Electronic Properties Research Articles

First principles calculations of electronic, vibrational, and thermodynamic properties of 3,6-dinitro-1,2,4,5-tetrazine biguanide.

G2(DTNT) as a newly reported nitrogen rich salt energetic material with good stability and detonation performance due to the hydrogen bonding crosslinking between DTNT anions and guanidine cations, demonstrating promising application prospects. This work investigates the electronic structure, vibrational characteristics and thermodynamic properties of G2(DTNT) based on first principles. Calculated lattice parameters have good consistency with the values reported in the literature, with an error of no more than 1.42%. The electronic structure of G2(DTNT) was studied based on band structure and density of states calculations. Vibration characteristics of G2(DTNT) were studied in detail through infrared and Raman spectroscopy, and each peak was assigned to different vibration modes. Phonon scattering curve indicates that G2(DTNT) is dynamically stable. In addition, we also calculated the thermal parameters and elastic constants of G2(DTNT), and found that it exhibits good thermal and mechanical stability. G2(DTNT) has strong deformation resistance along the b and c axes, and the strongest shear strain resistance along the a axis, mainly manifested as toughness. This study reports a first principles computational method based on DFT for investigating the crystal structure of G2(DTNT). Using PBE-GGA and Grimme dispersion correction with DFT-D method to handle exchange related potentials and van der Waals interactions, and OTFG Ultrasoft pseudopotential to describe electron ion interactions. The k-point grid of the Brillouin zone (BZ) is set to 4 × 1 × 1, with a minimum spacing of 0.07Å-1, and the force acting on each atom is less than 0.01eV/Å. Convergence criterion for energy difference is 5.0 × 10-7eV/atom, with a cut-off energy of 830eV. The maximum bulk stress and displacement amplitudes are 0.02 GPa and 5.0 × 10-4Å, respectively.

ErMn6Sn6: A Promising Kagome Antiferromagnetic Candidate for Room‐Temperature Nernst Effect‐Based Thermoelectrics

AbstractThe Nernst effect, the generation of a tranverse electric voltage in the presence of longitudinal thermal gradient, has garnered significant attention in the realm of magnetic topological materials due to its superior potential for thermoelectric applications. In this work, the electronic and thermoelectric transport properties of a Kagome magnet ErMn6Sn6 are investigated, a compound showing an incommensurate antiferromagnetic phase followed by a ferrimagnetic phase transition upon cooling. It is shown that in the antiferromagnetic phase ErMn6Sn6 exhibits both topological Nernst effect and anomalous Nernst effect, analogous to the electric Hall effects, with the Nernst coefficient reaching 1.71 µV K⁻¹ at 300 K and 3 T. This value surpasses that of most of previously reported state‐of‐the‐art canted antiferromagnetic materials and is comparable to recently reported other members of RMn6Sn6 (R = rare‐earth, Y, Lu, Sc) compounds, which makes ErMn6Sn6 a promising candidate for advancing the development of Nernst effect‐based thermoelectric devices.

Biaxial strain engineering of the band structure in atomically thin InSe

InSe emerges as an attractive two-dimensional semiconductor with potential applications in the near-infrared spectral range, featuring strongly layer-dependent direct bandgaps, prominent P-band emission, and high carrier mobilities. Owing to the superior mechanical flexibility of InSe, strain has been proposed as an effective way to modulate its electronic and optical properties. Here, we engineer the band structure of few-layer and bulk InSe with the thickness down to trilayers by biaxial compressive strain, enabled through thermal contraction of the substrate. We observe a significant bandgap tunability, with the blueshift rate of the bandgap transition (A transition) in the photoluminescence spectra as large as ∼200 meV per percent strain, almost twice of that obtained in the case of uniaxial straining. The biaxial strain effects show no signs of obvious layer dependence for InSe from trilayers to bulk. Moreover, we are surprised to find that the B transition with a deeper valence band involved is more sensitive to temperature than the A transition. Our results pave the way for atomically thin InSe in the applications of strain tunable optoelectronic devices and sensitive strain sensors.

Effect of side group on the mechanically induced conductance switching in 4, 4′-dipyridyl-based single-molecule junctions

Abstract The forming processes of 4, 4′-dipyridyl-based single-molecule junctions and mechanically induced conductance switching as well as the side-group effects are systematically investigated by applying the ab initio-based adiabatic geometric optimization method and the one-dimension transmission combined with three-dimension correction approximation (OTCTCA) method. The numerical results show that for the 4, 4′-dipyridyl with a π-conjugated phenyl-phosphoryl or diphenylsilyl side group, the pyridyl vertically anchors on the second atomic layer of the pyramid-shaped Au tip electrode at small inter-electrode distances by laterally pushing the apical Au atom aside, which induces stronger pyridyl-electrode coupling and high-conductance state of the formed junctions. As the inter-electrode distance increases, the pyridyl shifts to the apical Au atom of the tip electrode. This apical Au atom introduces additional scatterings to the tunneling electrons and significantly decreases the conductance of the junctions. Furthermore, for the 4, 4′-dipyridyl with a phenyl-phosphoryl side group, the probability of manifesting the high-conductance state is decreased due to the oxygen atom reducing the probability of the pyridyl adsorbing on the second layer of Au tip electrode. In contrast, for the 4, 4′-dipyridyl with a non-conjugated cyclohexyl-phosphoryl side group, the steric hindrance from the bulky cyclohexyl group leads the molecule to preferentially form the O-Au contact, which prevents both the high conductance and mechanically induced conductance switching of the junction. Our results provide a theoretical understanding of the side-group effects on electronic transport properties of single-molecule junctions, offering an alternative explanation for the experimental observations.

Reverse Regioselective Dicarbofunctionalization via Anti‐Michael‐Type Addition

AbstractVicinal dicarbofunctionalization of α,β‐unsaturated carbonyl compounds is a classical yet versatile method for constructing complex molecular architectures in a single step. However, the regioselectivity is typically governed by the electronic properties of the alkene moiety, leading to the introduction of a nucleophile at the β‐position and an electrophile at the α‐position. Herein, we report a palladium‐catalyzed dicarbofunctionalization of acrylamides via anti‐Michael‐type addition, achieving reverse regioselectivity relative to traditional approaches. This strategy enables the efficient incorporation of various (hetero)arene nucleophiles at the α‐position and carbon electrophiles, including iodoarenes, vinyl iodides, and iodomethane, at the β‐position to furnish dicarbofunctionalized amides in good yields. Mechanistic investigations suggest that the reaction proceeds through an alkylpalladium intermediate formed via the α‐addition of a nucleophile.

Valley-Selective Optical Absorption and Giant Exciton Binding Energy of Breathing Kagome Semiconductor with Nearly Flat Band.

Endowed with topological flat band and dispersive Dirac cones, layered Kagome materials, which are expected to exhibit distinctive electronic and optical properties, have garnered significant attention in the forefrontier research of condensed matter physics. Using density functional theory and many-body perturbation theory, here we study the optical and excitonic properties of tunable two-dimensional (2D) breathing Kagome material Ta3SBr7 with topologically nontrivial flat band. Originated from the bulk counterpart, two thermodynamically stable structures are proposed, suggesting a new geometric degree of freedom for controlling the electronic and optical properties of the breathing Kagome lattice. Both Ta3SBr7 monolayers exhibit momentum selective optical absorption, whose mechanism is unveiled from the detailed analysis of the dispersion, symmetry, and valley-contrasting Berry physics of electronic band structure. Because of the existence of characteristic nearly flat bands, the ground-state excitons of both Kagome structures possess exceptionally large binding energies up to 1.1 eV. Moreover, this geometric degree of freedom also results in significant differences in the optical activity and exciton radiative lifetimes for ground-state excitons in these two structures. Our results showcase the potential of Kagome semiconductors not only in the manipulation of excitonic behaviors but also in fundamental physics, such as fractional Chern insulators at zero applied magnetic field.

Oxidation Process and Addition of Zn and Te Lead to the Enhancement of Thermoelectric Figure of Merit in p-Type Bi2Te3.

To date, Bi2Te3-based systems are the most promising thermoelectric materials near room temperature for Peltier cooling and energy harvesting. Further improvement of the thermoelectric figure of merit zT is required to broaden the application of Bi2Te3-based thermoelectrics. In this study, we investigated the critical role of oxidation in the thermoelectric performance of p-type Bi0.45Sb1.55Te3 and proposed a way to improve the performance. Impurity oxides inevitably formed during the fabrication processes of constituent elements, leading to lowered mobility. To solve this problem, an oxygen getter element, Zn, was added to capture the oxygen from the Bi0.45Sb1.55Te3 matrix to increase the mobility. Moreover, the formed byproduct ZnO effectively scattered heat-carrying phonons simultaneously. The control of the oxidation process and the addition of Zn and Te led to a 30% enhancement in the zT of Bi0.45Sb1.55Te3 with the decoupling of improved electronic properties and reduced lattice thermal conductivity.

Phenyldithiafulvene-Substituted Ferrocene Derivatives as Redox-Regulated Molecular Switches.

We designed a new type of redox-active molecular triad in which two electron-donating dithiafulvene (DTF) groups are connected to a central ferrocene (Fc) hinge unit through phenylene linkers. Three structural isomers of the (DTF)2-Fc system were synthesized through Suzuki-Miyaura cross-coupling followed by phosphite-promoted olefination reactions. The molecular structures and solid-state properties of these compounds were investigated by X-ray single-crystallographic analysis. Their electronic absorption and electrochemical properties in the solution phase were examined using UV-vis spectroscopy and cyclic voltammetry. Our studies showed that these compounds possess multistage redox activities due to the presence of electron-donating DTF and Fc groups, while detailed redox behaviors are dependent on the substitution patterns and steric crowdedness of each compound. To gain deeper insight, we performed density functional theory (DFT) and molecular dynamics (MD) simulations to examine the conformational and electronic properties of these compounds in neutral and different oxidation states. Furthermore, the para-substituted (DTF)2-Fc was found to show intriguing supramolecular interactions with γ-cyclodextrin.

Investigation of Electronic and Transport Properties of Zigzag Aluminium Nitride Nanoribbon for Magnetoresistive Devices using Selective Edge Chlorination

AbstractIn this work, the utility of Zigzag Aluminium Nitride Nanoribbons (ZAlNNR) for voltage‐controlled magnetoresistive devices is investigated using the DFT‐NEGF approach. Based on energy calculations and magnetic moment analysis, it is proposed that selective edge chlorination of ZAlNNR leads to the magnetic ground state (AFM). To examine the impact of electrode magnetization on transport properties, the curve is calculated for parallel and antiparallel spin orientation of the electrodes. For parallel cases, spin‐filtering efficiency (SFE) is calculated, which is at various voltages, and also observe negative differential resistance (NDR) behavior. In the antiparallel case, it is observed that both finite transmission and zero transmission regions for variable bias voltage. Hence, an oscillatory current behavior is observed in this case. Finally, magnetoresistance (MR) is calculated in both spin‐up and spin‐down cases, which is of the order of at (for spin‐up configuration). Such large values of SFE and MR make it an appropriate choice for spin filter/voltage‐controlled magnetic tunnel junctions (MTJs).

Insights into the mobility of rare earth complexes in groundwater-rock interactions: A geochemical view from modeling of computational chemistry.

Insights into the mobility of rare earth complexes in groundwater-rock interactions: A geochemical view from modeling of computational chemistry.

First-principles study of electronic and optical response properties of bimetallic-sulphide heterostructure supported dithiocarbonate complex for organic solar cells

The use of molecular complexes in improving the transport properties of active layer materials for organic solar cells has been enormous in the recent era. The current study focuses on the transport and optical properties of dithiocarbonate-based complexes on Tin sulphide/Cobalt sulphide heterostructure. The charge transfer properties show electronegativity features for the N-butylamine complex, whereas electropositive transport features are observed for the N-dodecyl amine and mixed (N-butylamine/N-dodecylamine) complex blend. This charge transfer behaviour is consistent with typical acceptor–donor features, which are associated with metal-thiocarbamate complex transport. The optical features for dithiocarbonate-based complexes supported metal sulphide heterostructure show increased absorption and reflective plasmonic features in comparison with pristine metal sulphide heterostructure. The study proposes the incorporation of a dithiocarbonate complex as support for metal sulphide heterostructure active layer material that can be used to drive improved charge transport and localized surface plasmon resonance, which is crucial for charge transport in organic solar cell devices.

Adsorption of Silver Clusters on Naphthalene: Theoretical Insights into Structural, Energetic, Electronic, and Infrared Properties.

In the present study, we carry out a comprehensive investigation of the structural, bonding, and infrared spectral properties of the low-energy complexes of silver clusters Agn (n = 1-8) adsorbed on naphthalene C10H8 (Nap). The structural properties are obtained through a systematic multimethod global optimization scheme. The potential energy surfaces of the complexes are first explored at the density functional-based tight binding level of theory via extensive Monte Carlo parallel tempering simulations complemented by gradient-driven quenching, thus providing prescreened samples of low-energy structural conformations. The most stable isomers are then reoptimized at the density functional theory level using a functional that includes dispersion, namely B3LYP-D3BJ. The properties of the global minima are analyzed at the latter level. Unsurprisingly, the structures of Agn adsorbates within the most stable complexes are close to those of the bare clusters. Regarding 2D Agn structures (n = 2-6), those with Agn perpendicular to the Nap plane are found to be the most stable for n = 2-4, while parallel conformations are preferred for n = 5 and 6. The significant role of dispersion interactions in the stability of these complexes is shown. The study of the influence of Agn adsorption on the evolution of the HOMO-LUMO band gaps and vertical ionization potentials (VIPs) shows that the odd-even alternation of the adsorbate cluster electronic properties is maintained and that the VIP decreases with size. Finally, the influence of the adsorption of Agn on the infrared properties of Nap is analyzed: small shifts are observed as well as the appearance of new bands due to symmetry reduction. The essential novelty consists of relative intensity changes reflecting charge transfer (though not dominant) from Nap to Agn. Our study globally shows that Nap-Agn interactions lead to a modulation of the electronic and vibrational properties of Agn and Nap. This could be of interest for structural diagnosis and reactivity. Perspectives concerning the use of the present structural search methodology for more complex hybrid metal-organic systems in various application fields are suggested.

Enhanced Lattice Coherences and Improved Structural Stability in Quadruple A-Site Substituted Lead Bromide Perovskites.

Lead halide perovskites (LHPs) are promising materials for efficient photovoltaic devices; however, they often encounter limited structural stability and degradation problems that limit their technological potential. This study investigates a novel perovskite composition consisting of (Cs, MA, FA, GA)PbBr3, abbreviated as (4cat)PbBr3, to effectively enhance phase stability and optoelectronic characteristics. The spectroscopic data reveal improved structural order, electronic properties, and dynamic lattice response in a cubic phase, which is uniquely stabilized by the specific cation composition down to 80 K. Superior optoelectronic properties are verified by increased photoluminescence (PL) and 20-fold higher electron mobility, when compared to the single-cation composition, MAPbBr3. Notably, the ultrafast Terahertz-induced Kerr effect (TKE) reveals a dominating 1.1 THz octahedral twist mode, also observed in MAPbBr3, however with a doubled phonon coherence time in (4cat)PbBr3 at 80 K. The observation of higher structural order in the 4-cation composition is thus reflected by the prolonged lattice coherences, indicating enhanced dynamic screening effects that can explain the improved optoelectronic properties of (4cat)PbBr3. This study therefore sheds light on the influence of the A-site cation composition on the inorganic sublattice and its coherent dynamics, highly relevant to perovskite-based photovoltaic and optoelectronic technologies.

Staggered ABC-Stacking Cobalt-Triptycene Framework for Accelerating CO2 Photoreduction.

Metal-organic frameworks are highly efficient photocatalysts due to their highly tunable structures and favorable electronic properties. However, achieving control over framework stacking arrangements, such as the staggered ABC-stacking, presents significant challenges. This difficulty arises from the inherently unfavorable energetics of the ABC arrangement and weaker π-π interactions compared to other stacking modes. Herein, a cobalt-triptycene framework with a staggered ABC-stacking arrangement was successfully synthesized in the aqueous phase, achieving a 90% yield. Experimental evaluations revealed that this framework achieved a CO production rate of 4.43 mmol g⁻¹ h⁻¹, which is comparable to the most reported MOF-based photocatalysts for CO2 reduction. Moreover, density functional theory calculations and molecular dynamics simulations indicated that the ABC-stacking cobalt-triptycene framework exhibits lower activation energy (0.079 eV) for water molecules, reduced Gibbs free energies for key intermediates *COOH (0.76 eV) and *H (0.73 eV), and the highest reaction rate increment (7.488 times). Furthermore, principal component analysis reveals a strong correlation between the CO production rate and factors such as the Ik value, optical bandgap, and ΔG*H, revising the previous held notion that ΔG*COOH is the primary determinant of catalytic performance. These results offer valuable insights into the design principles of advanced photocatalysts for CO2 reduction.

From Donor-Acceptor Ligands to Smart Coordination Polymers: Cyanothiazole-Cu(I) Complexes for Multifunctional Electronic Devices.

Cyanothiazoles, small and quite overlooked molecules, possess remarkable optical properties that can be fine-tuned through coordination with transition metals. In this study, we investigate a promising application of cyanothiazoles, where their combination with copper(I) iodide forms a new class of complexes exhibiting outstanding optical properties. X-ray crystallography of copper(I) iodide complexes with isomeric cyanothiazoles revealed key structural features, such as π-π stacking, hydrogen bonding, and rare halogen---chalcogen I---S interactions, enhancing stability and reactivity. Advanced spectroscopy and computational modeling allowed precise identification of spectral signatures in FTIR, NMR, and UV-Vis spectra. Fluorescence studies, along with EXAFS and XANES synchrotron analyses, highlighted their unique thermal and electronic properties, providing a solid foundation for further research in the field.

Bioactivity of novel isoxazole-fused heterocycles: comprehensive antimicrobial, antioxidant activities, SwissADME predictions, molecular docking, and DFT analysis.

Among the foremost goals for organic chemists is to discover novel approaches for the synthesis of a particular heterocyclic and its design. Our approach focused on the vital precursor 4-acetyl-3-phenylisoxazol-5(4H)-one 3, as this molecule has an endocyclic carbonyl function in position 5 adjacent to the substituted acetyl function at site 4. Therefore, compound 3 was a crucial component of many types of fused isoxazole. The investigators provide a straightforward synthesis of fused isoxazole from the following categories: pyrano[3,2-d]isoxazole 4 & 6, isochromeno[4,3-d]isoxazole 5, isoxazolo[4',5':5,6]pyrano[3,4-c]pyridine 7, thieno[3',4':4,5]pyrano [3,2-d]isoxazole 8, pyrazolo[4,3-d]isoxazole 10a,b and 11a,b, and isoxazolo[4,5-c]pyridazine derivatives 14a,b. The target compounds and their structures were supported by the results of 1H-NMR, IR and mass spectroscopy. Molecular docking studies highlighted strong binding affinities to bacterial enzymes crucial for cell wall synthesis, while DFT calculations provided deep insights into their electronic properties and stability. Additionally, the antioxidant potential of compounds 11a,b was assessed using DPPH and ABTS assays, showing impressive concentration-dependent activity. Addressing the critical issue of antibiotic resistance, especially due to β-lactamases, molecular docking affirmed the high binding propensity of these derivatives with essential β-lactamase proteins (PDB: 1CK3, 6MU9, and 6W2Z). These findings underscore the promise of isoxazoline derivatives as powerful antimicrobial and antioxidant agents, paving the way for further development in combating bacterial resistance and oxidative stress.

Structural, opto-electronic, and elastic responses of double perovskite K2NaTiA6 (A=Cl and Br) for photovoltaic application: A DFT study

The physical properties of double halide perovskite K2NaTiA6 ([Formula: see text] and Br) were investigated using the first principles study root using the Wien2k package for renewable energy generation and solar cell applications. Research on halides is expanding in the field of optoelectronics and is believed to meet the requirements for addressing energy shortages. Moreover, Pugh and Poisson’s ratios indicate their elastic properties. The electronic properties and calculated the bandgaps using modified Becke–Johnson (mBJ) potentials, resulting in bandgaps of 1.09[Formula: see text]eV and 1.36[Formula: see text]eV for K2NaTiCl6 and K2NaTiBr6, respectively. The optical properties were evaluated using complex dielectric functions, and the results showed optimal light absorption in the infrared (IR) region. These findings suggest their potential for optoelectronic, device applications and are expected to support future experimental research on the suitability of K2NaTiX6 ([Formula: see text] and Br) for optical devices.

Electronic band structure, magnetic and thermoelectric properties of sodium and lanthanum cobaltites: ab initio PAW approach

ABSTRACT The electronic band structure and thermoelectric properties of the NaCoO2 and LaCoO3 cobaltites have been studied by the PAW method. The thermoelectric characteristics were calculated on the basis of Boltzmann–Onsager theory taking into account electron scattering by optical phonons, and the thermal conductivity coefficient was calculated using the Slack approximation. For LaCoO3 with electronic conductivity, in accordance with experimental data, the change of sign of Seebeck coefficient is noted at high temperatures. It is shown for NaCoO2 with hole conductivity that the sign of Seebeck coefficient can also be expected to change at high temperature. By varying starting magnetic moments, five solutions compatible with the LaCoO3 semiconductor conductivity were achieved. The magnetic states of cobalt atoms at semiconductor conductivity may have spin value S = 0 or 3/2.

Spatially resolved optoelectronic puddles of WTe2-2D Te heterostructure.

Two-dimensional (2D) semiconductors have attracted significant scientific interest because of their optical properties. Their applications in optoelectronic devices can be further expanded by combining them to form heterostructures. We characterized a WTe2-2D Te heterostructure through local probing of the photocurrent with respect to the magnitude, phase, and position. Photocurrent generation within the device is divided into distinct regions: photo-thermoelectric effects occur solely at the 2D Te-Au junction area, PV-dominant effects at the 2D-WTe2 interface, and thermoelectric-to-photovoltaic crossover effects at the WTe2-2D Te overlap area. These different photocurrents cannot be fused into a single domain because each area is governed by different generation mechanisms, which depend on the location of the device. The power dependence of each photocurrent type also varies within the device. Our results indicate that careful material selection and device structure design, based on the electronic, optical, and thermal properties of the channel materials, are essential to avoid forming different optoelectronic puddles that could counteract each other within a single device.

First-Principles Modeling of the Electronic and Optical Properties of Biogenic Crystals: The Case of Anhydrous Guanine

First-Principles Modeling of the Electronic and Optical Properties of Biogenic Crystals: The Case of Anhydrous Guanine