Search

A method is proposed to measure the in-plane thermal diffusivity of anisotropic solids along an arbitrary direction using laser-line lock-in thermography. In this method, the sample is heated by an intensity-modulated laser beam, which impinges on the sample surface with the shape of a narrow strip. The resulting temperature oscillations are recorded by a thermographic camera and a phase thermogram is obtained by lock-in processing the image sequence. The thermal diffusivity along the direction perpendicular to the laser line can be determined from the linear dependence of phase lag with the distance to the heating line using the slope method. Unlike laser-spot lock-in thermography, in which the slope method only provides the thermal diffusivity along the principal directions, in this configuration, the thermal diffusivity can be measured experimentally along any direction, just selecting the relative orientation of the sample with respect to the laser line. Moreover, this configuration allows averaging several parallel phase profiles leading to more reliable thermal diffusivity values. The experimental results are presented for a highly anisotropic material, namely, a unidirectional carbon fiber-reinforced polymer plate. [ABSTRACT FROM AUTHOR]

An extension of a first-principle combined Monte Carlo method is proposed in this work to obtain the secondary electron emission characteristics of anisotropic crystal Al2O3. Unlike isotropic crystal Cu, density functional theory calculations reveal that the q-dependent energy loss function of Al2O3 in all directions is different. Therefore, an interpolation algorithm is introduced in the Monte Carlo method to determine the loss of energy and inelastic mean free path of electrons. The simulation results are in good agreement with experimental data. This method can be further used to simulate the secondary emission yield of other anisotropic crystal materials. [ABSTRACT FROM AUTHOR]

The high-pressure synthesis of double-core nanothreads derived from pseudo-stilbene crystals represents a captivating approach to isolate within the thread chromophores or functional groups without altering its mechanical properties. These entities can be effectively utilized to finely tune optical properties or as preferential sites for functionalization. Bibenzyl, being isostructural with other members of this class, represents the ideal system for building co-crystals from which we can synthesize double-core nanothreads wherein bridging chromophores, such as the azo or ethylene moieties, are embedded in the desired concentration within a fully saturated environment. To achieve this, a critical step is the preliminary characterization of the high-pressure behavior of crystalline bibenzyl. We report here an accurate investigation performed through state-of-the-art spectroscopic techniques, Raman and Fourier transform infrared spectroscopy, and x-ray diffraction up to 40 GPa. Our findings reveal a strongly anisotropic compression of the crystal, which determines, at pressures between 1 and 2 GPa, consistent modifications of the vibrational spectrum, possibly related to a torsional distortion of the molecules. A phase transition is detected between 9 and 10 GPa, leading to a high pressure phase where, above 24 GPa, the nanothread formation is observed. However, the observed reaction was limited in extent and required significantly higher pressures in comparison to other members of the pseudo-stilbene family. This comprehensive study is imperative in laying the foundation for future endeavors, aiming to synthesize double-core nanothreads from pseudo-stilbene crystals, and provides crucial insights into the high-pressure behavior and phase transitions of crystalline bibenzyl. [ABSTRACT FROM AUTHOR]

Textured Pb(Mg 1/3 Nb 2/3)O 3 –PbTiO 3 (PMN-PT) piezoelectric ceramics with an anisotropic crystal structure were fabricated by reactive templated grain growth (RTGG) using MgO-doped (Na 1/2 Bi 1/2)TiO 3 –PbTiO 3 (MNBT-PT) seed. The crystal growth of MNBT-PT seed was stimulated by the addition of MgO, resulting in a rectangular single-crystal template with a width of 5∼20 μm and a thickness of 3∼5 μm. These rectangular MNBT-PT seeds effectively reduced the sintering temperature of the PMN-PT matrix, and the reaction occurred through in-situ topochemical conversion, leading to a single perovskite phase with an oriented texture. Because the MNBT-PT seeds with tetragonal structure altered the crystal structure matrix phase to be tetragonal-rich, the matrix phase of PMN-PT had to be optimized by adjusting the PMN/PT ratio to achieve optimal piezoelectric properties. The textured PMN-PT piezoelectric ceramic created using the reactive MNBT-PT seeds demonstrated superior piezoelectric/ferroelectric properties (d 33 of 951 pC/N, k p of 0.64 and P r of 24.9 μC/cm2) compared to ceramics with BaTiO 3 (BT) seed made under the same conditions. This improvement is likely due to the formation of a textured single phase crystal structure. [ABSTRACT FROM AUTHOR]

In this article we analyze the thermal processes in magnetically anisotropic metal complexes under the action of non-adiabatic switching of magnetic field. Using the non-stationary perturbation theory for the case of sudden perturbation, we show that this field can cause not only heat release, but also heat absorption, interconnected with the axial zero field splitting (parameter D) in a paramagnetic metal complex. As an illustrative example we consider the simplest S = 1-complexes having "easy axis" and "easy plane" types of anisotropy influenced by the magnetic field that is suddenly turned off. We demonstrate that the character of the thermal processes (heat dissipation or absorption) depends on the sign of D and direction of applied field and so the analysis of these processes can be in principle used as a complementary tool (in addition to SQIUD magnetometry, EPR spectroscopy and INS) for studying magnetic anisotropy. The conditions under which the non-adiabatic switching of the magnetic field gives rise to the heat absorption are revealed. This unusual phenomenon, which can be called "nonadiabatic field switching cooling", may have practical applications. [ABSTRACT FROM AUTHOR]

Within angle‐resolved polarized Raman spectroscopy (ARPRS) experiments, ensuring accurate configurations is crucial for obtaining reliable results, especially when dealing with anisotropic materials like CrOCl with anisotropic crystal structure and phonon properties. However, comprehensive understanding of phase‐dependent ARPRS and the calibration of phase angle on anisotropic phonon modes from a crystallographic perspective are still lacking. Herein, detailed investigation on phase‐dependent ARPRS and looked into the anisotropic photo‐phonon interaction in CrOCl through in situ ARPRS is conducted. The Raman tensors and crystal orientation are acquired under two typical configurations. Phase‐dependent ARPRS are thoroughly analyzed for the calibration of analyzer deviation. The anomalous anisotropic response in phase‐dependent ARPRS is closely related to the intrinsic linear dichroism (LD) effect in CrOCl, which is further confirmed by angle‐resolved polarization absorption. Moreover, the strong localized rules for various parallel energy bands of CrOCl have generated anomalous LD conversion effect near 470 nm, which expands the potential application of CrOCl in polarization‐wavelength selected devices. This findings can offer in‐depth comprehension on the anisotropic phonon physics of CrOCl and a feasible approach to utilize phase‐dependent ARPRS for probing the undiscovered abundant photo‐induced effects in low‐symmetry 2D materials. [ABSTRACT FROM AUTHOR]

For a given class of materials, universal displacements are those displacements that can be maintained for any member of the class by applying only boundary tractions. In this paper, we study universal displacements in compressible anisotropic linear elastic solids reinforced by a family of inextensible fibers. For each symmetry class and for a uniform distribution of straight fibers respecting the corresponding symmetry, we characterize the respective universal displacements. A goal of this paper is to investigate how an internal constraint affects the set of universal displacements. We have observed that other than the triclinic and cubic solids in the other five classes (a fiber-reinforced solid with straight fibers cannot be isotropic), the presence of inextensible fibers enlarges the set of universal displacements. [ABSTRACT FROM AUTHOR]

LiNi x Co y Mn 1-x-y O 2 (NCM) has been regarded as promising cathode materials for high energy density lithium ion battery. Apart from the capacity deterioration during cycling process, NCM particle microcracks' generation resulting from anisotropic strain in crystal lattice is also regarded as the crucial issue from mechanical scale. As the original materials of synthesizing NCM, NCMOH precursor decides much of the prepared NCM materials in both electrochemical and mechanical scale while mechanical degrading mechanism inside crystal lattice is missing in related literature. In this study, the LiNi 0.7 Co 0.1 Mn 0.2 O 2 single crystalline particles are calcined from NCMOH precursors with difference in mechanical stacking morphology and physical property (specific surface area and tapping density) through the same appropriate sintering condition. The evolution of lattice microstrain calculation and elastic modulus for NCM materials through structure and mechanical evaluation has been studied. It is indicated that larger size and higher rate capability (fast charging) of single crystalline LNCMO materials can be obtained from precursor with smaller specific surface area and higher tapping density while the larger microstrain and less elastic modulus degradation are determined during electrochemical charging process. Stronger structure maintaining ability of NCM lattice under large electric field force (during fast charging process) is beneficial to the capacity performance related with higher-rate capability. This might provide a novel insight of understanding the mechanical effect of NCMOH precursors on the synthesis and electrochemical performance of Ni-rich LiNi x Co y Mn 1-x-y materials. [ABSTRACT FROM AUTHOR]

Magnesium titanate ceramics were prepared by reactive spark plasma sintering (SPS) at 1200 °C for 5 min. Prior to sintering, MgO and TiO 2 powders were mixed by high energy ball milling (HEBM) for 15, 30, or 60 min. The effect of milling time on phase composition was analyzed by X-ray diffraction (XRD) for milled powders and sintered specimens. The morphology of the sintered ceramics was investigated by scanning electron microscopy (SEM), while elemental distribution was determined by energy dispersive spectroscopy (EDS). The presence of the MgTi 2 O 5 phase was detected in XRD and was confirmed by EDS analysis. Microcracking was observed for specimens prepared with longer milling times and attributed to the coefficient of thermal expansion (CTE) mismatch dominantly due to the anisotropic crystal structure of MgTiO 3 phase. The sample milled for 15 min showed the highest Vickers hardness due to less or no microcracking and nearly full density. The dielectric measurements in the range of 10 Hz–250 MHz demonstrated extremely high dielectric permittivity, as high as 104 at 1 kHz. An increase in loss tangents was observed due to oxygen vacancy formation, which was promoted by the vacuum environment during SPS. Oxygen vacancy-related dielectric relaxation was also detected and explained. [ABSTRACT FROM AUTHOR]

Anisotropic 2D layered materials with distinctive anisotropic electronic band structures and optical response are promising for practical applications in polarization imaging and sensors. Nonetheless, many of the currently reported polarized photodetectors based on anisotropic 2D materials are constrained by the low polarization responsivity and low linear dichroism ratio. Here a high-performance polarization-sensitive photodetector based on the novel in-plane anisotropy 2D violet phosphorus (VP) crystal is reported. The angle-resolved polarized Raman spectroscopy (ARPRS) study and the anisotropic electrical transport measurements revealed the highly in-plane anisotropy phonon vibration and electrical properties of VP crystal. The anisotropic ratio of electron mobility is calculated to be 2.7 at room temperature. Moreover, a polarization-sensitive photodetector based on the VP nanosheet shows high photoresponsivity of up to 341 A W-1 and a linearly dichroic ratio of up to 3.9, which is much larger than most other anisotropic 2D materials. These results indicate that the anisotropic VP crystal would be suitable for polarization-sensitive photodetectors, which leads to a promising perspective for future novel electronic and optoelectronic devices. [ABSTRACT FROM AUTHOR]

Although anisotropic phononic crystals (PnCs) could be utilized to control the phonon dispersions and thermal transports, rapidly discovering their properties presents a significant challenge due to the enormous consumption of traditional computational methods. In this study, we have developed machine learning techniques to forecast the thermal conductance of anisotropic PnCs (GPnC and GPnC/Gmem) based on the elastic constants, taking conventional inorganic and halide perovskites as examples for their thermoelectric applications. Our findings suggest that predicting GPnC/Gmem is more challenging than predicting GPnC attribute to the complex influence factors and spatial distribution patterns of the former. The GPnC and GPnC/Gmem of the weakest thermal anisotropic materials—all hexagonals are invariants in the (0 0 1) plane, because the velocities in this plane are direction-independent. The GPnC and GPnC/Gmem of the strongest thermal anisotropic material FAPbI3 reaches the minimum and maximum values in [1 1 0] and [1 0 0] directions, respectively. Ultimately, our machine learning models can map the hidden complex nonlinear relationships between target thermal properties and mechanical features to provide valuable insight for accurate and efficient prediction and analysis of the thermal behaviors of PnCs at a mesoscopic level under low temperatures. [ABSTRACT FROM AUTHOR]

The aim of this paper is to propose a two‐stage theory‐based analytical method for the dynamic performance of pile groups in layered poroelastic saturated cross‐anisotropic soils induced by moving loadings. Among them, the free‐field vibrational analysis of saturated soils is performed by the analytical element‐layer approach (ALEA) and Fourier transformation. Based on the free‐field response, the boundary element (BE) solution for the soil resistance at the soil‐pile interface is derived utilizing the two‐stage theory. Simultaneously, the finite element (FE) solutions for the pile shaft resistance and deformation of pile groups are derived based on the Timoshenko beam theory. Finally, the FE‐BE coupled dynamic equation for deformations and internal loadings of the soil‐pile system is obtained. Thereafter, the reliability of the proposed method is validated by comparing with existing solutions and FE data from ABAQUS. Based on the derived solutions, a comprehensive parametric study is performed to examine the effects of loading amplitude, force speed, soft soil‐layer stiffness, soil anisotropy, and pile length on the dynamic responses of pile groups. [ABSTRACT FROM AUTHOR]

We report on measurements of the anisotropy of velocities and attenuation of GHz-frequency acoustic phonons in a cubic MgO crystal at room temperature. They are used to quantify the strong anisotropy of the Grüneisen parameter and calculate the attenuation anisotropy for Rayleigh surface acoustic waves. These observations constitute important building blocks for better understanding of ultrafast laser-based magneto-acoustic and nonlinear acoustic experiments at ultrahigh frequencies. [ABSTRACT FROM AUTHOR]

Advancements in low‐dimensional functional device technology heavily rely on the discovery of suitable materials which have interesting physical properties as well as can be exfoliated down to the 2D limit. Exfoliable high‐mobility magnets are one such class of materials that, not due to lack of effort, has been limited to only a handful of options. So far, most of the attention has been focused on the van der Waals (vdW) systems. However, even within the non‐vdW, layered materials, it is possible to find all these desirable features. Using chemical reasoning, it is found that NdSb2 is an ideal example. Even with a relatively small interlayer distance, this material can be exfoliated down to few layers. NdSb2 has an antiferromagnetic ground state with a quasi 2D spin arrangement. The bulk crystals show a very large, non‐saturating magnetoresistance along with highly anisotropic electronic transport properties. It is confirmed that this anisotropy originates from the 2D Fermi pockets which also imply a rather quasi 2D confinement of the charge carrier density. Both electron and hole‐type carriers show very high mobilities. The possible non‐collinear spin arrangement also results in an anomalous Hall effect. [ABSTRACT FROM AUTHOR]

The switching speed of light polarization plays a crucial role in determining the upper‐limit bandwidth of applications like optical communications and laser microscopy. However, conventional polarization elements based on macroscopic anisotropic crystals like birefringent crystals and chalcogenide glasses are either static or restricted by the low switching time of about hundreds of picoseconds. Here, a femtosecond‐scale all‐optical polarization controlling method is proposed through engineering the excited hot electrons in a graphene‐loaded metasurface. Remarkably, a giant polarization orientation from left‐handed polarization (LCP) to right‐handed polarization (RCP) in the Poincaré sphere (≈80° rotation) is realized within only 200 fs in the mid‐infrared. With pumping, the dedicated polarization‐sensitive design allows the metasurface to exhibit a consistent resonance blueshift as the transient increase of the hot‐electron temperature in graphene for y‐polarized incidence. This polarization conversion approach features a giant modulation range and enables the reflected light to be dynamically and arbitrarily modulated into RCP, LCP, and linear states at femtosecond timescale. A few logic operations "AND", "OR", "NAND", and "XOR" based on this method are also demonstrated by monitoring the normalized Stokes parameters. It is believed that this work may find practical application in next‐generation signal‐processing systems with large capacity. [ABSTRACT FROM AUTHOR]

The paper considers elastic anisotropic nano‐sheet with nanotopography and containing embedded nanocavities under time‐harmonic in‐plane wave motion. The mechanical model is based on the classical elastodynamic theory for the anisotropic bulk solid and the nonclassical boundary conditions along its boundary derived by Gurtin and Murdoch. A localized constitutive equation for the half‐plane boundary is considered in the frame of surface elasticity theory. The computational tool is an efficient direct displacement boundary element method (BEM) based on the frequency‐dependent elastodynamic fundamental solution for elastic generally anisotropic material. To show the versatility of the proposed methodology, wave propagation in an elastic anisotropic heterogeneous nano‐sheet with nanorelief presented by hill‐canyon nanotopography is studied. The simulations illustrate the dependence of the wave field on the material anisotropy, on the surface elasticity properties, on the nanorelief peculiarities, on the nanocavities existence and their dynamic interaction, and on the incident wave characteristics. The obtained results reveal the potential of the developed mechanical model based on the boundary integral equations in the frame of surface elasticity theory to produce highly accurate results by using strongly reduced discretization mesh in comparison with the domain‐based methods. [ABSTRACT FROM AUTHOR]

Consequences of incorporation of magnesium atom(s) on structural and optoelectronic properties of wurtzite cadmium sulphide have been investigated from first-principle calculations. Like direct (Γ–Γ) band-gap end binary wurtzite cadmium and magnesium sulphide semiconductors, such incorporation also results in stable direct (Γ–Γ) band-gap wurtzite MgxCd1−xS semiconductor ternary alloys with band-gaps residing in the UV spectral region. Lattice constants (a0, c0) of specimens within the w-MgxCd1−xS system nonlinearly reduce, while fundamental band-gap (Eg) enhances with increasing Mg content. Optical characteristics of optically anisotropic wurtzite crystals are studied mainly with ordinary and extraordinary components of real and imaginary parts of the complex dielectric function and some other dependent optical parameters. Electronic transitions from valence S-3p to Mg-4s, Mg-4p, Cd-5s and Cd-4p states of conduction band jointly result in optical features of the ternary alloys. Each uniaxial wurtzite crystal shows birefringence. Optical energy gap (Eopt) of each ternary alloy, higher than the corresponding Eg, lies in the UV region. Calculated components of static optical constants for ternary alloys become lower, but critical point energies become higher for larger band-gap specimen and vice versa. High optical absorption of direct band-gap ternary alloys in the UV region leads them as a compatible semiconductor for fabricating faster UV optoelectronic devices with high efficiency. [ABSTRACT FROM AUTHOR]

To develop smart ionic skins capable of multi‐responsiveness and switchable ionic conductivity, a stimuli‐responsive and ionic conductive azobenzene‐based monomer is newly synthesized, uniaxially oriented, and polymerized for anisotropic liquid crystal elastomers (LCEs). Since the uniaxially oriented monodomain LCE with ionic asymmetric azobenzene monomers (i‐AAM) is prepared by thermal oligomerization, uniaxial stretching, and subsequent photopolymerization, the stimuli‐responsive i‐AAM LCE is thermally contracted by increasing the temperature above TNI as well as is bent along the aligned direction by irradiating it with UV light. In addition to the change of shape, the ionic conductivity of the LCE is reversible in response to heat and light stimuli. Polydomain i‐AAM LCE polymerized without the stretching process exhibits higher ionic conductivity than stretched monodomain LCE due to the initially formed stable ionic pathways. Ionic conductivity can also be switched simultaneously by polarity changes in response to the photoisomerization of i‐AAM, increased mobility from heat, and an elastic mechanoresponse from external stresses. These i‐AAM LCE‐based soft grippers exhibit stimuli‐responsive grasping and releasing actuation and detect ionic conductivity switches finely, suggesting potential as smart skins for advanced soft robots. [ABSTRACT FROM AUTHOR]

The paper presents a comparative analysis of three systems of dynamic equations for fluid‐saturated solids: the exact equations and two simplified versions known as the u‐p approximations obtained by neglecting certain acceleration terms in the exact equations. The constitutive relations for the solid skeleton are written in the general anisotropic incrementally linear form without considering any specific constitutive model or a particular type of anisotropy. The dynamic equations are compared in relation to the existence of solutions in the form of plane harmonic waves. Emphasis is placed on finding conditions for the non‐existence or existence of growing waves whose amplitude increases in time or space as the wave propagates. The conditions are formulated in terms of the acoustic tensor of the skeleton and the compressibility of the pore fluid. In particular, it is shown that for a hyperelastic skeleton, the exact equations and one of the u‐p approximations do not have growing wave solutions, whereas the other u‐p approximation may have such solutions even if the skeleton is hyperelastic. [ABSTRACT FROM AUTHOR]

Understanding the growth of needle-shaped molecular crystals and the factors that influence the needle morphology is not only a fundamental research question but is also important in the design of industrial crystallization processes. Needle-like crystals have poor flow properties, are difficult to filter and to dry and – in the case of pharmaceuticals – difficult to formulate. While the morphology can often be controlled by changing the solvent, some compounds are persistent needle-formers that grow from all solvents as highly anisotropic crystals. In this highlight article we discuss the structural properties that lead to (persistent) needle growth. We also review strategies to modify the morphology such as the use of tailor-made additives, polymeric growth modifiers and cocrystallization. [ABSTRACT FROM AUTHOR]

In the framework of stationary anisotropic heat conduction (the Laplace-Beltrami equation) without heat sources, we investigate both theoretically and numerically the acceleration of the two iterative algorithms of Kozlov et al. (U.S.S.R. Computational Mathematics and Mathematical Physics 31:45–52, 1991) for the accurate, convergent and stable reconstruction of the missing temperature and normal heat flux on an inaccessible boundary of the domain occupied by a solid from the knowledge of Cauchy data on the remaining and accessible boundary. For each of the two algorithms with relaxation studied, this inverse Cauchy problem for the Laplace-Beltrami equation with exact data is transformed into an equivalent fixed point problem for an associated operator that is defined on and takes values in a suitable function space, and also accounts for the relaxation parameter. Consequently, the convergence of each relaxation algorithm reduces to analysing the properties of the corresponding operator and this enables us to determine the admissible range for the relaxation parameter, as well as a criterion for selecting its optimal value at each iteration, for each iterative procedure and exact Cauchy data. In case of perturbed Cauchy data, regularisation is achieved by terminating the iteration according to the discrepancy principle. The numerical implementation is realised for two-dimensional homogeneous anisotropic solids using the finite element method and confirms a significant reduction in the number of iterations and hence CPU time required for the two relaxation algorithms proposed to achieve convergence, for both exact and perturbed Cauchy data, provided that the dynamical selection of the optimal value for the relaxation parameter is employed. [ABSTRACT FROM AUTHOR]

Although the spin‐controlled vortex generation and photonic spin‐Hall effect of spin‐flipped abnormal mode have been widely studied recently, the traditional method based on the metasurface is difficult to fabricate, and the efficiency of the spin‐flipped abnormal mode is rather low due to process errors and intrinsic material loss. Here, a new method is proposed based on the insights into the topological singularity and special Bragger reflections resonant (BRR) mode of one‐dimensional (1D) finite photonic crystals (PhCs) with anisotropic material to realize nearly perfect (100%) spin‐conversion efficiency. For a finite 1D PhC with cell number N, there are 3N complete spin‐conversion (CSC) and complete spin‐maintained (CSM) channels. Two mechanisms of these CSC and CSM channels are revealed. The working bandwidths and the angular ranges of these CSC and CSM are also studied. Based on these theoretical findings, multi‐angles and multi‐frequencies perfect spin‐conversion (‐maintained) devices can be designed. At last, these theoretical results are confirmed by the numerical experiments based on finite‐difference time‐domain (FDTD) methods. This work paves the way to exploring the topological properties and polarization control of PhCs made of anisotropic dielectrics and provides a prospective method for the design of multi‐channels spin optical devices. [ABSTRACT FROM AUTHOR]

The anisotropic phase-filed model of grain boundary diffusion and precipitation of solute in nanocrystalline solids has been developed. In this model, the Cahn–Hilliard equation is generalized for the anisotropic phase-field diffusion of solute and anisotropic compositional fluctuations. It is found that dynamics of solute concentration profile demonstrates the anomalous diffusion behavior with scaling parameters depending on the mobility ratio and microstructure of a solid solution. It is noteworthy that the increase in source concentration can slow down the concentration front propagation due to uphill diffusion or formation of a new phase. Parameters of grain boundary diffusion control the precipitation dynamics. In particular, a decrease in transverse diffusion coefficient is responsible for longer incubation time, and lower rates of nucleation and nuclei growth in comparison with the case of isotropic solute transport near grain boundaries. Transport properties of boundary and bulk are responsible for the formation of the bimodal size distribution function of second phase particles and specific kinetics of average radius and number density. [ABSTRACT FROM AUTHOR]

The elastic field of an angular dislocation line that has a branch placed in a crystal of a bi-material while the other branch is along a strongly bound or welded interface, is found when the two crystals have anisotropic properties. Since the field of this angular dislocation depends on the elastic constants of the two crystals, it can be called hybrid dislocation (HD). To face this problem already treated using isotropic elasticity, the analysis first formulates the elastic field of a closed dislocation loop whose surface S is that of a circular sector centred in a point O of the interface. By virtue of the Saint Venant principle, when the circular segment moves far away from O, the field induced by the loop near O tends towards that of a HD. The calculation is possible thanks to the knowledge of the Green's tensor of the bi-material which has already been the subject of several works. Thanks to the use of polar coordinates, the solution is reduced to convenient line-integral expressions which make the calculation faster. This work complements a previous approach to the HD problem based on the integral formalism. By combining two HD's, it also gives the solution to the problem of an interfacial angular dislocation. Some applications illustrate anisotropy effects and highlight an inability of integral formalism to deal with a interfacial branch strictly in the interface. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to provide SIF calculation method for engineering application. Design/methodology/approach: In this paper, the stress intensity factors (SIFs) calculation method is applied to the anisotropic Ni-based single crystal film cooling holes (FCHs) structure. Findings: Based on contour integral, the anisotropic SIFs analysis finite element method (FEM) in Ni-based single crystal is proposed. The applicability and mesh independence of the method is assessed by comparing the calculated SIFs using mode of plate with an edge crack. Anisotropic SIFs can be calculated with excellent accuracy using the finite element contour integral approach. Then, the effect of crystal orientation and FCHs interference on the anisotropic SIFs is clarified. The SIFs of FCH edge crack in the [011] orientated Ni-based single crystal increases faster than the other two orientations. And the SIF of horizontal interference FCHs edge crack is also larger than that of the inclined interference one. Originality/value: The SIFs of the FCH edge crack in the turbine air-cooled blade are innovatively computed using the sub-model method. Both the Mode I and II SIFs of FCHs edge crack in blade increase with crack growing. [ABSTRACT FROM AUTHOR]

Phonon polaritons (PhPs) in 2D van der Waals (vdW) crystals exhibit strong spatial confinement and long polariton lifetimes, making them promising for developing novel nanophotonic devices at midinfrared frequencies. Here, using α‐phase molybdenum trioxide (α‐MoO3) microdisks, in‐plane anisotropic PhP resonances with degree of polarization (DoP) of almost 100% from far‐field observation are demonstrated. Such in‐plane polarization‐dependent PhP resonances, originating from the anisotropic crystal structure of α‐MoO3, are readily tuned by the disk length and fit well to numerical simulations. Findings show new possibility for engineering in‐plane polarizers based on vdW crystals and may promote the development of functional polarization‐sensitive optoelectronic devices at midinfrared frequencies. [ABSTRACT FROM AUTHOR]

Implementing high‐performance ultraviolet C photodetectors (UVC PDs) based on β‐Ga2O3 films is challenging owing to the anisotropic crystal symmetry between the epitaxial films and substrates. In this study, highly enhanced state‐of‐the‐art photoelectrical performance is achieved using single‐domain epitaxy of monoclinic β‐Ga2O3 films on a hexagonal sapphire substrate. Unlike 3D β‐Ga2O3 films with twin domains, 2D β‐Ga2O3 films exhibit a single domain with a smooth surface and low concentration of point defects, which enable efficient charge separation by suppressing boundary‐induced recombination. Furthermore, a tailored anti‐reflection coating (ARC) is adopted as a light‐absorbing medium to improve charge generation. The tailored nanostructure, which features a gradient refractive index, not only substantially reduces the reflection, but also suppresses the surface leakage current as a passivation layer. This study provides fundamental insights into the single‐domain epitaxy of β‐Ga2O3 films and the application of ARC for the development of high‐performance UVC PDs. [ABSTRACT FROM AUTHOR]

CdS‐based materials are extensively studied for photocatalytic water splitting. By incorporating Ag+ into CdS nanomaterials, the catalyst's charge carrier dynamic can be tuned for photo‐electrochemical devices. However, photo‐corrosion and air‐stability of the heterostructures limit the photocatalytic device's performance. Here, a one‐pot, single molecular source synthesis of the air‐stable AgCdS ternary semiconductor alloy nanostructures by heat‐up method is reported. Monoclinic and hexagonal phases of the alloy are tuned by judicious choice of dodecane thiol (DDT), octadecyl amine (ODA), and oleyl amine (OLA) as capping agents. Transmission electron microscope (TEM) and powder X‐ray diffraction characterization of the AgCdS alloy confirm the monoclinic and hexagonal phase (wurtzite) formation. The high‐resolution TEM studies confirm the formation of AgCdS@DDT alloy nanorods and their shape transformation into nano‐triangles. The nanoparticle coalescence is observed for ODA‐capped alloys in the wurtzite phase. Moreover, OLA directs mixed crystal phases and anisotropic growth of alloy. Optical processes in AgCdS@DDT nano‐triangles show mono‐exponential decay (3.97 ± 0.01 ns). The monoclinic phase of the AgCdS@DDT nanorods exhibits higher electrochemical hydrogen evolution activity in neutral media as compared to the AgCdS@ODA/OLA alloy nanocrystals. DDT and OLA‐capped alloys display current densities of 14.1 and 14.7 mA cm−2, respectively, at 0.8 V (vs RHE). [ABSTRACT FROM AUTHOR]

Structural dimensionality and electronic dimensionality play a crucial role in determining the type of excitonic emission in hybrid metal halides (HMHs). It is important but challenging to achieve free exciton (FE) emission in zero‐dimensional (0D) HMHs based on the control over the electronic dimensionality. In this work, a quasi‐0D HMH (C7H15N2Br)2PbBr4 with localized electronic dimensionality is prepared as a prototype model. With increasing pressure onto (C7H15N2Br)2PbBr4, the broad and weak self‐trapped exciton (STE) emission at ambient conditions is considerably enhanced before 3.6 GPa, which originates from more distorted [PbBr4]2− seesaw units upon compression. Notably, a narrow FE emission in (C7H15N2Br)2PbBr4 appears at 3.6 GPa, and then this FE emission is gradually strengthened up to 8.4 GPa. High pressure structural characterizations reveal that anisotropic contraction of (C7H15N2Br)2PbBr4 results in a noticeable reduction in the distance between adjacent [PbBr4]2− seesaw units, as well as an obvious enhancement of crystal stiffness. Consequently, the electronic connectivity in (C7H15N2Br)2PbBr4 is sufficiently promoted above 3.6 GPa, which is also supported with theoretical calculations. The elevation of electronic connectivity and enhanced stiffness together lead to pressure‐induced FE emission and subsequent emission enhancement in quasi‐0D (C7H15N2Br)2PbBr4. [ABSTRACT FROM AUTHOR]

Existing porothermoelastic models assume that shale is isotropic and disregard material anisotropy. When material anisotropy is considered, the shale-bedding plane must be assumed to be perpendicular to the borehole axis. However, in the actual drilling of shale reservoirs, the assumptions above are idealized to correctly identify the mechanisms of wellbore instability in shale reservoirs. Therefore, based on the generalized porothermoelastic theory and the generalized plane assumption, a pseudo three-dimensional finite element model that considers complete material anisotropy is established. The effects of elastic anisotropy, solid thermal expansion coefficient anisotropy, permeability anisotropy, thermal osmosis coefficient anisotropy, and thermal conductivity anisotropy on effective stress and pore pressure are analyzed parametrically. The following conclusions are based on ΔT = − 50 K (cooling) and kT > 0: when the permeability of the formation is less than 1e−19 m2, thermal osmosis governs the distribution of pore pressure. When the formation is drilled, the pore pressure distribution under elastic anisotropy differs completely from that under elastic isotropy. As time progresses, the pore pressure increases under the effect of hydraulic pressure; however, the higher the elastic anisotropy ratio, the faster the pore pressure increases. Additionally, the greater the elastic anisotropy ratio, the greater is the effective hoop stress. As time progresses, the elastic anisotropy ratio increases and the effective hoop stress decreases. The greater the elastic anisotropy ratio, the greater are the anisotropy ratio of the solid thermal expansion coefficient, the permeability anisotropy ratio, the thermo-osmotic anisotropy coefficient ratio, and the thermal conductivity anisotropy ratio, which is conducive to wellbore stability. Based on a quantitative evaluation of the parameter anisotropy, the elastic anisotropy exerts the greatest effect on wellbore stability. Highlights: A fully coupled anisotropic porothermoelastic model is proposed for inclined wells in shale formations. The distributions of the effective stress and pore pressure in elastic anisotropy differed entirely from those in isotropy. Thermal osmosis governs the pore pressure distribution in low-permeability shale formations. The anisotropies of the elasticity, thermal expansion, permeability, thermal osmosis, and thermal conductivity are parametrically analyzed. [ABSTRACT FROM AUTHOR]

Structural dimensionality and electronic dimensionality play a crucial role in determining the type of excitonic emission in hybrid metal halides (HMHs). It is important but challenging to achieve free exciton (FE) emission in zero‐dimensional (0D) HMHs based on the control over the electronic dimensionality. In this work, a quasi‐0D HMH (C7H15N2Br)2PbBr4 with localized electronic dimensionality is prepared as a prototype model. With increasing pressure onto (C7H15N2Br)2PbBr4, the broad and weak self‐trapped exciton (STE) emission at ambient conditions is considerably enhanced before 3.6 GPa, which originates from more distorted [PbBr4]2− seesaw units upon compression. Notably, a narrow FE emission in (C7H15N2Br)2PbBr4 appears at 3.6 GPa, and then this FE emission is gradually strengthened up to 8.4 GPa. High pressure structural characterizations reveal that anisotropic contraction of (C7H15N2Br)2PbBr4 results in a noticeable reduction in the distance between adjacent [PbBr4]2− seesaw units, as well as an obvious enhancement of crystal stiffness. Consequently, the electronic connectivity in (C7H15N2Br)2PbBr4 is sufficiently promoted above 3.6 GPa, which is also supported with theoretical calculations. The elevation of electronic connectivity and enhanced stiffness together lead to pressure‐induced FE emission and subsequent emission enhancement in quasi‐0D (C7H15N2Br)2PbBr4. [ABSTRACT FROM AUTHOR]

Polycrystalline materials have shown promise in advanced optical applications because of their unique optical and mechanical properties. Most polycrystalline materials have non‐uniform optical properties due to residual porosity, secondary phases, and/or crystalline anisotropies (e.g., birefringence). These optical inhomogeneities manifest as scattering that reduces the transparency of the polycrystal. Even in the case of a single‐phase polycrystal with negligible porosity, birefringence scattering will always be present whenever the crystal is anisotropic (non‐cubic). Multiple models for predicting birefringence scattering have been suggested in the literature that are successful in describing scattering loss in specific material systems. Here a first‐principles model of birefringent scattering that is applicable to any single‐phase, unaligned transparent polycrystal is derived. The model can treat grain size distributions and is not limited to a specific material system. The derivation culminates in an equation that describes birefringence scattering coefficient spectra using the single‐crystal refractive index tensor and chord length distribution (measured from a representative polished surface micrograph). The model should be useful for designing materials and characterization. For example, it can be used to predict transmissions of transparent polycrystals for a range of grain sizes or to characterize the average grain size using a transmission measurement. [ABSTRACT FROM AUTHOR]

During determination of the thiocyanate dehydrogenase (TcDH) structure difficulties have occurred, related to the fact that enzyme crystals have been either twinned or strongly anisotropic. The diffraction quality of crystals can be improved by using mutant forms as objects of a study or by studying the structure of a related enzyme from another organism. Based on the analysis of the oligomeric structure of TcDH, the mutant forms of the enzyme that are promising for improving the diffraction properties have been proposed. The crystals have been obtained and the structures of the TcDH mutant forms with the substitutions T169A and K281A have been solved. The structure of the mutant form with the substitution T169A is found to be similar to the previously solved structures. In the structure of the mutant form with the substitution K281A, a change in the tetramer structure that made twinning impossible has been detected. [ABSTRACT FROM AUTHOR]

Constitutive equations of continuum mechanics of the solid phase of anisotropic material is focused in the paper. First, a synoptic one-dimensional Maxwell model is explored, subjected to arbitrary deformation load. The explicit form is derived for stress on strain dependence. Further, the analogous explicit constitutive equation is taken in three spatial dimensions and treated mathematically. Later on, a simply supported straight concrete beam reinforced by the steel fibres is taken as an investigated domain. The reinforcement is considered and dealt as scattered within the beam. Material characteristics are determined in line with the theory of the reinforcement. Sinusoidal load is taken as the action, stress reaction function is observed. By exploitation of the Fourier transform within the stress-strain relation analysis, both time and frequency interpretation of the constitutive relation can be performed. [ABSTRACT FROM AUTHOR]

We investigate the bound states in the continuum (BICs) in photonic crystal slabs composed of alternating anisotropic and isotropic dielectric materials. According to the orientation of optical axis plane, three different configurations are proposed for analyzing various types of BICs, associated with extremely large quality factors and vanishing spectral linewidths. In particular, symmetry-protected (SP) BICs exist at the Brillouin zone center for zero rotation angle of the optical axis, which exhibit antisymmetric field patterns that are decoupled from the symmetric radiating fields. Accidental BICs and Friedrich-Wintgen (FW) BICs also occur at the Brillouin zone center for particular rotation angles of the optical axis. The former emerge on isolated bands with quasi-symmetric or quasi-antisymmetric field patterns, while the latter appear near the avoided crossing between two dispersion bands. At off the Brillouin zone center, SP BICs do not exist while accidental BICs and FW BICs appear at particular optical axis rotation angles, with similar features but somewhat more asymmetric field patterns than those at the Brillouin zone center. [ABSTRACT FROM AUTHOR]

High-performance bi-functional materials are in urgent demand for the next-generation integrated optical devices. In this work, we successfully synthesized the first tricyanomelaminate with bi-functional optical responses, namely Cs3C6N9·H2O (I), from its analogue Na3C6N9·3H2O by a facile ion exchange method. In contrast to Na3C6N9·3H2O, I realizes an optimal arrangement of π-conjugated (C6N9)3− anion groups in its crystal structure. As a result, the second-order nonlinear optical (NLO) response is greatly enhanced from nearly zero of Na3C6N9·3H2O to ∼9.8 × KH2PO4 of I. Furthermore, I exhibits a giant linear optical anisotropic response (i.e. birefringence) of 0.52 at the wavelength of 550 nm. Both responses are almost the largest among the inorganic compounds of π-conjugated rings, which indicates that I has great potential as a bi-functional optical crystal. Structural and theoretical analyses reveal the microscopic origin of excellent optical properties. This work would attract a lot of interest to the persistently neglected potential of tricyanomelaminates as linear optical and NLO crystals. [ABSTRACT FROM AUTHOR]

Chalcopyrite (CuFeS2) particles, exposing anisotropic crystal planes during the grinding process, possess comprehensive surface properties that affect their leaching behaviors. In order to investigate the influence of anisotropic crystal planes on the leaching mechanisms, CuFeS2 particles with anisotropic crystal planes were produced by employing three-head laboratory grinder mill (TM), rod mill (RM), and ball mill (BM) and were then leached in a sulfuric acid solution at pH = 1. Based on the XRD, SEM, XPS, and simulation results, (112), (102), (312), (110), (116), (100), and (001) planes were mainly exposed on the CuFeS2 surface during the crushing and grinding process. In addition, fewer (112), (102), (312), and (110) planes but more (116), (100), and (001) planes were exposed on the CuFeS2 samples in the TM method than in the RM and BM methods. Since the leaching rates were in the order of (001) > (100) > (116) > (110) > (312) > (102) > (112) planes, the Cu extractions followed an order of TM > RM > BM. This study, therefore, provides an excellent theoretical basis for the effect of anisotropic crystal planes on CuFeS2 leaching, further improving the understanding of CuFeS2 leaching mechanisms. [ABSTRACT FROM AUTHOR]

Recently, by forming a P‐rich P–S system, the P3S monolayer has been predicted to have good resistance to air oxidation, large band gap, high absorption, and superior mobility. Inheriting this prediction, a series of ternary Janus P6XY (X/Y = S, Se, and Te; X ≠ Y) monolayers based on P3X nanosheet are designed and studied. The structures of P6XY monolayers are confirmed to be stable based on the evaluation of calculated results for phonon spectra, ab initio molecular dynamic simulations. It is also found that P6XY compounds possess anisotropic mechanical characteristics. All Janus structures are indirect semiconductors with large energy gaps varying from 2.12 to 2.60 eV calculated by the hybrid functional. Besides, biaxial strain significantly affects the electronic properties of the P6XY monolayers. In particular, the biaxial strains can induce a transition from indirect to direct bandgap in all three P6XY structures. The carrier mobility in the three proposed structures exhibits directional anisotropy and high electron mobility value, up to 1.27 × 103 cm2 V−1 s−1, which are suitable for applications in high‐performance and direction‐dependent nanoelectronic devices. [ABSTRACT FROM AUTHOR]

Nitroguanidine (NQ) in solvent-based triple-base propellants (STP) has a propensity to peel off and detach from the matrix, leading to significant defects, such as interface debonding within the propellant’s microstructure. This ultimately results in reduced and unstable mechanical properties. To address this critical issue, an efficient and eco-friendly manufacturing process was employed to successfully produce solventless triple-base propellants (SLTPs) as a comparison to conventional STPs. SLTP samples exhibit a mutually supportive three-dimensional spatial structure, with NQ crystals within the propellant matrix more securely bonded to the interface. They also demonstrate higher relative density (1.68 g⋅cm−3 ), more stable molding dimensions (no contraction), and enhanced tensile strength (41.92 MPa). Quasi-static structural failure tests reveal that the standard deviation of compressive strength for SLTP samples in three axes is smaller, registering at 1.10. The dynamic structural damage performance analysis indicates that the failure of energetic composite materials is attributable to separation fracture damage after the appearance of cracks on the tensile surface at −40 and 25°C. Furthermore, the structural failure of these materials occurs due to significant collapse failure after the compression surface bends inward at 50°C. Consequently, the present study offers a reliable theoretical foundation and procedural strategy for enhancing the structural strength of triple-base propellants. [ABSTRACT FROM AUTHOR]

Kinetics of singlet fission (SF) in molecular semiconductors, i.e., spontaneous splitting of the excited singlet state into a pair of triplet (T) excitons, is known to be strongly affected by geminate annihilation of created TT-pairs. In our work, we analyze in detail the specific properties of SF-kinetics in highly anisotropic molecular crystals (in which T-excitons undergo strongly anisotropic hopping migration) within the earlier proposed two-state model (TSM). This model allows for accurate treatment of the characteristic effects of anisotropic relative migration of T-excitons and TT-interaction on SF-kinetics, describing these effects within the approximation, that assumes kinetic coupling of two states: the [TT]-state of interacting TT-pairs and the [T + T]-state of freely migrating T-excitons. The TSM makes it possible to represent the TT-migration and interaction effects in terms of lattice-migration Green's functions, accurate analytical formulas that are obtained in this work. The TSM is applied to the analysis of SF-kinetics in rubrene single crystals, recently measured in a wide range of times (0.1 ns < t < 104 ns). The analysis enables one to obtain important information on specific properties of SF-kinetics in highly anisotropic crystals. In particular, the observed specific "hump" of SF-kinetics at intermediate times can be treated as a manifestation of the TT-coupling in the [TT]-state. It is also found that the characteristic asymptotic time-dependence of SF-kinetics (∼ t − 3 / 2 ) can markedly be distorted by spin relaxation in TT-pairs. [ABSTRACT FROM AUTHOR]

Large single crystals of rare-earth calcium oxoborates R Ca 4 O (BO 3) 3 with R = Er , Y, Dy, Gd, Sm, Nd, La (R C O B) were grown by the Czochralski method. Complete sets of dielectric, piezoelectric stress, and elastic stiffness coefficients of the R C O B crystal species were determined at ambient conditions using a combination of resonant ultrasound spectroscopy and the substitution method. The results are inherently consistent and reveal clear crystal chemical trends, with the size of the trivalent cation playing an important role. In particular, the longitudinal and shear aggregate elastic stiffnesses, c 11 iso and c 44 iso , decrease from about 165 to 154 GPa and, respectively, 45 to 41 GPa from the smallest to the largest R 3 + cation of the investigated crystal species, while the dielectric coefficients ϵ 22 and ϵ 33 increase. However, the maximum longitudinal piezoelectric effect peaks with 8.6 pCN − 1 at N d C O B , the species where the radius of R 3 + best matches the one of Ca 2 + . Increasing differences in the size of R 3 + and Ca 2 + lead to anisotropic stresses in the crystal lattice, which are partially relaxed by an increasing degree of cation disorder. [ABSTRACT FROM AUTHOR]

A negative linear temperature expansion and a negative linear compressibility were observed for imidazolium benzoate salt. Its strongly anisotropic strain induced by the temperature and pressure changes has been explained by the mechanism of H-bonded helices deformed in the structure. X-ray diffraction and vibrational spectroscopy were used to analyze interactions in the crystal. The Quantum Theory of Atoms in Molecules (QTAiM) approach was applied to analyze the hydrogen bonds and other interactions. In the salt under study, the interactions within the helix are substantially higher in energy than between helices. With decreasing temperature and increasing pressure, the value of the helix pitch increases while the value of the semi-major axis decreases, which results in the negative linear expansion and negative linear compression, respectively. [ABSTRACT FROM AUTHOR]

X-ray diffraction techniques are widely used to estimate stresses within polycrystalline materials. The application of these techniques requires the knowledge of the X-ray elastic constants relating the lattice strains to the stress state. Different analytical methods have been proposed to evaluate the X-ray elastic constants from the single-crystal elastic constants. For a given material, such methods provide the bulk X-ray elastic constants but they do not consider the role of free surfaces. However, for many practical applications of X-ray diffraction techniques, the penetration depth of X-rays is the same order of magnitude as the grain size, which means that the influence of the free surface on X-ray elastic constants cannot be excluded. In the present work, a numerical procedure is proposed to evaluate the surface and bulk X-ray elastic constants of polycrystalline materials. While the former correspond to the situation where the penetration is infinitely small in comparison with the grain size, the latter are representative of an infinite penetration depth with no free-surface effect. According to numerical results, the difference between surface and bulk X-ray elastic constants is important for strongly anisotropic crystals. Also, it is possible to propose a relation that allows evaluating X-ray elastic constants as a function of the ratio between the penetration depth and the average grain size. The corresponding parameters of such a relation are provided here for many engineering materials. [ABSTRACT FROM AUTHOR]

Herein, amorphous manganese dioxide (AMO) is prepared by the liquid‐phase coprecipitation method, the effect of heat treatment temperature on the microstructure, and phase composition of AMO and the electrochemical properties as cathode materials for aqueous Zn–MnO2 batteries are investigated. The results show that the AMO didn't crystallize at 250 °C, but its structure stability increases. When the temperature is 350 and 400 °C, part of the AMO crystallizes into rod‐shaped nano‐α‐MnO2 crystals. At 540 °C, the products crystallize into nano‐α‐MnO2 crystals. Continuing to increase the temperature to 650 °C, the structural stability of the products is further improved. Heat treatment leads to reduced specific surface area and porosity of the material, which in turn leads to reduced specific capacity and cycling stability. In addition, the heat‐treated products show a sharp drop in capacity during the discharge process; this was because the volume change caused by the irreversible phase change of the electrode material is difficult to release in the anisotropic crystal, resulting in the collapse of the structure. This study shows that unheated AMO is better than heat‐treated AMO as a cathode material for aqueous Zn–MnO2 battery cathode material in terms of overall performance and cost. [ABSTRACT FROM AUTHOR]

In this paper, we present a variant of the second gradient continuum model that allows description of the spatial dispersion effects of high-frequency waves in anisotropic crystals. The considered model takes into account the strain and inertia gradient effects and the classical electro-mechanical coupling. The simplified constitutive equations of the model contain seven and four length scale parameters for piezoelectric hexagonal crystals and elastic cubic crystals, respectively. It is shown that all except one length scale parameter can be identified based on the fitting of the continuum model to the lattice dynamics calculations for the dispersion relations of the bulk acoustic phonons. Examples of the identification are presented for hexagonal piezoelectric ZnO and AlN and for cubic diamond and Si crystals. Using a calibrated model, we then obtain the dispersion relations for the high-frequency Bleustein–Gulyaev wave in piezoelectric crystals and for the shear horizontal surface wave in elastic crystals. The last one is predicted by the gradient models only for the high frequencies, while at low frequencies this wave degenerates to the bulk shear wave. Examples of calculations are also provided for the Rayleigh wave propagating through the homogeneous piezoelectric half-space and layered ZnO(AlN)/diamond/Si structures. It is shown that this kind of surface wave can be used to identify the last unknown length scale parameter of the model. [ABSTRACT FROM AUTHOR]

Acousto-optic (AO) interaction in optically biaxial crystals is of great interest due to the variety of phase matching geometries caused by the low symmetry of the acoustic, optical, and photoelastic properties. The current state of the research in the field of acousto-optics of biaxial crystals is presented. Some promising biaxial crystals of the orthorhombic and monoclinic systems, which are of practical interest as materials for AO devices, are considered. The unique geometries of isotropic and anisotropic diffraction that exist in only biaxial crystals are analyzed, and the AO devices based on these crystals are briefly reviewed. [ABSTRACT FROM AUTHOR]

In this paper, the problem of deformation induced by an open pit excavation in anisotropic stiff soils is analysed by FE modelling. The presented research is focused on the influence of material model with anisotropic stiffness on the accuracy of deformation predictions as compared with the field measurements. A new hyperelastic-plastic model is applied to simulate anisotropic mechanical behaviour of stiff soils. It is capable to reproduce mixed variable stress-induced anisotropy and constant inherent cross-anisotropy of the small strain stiffness. The degradation of stiffness depending on strain is modelled with the Brick-type model. The model formulation and parameters are briefly presented. General deformation pattern obtained in the exemplary 2D boundary value problem of an open pit excavation is investigated considering different values of inherent cross-anisotropy coefficient of small strain stiffness. The numerical simulations are performed as a coupled deformation-flow analysis which allows to properly model the drainage conditions. The excavation phases are simulated by removal of soil layers according to the realistic time schedule. Finally, the monitored case of the trial open pit excavation in heavily overconsolidated Oxford Clay at Elstow, UK is simulated with proposed material model both in 2D and 3D conditions. The obtained calculation results are compared with displacement measurements and discussed. [ABSTRACT FROM AUTHOR]

We discuss the Goldstone mode of skyrmion crystal in a model of two-dimensional ferromagnet with the Dzyaloshinskii–Moriya interaction in magnetic field. We use stereographic projection approach to construct skyrmion crystal and consider skyrmion displacement field. The small overlap of the individual skyrmion images restricts the potential energy to the interaction of nearest neighboring displacements. The closed form of the Goldstone mode dispersion is found and its dependence on the magnetic field is studied. We use semiclassical quantization to define the Green's function and show that the propagation of displacements through the crystal changes its tensorial form from anisotropic to isotropic one at large times. [ABSTRACT FROM AUTHOR]

The emergence of new materials and fabrication techniques provides progress in the development of advanced photonic and communication devices. Transition metal dichalcogenides (e.g., molybdenum disulfide, MoS2) are novel materials possessing unique physical and chemical properties promising for optical applications. In this paper, a metasurface composed of particles made of bulk MoS2 is proposed and numerically studied considering its operation in the near‐infrared range. In the bulk configuration, MoS2 has a layered structure being a uniaxial anisotropic crystal demonstrating an optical birefringence property. It is supposed that the large‐scale and uniform MoS2 layers are synthesized in a vertical‐standing morphology, and then they are patterned into a regular 2D array of disks to form a metasurface. The natural anisotropy of MoS2 is utilized to realize the splitting of electric and magnetic dipole modes of the disks while optimizing their geometric parameters to bring the desired modes into overlap. At the corresponding resonant frequencies, the metasurface behaves as either an electric or a magnetic mirror, depending on the polarization of incident light. Based on the extraordinary reflection characteristics of the proposed metasurface, it can be considered an alternative to traditional mirrors and optical splitters when designing compact and highly efficient metadevices, which provide polarization and phase manipulation of electromagnetic waves on a subwavelength scale. [ABSTRACT FROM AUTHOR]