Deformation Of Crystals Research Articles

Efficient and Stable Perovskite Nanocrystal Light-Emitting Diodes with Sulfobetaine-Based Ligand Treatment

Perovskite nanocrystals (PNCs) possess outstanding optical properties such as narrow full-width at half-maximum (fwhm) emission and color tunability. However, the labile ionic nature and weakly bound surface ligands of PNCs result in colloidal instability and crystal structure deformation, thus degrading their optical properties. In this study, we treated CsPbBr3 PNCs with 3-(dodecyldimethyl-ammonio)propane-1-sulfonate (12-SBE) ligands and successfully stabilized the PNCs under ambient air and heat. Under optimum ligand exchange conditions, 12-SBE PNCs showed near 100% photoluminescence quantum yield (PLQY) without an increase in the size of the PNCs. After 12-SBE treatment, the agglomeration of PNCs in solution due to ligand loss was suppressed, and PNC size growth induced by moisture and oxygen under heating was reduced. Finally, we fabricated 12-SBE PNC LEDs exhibiting 6.7% external quantum efficiency (EQE). Moreover, the PL lifetime of 12-SBE PNC LEDs was enhanced 2-fold compared to oleylamine (OAM) PNC LEDs.

Development of five-dimensional scanning transmission electron microscopy.

By combining the scanning transmission electron microscopy with the ultrafast optical pump-probe technique, we improved the time resolution by a factor of ∼1012 for the differential phase contrast and convergent-beam electron diffraction imaging. These methods provide ultrafast nanoscale movies of physical quantities in nano-materials, such as crystal lattice deformation, magnetization vector, and electric field. We demonstrate the observations of the photo-induced acoustic phonon propagation with an accuracy of 4ps and 8nm and the ultrafast demagnetization under zero magnetic field with 10ns and 400nm resolution, by utilizing these methods.

DFT-D3 study of two-dimensional polymerization of C60 crystal under high pressure

The high-pressure behavior of a monomer and 2D polymerized C60 crystals were investigated using DFT-D3 calculations. Although covalent bonds were not observed in monomer upon simple compression, C60 moieties in two-dimensional polymer phases (Immm and phases) exhibited intermolecular electron density, which indicates the formation of covalent bonds between C60 moieties. The C60 crystals were highly compressed under high pressure; however, small compression was observed at the C60 moieties. Both internal energies and PV terms contributed similarly to enthalpy. The deformation of crystals prevented polymerization. These results suggested a different behavior from that of typical inorganic materials.

Experimental Study on Performance Optimization of Grouting Backfill Material Based on Mechanically Ground Coal Gangue Utilizing Urea and Quicklime.

Previously conducted studies have established that grouting backfill in mining-induced overburden bed separation and mined-out areas with broken rocks provides an efficient strategy to control strata movement and surface subsidence caused by underground mining. Grouting backfill materials (GBMs) based on coal gangue (CG) are highly desirable in coal mining for accessibility to abundant CG and urgent demand for CG disposal. However, CG is generally employed as coarse aggregate due to rather rigid and inert properties, limiting its application in GBMs. Herein, to reduce reliance on fine aggregates, such as fly ash and clay, cemented GBM formulations using ground CG powder as a dominant component were proposed. Urea and quicklime were utilized as additives to optimize slurry transportability and compressive strength. Besides typical grinding without additives, CG powder was also prepared via grinding with urea, intending to enhance the hydrogen bonding (HB) interaction between urea and minerals contained in CG. The effect of grinding time and urea on CG particle size and phase composition was investigated. Then, the dependence of slurry transportability and compressive strength on grinding time, solid concentration, urea, and quicklime dosage were revealed. It has been experimentally proved that grinding for 30~90 min significantly decreased CG particle size and even induced crystal deformation of dolomite and kaolinite. For GBMs, urea improved slurry flowability, possibly caused by decreased water absorption on the CG surface and the release of water encapsulated in hydrated cement particles. Moreover, quicklime strengthened GBM bodies, which could be explained by an accelerated pozzolanic reaction between CG powder and additional CH supplied by quicklime hydration. G60U3-based GBM-B2 with 5% quicklime provided a stable and smooth slurry with a bleeding rate of 1.25%, a slump flow of 205 mm, and a hardened body with a seven-day UCS of 1.51 MPa.

Preparation and investigation of physiochemical, magnetic, and anti-microbial properties of cobalt-doped Bi2S3 nanostructure

The current study proposes the synthesis of cobalt-doped Bi2S3 nanostructures by the unique reverse micelle method at room temperature. Analysis using Energy dispersive analysis of X-rays (EDAX) demonstrated the correct stoichiometry, powder X-ray diffraction (PXRD) data were Rietveld refined using GSAS-II software confirming the formation of orthorhombic Bi2S3 with some residuals for cubic CoS2 phase. As the weight% of cobalt increases, the unit cell volume of orthorhombic Bi2S3 increases from 503.17 (16) (A0)3 to 507.34 (4) (A0)3. The Raman measurement shows the vibrational mode of both orthorhombic Bi2S3 and cubic CoS2 phases. The weak peak centered at 255 cm−1 is due to the symmetric vibration of the Bi–S bond which disappears in cobalt-doped samples and was replaced by new peaks related to Co–S bond vibration. This indicates the deformation in host orthorhombic Bi2S3 crystal due to cobalt doping and is consistent with Rietveld refinement results of PXRD. This work also gives the value of isobaric Gruneisen parameter for CoxBi2-xS3 (x = 0.0,1.0,1.5 & 2.0 wt%) were 5.1, −7.3, −4.8, and −5.2 respectively obtained from the low-temperature Raman measurement. The optical study shows the increment in band-gap with doping and proves to have visible light active band-gap. The pristine Bi2S3 nanostructures showed broad emission from the violet region (400 nm) to the yellow region (590 nm) with maximum emission at 440 nm in the blue region. The PL intensity decreases as cobalt weight% increases because of electron-hole recombination. The morphological study through high-resolution transmission electron microscopy (HR-TEM) revealed the single crystalline nature and showed the change in morphology from nanocylinders and nanorods with nanoparticles. The room temperature ferromagnetic behavior increases as cobalt weight% increases and reaches the maximum for 1.5 wt% cobalt. This study showed that the prepared nanostructures have potential application as an antimicrobial agent against both Gram + ve and Gram-ve microorganisms.

Editorial: Strong field physics and attosecond science

emission from Rydberg atoms. Substantial neutral atoms can be excited after tunneling in a strong laser 14 field, in the process known as frustrated tunneling ionization. The generation of coherent emission from 15 the excited-state atoms produced by the frustrated tunneling ionization is demonstrated to be dependent on 16 the chirp of the laser pulse. This chirp dependence also provides a new way to investigate the dynamics 17 of Rydberg states. Kong et al. (Kong et al., 2022) explored the influence of mechanical strains on the 18 high-order harmonic generation in the monolayer hexagonal boron nitride crystal by using time-dependent 19 density functional theory. They found the band structure is sensitive to the structural deformation modulated 20 by strains. This result may be useful in probing lattice deformations in crystals and heuristic to enhance the 21 optoelectronic efficiency of solid-state nano-devices. In conclusion, the Research Topic is created to present the latest advances and trends concerning the 62 strong field physics and attosecond science. Our special thanks to the Frontiers in Physics team for the 63 technical assistance with publishing. Much more efforts are still ongoing in this fascinating area. We expect 64 that this field will attract more and more attentions and benefit potential applications.

Avalanches and rate effects in strain-controlled discrete dislocation plasticity of Al single crystals

Three-dimensional discrete dislocation dynamics simulations are used to study strain-controlled plastic deformation of face-centered cubic aluminium single crystals. After describing the rate and size dependence of the average stress-strain curves, we study the power-law distributed strain bursts and the average avalanche shapes, and find a universal power-law exponent $\tau \approx 1.0$ for all imposed strain rates and system sizes, characterizing both the event sizes and their durations. We discuss the dependence of our results on loading rate and compare these with previous studies of strain-controlled two-dimensional systems of discrete dislocations as well as of quasistatic stress-controlled loading of aluminium single crystals.

Dynamic length scale and weakest link behavior in crystal plasticity

Irreversible deformation of crystals is often characterized by stochastic scale-free distributed intermittent local plastic bursts. Quenched obstacles with short-range interaction were found to limit the size of these events, which was termed as a transition from wild to mild fluctuations. Here, we show by analyzing the local yield thresholds in a discrete dislocation model that a dynamic length scale can be introduced based on weakest link principles, and this scale characterizes the extension of plastic events. The interplay between long-range dislocation interactions and short-range quenched disorder is found to destroy scale-free dynamical correlations, thus leading to event localization (that is, shortening of the length scale) which explains the crossover between the wild and mild regimes. Several methods are presented to determine the dynamic length scale which can be generalized to other types of heterogeneous materials.

Elastic Organic Crystals as Bioinspired Hair‐Like Sensors

AbstractOne of the typical haptic elements are natural hairy structures that animals and plants rely on for feedback. Although these hair sensors are an admirable inspiration, the development of active flow sensing components having low elastic moduli and high aspect ratios remains a challenge. Here, we report a new sensing approach based on a flexible, thin and optically transmissive organic crystal of high aspect ratio, which is stamped with fluorescent dye for tracking. When subjected to gas flow and exposed to laser, the crystal bends due to exerted pressure and acts as an optical flow (hair) sensor with low detection limit (≈1.578 m s−1) and fast response time (≈2.70 s). The air‐flow‐induced crystal deformation and flow dynamics response are modelled by finite element analysis. Due to having a simple design and being lightweight and mechanically robust this prototypical crystal hair‐like sensor opens prospects for a new class of sensing devices ranging from wearable electronics to aeronautics.

Elastic Organic Crystals as Bioinspired Hair-Like Sensors.

One of the typical haptic elements are natural hairy structures that animals and plants rely on for feedback. Although these hair sensors are an admirable inspiration, the development of active flow sensing components having low elastic moduli and high aspect ratios remains a challenge. Here, we report a new sensing approach based on a flexible thin and optically transmissive organic crystal of high aspect ratio, which is stamped with fluorescent dye for tracking. When subjected to gas flow and exposed to laser, the crystal bends due to exerted pressure and acts as optical flow sensor with low detection limit (~1.578 ms-1) and fast response time (~2.70 s). The air-flow-induced crystal deformation and flow dynamics response are modelled by finite element analysis. Due to the simple design, light-weight, and mechanical robustness, this prototypical crystal hair-like sensor opens prospects for a new class of sensing devices from wearable electronics to aeronautics.

In Situ Growth of Cyclodextrin‐Based Metal Organic Framework Air Filters for Reusable SO2 Adsorbent Applications

AbstractIn situ growth of cyclodextrin‐based metal‐organic frameworks (CD‐MOFs) is investigated for the effective fabrication of MOF composites through the vapor diffusion method combined with O2 plasma treatment. The growth rate of γ‐CD‐MOFs on poly(ethylene terephthalate) fibers (CD‐MOFs–PET) is determined for 136 h, and the CD‐MOFs‐PET with 24 h growth time shows the highest surface area without crystal deformation. The specific surface area of the CD‐MOFs‐PET with 24 h growth time is 142.88 m2 g−1, which is 235 times higher than the pristine PET fibers. The 24 h CD‐MOFs‐PET shows removal efficiencies higher than 99% for PM0.1 and higher than 95% for SO2 gas. The CD‐MOFs‐PET demonstrates high recovery of SO2 adsorption ability by the repeated adsorption‐desorption cycles, maintaining up to 90% of initial adsorption performance. This study intends to provide an informative discussion of the applicability of textile‐based CD‐MOFs and the development of reusable filters for the removal of SO2.

Pauli crystal melting in shaken optical traps

Pauli crystals are ordered geometric structures that emerge in trapped noninteracting fermionic systems due to their underlying Pauli repulsion. The deformation of Pauli crystals - often called melting - has been recently observed in experiments, but the mechanism that leads to it remains unclear. We address this question by studying the melting dynamics of N=6N=6 fermions as a function of periodic driving and experimental imperfections in the trap (anisotropy and anharmonicity) by employing a combination of numerical simulations and Floquet theory. Surprisingly, we reveal that the melting of Pauli crystals is not simply a direct consequence of an increase in system energy, but is instead related to the trap geometry and the population of the Floquet modes. We show that the melting is absent in traps without imperfections and triggered only by a sufficiently large shaking amplitude in traps with imperfections.

Crystal orientation and deformation state analysis in Kikuchi patterns via pattern reconstruction aided deep learning

Crystal orientation and deformation state analysis in Kikuchi patterns via pattern reconstruction aided deep learning

On the brittleness of elementary semiconductors

It is shown that the brittleness of a single-component covalent crystal (diamond, Si, Ge) is due to the "duplicity" of the paired potential of interatomic interaction for elastic (reversible) and for plastic (irreversible) deformation. This leads to the fact that the specific surface energy during plastic deformation of a covalent crystal is more than two times less than the specific surface energy during elastic deformation. Therefore, with a small deformation of a covalent crystal, it is energetically more advantageous to create a surface by irreversible breaking than by reversible elastic stretching. It is indicated that the brittle-ductile transition in a single-component covalent crystal is accompanied by metallization of covalent bonds on the surface. It is shown that the brittle-ductile transition temperature (TBDT) for single-component covalent crystals under static load has an upper limit: TBDT/Tm<0.45, where Tm --- is the melting temperature. Keywords: interatomic covalent bond, brittleness, ductility, elementary semiconductors, brittle-ductile transition.

О хрупкости элементарных полупроводников

It is shown that the brittleness of a single-component covalent crystal (diamond, Si, Ge) is due to the “duplicity” of the paired potential of interatomic interaction for elastic (reversible) and for plastic (irreversible) deformation. This leads to the fact that the specific surface energy during plastic deformation of a covalent crystal is more than two times less than the specific surface energy during elastic deformation. Therefore, with a small deformation of a covalent crystal, it is energetically more advantageous to create a surface by irreversible breaking than by reversible elastic stretching. It is indicated that the brittle-ductile transition in a single-component covalent crystal is accompanied by metallization of covalent bonds on the surface. It is shown that the brittle-ductile transition temperature (TBDT) for single-component covalent crystals under static load has an upper limit: TBDT/Tm < 0.45, where Tm is the melting temperature.

Attempt to correlate dislocations network and distribution to macroscale plane rotations in <001> cast-mono ingots

This work aims to contribute to the understanding of the mechanisms behind electrically active crystalline defect formation in cast-mono (cm) ingots grown along the <001> axis. Both the spatial distributions of background dislocations in the cellular dislocation array and the driving force for dislocation multiplication in the sub-grains are not perfectly understood. Macroscale length crystal rotations are here characterized by the (θ/2θ) X-ray diffraction (XRD) method at different ingot heights and along two perpendicular sample axes. XRD measurements show the presence of crystal rotations in the large single grain domain. Two orthogonal misorientations components are found to evolve linearly along each sample axis forming plane orientation gradients up to (0.05 ± 0.02) degree/cm extending over 12 cm inside the cast-mono grain. (001) crystal structure deformation are also analysed by rocking curve imaging (RCI) using synchrotron radiation on wafers of a neighboring brick. First, results confirm the presence of the plane orientation gradient measured by XRD and its order of magnitude. Second, RCI results demonstrate that the plane orientation gradient is associated to the cellular dislocation network. Therefore, these results strongly suggest that background dislocations network of a cellular form can create an organized orientation gradient at large distance within the ingot. The involvement of the characterized orientation gradients in the formation and extension of electrically active SGBs in cast-mono ingots is discussed. • Crystal structure deformation measurements of cm-Si ingots. • Evidence of the presence of {001} planes orientation gradients. • Plane orientation gradients almost constant along the sample axes. • Orientation gradients increase with the ingot height. • Orientation gradients associated to the cellular network of dislocations.

Quasi-static deformation simulations of molecular crystals

This research employs two computational methods to simulate shear deformation of molecular crystals; it calculates slip barriers, finds rotational twinning, and predicts polymorphic transitions.

Witness to strain: Subdomain boundary length and the apparent subdomain boundary density in large strained olivine grains

Abstract Electron backscatter diffraction (EBSD) investigation of strain mainly uses polycrystalline samples to study fabric development. We extend the use of EBSD for the analysis of large single mineral grains by measuring the apparent surficial subdomain boundary density per unit area, reported here as unit segment length (USL). We apply this USL technique to examine and quantify the plastic deformation recorded by naturally shocked olivine in the low to moderately shocked ureilite meteorite Northwest Africa 2221 and the highly shocked martian dunitic cumulate meteorite Northwest Africa 2737, by assessing the types of subdomain boundaries and the increase of subdomain misorientation with increasing shock metamorphism. We further compare USL results for the shocked olivine in the meteorites with those for the terrestrial deformation of Hawaiian olivine. USL of olivine increases with shock level, and USL from shocked olivine is significantly greater than that of terrestrially deformed olivine. USL is a promising tool for the quantification of plastic deformation in large single crystals from shock as well as terrestrial deformation. The results derived from USL measurements along with local EBSD maps are complementary with quantitative 2D X-ray diffraction analysis of crystal deformation and disruption, leading to a more comprehensive understanding of characteristic shock deformation recorded by large single crystals.

Molecular dynamics study on defect evolution during the plastic deformation of nickel-based superalloy GH4169 single crystal under different rolling temperatures.

Nickel-based superalloy GH4169 is widely used as an important material in the aviation field. The rolling forming process can improve its surface quality and performance. Therefore, conducting an extensive investigation into the microscopic plastic deformation defect evolution process of nickel-based single crystal alloys during the rolling process is crucial. This study can offer valuable insights for optimizing rolling parameters. In this paper, a nickel-based superalloy GH4169 single crystal alloy was rolled at different temperatures from the atomic scale using the molecular dynamics (MD) method. The crystal plastic deformation law, dislocation evolution and defect atomic phase transition under different temperature rolling were studied. The results show that the dislocation density of nickel-based single crystal alloys increases as the temperature increases. When the temperature continues to increase, it is accompanied by an increase in vacancy clusters. When the rolling temperature is below 500 K, the atomic phase transition of the subsurface defects of the workpiece is mainly a Close-Packed Hexagonal (HCP) structure; when the temperature continues to increase, the amorphous structure begins to increase, and when the temperature reaches 900 K, the amorphous structure increases significantly. This calculation result is expected to provide a theoretical reference for the optimization of rolling parameters in actual production.

Complex severe plastic deformation of aluminum single crystal

A new route of severe plastic deformation – the complex shearing of extruded tube (CSET) technique – was proposed recently. In this route, a tube is produced from a rod via extrusion combined with two passes of an equal channel angular pressing like processing and with mandrel rotation. In the present paper, we describe and discuss the changes in the microstructure of an aluminum single crystal processed by CSET with respect to grain refinement, orientation changes and dislocation distribution.