Bands In Region Research Articles

Serration-induced plasticity in phase transformative stainless steel 316L upon ultracold deformation at 4.2 K

Eras of hydrogen economy and aerospace have reignited interest in long-used austenitic stainless steel series owing to cost-effective and desirable mechanical properties for cryogenic applications. However, their mechanical response at liquid helium temperature (4.2 K), a critical temperature for liquid hydrogen and aerospace applications, is still arguable, and the associated underlying deformation mechanisms upon such ultracold deformation remain elusive. Here, we investigate the microstructural evolution of stainless steel 316L during ultracold tensile deformation at 4.2 K, showcasing microstructures about how tensile properties conducted at 4.2 K are distinguishable compared to the widely known ones at 77 K and about what deformation mechanism at 4.2 K prevails. We make clear that ultracold tensile deformation of stainless steel 316L enables a large ductility, increasing from 52 % at 77 K to 60 % at 4.2 K, even a drop of loading temperature from 77 K to 4.2 K, and even severe discontinuous plastic serration flow in the strain-stress curves at 4.2 K. Microstructural analysis of 4.2 K-ultracold deformation structure elucidates that simultaneous enhancement in strength and ductility is the consequence of both effects, i.e., the first-order solid-state transformation hardening effect by phase transformation of austenite to highly dislocated ά-martensite microstructure in the earlier plastic strain regime, followed by twinning-induced plasticity effect within the deformation-induced ά-martensitic body-centered cubic (BCC) grains in the later stages of deformation. The advent of deformation twin boundaries in ά-martensite grains acts as robust impediments to dislocation accumulation, resulting in substantial work hardening. Further, our high-resolution transmission electron microscopy analysis, taken from the regions of stress-induced adiabatic shear bands, reveals two significant features: (i) the intersection of plentiful coherent twins imposes atomic-scale stacking faults, nano-incoherent twins, and disconnections into BCC ά-martensite; (ii) at these localized temperature-rise regions, the ordered domain is often observed in the BCC martensite. Our findings can provide both a new paradigm of serration impact on mechanical properties and the origin of serrated yielding in the plastic strain regime at 4.2 K, guiding the twinning-utilized alloy design conformable for ultracold applications.

Ti1-xAlxN or TiN + AlN: An investigation about Al influence on titanium aluminum nitride thin films structural organization

Ti1-xAlxN thin films with different Al contents (Ti0.8Al0.2N, Ti0.6Al0.4N and Ti0.4Al0.6N) were deposited by reactive magnetron sputtering in order to determine the real structure formed in these coatings: a single ternary nitride, with a substitutional solid solution formation, or the presence of two binary nitrides, TiN + AlN. The elementary composition, morphology homogeneity, chemical elements distribution, crystalline structure, grain size evaluation, modification on coatings structure and formed compounds were determined. GAXRD analyses evinced a grain size growth for all Ti1-xAlxN samples, suggesting that aluminum atoms are not present as a single AlN phase, but as a ternary nitride. In XPS analyses, N 1s spectrum for all samples exhibited a shift toward lower binding energies in Ti-N component, attesting the Ti-Al-N bond presence. Moreover, signatures of Al 3p and Ti 3d band shift were detected in the valence band region, confirming the Ti1-xAlxN solid solution formation for all deposited samples.

Machine-Learning-Based Depression Detection Model from Electroencephalograph (EEG) Data Obtained by Consumer-Grade EEG Device.

Background/Objectives: There have been attempts to detect depression using medical-grade electroencephalograph (EEG) data based on a machine learning approach. EEG has garnered interest as a method for assessing brainwaves by attaching electrodes to the scalp to obtain electrical activity in the brain. Recently, machine learning has been applied to the EEG data to detect depression, with encouraging results. Specifically, studies using medical-grade EEG data have shown that depression can be accurately detected. However, there is a need to expand the range of applications by achieving a score with machine learning using simpler consumer-grade brain wave sensors. At present, a sufficient score has not been achieved.; Methods: To improve the score of depression detection, we quantified various EEG indices to train models such as power spectrum, asymmetry, complexity, and functional connectivity. In addition, feature selection was performed to ensure that the model learns only promising EEG indices for depression detection. The feature selection methods were Light Gradient Boosting Machine (LightGBM) feature importance, mutual information, ReliefF and ElasticNet coefficients. The selected EEG indices were learned by the LightGBM model, which is reported to be as accurate as the latest deep learning models. In cross-validation, the independence of test and training data was ensured to avoid excessively calculated score; Results: The results showed that the Macro F1 score was 91.59%, suggesting that a consumer-grade EEG can detect depression. In addition, analysis of the EEG indices selected by feature selection indicated that the Macro F1 score was about 80% for single EEG indices such as differential entropy in the frequency band β and functional connectivity in the left frontal region in the frequency band 1-128 Hz; Conclusions: Although the data were obtained from a consumer-grade EEG, the results suggest that these EEG indices are promising for detection depression.

The electronic structure, optical, and transport properties of novel SrScCu3M4 (M = Se, Te) semiconductors

Abstract The density functional theory is used to investigate the complex relationships between the physical properties of the novel quaternary SrScCu3M4 (M = Se, Te) semiconductors. The computed negative formation energy values of these materials demonstrate their stable nature. The distribution of ELF around chalcogens and Cu atoms shows substantial localization, indicating strong covalent bonding. The phonon dispersion curves show that the materials have good structural stability with no negative frequencies. The s/p states of Se and s/p/d of Te play minor roles, while Cu-d states have a considerable influence on the valence band region. The computed energy gap values without SOC for SrScCu3Se4 and SrScCu3Te4 are 1.29, and 0.90, respectively. The predicted energy gap values with SOC for SrScCu3Se4 and SrScCu3Te4 are 1.35, and 0.87, respectively. SrScCu3Se4 is a harder and more compressible material than SrScCu3Te4, as confirmed by its higher bulk modulus. The ε 1(ω) values decrease and ultimately become negative, which suggests these materials are reflective. SrScCu3Te4 exhibits plasmon resonance at a high energy domain as compared to SrScCu3Se4, resulting in a greater loss function. The current study can establish the potential efficiency of these materials in cutting-edge optoelectronic devices.

Probing Surface-Mediated Electronic Coupling in Flat Hexagonal Phosphorus Nanostructures and Monolayer on Au(111).

Due to its diverse allotropes and intriguing properties, 2D phosphorus, also known as phosphorene, is a material of great interest. Here, the successful growth of flat hexagonal 2D phosphorus on Au(111) is reported. Starting from phosphorus linear chains at low coverage, a porous network and finally an extended 2D flat hexagonal (HexP) layer while increasing phosphorus deposition is formed. Using scanning tunneling microscopy/spectroscopy combined with ab initio calculations, the structure and electronic properties of the as-grown phosphorus structures are followed. The progressive formation of a phosphorus electronic band in the conduction band region is followed. More strikingly, a partial flatband that appears only on the HexP phase characterized by a sharp peak in the electronic spectrum is observed. These bands arise from the hybridization of phosphorus and gold atoms. This novel phosphorus-based structure exhibits remarkable electronic properties due to gold mediated phosphorus-phosphorus electronic coupling. This work paves the way for new interface material developments with attractive electronicproperties.

Enhancing motor skill learning through multiple sessions of online high-definition transcranial direct current stimulation in healthy adults: insights from EEG power spectrum.

The purpose of this study was to evaluate the influence of high-definition transcranial direct current stimulation (HD-tDCS) on finger motor skill acquisition. Thirty-one healthy adult males were randomly assigned to one of three groups: online HD-tDCS (administered during motor skill learning), offline HD-tDCS (delivered before motor skill learning), and a sham group. Participants engaged in a visual isometric pinch task for three consecutive days. Overall motor skill learning and speed-accuracy tradeoff function were used to evaluate the efficacy of tDCS. Electroencephalography was recorded and power spectral density was calculated. Both online and offline HD-tDCS total motor skill acquisition was significantly higher than the sham group (P < 0.001 and P < 0.05, respectively). Motor skill acquisition in the online group was higher than offline (P = 0.132, Cohen's d =1.46). Speed-accuracy tradeoff function in the online group was higher than both offline and sham groups in the post-test. The online group exhibited significantly lower electroencephalography activity in the frontal, fronto-central, and centro-parietal alpha band regions compared to the sham (P < 0.05). The findings suggest that HD-tDCS application can boost finger motor skill acquisition, with online HD-tDCS displaying superior facilitation. Furthermore, online HD-tDCS reduces the power of alpha rhythms during motor skill execution, enhancing information processing and skill learning efficiency.

Highly efficient Y3-xBaxAl5-xSixO12:Cr3+ near-infrared phosphor for plant growth

Near-infrared (NIR) phosphors enhance the growth of plants due to their superior penetration. However, relatively high thermal quenching and low quantum efficiency restrict the development of NIR phosphors. In this study, Y3-xBaxAl5-xSixO12:Cr3+ phosphors (YBAS:Cr3+) with varying concentrations of Ba2+-Si4+ and Cr3+ were studied. The results demonstrate high-purity phases are obtained with doping Ba2+-Si4+ and Cr3+. The Ba2+-Si4+ doping enhances crystallinity and near-spherical particles are synthesized. The theoretical calculations indicate a significant reduction in bandgap with doping Ba2+-Si4+, resulting in impurity levels appearing in the valence band region. The state density calculation shows that the band formation is contributed by all elements. The optimal Ba2+-Si4+ doping concentration is 0.05 mol and the Cr3+ doping content is 0.09 mol. The critical distance (R c ) is 16.62 Å. Dipole–dipole interactions and radiation reabsorptions are main concentration quenching mechanisms. Lattice distortions occur with the introduction of Ba2+-Si4+ and the value (D r ) is 0.052. The YBAS:0.09Cr3+ phosphor shows a crystal field strength with a Dq/B value of 2.76. The phosphor exhibits a high quantum efficiency (73.42%), superior thermal quenching resistance (∼70% initial intensity at 150°C), and a suitable fluorescence lifetime (130.04 µs). A near-infrared pc-LED with YBAS:0.09Cr3+ phosphor displays a high output power of 167.12 mW and a moderate conversion efficiency of 3.82%.

Optical Characterization of Coastal Waters with Atmospheric Correction Errors: Insights from SGLI and AERONET-OC

This study identifies the characteristics of water regions with negative normalized water-leaving radiance (nLw(λ)) values in the satellite observations of the Second-generation Global Imager (SGLI) sensor aboard the Global Change Observation Mission–Climate (GCOM-C) satellite. SGLI Level-2 data, along with atmospheric and in-water optical properties measured by the sun photometers in the AErosol RObotic NETwork-Ocean Color (AERONET-OC) from 26 sites globally, are utilized in this study. The focus is particularly on Tokyo Bay and the Ariake Sea, semi-enclosed water regions in Japan where previous research has pointed out the occurrence of negative nLw(λ) values due to atmospheric correction with SGLI. The study examines the temporal changes in atmospheric and in-water optical properties in these two regions, and identifies the characteristics of regions prone to negative nLw(λ) values due to atmospheric correction by comparing the optical properties of these regions with those of 24 other AERONET-OC sites. The time series results of nLw(λ) and the single-scattering albedo (ω(λ)) obtained by the sun photometers at the two sites in Tokyo Bay and Ariake Sea, along with SGLI nLw(λ), indicate the occurrence of negative values in SGLI nLw(λ) in blue band regions, which are mainly attributed to the inflow of absorptive aerosols. However, these negative values are not entirely explained by ω(λ) at 443 nm alone. Additionally, a comparison of in situ nLw(λ) measurements in Tokyo Bay and the Ariake Sea with nLw(λ) values obtained from 24 other AERONET-OC sites, as well as the inherent optical properties (IOPs) estimated through the Quasi-Analytical Algorithm version 5 (QAA_v5), identified five sites—Gulf of Riga, Long Island Sound, Lake Vanern, the Tokyo Bay, and Ariake Sea—as regions where negative nLw(λ) values are more likely to occur. These regions also tend to have lower nLw(λ) values at shorter wavelengths. Furthermore, relatively high light absorption by phytoplankton and colored dissolved organic matter, plus non-algal particles, was confirmed in these regions. This occurs because atmospheric correction processing excessively subtracts aerosol light scattering due to the influence of aerosol absorption, increasing the probability of the occurrence of negative nLw(λ) values. Based on the analysis of atmospheric and in-water optical measurements derived from AERONET-OC in this study, it was found that negative nLw(λ) values due to atmospheric correction are more likely to occur in water regions characterized by both the presence of absorptive aerosols in the atmosphere and high light absorption by in-water substances.

Ab-initio investigation of structural, electronic, thermoelectric and optical properties of Full-Heusler X2MnB (X = Ti, Zr) for energy harvesting applications

In this manuscript comprehensive first-principles calculations have been presented for Full-Heusler X2MnB (X = Ti, Zr) compounds. This work includes detailed observations of the structural stability, origin of the transport phenomenon, optical properties, and electronic response. Structural parameters support the previous findings by confirming structural stability in the non-magnetic phase. Ti2MnB (Zr2MnB) valence band maxima and conduction band minima have bandgaps of 0.217 (0.301) eV and 0.181 (0.209) eV for PBE-GGA (mBJ) approximations which lie between L-L symmetry points. Due to the comparative measurements of the two states, the DOS results show that the Ti1/Zr1, Ti2/Zr2 Mn eg, and t2g states mainly contribute to the valence band region for Ti2MnB and Zr2MnB alloys, confirming their ionic nature. The computation of the overall electronic parameters’ reveals semiconducting nature. Thermoelectric properties have been calculated as a function of temperature in the 100–1200 K range. The positive values of Seebeck coefficients specify p-type character of X2MnB While at 300 K, Zr2MnB and Ti2MnB showed the highest Seebeck coefficients, measuring roughly values of 268 (µK/V) and 243 (µK/V), respectively. These values suggest that the material exhibits high thermoelectric performance. Though high optical absorption coefficient and low reflectivity in the visible and ultra violet regions, confirms use of these materials in solar cell applications. These findings suggest that material holds great potential for use in thermoelectrical applications which can support in upcoming experimental considerations.

Structural graph learning method for hyperspectral band selection

ABSTRACT Recently, graph learning-based hyperspectral band selection algorithms illustrate impressive performance for hyperspectral image (HSI) processing, whose goal is to select an optimal band combination containing less redundancy through the learned graph matrix. However, most of the previous methods work in single spectral domain, which neglects the rich image spatial information. Moreover, they typically model the graph matrix from a global perspective while ignoring the differences in spatial distribution that exist in diverse pixel and band regions. Based on the above considerations, to take full account of structure information in spatial and spectral domains, a structural graph learning method for hyperspectral band selection (SGLM) is designed. Specifically, SGLM constructs two matrices using the correlation between pixels and bands under the local perspective, which can capture the image structure information reasonably. Since the proposed method is modelled in both spatial and spectral dimensions, it is conducive to subsequent band subset generation task. Meanwhile, in order to guarantee local spatial consistency among bands, a Laplacian regularization term associated with the error matrix is introduced to the self-representation model. Additionally, considering that the importance of a band is consistent with its capability to reconstruct the entire band set, an adjacent bands reconstruction strategy is adopted to obtain the ultimate band combination, which can assess the significance of each band effectively. The comprehensive experimental analysis on four datasets demonstrates that the proposed SGLM model has outstanding superiority in comparison with several band selection algorithms.

A novel dual-band defected ground structure wearable microstrip patch antenna for breast tumor detection in biomedical applications

This paper presents a dual-band, low-profile wearable antenna for detecting breast tumors in biomedical applications. The antenna is designed on the FR4 substrate with an optimized dimension of 32 × 27.5 × 0.61 mm3. The compact rectangular patch is miniaturized by cutting the rectangular slots on the front side. The partial ground structure is used for moving the resonance frequency in the ISM band region and for giving the tripping result of the return loss. A breast phantom is created between the transmitter and receiver for detecting the tumor in the phantom model. The different sizes and positions of the tumor in the breast phantom provide different values of the return loss. The final optimized design of the antenna is operated at 2.43 GHz and 3.32 GHz with −35 and −24 return losses respectively. It has been observed from the simulated and measured results that the antenna has a negligible difference between the reflected coefficient, radiation pattern and gain. Afterward, the antenna is also checked for biocompatibility, which represents its good performance. The on-body analysis of the antenna represents a minor variation in the results. The Specific Absorption Ratio (SAR) value of the antenna is in the acceptable range as defined for the wearable device. It is a promising compact wearable antenna that can be used in biomedical applications.

Reduction of the photogenerated electron transport path by modulating the conduction band region to achieve the highest lignin β–O–4 bond photocleavage efficiency under xenon excitation

Photocracking of lignin β–O–4 bonds is a green approach for the high-value modification of lignin. Graphitic carbon nitride (g-C3N4) that can photocleave the β–O–4 bond is presently the only stable, metal-free photocatalyst owing to the residual metal ions generated due to photocorrosion of metal sulfides. Herein, g-C3N4 with a N–C3 vacancy structure is prepared by etching site–engineering strategy based on the protection of C–N=C structure by chlorine atom. The N–C3 vacancy structure can reduce the transport path of the photogenerated electrons by tuning the conduction band (CB) region to the edge of the photocatalyst, which impedes the critical complexation of the photogenerated electron–hole pairs and enhances the photoelectric conversion efficiency five-fold. Combined with the unique chemisorption capacity (137.82 kJ/mol) of N–C3 vacancies for oxygen, the g-C3N4 photocatalysts with N–C3 vacancy structure can generate 9.6-fold higher superoxide radicals and 13-fold higher lignin β–O–4 bond photocleavage efficiency lignin compared with untreated g-C3N4. Based on the reaction enthalpy changes and free energies investigated through simulations, a route of lignin Cα–Cβ bonds being oxidized and dehydrogenated twice by photogenerated cavities is proposed for the first time. This work reveals the relation between the properties of g-C3N4 and the photocleavage efficiency of lignin β–O–4 bonds.

Penetrating wood foreign bodies (stob) of the coronary band in horses: 15 cases.

To retrospectively report the historical and clinical findings, diagnostics, treatment, and outcome of horses with penetrating wood foreign bodies (PWFBs) of the coronary band. 15 client-owned horses. Horses had varying degrees of lameness and soft tissue swelling of the coronary band and pastern region. A defect in the coronary band was identified, but the actual wood foreign body was not always readily visualized. Medical records of horses diagnosed with PWFBs of the coronary band between 2004 and 2023 were reviewed. Information retrieved from the medical records included history, signalment, diagnostics, treatment, and outcome. Thirteen of 15 horses that sustained a PWFB to the coronary band were participating in foxhunting. Penetrating wood foreign bodies occurred more frequently near the central axis or toe region (11/15) and more commonly in the forelimbs (11/15). Removal of PWFBs can be performed with the horse standing and sedated with regional anesthesia. Complete removal of the PWFB required partial removal of the adjacent hoof wall. Penetrating wood foreign bodies occurred in the coronary band and lodged distally in the hoof wall of horses. Foxhunting may be a risk factor for this type of injury. Penetrating wood foreign bodies occurred most commonly in the front feet, near the central axis of the coronary band. Complete removal of the PWFB required removing a section of the adjacent hoof wall. The prognosis for return to the previous level of activity following treatment was favorable.

Spectral and microstructural analysis of the effect of the Ga+ implantation on diamond: a CL-EELS study

Due to its capacity to achieve nanometre-scale machining and lithography, a focused ion beam (FIB) is an extended tool for semiconductor device fabrication and development, in particular, for diamond-based devices. However, some technological steps are still not fully optimized for its use. Indeed, ion implantation seems to affect the crystalline structure and electrical properties of diamond. For this study, a boron-doped ([B] ∼ 1017 atoms·cm−3) diamond layer grown by chemical vapour deposition was irradiated using Ga+ by FIB, with 1 nA current and 5, 20, and 30 keV of acceleration voltage. The Ga+ implanted diamond layer has been analysed through cathodoluminescence (CL) and scanning transmission electron microscopy (STEM)-related techniques. The beam penetration depth has been simulated by Monte Carlo calculations of both Ga+ (FIB) and e− (CL) beams at different energies. The comparative CL analysis of the layer as-grown and after implantation revealed peaks related to defects, such as A band, H3 centre, and defects present in the green band region. The STEM studies for the 30 keV implanted sample showed that the diamond lattice is affected by the damage, evidencing amorphisation in the layer with a sp2/sp3 ratio of 1.37, estimated by electron energy loss spectroscopy. Therefore, this study highlights the effects of the Ga+ implantation on the optical and structural characteristics of diamond, using different methods.

Ductile shear damage micromechanisms studied by correlative multiscale nanotomography and SEM/EBSD for a recrystallized aluminum alloy 2198 T8

The damage mechanisms of ductile fracture under shear loading of an aluminum alloy 2198T8R were studied using flat thin-sheet samples. One sample was loaded until 85% of the failure displacement and then unloaded, and another one was loaded up to failure. To overcome the inherent shortcomings of nanotomography concerning the investigation of flat samples, synchrotron nano-laminography was applied to the pre-loaded sample and provided structural information down to the nanometer scale, allowing ductile damage nucleation and evolution to be studied. The damage features, including flat cracks and intermetallic particle-related damage, were visualized in 3D from the highly-deformed shear band region. Using nano-laminography, no nano-voids were found. The damaged shear ligament was also observed after polishing via destructive correlative scanning electron microscope (SEM) and electron back-scatter diffraction (EBSD) which suggests that the detrimental flat cracks were both intergranular and transgranular. The flat cracks were related to highly-deformed bands. No nano-voids could be found using SEM analysis. Fractography on the second broken sample revealed that the flat cracks contained hardly observable nanometer-sized dimples. The final coalescence region was covered by sub-micrometer-sized dimples, inside which dispersoid particles were present. The fact that no nano-void was found for the pre-deformed sample implies that the nucleation, growth and coalescence of these sub-micrometer-sized voids occur at late stages of the loading history.

Possibilities of Skin Autofluorescence Reflecting the Characteristics of Diabetes Mellitus in Childhood

Objective: To measure skin autofluorescence in children and adolescents suffering from type 1 diabetes mellitus and evaluate its relationship with gender, age, experience and chronic complications of the disease. Materials and Methods: The study group included 47 children and adolescents with type 1 diabetes. Autofluorescence of the skin from the inner surface of the shoulder and nail of patients was measured using an original compact spectrofluorimeter based on the STS-VIS OCEAN OPTICS © USA microspectrometer with UVA excitation. Statistical analysis was carried out using StatsoftStatistica 12.0 software. The data is presented as a two-dimensional array. The UV LED signal was averaged and smoothed using the moving average method with a 10 nm window. Then the spectra were renormalized taking into account the found coefficients. The result of applying additional normalization is a decrease in the standard deviation. Results and Discussion: Significant differences were revealed in the skin fluorescence spectra of children of different ages. between age groups (5-7) and (8-12) is most significant in the region of the alpha band of oxyhemoglobin (540 nm) (p &lt;0.005). When using I-normalization, the NADH peak region (p &lt; 0.02) is significant with increasing disease duration. When studying the influence of gender factors on the level of skin autofluorescence, the most significant differences are found in the area of only the isosbestic points of deoxy and oxyhemoglobin 442 nm (p&lt;10-7) and 491 nm (p&lt;10-8). Significant differences in skin autofluorescence at the reference length were also obtained waves in the autofluorescence spectrum of 500 nm correspond to p&lt;10-14, depending on the presence of complications. Conclusion: In Russia, as well as throughout the world, there is an increase in the incidence of type 1 diabetes mellitus. For early diagnosis of changes in carbohydrate metabolism and complications of the disease, a simple, accessible, non-invasive research method is needed. Taking into account the results of our study, when creating non-invasive methods for monitoring the state of carbohydrate metabolism, it is necessary to take into account gender and age characteristics, experience and the presence of complications of type 1 diabetes mellitus.

Unveiling the deformation micro-mechanism for mechanical anisotropy of a CoCrFeNi medium entropy alloy

The equiatomic Cr-Co-Fe-Ni medium-entropy alloy has the face-centered cubic structure. Single crystals of this alloy were tested by in-situ micropillar compression along different loading axes under scanning electron microscope. The transmission electron microscopy characterization and molecular dynamics simulation were incorporated for quantitative analysis of the effects of different crystal orientations on the deformation mechanisms. The <001>-oriented pillar not only exhibited extensive deformation-induced nano twinning, but also has been identified for the first time to undergo the FCCHCP phase transformation at room temperature. The strain localization tendency of <011>-oriented samples was confirmed through uniaxial tests to interpret the significant serration on stress-strain curves. The prominent strain hardening of <111>-oriented pillars was attributed to intense intersection between slip planes as evidenced by the extra density of Lomer-Cottrell locks. Such a high hardening rate has caused subsequent kinking of pillars. Functional division of different regions of kink band was conducted based on Orowan model. In principle, multi-principal element alloys can theoretically be designed and developed to combine a variety of excellent properties, which is an important class of candidate structural materials for advanced engineering systems. These findings provide promising guidance for understanding the mechanical anisotropy and application of these alloys.

Insights into the optoelectronic, thermodynamic, and thermoelectric properties of novel BaYCuX3 (X = Se, Te) semiconductors from first-principles investigation

The widely used density functional theory was employed to study an intricate relationship of the optoelectronic, thermodynamic, and transport features of novel quaternary BaYCuX3 (X = Se, Te) semiconductors. The conduction band region is significantly impacted by the Ba-d and Y-d states, with negligible contributions from the S-s/p/d and Te-s/p/d states. The valence and conduction bands peak at the high symmetry Γ and Y sites, revealing an indirect energy band nature. The predicted band gaps for the BaYCuSe3 and BaYCuTe3 using the WC-GGA and TB-mBJ approximations are 0.96, 1.31 eV, and 0.54, 0.89 eV, respectively. The small atomic size of selenium in BaYCuSe3 material contributes to strong bonding, resulting in a larger energy gap as compared to BaYCuTe3. Maximum values of ε1(ω) drop as photon frequency increases, eventually approaching negative in some energy ranges. The absorption coefficient spectra shifted toward lower energy as the anion changed from Se to Te. Furthermore, the BaYCuTe3 has plasmon resonances at higher energies as compared to BaYCuSe3, resulting in increased energy loss. Furthermore, the BaYCuTe3 material exhibits maximum thermal conductivity than BaYCuSe3 across the whole temperature range.

The interplay between a pseudogap and superconductivity in a two-dimensional Hubbard model

Strongly correlated electrons systems may exhibit a variety of interesting phenomena, for instance, superconductivity and pseudogap, as is the case of cuprates and pnictides. In strongly correlated electron systems, it is considered essential to understand, not only the nature of the pseudogap, but also the relationship between superconductivity and the pseudogap. In order to address this question, in the present work, we investigated a one-band Hubbard model treated by the Green's function method within an n-pole approximation. In the strongly correlated regime, antiferromagnetic correlations give rise to nearly flat band regions in the nodal points of the quasiparticle bands. As a consequence, a pseudogap emerges at the antinodal points of the Fermi surface. The obtained results indicate that the same antiferromagnetic correlations responsible for a pseudogap, can also favor superconductivity, providing an increase in the superconducting critical temperature Tc.

First-principles study on the effect of torsional deformation on WSe2 as an anode material for calcium ion batteries.

In this paper, the effects of torsional deformation on the electronic properties of intrinsic WSe2 system and Ca-adsorbed WSe2 system were systematically studied by first-principles method. The results show that Ca can be stably adsorbed on the vacancy (H site) of WSe2 surface in all deformation systems, and the adsorption energy of the system without deformation is the highest. Intrinsic WSe2 is a semiconductor with a direct band gap of 1.53 eV. The torsional deformation makes WSe2 change from a direct band gap semiconductor to an indirect band gap semiconductor and finally to a metal property. The adsorption of Ca makes the conduction band of WSe2 move down and increases the number of peaks in the conduction band region. The new density of state peaks are mainly derived from the contribution of W-d, Se-p, and d orbitals of adsorbed atoms in each adsorption system. Mulliken charge analysis shows that Ca transfers most of the valence electrons to the substrate, and the torsional deformation changes the amount of transferred charge. The twist deformation reduces the diffusion barrier of Ca on WSe2 surface from 0.20 to 0.14 eV. The above results provide a basis for the improved application of WSe2 in ion batteries. In this study, all the first-principles calculations are based on Materials Studio 8.0 software package. The generalized gradient approximation (GGA) functional Perdew-Burke-Ernzerhof (PBE) is used for the electron exchange correlation interactions in all systems. The optimization algorithm uses Broyden-Fletcher-Goldfarb-Shanno (BFGS) to optimize the model structure and calculate the energy. The measured cutoff energy is optimized to 450 eV, and the radius of the vacuum layer in the Z-axis direction is 20 Å. The K-point of 7 × 7 × 1 is selected by Monkhorst-Pack method. The structural optimization criterion is selected, the convergence radius of the force is 0.01 eV/Å, and the displacement radius between atoms is within 0.001 Å distance. The energy convergence radius of each atom is less than 1.0 × 10-6 eV/atom.