Dipolar Interactions Research Articles

Consistent theoretical description of nuclear spin long-lived states decay under conditions of reversible ligand-protein binding.

Determining the stability constant of the complex formed by an organic ligand with a protein is the first stage in the screening of new drugs. Nuclear spin long-lived states, in particular the singlet state, can be used to study the reversible binding of ligands to proteins. In a complex with a protein, the spins of the ligand interact with the spins of the protein, the system of protein and ligand nuclei can relax by a dipole-dipole mechanism, and the lifetime of the singlet state is strongly reduced. In this theoretical study, a system of encounter theory equations with the condition of fast relaxation in free protein was solved to determine the lifetime of the LLS in the presence of protein. It was shown that in the limit of fast chemical exchange, the relaxation of the LLS of the ligand nuclei due to dipole interaction with the protein nuclei is reduced to relaxation by the mechanism of dipole interaction with one proton of the protein, which is located at some effective distance from the ligand nuclei. Numerical calculations were made to test the applicability of the approximations used to process the experimental lifetime dependencies on the ligand concentration and external field, and it was shown that these approximations coincide with the limit of fast exchange in strong and weak magnetic fields, but not in the medium field. An analytical expression for the lifetime of the singlet state of ligand nuclei in an arbitrary magnetic field in the absence of protein was obtained.

Field-Induced Antiferromagnetic Correlations in a Nanopatterned Van der Waals Ferromagnet: A Potential Artificial Spin Ice.

Nano-patterned magnetic materials have opened new venues for the investigation of strongly correlated phenomena including artificial spin-ice systems, geometric frustration, and magnetic monopoles, for technologically important applications such as reconfigurable ferromagnetism. With the advent of atomically thin 2D van der Waals (vdW) magnets, a pertinent question is whether such compounds could make their way into this realm where interactions can be tailored so that unconventional states of matter can be assessed. Here, it is shown that square islands of CrGeTe3 vdW ferromagnets distributed in a grid manifest antiferromagnetic correlations, essential to enable frustration resulting in an artificial spin-ice. By using a combination of SQUID-on-tip microscopy, focused ion beam lithography, and atomistic spin dynamic simulations, it is shown that a square array of CGT islandas small as 150 × 150 × 60 nm3 have tunable dipole-dipole interactions, which can be precisely controlled by their lateral spacing. There is a crossover between non-interacting islands and significant inter-island anticorrelation depending on how they are spatially distributed allowing the creation of complex magnetic patterns not observable at the isolated flakes. These findings suggest that the cross-talk between the nano-patterned magnets can be explored in the generation of even more complex spin configurations where exotic interactions may be manipulated in an unprecedented way.

Enhancing Mass Transfer of Reactive Oxygen and Nitrogen Species in Plasma‐Activated Water: A Molecular Dynamics Study on the Impact of Plasma Electric Fields

ABSTRACTThis study investigates the impact of plasma electric fields on the mass transfer characteristics of reactive oxygen and nitrogen species (RONS), specifically NO2 and O3, in water using molecular dynamics simulations. The results demonstrate that the plasma electric field significantly increases the thickness of the Gibbs Dividing Surface, reduces surface tension at the gas–liquid interface, and disrupts the hydrogen bond network. These changes lead to an enhanced solubility and self‐diffusion coefficient for both NO2 and O3. Due to stronger dipole–dipole interactions, NO2 exhibits superior mass transfer performance compared to O₃. This research provides theoretical support for the application of plasma‐activated water technology.

Tunable Single‐Phase White Light Emission from Complex Perovskite Sr3CaNb2O9: Dy3+/Eu3+ Phosphors

AbstractSr3CaNb2O9:Dy3+/Eu3+ phosphors with a complex perovskite structure are prepared using a high‐temperature solid‐ state reaction technique. These phosphors are doped either singly or in combination with Dy3+/Eu3+ ions, resulting in efficient energy transfer from Dy3+ to Eu3+ and thus tunable‐color emission. Under 353 nm excitation, the Sr3CaNb2O9:Dy3+ phosphor emits blue (492 nm), yellow (583 nm), and red (682 nm) light, with the optimal doping concentration of Dy3+ of 0.04%. When excited by 394 nm (7F0 → 5L6), the Sr3CaNb2O9:Eu3+ phosphor exhibits two most intense emissions centered at 593 nm (5D0 → 7F1) and 614 nm (5D0 → 7F2). The decrease in luminescence intensity with increasing doping concentration of Dy3+ and Eu3+ is due to the cross‐relaxation associated with electric dipole–dipole interaction. Photoluminescence emission measurements under excitations of 353 and 365 nm indicate that the Sr3CaNb2O9:0.04Dy3+/0.05Eu3+ phosphor shows excellent thermal stability, even at a temperature of 150 °C, where the luminescence intensity preserves 79% of its initial value at room temperature. The electroluminescence performance of the Sr3CaNb2O9:0.04Dy3+/0.05Eu3+ phosphor is tested with 365 nm LED chips for potential use in white LEDs. The results confirm that Sr3CaNb2O9:0.04Dy3+/0.05Eu3+ phosphor has great potential for use in high‐power white LED applications as a single matrix.

Ultrabroadband Visible-Near-Infrared Phosphor CaY2Mg2Ge3O12:Ce3+/Cr3+ and Its Temperature Sensing.

With the wide application of phosphor conversion light-emitting diode (pc-LED) in nondestructive testing, spectral illumination, near-infrared (NIR) spectroscopy, agricultural medical care, and other fields, the ultrabroadband visible-NIR tunable emission phosphor is considered as the most promising fluorescent material. In this paper, Ce3+/Cr3+ single-doped and codoped CaY2Mg2Ge3O12 phosphors were successfully prepared by using the high-temperature solid-state method. Ce3+ and Cr3+ codoped phosphors show ultrabroadband visible-NIR emission from 480 to 900 nm with two emission peaks at visible 556 nm and infrared 758 nm. Interestingly, energy transfer and occupation competition are shown in the Ce3+/Cr3+ codoped CaY2Mg2Ge3O12. Additionally, the luminescence of Ce3+/Cr3+ codoped CaY2Mg2Ge3O12 is adjusted with the doping ion concentration or ambient temperature changes. The energy transfer mechanism of Ce3+-Cr3+ is studied according to Dexter's formula, and a dipole-dipole interaction is determined. Furthermore, its superior sensitivity with Sr of 1.331%K-1 at 298 K was calculated by using the fluorescence intensity ratio. The pc-LED device was fabricated by combining a commercial 460 nm blue LED chip with CaY2Mg2Ge3O12:Ce3+, Cr3+ phosphors, producing yellow-white light and broadband NIR light, indicating great potential application in night vision pc-LEDs.

Additives Capable of Stably Supplying Anions/Cations for Homogeneous Lithium Deposition/Stripping.

One of the important factors leading to lithium dendrites is a slow lithium-ion mass transport and imbalanced distribution of the Li+ concentration and nuclei sites on the anode surface. To achieve uniform lithium deposition during the charge and discharge process, we introduce a homemade new copolymer (with the quaternary ammonium group N3R+I- on its side chain as the main functional group), named P35, as a functional electrolyte additive to regulate the lithium deposition. Theoretical calculations show that under the strong coordinating interaction between I- and N3R+, P35 preferentially adsorbs onto the lithium foil surface, effectively countering the adsorption of lithium salt anions such as PF6-. Moreover, the positive charge carried by the quaternary ammonium salt group of P35 could interact with PF6- to limit their mobility. Consequently, the dipole interaction on lithium ions is diminished, leading to an enhancement in the transport rate and a decrease in the concentration gradient of lithium ions. Furthermore, a more efficient SEI was formed due to the dual charges electrostatic shield formed by N3R+I-. Li-Li symmetric cells and Li-LiFePO4 full cells assembled with electrolytes with P35 exhibit better rate performance, smaller polarization, and smoother deposition morphology in comparison to the cells without the P35 additive.

Directional Superradiance in a Driven Ultracold Atomic Gas in Free Space

Ultracold atomic systems are among the most promising platforms that have the potential to shed light on the complex behavior of many-body quantum systems. One prominent example is the case of a dense ensemble illuminated by a strong coherent drive while interacting via dipole-dipole interactions. Despite being subjected to intense investigations, this system retains many open questions. A recent experiment carried out in a pencil-shaped geometry [Ferioli Nat. Phys. 19, 1345 (2023)] has reported measurements that have seemed consistent with the emergence of strong collective effects in the form of a “superradiant” phase transition in free space, when looking at the light-emission properties in the forward direction. Motivated by the experimental observations, we carry out a systematic theoretical analysis of the steady-state properties of the system as a function of the driving strength and atom number N. We observe signatures of collective effects in the weak-driving regime, which disappear with increasing drive strength as the system evolves into a single-particle-like mixed state comprised of randomly aligned dipoles. Although the steady state features some similarities to the reported superradiant-to-normal nonequilibrium transition, also known as cooperative resonance fluorescence, we observe significant qualitative and quantitative differences, including a different scaling of the critical drive parameter (from N to N). We validate the applicability of a mean-field treatment to capture the steady-state dynamics under currently accessible conditions. Furthermore, we develop a simple theoretical model that explains the scaling properties by accounting for interaction-induced inhomogeneous effects and spontaneous emission, which are intrinsic features of interacting disordered arrays in free space. Published by the American Physical Society 2024

Aging Treatment to Enhance Coercivity Through Grain Boundary Modification in SmFe10V2 Bulk Magnets

We explored the potential for an aging treatment to achieve high coercivity, of 0.859 MA/m, in a SmFe10V2 alloy with a ThMn12-type structure. Bulk magnets were fabricated by sintering ball-milled powders, followed by aging treatment. XRD and SEM analyses revealed that aging treatment promotes the formation of a Sm-rich grain boundary phase with nano-scale thickness. The high Sm content (~60–80 at.%) and low Fe content (~20–30 at.%) in the grain boundary phase led to non-ferromagnetism, enhancing the coercivity by isolating the 1–12 grains and weakening the dipolar interaction between the grains. The aging temperature and duration were optimized to maximize the Sm-rich phase and minimize the soft magnetic SmFe2 phase. This study provides a new fabrication method for ThMn12-type magnets and investigates the relationship between microstructure and coercivity, offering valuable insights for the future design and development of high-performance SmFe12-based magnets.

Electroless Synthesis of Cobalt Nanowires in Magnetic Field and their Characterization by Resonant Magnetometry Methods

In this paper, a simple and effective low-temperature electroless chemical method that provides the synthesis of cobalt micro- and nanowires due to the processes of self-organization of magnetic cobalt nanoparticles under the influence of a magnetic field, using the technology of chemical synthesis of magnetic nanoparticles and nanowires is proposed. Cobalt nanoparticles have magnetic dipole moments. An external magnetic field forces them to be oriented parallel to it. Dipole-dipole interactions between magnetic nanoparticles lead to attraction between cobalt nanoparticles leading to their self-organization into nanowires, reducing their total energy. The resulting smaller nanoparticles fill the gaps between the ordered nanoparticles, leading to the formation of smooth cobalt nanowires. The magnetic and structural properties of the synthesized and commercial nanowires polarized by a magnetic field in the epoxy matrix were studied using the resonant radio-frequency magnetometry and electron microscopy methods. These methods are of interest for optimizing the coercive force of cobalt nanowires with a view to their possible use in creating permanent magnets that do not use rare earth elements, as well as in information processing devices and sensors.

Effect of scalar condensation on fermionic pole-skipping

In this paper, we investigated the holographic fermionic pole-skipping phenomena for a class of interacting theory in a charged AdS black hole background. We have studied two types of fermion-scalar interactions in the bulk: dipole and Yukawa type interaction. Depending upon the interaction we introduced both real and charged scalar fields. We have particularly analyzed the effect of scalar condensation on the fermionic pole-skipping points and discussed their behaviour near critical temperatures.

Proposal for realization and detection of Kitaev quantum spin liquid with Rydberg atoms

The Kitaev chiral spin liquid has captured widespread interest in recent decades because of its intrinsic non-Abelian excitations, yet the experimental realization is challenging. Here we propose to realize and detect Kitaev chiral spin liquid in a deformed honeycomb array of Rydberg atoms. With a laser-assisted dipole-dipole interaction mechanism which realizes both effective hopping and pairing terms for hard-core bosons, together with van der Waals interactions, we achieve the pure Kitaev model with high precision. The gapped non-Abelian spin liquid phase is then obtained under experimental conditions. Moreover, we propose innovative strategies to probe the chiral Majorana edge modes by light Bragg scattering and by imagining their chiral motion. Our proposed scheme broadens the range of quantum spin models with exotic topological phases that can be realized and detected in atomic systems, and makes an important step toward manipulating non-Abelian anyons. Published by the American Physical Society 2024

Chiral Differentiation of Chiral Lactides and Chiral Diketones on Native and Phenylcarbamoylated Cyclodextrin Chiral Stationary Phases.

Inclusion complexation, hydrogen bonds, π-π interaction, dipole-dipole interaction, and steric hindrance effect all contribute to the enantioseparation ability of cyclodextrin (CD) or CD derivatives. In this work, one native cationic CD chiral stationary phases (SHCDCSP) and four derivatized CD-CSPs, namely, per(4-trifluoromethyl) phenylcarbamoylated-β-CD CSP (SFPhCDCSP), per(4-chloro) phenylcarbamoylated-β-CD CSP (SCPhCDCSP), per(4-bromo) phenylcarbamoylated-β-CD CSP (SBPhCDCSP), and per(4-methyl) phenylcarbamoylated-β-CD CSP (SMPhCDCSP), were prepared via thioether linkage and applied for the enantioseparation of chiral lactides and chiral diketones in both reverse phase(RP) and normal phase (NP) modes. Most of the studied chiral lactides were found to be well resolved (Rs > 1.5) under RP mode, especially Met-Sty-Ibn (compound 11) is observed to display highest resolutions (Rs = 5.09, Rs = 3.17) among all the analytes on the SFPhCDCSP and SMPhCDCSP. In NP mode, SFPhCDCSP showed excellent chiral recognition ability towards chiral lactides. The comparison study of CD-CSPs reveals the structure of CSPs play a significant role on the enantioselectivities.

A self-assembly capsule-like solvation structure electrolyte for lithium metal batteries

The localized high-concentration electrolyte can be achieved by diluting a high-concentration electrolyte with an anti-solvent, which inherits the original solvation structural characteristics and reduces harmful interfacial reactions, resulting in an electrolyte with unique functions suitable for lithium metal batteries. Here, we design a localized high-concentration electrolyte with a capsule-like solvation structure and non-flammable properties to obtain stable-cycle and safe lithium metal batteries. The weak coordination and dipole-dipole interactions of fluorinated ether molecules promote the self-assembly of capsule-like solvated sheaths, encapsulating cations/anions and polar solvent molecules within the solvation sheath, which improves the oxidative stability of the electrolyte system and promotes the reduction of anions. A high-quality solid electrolyte layer was derived at the electrode interfaces, leading to rapid Li+ transport and dendrite-free lithium deposition. Consequently, a Coulombic efficiency of 99.7% is achieved, and the assembled Li||NCM811 battery exhibits a long cycle life of more than 400 cycles at 0.5C with a capacity retention of 83%. This work provides a promising approach for developing non-flammable electrolytes suitable for high-voltage lithium metal batteries.

Molecular structures of residual solvent in polyacrylonitrile based electrolytes: Implications for conductivity and stability.

Lithium-ion batteries increasingly play significant roles in modern technologies; however, increased energy density also raises concerns about electrolyte safety. Traditional electrolytes that use volatile organic solvents face risks of thermal runaways and fires from electrode shorting. In response, polymer-based solid electrolytes have been developed for replacement. Polyacrylonitrile (PAN) is a promising fire-resistant component for electrolyte fabrication, but its limited solubility necessitates using low-volatility solvents, which are notoriously difficult to remove in subsequent drying processes. Here, we use femtosecond two-dimensional infrared spectroscopy to provide an in-depth understanding of how residual solvent from processing affects the molecular structures and dynamics within a polymer electrolyte. To this end, linear and nonlinear infrared spectroscopies are employed to interrogate the molecular interactions in PAN-based electrolytes containing various contents of N,N-dimethylformamide (DMF). We show that the amount of DMF within the PAN electrolyte affects the Li+ structure. The coordination can proceed through the carbonyl group and/or the amide nitrogen to form antiparallel structures with the nitrile groups of PAN through dipole-dipole interactions. The free motion of DMF is drastically inhibited upon interaction with Li+ and PAN, which decreases the ionic conductivity and potentially affects the stability (resistance toward removal and chemical decomposition). These findings have implications for the design and processing of solid polymer electrolytes.

Quantum Otto Heat Engine Using Polar Molecules in Pendular States

Quantum heat engines (QHEs) are established by applying the principles of quantum thermodynamics to small−scale systems, which leverage quantum effects to gain certain advantages. In this study, we investigate the quantum Otto cycle by employing the dipole−dipole coupled polar molecules as the working substance of QHE. Here, the molecules are considered to be trapped within an optical lattice and located in an external electric field. We analyze the work output and the efficiency of the quantum Otto heat engine (QOHE) as a function of various physical parameters, including electric field strength, dipole−dipole interaction and temperatures of heat baths. It is found that by adjusting these physical parameters the performance of the QOHE can be optimized effectively. Moreover, we also examine the influences of the entanglement and relative entropy of coherence for the polar molecules in thermal equilibrium states on the QOHE. Our results demonstrate the potential of polar molecules in achieving QHEs.

Thermodynamics and entropic inference of nanoscale magnetic structures in Gd

A bulk gadolinium (Gd) single crystal exhibits virtually zero remnant magnetization, a common trait among soft uniaxial ferromagnets. This characteristic is reflected in our magnetometry data showing virtually hysteresis free isothermal magnetization loops with large saturation magnetization. The absence of hysteresis allows to model the measured easy axis magnetization as a function of temperature and applied magnetic field, rather than a relation, which permits the application of Maxwell relations from equilibrium thermodynamics. Demagnetization effects broaden the isothermal first-order transition from negative to positive magnetization. By analyzing magnetization data within the coexistence regime, we deduce the isothermal entropy change and the field-induced heat capacity change. Comparing the numerically inferred heat capacity with relaxation calorimetric data confirms the applicability of the Maxwell relation. Analysis of the entropy in the mixed phase region suggests the presence of hitherto unresolved nanoscale magnetic structures in the demagnetized state of Gd. To support this prediction, Monte Carlo simulations of a 3D Ising model with dipolar interactions are performed. Analyzing the cluster size statistics and magnetization from the model provides strong qualitative support of our analytic approach.

Nematic and Smectic Phases with Proper Ferroelectric Order.

A material showing a sequence of three ferroelectric liquid crystalline phases below the paraelectric nematic phase is synthesized and studied. The polar order of molecules appearing due to the dipole-dipole interactions in the ferroelectric nematic, NF, phase is preserved also in the smectic phases: orthogonal SmAF and tilted SmCF. The ferroelectric ground state of both smectic phases is confirmed by their second harmonic generation (SHG)activity and polarization switching. In the SmCF phase the polarization becomes oriented to the electric field by decreasing the tilt angle to zero. Although both smectic phases are ferroelectric in nature, their dielectric response is found to be very different.

Self-Assembled Bent Perylenediimides.

The properties of π-functional materials are predominantly influenced by both their molecular structures and interactions between π-systems. Recent advancements have focused on modifying the geometry or topology of π-molecules from planar to nonplanar conformations to tailor molecular properties. However, the interactions among nonplanar π-molecules remain largely unexplored, likely due to the significant reduction in contact surfaces arising from their curved structures. Herein, we investigated the electro-optical properties and π-stacking behaviors of a series of bent perylenediimides (B-PDIs) with gradual changes in bending angles, achieved by altering the lengths of linear alkyl chains connecting the two nitrogen positions of each PDI. Curvature-dependent self-assembly of these bent PDIs is observed, which is primarily driven by dipole-dipole interactions rather than dispersion forces. More importantly, fine-tuning intermolecular coupling through bending enables excited-state symmetry-breaking charge separation in [n]B-PDIs (n = 16, 12) in the crystalline solid state.

Isobaric vapour-liquid equilibrium studies for binary systems of a green solvent furfuryl alcohol with aniline and substituted anilines at 101.31 kPa

New experimental vapour-liquid equilibrium (VLE) data, which is expected to be useful in industrial processes such as the design of separation processes is reported in the present article. Isobaric VLE data of an eco-sustainable, green solvent furfuryl alcohol (FFA) as a common component has been measured for three binary systems (i) furfuryl alcohol + aniline (AN), (ii) furfuryl alcohol + N-methylaniline (NMA) and (iii) furfuryl alcohol + N-ethylaniline (NEA) in the complete concentration of FFA at a pressure of 101.31 kPa. The Antoine equation has been used to calculate the vapour pressure of pure samples. The reported VLE data is thermodynamically consistent according to the van Ness, Fredenslund and Herington area tests. The experimental observations of the three systems displayed non-ideal nature and negative deviation from Raoult's law. The Wilson and UNIQUAC activity coefficient models have been applied to correlate the experimental data. The information of the boiling point temperature (T), activity coefficients (γi) and variation of excess Gibbs energy (GE) with the concentration of FFA indicated the presence of dipole-dipole interactions and hydrogen bonding between the molecules of FFA and the selected amines.

Microscopic description of the pygmy and giant dipole resonances in even–even nuclei. Application to the isotopes 150,152,154,156,158,160Gd

This paper deals with a microscopic approach for the description of the pygmy dipole resonance (PDR) as well as of the giant dipole resonance (GDR). The formalism is based on a Hamiltonian which is summing a mean field term, the pairing for alike nucleons and the dipole–dipole interaction. Two features are specific for our description: (a) The use of a projected spherical single particle basis and (b) the involved dipole operator is a Schif-like operator including a corrective term which is cubic in the radial coordinate. The dipole strength distribution with energy is plotted for the PDR region, i.e., [0,10] MeV. The dominant transitions have an isovector character for three isotopes and isoscalar for another three. The PDR states carry only 0.4–1.8[Formula: see text] of the total EWSR. The dependence of the dipole strength on nuclear deformation is evidenced. For the whole interval of [0,20] MeV the dipole strength was first folded by Lorentzian of 1[Formula: see text]MeV width and then plotted as function of the QRPA energies. The peaks belonging to each of the two ranges are analyzed in detail and their nature, isovector/isoscalar, was pointed out. The r-cubic term and the nuclear deformation have opposite effects on the dipole strength. The famous Thomas–Reiche–Kuhn sum rule formula is generalized to the case of the Schiff dipole momentum. The new EWSR is very well satisfied. The photoabsorbtion cross-section is calculated and compared with experimental data in a figure showing its dependence on energy. The total cross-section, [Formula: see text], the moments of the integrated cross-sections, [Formula: see text], [Formula: see text], the dipole polarizability and the thickness of the neutron crust are also calculated. The main features of PDR and GDR are realistically described.