Anisotropy Factor Research Articles

Insights of anisotropic compact stellar structures in f(R, T) theory

Abstract This study formulates two distinct non-singular interior solutions that characterize anisotropic spherical structures in the context of f(R, T) theory. We formulate the modified Einstein field equations alongside the corresponding anisotropic factor associated with a static interior spacetime. The field equations are then addressed by implementing two unique constraints that facilitate to solve a system. By adopting specific forms of pressure anisotropy, we derive two different solutions. In both scenarios, we encounter differential equations whose solutions incorporate integration constants which are determined by equating the metric functions of an interior metric with those of the Schwarzschild exterior metric at the boundary of the sphere. The condition of zero radial pressure at the hypersurface also plays a crucial role in this regard. Subsequently, we explore specific conditions that, when met, yield physically feasible compact models. To graphically assess them, we take into account the estimated data of a star, namely SAX J 1808.4-3658 along with different values of the model parameter. Our findings indicate that both stellar solutions align well with the physically existence criteria under certain parametric values.

Switchable planar chirality and spin texture in highly ordered ferroelectric hybrid perovskite domains

Chiral organic-inorganic hybrid perovskites offer a promising platform for developing non-linear chiro-optical applications and chiral-induced spin selectivity. Here, we show that achiral hybrid perovskites that have highly ordered ferroelectric domains with orthogonal polarization exhibit planar chirality, as manifested by second harmonic generation with strong circular dichroism. Interestingly, the handedness of the second harmonic generation circular dichroism response can be alternatingly switched between orthogonally polarized domains and domain walls. To correlate the origin of planar chirality in these domains, atom-resolved atomic force microscopy is used to reveal distinct arrangements of atomic rows in these ferroelectric crystals that indicate planar symmetry breaking. Remarkably, a large SHG anisotropy factor of 0.41 is measured at the domain wall. Additionally, spatially resolved two-photon photoluminescence excitation measurement provide evidence of larger Rashba spin-splitting in these chiral ferroelectric domains compared to domain-free areas. Our discoveries of domain-dependent planar chirality and spin texture hold great promise for advancement of domain-specific chiro-optical applications.

Inducing Efficient and Multiwavelength Circularly Polarized Emission From Perovskite Nanocrystals Using Chiral Metasurfaces.

Chiral nano-emitters have recently received great research attention due to their technological applications and the need for a fundamental scientific understanding of the structure-property nexus of these nanoscale materials. Lead halide perovskite nanocrystals (LHP NCs) with many interesting optical properties have anticipated great promise for generating chiral emission. However, inducing high anisotropy chiral emission from achiral perovskite NCs remains challenging. Although chiral ligands have been used to induce chirality, their anisotropy factors (glum) are low [10-3 to 10-2]. Herein, the generation of high anisotropy circularly polarized photoluminescence (CPL) from LHP NCs is demonstrated using chiral metasurfaces by depositing nanocrystals on top of prefabricated resonant photonic structures (2D gammadion arrays). This scalable approach results in CPL with glum to a record high of 0.56 for perovskite NCs. Furthermore, the differences between high-index dielectric chiral metasurfaces and metallic ones are explored for inducing chiral emission. More importantly, the generation of simultaneous multi-wavelength circularly polarized light is demonstrated by combining dielectric and metallic chiral metasurfaces.

Edge dislocations, alloy composition, and grain boundaries effects on the mechanical properties in NiCo binary alloy

In this research, we investigated the mechanical properties of NiCo binary alloy both with and without grain boundaries, across various alloy compositions. We investigated the effects of edge dislocation, alloy compositions, and grain boundaries on the mechanical properties of FCC NiCo\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$NiCo$$\\end{document} using molecular dynamics (MD) simulations. By analyzing the influence of the grain boundaries with different alloy compositions on several mechanical properties, we were able to gain a deeper understanding of how these characteristics were modified. The elastic moduli increased with increasing grain boundaries for a specific chemical composition, indicating that NiCo\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$NiCo$$\\end{document} becomes more rigid. The anisotropy factor analysis showed that NiCo\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$NiCo$$\\end{document} have a natural tendency toward anisotropy, which is further influenced by the presence of grain boundaries. Grain boundaries have a significant effect on strength and ductility across a wide range of alloy compositions. These results indicate that a deeper comprehension of these implications can aid in designing improved binary alloy with superior mechanical characteristics.

Estimation of Scattering Properties Modifications Caused by InVivo Human Skin Optical Clearing Using Line-Field Confocal Optical Coherence Tomography.

The image contrast and probing depth of optical methods applied to invivo skin could be improved by reducing skin scattering using the optical clearing method. The aim of this study was to quantify, from line-field confocal optical coherence tomography (LC-OCT) 3D images, the modifications of skin scattering properties invivo during optical clearing. Nine mixtures of optical clearing agents were used in combination with physical and chemical permeation enhancers on the human skin of three healthy volunteers. Scattering coefficient and anisotropy factor of the epidermis and the upper dermis were estimated from the 3D LC-OCT images of skin using an exponential decay model of the in-depth intensity profile. We were able to demonstrate a decrease in epidermal scattering (down to 33%) related to optical clearing, with the best results obtained by a mixture of polyethylene glycol, oleic acid, and propylene glycol.

Relativistic model for anisotropic compact stars in embedding class-I spacetime

In the present article, we introduce a completely new regular model for static, spherically symmetric celestial fluid spheres in embedding class I spacetime. In this regard, needfully, we propose a new suitable metric potential e λ(r) to generate the present model. The various analyses on energy density, pressure, anisotropic factor, mass, compactness parameter, redshift, and energy condition make sure the model is physically viable on the ground of model stars Vela X-1, Cen X-3, SMC X-4, and LMC X-4. The reported solutions also respect the equilibrium state by satisfying the Tolman–Oppenheimer–Volkoff (TOV) equation and ensure stability by satisfying the causality condition, condition on the adiabatic index, and Harrison–Zeldovich–Novikov condition. The generated M − R graph matches the ranges of masses and radii for the model compact stars. Additionally, this study provides estimates of the moment of inertia based on the I − M graph.

Significant Chiral Asymmetry Observed in Neutral Amino Acid Ultraviolet Photolysis.

The origin of homochirality in biological organisms remains an open question. Some suggest that its origin might be extraterrestrial, specifically due to the exposure of chiral molecules to circularly polarized photons in interstellar space, which could cause an initial population imbalance leading to the homochirality observed today. However, this extraterrestrial hypothesis has not been widely accepted, largely due to the belief that molecular optical rotatory dispersion is too insignificant to create the substantial imbalance required for homochirality. Here we report experimental evidence that specific conformers of neutral amino acids exhibit significant asymmetry in the chiral destroying dissociation rate induced by circularly polarized photons. The observed anisotropy factor for the lowest energy conformer of leucine was remarkably large, reaching 0.1─a factor of 13 times larger than observed for zwitterionic leucine in solid films, and nearly 40 times greater than the anisotropy reported in the electronic absorption spectrum of gas-phase leucine ensembles at room temperature. This significant finding indicates that even if reported anisotropy values in the electronic absorption spectrum are low, the dissociation asymmetry of certain conformers can still be substantial. An anisotropy factor of 0.1 could result in an initial enantiomeric excess exceeding 10%, even with a 90% extent of reaction. This discovery suggests that asymmetric photodissociation of amino acids may have been a crucial factor in the emergence of biological homochirality.

Research on the Anisotropy of the Thermal Conductivity of Sandstone Heritage via Digital Rock Physics Under Various Pore Media

ABSTRACT The thermal conductivity of sandstone heritage has been emphasized as one of the crucial factors affecting the weathering, in order to further investigate the anisotropy of the thermal conductivity of sandstone at the microscale. In this study, the thermal conductivity of the sandstone samples is measured using the laser flash method. Next, micro-CT images are utilized to reconstruct the digital rock, randomly selected different sizes of REVs (130 × 250 * 250, 100 × 100 * 100, 50 × 50 * 50 voxels) are taken from the reconstructed digital rock. Thermal simulations are then conducted on these REVs in different directions and under steady-state conditions for three pore-filling phases (air, water, and ice). An anisotropic model is introduced to evaluate the thermal conductivity anisotropy of the REVs. Finally, the overall analysis reveals that the pore-filled phase changes from air to water and finally to ice result in an increase of the thermal conductivity of the digital rocks; Additionally, as the thermal conductivity of the filling phase increases, the digital rock progressively transitions towards isotropy. As the porosity of the digital rocks increases, the thermal conductivity decreases and the thermal anisotropy factor diverse further from 1. Changes in REV size has an insignificant effect on the thermal conductivity; however, an increase in the REV size causes the anisotropy factor closer to 1. It is expected the innovative method reported in the present work can provide a feasible and reliable alternative for studying the thermal anisotropy and delaying weathering in stone heritage.

First‐Principles Study of Structural and Elastic, Electronic, and Thermoelectric Properties of PdSe2

The thermoelectric material in orthorhombic (Pbca) phase is studied with the help of density functional theory implemented in WIEN2k. The main properties of investigated are elastic, electronic, and thermoelectric properties. The anisotropy factors obtained with the elastic constants indicate that is strongly anisotropic. The Tran and Blaha‐modified Becke–Johnson exchange potential is used for bandgap calculations. The BoltzTraP code is used to find out the thermoelectric properties of . At 300 K, the maximum value of the Seebeck coefficient is 200 μV K−1 for the hole carrier concentration of 2.5 × 1019 cm−3 and is 241 μV K−1 for the electron carrier concentration of 1.2 × 1019 cm−3. The power factor (PF) and figure of merit (ZT) are calculated for different carrier concentrations and temperatures. The optimum value of ZT for bulk PdSe2 as calculated in this work is ≈0.6 for hole carrier concentration (p = 2.6 × 1020 cm−3) at 800 K, which suggests as a potential material in thermoelectric applications at higher temperatures.

Strain effect on the physical properties of novel Mg3NI3 perovskite material: First principle DFT analysis

Inorganic perovskite-based substances have become a major attraction to solar technology. Inorganic cubic Mg3NI3 perovskites have generated a heap of fascination owing to their distinctive optical, electrical, and structural features. The photovoltaic and optoelectronic industries prioritize lead-free, atomically tailored metal halide perovskites due to the need to address lead (Pb) toxicity and instability. This study assessed the optical, structural, and electrical parameters of Pb-free inorganic halide perovskites Mg3NI3 as a function of biaxial compressive and tensile strain, leveraging first-principles density-functional theory (FP-DFT). Refractive index, absorption coefficient, reflectivity, dielectric function, and tolerance factor are a few additional optical parameters that are computed and processed. The bandgap of the planar Mg3NI3 molecule is 0.412 eV (PBE) when SOC is not applied. The bandgap reduces to 0.363 eV (PBE) at its Γ(gamma) and R-point when the subjective SOC effect is taken into consideration. This compound's bandgap will narrow under tensile strain and expand under compressive strain, depending on whether the SOC effect is applied or not. Several elastic factors are anticipated, including the bulk modulus, Pugh's ratio, elastic constants, anisotropic factors, and Poisson's ratio. Electronic property calculations using band mechanism and density of states (DOS) suggest that Mg3NI3 have a bandgap that is indirect and semiconductive. The elastic properties of this material were found to be mechanically stable, anisotropic, and ductile. In the photon energy range suitable for solar cells, the spikes in the dielectric constant of Mg3NI3 are seen. Our findings point to the prospect of Mg3NI3 as a non-toxic, high-performance, low-cost material for implementation in solar cells and different semiconductor devices.

Emergence of Optical Activity and Surface Morphology Changes in Racemic Amino Acid Films Under Circularly Polarized Lyman-α Light Irradiation.

The homochirality of life remains one of the most enigmatic issues in the study of the origin of life. A proposed mechanism for symmetry breaking involves irradiation by circularly polarized light (CPL). To investigate the photoreaction of amino acids under CPL irradiation, a vacuum ultraviolet (VUV) CPL irradiation system was developed at the synchrotron light source UVSOR-III. Hydrogen Lyman-α CPL (121.6 nm) is considered a potential asymmetric source in space. Therefore, racemic alanine film samples were irradiated with Lyman-α CPL to explore the photoreaction of biomolecules. Circular dichroism (CD) spectra measurements revealed that irradiation with right- (left-) handed CPL induced a positive (negative) anisotropy factor g in the wavelength range of 180-240 nm. However, the spectra differed from those of enantiopure alanine, exhibiting broad wavelength ranges and no sign change. Liquid chromatography-mass spectrometry (LC-MS) measurements indicate formation of larger molecules, such as oligomeric alanine adducts or modified oligomers after the Lyman-α CPL irradiation. Additionally, CPL irradiation considerably changes the microstructure of the alanine film surface, leading to the formation of circular network aggregates on the scale of 100 nm. The morphology changes in the alanine film and/or the formation of the larger molecules could be possible causes of the modified anisotropy factor spectra compared to those of enantiopure alanine. These findings highlight the need for further research on the photoreaction of biomolecules in solid states under VUV CPL irradiation, particularly in the photoionization energy range, to validate the cosmic scenario of homochirality.

A comparative study on the physical properties of Ba2XIO6 (X = Li, K) double perovskites alloys

This work concerns the study of the physical properties of Ba2XIO6 (X = Li, K) double perovskites alloys using first principles approach since the density functional theory implemented in Wien2k code. The exchange–correlation potential is treated by WC-GGA and mbJ-GGA. The negative formation enthalpy of both alloys confirms the dynamic stability. Further, the elastic constants reveal that these compounds are mechanically stable and can be synthesized experimentally. The bulk, shear moduli, Young, Poisson’s ratio, anisotropic factor, and Vickers hardness values for these materials are determined using the results of the elastic constants. The Young’s modulus 3D representation showed that the Ba2KIO6 material displays a strong anisotropy compared to Ba2LiIO6. Furthermore, the analysis of electronic band structures and the density of states reveal a semiconducting nature with direct band gaps of 2.340 eV, 4.213 eV 2.350 eV and 4.027 eV for Ba2LiIO6 and Ba2KIO6, respectively, using WC-GGA and TB-mBj-GGA. Moreover, optical functions: absorption, refractive index, reflectivity and loss function are obtained.

Magnetocrystalline anisotropy energy of AYbO3 (A= Sr, Ba and Ca) perovskite oxides

First-principles calculations and Monte Carlo simulations were employed to explore the effect of magnetic anisotropy on magnetocaloric properties and the magnetocrystalline anisotropy energy (MAE) of AYbO3 (A = Sr, Ba and Ca) perovskite oxides. The equilibrium lattice constant a0 is calculated AYbO3 (A = Sr, Ba and Ca). The elastic constants and related mechanical quantities such as bulk modulus B, Zener anisotropy factor A and Cauchy pressure Cp were calculated. CaYbO3 and SrYbO3 exhibit the half-metallic characteristic. While BaYbO3 exhibits semiconductor character. Sr, Ba and Ca atoms located in the A site affected the values of magnetocrystalline anisotropy energy (MAE) so changing the sign of the magnetic anisotropy constant in SrYbO3. The magnetic anisotropy shows that the easy axis is along the axis [100] for SrYbO3, CaYbO3 and BaYbO3 respectively. The critical temperature around Tc = 65 K using the MCS method. The isothermal magnetic entropy change was calculated for BaYbO3 under different magnetic fields and magnetic anisotropy. The highest isothermal entropy change obtained at H = 5T and D = 0 is 5.51 J/kg.K. While it’s equal to 8.10 J/kg.T at H = 5T and D =5.

Anisotropy and lateral compressive strength of large-size cement-stabilized macadam for bulging deformation resistance: A numerical analysis

Large-size cement-stabilized macadam (LCSM) base effectively hinders bulging deformation in asphalt pavements. Under vibratory compaction, the embedded skeleton structure and anisotropy of large-size aggregates (LSA) impact the mechanical properties of LCSM mixes. To reveal the mesostructure and anisotropy of LSA and determine the optimal volume percentage of LSA in LCSM mixes against bulging deformation, this study first characterized the bulging deformation resistance of LCSM mixes using lateral compressive strength (LCS). Next, the evolution of coordination number (CN) and distributions of contact force and contact normal for LSAs at different volume percentages under dynamic cyclic loading were investigated using the discrete element method (DEM). In particular, the induced anisotropic behavior was explored. Then, indoor tests and numerical simulations were conducted to assess the mixes’ LCS and vertical compressive strength (VCS); additionally, the compressive damage characteristics were analyzed. The results indicate that increasing the volume percentage of LSA and dynamic cyclic loading enhanced the CN, strong contact force, and contact normal density. LSAs at varying volume percentages exhibited pronounced anisotropic characteristics before and after loading, and the anisotropy factor of the LSA dropped after loading at a volume percentage of 65 %. Furthermore, the mixes’ VCS values exceeded LCS ones at the same LSA volume percentage, and there was a consistent relationship between the LSA anisotropy and the VCS/LCS ratio, suggesting that the optimal LSA volume percentage in LCSM mixes ranged from 60 % to 65 %. Finally, as the LSA volume increased, the skeleton effect became more pronounced than the interface attenuation effect, leading to higher VCS and LCS values in the mixes, thus improving their resistance to bulging deformation.

Synthesis, Structure, and Optical Property of [6]Cyclo-1,2-naphthylene.

A one-pot procedure with cobalt-mediated oxidation of 2,2'-dilithio-1,1'-binaphthyl by ferrocenium salts afforded the chiral cyclic hexamer of naphthylene, [6]cyclo-1,2-naphthylene (1). The molecular structure of 1 was determined by single crystal X-ray crystallography and NMR analyses, revealing its cyclic structure with an approximate D3 symmetry. Compound 1 exhibits blue emission at 383 nm with high photoluminescence quantum yield of 97 %, which can be attributed to its rigid twelve-membered ring structure. Optical resolution of 1 by chiral HPLC allowed for the evaluation of its chiroptical properties. Each enantiomer exhibits circular dichroism with complex Cotton effects, which are grouped into three positive or three negative couplets. Circularly polarized luminescence is observed at 383 nm with an anisotropy factor |glum| on the order of 10-4. The high photoluminescence quantum yield and the CPL properties of 1 indicate its potential application as a CPL emitter.

Understanding the pressure effect on the physical properties of half-Heusler semiconductor LiCaX (X = As, Sb, N) compounds from Ab-initio calculations

The study delves into the structural, elastic, electronic, thermodynamic, and lattice dynamical and optic properties of LiCaX (X = As, Sb, N) ternary half-Heusler compounds under varying pressure and temperature conditions. Employing density functional theory with the generalized gradient approximation (GGA) in VASP codes, the initial steps involve optimizing the structure of the compound (cubic MgAgAs-type, space group F43m, C1b), determining elastic constants (C11, C12, and C44), and calculating elastic moduli (bulk modulus, shear modulus, Young's modulus). Other mechanical parameters such as Pugh's ratio, Poisson's ratio, and Zener anisotropy factor are also derived, providing insights into the brittle/ductile characteristics and isotropic/anisotropic behavior. The study further explores different vibrational modes in the compounds, and the effects of pressure on elastic anisotropy, vibrational, and optical properties are thoroughly investigated. Utilizing the quasi-harmonic Debye model, the research successfully reports V/Vo, bulk modulus, thermal expansion coefficient, and heat capacity at constant volume over a temperature range from 0 to 1000 K. The variation of photon energy is analyzed concerning the real and imaginary parts of the dielectric constant, refractive indices, extinction coefficient, reflectivity, and energy loss function up to 20 eV. The findings encapsulate the fundamental physical properties of all considered compounds, concluding with suggestions for potential future research avenues.

Tunable enhanced chiroptical response of a twisted L-shaped plasmon nanoparticle system

Chiroptical responses in plasmon systems have aroused widespread interest, manifesting potential application in fields including physics, biology, and pharmacy, as well as other disciplines. However, the enhancement and tunability of chiroptical responses by strong plasmon coupling, which have been seldom discussed, remain wanting. In this paper, we propose a stacked and twisted L-shaped nanoparticle system, which exhibits an enhanced chiroptical response and the dynamic modulation of chiroptical response. By adjusting the twist angle and the gap between L-shaped nanoparticles, the anisotropy factor g, which quantifies the relative strength of the chiroptical response, can reach up to −1.5, and the peak position and linewidth of the g spectrum can be modified. Furthermore, in instances where the chiroptical response is weak, we construct a finite-size 1D chain by using the proposed system as the unit cell. By harnessing the global interaction among the unit cell of the 1D chain, the maximum value of g can be effectively improved and adjusted. Such an L-shaped nanoparticle system as a fundamental structure has potential applications in tunable chiroptical devices and also extends methods for device design.

Study on the creep constitutive model of layered rockconsidering anisotropic and damage factors after hightemperature exposure

The failure of layered rock after high temperature exposure is a major concern in deep underground engineering projects. This paper proposes an improved Nishihara creep constitutive model that considers damage factors and the bedding angle, which overcomes the shortcomings of the deviation in the description of the conventional Nishihara model in the acceleration stage. The constitutive model is verified by the conventional triaxial creepiest. The theoretical curve has a high degree of fitting with the experimental curve. The experimental results show that a temperature of [Formula: see text] has an obvious influence on the steady creep rate and the creep strain of layered sandstone, and [Formula: see text] can be regarded as the temperature threshold for the long-term strength and change from anisotropic to isotropic of layered sandstone. The irreversible melting mixing phenomenon at the boundary of mineral particles with increasing temperature is the mechanism by which different treatment temperatures affect the anisotropy degree of layered rock.

The Influence of Pressure on the Electronic and Elastic Characteristics of GaP Nanocrystals using Density Functional Theory

The electronic structural and mechanical properties of III-V Gallium Phosphide (GaP) nano-crystals zinc-blende stable (ZB) phase under pressure dependence have been studied via the model of the density functional theory (DFT) in combination with the large unit cell (LUC) approach at (8, 16, 54 & 64) atoms. The exchanges and correlations (XC) energy has been defined in all approaches through generalized gradient approximations of the Perdew-Burke-Ernzerhof (GGA-PBE), and determination of GaP characteristics in the case where the pressure has been increased from 0GPa to ±50GPa. Elastic parameters like elastic constants (C11, C12 & C44), Kleinmann parameter (ξ), Zener anisotropic factor (A), shear modulus (G), Young's modulus (E), Poisson’s ratio (v), Bulk modules (B) of GaP-ZB structure have been calculated and showed systematic variation with a pressure increase. Our calculations show that Bulk modules and sound speed increase with an increase in the number of core atoms. In this systematic approach, it has been found that the B/G ratio is 1.58 for this compound and it exhibits a negative Cauchy pressure, classifying GaP as brittle. The results were discovered to be consistent with other theoretical as well as experimental results. The present study directly relates to the latest experimental works on the III-phosphide compounds. The current results provide information and direction for further investigation into the fundamentals and potential applications of gallium phosphate (GaP) nanocrystals. In addition, we attempted to compare the results of the investigation with some similar types of compounds that are already documented in the literature. We believe that our study will have a significant impact on both the field of research and contemporary technology based on semi-conducting materials.

New insights into fatigue anisotropy of an additively manufactured medium-entropy alloy: from the perspectives of crack initiation and crack propagation

ABSTRACT The present work investigates anisotropic fatigue properties of an additively manufactured (AM) medium-entropy alloy (MEA). The fatigue properties of the materials in 0°, 45° and 90° orientations with respect to the build layers were measured. In order to discover the dominant factors for stress level-dependent fatigue anisotropy, crystal plasticity finite element simulations and fatigue crack growth (FCG) experiments were used to evaluate crack initiation and crack propagation behaviours, respectively. The main conclusions are summarised as follows: First, in comparison to grain anisotropy, the difference in fatigue initiation stage is controlled by defect anisotropy. Second, the direct cause of the difference in the FCG rate is considered to be the differences in deflection angle, affected by the incompatibility of the slip planes between adjacent grains. Third, the AM-MEA displays a stress level-dependent fatigue anisotropy. At high-stress level, the fatigue life of the MEA-45° specimen is significantly higher than that of MEA-0° and MEA-90°, while at low-stress levels, the fatigue resistance of MEA-0° is similar to that of MEA-45°. Stress level-dependent fatigue anisotropy is controlled by different ratios of crack initiation and crack propagation. Our work proposes a novel research strategy that qualitatively evaluates fatigue anisotropy of AM materials.