Features Of Electronic Structure Research Articles

Features of the Conduction-Band Electronic Structure of Manganese Sulfide Solid Solutions Doped with Lanthanides

Features of the Conduction-Band Electronic Structure of Manganese Sulfide Solid Solutions Doped with Lanthanides

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.

Exploring the novel aryltellurium(IV) complexes: Synthesis, characterization, antioxidant, antimicrobial, antimalarial, theoretical and ADMET studies

The current research study is focused on biological efficacy of newly synthesized Schiff base ligand 1,1′-(ethane-1,2-diylbis(azanylylidene))bis(methanylylidene))bis(naphthalen-2-ol) (HNED) and its aryltellurium(IV) complexes. The synthesized compounds were comprehensively characterized by physical and spectral investigations such asmolar conductance, Powder-XRD, EDAX, elemental, TGA-DTG analysis, mass, FT-IR, UV–Vis, 13C NMR and 1H NMR spectroscopy. The molecular and electronic structural characteristics of the synthesized compounds were explored by theoretical chemical estimations which was based on density functional theory (DFT). The outcome of the spectroscopic and theoretical data revealed that the Schiff base HNED was coordinated with tellurium ion through oxygen and nitrogen atoms, suggesting distorted octahedral geometry of complexes. The compounds displayed mild to strong antimicrobial activity against numerous microbial species, with the growth inhibitory activities of the complexes being greater than those of the Schiff base. Complexes 6c and 6f exhibited the highest scavenging ability. Complex 6a exhibited the highest efficiency in inhibiting malarial malformation. In silico molecular docking was executed to explore the binding interaction and binding energies of compound against the active site of the various receptors (3MZF, 4DXD, 3Q70 and 2GHU). The ADMET results indicated that the synthesized compounds have favorable drug-like behavior. This study suggest that the complexes may act as promising candidates for infection ailments.

Irida-graphyne: A promising material for optoelectronic applications

Irida-graphyne (IGY), a sheet composed of carbon atoms with sp and sp2 hybridization, is offered and compared to irida-graphene (IG). The electronic structure and optical characteristic of IGY are investigated by density functional theory. The thermal and dynamic stabilities of IGY are confirmed by cohesive energy, ab initio molecular dynamics simulation, and phonon dispersion. The results indicated that IGY is metal and exhibits strong anisotropy photoresponse as well as IG to incident light with parallel and perpendicular polarizations. The high dielectric constants and optical absorption are obtained. As a result, these sheets can be used in energy storage systems, and display broad absorption spectra from infrared to ultraviolet region. The reflection and transmission constates indicated that IG and IGY are transparent, particularly in the high-energy region. Hence, the electronic and optical properties of IG and IGY support the idea that they could be used in next-generation optoelectronic devices.

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.

Prediction of free radical reactions toward organic pollutants with easily accessible molecular descriptors

Machine learning (ML) is becoming an efficient tool for predicting the fate of aquatic contaminants owing to the preponderance of big data. However, whether ML can “learn” the differences in reactivity among different free radicals has not yet been tested. In this work, the effectiveness of combining ML algorithms with molecular fingerprints to predict the reactivity of three free radicals was evaluated. First, a dataset containing 211 organic pollutants and their respective rate constants with the carbonate radical (CO3•−) was used to develop predictive models using both linear regression and ML methods. The use of topological atomic alignment information, in the form of the molecular access system (MACCS) and Morgan Fingerprint, and the electronic structure features (energy levels of the lowest unoccupied and highest occupied molecular orbitals, ELUMO and EHOMO, and the energy gap between ELUMO and EHOMO) gave satisfactory predictive performances (ML model with Random Forest algorithm with MACCS: RMSEtest = 0.787; linear regression model with energy levels: RMSEtest = 0.641). Additionally, the model interpretation correctly described that the key reactivity features for CO3•− were relatively close to those for SO4•− rather than those for •OH. These results suggest that combination of ML algorithms with easily accessible molecular fingerprints would be a powerful tool to accurately predict the radical reactions towards organic compounds.

The Magnetocaloric Effect in La(Fe,Mn,Si)<sub>13</sub>H<sub><i>x</i></sub> Based Composites: Experiment and Theory

Abstract—Samples of composites with different porosity and surface roughness based on LaFe11.4Mn0.3Si1.3H1.6 (LFMSH) alloy powders were obtained, their magnetocaloric properties were studied by a direct method in cyclic magnetic fields μ0H = 1.2 T at a frequency of 2 Hz. The maximum value of the adiabatic temperature change in pure LFMSH powder was ΔT = 3 K at Т0 = 287 K in the sample cooling mode; for composite samples, this value turned out to be approximately 2 times lower than in the powder. The effect of Mn and H atoms on the electronic structure and local magnetic characteristics of the initial La(Fe,Si)13 alloy has been studied by the methods of the electron density functional theory. Replacing some of the Fe atoms with Mn reduces the total magnetic moment and slightly lowers the Curie temperature. Hydrogenation, on the contrary, leads to an increase in exchange interactions between Fe atoms located at the vertices of the icosahedron and an increase in the Curie temperature.

Converting the Bulk Transition Metal Dichalcogenides Crystal into Stacked Monolayers via Ethylenediamine Intercalation.

We report the synthesis of ethylenediamine-intercalated NbSe2 and Li-ethylenediamine-intercalated MoSe2 single crystals with increased interlayer distances and their electronic structures measured by means of angle-resolved photoemission spectroscopy (ARPES). X-ray diffraction patterns and transmission electron microscopy images confirm the successful intercalation and an increase in the interlayer distance. ARPES measurement reveals that intercalated NbSe2 shows an electronic structure almost identical to that of monolayer NbSe2. Intercalated MoSe2 also returns the characteristic feature of the monolayer electronic structure, a direct band gap, which generates sizable photoluminescence even in the bulk form. Our results demonstrate that the properties and phenomena of the monolayer transition metal dichalcogenides can be achieved with large-scale bulk samples by blocking the interlayer interaction through intercalation.

Vortex-core spectroscopy of [formula omitted]-wave cuprate high-temperature superconductors

The mechanism of high-temperature superconductivity remains one of the great challenges of contemporary physics. Here, we review efforts to image the vortex lattice in copper oxide-based high-temperature superconductors and to measure the characteristic electronic structure of the vortex core of a d-wave superconductor using scanning tunneling spectroscopy.

Quantum transport simulations of sub-5 nm bilayer Ga2O3 transistor for high-performance applications

Two-dimensional (2D) semiconductors with bizarre properties show great application potential for nanoscale devices, which is regarded as the Si alternation to extend the Moore’s Law in sub-5 nm era. In this study, we investigate the electronic structure and ballistic transport characteristics of sub-5 nm bilayer (BL) Ga2O3 metal-oxide-semiconductor field-effect transistor (MOSFET) using the first-principles calculations and the nonequilibrium Green’s function method. Quasi-direct band structure with bandgap of 4.77 eV is observed in BL Ga2O3, and high electron mobility of 910 cm2 V−1s−1 at 300 K is observed under the full-phonon scattered processes. Due to the enlarged natural length, the gate-controllable ability of 2D Ga2O3 n-MOSFET is suppressed with the increased layer. The transport characteristic investigation indicates that BL Ga2O3 n-MOSFETs can meet the latest International Technology Roadmap for Semiconductors requirement for high-performance application until L g = 4 nm. The figures of merits including on-current, intrinsic delay time, and power delay product are showing competitive potential with the reported 2D materials. With the help of underlap structure, the device performance can be further improved in the sub-3 nm region. Our results indicate that BL Ga2O3 is a promising candidate for sub-5 nm MOSFET applications.

A promising optoelectronic and thermoelectric response of full Heusler Na2TlX (X = Bi, Sb) alloys: a DFT approach

The energy conversion efficiency is one of the attributes that make Heusler alloys an extraordinary candidate for thermoelectric applications. In this paper, we have examined the electronic structure, elastic, optical and transport characteristics of full Heusler Na2TlX (X = Bi, Sb) alloys using DFT. The electronic properties are analyzed by utilizing modified Becke Johnson (mBJ) potential. The negative formation energies and optimization results reveal the stable phases of both alloys. The electronic properties exposed the semiconductor nature of both alloys. The elastic stability is obtained from various elastic parameters. The optical response of these alloys has been studied in depth by evaluating the real and imaginary dielectric functions, optical loss, refractive index and absorption coefficient. Furthermore, the thermoelectric properties are computed, which demonstrate the high electrical conductivity, Seebeck and ZT values for both alloys. The above computed attributes favor the use of studied alloys in green energy and optoelectronic applications.

Bifunctional CoxP-FeP@C for overall water splitting realized by manipulating the electronic states of Co via phosphorization

The electronic properties and structural characteristics of transition metal materials have a significant impact on their electrocatalytic performance. Therefore, precisely controlling the electronic states of core metals and fabricating catalysts with advanced structures are conducive to facilitating electrolysis process. Herein, we manipulate the electronic properties of the electroactive sites of catalysts by controlling the degree of phosphorization during the phosphorization process. The CoxP-FeP@C electrocatalysts, characterized by their sea-urchin morphology, were synthesized by subjecting CoFc-metal organic framework (MOF) precursors to phosphorization for specific time intervals. The optimized Co2P-FeP@C-5 electrocatalyst showed the optimum performance towards the oxygen evolution reaction (OER) catalytic efficiency with 239 mV overpotential and the hydrogen evolution reaction (HER) activity with 169 mV overpotential to reach 10 mA·cm−2 in 1.0 M KOH (PH = 13.8).For comparison, the extended duration of phosphorization resulted in the formation of CoP-FeP@C-15 and CoP-FeP@C-30 electrocatalysts, which exhibited compromised electrocatalytic performance due to the transformation of the electroactive core Co2P to CoP during subsequent phosphorization processes.The improved interfacial properties between Co2P and FeP play a crucial role in enhancing the efficiency of water decomposition, attributed to the higher density of states (DOS) at the Fermi Level and the increased availability of electroactive sites for the adsorption of intermediates and electrolysis. These findings are substantiated by density functional theory (DFT) calculations. This approach offers a highly effective means of manipulating the electronic properties of the electroactive transition metal core by controlling the degree of phosphorization, with the ultimate goal of achieving efficient water splitting.

Study on the Electronic Structure and Electrical Transmission Characteristics of Low-dimensional h-BCN Nanomaterials

Study on the Electronic Structure and Electrical Transmission Characteristics of Low-dimensional h-BCN Nanomaterials

Synthesis of Flower‐Like FeS2 and NiS2 Microspheres Based on Nanoflakes and Nanoparticles: Electronic Structures, Magnetic and Optical Properties

Flower‐like spherical micrometer‐sized particles of FeS2 and NiS2 are synthesized using the solvothermal method. The microstructure, phase composition, saturation magnetization and optical characteristics of the synthesized FeS2 and NiS2 are described, and the atomic structure, electronic structure, and optical characteristics of the materials are calculated systematically founded upon the first principles of density functional theory. This work shows that the magnetic saturation intensity of FeS2 and NiS2 is respectively 0.36 and 0.02 emu g−1. The FeS2 and NiS2 bandgaps are separately 0.81 and 2.07 eV, calculated by Tauc's relation. Through the comparison of optical properties, the maximum absorption coefficient of FeS2 and NiS2 is separately 3.26 × 105 and 3.3 × 105 cm−1, and the two crystals’ absorption coefficient accordingly drops to 0 at 23.8 and 25.8 eV, indicating that the maximum absorption value and energy absorption range of NiS2 are higher than those of FeS2. The reflectivity above 60% ranges from 15.3 to 20.6 eV and 15.2 to 21.5 eV for FeS2 and NiS2, respectively, which indicates that the reflectivity of NiS2 is stronger than that of FeS2.

First-principles study of controllable contact types in Janus MoSH/GaN van der Waals heterostructure.

The search for contact materials with low contact resistance and tunable Schottky barrier (SB) height of two-dimensional (2D) materials is important for improving the electronic performance. Inspired by the recently synthesized metallic Janus MoSH, this study employs first-principles calculations to investigate the electronic structure, mechanical properties, and interface characteristics of Janus MoSH/GaN and MoHS/GaN van der Waals (vdW) heterostructures. We find that both heterostructures exhibit isotropic mechanical properties and form p-type Schottky barrier contacts (p-ShC) and the SB height of MoHS/GaN is smaller than that of the MoSH/GaN heterostructure. The variation in SB height and contact type under biaxial strain and electric field is also studied for both vdW heterostructures, respectively. Compared to the MoSH/GaN heterostructure, the MoHS/GaN heterostructure can transition to Ohmic contact (OhC) under biaxial strain and electric field, making the S-face contact of MoSH with GaN a more effective contact approach. These findings could provide a new pathway for the design of controllable Schottky nanodevices and high-performance electronic devices on GaN-based vdW heterostructures.

Tailoring the structure, mechanical, electronic, and thermodynamic properties of Al8Mn5 by doping Ti atom with different atomic site configurations

To solve the problem of the influence of Ti particles on Al8Mn5 phases is difficult to observe from the experiments, the effects of Al8Mn5 doped with Ti atom at different Wyckoff sites on its thermodynamic properties, mechanical properties, and electronic structural characteristics were systemically studied by first-principles calculations in this work. It was found that the doping of Ti can enhance the thermodynamic, dynamic, and mechanical stability, change the elastic anisotropy in different directions, and decrease the ductility of Al8Mn5. The calculated mechanical results showed that the bulk modulus decreased, while the Young's modulus (E), hardness (HV), and shear modulus improved for the Ti-doped Al8Mn5 phases. The Al–Ti5 phase in Ti doping Al sites and the Mn–Ti3 phase in Ti doping Mn sites have the largest E with the values of 234.59 and 233.25 GPa, respectively. Additionally, the Al–Ti5 and the Mn–Ti3 phases have the highest HV of 16.24 and 16.06 GPa in Chen's model, and 14.31 and 14.48 GPa in Tian's model, respectively. The electronic structures and chemical bonding characteristic information elaborated that the improvement in mechanical properties is due to the improvement in Al–Mn and Al–Al bond strength.

Unraveling Metal-Ligand Bonding in an HNO-Evolving {FeNO}6 Complex with a Combined X-ray Spectroscopic Approach.

Photolytic delivery of nitric oxide and nitroxide has substantial biomedical and phototherapeutic applications. Here, we utilized hard X-ray spectroscopic methods to identify key geometric and electronic structural features of two photolabile {FeNO}6 complexes where the compounds differ in the presence of a pendant thiol in [Fe(NO)(TMSPS2)(TMSPS2H)] and thioether in [Fe(NO)(TMSPS2)(TMSPS2CH3)] with the former complex being the only transition metal system to photolytically generate HNO. Fe Kβ XES identifies the photoreactant systems as essentially Fe(II)-NO+, while valence-to-core XES extracts a NO oxidation state of +0.5. Finally, the pre-edge of the Fe high-energy-resolution fluorescence detected (HERFD) XAS spectra is shown to be acutely sensitive to perturbation of the Fe-NO covalency enhanced by the 3d-4p orbital mixing dipole intensity contribution. Collectively, this X-ray spectroscopic approach enables future time-resolved insights in these systems and extensions to other challenging redox noninnocent {FeNO}x systems.

Dual Lewis Acid-Base Sites Regulate Silver-Copper Bimetallic Oxide Nanowires for Highly Selective Photoreduction of Carbon Dioxide to Methane.

Highly selective photoreduction of CO2 to valuable hydrocarbons is of great importance to achieving a carbon-neutral society. Precisely manipulating the formation of the Metal1 ⋅⋅⋅C=O⋅⋅⋅Metal2 (M1 ⋅⋅⋅C=O⋅⋅⋅M2 ) intermediate on the photocatalyst interface is the most critical step for regulating selectivity, while still a significant challenge. Herein, inspired by the polar electronic structure feature of CO2 molecule, we propose a strategy whereby the Lewis acid-base dual sites confined in a bimetallic catalyst surface are conducive to forming a M1 ⋅⋅⋅C=O⋅⋅⋅M2 intermediate precisely, which can promote selectivity to hydrocarbon formation. Employing the Ag2 Cu2 O3 nanowires with abundant Cu⋅⋅⋅Ag Lewis acid-base dual sites on the preferred exposed {110} surface as a model catalyst, 100 % selectivity toward photoreduction of CO2 into CH4 has been achieved. Subsequent surface-quenching experiments and density functional theory (DFT) calculations verify that the Cu⋅⋅⋅Ag Lewis acid-base dual sites do play a vital role in regulating the M1 ⋅⋅⋅C=O⋅⋅⋅M2 intermediate formation that is considered to be prone to convert CO2 into hydrocarbons. This study reports a highly selective CO2 photocatalyst, which was designed on the basis of a newly proposed theory for precise regulation of reaction intermediates. Our findings will stimulate further research on dual-site catalyst design for CO2 reduction to hydrocarbons.

Dual Lewis Acid‐Base Sites Regulate Silver‐Copper Bimetallic Oxide Nanowires for Highly Selective Photoreduction of Carbon Dioxide to Methane

AbstractHighly selective photoreduction of CO2 to valuable hydrocarbons is of great importance to achieving a carbon‐neutral society. Precisely manipulating the formation of the Metal1⋅⋅⋅C=O⋅⋅⋅Metal2 (M1⋅⋅⋅C=O⋅⋅⋅M2) intermediate on the photocatalyst interface is the most critical step for regulating selectivity, while still a significant challenge. Herein, inspired by the polar electronic structure feature of CO2 molecule, we propose a strategy whereby the Lewis acid‐base dual sites confined in a bimetallic catalyst surface are conducive to forming a M1⋅⋅⋅C=O⋅⋅⋅M2 intermediate precisely, which can promote selectivity to hydrocarbon formation. Employing the Ag2Cu2O3 nanowires with abundant Cu⋅⋅⋅Ag Lewis acid‐base dual sites on the preferred exposed {110} surface as a model catalyst, 100 % selectivity toward photoreduction of CO2 into CH4 has been achieved. Subsequent surface‐quenching experiments and density functional theory (DFT) calculations verify that the Cu⋅⋅⋅Ag Lewis acid‐base dual sites do play a vital role in regulating the M1⋅⋅⋅C=O⋅⋅⋅M2 intermediate formation that is considered to be prone to convert CO2 into hydrocarbons. This study reports a highly selective CO2 photocatalyst, which was designed on the basis of a newly proposed theory for precise regulation of reaction intermediates. Our findings will stimulate further research on dual‐site catalyst design for CO2 reduction to hydrocarbons.

Recent Advances and Opportunities of Eco-Friendly Ternary Copper Halides: A New Superstar in Optoelectronic Applications.

Recently, the newly-emerging lead-free metal-halide materials with less toxicity and superior optoelectronic properties have received wide attention as the safer and potentially more robust alternatives to lead-based perovskite counterparts. Among them, ternary copper halides (TCHs) have become a vital group due to their unique features, including abundant structural diversity, ease of synthesis, unprecedented optoelectronic properties, high abundance, and low cost. Although the recent efforts in this field have made certain progresses, some scientific and technological issues still remain unresolved. Herein, a comprehensive and up-to-date overview of recent progress on the fundamental characteristics of TCH materials and their versatile applications is presented, which contains topics such as: i) crystal and electronic structure features and synthesis strategies; ii) mechanisms of self-trapped excitons, luminescence regulation, and environmental stability; and iii) their burgeoning optoelectronic devices of phosphor-converted white light-emitting diodes (WLEDs), electroluminescent LEDs, anti-counterfeiting, X-ray scintillators, photodetectors, sensors, and memristors. Finally, the current challenges together with future perspectives on the development of TCH materials and applications are also critically described, which is considered to be critical for accelerating the commercialization of these rapidly evolving technologies.