Stable Configuration Research Articles

Exploring the Diversity of Nuclear Density through Information Entropy.

This study explores the role of information entropy in understanding nuclear density distributions, including both stable configurations and non-traditional structures such as neutron halos and α-clustering. By quantifying the uncertainty and disorder inherent in nucleon distributions in nuclear many-body systems, information entropy provides a macroscopic measure of the physical properties of the system. A more dispersed and disordered density distribution results in a higher value of information entropy. This intrinsic relationship between information entropy and system complexity allows us to quantify uncertainty and disorder in nuclear structures by analyzing various geometric parameters such as nuclear radius, diffuseness, neutron skin, and cluster structural features.

Multimessenger signals from compact axion star mergers

Axion dark matter can form stable, self-gravitating, and coherent configurations known as axion stars, which are rendered unstable above a critical mass by the Chern-Simons coupling to electromagnetism. We study, using numerical relativity, the merger and subsequent decay of compact axion stars. We show that two subcritical stars can merge, and form a more massive, excited, and critical star, which survives for a finite period before rapidly decaying via electromagnetic radiation. We find a rich multimessenger signal, composed of gravitational waves, electromagnetic radiation, and axion radiation. The gravitational wave signal is broken into two parts: a weak and broad signal from the merger, followed by a much stronger signal of almost fixed frequency from the decay. The electromagnetic radiation follows only the gravitational waves from the decay, while the axion signal is continuous throughout the process. We briefly discuss the detectability of such a signal. Published by the American Physical Society 2024

Design of Thermally Activated Delayed Fluorescence Materials: Transition from Carbonyl to Amide‐Based Acceptor

AbstractBenzophenone skeletons containing a carbonyl unit (O=C) have been widely used as electron acceptors in the thermally activated delayed fluorescence (TADF) materials. Herein, we present a novel molecular design concept for TADF materials by transitioning from a carbonyl to an amide (O=C−N) skeleton as the acceptor. The amide unit, compared to its carbonyl counterpart, offers a more stable electronic configuration. Leveraging this insight, we have developed a series of high‐performance TADF molecules based on benzoyl carbazole and carbazoline acceptors. These molecules exhibit exceptionally small singlet‐triplet energy gaps and pronounced aggregation‐enhanced emission properties, achieving photoluminescence quantum yields in neat films as high as 99 %. Consequently, these materials serve as efficient emitters in non‐doped organic light‐eimtting diodes (OLEDs), reaching a maximum quantum efficiency (EQEmax) of up to 26.0 %, significantly higher than the 17.0 % obtained with benzophenone acceptor‐based TADF molecules. Additionally, they have been used as TADF hosts in narrowband red fluorescent OLEDs, setting a record‐high EQEmax of 22.4 %.

Computational insights into the deoxygenation reaction of biomass-derived phenolic compounds over Ni2P (001) catalysts

This research sets the scene for understanding the interaction of phenolic molecules (i.e., phenol, o-cresol, m-cresol, and p-cresol) with Ni2P catalyst surface and how their hydrodeoxygenation reaction progresses over the surface. The hydrodeoxygenation process is responsible for removing the oxygen content from the pyrolysis oil compounds, particularly through direct deoxygenation route. Ni2P, which is one of the most common transition metal phosphides, serves as a candidate surface of this study. Two main investigations were carried out including the optimization of (1) adsorption configuration of the phenolic compounds and the (2) net charge distribution between the surface and the adsorbate. According to the adsorption energy studies, the horizontal configuration of the o-cresol molecule on the Ni2P(001) hollow site presented the most optimized and stable configuration with the least negative adsorption energy (−0.26 eV), resulting in the most negative net charge density at −0.286 |e|, as determined by the Bader charge analysis. Upon adsorption on Ni2P(001) surface, o-cresol undergoes significant charge redistribution, where the oxygen atom (-OH group) exhibits a net charge of −1.3443 |e|, indicating electron transfer to the surface. The catalytic pathway proceeded with deoxygenation followed by ring hydrogenation to produce toluene (C7H8), such that C–O bond dissociation has a reaction energy of −0.715 eV, while C–H bond formation step had a reaction energy of 0.011 eV.

Design of Thermally Activated Delayed Fluorescence Materials: Transition from Carbonyl to Amide-Based Acceptor.

Benzophenone skeletons containing a carbonyl unit (O=C) have been widely used as electron acceptors in the thermally activated delayed fluorescence (TADF) materials. Herein, we present a novel molecular design concept for TADF materials by transitioning from a carbonyl to an amide (O=C-N) skeleton as the acceptor. The amide unit, compared to its carbonyl counterpart, offers a more stable electronic configuration. Leveraging this insight, we have developed a series of high-performance TADF molecules based on benzoyl carbazole and carbazoline acceptors. These molecules exhibit exceptionally small singlet-triplet energy gaps and pronounced aggregation-enhanced emission properties, achieving photoluminescence quantum yields in neat films as high as 99 %. Consequently, these materials serve as efficient emitters in non-doped organic light-eimtting diodes (OLEDs), reaching a maximum quantum efficiency (EQEmax) of up to 26.0 %, significantly higher than the 17.0 % obtained with benzophenone acceptor-based TADF molecules. Additionally, they have been used as TADF hosts in narrowband red fluorescent OLEDs, setting a record-high EQEmax of 22.4 %.

Oxygen-close-packed (310)-plane substrates of β-Ga2O3 grown by the casting method

The highly anisotropic crystal structure of β-Ga2O3 gives rise to a variety of crystal planes, among which the (310) plane is a potentially stable close-packed plane for the O sublattice. In this paper, we report the β-Ga2O3 single crystal and substrates with a (310) major plane grown by the spontaneous nucleation technique in the casting method. High-quality crystal growth and substrate processing were confirmed by the 25.67 arc sec full width at half maximum and the 0.25 nm surface roughness. The nanoindentation experiments revealed the (310) substrate's better elastic recovery than that of (100) substrate. The Young's modulus and hardness of (310) substrates were 200 and 7.6 GPa, respectively. The surface barrier height and the Schottky barrier height were 1.25 and 0.92 eV, respectively. First principles calculations identified the (310)-Ga-I plane as the most stable surface configuration of the (310) plane under oxygen-poor condition, with a surface energy density of 1.48 J/m2. The (310) twin boundary formation around the O sublattice has a high energy density of 0.55 J/m2, suggesting its unlikelihood of spontaneous formation. These properties of (310) plane facilitate a high-quality crystal processing and epitaxial growth, thus endowing potential applications in high-quality power devices. Furthermore, the growth and fabrication of the (310) plane provide a route toward understanding the properties of β-Ga2O3 and advancing the growth techniques of oxide crystals.

Morphing Spoiler for Adaptive Aerodynamics by Shape Memory Alloys

The automotive industry is continuously looking for innovative solutions to improve vehicle aerodynamics and efficiency. The research introduces a significant breakthrough in the field of automotive aerodynamics by employing shape memory alloys as bistable actuators for spoilers and moving flaps. The main novelty of this research lies in the development of a bistable actuator made of shape memory alloys as a precise and accurate control mechanism for spoilers and movable flaps. The shape memory alloys, with their unique ability to maintain two stable configurations and switch rapidly from one to the other in response to thermal or mechanical stimuli, allow precise and rapid adjustment of aerodynamic surfaces. The main advantage of this technology is its ability to improve vehicle aerodynamics by optimising both drag and downforce, thereby improving vehicle performance and fuel efficiency. This research shows the promising potential of a single composition of NiTi as a revolutionary technology in the automotive industry, revolutionising the way spoilers and moving flaps are used to achieve superior vehicle performance.

Adaptive-Quadratic-Neural-Network-Based Multifidelity Modeling Approach for Buckling of Stiffened Panels

This paper presents a method for predicting the buckling load of stiffened panels using multifidelity modeling based on quadratic neural networks (QNNs) with adaptive activation functions. The effectiveness of the proposed approach is demonstrated through a series of simulations on a range of stiffened panel configurations, and the results are compared to those obtained from traditional multifidelity and high-fidelity models in terms of accuracy and computational efficiency. Numerical experiments demonstrate that the model can accurately and efficiently predict the buckling load of stiffened panels while significantly reducing the computational cost of evaluating the surrogate model. In particular, the proposed adaptive quadratic neural networks (AQNNs) model achieves convergence approximately three times faster and four times less trainable parameters compared to traditional artificial neural networks while maintaining the same validation loss. This approach can significantly improve the design and optimization of aerospace structures by easily and quickly exploring various design configurations and finding stable and efficient configurations. This study highlights the potential of a new multifidelity modeling framework for predicting the buckling load and collapse load of aerospace structures by enhancing convergence speed and prediction accuracy while reducing the computational complexity of neural networks.

Fuel-optimal acquisition and control of a cartwheel formation in Earth displaced heliocentric orbit

An optimization approach for cartwheel formation acquisition and maintenance in an Earth Displaced heliocentric orbit is presented. This work considers non-gravitational perturbations such as solar radiation pressure, thus extending the studies previously performed for the mission LISA. The problem is tackled as a Nonlinear Programming problem using a multiple shooting method. The optimization process is performed in two steps: first, the orbital elements of each satellite in heliocentric orbit are optimized to guarantee the stability during the science phase hence easing maintenance of the cartwheel formation in presence of orbital perturbations. Then, the obtained initial states are propagated to obtain a set of target orbital states which become the final target of a second optimization covering the transfer phase from Earth. For the science phase optimization presents two alternative cost functions are introduced, one based on the arm-length evolution and one on the arm-length-rate evolution. The performance of each cost function is analysed for different initial displacement angles: for target arm-lengths below 2.5 million kilometers the arm-length cost function provides the best results while no significant difference between the two optimized solutions is observed above this value. The transfer phase optimization presents two different approaches, one considering an injection on a trajectory more favourable for one of the three spacecraft and one considering an injection on an intermediate trajectory which minimizes the overall acquisition cost of all spacecraft. The proposed optimization approach performance are studied on a set of test cases covering both transfer and science phase, showing that stable configuration conditions can be found even in presence of orbital perturbations and that the multiple injection transfer is capable of providing a more homogeneous fuel consumption among the three spacecraft.

Local gravitational instability of two-component thick discs in three dimensions

Aims. The local gravitational instability of rotating discs is believed to be an important mechanism in different astrophysical processes, including the formation of gas and stellar clumps in galaxies. We aim to study the local gravitational instability of two-component thick discs in three dimensions. Methods. We use as a starting point a recently proposed analytic three-dimensional (3D) instability criterion for discs with non-negligible thickness that takes the form Q3D < 1, where Q3D is a 3D version of the classical 2D Toomre Q parameter for razor-thin discs. Here, we extend the 3D stability analysis to two-component discs, considering first the influence on Q3D of a second unresponsive component, and then the case in which both components are responsive. We present the application to two-component discs with isothermal vertical distributions, which can represent, for instance, galactic discs with both stellar and gaseous components. Finally, we relax the assumption of vertical isothermal distribution, by studying one-component self-gravitating discs with polytropic vertical distributions for a range of values of the polytropic index corresponding to convectively stable configurations. Results. We find that Q3D < 1, where Q3D can be computed from observationally inferred quantities, is a robust indicator of local gravitational instability, depending only weakly on the presence of a second component and on the vertical gradient of temperature or velocity dispersion. We derive a sufficient condition for local gravitational instability in the midplane of two-component discs, which can be employed when both components have Q3D > 1.

Manipulating the electronic and spintronic properties in PtS2/MoTe2 heterostructure with strain

In this work, the strain engineering on the electronic and spintronic properties of PtS2/MoTe2 heterostructure is investigated by first-principle calculations. Based on the energy minimum principle, the most stable configuration of the PtS2/MoTe2 heterostructure is recognized. The mechanisms for the evolution of the band structures under different strains are analyzed by the atomic orbital projected band structures. Furthermore, a Rashba type spin texture of PtS2/MoTe2 heterostructure is predicted, with a formation mechanism revealed through atomic orbital projected spin textures. The strain tunable electronic and spintronic properties of PtS2/MoTe2 heterostructure hold great promise in applications of spintronics and nanoelectronics.

Synthesis, spectroscopic characterization, electronic elucidation, chemical reactivity, topological and molecular docking investigations of cefadroxil sulfoxide

The cefadroxil sulfoxide (CDSO) para-hydroxy derivative, derived from cefadroxil, has enormous significance in pharmaceutical applications. The cefadroxil sulfoxide (CDSO) compound was synthesized and characterized by spectroscopic (FT-IR, FT-Raman, and UV–Visible) assessments. Computational investigations have been carried out concurrently with a B3LYP-6-311++G(d,p) basis set and density functional theory (DFT). The molecular vibrational assignments, chemical reactivity, electronic properties, and optical activities are calculated using gas and different solvent phases. The stable ground state configuration of the given molecular compound is investigated using PES analysis. Furthermore, the chemical behavior of the CDSO was thoroughly investigated for different solvent aspects through HOMO-LUMO, MEP, UV–Visible and electron-hole excitation analyses. The molecular occupancy, virtual occupancy, and overlapping bonding energies are investigated by TDOS, PDOS, and COOP spectrum studies. Fukui function and dual descriptor investigations extend to the chemical reactivity of individual atomic sites. The intra-molecular analysis provided a deeper understanding of the molecular interactions performed by natural bond orbitals (NBO) and non-linear optics (NLO), which provided optical activity for the title compound. Additionally, electron localization function (ELF), localized orbital locator (LOL), and reduced density gradient (RDG) analyses were also accomplished to provide insight into the delocalized orbitals in the header composite. The molecular docking was achieved, and the ligand with 4EVM protein is providing the potential antimicrobial biological activity (binding energy −7.12 kcal/mol) of the CDSO compound.

Oppositions, joints, and targets: the attractors that are the glue of social interactions.

Social interactions are often analyzed by scoring segments of predefined behavior and then statistically assessing numerical and sequential patterns to identify the structure of the encounters. However, this approach can miss the dynamics of the animals' relationship over the course of the encounter, one that often involves invariant bonds, say a nose-to-nose orientation, with many different movements performed by both partners acting to counteract each other's attempts to break or maintain the relationship. Moreover, these invariant bonds can switch from one configuration to another during an interaction, leading from one stable configuration to another. It is this stepwise sequence of configurational stabilities that lead to functional outcomes, such as mating, aggression, or predation. By focusing on the sequence of invariant relational configurations, the deep structure of interactions can be discerned. This deep structure can then be used to differentiate between compensatory movements, no matter how seemingly stereotyped they may appear, from movement patterns which are restricted to a particular form when more than one option is available. A dynamic perspective requires suitable tools for analysis, and such tools are highlighted as needed in describing particular interactions.

Structural balance in real-world social networks: incorporating direction and transitivity in measuring partial balance

Structural balance theory predicts that triads in networks gravitate towards stable configurations. This theory has been verified for undirected graphs. Since real-world networks are often directed, we introduce a novel method for considering both transitivity and sign consistency for evaluating partial balance in signed digraphs. We test our approach on graphs constructed by using different methods for identifying edge signs: natural language processing to infer signs from underlying text data, and self-reported survey data. Our results show that for various social contexts and edge sign detection methods, partial balance of these digraphs is moderately high, ranging from 61 to 96%. Our approach not only enhances the theoretical framework of structural balance but also provides practical insights into the stability of social networks, enabling a deeper understanding of interpersonal and group dynamics across different communication platforms.

Theoretical Study on the Electrocatalytic CO2 Reduction Mechanism of Single-Atom Co Complexed Carbon-Based (Co-Nχ@C) Catalysts Supported on Carbon Nanotubes.

Electrocatalytic CO2 reduction serves as an effective strategy to tackle energy crises and mitigate greenhouse gas effects. The development of efficient and cost-effective electrocatalysts has been a research hotspot in the field. In this study, we designed four Co-doped single-atom catalysts (Co-Nχ@C) using carbon nanotubes as carriers, these catalysts included tri- and dicoordinated N-doped carbon nanoribbons, as well as tri- and dicoordinated N-doped graphene, respectively denoted as H3(H2)-Co/CNT and 3(2)-Co/CNT. The stable configurations of these Co-Nχ@C catalysts were optimized using the PBE+D3 method. Additionally, we explored the reaction mechanisms of these catalysts for the electrocatalytic reduction of CO2 into four C1 products, including CO, HCOOH, CH3OH and CH4, in detail. Upon comparing the limiting potentials (UL) across the Co-Nχ@C catalysts, the activity sequence for the electrocatalytic reduction of CO2 was H2-Co/CNT > 3-Co/CNT > H3-Co/CNT > 2-Co/CNT. Meanwhile, our investigation of the hydrogen evolution reaction (HER) with four catalysts elucidated the influence of acidic conditions on the electrocatalytic CO2 reduction process. Specifically, controlling the acidity of the solution was crucial when using the H3-Co/CNT and H2-Co/CNT catalysts, while the 3-Co/CNT and 2-Co/CNT catalysts were almost unaffected by the solution's acidity. We hope that our research will provide a theoretical foundation for designing more effective CO2 reduction electrocatalysts.

Exploring effects of reactant’s chemical environments on adsorption and reaction mechanism by global optimization and IR spectrum calculation, using NO oxidation as a case

Reactant’s chemical environments derived from the type and concentration of surface species on heterogeneous catalysts do great effects on the structures of reactants and reaction pathway. Unraveling the arrangement of surface species and reaction mechanism at different reactant’s chemical environments in theory remains a substantial challenge due to the difficulty in obtaining the global stable configuration of surface species on catalysts and the lack of other theoretical evidences for the identification of surface species and reaction pathway. To solve this problem, a protocol combining the global optimization of surface species at different chemical environments with electronic structure analysis and IR spectrum calculation including frequency and intensity was proposed to unravel the arrangement of surface species and their reaction pathway in this work. Using NO adsorption and oxidation on Pt(111) and O-covered Pt(111) as a case, their stable structures were obtained by the global optimization; then the origins of the structural transformation of NO and NO2 at different environments were elucidated by electronic structure analysis; then the structures and reaction pathway were confirmed by comparing the experimental and calculated IR spectra of NO and NO2 with frequency and intensity. Utilizing this protocol, the stable structures of NO and its transformation, as well as oxidation pathway were revealed under varying chemical environments at the molecular level. It provides solid supports for identifying the stable arrangement of surface species, their transformation and reaction pathway, and can be easily extended to heterogeneous catalysis.

Impact of cold dark matter and variable equations of state on the stability of thin-shell wormholes

The goal of this research is to better understand how two identical black hole copies, bounded by a cold dark matter halo, produce and stabilize thin-shell wormholes. The occurrence of a cold dark matter halo is discovered to increase the black hole’s horizon radius. Investigating the stable geometry of these wormholes by linearized radial perturbation analysis is the main objective of the work. It is noteworthy that the development of thin-shell wormholes with reduced energy limitations is associated with the presence of a cold dark matter halo. We study how the stability of the wormholes is affected by variable equations of state, including phantom-like, variable Chaplygin, and barotropic equations of state. The question emphasizes how crucial the existence of a cold dark matter halo is to preserving stable thin-shell wormhole configurations. The findings shed light on the interactions between a cold dark matter halo and wormholes, which improved our knowledge of both phenomena and their possible consequences for extraterrestrial travel.

Optical response of Zr[formula omitted]CO[formula omitted]/MoS[formula omitted] van der Waals heterostructures calculated using first-principles calculations

In the field of material science, the search for a material with an optimal bandgap of approximately 1.40 eV that can act as an efficient photocatalyst for water splitting using solar spectrum irradiation is a noble mission. In this article, we explore the structural, electronic structure, optical and photocatalytic properties of Zr2CO2/MoS2 vdW heterostructures. Our results demonstrates that the Zr2CO2/MoS2 vdW heterostructure can be reliably synthesized. This is due to a minimal lattice mismatch of less than 3%, a negative adhesion energy of -4.23 meV/Å 2, and inherent dynamic stability. The electronic band structure calculations indicate that the Zr2CO2/MoS2 vdW heterostructure is an indirect bandgap semiconductor. We found that the conduction band minimum (CBM) and valance band maximum (VBM) of the heterostructure are located in different monolayers. Furthermore, under −2% biaxial strain a transition from type-I to type-II (staggered) band alignment occurred. Stacking 2D MoS2 on the Zr2CO2 monolayer results in a vdW heterostructure, and as a result, the HSE calculated bandgap of the Zr2CO2/MoS2 vdW heterostructure in most stable configuration lying in the ideal range for photocatalytic applications. We also studied the heterostructure’s optical properties to understand its response to incident photons with energies up to 14 eV. Based on our findings, Zr2CO2/MoS2 heterostructures are desirable for optoelectronic device applications operated in visible range. Our research offers fresh recommendations for developing novel, highly effective photocatalytic compounds with numerous optical device applications.

A DFT study of eugenol adsorption onto pure and Si-doped Al12N12 and B12N12 fullerene-like nanocages

Density functional theory (DFT) methods have been employed in this work to study the adsorption behavior of eugenol (Eug) on the external surface of pure and Si-doped Al12N12 and B12N12 fullerene-like nanocages. All calculations were performed using the M062X-D3 functional combined with the 6-311 + G(d,p) basic sets. In order to probe the reliability of the DFT method, three other functionals (B3LYP-D3, CB3LYP-D3 and WB97XD) were employed and no significant difference was observed in the adsorption energy values of the most stable configurations (AEII and BEII). Also, the complexes are found to be stable in standard conditions in gas and aqueous phases, and the adsorption process is found to be exothermic and spontaneous. Interestingly, Si-doped nanomaterials (Si-AEII and Si-BEII) form the most stable adsorbent-adsorate molecular states (Eads = −90.07 and −61.42 kcal/mol respectively) in gas phase. Furthermore, Si-AEII and Si-BEII complexes exhibit the highest reactivity, characterized by the lowest values of the HOMO-LUMO energy gap (5.50 and 7.07 eV respectively). MEP map of the studied systems showed electron rich and electron deficient sites. Natural bond orbital analyses revealed that the interaction of Al12N12 with Eug is mainly due to the strong electron delocalization LP(2)O10 → LP*(2)Al47 (E(2) = 34 kcal/mol), whereas in Eug-B12N12 complex, it is mainly due to the electron delocalization LP(2)O10 → P*(4)B36 (E(2) = 96.53 kcal/mol). The QTAIM analysis revealed that Si–O and Al–C/B–C bonds linking eugenol to doped cages are attractive weak interactions and their nature have been confirmed via RDG/NCI analyses. Indeed, the present study revealed the suitability of Si-doped Al12N12 and B12N12 fullerene-like nanocages for the efficient drug delivery of eugenol.

Induced Manipulation of Atomically Dispersed Cobalt through S Vacancy for Photocatalytic Water Splitting: Asymmetric Coordination and Dynamic Evolution.

It is still a challenge to construct single-atom level reduction and oxidation sites in single-component photocatalyst by manipulating coordination configuration for photocatalytic water splitting. Herein, the atomically dispersed asymmetric configuration of six-coordinated Co-S2O4 (two exposed S atoms, two OH groups, and two Co─O─Zn bonds) suspending on ZnIn2S4 nanosheets verified by combining experimental analysis with theoretical calculation, is applied into photocatalytic water splitting. The Co-S2O4 site immobilized by Vs acts as oxidation sites to guide electrons transferring to neighboring independent S atom, achieving efficient separation of reduction and oxidation sites. It is worth mentioning that stabilized Co-S2O4 configuration show dynamic structure evolution to highly active Co-S1O4 configuration (one exposed S atom, one OH group, and three Co─O─Zn bonds) in reaction, which lowers energy barrier of transition state for H2O activization. Ultimately, the optimized photocatalyst exhibits excellent photocatalytic activity for water splitting (H2: 80.13 µmol g-1 h-1, O2: 37.81 µmol g-1 h-1) and outstanding stability than that of multicomponent photocatalysts due to dynamic and reversible evolution between stable Co-S2O4 configuration and active Co-S1O4 configuration. This work demonstrates new cognitions on immobilized strategy through vacancy inducing, manipulating coordination configuration, and dynamic evolution mechanism of single-atom level catalytic site in photocatalytic water splitting.