Atomic Level Research Articles

Fluorescence resonance energy transfer in atomically precise metal nanoclusters by cocrystallization-induced spatial confinement

Understanding the fluorescence resonance energy transfer (FRET) of metal nanoparticles at the atomic level has long been a challenge due to the lack of accurate systems with definite distance and orientation of molecules. Here we present the realization of achieving FRET between two atomically precise copper nanoclusters through cocrystallization-induced spatial confinement. In this study, we demonstrate the establishment of FRET in a cocrystallized Cu8(p-MBT)8(PPh3)4@Cu10(p-MBT)10(PPh3)4 system by exploiting the overlapping spectra between the excitation of the Cu10(p-MBT)10(PPh3)4 cluster and the emission of the Cu8(p-MBT)8(PPh3)4 cluster, combined with accurate control over the confined space between the two nanoclusters. Density functional theory is employed to provide deeper insights into the role of the distance and dipole orientations of molecules to illustrate the FRET procedure between two cluster molecules at the electronic structure level.

On the wavefunction cutoff factors of atomic hydrogen confined by an impenetrable spherical cavity

AbstractThe Schrödinger equation for the hydrogen atom enclosed by an impenetrable spherical cavity is solved through a Finite‐Differences approach to gain an insight on the actual nature and structure of the ansatz wavefunction cutoff factor widely used in an ad hoc manner in corresponding variational calculations to comply with the Dirichlet boundary conditions. The results of this work provide a theoretical foundation for the choice of the appropriate analytical cutoff functions that fulfill the boundary conditions. We find three different regions for the behavior of the cutoff functions. Small cavity radius where the cutoff function has a parabolic behavior, an intermediate region where the cutoff function is quasi‐linear, and a large cavity region where the cutoff function is a step‐like function. We deduce the traditional linear and quadratic cutoff functions used in the literature as well as its validity region for the confining radius. Finally, we provide a mathematical deduction of the exact cutoff function in terms of the nodal structure of the free hydrogenic wavefunctions and a relation to the Laguerre polynomials for some cavity radii where the free atomic energy level coincides with a confined energy level. We find that the cutoff function transit over several unconfined solutions in terms of its nodal structure as the system is compressed.

Fabrication and luminous properties of BaAl2O4-LuAG:Ce composite phosphor ceramics for solid-state laser lighting

Based on the “effective ionic radius match effect” and the “charge balance substitution rule of ions”, mixed Ba2+, Al3+, Lu3+, and Ce3+ ions can be effectively regulated to a BaAl2O4-LuAG:Ce biphasic structure. The contribution of BaAl2O4 like as scattering centers can reduce overall reflection losses and enhance the light extraction efficiency of these composite phosphor ceramics (CPCs). In this work, a series of x wt.% BaAl2O4-LuAG:Ce (x = 0, 3, 5, 10, 15) CPCs were fabricated by vacuum sintering using co-precipitated composite powders. Homogenization at the atomic level of mixed Ba3+, Al3+, Lu3+, and Ce3+ ions in multiphase powders provides uniform distribution of BaAl2O4 and LuAG:Ce constituent phases in composite ceramics. The introduction of BaAl2O4 has an additive effect, which also consists in uniform aggregation of pores near their grains during sintering. It allows to adjust the size and amount of microstructural defects by varying the secondary phase content. Under the excitation of 10.8 W 450 nm LDs in a reflection mode, 3 wt% BaAl2O4-based CPCs show the optimum luminous flux of 2244 lm and a luminous efficiency of 208 lm·W−1. The obtained CPCs show a high application potential in solid-state laser lighting.

Spectral analysis of three hot subdwarf stars: EC 11481-2303, Feige 110, and PG 0909+276: A critical oscillator-strength evaluation for iron-group elements

For the precise spectral analysis of hot stars, advanced stellar-atmosphere models that consider deviations from the local thermodynamic equilibrium are mandatory. This requires accurate atomic data to calculate all transition rates and occupation numbers for atomic levels in the considered model atoms, not only for a few prominent lines exhibited in an observation. The critical evaluation of atomic data is a challenge because it requires precise laboratory measurements. Ultraviolet spectroscopy of hot stars with high resolving power provide such ``laboratory'' spectra. We compare observed, isolated lines of the iron group (here calcium to nickel) with our synthetic line profiles to judge the accuracy of the respective oscillator strengths. This will verify them or yield individual correction values to improve the spectral analysis, that is the determination of, for example, effective temperature ( and abundances. To minimize the error propagation from uncertainties in surface gravity ($g$), and abundance determination, we start with a precise reanalysis of three hot subdwarf stars, namely and Then, we measure the abundances of the iron-group elements individually. Based on identified, isolated lines of these elements, we compare observation and models to measure their deviation in strength (equivalent width). For and we confirmed the previously determined and values within their error limits. For all three stars, we fine-tuned all metal abundances to achieve the best reproduction of the observation. For more than 450 isolated absorption lines of the iron group, we compared modeled and observed line strengths. Considering the uncertainty of the analysis and evaluation procedure, an upper limit for the uncertainty of the underlying atomic data was established. We selected strong, reliable isolated absorption lines, which we recommend to use as reference lines for abundance determinations in related objects.

Unraveling the molecular mechanism of novel leukemia mutations on NTRK2 (A203T & R458G) and NTRK3 (E176D & L449F) genes using molecular dynamics simulations approach

Background: NTRK1, NTRK2, and NTRK3 are members of the neurotrophic receptor tyrosine kinases (NTRK) family, which encode TrkA, TrkB, and TrkC receptors, respectively. Hematologic cancers are also linked to point mutations in the NTRK gene's kinase domain. Trk fusions are the most common genetic change associated with oncogenic activity in Trk-driven liquid tumors. Thus, point mutations in NTRK genes may also play a role in tumorigenesis. The structural and functional effect of mutations in Trk-B & Trk-C proteins remains unclear. Methods: In this research, Homology (threading-based approach) modeling and the all-atom molecular dynamics simulations approaches are applied to examine the structural and functional behavior of native and mutant Trk-B and Trk-C proteins at the molecular level. Results: The result of this study reveals how the mutations in Trk-B (A203T & R458G) and Trk-C (E176D & L449F) proteins lost their stability and native conformations. The Trk-B mutant A203T became more flexible than the native protein, whereas the R458G mutation became more rigid than the native conformation of the Trk-B protein. Also, the Trk-C mutations (E176D & L449F) become more rigid compared to the native structure. Conclusions: This structural transition may interrupt the function of Trk-B and Trk-C proteins. Observing the impact of NTRK-2/3 gene alterations at the atomic level could aid in discovering a viable treatment for Trk-related leukemias.

Multi-layers hexagonal hole MXene trap constructed by carbon vacancy defect regulation strategy enables high energy density potassium-ions storage

Due to the slow reaction kinetics of potassium-ions with large size radius in layered materials, the energy density of aqueous potassium-ion hybrid supercapacitors (PIHCs) is severely limited. At the same time, the treatment of defects is a “double-edged sword” in energy storage materials, which requires targeted and precise regulation. In order to solve this problem, multi-layers hexagonal hole MXene trap was constructed by using the carbon vacancy defect regulation strategy, and high specific capacitance and energy density potassium-ion storage was realised in PIHCs. The structure-activity relationship at the atomic level was elucidated in combination with the pseudo-capacitance effect caused by the change of valency of newly exposed titanium atoms in the inner wall of the hexagonal hole MXene trap. By density functional theory, the adsorption energy and kinetic analysis of multi-layers hexagonal hole MXene for potassium-ions were calculated, and the optimal position and quantity of potassium-ions were determined. By quantitative analysis of electron band structure and differential charge density, the internal mechanism of high conductivity and energy density of multi-layers hexagonal hole MXene PIHCs was revealed.

Unraveling the corrosion inhibition behavior of prinivil drug on mild steel in 1M HCl corrosive solution: insights from density functional theory, molecular dynamics, and experimental approaches

Unraveling the corrosion inhibition behavior of prinivil drug on mild steel in 1M HCl corrosive solution: insights from density functional theory, molecular dynamics, and experimental approaches

In vitro blood sample assessment: investigating correlation of laboratory hemoglobin and spectral properties of dual-energy CT measurements (ρ/Z)

Abstract Objectives Our study comprised a single-center retrospective in vitro correlation between spectral properties, namely ρ/Z values, derived from scanning blood samples using dual-energy computed tomography (DECT) with the corresponding laboratory hemoglobin/hematocrit (Hb/Hct) levels and assessed the potential in anemia-detection. Methods DECT of 813 patient blood samples from 465 women and 348 men was conducted using a standardized scan protocol. Electron density relative to water (ρ or rho), effective atomic number (Zeff), and CT attenuation (Hounsfield unit) were measured. Results Positive correlation with the Hb/Hct was shown for ρ (r-values 0.37–0.49) and attenuation (r-values 0.59–0.83) while no correlation was observed for Zeff (r-values −0.04 to 0.08). Significant differences in attenuation and ρ values were detected for blood samples with and without anemia in both genders (p value < 0.001) with area under the curve ranging from 0.7 to 0.95. Depending on the respective CT parameters, various cutoff values for CT-based anemia detection could be determined. Conclusion In summary, our study investigated the correlation between DECT measurements and Hb/Hct levels, emphasizing novel aspects of ρ and Zeff values. Assuming that quantitative changes in the number of hemoglobin proteins might alter the mean Zeff values, the results of our study show that there is no measurable correlation on the atomic level using DECT. We established a positive in vitro correlation between Hb/Hct values and ρ. Nevertheless, attenuation emerged as the most strongly correlated parameter with identifiable cutoff values, highlighting its preference for CT-based anemia detection. Clinical relevance statement By scanning multiple blood samples with dual-energy CT scans and comparing the measurements with standard laboratory blood tests, we were able to underscore the potential of CT-based anemia detection and its advantages in clinical practice. Key Points Prior in vivo studies have found a correlation between aortic blood pool and measured hemoglobin and hematocrit. Hemoglobin and hematocrit correlated with electron density relative to water and attenuation but not Zeff. Dual-energy CT has the potential for additional clinical benefits, such as CT-based anemia detection. Graphical Abstract

The Future of Protection: Unleashing the Power of Nanotech against Corrosion

Corrosion and nanomaterials application gives a complete understanding of corrosion, a pervasive and costly problem that affects a variety of industries worldwide. This study investigates the negative effects of corrosion on infrastructure, safety, and product durability by examining its natural processes and various forms. Regardless of their relative effectiveness, intrinsic restrictions typically limit conventional corrosion control techniques. This article aims to investigate the topic of nanomaterials, which are rapidly emerging and have the potential to significantly reduce corrosion. This abstract delves into the fascinating world of nanomaterials, which range in size from 1 to 100 nanometres, and explores their remarkable powers. Nanomaterials offer substantial advancements in corrosion management, such as better coatings, self-healing mechanisms, and even "smart" coatings with sensing capabilities. The article focuses on the potential benefits of employing nanoparticles for corrosion management, drawing on recent research and imaginative applications. Nanotechnology enables the creation of novel solutions like superior barriers, increased durability, self-repairing capabilities, and targeted corrosion avoidance. However, hurdles remain as the abstract investigates the complexities of manufacturing costs, uncertainty about long-term efficiency, potential environmental effects, and scalability problems associated with adding nanomaterials to corrosion control systems. Understanding corrosion and nanomaterial applications provides essential insights into the fundamental mechanics of corrosion, as well as the significant impact of nanotechnology. This abstract aims to encourage academics, engineers, and policymakers to use nanomaterials to address the ongoing problem of corrosion. Its goal is to promote the use of nanomaterials in diverse industries by giving interdisciplinary insights and forward-thinking ideas that improve durability, safety, and sustainability. Corrosion, a relentless degrader of infrastructure and industrial assets, necessitates novel approaches to mitigate its negative impacts. Nanotechnology has lately emerged as a promising frontier in corrosion mitigation, presenting unrivalled opportunities for improved protection and a longer service life. This paper examines the current state of nanotechnology-based corrosion protection, discusses key obstacles and prospects, and makes recommendations for future advances. Nanotechnology's ability to manipulate materials at the atomic and molecular level has transformed the field of corrosion protection. Nanomaterials, which include nanoparticles, nanocomposites, and nanocoatings, have distinct features that make them particularly effective in inhibiting corrosion start-up and propagation. Nanotech-based solutions outperform conventional coatings in terms of adhesion, barrier characteristics, and chemical resistance, thanks to precise engineering and surface modification approaches. Despite tremendous advancements, broad implementation of nanotechnology-based corrosion prevention confronts challenges. Standardisation and regulation are critical for ensuring the safety, reliability, and environmental sustainability of nanomaterials and coatings. Academics, industry, and regulating authorities must work together to provide comprehensive criteria for material synthesis, characterization, and application. Initiatives that promote education and awareness are critical for accelerating the use of nanotechnology in corrosion protection. Training programmes and knowledge-sharing platforms can provide engineers and industry experts with the necessary skills and competence to properly implement nanotech-based solutions. Public communication efforts emphasizing the benefits of nanotechnology in maintaining infrastructure integrity can garner support from stakeholders and governments. The future possibilities for nanotech-based corrosion prevention are very promising. Advances in nanomaterial production techniques provide unparalleled control over material properties, paving the way for the creation of tailored coatings with superior performance characteristics. Integration with other emerging technologies, like artificial intelligence and the Internet of Things (IoT), has the potential to improve corrosion monitoring and management approaches. Furthermore, the creation of self-healing nanoparticles constitutes a significant advancement in corrosion protection. Inspired by biological systems, self-healing nanocomposites can repair corrosion-induced damage on their own, prolonging the service life of infrastructure assets and lowering lifecycle costs. Continued investment in research and development is crucial to realising nanotechnology's full promise for corrosion protection and ushering in a new era of resilience and dependability. Nanotechnology provides transformative corrosion control solutions that have the potential to revolutionise a variety of industrial sectors. By addressing important obstacles and capitalising on emerging opportunities, we can use nanotechnology to protect infrastructure, conserve resources, and assure long-term growth for future generations.

Modelling Photocatalytic N2 Reduction to Ammonia: Where We Stand and Where We Are Going.

Artificial ammonia synthesis via the Haber-Bosch process is environmentally problematic due to the high energy consumption and corresponding CO emissions, produced during the reaction and before hand in hydrogen production upon methane steam reforming. Photocatalytic nitrogen fixation as a greener alternative to the conventional Haber-Bosch process enables us to perform nitrogen reduction reaction (NRR) under mild conditions, harnessing light as the energy source. Herein, we systematically review first-principles calculations used to determine the electronic/optical properties of photocatalysts, N2 adsorption and to expound possible NRR mechanisms. The most commonly studied photocatalysts for nitrogen fixation are usually modified with dopants, defects, co-catalysts and Z-scheme heterojunctions to prevent charge carrier recombination, improve charge separation efficiency and adjust a band gap to for utilizing a broader light spectrum. Most studies at the atomistic level of modeling are grounded upon density functional theory (DFT) calculations, wholly foregoing excitation effects paramount in photocatalysis. Hence, there is a dire need to consider methods beyond DFT to study the excited state properties more accurately. Furthermore, a few studies have been examined, which include higher level kinetics and macroscale simulations. Ultimately, we show there is still ample room for improvement with regard to first principles calculations and their integration in multiscale models.

Single−atom Co anchored on covalent organic framework for remarkable photocatalytic hydrogen evolution efficiency

Single-atom catalysts (SACs) have attracted extensive attention because of their high atomic utilization and superior catalytic activity. Herein, single-atom Co has anchored on the β-ketoenamine-linked covalent organic framework (Tp-Tta COF) pores and used for remarkable photocatalytic hydrogen(H2) production under Ultraviolet–Visible light (UV–Vis light) irradiation. The single-atom Co is visualized by the aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC HAADF-STEM), and the C3–Co–N1 coordination structure is demonstrated by X-ray absorption fine structure (XAFS) measurements. The modified Co0.4-SAC/Tp-Tta COF shows a high photocatalytic H2 production of 1798.5 μmol g−1 h−1 and the Apparent quantum yield(AQY) is 3.02% at 420 nm. The improvement of the activity and stability of the photocatalyst is mainly attributed to the incorporation of Co single-atom that boosts the separation efficiency of photogenerated electron-hole pair and provides well-dispersed active sites. This study provides valuable insights into the development of UV–Vis light-responsive photocatalysts at the atomic level.

Formulation of next-generation polyvalent vaccine candidates against three important poxviruses by targeting DNA-dependent RNA polymerase using an integrated immunoinformatics and molecular modeling approach

BackgroundPoxviruses comprise a group of large double-stranded DNA viruses and are known to cause diseases in humans, livestock animals, and other animal species. The Mpox virus (MPXV; formerly Monkeypox), variola virus (VARV), and volepox virus (VPXV) are among the prevalent poxviruses of the Orthopoxviridae genera. The ongoing Mpox infectious disease pandemic caused by the Mpox virus has had a major impact on public health across the globe. To date, only limited repurposed antivirals and vaccines are available for the effective treatment of Mpox and other poxviruses that cause contagious diseases. MethodsThe present study was conducted with the primary goal of formulating multi-epitope vaccines against three evolutionary closed poxviruses i.e., MPXV, VARV, and VPXV using an integrated immunoinformatics and molecular modeling approach. DNA-dependent RNA polymerase (DdRp), a potential vaccine target of poxviruses, has been used to determine immunodominant B and T-cell epitopes followed by interactions analysis with Toll-like receptor 2 at the atomic level. ResultsThree multi-epitope vaccine constructs, namely DdRp_MPXV (V1), DdRp_VARV (V2), and DdRp_VPXV (V3) were designed. These vaccine constructs were found to be antigenic, non-allergenic, non-toxic, and soluble with desired physicochemical properties. Protein-protein docking and interaction profiling analysis depicts a strong binding pattern between the targeted immune receptor TLR2 and the structural models of the designed vaccine constructs, and manifested a number of biochemical bonds (hydrogen bonds, salt bridges, and non-bonded contacts). State-of-the-art all-atoms molecular dynamics simulations revealed highly stable interactions of vaccine constructs with TLR2 at the atomic level throughout the simulations on 300 nanoseconds. Additionally, the outcome of the immune simulation analysis suggested that designed vaccines have the potential to induce protective immunity against targeted poxviruses. ConclusionsTaken together, formulated next-generation polyvalent vaccines were found to have good efficacy against closely related poxviruses (MPXV, VARV, and VPXV) as demonstrated by our extensive immunoinformatics and molecular modeling evaluations; however, further experimental investigations are still needed.

Ferroelectric Domain Intrinsic Radiation Resistance of Lithium Niobate Ferroelectric Single−Crystal Film

The study of the properties of ferroelectric materials against irradiation has a long history. However, anti−irradiation research on the ferroelectric domain has not been carried out. In this paper, the irradiation of switched domain structure is innovatively proposed. The switched domain of 700 nm lithium niobate (LiNbO3, LN) thin film remains stable after gamma irradiation from 1 krad to 10 Mrad, which was prepared by piezoresponse force microscopy (PFM). In addition, the changing law of domain wall resistivity is explored through different sample voltages, and it is verified that the irradiated domain wall conductivity is still larger than the domain. This domain wall current (DWC) property can be applied to storage, logic, sensing, and other devices. Based on these, a ferroelectric domain irradiation resistance model is established, which explains the reason at an atomic level. The results open a possibility for exploiting ferroelectric materials as the foundation in the application of space and nuclear fields.

Toxicological study on ibuprofen and selenium in freshwater mussel Lamellidens marginalis and exploring the microbial cytochrome through modelling and quantum mechanics approaches for its toxicity degradation in contaminated environment

Toxicological stress in aquatic organisms is caused by the discharge of hundreds of toxic pollutants and contaminants among which the current study concentrates on the toxic effect of non-steroidal anti-inflammatory drug ibuprofen (IBF) and the trace element selenium (Se). In this study, IBF and Se toxicity on freshwater mussel Lamellidens marginalis was studied for 14 days, and in silico predictions for their degradation were made using Molecular modelling and Quantum Mechanical approaches. The degrading propensity of cytochrome c oxidase proteins from Trametes verticillatus and Thauera selenatis (Turkey tail fungi and Gram-negative bacteria) is examined into atom level. The results of molecular modelling study indicate that ionic interactions occur in the T. selenatis-HEME bound complex by Se interacting directly with HEME, and in the T. versicolor-HEME bound complex by IBF bound to a nearby region of HEME. Experimental and theoretical findings suggest that, the toxicological effects of Se and IBF pollution can be reduced by bioremediation with special emphasis on T. versicolor, and T. selenatis, which can effectively interact with Se and IBF present in the environment and degrade them. Besides, this is the first time in freshwater mussel L. marginalis that ibuprofen and selenium toxicity have been studied utilizing both experimental and computational methodologies for their bioremediation study.

Molecular Mechanisms of the Impaired Heparin Pentasaccharide Interactions in 10 Antithrombin Heparin Binding Site Mutants Revealed by Enhanced Sampling Molecular Dynamics.

Antithrombin (AT) is a critical regulator of the coagulation cascade by inhibiting multiple coagulation factors including thrombin and FXa. Binding of heparinoids to this serpin enhances the inhibition considerably. Mutations located in the heparin binding site of AT result in thrombophilia in affected individuals. Our aim was to study 10 antithrombin mutations known to affect their heparin binding in a heparin pentasaccharide bound state using two molecular dynamics (MD) based methods providing enhanced sampling, GaMD and LiGaMD2. The latter provides an additional boost to the ligand and the most important binding site residues. From our GaMD simulations we were able to identify four variants (three affecting amino acid Arg47 and one affecting Lys114) that have a particularly large effect on binding. The additional acceleration provided by LiGaMD2 allowed us to study the consequences of several other mutants including those affecting Arg13 and Arg129. We were able to identify several conformational types by cluster analysis. Analysis of the simulation trajectories revealed the causes of the impaired pentasaccharide binding including pentasaccharide subunit conformational changes and altered allosteric pathways in the AT protein. Our results provide insights into the effects of AT mutations interfering with heparin binding at an atomic level and can facilitate the design or interpretation of in vitro experiments.

Sub-2 nm Microstrained High-Entropy-Alloy Nanoparticles Boost Hydrogen Electrocatalysis.

High-entropy alloys (HEAs) confine multifarious elements into the same lattice, leading to intense lattice distortion effect. The lattice distortion tends to induce local microstrain at atomic level and thus affect surface adsorptions toward different adsorbates in various electrocatalytic reactions, yet remains unexplored. Herein, this work reports a class of sub-2nm IrRuRhMoW HEA nanoparticles (NPs) with distinct local microstrain induced by lattice distortion for boosting alkaline hydrogen oxidation (HOR) and evolution reactions (HER). This work demonstrates that the distortion-rich HEA catalysts with optimized electronic structure can downshift the d-band center and generate uncoordinated oxygen sites to enhance the surface oxophilicity. As a result, the IrRuRhMoW HEA NPs show a remarkable HOR kinetic current density of 8.09mA µg-1 PGM at 50mV versus RHE, 8.89, 22.47 times higher than those of IrRuRh NPs without internal strain and commercial Pt/C, respectively, which is the best value among all the reported non-Pt based catalysts. IrRuRhMoW HEA NPs also display great HER performances with a turnover frequency (TOF) value of 5.93 H2 s-1 at 70mV versus RHE, 4.6-fold higher than that of Pt/C catalyst, exceeding most noble metal-based catalysts. Experimental characterizations and theoretical studies collectively confirm that weakened hydrogen (Had) and enhanced hydroxyl (OHad) adsorption are achieved by simultaneously modulating the hydrogen adsorption binding energy and surface oxophilicity originated from intensified ligand effect and microstrain effect over IrRuRhMoW HEA NPs, which guarantees the remarkable performances toward HOR/HER.

Constraining the chameleon-photon coupling with atomic spectroscopy

We compute bounds from atomic spectroscopy on chameleon fields that couple to the photon. Chameleons are a wide class of scalar field models that generically lead to screened fifth forces and a host of novel phenomenologies, particularly when the photon coupling is included. We account for perturbations to the atomic energy levels from both the scalar field ‘fifth force’ and the scalar field’s correction to the electric field. We also account for the electromagnetic interaction’s contribution to the scalar charge of the proton, which enables a considerably wider class of models to be tested than without this effect. We find bounds that cover different areas of chameleon parameter space. A range of models spanning approximately one order of magnitude in chameleon coupling parameters (around M,Mγ≈10−16MPl) are excluded for the first time. We also show that improvements to the theoretical uncertainty of hydrogen’s spectrum within the Standard Model would immediately rule out additional chameleon theory space by this analysis. Published by the American Physical Society 2024

Exploring ice Ic nucleation and structural relaxation in supercooled water

Despite intensive research efforts, understanding how water freezes remains an open and relevant question with profound implications. In this study, we examine ice Ic nucleation and water relaxation at the atomic level, employing molecular dynamics (MD) simulations and Classical Nucleation Theory (CNT). Our key findings address the following foundational issues: (i) Routes to cubic ice. Ice Ic seeding liquid water results in equal amounts of ice Ic and Ih structures at T<235K, while ice Ic predominates at T⩾235K along zero isobar. Moreover, ice produced from spontaneous nucleation at T=205-215K is more cubic compared with that grown on ice Ic seeds; (ii) CNT validity. Using MD-generated data, CNT accurately predicts ice nucleation rates without any fitting parameter, thereby bridging the gap between simulations and experiments; (iii) Kinetic crossroads. We determined a kinetic spinodal for high-density water as an intersection of relaxation and nucleation time curves at TKS=199K for a MD sample and TKS=233K for a macroscopic sample, which coincides with the experimental homogenous freezing limit; (iv) Kauzmann conundrum. Finally, we indicated that if the Kauzmann temperature exists, estimated as TK=190K, it might be inaccessible for high-density water due to the kinetic spinodal at a higher temperature, TKS>TK, thus resolving the long-standing entropy paradox. Overall, this research provides valuable insights into fundamental aspects related to water crystallization.

Advanced Development of In situ Characterization Technique for Electrocatalytic Hydrogen Evolution Reaction

AbstractHydrogen evolution reaction (HER) from water splitting using renewable energy provides a promising solution to the global energy crisis and environmental problems. However, the lack of in‐depth understanding of the reaction mechanism and clear identification of the catalytic active site has hindered the further development of low‐cost, high‐performance, and long‐life efficient electrocatalysts. Through in situ characterization techniques, the activity and stability of catalysts can be monitored in real‐time, track the structural evolution of catalytic reaction intermediates, and obtain a deep understanding of catalytic reaction mechanism, so as to feedback and guide the development and utilization of the catalyst. In this review, advanced development of in situ characterization techniques in electrocatalytic HER in recent years is summarized. In situ spectroscopy can be used to track the behavior of reaction intermediates such as adsorption, desorption, and structural evolution at the molecular level to reveal the electrocatalytic HER mechanism. The imaging techniques can be used to observe the evolution of material structure during HER in situ, which provides valuable information for the understanding of visualization of catalytic hydrogen evolution at atomic level. This review contributes to theadvanced development of in situ characterization technique for electrocatalytic HER.

Martini-Based Coarse-Grained Soil Organic Matter Model Derived from Atomistic Simulations.

The significance of soil organic matter (SOM) in environmental contexts, particularly its role in pollutant adsorption, has prompted an increased utilization of molecular simulations to understand microscopic interactions. This study introduces a coarse-grained SOM model, parametrized within the framework of the versatile Martini 3 force field. Utilizing models generated by the Vienna Soil Organic Matter Modeler 2, which constructs humic substance systems from a fragment database, we employed Swarm-CG to parametrize the fragments and subsequently assembled them into macromolecules. Direct Boltzmann inversion (DBI) facilitated the determination of bonded parameters between fragments. The parametrization yielded favorable agreement in the radius of gyration and solvent-accessible surface area. Transfer free energies exhibited a strong correlation with hexadecane-water and chloroform-water values, albeit deviations were noted for octanol-water values. Comparing densities of modeled Leonardite humic acid systems at coarse-grained and atomistic levels revealed promising agreement, particularly at higher water concentrations. The DBI approach effectively reproduced average values of bonded interactions between fragments. Radial distribution functions between carboxylate groups and calcium ions showed partial agreement, however, reproducing certain peaks was challenging due to fixed bead sizes. Detailed analysis of atomistic systems revealed different configurations between the groups, explaining discrepancies. The present contribution provides a comprehensive insight into the properties, strengths, and weaknesses of the coarse-grained SOM model, serving as a foundation for future investigations encompassing pollutant interactions and varied SOM compositions.