Analysis Of Band Structure Research Articles

Expanding PyProcar for new features, maintainability, and reliability

This paper presents a comprehensive update to PyProcar, a versatile Python package for analyzing and visualizing density functional theory (DFT) calculations in materials science. The latest version introduces a modularized codebase, a centralized example data repository, and a robust testing framework, offering a more reliable, maintainable, and scalable platform. Expanded support for various DFT codes broadens its applicability across research environments. Enhanced documentation and an example gallery make the package more accessible to new and experienced users. Incorporating advanced features such as band unfolding, noncollinear calculations, and derivative calculations of band energies enriches its analytic capabilities, providing deeper insights into electronic and structural properties. The package also incorporates PyPoscar, a specialized toolkit for manipulating POSCAR files, broadening its utility in computational materials science. These advancements solidify PyProcar's position as a comprehensive and highly adaptable tool, effectively serving the evolving needs of the materials science community. New version program summaryProgram title: PyProcarCPC Library link to program files:https://doi.org/10.17632/d4rrfy3dy4.2Developer's repository link:https://github.com/romerogroup/pyprocarLicensing provisions: GPLv3Programming language: PythonSupplementary material: Pyprocar-Supplementary InformationJournal reference of previous version: Comput. Phys. Commun. 251 (2020) 107080, https://doi.org/10.1016/j.cpc.2019.107080Does the new version supersede the previous version?: YesReasons for the new version: Changes in the directory structure, the addition of new features, enhancement of the manual and user documentation, and generation of interfaces with other electronic structure packages.Summary of revisions: These updates enhance its capabilities and ensure developers' and users' maintainability, reliability, and ease of use.Nature of problem: To automate, simplify, and serialize the analysis of band structure and Fermi surface, especially for high throughput calculations.Solution method: Implement a Python library able to handle, combine, parse, extract, plot, and even repair data from density functional calculations from diverse electronic structure packages. PyProcar uses color maps on the band structures or Fermi surfaces to give a simple representation of the relevant characteristics of the electronic structure.Additional comments including restrictions and unusual features: PyProcar can produce high-quality figures of band structures and Fermi surfaces (2D and 3D), projection of atomic orbitals, atoms, and/or spin components.

Preparation and photocatalytic properties of g-C3N4/WO3–SiO2 composite photocatalyst for methylene blue and methyl orange degradation

WO3–SiO2 gel was prepared by sol-gel method using ethyl orthosilicate and sodium tungstate dihydrate as raw materials, and a series of g-C3N4/WO3–SiO2 composite photocatalysts with different g-C3N4 loading loads were prepared on WO3–SiO2 gel. The photocatalytic degradation performance of methylene blue (MB) and methyl orange (MO) was investigated under 464 nm light source. According to the findings, the degrading effect of the g-C3N4/WO3–SiO2 composite catalyst is optimum when the load of g-C3N4 is 1.3 wt%, and the degradation rates of MB and MO are 95.62 % and 98.09 %, respectively. The characterization results show that the excellent photocatalytic performance is due to the formation of g-C3N4/WO3 heterojunction by the introduction of g-C3N4, which effectively promotes the migration and separation of photogenerated carriers, increases the number of active electrons and holes, and thus enhances its photocatalytic activity. In addition, according to the analysis of the energy band structure of the catalyst, the possible mechanism of g-C3N4/WO3–SiO2 degradation of MB (MO) is proposed as S-type heterojunction mechanism.

Flexural wave rainbow trapping effect in the periodic non-uniform Euler-Bernoulli beams and its application in energy harvesting

The rainbow trapping of elastic wave enables spatial frequency shunting and energy concentration phenomenon, which implies that the broadband vibration will forbid propagating forward and occur energy concentration at different positions of metamaterial structure. This paper proposes a novel metamaterial consisting of the periodic non-uniform Euler-Bernoulli beams with an arbitrary profile section to achieve the rainbow trapping effect of flexural wave and application in piezoelectric energy harvester. Firstly, the differential quadrature method is introduced to solve a partial differential equation with variable coefficients. The convergence of this method is systematically demonstrated, and the correctness of band structures is validated by comparing theoretical results calculated by the differential quadrature method with those from the finite element method for different profiles. Based on band structures analysis, the working mechanism of the flexural wave rainbow trapping effect is attributed to the group velocity modulation; thereby, the constructed periodic array of non-uniform beams achieves integration of specific-band vibration reduction and energy enhancement at specific positions. Secondly, simulations indicate that the resonance rainbow trapping frequencies demonstrate more intense concentration of flexural wave energy compared to the counterpart with initial frequencies. Finally, the resonance rainbow trapping phenomenon demonstrates superiority in vibration energy harvesting. Specifically, when piezoelectric films are pasted on specific-position with enhanced energy density, the maximum output voltage in the independent circuit connection reaches up to 2.30V for the resonance rainbow trapping frequency of 8752Hz and the PVDF film position of x = 670 mm. Furthermore, simulations illustrate that the maximum output voltage and power are up to 4.52V and 1894.12 nW for the Series-A circuit connection, respectively, which is approximately the sum of the individual maximum output electrical energy generated by independent circuit connection at positions A and B. The proposed metamaterial beams can offer new selection guidelines for high-performance vibration energy harvesters.

Construction of S-scheme Cs3PMo12O40/MnIn2S4 heterojunction for efficient photocatalytic removal of antibiotics: Degradation pathways, toxicity evaluation and mechanism insight

Developing highly efficient photocatalysts for the removal of antibiotics and heavy metals is of vital importance but remains a great challenge. In this investigation, a novel S-scheme Cs3PMo12O40/MnIn2S4 (CPM/MIS) heterojunction with core-shell structure was fabricated successfully via hydrothermal synthesis/dissolution-precipitation approaches, which was labelled as x CPM/MIS (x = 5, 7, 9 and 11, respectively). In the composites, these 2D MIS nanoflakes were securely and uniformly affixed on the exterior of 3D CPM nanospheres, which was verified through SEM and TEM. These as-produced materials manifested enhanced photocatalytic activity towards antibiotics (tetracycline (TC) and ciprofloxacin (CIP)) degradation and Cr(VI) reduction with visible light, and the removal rates of the optimal 9 CPM/MIS for TC, CIP and Cr(VI) could reach 97.81%, 61.78% and 67.07%, respectively. Of note, these resulting CPM/MIS composites possessed excellent stability and reusability. The outstanding photocatalytic property was attributed to the synergistic effect arising from the advantageous core-shell structure and S-scheme heterostructure. This configuration strengthened robustly interfacial interaction between the constituents, which effectively enhanced light absorption in visible region, promoted the separation and transfer efficiency of photoinduced carriers, and preserved the charge carriers with heightened redox abilities. The ESR spectra and trapping tests confirmed the dominating role of holes and superoxide radical in contaminants removal. Additionally, the high-performance liquid chromatography-mass spectrometry (HPLC-MS) technique was employed to identify the photodegradation pathways of TC. And the product toxicity was evaluated using QSAR prediction. Conclusively, combining the in situ XPS data and analysis of energy band structure, a S-scheme catalytic mechanism was elucidated. This study opens new avenues for systematically designing and fabricating S-scheme heterojunction photocatalysts with outstanding catalytic property for contaminants removal.

Insights into structural, electronic, optical properties, and impedance spectroscopy of semi-doped perovskite Nd0.5Ba0.5CoO3: A theoretical and experimental study

In this study, the electronic, structural, and optical properties of semi-doped perovskite Nd0.5Ba0.5CoO3 (NBCO) were investigate using the CASTEP software, which relies on density functional theory (DFT) along with the correlation function of generalized gradient approximation (GGA) and Perdew-Burke-Ernzerhof (PBE). The mesh parameters of the (super) cell indicate that NBCO adopts an orthorhombic structure in the Pmmm space group, featuring a Coulomb Energy (EC) of approximately −244 eV. DFT and total density of states (DOS) analyses reveal that the as-prepared perovskite manifests metallic characteristics, and a notable covalent interaction is observed between the O-p and Co-d spin states, indicating strong hybridization between these orbitals. Remarkably, NBCO demonstrates 100 % spin polarization (P) at the Fermi level, with a calculated total magnetic moment of approximately 3.44 μB. Moreover, low dielectric loss (tgδ) values suggest facile electron movement, and impedance spectroscopy illustrates a dielectric relaxation phenomenon. DFT calculations predict an orthorhombic crystal structure with higher electron density at cobalt atom positions. Band structure and DOS analyses affirm metallic behavior owing to the robust hybridization between oxygen-p and cobalt-d orbitals. Optical property assessments reveal potential applications in spintronics and optoelectronics, with notable absorption in the ultraviolet–visible range. The conductivity spectra from impedance spectroscopy contribute to understanding temperature-dependent charge transport mechanisms. Dielectric constants decrease with increasing frequency and temperature, while dielectric losses remain low, indicating efficient electron movement. The material adheres to a metallic conduction mechanism as described by Drude's law, and the material's 100 % spin polarization at the Fermi level and a total magnetic moment of 3.44 μB are significant findings. Negative dielectric constants observed at specific frequencies suggest potential applications in metamaterials. Overall, the determined properties position NBCO cobaltite as a promising candidate for high-frequency devices, spintronic components, and sensors.

Unveiling the electronic structure and optical properties of two-dimensional TMDCs: first-principles study

Transition metal dichalcogenide (TMDC) materials are considered extremely efficient materials with significant applications in photovoltaics and optoelectronics. Here, the electronic structure and optoelectronic features of new transition metal-containing dichalcogenides are studied using state-of-the-art density functional theoretical calculations. For the analysis of the electronic band structures, we employed a modified Becke-Johnson potential. According to the band structure analysis, Platinum-based dichalcogenides possess an indirect band profile, having the valence band maximum and the conduction band minimum situated at discrete symmetry regions. At the same time, the zirconium-based materials have a direct type band structure at the same Γ-point. We calculated cohesive energies and formation energies to assess the stability of these materials. The substantial optical parameters such as the two parts of the dielectric constant, absorption coefficients, energy loss functions, reflectivity spectra, refractive index, real optical conductivity spectra, spectra, and the extinction coefficients, are calculated. These findings provide insight into potential applications in optoelectronic devices. The calculated band gaps and refractive index revealed an inverse relationship. This research aims to make a significant contribution to the advancement of various and possibly gainful semiconducting technologies, as well as their practical applications.

First-principles screening of structural, electronic, optical and elastic properties of Cu-based hydrides-perovskites XCuH3 (X=Ca and Sr) for hydrogen storage applications

In the present study, density functional theory is used to conduct an in-depth investigation of the physicochemical features of the perovskite XCuH3 (X = Ca and Sr). The CaCuH3 and SrCuH3, with lattice parameters of 3.66 Å and 3.77 Å, are synthesizable and thermodynamically stable, according to structural simulations. Analysis of the electronic band structure (0 eV) and density of states (DOS) shows that XCuH3 (X = Ca and Sr) perovskites exhibit metallic behaviour. For novel polycrystalline materials, the shear and Young's moduli as well as the Poisson's ratio are computed and the findings suggested that compounds with the formula XCuH3 (X = Ca and Sr) are ductile. Hydrogen storage qualities have been analyzed and it has been shown that the CaCuH3 and SrCuH3 have gravimetric hydrogen storage capacities of 2.85 wt% and 1.97 wt%, respectively. The SrCuH3 has the highest Debye temperature (θD) 344.41 K. The findings, taken as a whole, provide a practical strategy for developing innovative, potentially useful perovskite-type hydrides for hydrogen storage.

Enhanced electrical performance of InGaSnO thin-film transistors by designing a dual-active-layer structure

In this study, dual-active-layer InGaSnO (IGTO) thin-film transistors (TFTs) were designed, and their electrical properties were investigated. Consequently, compared with the single-layer IGTO (pure Ar) TFTs, the dual-layer IGTO TFTs exhibited improved electrical properties, including a high field-effect mobility of 25.1 cm2 V−1 s−1, a low threshold voltage of 0.8 V, a high on/off current ratio of 1 × 108, a small subthreshold slope of 300 mV/decade, and a low off current. Additionally, the dual-layer IGTO TFTs showed superior stability for small Vth shifts of −1.9 V and 1.8 V under gate bias stress test conditions. Band structure analysis indicated that a thin front layer of IGTO (pure Ar) can provide an appropriate carrier concentration (Ne) near the IGTO (pure Ar)/IGTO (Ar/O2) interface, whereas a thick layer of IGTO (Ar/O2) can control the channel conductance and threshold voltage of IGTO TFTs. Moreover, atomic force microscopy, X-ray photoelectron spectroscopy, and Hall effect measurement results showed that the surface roughness, oxygen vacancies, Ne, and total trap density of IGTO (Ar/O2) films and TFTs were reduced by increasing the oxygen flow rate. Over all, the high performance dual-active-layer IGTO TFTs provides insights that can contribute to developing a new generation of transparent oxide thin-film electronics.

Comparative investigation of the characterization and photoactivity of gold-decorated graphitic carbon nitride: A study aspect of various synthesis approaches

In recent decades, photocatalysis has been broadly considered one of the potential approaches for different environmental and medicinal applications. Different synthesis methods possess different benefits and drawbacks, requiring thorough comparison to optimize the usage of precursors, equipment, and photocatalysis activity of the materials. In this study, the gold-decorated graphitic carbon nitride nanocomposites (AuCN) were successfully fabricated via different methods, including hydrothermal (HT), radiation under visible light (Ir), and chemical reduction (VC). The characterization of the prepared materials was investigated, which showed an efficient exfoliation of graphitic carbon nitride (g-C3N4 − CN) sheets and uniform embedment of gold nanoparticles (AuNPs). The AuCN sample synthesized from the chemical approach (AuCN-VC) showed the strongest signals of the AuNPs content, while the material prepared from the hydrothermal method (AuCN-HT) indicated a better CN crystalline structure. Furthermore, the photoactivity of the fabricated materials was also compared with pristine CN via the analysis of band structure, elucidating an improvement in the band gap energy to 2.25, 2.59, and 2.68 eV for the hydrothermal, irradiation, and chemical approaches, respectively. According to the photocatalysis results, AuCN-VC possessed the highest photo behavior under visible illumination with the hydrogen peroxide yield production at 271.5 mM/g.h. Meanwhile, the observation in the antibacterial activity exhibited the greatest performance regarding AuCN-HT with the recorded inhibition zone diameters of 9.3 and 8.6 mm against P. aeruginosa and S. aureus, respectively, under photo-excitation. According to the aforementioned results, the synthesized AuCN composites suggest great potential in a wide range of applications in environmental remediation and renewable production.

The effect of non-metals (O, F) dopant on the electronic structure, Dirac cone, and optical characteristics of graphene sheets applicable for gas sensing

In order to gain a systematic comprehension of the impacts of low-level defects in graphene, ab-initio calculations were performed on monolayer graphene sheets to examine how oxygen and fluorine substitutional impurities affect their energetic stability, electronic and optical characteristics. The optimal configurations, structural stability, electronic band structures, spatial charge density, and optical spectra of graphene single-layer materials doped with oxygen and fluorine atoms are investigated. The fluorine-doped graphene, therefore, showed a lower formation energy than its oxygen-doped counterpart. Additionally, F-doped graphene shows a higher charge density around the fluorine atom than O-doped graphene. Based on band structure analysis, the lower conduction bands of graphene sheets shift below the Fermi state (EF) when two O or F impurities are substituted into it. With two O/F impurity atoms doped into graphene, the conduction states are farther displaced below the EF, resulting in n-type behavior. Consequently, altering graphene structure via an O/F-substituting scheme results from the disruption of the Dirac cone near EF, which has become flat along the high symmetry point (K-point) in the Brillouin zone. Furthermore, the substitution of graphene sheets via O or F impurities exhibit markedly modified optical spectra and refractive indices at low photon energies. As a result, with one or two O/F impurity elements inserted into graphene sheets, the reflectivity and optical conductivity spectra differ at the lowest electromagnetic radiation ranges. Additionally, the electron energy loss functions as well as X-ray absorption spectra of clean and doped graphene monolayers revealed spectral variations at a moderate energy span. These investigations surmise that novel chemical modifications to graphene sheets doped with light non-metallic elements (O/F) may offer the opportunity to tailor their optical characteristics in the infrared spectrum, which may be beneficial in sensor and electrocatalyst uses.

Highly Efficient Color Conversion of 3D Photonic Crystal Phosphor Films for Micro‐Light‐Emitting Diode Applications

The color conversion efficiency of phosphor films can be significantly improved by producing them in the shape of photonic crystals (PhCs). When light with photonic band‐edge wavelengths is incident on a PhCs phosphor film, the excitation photons are resonantly absorbed, enhancing the emission intensity. This study develops three‐dimensional PhC phosphor films based on self‐assembled inverse opal structures. PhC phosphors are constructed using a silk fibroin polymer and red organic fluorescent dyes (λpeak ≈ 610 nm) doped into it. The photonic structures are designed using electromagnetic wave simulations and photonic band structure analyses. The fabricated PhC phosphor films are integrated with blue micro‐light‐emitting diode (micro‐LED) chips (λpeak ≈ 452 nm), resulting in a color conversion efficiency increase of more than 1.5 times that of bulk phosphor films. Additionally, experiments are performed using various micro‐LED chips with a size of less than 100 μm. Overall, the results of this study demonstrate the potential of PhC phosphor films in future micro‐LED‐based devices and applications, including displays and communication systems.

Co+2, Ni+2, Cu+2 doped Indium oxide as visible active nano-photocatalyst: A facile solution combustion synthesis, electronic band structure analysis by DFT approach and photocatalytic decontamination of RhB and Triclopyr

The present investigations deals with the fabrication of metal ion (M = Co+2, Ni+2, and Cu+2) doped-In2O3 photocatalysts by a simple solution combustion method. All the synthesized materials were characterized for different features by various techniques including XRD, FESEM, EDX, XPS, UVDRS, and PL. Synthesized compounds were examined for the degradation of two organic pollutants; cationic dye Rhodamine B (RhB) and pesticide Triclopyr (TC). Modification with metal ions significantly improved the degradation efficiency of pure In2O3 photocatalyst and followed the trend Co+2/In2O3 > Ni+2/In2O3 > Cu+2/In2O3 > In2O3. Highest degradation efficiencies of 99.03% for RhB and 95.84 % for TC were obtained in the case of Co+2/In2O3 (1 mol %) under visible light illumination. Further, Density Functional Theory investigations show that Co+2/In2O3 is the most favorable energetically and leads to the creation of two transition states -as opposed to a single transition state in the other doped systems-, one of which is near the Fermi level and the other at around 1.5 eV above it. We believe that this exclusive property is behind the highest photocatalytic efficiency observed experimentally. Additionally, the doped nanostructures lead to higher visible light absorption and separation of light induced charge carriers. The effect of the pH and the reactive oxygen species were also examined. Besides, a probable mechanism of charge transfer and degradation of the pollutants was presented.

Physical properties of Be-based fluoroperovskite compounds XBeF3 (X = K, Rb): a first-principles study

In this study, we used the ab-initio computational tools as implemented in the CASTEP code to explore the effects of pressure on the structural, elastic, electronic, thermodynamic and optical properties of the fluoroperovskite compounds XBeF3 (X = K, Rb) based on Being. Exchange–correlation interactions were modeled using the GGA-PBEsol functional. The ground state of the title materials was characterized by calculating the optimized lattice parameter, the bulk modulus B and its pressure derivative, and the Goldsmith tolerance factor. These materials exhibit structural stability in the cubic structure even when subjected to significant pressure levels, extending up to 18 GPa. The analysis of numerical assessments of single-crystal elastic constants (Cij ), polycrystalline elastic moduli, namely shear modulus (G), Young’s modulus and Poisson’s ratio, as well as the anisotropy factor (A), highlights the mechanical stability, elastic anisotropy and ductility of considered the compounds. The thermodynamic properties of these materials were studied through the Debye quasi-harmonic model. Analysis of energy band structures and density of states spectra shows that XBeF3 (X = K, Rb) is insulating in nature, with band gaps of 7.99 and 7.26 eV, respectively. Additionally, we calculated the linear optical spectra, including dielectric function, absorption coefficient, refractive index, optical reflectivity, and energy loss function. Based on the results obtained, these materials could be used in various optoelectronic devices operating in the UV spectrum and in energy storage devices.

Double vacancies synergistically enhanced photocatalytic activity of S-Scheme VO,S-Bi2WO6/L-CoIn2S4 heterojunction for degradation of co-existing antibiotics

In this study, the VO,S-Bi2WO6/L-CoIn2S4 heterojunction photocatalysts enriched with O and S double vacancies were prepared by L-cysteine self-doping strategy for efficient degradation of antibiotics. Results of X-ray photoelectron spectroscopy and electronic paramagnetic resonance (EPR) analysis demonstrated the existence of O and S vacancies in photocatalysts. Results of band structure analysis, electron spin resonance (ESR) and free radical capture experiments indicated that charges transfer pathway of the VO,S-Bi2WO6/L-CoIn2S4 heterojunction conformed to S-scheme mechanism. Benefiting from the synergistic effects of O, S double defects, active sites of the heterojunction were increased, and separation of photogenerated carriers was promoted. The VO,S-Bi2WO6/L-CoIn2S4 heterojunction achieved degradation efficiencies of 92.7%, 83.7%, and 40.7% for tetracycline (TC), Chlortetracycline (CTC), and Levofloxacin (LEV) within 100 min, respectively, with ·O2− as the dominated reactive species contributing to antibiotics degradation. The VO,S-Bi2WO6/L-CoIn2S4 exhibited the highest kinetic constant, which was 1.73 and 1.33 times of those of the Bi2WO6 and L-CoIn2S4. Surprisingly, when TC and CTC were coexisted, the removal of TC decreased from 92.7% to 81%, while the removal of CTC increased to 88%, showing competitive effect. Possible degradation pathways of TC and CTC were proposed according to their degradation intermediates. Ecotoxicity of the main degradation intermediates were alomost lower than TC and CTC. This work provides a reference for developing efficient S-Scheme heterojunctions with dual-vacancy for efficient degradation of organic contaminants.

Tutton K2Zn(SO4)2(H2O)6 salt: Structural-vibrational properties as a function of temperature and ab initio calculations

In this work, a thorough study of Tutton K2Zn(SO4)2(H2O)6 crystal was performed. Structural, electronic, vibrational, and thermal properties were analyzed and discussed. Calculations based on the density functional theory (DFT) were performed to provide a correct assignment of vibration modes (90 active Raman and 93 active IR), and analyses of band structure and density of states. Powder X-ray diffraction (PXRD) at 300 K showed that the Tutton crystallizes in monoclinic symmetry with space group P21/a. An electronic bandgap of 4.66 eV, typical of insulating material, was estimated by band structure calculation. The thermal analysis in the 300–700 K range by coupled TG-DTA thermogram revealed two endothermal events and one exothermal. Such events were investigated by PXRD and Raman spectroscopy as a function of temperature, where three phase changes associated with dehydration and crystallization were observed. The new phase structures were determined by the Le Bail and Rietveld methods. The thermal-structural findings suggest that the K2Zn(SO4)2(H2O)6 Tutton can be considered a promising thermochemical compound for residential heat storage devices due to a low onset for the dehydration temperature (≈327 K) and a high enthalpy of dehydration (77.4 kJ/ mol H2O).

Ab initio insight into the physical properties of MgXH3 (X = Co, Cu, Ni) lead-free perovskite for hydrogen storage application.

Renewable energy systems are vital for a sustainable future, where solid-state hydrogen storage can play a crucial role. Perovskite hydride materials have attracted the scientific community for hydrogen storage applications. The current work focuses on the theoretical study using density functional theory (DFT) to evaluate the characteristics of MgXH3 (X = Co, Cu, Ni) hydrides. The structural, vibrational, electronic, mechanical, thermodynamic, and hydrogen storage properties of these hydrides were investigated. The equilibrium lattice parameters were calculated using the Birch-Murnaghan equation of state-to-energy volume curves. The elastic constants (Cij) and relevant parameters, such as Born criteria, were calculated to confirm the mechanical stability of the hydrides. The Cauchy pressure (Cp) revealed brittle or ductile behavior. The outcomes of the Pugh ratio, Poisson ratio, and anisotropy were also calculated and discussed. The absence of negative lattice vibrational frequencies in phonon dispersion confirmed the lattice's dynamic stability. The heat capacity curves of thermodynamic properties revealed that hydrides can conduct thermal energy. The metallic character and ample interatomic distances of hydrides were confirmed by the band structure and population analysis, which confirmed that hydrides can conduct electrical energy and adsorb hydrogen. The density of state (DOS) and partial DOS unveiled the role of specific atoms in the DOS of the crystal. The calculated gravimetric hydrogen storage capacity of MgCoH3, MgCuH3, and MgNiH3 hydrides was 3.64, 3.32, and 3.49wt%, respectively. Our results provide a deeper understanding of its potential for hydrogen storage applications through a detailed analysis of MgXH3 (X = Co, Cu, Ni) perovskite hydride material.

Interface engineering of heterostructured vanadium oxides for enhanced energy storage in Zinc−Ion batteries

Rechargeable aqueous Zn−ion batteries (RAZIBs) with the merits of cost effectiveness and high safety have been rejuvenated as tantalizing energy storage systems to meet the demand for grid−scale applications. Currently, the energy storage capability of the positive electrode (cathode) holds the key for the overall performance of RAZIBs. In this work, we reveal VO2, V10O24·12H2O (HVO), and VO2/HVO can be prepared via hydrothermal reaction by using different reducing agents. VO2 exhibits high capacity of 237 mAh/g at 4 A/g, while it suffers from quick capacity decay with 48 % retention after 2000 charge/discharge cycles. On the contrary, HVO demonstrates moderate capacity but meritorious cycle stability (i.e., 173 mAh/g at 4 A/g and 82 % after 2000 cycles). By integrating the merits of high−capacity VO2 and high−stability HVO, the biphasic VO2/HVO sample exhibits promising electrochemical performance with high capacity (317 and 239 mAh/g at 1 and 4 A/g, respectively) and good cycle stability (80 % after 2000 cycles). As examined by band structure analysis, the superior electrochemical performance of VO2/HVO is attributed to the presence of a heterojunction between VO2 and HVO enabling a built−in electric field to boost electron transport kinetics, leading to high attainable capacity and reliable cycle performance in RAZIBs.

Different look at S-p bonding orbital in CdS, with Zn and Se series gap investigations

The electronic characteristics of Cadmium sulfide (CdS) series Zn x Cd16−x S8Se8 and Cd16Se16−x S x are investigated. According to the calculations, barely 12% Zn (X = 2) in the form Zn2Cd14Se16 is required to maximize the gap. To properly evaluate the excited states, the generalized gradient approximation (GGA) and modified Becke-Johnson (mBJ) potentials are utilized in the computations. The parent compound CdS exhibits three distinct forms of crystal structures, with the hexagonal structure being remarkably stable under the GGA and mBJ functionals. The partial density of states around the Fermi level demonstrates that the system’s electronic characteristics are determined by the interaction of S-p and Cd-s,p states. A substantial splitting of the valence band, shown by band structure analysis, suggests a greater polarization crystal field in the hexagonal CdS structure. The stereochemical activity of the S atom stimulated the CdS compound for extremely tiny displacements of 0.0014 Å and 0.043 Å for the Cd and S atoms in the [001] direction, respectively, as well as tilting of the Cd-S-Cd link. This compound exhibits lone pair properties, with three valance electrons of the p-orbital participating in covalent bonding and S-s electrons fully occupied. Furthermore, Van Hove singularities are discovered in the electron density of states due to the Cd-d atoms that support in the analysis of optical absorption spectra. Finally, the results suggest that CdS has potential for solar cells applications due to its direct wide band gap semiconductor features,

Bandgaps of long-period polytypes of IV, IV-IV, and III-V semiconductors estimated with an Ising-type additivity model.

We apply an Ising-type model to estimate the bandgaps of the polytypes of group IV elements (C, Si, and Ge) and binary compounds of groups: IV-IV (SiC, GeC, and GeSi), and III-V (nitride, phosphide, and arsenide of B, Al, and Ga). The models use reference bandgaps of the simplest polytypes comprising 2-6 bilayers calculated with the hybrid density functional approximation, HSE06. We report four models capable of estimating bandgaps of nine polytypes containing 7 and 8 bilayers with an average error of ≲0.05eV. We apply the best model with an error of <0.04 eV to predict the bandgaps of 497 polytypes with up to 15 bilayers in the unit cell, providing a comprehensive view of the variation in the electronic structure with the degree of hexagonality of the crystal structure. Within our enumeration, we identify four rhombohedral polytypes of SiC-9R, 12R, 15R(1), and 15R(2)-and perform detailed stability and band structure analysis. Of these, 15R(1) that has not been experimentally characterized has the widest bandgap (>3.4 eV); phonon analysis and cohesive energy reveal 15R(1)-SiC to be metastable. Additionally, we model the energies of valence and conduction bands of the rhombohedral SiC phases at the high-symmetry points of the Brillouin zone and predict band structure characteristics around the Fermi level. The models presented in this study may aid in identifying polytypic phases suitable for various applications, such as the design of wide-gap materials, that are relevant to high-voltage applications. In particular, the method holds promise for forecasting electronic properties of long-period and ultra-long-period polytypes for which accurate first-principles modeling is computationally challenging.

Auger-suppression in barrier-blocking HgCdTe long-wavelength infrared detector

Throughout, both the Auger-suppression effect and barrier-blocking devices have been regarded as highly promising solutions for achieving high- operation-temperature (HOT) in long-wave infrared (LWIR) HgCdTe devices. Herein, two structural designs of pBin-type barrier-blocking LWIR HgCdTe devices were introduced and analyzed, accompanied by an extensive investigation into the Auger-suppression effect within the designed structures. It was observed that this unique structural approach has the potential to enhance the operational temperature of HgCdTe barrier-blocking devices. A strong dependency of the Auger suppression effect on the doping concentration within the absorption region was revealed through the analysis of absorption region structural parameters. Furthermore, the analysis of band structures for different design configurations demonstrated that the structural design involving p-type barrier layers can effectively position the barrier at the conduction band, eliminating the reliance on valence band-offset with respect to barrier layer structural parameters. Consequently, the structural design and fabrication processes of the devices were significantly simplified. These discoveries offer theoretical guidance for the simplification of structural design and fabrication processes in HOT barrier-blocking HgCdTe devices, emphasizing the potential of pBin-type structures in enhancing device performance and achieving elevated operational temperatures.