THE mechanical response and deformation mechanisms of pure nickel under nanoindentation were systematically investigated using molecular dynamics(MD)simulations,with a particular focus on the novel interplay between c...THE mechanical response and deformation mechanisms of pure nickel under nanoindentation were systematically investigated using molecular dynamics(MD)simulations,with a particular focus on the novel interplay between crystallographic orientation,grain boundary(GB)proximity,and pore characteristics(size/location).This study compares single-crystal nickel models along[100],[110],and[111]orientations with equiaxed polycrystalline models containing 0,1,and 2.5 nm pores in surface and subsurface configurations.Our results reveal that crystallographic anisotropy manifests as a 24.4%higher elastic modulus and 22.2%greater hardness in[111]-oriented single crystals compared to[100].Pore-GB synergistic effects are found to dominate the deformation behavior:2.5 nm subsurface pores reduce hardness by 25.2%through stress concentration and dislocation annihilation at GBs,whereas surface pores enable mechanical recovery via accelerated dislocation generation post-collapse.Additionally,size-dependent deformation regimes were identified,with 1 nm pores inducing negligible perturbation due to rapid atomic rearrangement,in contrast with persistent softening in 2.5 nm pores.These findings establish atomic-scale design principles for defect engineering in nickel-based aerospace components,demonstrating how crystallographic orientation,pore configuration,and GB interactions collectively govern nanoindentation behavior.展开更多
Compared to the well-studied two-dimensional(2D)ferroelectricity,the appearance of 2D antiferroelectricity is much rarer,where local dipoles from the nonequivalent sublattices within 2D monolayers are oppositely orien...Compared to the well-studied two-dimensional(2D)ferroelectricity,the appearance of 2D antiferroelectricity is much rarer,where local dipoles from the nonequivalent sublattices within 2D monolayers are oppositely oriented.Using NbOCl_(2) monolayer with competing ferroelectric(FE)and antiferroelectric(AFE)phases as a 2D material platform,we demonstrate the emergence of intrinsic antiferroelectricity in NbOCl_(2) monolayer under experimentally accessible shear strain,along with new functionality associated with electric field-induced AFE-to-FE phase transition.Specifically,the complex configuration space accommodating FE and AFE phases,polarization switching kinetics,and finite temperature thermodynamic properties of 2D NbOCl_(2) are all accurately predicted by large-scale molecular dynamics simulations based on deep learning interatomic potential model.Moreover,room temperature stable antiferroelectricity with low polarization switching barrier and one-dimensional collinear polarization arrangement is predicted in shear-deformed NbOCl_(2) monolayer.The transition from AFE to FE phase in 2D NbOCl_(2) can be triggered by a low critical electric field,leading to a double polarization–electric(P–E)loop with small hysteresis.A new type of optoelectronic device composed of AFE-NbOCl_(2) is proposed,enabling electric“writing”and nonlinear optical“reading”logical operation with fast operation speed and low power consumption.展开更多
The global energy demand is increasing rapidly,and it is imperative to develop shale hydrocarbon re-sources vigorously.The prerequisite for enhancing the exploitation efficiency of shale reservoirs is the systematic e...The global energy demand is increasing rapidly,and it is imperative to develop shale hydrocarbon re-sources vigorously.The prerequisite for enhancing the exploitation efficiency of shale reservoirs is the systematic elucidation of the occurrence characteristics,flow behavior,and enhanced oil recovery(EOR)mechanisms of shale oil within commonly developed nanopores.Molecular dynamics(MD)technique can simulate the occurrence,flow,and extraction processes of shale oil at the nanoscale,and then quantitatively characterize various fluid properties,flow characteristics,and action mechanisms under different reservoir conditions by calculating and analyzing a series of MD parameters.However,the existing review on the application of MD simulation in shale oil reservoirs is not systematic enough and lacks a summary of technical challenges and solutions.Therefore,recent MD studies on shale oil res-ervoirs were summarized and analyzed.Firstly,the applicability of force fields and ensembles of MD in shale reservoirs with different reservoir conditions and fluid properties was discussed.Subsequently,the calculation methods and application examples of MD parameters characterizing various properties of fluids at the microscale were summarized.Then,the application of MD simulation in the study of shale oil occurrence characteristics,flow behavior,and EOR mechanisms was reviewed,along with the elucidation of corresponding micro-mechanisms.Moreover,influencing factors of pore structure,wall properties,reservoir conditions,fluid components,injection/production parameters,formation water,and inorganic salt ions were analyzed,and some new conclusions were obtained.Finally,the main challenges associated with the application of MD simulations to shale oil reservoirs were discussed,and reasonable prospects for future MD research directions were proposed.The purpose of this review is to provide theoretical basis and methodological support for applying MD simulation to study shale oil reservoirs.展开更多
The extraordinary strength of metal/graphene composites is significantly determined by the characteristic size,distribution and morphology of graphene.However,the effect of the graphene size/distribution on the mechan...The extraordinary strength of metal/graphene composites is significantly determined by the characteristic size,distribution and morphology of graphene.However,the effect of the graphene size/distribution on the mechanical properties and related strengthening mechanisms has not been fully elucidated.Herein,under the same volume fraction and distribution conditions of graphene,molecular dynamics simulations were used to investigate the effect of graphene sheet size on the hardness and deformation behavior of Cu/graphene composites under complex stress field.Two models of pure single crystalline Cu and graphene fully covered Cu matrix composite were constructed for comparison.The results show that the strengthening effect changes with varying the graphene sheet size.Besides the graphene dislocation blocking effect and the load-bearing effect,the deformation mechanisms change from stacking fault tetrahedron,dislocation bypassing and dislocation cutting to dislocation nucleation in turn with decreasing the graphene sheet size.The hardness of Cu/graphene composite,with the graphene sheet not completely covering the metal matrix,can even be higher than that of the fully covered composite.The extra strengthening mechanisms of dislocation bypassing mechanism and the stacking fault tetrahedra pinning dislocation mechanism contribute to the increase in hardness.展开更多
Carbon nanotube formation exemplifies atomically precise self-assembly,where atomic interactions dynamically engineer nanoscale architectures with emergent properties that transcend classical material boundaries.Howev...Carbon nanotube formation exemplifies atomically precise self-assembly,where atomic interactions dynamically engineer nanoscale architectures with emergent properties that transcend classical material boundaries.However,elucidating the transient molecular intermediates remains a critical mechanistic frontier.This study investigates the atomic-scale nucleation process of single-walled carbon nanotubes(SWCNTs)from acetylene on iron(Fe)clusters,utilizing GFN(-x)TB-based nanoreactor molecular dynamics simulations.The simulations reveal a consistent nucleation pathway,regardless of iron cluster size(Fe_(13),Fe_(38),Fe_(55)),where the chemisorption and dissociation of acetylene molecules on the Fe clusters lead to the formation of C_(2)H and C_(2)intermediates.These species then undergo oligomerization,initiating the growth of carbon chains.As the chains cross-link and cyclize,five-membered carbon rings are preferentially formed,which eventually evolve into six-membered rings and more complex sp2-hybridized carbon networks,resembling the cap structures of nascent SWCNTs.Although the nucleation mechanism remains similar across all cluster sizes,larger clusters show enhanced catalytic activity,leading to higher molecular weight hydrocarbons and more extensive carbocyclic networks due to their higher density of active sites per reacting molecule.Crucially,the study highlights the role of C_(2)H as the key active species in the carbon network formation process.These findings offer critical insights into the initial stages of SWCNT nucleation,contributing to a deeper understanding of the mechanisms driving SWCNT growth and guiding the development of optimized synthetic strategies.展开更多
Background:In this present study,we have screened major phytoconstituents of Nilavembu Kudineer against critical COVID-19 target proteins that cause severe pneumonia globally.In addition,a human receptor protein that ...Background:In this present study,we have screened major phytoconstituents of Nilavembu Kudineer against critical COVID-19 target proteins that cause severe pneumonia globally.In addition,a human receptor protein that facilitates viral entry into the host cell was also targeted.Methods:Phytoconstituents derived from Nilavembu Kudineer formulation were docked against 12 major proteins,which help viral entry,viral proliferation,and a human receptor facilitate the viral entry into the host cells.The major metabolites of Nilavembu Kudineer were retrieved based on literature from the PubChem database.The docked complex was subjected to MD simulation studies to verify its binding mode and the stability of the interactions.The binding energy analysis was performed to estimate the binding affinity between the compounds and their respective receptors using MM/GBSA.Results:Docking studies have shown that three major plants in the polyherbal formulation,Andrographis paniculata,Mollugo cerviana,and Zingiber officinale,have 14 potential compounds that have better binding affinity against COVID-19 proteins and their host receptor protein.MD studies and binding energy calculations also confirmed that these compounds possess better stability and strong binding energy with these proteins.Conclusion:In silico analyses suggest that phytoconstituents from Nilavembu Kudineer possess promising multi-target antiviral activity against COVID-19.These findings provide a rationale for further experimental studies to validate their therapeutic potential for the treatment of COVID-19.展开更多
A microscopic understanding of the complex solute-defect interaction is pivotal for optimizing the alloy’s macroscopic mechanical properties.Simulating solute segregation in a plastically deformed crystalline system ...A microscopic understanding of the complex solute-defect interaction is pivotal for optimizing the alloy’s macroscopic mechanical properties.Simulating solute segregation in a plastically deformed crystalline system at atomic resolution remains challenging.The objective is to efficiently model and predict a phys-ically informed segregated solute distribution rather than simulating a series of diffusion kinetics.To ad-dress this objective,we coupled molecular dynamics(MD)and Monte Carlo(MC)methods using a novel method based on virtual atoms technique.We applied our MD-MC coupling approach to model off-lattice carbon(C)solute segregation in nanoindented Fe-C samples containing complex dislocation networks.Our coupling framework yielded the final configuration through efficient parallelization and localized en-ergy computations,showing C Cottrell atmospheres near dislocations.Different initial C concentrations resulted in a consistent trend of C atoms migrating from less crystalline distortion to high crystalline distortion regions.Besides unraveling the strong spatial correlation between local C concentration and defect regions,our results revealed two crucial aspects of solute segregation preferences:(1)defect ener-getics hierarchy and(2)tensile strain fields near dislocations.The proposed approach is generic and can be applied to other material systems as well.展开更多
Enhancing rubber-bitumen compatibility is crucial to improve pavement performance and durability.To investigate the compatibility improvement between H2O2-activated waste crumb rubber(AWCR)and bitumen,coarse and fine ...Enhancing rubber-bitumen compatibility is crucial to improve pavement performance and durability.To investigate the compatibility improvement between H2O2-activated waste crumb rubber(AWCR)and bitumen,coarse and fine waste crumb rubber(WCR)were treated and analyzed through multi-scale characterization and molecular simulation.Microstructure and chemical changes of WCR and AWCR were analyzed with scanning electron microscope(SEM),contact angle tests and Fourier transform infrared spectroscopy(FTIR).Compatibility was also indirectly evaluated through modified boiling tests and storage stability tests.Besides,molecular dynamics was used to explore the interaction between WCR/AWCR and bitumen.SEM,contact angle,and FTIR results showed bond breakage of C=C and C–C and increased polar groups like–OH and–COOH in AWCR,resulting in a rougher texture and higher surface energy.Compared with WCR,AWCR showed a lower bitumen stripping rate after boiling,and the binder with AWCR also had a lower softening point difference and segregation rate after storage.Molecular dynamics simulations further confirmed that AWCR has a closer solubility parameter and higher binding energy to bitumen than WCR,reflected in a relatively slower diffusion rate.This study provides comprehensive evidence for an eco-friendly method of WCR surface treatment for more efficient recycling of tire rubber in asphalt pavements.展开更多
This study investigates the effect of shock velocity(u_(p))on damage evolution mechanisms in nanocrystalline iron via molecular dynamics simulations.As u_(p)increases,shock wave propagation accelerates,and stress dist...This study investigates the effect of shock velocity(u_(p))on damage evolution mechanisms in nanocrystalline iron via molecular dynamics simulations.As u_(p)increases,shock wave propagation accelerates,and stress distribution transitions from grain boundary concentration to homogeneity.This causes a transition in fracture mode from cleavage to ductile behavior.When u_(p)exceeds 1.5 km·s^(-1),micro-spallation emerges as the dominant failure mode.During micro-spallation,localized melting within the material impedes the propagation of the shock wave.As u_(p)increases,the growth rate of the void volume fraction initially rises but then decreases.Higher u_(p)leads to earlier void nucleation.At lower u_(p),the cavitation of the model is mainly characterized by the growth and penetration of a few voids.With increasing u_(p),the number of voids grows,and their interactions expand the delamination damage region.The spall strength demonstrates stage-specific dependence on u_(p).In the classical spallation stage(C_Ⅰ),temperature softening reduces spall strength.In the plastic strengthening regime(C_Ⅱ),strain hardening enhances spall strength.In the micro-spallation stage(M_Ⅲ),further increases in u_(p)cause melting during tensile and compressive phases,reducing spall strength.Finally,in the compressionmelting regime(M_Ⅳ),local temperatures exceed the melting point,diminishing plastic damage and accelerating spall strength reduction.This study provides new insights into the dynamic response of nanocrystalline iron.展开更多
Euphorbia helioscopia,a natural plant recognized for its anti-tumor properties,has been extensively investigated in various cancers.However,its therapeutic potential in gastric cancer with positive lymph node metastas...Euphorbia helioscopia,a natural plant recognized for its anti-tumor properties,has been extensively investigated in various cancers.However,its therapeutic potential in gastric cancer with positive lymph node metastasis remains underexplored.This study aimed to elucidate the role of E.helioscopia in treating gastric cancer with lymph node metastasis using an integrative approach that combined network pharmacology,molecular docking,and molecular dynamics simulations.Initially,shared target data between E.helioscopia and gastric cancer with positive lymph node metastasis were identified and systematically analyzed.Subsequently,molecular docking was conducted to validate the interactions between key components and targets.Finally,molecular dynamics simulations were employed,with binding free energy calculations performed using the MM-PBSA algorithm.The findings revealed that the primary bioactive compounds of E.helioscopia in this context included quercetin and luteolin,targeting core molecules such as EGFR and MMP9.Key pathways implicated in its mechanism of action included resistance to EGFR tyrosine kinase inhibitors,among others.Molecular docking demonstrated robust binding affinity between the active compounds and critical targets,with molecular dynamics and binding free energy analyses highlighting a particularly stable interaction between luteolin and MMP9.In conclusion,E.helioscopia exhibited a multi-component,multi-target,and multi-pathway therapeutic profile in treating gastric cancer with positive lymph node metastasis.These findings offered valuable theoretical insights supporting its potential clinical application in oncology.展开更多
Understanding the rheology of bentonite suspensions is crucial for ensuring the safety of engineering practices.However,the rheological mechanisms of bentonite remain unclear due to the limitations of conventional exp...Understanding the rheology of bentonite suspensions is crucial for ensuring the safety of engineering practices.However,the rheological mechanisms of bentonite remain unclear due to the limitations of conventional experimental techniques,particularly in assessing the microscopic interactions between clay particles and their impact on rheological properties.In this paper,the rheological behaviors of Namontmorillonite were studied with a focus on interparticle interactions.Both equilibrium molecular dynamics(MD)and non-equilibrium MD simulations were conducted to understand the physical properties of Na-montmorillonite under zero shear and various shear rates,respectively.The interaction between two parallel clay particles was determined in simulations,indicating that the classical Darjaguin-Landau-Verwey-Overbeek(DLVO)theory underestimates the interactions for a small separation distance.Na-montmorillonite exhibits a typical shear thinning behavior under shearing.However,as water content increases,it begins to behave more like liquid water.The yield stress of montmorillonite,as determined by the Bingham model,was found to be linearly related to the interaction pressures between clay particles.Besides MD simulations,the microstructure of clay suspension was further quantified using the separation distance and incline angle between non-parallel clay particles.Based on MD results and the quantified clay structure,a model was developed to estimate the yield stress of montmorillonite considering various influence factors,including electrolyte concentration,temperature,and solid fraction.Finally,from a comparison with calculated and experimental data,the results confirm the good performance of the proposed model.These findings provide significant insights for understanding the rheological soil behaviors and evaluating the yield stress of bentonite suspensions.展开更多
Eu^(2+)doped fluorosilicate glass-ceramics containing BaF_(2) nanocrystals have high potential as spectral conversion materials for organic solar cells.However,it is difficult to realize the efficient design of BaF_(2...Eu^(2+)doped fluorosilicate glass-ceramics containing BaF_(2) nanocrystals have high potential as spectral conversion materials for organic solar cells.However,it is difficult to realize the efficient design of BaF_(2):Eu^(2+)doped fluorosilicate glass and to vividly observe the glass microstructure in experiment through traditional trial-and-error glass preparation method.BaF_(2):Eu^(2+)doped fluorosilicate glassceramics with high transparency,and high photoluminescence(PL)performance were predicted,designed and prepared via molecular dynamics(MD)simulation method.By MD simulation prediction,self-organized nanocrystallization was realized to inhibit the abnormal growth of nanocrystals due to[AlO_(4)]tetrahedra formed in the fluoride-oxide interface.The introduction of NaF reduces the effective phonon energy of the glass because Na+will prompt Al^(3+)to migrate from the fluoride phase to the silicate phase and interface.The local environment of Eu^(2+)is optimized by predicting the doping concentration of EuF_(3) and 2 mol%EuF3 is the best concentration in this work.Glass-ceramics sample GC2Eu as spectral conversion layer was successfully applied on organic solar cells to obtain more available visible phonons with a high photoelectric conversion efficiency(PCE).This work confirms the guidance of molecular dynamics simulation methods for fluorosilicate glasses design.展开更多
To efficiently address the current high cost associated with preparing pseudo-boehmite from organic aluminum,a low-cost alternative,AlCl_(3),is employed as the raw material.The sol-gel method is utilized,and H_(2)O_(2...To efficiently address the current high cost associated with preparing pseudo-boehmite from organic aluminum,a low-cost alternative,AlCl_(3),is employed as the raw material.The sol-gel method is utilized,and H_(2)O_(2)is incorporated for the modification of pseudo-boehmite.The modification mechanism is thoroughly investigated through the use of X-ray powder diffractometer,scanning electron microscope,and BET data analysis,as well as molecular dynamics simulations.Under specific conditions(temperature at 80°C,pH=7,and H_(2)O_(2)volume ratios of 0.5:1,1:1,and 2:1),mesoporous pseudo-boehmite is synthesized with a specific surface area of 227 m^(2)/g,a pore volume of 0.281 cm^(3)/g,a pore size of 6.78 nm,and a peptizing index of 99.47%.A novel and innovative methodology for the cost-effective production of high-performance alumina is offered through the approach.展开更多
Molecular-level interactions between polymeric inhibitors and wax crystals are essential for mitigating wax deposition in crude oils,a major operational and environmental challenge.This study investigates the mechanis...Molecular-level interactions between polymeric inhibitors and wax crystals are essential for mitigating wax deposition in crude oils,a major operational and environmental challenge.This study investigates the mechanisms by which specific inhibitors target wax crystals to prevent aggregation.Extracted wax and inhibitor were characterized using gas chromatography,X-ray diffraction,and spectroscopy to determine the molecular structures.The wax primarily comprised of straight-chain nC28 alkanes,while the inhibitor was an ethylene/vinyl acetate copolymer.Rheological tests demonstrated a reduced gelation point upon inhibitor addition.Molecular dynamics(MD)simulations,performed using the COMPASS II force field,revealed interactions at the molecular level.Structural validation of molecules was done through comparative analysis of the experimental infrared and simulated vibrational analysis spectra whereas that of the rhombohedral wax crystal was achieved using the Pawley method,yielding a Profile R-factor of 9.26%.Morphological studies revealed five symmetrically unique facets,with the(110)plane being the fastestgrowing due to its inter-planar distance and attachment energy(-157.25 kcal/mol).Adsorption energy calculations(-180 kcal/mol)confirmed that the inhibitor effectively disrupted crystal growth on the surface by adsorbing its polar section onto the wax surface while repelling the non-polar groups,thereby reducing waxaggregation.展开更多
Stimuli-responsive polymers capable of rapidly altering their chain conformation in response to external stimuli exhibit broad applica-tion prospects.Experiments have shown that pressure plays a pivotal role in regula...Stimuli-responsive polymers capable of rapidly altering their chain conformation in response to external stimuli exhibit broad applica-tion prospects.Experiments have shown that pressure plays a pivotal role in regulating the microscopic chain conformation of polymers in mixed solvents,and one notable finding is that increasing the pressure can lead to the vanishing of the co-nonsolvency effect.However,the mecha-nisms underlying this phenomenon remain unclear.In this study,we systematically investigated the influence of pressure on the co-nonsolvency effect of single-chain and multi-chain homopolymers in binary mixed good-solvent systems using molecular dynamics simulations.Our results show that the co-nonsolvency-induced chain conformation transition and aggregation behavior significantly depend on pressure in allsingle-chain and multi-chain systems.In single-chain systems,at low pressures,the polymer chain maintains a collapsed state over a wide range of co-solvent fractions(x-range)owing to the co-nonsolvency effect.As the pressure increases,the x-range of the collapsed state gradually narrows,ac-companied by a progressive expansion of the chain.In multichain systems,polymer chains assemble into approximately spherical aggregates over a broad x-range at low pressures owing to the co-nonsolvency effect.Increasing the pressure reduces the x-range for forming aggregates and leads to the formation of loose aggregates or even to a state of dispersed chains at some x-range.These findings indicate that increasing the pressure can weaken or even offset the co-nonsolvency effect in some x-range,which is in good agreement with the experimental observations.Quantitative analysis of the radial density distributions and radial distribution functions reveals that,with increasing pressure,(1)the densities of both polymers and co-solvent molecules within aggregates decrease,while that of the solvent molecule increases;and(2)the effective interac-tions between the polymer and the co-solvent weaken,whereas those between the polymer and solvent strengthen.This enhances the incorpo-ration of solvent molecules within the chains,thereby weakening or even suppressing the chain aggregation.Our study not only elucidates the regulatory mechanism of pressure on the microscopic chain conformations and aggregation behaviors of polymers,but also may provide theo-retical guidance for designing smart polymericmaterials based on mixed solvents.展开更多
To overcome the limitations of microscale experimental techniques and molecular dynamics(MD)simulations,a coarse-grained molecular dynamics(CGMD)method was used to simulate the wetting processes of clay aggregates.Bas...To overcome the limitations of microscale experimental techniques and molecular dynamics(MD)simulations,a coarse-grained molecular dynamics(CGMD)method was used to simulate the wetting processes of clay aggregates.Based on the evolution of swelling stress,final dry density,water distribution,and clay arrangements under different target water contents and dry densities,a relationship between the swelling behaviors and microstructures was established.The simulated results showed that when the clay-water well depth was 300 kcal/mol,the basal spacing from CGMD was consistent with the X-ray diffraction(XRD)data.The effect of initial dry density on swelling stress was more pronounced than that of water content.The anisotropic swelling characteristics of the aggregates are related to the proportion of horizontally oriented clay mineral layers.The swelling stress was found to depend on the distribution of tactoids at the microscopic level.At lower initial dry density,the distribution of tactoids was mainly controlled by water distribution.With increase in the bound water content,the basal spacing expanded,and the swelling stresses increased.Free water dominated at higher water contents,and the particles were easily rotated,leading to a decrease in the number of large tactoids.At higher dry densities,the distances between the clay mineral layers decreased,and the movement was limited.When bound water enters the interlayers,there is a significant increase in interparticle repulsive forces,resulting in a greater number of small-sized tactoids.Eventually,a well-defined logarithmic relationship was observed between the swelling stress and the total number of tactoids.These findings contribute to a better understanding of coupled macro-micro swelling behaviors of montmorillonite-based materials,filling a study gap in clay-water interactions on a micro scale.展开更多
The crystallization behavior of polymers is significantly influenced by molecular chain length and the dispersion of varying chain lengths.The complexity of studying crystallization arises from the dispersity of polym...The crystallization behavior of polymers is significantly influenced by molecular chain length and the dispersion of varying chain lengths.The complexity of studying crystallization arises from the dispersity of polymer materials and the typically slow cooling rates.Recent advancements in fast cooling techniques have rendered the investigation of polymer crystallization at varying cooling rates an attractive area of research;however,a systematic quantitative framework for this process is still lacking.We employ a coarse-grained model for polyvinyl alcohol(CGPVA)in molecular dynamics simulations to study the crystallization of linear polymers with varying chain lengths under variable cooling rates.Monodisperse,bidisperse and polydisperse samples are simulated.We propose two formulae based on a two-phase assumption to fit the exothermal curves obtained during cooling.Based on these formulae,better estimations of crystallization temperatures are obtained and the effects of chain lengths and cooling rates are studied.It is found that the crystallization temperature increases with chain length,similar to the Gibbs-Thomson relation formelting temperature,indicating a strong relation between fast crystallization and glass formation in linear polymers.Extrapolation to the infinitely slow cooling rate provides an easy way in simulations to estimate the equilibrium crystallization temperature.The effective chain lengths of polydisperse and bidisperse samples are found to be the number-averaged chain lengths compared to the weight-averaged ones.The chain length-dependent crystallization exhibits crossover behavior near the entanglement length,indicating the effects of entanglements under fast cooling conditions.The effect of chain length dispersity on crystallization becomes more obvious under fast cooling conditions.展开更多
As the main factor influencing the flow and preservation of underground fluids,wettability has a profound impact on CO_(2)sequestration(CS).However,the influencing factors and internal interaction mechanisms of shale ...As the main factor influencing the flow and preservation of underground fluids,wettability has a profound impact on CO_(2)sequestration(CS).However,the influencing factors and internal interaction mechanisms of shale kerogen wettability remain unclear.In this study,we used molecular dynamics to simulate the influence of temperature,pressure,and salinity on wettability.Furthermore,the results were validated through various methods such as mean square displacement,interaction energy,electrostatic potential energy,hydrogen bonding,van der Waals forces,and electrostatic forces,thereby confirming the reliability of our findings.As temperature increases,water wettability on the surface of kerogen increases.At CO_(2)pressures of 10 and 20 MPa,as the temperature increases,the kerogen wettability changes from CO_(2)wetting to neutral wetting.As the CO_(2)pressure increases,the water wettability on the surface of kerogen weakens.When the pressure is below 7.375 MPa and the temperature is 298 or 313 K,kerogen undergoes a wettability reversal from neutral wetting to CO_(2)wetting.As salinity increases,water wettability weakens.Divalent cations(Mg2+and Ca2+)have a greater impact on wettability than monovalent cations(Na^(+)).Water preferentially adsorbs on N atom positions in kerogen.CO_(2)is more likely to form hydrogen bonds and adsorb on the surface of kerogen than H_(2)O.As the temperature increases,the number of hydrogen bonds between H_(2)O and kerogen gradually increases,while the increase in pressure reduces the number of hydrogen bonds.Although high pressure helps to increase an amount of CS,it increases the permeability of a cap rock,which is not conducive to CS.Therefore,when determining CO_(2)pressure,not only a storage amount but also the storage safety should be considered.This research method and results help optimize the design of CS technology,and have important significance for achieving sustainable development.展开更多
The impact of chemical short-range order(SRO)and twin boundary(TB)structures on the deformation response under shock compression in CoCrNi medium-entropy alloy(MEA)was investigated using molecular dynamics(MD)simulati...The impact of chemical short-range order(SRO)and twin boundary(TB)structures on the deformation response under shock compression in CoCrNi medium-entropy alloy(MEA)was investigated using molecular dynamics(MD)simulation.Four microstructural configurations were considered,including random solid solution(RSS),short-range order(SRO),twin boundaries(Twin),and a coupling of SRO and TB(Coup).The results demonstrate that,in comparison to the random MEAs(RSS sample and Twin sam-ple),those with the chemical SRO structure(SRO sample and Coup sample)exhibit a higher shock front zone ratio and an elevated Hugoniot elastic limit(HEL)at a low shock velocity(U_(P)=1200 m/s).This improvement can be attributed to the chemical SRO structure,which increases the energy barrier for dislocation nucleation and propagation.Additionally,pre-existing TBs can also serve as barriers to dislocation movement.In random samples,amorphous clusters tend to initiate from Cr atoms,due to the weak bonding of Cr-Cr pairs.In contrast,in the samples with chemical SRO structure,the increased presence of strong Co-Cr bonding and reduced Cr-Cr bonding effectively raises the activation energy for amor-phization.These local amorphous clusters provide an environment conducive to dislocation nucleation.Consequently,chemical SRO structures lead to increased resistance to dislocation nucleation,where the formation of Shockley Partial(SP)dislocation necessitates longer loading durations,with the nucleation sites situated at a greater distance from the surface.Furthermore,during shock compression in CoCrNi MEAs,SP dislocations preferentially nucleate in the Co-Cr clusters.In conclusion,the presence of chemical SRO structure enhances the shock resistance of the CoCrNi MEAs at lower shock velocities.However,the strengthening effect diminishes with increasing impact velocity and eventually becomes negligible.展开更多
Recent advancements in nanotechnology have spotlighted the catalytic potential of nanozymes, particularly single-atom nanozymes(SANs), which are pivotal for innovations in biosensing and medical diagnostics. Among oth...Recent advancements in nanotechnology have spotlighted the catalytic potential of nanozymes, particularly single-atom nanozymes(SANs), which are pivotal for innovations in biosensing and medical diagnostics. Among others, DNA stands out as an ideal biological regulator. Its inherent programmability and interaction capabilities allow it to significantly modulate nanozyme activity. This study delves into the dynamic interplay between DNA and molybdenum-zinc single-atom nanozymes(Mo-Zn SANs). Using molecular dynamics simulations, we uncover how DNA influences the peroxidase-like activities of Mo-Zn SANs, providing a foundational understanding that broadens the application scope of SANs in biosensing.With these insights as a foundation, we developed and demonstrated a model aptasensor for point-ofcare testing(POCT), utilizing a label-free colorimetric approach that leverages DNA-nanozyme interactions to achieve high-sensitivity detection of lysozyme. Our work elucidates the nuanced control DNA exerts over nanozyme functionality and illustrates the application of this molecular mechanism through a smartphone-assisted biosensing platform. This study not only underscores the practical implications of DNA-regulated Mo-Zn SANs in enhancing biosensing platforms, but also highlights the potential of single-atom nanozyme technology to revolutionize diagnostic tools through its inherent versatility and sensitivity.展开更多
基金The National Natural Science Foundation of China(Grant No.12462006)Beijing Institute of Structure and Environment Engineering Joint Innovation Fund(No.BQJJ202414).
文摘THE mechanical response and deformation mechanisms of pure nickel under nanoindentation were systematically investigated using molecular dynamics(MD)simulations,with a particular focus on the novel interplay between crystallographic orientation,grain boundary(GB)proximity,and pore characteristics(size/location).This study compares single-crystal nickel models along[100],[110],and[111]orientations with equiaxed polycrystalline models containing 0,1,and 2.5 nm pores in surface and subsurface configurations.Our results reveal that crystallographic anisotropy manifests as a 24.4%higher elastic modulus and 22.2%greater hardness in[111]-oriented single crystals compared to[100].Pore-GB synergistic effects are found to dominate the deformation behavior:2.5 nm subsurface pores reduce hardness by 25.2%through stress concentration and dislocation annihilation at GBs,whereas surface pores enable mechanical recovery via accelerated dislocation generation post-collapse.Additionally,size-dependent deformation regimes were identified,with 1 nm pores inducing negligible perturbation due to rapid atomic rearrangement,in contrast with persistent softening in 2.5 nm pores.These findings establish atomic-scale design principles for defect engineering in nickel-based aerospace components,demonstrating how crystallographic orientation,pore configuration,and GB interactions collectively govern nanoindentation behavior.
基金supported by the National Natural Science Foundation of China (Grant No.11574244 for G.Y.G.)the XJTU Research Fund for AI Science (Grant No.2025YXYC011 for G.Y.G.)the Hong Kong Global STEM Professorship Scheme (for X.C.Z.)。
文摘Compared to the well-studied two-dimensional(2D)ferroelectricity,the appearance of 2D antiferroelectricity is much rarer,where local dipoles from the nonequivalent sublattices within 2D monolayers are oppositely oriented.Using NbOCl_(2) monolayer with competing ferroelectric(FE)and antiferroelectric(AFE)phases as a 2D material platform,we demonstrate the emergence of intrinsic antiferroelectricity in NbOCl_(2) monolayer under experimentally accessible shear strain,along with new functionality associated with electric field-induced AFE-to-FE phase transition.Specifically,the complex configuration space accommodating FE and AFE phases,polarization switching kinetics,and finite temperature thermodynamic properties of 2D NbOCl_(2) are all accurately predicted by large-scale molecular dynamics simulations based on deep learning interatomic potential model.Moreover,room temperature stable antiferroelectricity with low polarization switching barrier and one-dimensional collinear polarization arrangement is predicted in shear-deformed NbOCl_(2) monolayer.The transition from AFE to FE phase in 2D NbOCl_(2) can be triggered by a low critical electric field,leading to a double polarization–electric(P–E)loop with small hysteresis.A new type of optoelectronic device composed of AFE-NbOCl_(2) is proposed,enabling electric“writing”and nonlinear optical“reading”logical operation with fast operation speed and low power consumption.
基金supported by the National Natural Science Foundation of China(52304021,52104022,52204031)the Natural Science Foundation of Sichuan Province(2022NSFSC0205,2024NSFSC0201,2023NSFSC0947)the National Science and Technology Major Projects of China(2017ZX05049006-010).
文摘The global energy demand is increasing rapidly,and it is imperative to develop shale hydrocarbon re-sources vigorously.The prerequisite for enhancing the exploitation efficiency of shale reservoirs is the systematic elucidation of the occurrence characteristics,flow behavior,and enhanced oil recovery(EOR)mechanisms of shale oil within commonly developed nanopores.Molecular dynamics(MD)technique can simulate the occurrence,flow,and extraction processes of shale oil at the nanoscale,and then quantitatively characterize various fluid properties,flow characteristics,and action mechanisms under different reservoir conditions by calculating and analyzing a series of MD parameters.However,the existing review on the application of MD simulation in shale oil reservoirs is not systematic enough and lacks a summary of technical challenges and solutions.Therefore,recent MD studies on shale oil res-ervoirs were summarized and analyzed.Firstly,the applicability of force fields and ensembles of MD in shale reservoirs with different reservoir conditions and fluid properties was discussed.Subsequently,the calculation methods and application examples of MD parameters characterizing various properties of fluids at the microscale were summarized.Then,the application of MD simulation in the study of shale oil occurrence characteristics,flow behavior,and EOR mechanisms was reviewed,along with the elucidation of corresponding micro-mechanisms.Moreover,influencing factors of pore structure,wall properties,reservoir conditions,fluid components,injection/production parameters,formation water,and inorganic salt ions were analyzed,and some new conclusions were obtained.Finally,the main challenges associated with the application of MD simulations to shale oil reservoirs were discussed,and reasonable prospects for future MD research directions were proposed.The purpose of this review is to provide theoretical basis and methodological support for applying MD simulation to study shale oil reservoirs.
基金Foundation of Northwest Institute for Nonferrous Metal Research(ZZXJ2203)Capital Projects of Financial Department of Shaanxi Province(YK22C-12)+3 种基金Innovation Capability Support Plan in Shaanxi Province(2023KJXX-083)Key Research and Development Projects of Shaanxi Province(2024GXYBXM-351,2024GX-YBXM-356)National Natural Science Foundation of China(62204207,12204383)Xi'an Postdoctoral Innovation Base Funding Program。
文摘The extraordinary strength of metal/graphene composites is significantly determined by the characteristic size,distribution and morphology of graphene.However,the effect of the graphene size/distribution on the mechanical properties and related strengthening mechanisms has not been fully elucidated.Herein,under the same volume fraction and distribution conditions of graphene,molecular dynamics simulations were used to investigate the effect of graphene sheet size on the hardness and deformation behavior of Cu/graphene composites under complex stress field.Two models of pure single crystalline Cu and graphene fully covered Cu matrix composite were constructed for comparison.The results show that the strengthening effect changes with varying the graphene sheet size.Besides the graphene dislocation blocking effect and the load-bearing effect,the deformation mechanisms change from stacking fault tetrahedron,dislocation bypassing and dislocation cutting to dislocation nucleation in turn with decreasing the graphene sheet size.The hardness of Cu/graphene composite,with the graphene sheet not completely covering the metal matrix,can even be higher than that of the fully covered composite.The extra strengthening mechanisms of dislocation bypassing mechanism and the stacking fault tetrahedra pinning dislocation mechanism contribute to the increase in hardness.
基金supported by the National Key R&D Program of China(2022YFA1604100)the National Natural Science Foundation of China(22302220,22372187,1972157,21972160,22402218)+2 种基金the National Science Fund for Distinguished Young Scholars of China(22225206)the Fundamental Research Program of Shanxi Province(202203021222403)the Youth Innovation Promotion Association CAS(2020179)。
文摘Carbon nanotube formation exemplifies atomically precise self-assembly,where atomic interactions dynamically engineer nanoscale architectures with emergent properties that transcend classical material boundaries.However,elucidating the transient molecular intermediates remains a critical mechanistic frontier.This study investigates the atomic-scale nucleation process of single-walled carbon nanotubes(SWCNTs)from acetylene on iron(Fe)clusters,utilizing GFN(-x)TB-based nanoreactor molecular dynamics simulations.The simulations reveal a consistent nucleation pathway,regardless of iron cluster size(Fe_(13),Fe_(38),Fe_(55)),where the chemisorption and dissociation of acetylene molecules on the Fe clusters lead to the formation of C_(2)H and C_(2)intermediates.These species then undergo oligomerization,initiating the growth of carbon chains.As the chains cross-link and cyclize,five-membered carbon rings are preferentially formed,which eventually evolve into six-membered rings and more complex sp2-hybridized carbon networks,resembling the cap structures of nascent SWCNTs.Although the nucleation mechanism remains similar across all cluster sizes,larger clusters show enhanced catalytic activity,leading to higher molecular weight hydrocarbons and more extensive carbocyclic networks due to their higher density of active sites per reacting molecule.Crucially,the study highlights the role of C_(2)H as the key active species in the carbon network formation process.These findings offer critical insights into the initial stages of SWCNT nucleation,contributing to a deeper understanding of the mechanisms driving SWCNT growth and guiding the development of optimized synthetic strategies.
文摘Background:In this present study,we have screened major phytoconstituents of Nilavembu Kudineer against critical COVID-19 target proteins that cause severe pneumonia globally.In addition,a human receptor protein that facilitates viral entry into the host cell was also targeted.Methods:Phytoconstituents derived from Nilavembu Kudineer formulation were docked against 12 major proteins,which help viral entry,viral proliferation,and a human receptor facilitate the viral entry into the host cells.The major metabolites of Nilavembu Kudineer were retrieved based on literature from the PubChem database.The docked complex was subjected to MD simulation studies to verify its binding mode and the stability of the interactions.The binding energy analysis was performed to estimate the binding affinity between the compounds and their respective receptors using MM/GBSA.Results:Docking studies have shown that three major plants in the polyherbal formulation,Andrographis paniculata,Mollugo cerviana,and Zingiber officinale,have 14 potential compounds that have better binding affinity against COVID-19 proteins and their host receptor protein.MD studies and binding energy calculations also confirmed that these compounds possess better stability and strong binding energy with these proteins.Conclusion:In silico analyses suggest that phytoconstituents from Nilavembu Kudineer possess promising multi-target antiviral activity against COVID-19.These findings provide a rationale for further experimental studies to validate their therapeutic potential for the treatment of COVID-19.
基金the funding from the Ger-man Research Foundation(DFG)-BE 5360/1-1 and ThyssenKrupp Europe.
文摘A microscopic understanding of the complex solute-defect interaction is pivotal for optimizing the alloy’s macroscopic mechanical properties.Simulating solute segregation in a plastically deformed crystalline system at atomic resolution remains challenging.The objective is to efficiently model and predict a phys-ically informed segregated solute distribution rather than simulating a series of diffusion kinetics.To ad-dress this objective,we coupled molecular dynamics(MD)and Monte Carlo(MC)methods using a novel method based on virtual atoms technique.We applied our MD-MC coupling approach to model off-lattice carbon(C)solute segregation in nanoindented Fe-C samples containing complex dislocation networks.Our coupling framework yielded the final configuration through efficient parallelization and localized en-ergy computations,showing C Cottrell atmospheres near dislocations.Different initial C concentrations resulted in a consistent trend of C atoms migrating from less crystalline distortion to high crystalline distortion regions.Besides unraveling the strong spatial correlation between local C concentration and defect regions,our results revealed two crucial aspects of solute segregation preferences:(1)defect ener-getics hierarchy and(2)tensile strain fields near dislocations.The proposed approach is generic and can be applied to other material systems as well.
基金supported by the research project“Green-health-safety Nexus for New Urban Spaces-GreeNexUS”(HORIZON MSCA-2021 DN,Marie Sklodowska-Curie Actions)Grant Agreement No.101073437:research grant under the title"Impact Absorbing Pavements with Improved Accessibility Features(DC9-IAP)".
文摘Enhancing rubber-bitumen compatibility is crucial to improve pavement performance and durability.To investigate the compatibility improvement between H2O2-activated waste crumb rubber(AWCR)and bitumen,coarse and fine waste crumb rubber(WCR)were treated and analyzed through multi-scale characterization and molecular simulation.Microstructure and chemical changes of WCR and AWCR were analyzed with scanning electron microscope(SEM),contact angle tests and Fourier transform infrared spectroscopy(FTIR).Compatibility was also indirectly evaluated through modified boiling tests and storage stability tests.Besides,molecular dynamics was used to explore the interaction between WCR/AWCR and bitumen.SEM,contact angle,and FTIR results showed bond breakage of C=C and C–C and increased polar groups like–OH and–COOH in AWCR,resulting in a rougher texture and higher surface energy.Compared with WCR,AWCR showed a lower bitumen stripping rate after boiling,and the binder with AWCR also had a lower softening point difference and segregation rate after storage.Molecular dynamics simulations further confirmed that AWCR has a closer solubility parameter and higher binding energy to bitumen than WCR,reflected in a relatively slower diffusion rate.This study provides comprehensive evidence for an eco-friendly method of WCR surface treatment for more efficient recycling of tire rubber in asphalt pavements.
文摘This study investigates the effect of shock velocity(u_(p))on damage evolution mechanisms in nanocrystalline iron via molecular dynamics simulations.As u_(p)increases,shock wave propagation accelerates,and stress distribution transitions from grain boundary concentration to homogeneity.This causes a transition in fracture mode from cleavage to ductile behavior.When u_(p)exceeds 1.5 km·s^(-1),micro-spallation emerges as the dominant failure mode.During micro-spallation,localized melting within the material impedes the propagation of the shock wave.As u_(p)increases,the growth rate of the void volume fraction initially rises but then decreases.Higher u_(p)leads to earlier void nucleation.At lower u_(p),the cavitation of the model is mainly characterized by the growth and penetration of a few voids.With increasing u_(p),the number of voids grows,and their interactions expand the delamination damage region.The spall strength demonstrates stage-specific dependence on u_(p).In the classical spallation stage(C_Ⅰ),temperature softening reduces spall strength.In the plastic strengthening regime(C_Ⅱ),strain hardening enhances spall strength.In the micro-spallation stage(M_Ⅲ),further increases in u_(p)cause melting during tensile and compressive phases,reducing spall strength.Finally,in the compressionmelting regime(M_Ⅳ),local temperatures exceed the melting point,diminishing plastic damage and accelerating spall strength reduction.This study provides new insights into the dynamic response of nanocrystalline iron.
基金The Gansu Province University Industrial Support Plan(Grant No.2023CYZC-05)the Cuiying Technology Innovation Project of Lanzhou University Second Hospital(Grant No.CY2022-MS-B04)+1 种基金the Doctoral Students Training Research Fund of Lanzhou University Second Hospital(Grant No.YJS-BD-32)the Gansu Province Drug Regulatory Science Research Project in 2024(Grant No.2024GSMPA032).
文摘Euphorbia helioscopia,a natural plant recognized for its anti-tumor properties,has been extensively investigated in various cancers.However,its therapeutic potential in gastric cancer with positive lymph node metastasis remains underexplored.This study aimed to elucidate the role of E.helioscopia in treating gastric cancer with lymph node metastasis using an integrative approach that combined network pharmacology,molecular docking,and molecular dynamics simulations.Initially,shared target data between E.helioscopia and gastric cancer with positive lymph node metastasis were identified and systematically analyzed.Subsequently,molecular docking was conducted to validate the interactions between key components and targets.Finally,molecular dynamics simulations were employed,with binding free energy calculations performed using the MM-PBSA algorithm.The findings revealed that the primary bioactive compounds of E.helioscopia in this context included quercetin and luteolin,targeting core molecules such as EGFR and MMP9.Key pathways implicated in its mechanism of action included resistance to EGFR tyrosine kinase inhibitors,among others.Molecular docking demonstrated robust binding affinity between the active compounds and critical targets,with molecular dynamics and binding free energy analyses highlighting a particularly stable interaction between luteolin and MMP9.In conclusion,E.helioscopia exhibited a multi-component,multi-target,and multi-pathway therapeutic profile in treating gastric cancer with positive lymph node metastasis.These findings offered valuable theoretical insights supporting its potential clinical application in oncology.
基金the financial support provided by the National Science Fund for Distinguished Young Scholars of China(Grant No.42225702)the National Natural Science Fund of China for Excellent Young Scholars Fund(Overseas)+2 种基金Applied Basic Research Programme of Liaoning Province(2023JH2/101300139)Opening fund of State Key Laboratory of Geohazard Prevention and Geoenvironment Protection(Chengdu University of Technology,SKLGP2024K020)Key Laboratory of Earth Fissures Geological Disaster,Ministry of Natural Resources.
文摘Understanding the rheology of bentonite suspensions is crucial for ensuring the safety of engineering practices.However,the rheological mechanisms of bentonite remain unclear due to the limitations of conventional experimental techniques,particularly in assessing the microscopic interactions between clay particles and their impact on rheological properties.In this paper,the rheological behaviors of Namontmorillonite were studied with a focus on interparticle interactions.Both equilibrium molecular dynamics(MD)and non-equilibrium MD simulations were conducted to understand the physical properties of Na-montmorillonite under zero shear and various shear rates,respectively.The interaction between two parallel clay particles was determined in simulations,indicating that the classical Darjaguin-Landau-Verwey-Overbeek(DLVO)theory underestimates the interactions for a small separation distance.Na-montmorillonite exhibits a typical shear thinning behavior under shearing.However,as water content increases,it begins to behave more like liquid water.The yield stress of montmorillonite,as determined by the Bingham model,was found to be linearly related to the interaction pressures between clay particles.Besides MD simulations,the microstructure of clay suspension was further quantified using the separation distance and incline angle between non-parallel clay particles.Based on MD results and the quantified clay structure,a model was developed to estimate the yield stress of montmorillonite considering various influence factors,including electrolyte concentration,temperature,and solid fraction.Finally,from a comparison with calculated and experimental data,the results confirm the good performance of the proposed model.These findings provide significant insights for understanding the rheological soil behaviors and evaluating the yield stress of bentonite suspensions.
基金Project supported by the National Natural Science Foundation of China(52172008,51872255)the Key Research and Development Project of Zhejiang Province(2021C01174)。
文摘Eu^(2+)doped fluorosilicate glass-ceramics containing BaF_(2) nanocrystals have high potential as spectral conversion materials for organic solar cells.However,it is difficult to realize the efficient design of BaF_(2):Eu^(2+)doped fluorosilicate glass and to vividly observe the glass microstructure in experiment through traditional trial-and-error glass preparation method.BaF_(2):Eu^(2+)doped fluorosilicate glassceramics with high transparency,and high photoluminescence(PL)performance were predicted,designed and prepared via molecular dynamics(MD)simulation method.By MD simulation prediction,self-organized nanocrystallization was realized to inhibit the abnormal growth of nanocrystals due to[AlO_(4)]tetrahedra formed in the fluoride-oxide interface.The introduction of NaF reduces the effective phonon energy of the glass because Na+will prompt Al^(3+)to migrate from the fluoride phase to the silicate phase and interface.The local environment of Eu^(2+)is optimized by predicting the doping concentration of EuF_(3) and 2 mol%EuF3 is the best concentration in this work.Glass-ceramics sample GC2Eu as spectral conversion layer was successfully applied on organic solar cells to obtain more available visible phonons with a high photoelectric conversion efficiency(PCE).This work confirms the guidance of molecular dynamics simulation methods for fluorosilicate glasses design.
基金Funded by the National Natural Science Foundation of China(Nos.22068021 and 52064030)the Yunnan Young and Middle-aged Academic and Technical Leaders Reserve Talent Program of China(No.202305AC160064)the Yunnan Major Scientific and Technological Program of China(Nos.202402AB080004,202202AG050011,and 202202AG050007)。
文摘To efficiently address the current high cost associated with preparing pseudo-boehmite from organic aluminum,a low-cost alternative,AlCl_(3),is employed as the raw material.The sol-gel method is utilized,and H_(2)O_(2)is incorporated for the modification of pseudo-boehmite.The modification mechanism is thoroughly investigated through the use of X-ray powder diffractometer,scanning electron microscope,and BET data analysis,as well as molecular dynamics simulations.Under specific conditions(temperature at 80°C,pH=7,and H_(2)O_(2)volume ratios of 0.5:1,1:1,and 2:1),mesoporous pseudo-boehmite is synthesized with a specific surface area of 227 m^(2)/g,a pore volume of 0.281 cm^(3)/g,a pore size of 6.78 nm,and a peptizing index of 99.47%.A novel and innovative methodology for the cost-effective production of high-performance alumina is offered through the approach.
基金the China Sponsorship Council for the scholarship funding(2022GXZ006306)The authors would like to acknowledge contributions from colleagues and support from the Sinopec Company project(No.P23138)the National Natural Science Foundation of China(No.52174047).We also appreciate the editors and the anonymous reviewers for reviewing the manuscript.
文摘Molecular-level interactions between polymeric inhibitors and wax crystals are essential for mitigating wax deposition in crude oils,a major operational and environmental challenge.This study investigates the mechanisms by which specific inhibitors target wax crystals to prevent aggregation.Extracted wax and inhibitor were characterized using gas chromatography,X-ray diffraction,and spectroscopy to determine the molecular structures.The wax primarily comprised of straight-chain nC28 alkanes,while the inhibitor was an ethylene/vinyl acetate copolymer.Rheological tests demonstrated a reduced gelation point upon inhibitor addition.Molecular dynamics(MD)simulations,performed using the COMPASS II force field,revealed interactions at the molecular level.Structural validation of molecules was done through comparative analysis of the experimental infrared and simulated vibrational analysis spectra whereas that of the rhombohedral wax crystal was achieved using the Pawley method,yielding a Profile R-factor of 9.26%.Morphological studies revealed five symmetrically unique facets,with the(110)plane being the fastestgrowing due to its inter-planar distance and attachment energy(-157.25 kcal/mol).Adsorption energy calculations(-180 kcal/mol)confirmed that the inhibitor effectively disrupted crystal growth on the surface by adsorbing its polar section onto the wax surface while repelling the non-polar groups,thereby reducing waxaggregation.
基金support provided by the National Natural Science Foundation of China(Nos.22173051,21829301,21774066),PCSIRT(IRT1257)the College Discipline Innovation and Intelligence Introduction Program(111 Project(B16027)+2 种基金the International Cooperation Base(No.2016D01025)Tianjin International Joint Research and Development Center)P.Zhang acknowledges the financial support provided by NSFC(No.22473024).
文摘Stimuli-responsive polymers capable of rapidly altering their chain conformation in response to external stimuli exhibit broad applica-tion prospects.Experiments have shown that pressure plays a pivotal role in regulating the microscopic chain conformation of polymers in mixed solvents,and one notable finding is that increasing the pressure can lead to the vanishing of the co-nonsolvency effect.However,the mecha-nisms underlying this phenomenon remain unclear.In this study,we systematically investigated the influence of pressure on the co-nonsolvency effect of single-chain and multi-chain homopolymers in binary mixed good-solvent systems using molecular dynamics simulations.Our results show that the co-nonsolvency-induced chain conformation transition and aggregation behavior significantly depend on pressure in allsingle-chain and multi-chain systems.In single-chain systems,at low pressures,the polymer chain maintains a collapsed state over a wide range of co-solvent fractions(x-range)owing to the co-nonsolvency effect.As the pressure increases,the x-range of the collapsed state gradually narrows,ac-companied by a progressive expansion of the chain.In multichain systems,polymer chains assemble into approximately spherical aggregates over a broad x-range at low pressures owing to the co-nonsolvency effect.Increasing the pressure reduces the x-range for forming aggregates and leads to the formation of loose aggregates or even to a state of dispersed chains at some x-range.These findings indicate that increasing the pressure can weaken or even offset the co-nonsolvency effect in some x-range,which is in good agreement with the experimental observations.Quantitative analysis of the radial density distributions and radial distribution functions reveals that,with increasing pressure,(1)the densities of both polymers and co-solvent molecules within aggregates decrease,while that of the solvent molecule increases;and(2)the effective interac-tions between the polymer and the co-solvent weaken,whereas those between the polymer and solvent strengthen.This enhances the incorpo-ration of solvent molecules within the chains,thereby weakening or even suppressing the chain aggregation.Our study not only elucidates the regulatory mechanism of pressure on the microscopic chain conformations and aggregation behaviors of polymers,but also may provide theo-retical guidance for designing smart polymericmaterials based on mixed solvents.
基金supported by the National Natural Science Foundation of China(Grant No.42172308)the Youth Innovation Promotion Association CAS(Grant No.2022331)the Key Research and Development Program of Hubei Province(Grant No.2022BAA036).
文摘To overcome the limitations of microscale experimental techniques and molecular dynamics(MD)simulations,a coarse-grained molecular dynamics(CGMD)method was used to simulate the wetting processes of clay aggregates.Based on the evolution of swelling stress,final dry density,water distribution,and clay arrangements under different target water contents and dry densities,a relationship between the swelling behaviors and microstructures was established.The simulated results showed that when the clay-water well depth was 300 kcal/mol,the basal spacing from CGMD was consistent with the X-ray diffraction(XRD)data.The effect of initial dry density on swelling stress was more pronounced than that of water content.The anisotropic swelling characteristics of the aggregates are related to the proportion of horizontally oriented clay mineral layers.The swelling stress was found to depend on the distribution of tactoids at the microscopic level.At lower initial dry density,the distribution of tactoids was mainly controlled by water distribution.With increase in the bound water content,the basal spacing expanded,and the swelling stresses increased.Free water dominated at higher water contents,and the particles were easily rotated,leading to a decrease in the number of large tactoids.At higher dry densities,the distances between the clay mineral layers decreased,and the movement was limited.When bound water enters the interlayers,there is a significant increase in interparticle repulsive forces,resulting in a greater number of small-sized tactoids.Eventually,a well-defined logarithmic relationship was observed between the swelling stress and the total number of tactoids.These findings contribute to a better understanding of coupled macro-micro swelling behaviors of montmorillonite-based materials,filling a study gap in clay-water interactions on a micro scale.
基金National Natural Science Foundation of China No.22341302.
文摘The crystallization behavior of polymers is significantly influenced by molecular chain length and the dispersion of varying chain lengths.The complexity of studying crystallization arises from the dispersity of polymer materials and the typically slow cooling rates.Recent advancements in fast cooling techniques have rendered the investigation of polymer crystallization at varying cooling rates an attractive area of research;however,a systematic quantitative framework for this process is still lacking.We employ a coarse-grained model for polyvinyl alcohol(CGPVA)in molecular dynamics simulations to study the crystallization of linear polymers with varying chain lengths under variable cooling rates.Monodisperse,bidisperse and polydisperse samples are simulated.We propose two formulae based on a two-phase assumption to fit the exothermal curves obtained during cooling.Based on these formulae,better estimations of crystallization temperatures are obtained and the effects of chain lengths and cooling rates are studied.It is found that the crystallization temperature increases with chain length,similar to the Gibbs-Thomson relation formelting temperature,indicating a strong relation between fast crystallization and glass formation in linear polymers.Extrapolation to the infinitely slow cooling rate provides an easy way in simulations to estimate the equilibrium crystallization temperature.The effective chain lengths of polydisperse and bidisperse samples are found to be the number-averaged chain lengths compared to the weight-averaged ones.The chain length-dependent crystallization exhibits crossover behavior near the entanglement length,indicating the effects of entanglements under fast cooling conditions.The effect of chain length dispersity on crystallization becomes more obvious under fast cooling conditions.
基金supported by the China Scholarship Council(Grant No.202306440152)the CNPC Science and Technology Major Project of the Fourteenth Five-Year Plan(Grant No.2021DJ0101)+1 种基金the Science Foundation of China University of Petroleum,Beijing(Grant No.2462022YXZZ007)the National Natural Science Foundation of China(Grant No.42102145).
文摘As the main factor influencing the flow and preservation of underground fluids,wettability has a profound impact on CO_(2)sequestration(CS).However,the influencing factors and internal interaction mechanisms of shale kerogen wettability remain unclear.In this study,we used molecular dynamics to simulate the influence of temperature,pressure,and salinity on wettability.Furthermore,the results were validated through various methods such as mean square displacement,interaction energy,electrostatic potential energy,hydrogen bonding,van der Waals forces,and electrostatic forces,thereby confirming the reliability of our findings.As temperature increases,water wettability on the surface of kerogen increases.At CO_(2)pressures of 10 and 20 MPa,as the temperature increases,the kerogen wettability changes from CO_(2)wetting to neutral wetting.As the CO_(2)pressure increases,the water wettability on the surface of kerogen weakens.When the pressure is below 7.375 MPa and the temperature is 298 or 313 K,kerogen undergoes a wettability reversal from neutral wetting to CO_(2)wetting.As salinity increases,water wettability weakens.Divalent cations(Mg2+and Ca2+)have a greater impact on wettability than monovalent cations(Na^(+)).Water preferentially adsorbs on N atom positions in kerogen.CO_(2)is more likely to form hydrogen bonds and adsorb on the surface of kerogen than H_(2)O.As the temperature increases,the number of hydrogen bonds between H_(2)O and kerogen gradually increases,while the increase in pressure reduces the number of hydrogen bonds.Although high pressure helps to increase an amount of CS,it increases the permeability of a cap rock,which is not conducive to CS.Therefore,when determining CO_(2)pressure,not only a storage amount but also the storage safety should be considered.This research method and results help optimize the design of CS technology,and have important significance for achieving sustainable development.
基金supported financially by the National Key Research and Development Program(No.2022YFB4602100)to National Natural Science Foundation of China(Nos.51725503 and 52275147).
文摘The impact of chemical short-range order(SRO)and twin boundary(TB)structures on the deformation response under shock compression in CoCrNi medium-entropy alloy(MEA)was investigated using molecular dynamics(MD)simulation.Four microstructural configurations were considered,including random solid solution(RSS),short-range order(SRO),twin boundaries(Twin),and a coupling of SRO and TB(Coup).The results demonstrate that,in comparison to the random MEAs(RSS sample and Twin sam-ple),those with the chemical SRO structure(SRO sample and Coup sample)exhibit a higher shock front zone ratio and an elevated Hugoniot elastic limit(HEL)at a low shock velocity(U_(P)=1200 m/s).This improvement can be attributed to the chemical SRO structure,which increases the energy barrier for dislocation nucleation and propagation.Additionally,pre-existing TBs can also serve as barriers to dislocation movement.In random samples,amorphous clusters tend to initiate from Cr atoms,due to the weak bonding of Cr-Cr pairs.In contrast,in the samples with chemical SRO structure,the increased presence of strong Co-Cr bonding and reduced Cr-Cr bonding effectively raises the activation energy for amor-phization.These local amorphous clusters provide an environment conducive to dislocation nucleation.Consequently,chemical SRO structures lead to increased resistance to dislocation nucleation,where the formation of Shockley Partial(SP)dislocation necessitates longer loading durations,with the nucleation sites situated at a greater distance from the surface.Furthermore,during shock compression in CoCrNi MEAs,SP dislocations preferentially nucleate in the Co-Cr clusters.In conclusion,the presence of chemical SRO structure enhances the shock resistance of the CoCrNi MEAs at lower shock velocities.However,the strengthening effect diminishes with increasing impact velocity and eventually becomes negligible.
基金supported by the Science and Technology Research Project from Education Department of Jilin Province (No. JJKH20231296KJ)the Natural Science Foundation of Science and Technology Department of Jilin Province (Joint Fund Project) (No. YDZJ202201ZYTS340)+9 种基金the Fundamental Research Funds for the Central Universities (No. 2412022ZD013)the Science and Technology Development Plan Project of Jilin Province (Nos. SKL202302030, SKL202402017, 20210204126YY, 20230204113YY, 20240602003RC, 20210402059GH)the National Natural Science Foundation of China (Nos. 22174137, 22322410, 92372102 and 22073094)the Cooperation Funding of Changchun with Chinese Academy of Sciences (No. 22SH13)the Capital Construction Fund Projects within the Budget of Jilin Province (No. 2023C042–5)the University Level Scientific Research Projects of Ordinary Universities in Xinjiang Uygur Autonomous Region (No. 2022YQSN002)the State Key Laboratory of Molecular Engineering of Polymers (Fudan University) (No. K2024–11)the Program for Young Scholars in Regional Development of CASthe essential support of the Network and Computing Center, CIAC, CASthe Computing Center of Jilin Province。
文摘Recent advancements in nanotechnology have spotlighted the catalytic potential of nanozymes, particularly single-atom nanozymes(SANs), which are pivotal for innovations in biosensing and medical diagnostics. Among others, DNA stands out as an ideal biological regulator. Its inherent programmability and interaction capabilities allow it to significantly modulate nanozyme activity. This study delves into the dynamic interplay between DNA and molybdenum-zinc single-atom nanozymes(Mo-Zn SANs). Using molecular dynamics simulations, we uncover how DNA influences the peroxidase-like activities of Mo-Zn SANs, providing a foundational understanding that broadens the application scope of SANs in biosensing.With these insights as a foundation, we developed and demonstrated a model aptasensor for point-ofcare testing(POCT), utilizing a label-free colorimetric approach that leverages DNA-nanozyme interactions to achieve high-sensitivity detection of lysozyme. Our work elucidates the nuanced control DNA exerts over nanozyme functionality and illustrates the application of this molecular mechanism through a smartphone-assisted biosensing platform. This study not only underscores the practical implications of DNA-regulated Mo-Zn SANs in enhancing biosensing platforms, but also highlights the potential of single-atom nanozyme technology to revolutionize diagnostic tools through its inherent versatility and sensitivity.
