deer Waals epitaxy (vdWE) of multiple-facet InGaN-based LEDs. Taking advantage of the low nucleation density of GaN on graphene, the surface morphology of the films was controlled as complete voids without flat. The morphology of InGaN/GaN multi quantum wells followed with the multiple-facet GaN, which caused the variation of indium concentration in different lattice plane of multi quantum well and led to multiband emission. Those findings reveal the roles of graphene in growth of III-nitride and provide valuable insights into the application of graphene for phosphor-free white light illumination.

The Influence of CsBr on Crystal Orientation and Optoelectronic Properties of MAPbI3-Based Solar Cells.

Crystal orientations are closely related to the behavior of photogenerated charge carriers and are vital for controlling the optoelectronic properties of perovskite solar cells. Herein, we propose a facile approach to reveal the effect of lattice plane orientation distribution on the charge carrier kinetics via constructing CsBr-doped mixed cation perovskite phases. With grazing-incidence wide-angle X-ray scattering measurements, we investigate the crystallographic properties of mixed perovskite films at the microscopic scale and reveal the effect of the extrinsic CsBr doping on the stacking behavior of the lattice planes. Combined with transient photocurrent, transient photovoltage, and space-charge-limited current measurements, the transport dynamics and recombination of the photogenerated charge carriers are characterized. It is demonstrated that CsBr compositional engineering can significantly affect the perovskite crystal structure in terms of the orientation distribution of crystal planes and passivation of trap-state densities, as well as simultaneously facilitate the photogenerated charge carrier transport across the absorber and its interfaces. This strategy provides unique insight into the underlying relationship between the stacking pattern of crystal planes, photogenerated charge carrier transport, and optoelectronic properties of solar cells.

Quantifying the effect of macrozones on the cold-dwell fatigue response of UD-rolled Ti-6Al-4V using high-energy X-ray diffraction

High-energy X-ray diffraction is used to investigate the evolution of elastic lattice strains in rolled Ti-6Al-4V specimens during cyclic loading in-situ with and without the inclusion of a 120s dwell period. A 1mm segment of the gauge section is monitored throughout the first 100 cycles for specimens extracted along the rolling direction (RD), the transverse direction (TD) and 45° between the two, to explore the effects of texture on the evolution of the micromechanical response. Five families of lattice planes from the hexagonal α phase are analysed with emphasis on lattice strain measured at the peak of each cycle, while macroscopic strain accumulation is simultaneously monitored via Digital Image Correlation. In cyclic loading conditions including a dwell period at load, a prominent increase in elastic strains is observed in prismatic and basal lattice planes with the specimen loaded 45° from the rolling direction. In the absence of dwell, both RD and TD specimen orientations exhibited subtle cyclic hardening in all families of lattice planes probed despite negligible evolution in accumulated macroscopic plastic strain. Estimations of lattice orientation-dependent stresses are also presented using directional moduli to examine redistribution of load across sets of grains with the increasing cycle count.

Friction stir processed Al 7075 matrix composites with addition of SiC coated graphene nanoplatelets

Friction Stir Processing (FSP) is a surface modification technique that has been commonly used while preparing surface composites. Through FSP, the surface properties such as strength, hardness, wear, and corrosion resistance could be enhanced by adding discontinuous reinforcements in the base alloy. The present experimental investigation involves nano reinforcements i.e graphene nanoplatelets (GNP) and SiC coated GNP was reinforced into Al 7075 and fabricated nano surface composite via Friction stir processing (FSP). A nano SiC granular and layered coating over GNP was obtained from FESEM studies. The Surface morphology, tensile strength, microhardness, and wear studies were explored. The hardness and ultimate tensile strength values of FSP'ed Al 7075, GNP, and SiC coated GNP in Al 7075 were 96.2, 128.4, 139.3 HV, and 344.8, 383.2, and 417.5 N/mm2 respectively. The hardness and ultimate tensile strength significantly increased by 44% and 21%. In similar lines, the specific wear rate also decreased 80% compared to other samples due to its lubricant property. X-RD analysis affirms the existence of Al, SiC, GNP phases that match with the lattice planes. Microscopic studies revealed the presence of SiC particles on GNP as a form of coating and also dispersed uniformly in Al 7075 composites.

Synthesis, characterization and electro active properties of poly (MT-co-4-Fluoro aniline) Ag dispersed polymer nano composites

A series of electroactive nanocomposites was prepared by in-situ polymerization method. The silver nanoparticles dispersed in poly (metatoluidine-co-4-fluoroaniline) copolymer. The solubility characteristic of these materials are tested in various polar and polar solvents. The m-toluidine-co-4-fluoroaniline silver doped polymer nanocomposites is more soluble in organic solvents. These polymer nanocomposites possess better soluble nature than that of its homopolymer. From the UV–visible spectra absorption band obtained at 382 nm is attributed to the π-π* transition of the benzenoid moiety. The charge transfer process from benzenoid to quinoid, the band at 659 nm. The shifting of bands from 1596, 1488 cm−1 to 1598, 1495 cm−1 in the m-toluidine-co-4-fluoroaniline silver doped polymer nanocomposites observed in FTIR spectra. X-ray diffraction confirms the non-crystallinity of the m-toluidine-co-4-fluoroaniline silver doped polymer nanocomposites at a band around 25°. The crystalline peaks observed at 2θ around 32, 46, 64 and 73°is due to the lattice planes of face-centered cubic (FCC) (111), (200), (220) and (311) silver nanoparticles in poly (m-toluidine-co-4-fluoroaniline). SEM analysis shows the composites exhibits spherical granular sponge structure. They are microclustured in nature having porosity too. The conductivity value of m-toluidine-co-4-fluoroaniline silver doped polymer nanocomposites is decreased from 1.1 × 10-8 S/cm to 0.2524 × 10-8 S/cm.

The enzymatic performance derived from the lattice planes of Ir nanoparticles

DFT calculations reveal that the versatile enzyme-like properties of IrNPs are directly related to their crystal planes. The catalase-like activity originates from the Ir(111) plane, while the oxidase-like activity is intrinsic to the Ir(220) plane.

Mechanism of stress induced irreversible magnetic anisotropy in Fe-based alloy ribbons

Fe-based amorphous and nanocrystalline soft magnetic alloys are regarded as the significant dual-green energy-saving materials because of their superior magnetic properties and straightforward fabrication procedure. As such, they have attracted much attention in the fields of the electronic information and electrical power. In this work, Fe<sub>73.5</sub>Cu<sub>1</sub>Nb<sub>3</sub>Si<sub>13.5</sub>B<sub>9</sub> (%) amorphous alloy ribbon is subjected to various physical ageing treatments in nitrogen atmosphere. These treatments include annealing at 540 ℃ for 30 min under different tensile stresses and isothermal tempering without tensile stress for several cycles. The origin of stress-induced magnetic anisotropy is investigated through using dynamic strain analysis, the longitudinally driven giant magento-impedance effect, and synchrotron radiation X-ray diffraction. In the process of tensile stress annealing, it is found that the axial strain of ribbon is elastic strain when annealing temperature is below the glass transition point, and plastic strain when annealing temperature is above the glass transition point; the precipitation of nanocrystalline phase has a pinning effect on amorphous matrix, which slows down the strain rates and makes the tend stable. Additionally, isothermal tempering studies show that the stress-induced magnetic anisotropy and lattice plane anisotropy have different relaxation patterns. It is found through numerical fitting that the stress-induced magnetic anisotropy can reach a stable value of 0.144 by infinite tempering, whereas the lattice plane anisotropy can only relax to zero by finite tempering. A model of nanocrystalline grain distribution anisotropy is developed to re-examine the origin of stress-induced magnetic anisotropy. It supports a viewpoint that the nanocrystalline grain distribution anisotropy <inline-formula><tex-math id="M4">\begin{document}$\Delta \delta $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221509_M4.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221509_M4.png"/></alternatives></inline-formula> is responsible for the stress-induced irreversible magnetic anisotropy <inline-formula><tex-math id="M5">\begin{document}${K_{\text{d}}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221509_M5.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221509_M5.png"/></alternatives></inline-formula>, and that their relationship can be described as a following function: <inline-formula><tex-math id="M6">\begin{document}${K_{\text{d}}} = k\Delta \delta $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221509_M6.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20221509_M6.png"/></alternatives></inline-formula>. Therefore, it is proposed that the stress-induced anisotropy originates from a synergistic interaction between the lattice plane anisotropy and the nanocrystalline grain distribution anisotropy in Fe-based alloy ribbon. This work has important implications for understanding the mechanism of the stress-induced magnetic anisotropy.

High Index Lattice Plane of CDS to Enhance Photocatalytic Hydrogen Production

High Index Lattice Plane of CDS to Enhance Photocatalytic Hydrogen Production

Double perovskite Cs2AgBiBr6 radiation sensor: synthesis and characterization of single crystals

Single crystals of lead-free halide double perovskite Cs2AgBiBr6 sensor material manifest a remarkable potential for application in radiation detection and imaging. In this study, the purity and crystallinity of solution-grown Cs2AgBiBr6 single crystals with cubic Fmoverline{3}m symmetry have been corroborated by powder XRD measurements, while the single crystal XRD patterns reveal the dominant {111} lattice planes parallel to the sample surfaces. A wider range of lower resistivity values (106–109 Ωcm) was obtained from the I-V measurements compared to the 1.55 × 109–6.65 × 1010 Ωcm values from the van der Pauw method, which is typically higher for the Ag than for the carbon paint electrodes. Charge-carrier mobility values estimated from the SCLC method for the carbon paint-Cs2AgBiBr6 (1.90–4.82 cm2V−1 s−1) and the Ag-Cs2AgBiBr6 (0.58–4.54 cm2V−1 s−1) including the density of trap states (109–1010 cm−3) are comparable. Similar values of 1.89 cm2V−1 s−1 and 2.36 cm2V−1 s−1 are derived from the Hall effect measurements for a sample with carbon and Ag electrodes, respectively. The key electrical parameters including the X-ray photoresponse measurements indicate that the Cs2AgBiBr6 samples synthesized in this study satisfy requirements for radiation sensors.Graphical abstract