Electrons Research Articles

Crystal structures and electronic and magnetic properties of Janus bilayer Cl[formula omitted]Cr[formula omitted]I[formula omitted]

Two-dimensional (2D) magnetic material CrI3 has aroused extensive attention, because it could provide a new platform for investigating the relations between crystal structures and electronic and magnetic properties. Here, we study crystal structures and electronic and magnetic properties of three configurations (Cl-Cl I-I and Cl-I) of Janus bilayer Cl3Cr2I3 with two stacking orders (AB and AA1/3) by using the first principles approach incorporating the spin–orbit coupling (SOC) effect and the dipole correction. It is found that the spin polarization and the SOC effect can expand the lattice constant and the interlayer distance (ID) of the three configurations. Especially, the ID of the I-I configuration is 1 Å larger than that of the Cl-Cl configuration. The total energy calculation results show that the atomic configuration, the SOC effect and the stacking order play an important role in determining the magnetic ground states of the Janus layers. Our results indicate the atomic configurations of the Janus bilayers are not conducive to the increase of critical temperature. Interestingly, the Cl-I configuration has a vertical dipole moment, and its AFM state has large spin splitting. It is revealed that the non-periodic structure, the symmetry breaking of the average potential and the weak interlayer interaction lead to the vertical dipole moment and the abnormal AFM state that is not the most stable state.

Beyond the random phase approximation (RPA): first principles calculation of the valence EELS spectrum for KBr including local field, quasiparticle, excitonic and spin orbit coupling effects.

Beyond the random phase approximation (RPA): first principles calculation of the valence EELS spectrum for KBr including local field, quasiparticle, excitonic and spin orbit coupling effects.

Thionation of conjugated porphyrin with enhanced photodynamic and photothermal effects for cancer therapy

Phototherapy has emerged as a promising modality for cancer treatment in recent years, owing to its precise temporal control and minimally invasive nature. Here, two new organic porphyrin molecules, denoted as ONP and SNP, were designed and synthesized with an acceptor–donor–acceptor (A-D-A) architecture. The donor–acceptor (D-A) pairs in molecules facilitated the intermolecular charge transfer (ICT), thereby amplifying near-infrared (NIR) absorbance and promoting nonradiative heat generation. Notably, the substitution of oxygen atoms with sulfur in naphthalimides (NI) led to significant change of their photophysical and photochemical properties. Specifically, the sulfur atoms exhibited pronounced spin–orbit coupling (SOC) effect, leading to efficient photoinduced intersystem crossing (ISC) processes, thus facilitating the generation of reactive oxygen species (ROS). Upon self-assembly, the formed nanomaterials (ONP NPs and SNP NPs) exhibited spherical morphology with average size about 150 nm. The biocompatibility and photocytotoxicity of nanoparticles against Hepa1-6 cells were evaluated using the CCK-8 assay. Additionally, the synergistic effects (photodynamic therapy and photothermal therapy) of SNP NPs were confirmed through diverse in vitro experiment under 690 nm laser irradiation. The generation of intracellular ROS by SNP NPs was confirmed with DCFH-DA as probe. This study provides an ingenious strategy for developing organic nanomaterials with high treatment efficiency through synergistic photodynamic/photothermal effects.

JWST reveals the rapid and strong day-side variability of 55 Cancri e

Context. The nature of the close-in rocky planet 55 Cnce is puzzling, despite it having been observed extensively. Its optical and infrared occultation depths show temporal variability, in addition to a phase curve variability observed in the optical. Aims. We wish to explore the possibility that the variability originates from the planet being in a 3:2 spin–orbit resonance, and thus showing different sides during occultations. We proposed and were awarded Cycle 1 time at the James Webb Space Telescope (JWST) to test this hypothesis. Methods. JWST/NIRCam (Near Infrared Camera) observed five occultations (secondary eclipses) of the planet – of which four were observed within a week – simultaneously at 2.1 and 4.5 µm. While the former gives band-integrated photometry, the latter provides a spectrum between 3.9–5.0 µm. Results. We find that the occultation depths in both bandpasses are highly variable and change between a non-detection (−5 ± 6 ppm and 7 ± 9 ppm) to 96 ± 8 ppm and 119−19+34 ppm at 2.1 µm and 4.5 µm, respectively. Interestingly, the variations in both bandpasses are not correlated and do not support the 3:2 spin-orbit resonance explanation. The measured brightness temperature at 4.5 µm varies between 873–2256 K and is lower than the expected day-side temperature of bare rock with no heat redistribution (2500 K), which is indicative of an atmosphere. Our atmospheric retrieval analysis of occultation depth spectra at 4.5 µm finds that different visits statistically favour various atmospheric scenarios including a thin outgassed CO/CO2 atmosphere and a silicate rock vapour atmosphere. Some visits even support a flat line model. Conclusions. The observed variability could be explained by stochastic outgassing of CO/CO2, which is also hinted at by retrievals. Alternatively, the variability observed at both 2.1 and 4.5 µm could be the result of a circumstellar patchy dust torus generated by volcanism on the planet.

Stability of spin-spiral magnetic structures in Mn2PtSn

The stability of a long-periodic homogeneous spin-spiral configuration in an inverse tetragonal Heusler compound, Mn2PtSn, is studied with the help of density functional theory calculations. The energetically most stable collinear magnetic state in this system is the ferrimagnetic one. However, the existence of negative phonon frequency makes this configuration dynamically unstable. The energy dispersion plots reveal that an energy minimum exists at q=0.1 along [100] and [110] propagating directions, which correspond to a stable non-collinear configuration compared to the collinear spin states. The inclusion of spin–orbit coupling further reduces the ground-state energy without changing the q-vector of the energy minima. The cycloidal spiral configuration, where the spins rotate at an angle of 36° along the propagating direction, is found to be more stable than the screw spiral configuration. The calculated density of state plots further supports the stability of the non-collinear cycloidal spin order. This stable, non-collinear spin-spiral configuration of Mn2PtSn makes this compound a prospective material for spintronics device applications.

Studying bimetals copper-indium for enhancing PCN photocatalytic CO2 reduction activity and selectivity mechanism

In this work, a bimetallic indium-copper-doped atomically dispersed Cu-In-PCN photocatalyst was prepared by thermal polymerization, and it exhibits remarkable photocatalytic CO2 reduction activity with CO yield of 113.56 µmol g−1 and a selectivity nearly 96 %. Additionally, experimental investigations and DFT calculations reveal the mechanisms underpinning the high performance of Cu-In-PCN catalyst, that Cu 3d and In 5p orbitals contribute to the band composition of Cu-In-PCN and reduced the bandgap, the electrons from PCN transfer to copper active sites and increasing the electron density for CO2 reduction. Furthermore, the Cu-In bimetallic lowered the free energy of COOH* intermediate, which more easily conversion to CO via dehydroxylation than PCN, Cu-PCN, and In-PCN. In situ FTIR show that the COOH* is the key intermediate in the photocatalytic reduction of CO2 to CO. This work makes up for the current shortcomings of using bimetallic-doped PCN for photocatalytic CO2 with low selectivity and unclear mechanism.

Insights into the removal of sulfamethazine and sulfonamide-resistant bacteria from wastewater by Fe-Mn spinel oxide modified cow manure biochar activated peroxymonosulfate: A nonradical pathway regulated by enhanced adsorption and 3d orbital electron reconstruction

Effectively regulating nonradical pathways is crucial for adapting to complex water environments in sulfate radical-based advanced oxidation processes (SR-AOPs). This study prepared manganese ferrite-modified cow-manure biochar composites (BC-FM) as peroxymonosulfate activators to remove sulfamethazine (SMT) and sulfonamide-resistant bacteria (SA-ARB) from wastewater. The extensive conjugated graphitic structure in biochar induced Fe 3d orbital electron reconstruction, promoting empty orbitals formation and enhancing peroxymonosulfate inner-sphere complexation. This facilitated 100 % electron-transfer-dominated nonradical regulation. BC-FM exhibited remarkable catalytic performance, with apparent rate constant of 0.170 min−1 for SMT, inactivating ∼8.6 log of SA-ARB, and effectively blocking horizontal transfer of antibiotic resistance genes in both single and complex pollution systems (SMT/SA-ARB). Moreover, ion leaching experiments, cycling tests, real-water experiments, fluidized-bed and fixed-bed experiments demonstrated BC-FM’s potential for prolonged utilization and practical implementation. This study offers new insights into designing high-performance, environment-friendly bimetal catalysts and provides a basis for remediating organic contaminants with SR-AOPs in livestock wastewater.

Electron-withdrawing effect of polyoxometalates in Cu(I)-based metal–organic frameworks for enhanced azide-alkyne “click” reaction

Boosting the nucleophilicity of Cu(I) sites is an essential strategy to enhance the efficiency of Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction. In this work, a Lindquist-type polyoxometalate (POM)-based metal–organic framework, [CuI4(W6O19)2(L)]·2H2O (NEAU-1), was synthesized via an in-situ solvothermal method. Single-crystal X-ray diffraction results reveal that NEAU-1 exhibits a sandwich structure, with POMs intercalated between the two-dimensional layers formed by resorcin[4]arene ligands and Cu(I) ions. NEAU-1 possesses abundant Cu(I) active sites and high chemical stability, making it an effective heterogeneous catalyst for the CuAAC reaction. More importantly, the presence of POMs effectively reduces the electron cloud density around Cu(I) sites, significantly lowering the energy barrier for the formation of copper-acetylide compounds and facilitating subsequent nucleophilic reactions. The synergistic catalytic effect of POMs and Cu(I) can achieve a conversion rate of over 99 % for benzyl azide and phenylacetylene within 40 min. This work presents a sustainable molecular-level strategy to enhance the activity of the CuAAC reaction.

Enhanced VOCs adsorption on Group VIII transition metal-doped MoS2: A DFT study

Volatile organic compounds (VOCs) represent a significant category of toxic and harmful air pollutants. Among the various abatement techniques available for VOCs, adsorption technology is widely recognized as a cost-effective solution. In this study, density functional theory (DFT) was employed to calculate and compare the adsorption capacities of six typical VOCs on pristine MoS2 and MoS2 modified with Group VIII (MVIII) transition metals atoms. It is found that MVIII-MoS2 monolayer demonstratesa significant enhancement in adsorption capabilities for VOCsrelative to pristine MoS2. Among these Group VIII transition metals atoms, Fe, Ru and Os atoms exhibited the most significant VOCs adsorption enhancement, with Fe atoms demonstrating a particularly pronounced effect. This suggests a synergistic interaction between the metal dopants and the substrate. Density of states (DOS) and charge density difference analyses provided further insights into the mechanisms underlying improved adsorption capability. Interestingly, the introduction of MVIII atoms results in the emergence of a novel state density within the surface state of MoS2, thereby facilitating enhanced electron transfer between VOCs and the substrate. Charge density difference calculations further corroborated these findings, with certain configurations exhibiting significant electron cloud overlap. Such modification leads to more active electron transfer, thereby increasing the substrate’s affinity for VOC molecules and consequently improving the adsorption efficiency. The findings not only enhance the comprehension of VOC adsorption mechanisms on MoS2 but also underscore the potential of metal-doped two-dimensional materials for environmental applications.

Design and first tests of the trapped electrons experiment T-REX.

Gyrotrons are essential for electron cyclotron resonance heating in fusion reactors, making efficient operation crucial for advancing fusion energy. Past experiments revealed instability issues due to trapped electrons in the magnetron injection gun (MIG) region, causing undesired currents and operational failures. To address this, tight manufacturing tolerances are required for the MIG geometry [Pagonakis etal., Phys. Plasmas 23, 023105 (2016)]. We present the initial findings of the trapped electrons experiment developed at the Swiss Plasma Center, designed to understand the physics of electron clouds in gyrotron MIGs. T-REX replicates MIG geometries, as well as their typical electric and magnetic fields, and it is supported by 2D particle-in-cell simulations with the FENNECS code [Le Bars etal., Phys. Plasmas 29, 082105 (2022); Le Bars, Ph.D. thesis, EPFL, Lausanne, 2023]. The setup includes two coaxial electrodes in a vacuum chamber atop a superconducting magnet, with a central electrode biased to negative DC voltages and an outer one at the ground, creating a radial electric field (1-2MV/m) and an axial magnetic field (B < 0.4T). This setup mimics Penning-Malmberg traps. We present the experimental device and first findings on current distribution and also a qualitative comparison with FENNECS simulations [Le Bars etal., Comput. Phys. Commun. 303, 109268 (2024)]. Planned diagnostics include optical emission spectroscopy, phosphor screen imaging, streak camera imaging, and potentially electric field distribution via the Stark effect. This research aims to enhance gyrotron performance and reliability in fusion energy systems.

Sulfur atom occupying surface oxygen vacancy to boost the charge transfer and stability for aqueous Bi2O3 electrode

Oxygen vacancies (Ov) within metal oxide electrodes can enhance mass/charge transfer dynamics in energy storage systems. However, construction of surface Ov often leads to instability in electrode structure and irreversible electrochemical reactions, posing a significant challenge. To overcome these challenges, atomic heterostructures are employed to address the structural instability and enhance the mass/charge transfer dynamics associated with phase conversion mechanism in aqueous electrodes. Herein, we introduce an atomic S–Bi2O3 heterostructure (sulfur (S) anchoring on the surface Ov of Bi2O3). The integration of S within Bi2O3 lattice matrix triggers a charge imbalance at the heterointerfaces, ultimately resulting in the creation of a built-in electric field (BEF). Thus, the BEF attracts OH− ions to be adsorbed onto Bi within the regions of high electron cloud overlap in S–Bi2O3, facilitating highly efficient charge transfer. Furthermore, the anchored S plays a pivotal role in preserving structural integrity, thus effectively stabilizing the phase conversion reaction of Bi2O3. As a result, the S–Bi2O3 electrode achieves 72.3 mAh g−1 at 10 A g−1 as well as high-capacity retention of 81.9% after 1600 cycles. Our innovative S–Bi2O3 design presents a groundbreaking approach for fabricating electrodes that exhibit efficient and stable mass and charge transfer capabilities. Furthermore, it enhances our understanding of the underlying reaction mechanism within energy storage electrodes.

Control of spin–orbit torque-driven domain nucleation through geometry in chirally coupled magnetic tracks

The interfacial Dzyaloshinskii–Moriya interaction (DMI) can be exploited in magnetic thin films to realize lateral chirally coupled systems, providing a way to couple different sections of a magnetic racetrack and realize interconnected networks of magnetic logic gates. Here, we systematically investigate the interplay between spin–orbit torques, chiral coupling, and the device design in domain wall racetracks. We show that the current-induced domain nucleation process can be tuned between single-domain nucleation and repeated nucleation of alternate domains by changing the orientation of an in-plane patterned magnetic region within an out-of-plane magnetic racetrack. Furthermore, by combining experiments and micromagnetic simulations, we show that the combination of damping-like and field-like spin–orbit torques with DMI results in selective domain wall injection in one of two arms of a Y-shaped device depending on the current density. Such an element constitutes the basis of domain wall based demultiplexer, which is essential for distributing a single input to any one of the multiple outputs in logic circuits. Our results provide input for the design of reliable and multifunctional domain wall circuits based on chirally coupled interfaces.

Multiple Topological Phases with Electronic Correlation in Intrinsic Ferromagnetic Semimetal VI3 Monolayer.

2D topological materials with magnetic ordering have become hot topics due to their nontrivial band topology and quantum states. In this work, the second-order topological states and evolution of linear band crossing are successfully predicted utilizing the effective k· p and tight binding models in the intrinsic ferromagnetic VI3 monolayer under various effective Hubble interaction Ueff. Upon inclusion of spin orbit coupling, a small bandgap (Eg-1) of 12.7 meV is opened with a Chern invariant C = -1 at Ueff = 0 eV. The Eg-1 undergoes a transition from the non-trivial state to trivial state at Ueff = 0.80 eV, accompanied by the appearance of Dirac cone. Remarkably, the increase of Ueff causes the band inversion and adjustment of crystal symmetry, resulting in two unreported coexistingtopological bandgaps (Eg-2 and Eg-3). Furthermore, a gapless node-loop appears at Ueff = 1.06 eV and disappears at Ueff = 1.09 eV around Γ point. Moreover, for the first time, the existence of second-order topological states with quantized corner fractional charges (e/3) is also observed in the VI3 monolayer at Ueff ≥0.96 eV. These results make the VI3 monolayer a compelling candidate for exploring topological devices.

Tidal evolution and spin–orbit dynamics for bodies in the viscous regime

Tidal evolution and spin–orbit dynamics for bodies in the viscous regime

The origin of ferroelectricity in HfO2 from orbital hybridization and covalency

Fluorite-structured HfO2 ferroelectrics exhibit remarkable ferroelectricity owing to the robust thickness scalability, rendering them promising for next-generation ferroelectric memories. Unlike the well-understood perovskite structured ferroelectrics, such as Pb(Zr,Ti)O3, the origin of ferroelectricity in HfO2 remains elusive, which impedes the experimental fabrication of pure and stable ferroelectric orthorhombic phase in films. This study seeks to elucidate its origin by analyzing the covalent nature of local chemical bonding and changes in orbital hybridization and by catching the typical feather of the half-unit-cell spacer/polar layer in the orthorhombic phase. Notably, we find that the differences in the hybridization intensity of the 2s orbitals of two types of O atoms (OI and OII) and 5d orbitals of Hf atoms play a crucial role in inducing ferroelectric distortion. Furthermore, we demonstrate that the intrinsic mechanisms of stress in enhancing the ferroelectricity of HfO2 originate from the modulation of orbital hybridization intensity of the Hf–O bonds. These insights provide a vital theoretical foundation for further exploration of ferroelectric phase transitions and property modulation in HfO2 and similar fluorite-structured ferroelectrics.

Exploring Ion Polarizabilities and Their Correlation with van der Waals Radii: A Theoretical Investigation.

Polarizability (α) is a fundamental property which measures the tendency of the electron cloud of an atom, ion, or molecule to be distorted by electric field. Polarizability contributes to important physical properties such as molecular interactions or dielectric constants; thus, it is essential to have accurate polarizabilities in molecular simulations. However, it remains a challenge to develop polarizable force fields (FFs) for ions in computational chemistry. In particular, a comprehensive set of polarizabilities for ions has not been derived. Herein, we derived a systematic set of polarizabilities for atoms and ions across the periodic table based on high-level quantum mechanics calculations. These values have excellent agreement with experimental data. Furthermore, we examined the relationship between the obtained polarizabilities and the van der Waals (VDW) radii (RVDW) that we previously determined (J. Chem. Theory Comput., 2023, 19, 2064). Two relationships, RVDW ∝ α1/7 and RVDW ∝ α1/3, proposed in previous studies were examined in the present work. Our results indicated the former relationship, which was derived based on the quantum harmonic oscillator model, prevails for atoms and cations, but neither relationship provides a satisfactory fit for anions. This is consistent with the tight-binding nature of the electrons in atoms and cations, while it is more challenging to quantify the polarizabilities of anions because of their more dispersed electron clouds. Moreover, we compared different approaches to determine the dispersion coefficients, including the London equation, Slater-Kirkwood equation, symmetry-adapted perturbation theory (SAPT) calculations, and time-dependent density functional theory method, along with the approach based on VDW constants. Our results indicated that although different approaches predict deviated magnitudes for the dispersion coefficients, their predictions are highly correlated, implying that each of these approaches can be used to evaluate dispersion interactions after proper scaling. Finally, we have developed a parametrization strategy for the 12-6-4 model based on the obtained insights. We specifically compared the performance of the 12-6-4 model with SAPT and SobEDA analyses to model interactions involving Na+/Mg2+ and various ligands containing He, Ne, Ar, H2O, NH3, [H2PO4]-, and [HPO4]2-. Our results demonstrate that the 12-6-4 parameters effectively reproduce both the total interaction energy and the individual energy components (electrostatics, exchange-repulsion, dispersion, and induction), highlighting the physical robustness of the 12-6-4 model and the effectiveness of our parametrization approach. This study has significant implications for advancing the development of next-generation ion models and polarizable FFs.

Magnetic interaction induced splitting of bands in hexagonal RMnO3 (R = Lu, Y, and Sc) compounds

In this work, calculations using non-collinear spin density functional theory were performed to study the electronic band structures for different antiferromagnetic orders in hexagonal RMnO3 (R = Lu, Y, and Sc) compounds. These are an important class of multifunctional materials with interesting properties for various applications. By comparing the band structure of different magnetic configurations, it is observed that some of them exhibit band splitting that can be attributed to ferromagnetic interplane coupling. The energy splitting is significantly larger (331 meV) for the ScMnO3 compound, which probably has a higher interplane magnetic interaction. In addition, we report that the spin–orbit coupling also induces a splitting of bands in some regions of the Brillouin zone for those magnetic configurations with a weak magnetic moment along the hexagonal c-axis. These findings offer an intriguing insight into the topological characteristics of hexagonal manganites’ band structure, which was previously unexplored in existing literature. This discovery opens avenues for future investigations in this field.

Porous mesh poly-L-Cysteine and lamellar polynicotinamide-based electrochemical sensor for melatonin detection in milk and tablets

An poly L-Cys/NADH/GCE electrochemical sensor for melatonin (MT) detection was developed by electropolymerising reticulated poly L-cysteine (poly L-Cys) and lamellar poly-nicotinamide adenine dinucleotide (NADH) on a glassy carbon electrode (GCE). The morphology, elemental composition, and elemental states of the fabricated electrochemical sensor were characterized through scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). Additionally, the electrochemical behavior of melatonin on poly L-Cys/NADH/GCE was investigated through electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and differential pulse voltammetry (DPV). The results showed a linear relationship for MT across the concentration range of 0.1 to 1000.0 µmol/L, with linear equations Ip(µA) = 0.0978c(µmol/L) + 0.0981, R2 = 0.9937 (concentration range: 0.1–40.0 µmol/L), and Ip(µA) = 0.0137c(µmol/L) + 5.2741, R2 = 0.9636 (concentration range: 40.0–1000.0 µmol/L). The recoveries in milk samples ranged from 98.71 % to 107.98 %, with relative standard deviations (RSD) for actual tablet samples below 8.60 %. Furthermore, the electro-oxidation sites of MT and its reaction process were deduced by calculating electron orbitals and electron cloud diagrams.

Low-lying [formula omitted] electronic states of BiF: Perturbative versus variational approaches of spin–orbit coupling

The low-lying Ω states of bismuth monofluoride (BiF) below 50000 cm−1 have been theoretically studied using the multi-reference configuration interaction and the equation-of-motion coupled-cluster methods, where the spin–orbit coupling (SOC) effects are respectively considered perturbatively or variationally. Since the perturbative treatment of SOC is not a good approximation for the heavy atom Bi, the latter method exhibits higher accuracy and better agreements with the experimental spectroscopic constants. Our results show that the second 3Π state of BiF is due to the occupation on the Rydberg 7s-shell of Bi, which gives rise to the so-called “triplet C” state and its sub-states reported in the early literatures. With the help of our theoretical results, some experimentally assigned spectral bands with considerable confusion have also been clarified and reassigned.

A Novel Method to Constrain Tidal Quality Factor from A Nonsynchronized Exoplanetary System

We propose a novel method to constrain the tidal quality factor, Q′ , from an observed nonsynchronized star–planet system consisting of a slowly rotating low-mass star and a close-in Jovian planet, taking into account the coevolution of stellar spin and planetary orbit due to the tidal interaction and the magnetic braking. On the basis of dynamical system theory, the track of the coevolution of angular momentum from the fast-rotator regime for such a system exhibits the existence of a forbidden region in the Ωorb–Ωspin plane, where Ωspin and Ωorb denote the angular velocity of the stellar spin and planetary orbit, respectively. The forbidden region is determined primarily by the strength of the tidal interaction. By comparing the (Ωorb, Ωspin) of a single star–planet system to the forbidden region, we can constrain the tidal quality factor regardless of the evolutionary history of the system. The application of this method to the star–planet system NGTS-10–NGTS-10 b gives Q′≳108 , leading to a tight upper bound on the tidal torque. Since this cannot be explained by previous theoretical predictions for nonsynchronized star–planet systems, our result requires mechanisms that suppress the tidal interaction in such systems.