Batteries play a critical role in electric vehicles and distributed energy generation.With the growing demand for energy storage solutions,new battery materials and systems are continually being developed.In this proc...Batteries play a critical role in electric vehicles and distributed energy generation.With the growing demand for energy storage solutions,new battery materials and systems are continually being developed.In this process,molecular dynamics(MD)simulations can reveal the microscopic mechanisms of battery processes,thereby boosting the design of batteries.Compared to other MD simulation techniques,the machine learning force field(MLFF)holds the advantages of first-principles accuracy along with large spatial and temporal scale,offering opportunities to uncover new mechanisms in battery systems.This review presents a detailed overview of the fundamental principles and model types of MLFFs,as well as their applications in simulating the structure,transport properties,and chemical reaction properties of bulk battery materials and interfaces.Notably,we emphasize the long-range interaction corrections and constant-potential methods in the model design of MLFFs.Finally,we discuss the challenges and prospects of applying MLFF models in the research of batteries.展开更多
Developing a widely-used reactive force field is meaningful to explore the fundamental reaction mechanism on gas-surface chemical reaction dynamics due to its very high computational efficiency. We here present a stud...Developing a widely-used reactive force field is meaningful to explore the fundamental reaction mechanism on gas-surface chemical reaction dynamics due to its very high computational efficiency. We here present a study of hydrogen and its deuterated molecules dissociation on Pd surfaces based on a full-dimensional potential energy surface （PES） constructed by using a simple second moment approximation reactive force field （SMA RFF）. Although the descriptions of the adsorbate-substrate interaction contain only the dissociation reaction of H2/Pd（111） system, a good transferability of SMA potential energy surface （PES） is shown to investigate the hydrogen dissociation on Pd（100）. Our simulation results show that, the dissociation probabilities of H2 and its deuterated molecules on Pd（111） and Pd（100） surfaces keep non-monotonous variations with respect to the incident energy Ei, which is in good agreement with the previous ab initio molecular dynamics. Furthermore, for the oriented molecules, the dissociation probabilities of the oriented H2 （D2 and T2） molecule have the same orientation dependence behavior as those oriented HD （HT and DT） molecules.展开更多
We present a new method for image deformation. The warping technique provides smooth distortion with intuitive and easy manipulation. Driven by a restrained force field, the input image is deformed gradually and conti...We present a new method for image deformation. The warping technique provides smooth distortion with intuitive and easy manipulation. Driven by a restrained force field, the input image is deformed gradually and continuously. The method allows us to customize the force fields and the region of interest manually through some simple steps. Experimental results demonstrate the effectiveness and convenience of the approach.展开更多
Carbon nanotubes （CNTs） have long been expected to be excellent nanochannels for use in desalination membranes and other bio-inspired human-made channels owing to their experimentally confirmed ultrafast water flow ...Carbon nanotubes （CNTs） have long been expected to be excellent nanochannels for use in desalination membranes and other bio-inspired human-made channels owing to their experimentally confirmed ultrafast water flow and theoretically predicted ion rejection. The correct classical force field potential for the interactions between cations and CNTs plays a cru- cial role in understanding the transport behaviors of ions near and inside the CNT, which is key to these expectations. Here, using density functional theory calculations, we provide classical force field potentials for the interactions of Na＋/hydrated Na＋ with （7,7）, （8,8）, （9,9）, and （10,10）-type CNTs. These potentials can be directly used in current popular classical soft- ware such as nanoscale molecular dynamics （NAMD） by employing the tclBC interface. By incorporating the potential of hydrated cation-g interactions to classical all-atom force fields, we show that the ions will move inside the CNT and accu- mulate, which will block the water flow in wide CNTs. This blockage of water flow in wide CNTs is consistent with recent experimental observations. These results will be helpful for the understanding and design of desalination membranes, new types of nanofluidic channels, nanosensors, and nanoreactors based on CNT platforms.展开更多
The harmonic force field and the vibrational spectrum of nitramide were calculated by using the ab initio gradient program TEXAS at the Hartree-Fock level with a 4-21G basis set. The directly computed theoretical harm...The harmonic force field and the vibrational spectrum of nitramide were calculated by using the ab initio gradient program TEXAS at the Hartree-Fock level with a 4-21G basis set. The directly computed theoretical harmonic force field was scaled by using empirical scale factors which are transferred from other molecules and provided an a priori prediction of fundamental frequencies and intensities. The average deviations between predicted vibrational frequencies of nitramide and experimental IR spectrum in an argon matrix are 63 cm-1 for symmetric vibrations and 41 cm-1 for antisymmetric modes. A new set of scale factors was optimized in this paper. These scale factors reduced the average deviations to 2. 3 cm-1 for symmetric modes and 0. 8 cm-1 for antisymmetric ones. The vibrational spectra of three isotopic derivatives of nitramide were predicted by using the force field resulted from the optimized set of scale factors, which are in good agreement with their experimental data in an argon matrix.展开更多
Neural network force fields have significantly advanced ab initio atomistic simulations across diverse fields.However,their application in the realm of magnetic materials is still in its early stage due to challenges ...Neural network force fields have significantly advanced ab initio atomistic simulations across diverse fields.However,their application in the realm of magnetic materials is still in its early stage due to challenges posed by the subtle magnetic energy landscape and the difficulty of obtaining training data.Here we introduce a data-efficient neural network architecture to represent density functional theory total energy,atomic forces,and magnetic forces as functions of atomic and magnetic structures.Our approach incorporates the principle of equivariance under the three-dimensional Euclidean group into the neural network model.Through systematic experiments on various systems,including monolayer magnets,curved nanotube magnets,and moiré-twisted bilayer magnets of CrI_(3),we showcase the method’s high efficiency and accuracy,as well as exceptional generalization ability.The work creates opportunities for exploring magnetic phenomena in large-scale materials systems.展开更多
The interstellar medium molecule thiocarbonyl thioketen,H_(2)CCS,has several stable isomers and has received considerable attention of as-tronomical observation in recent years.The positions of H,C,and S atoms of thre...The interstellar medium molecule thiocarbonyl thioketen,H_(2)CCS,has several stable isomers and has received considerable attention of as-tronomical observation in recent years.The positions of H,C,and S atoms of three isomers lead to di-verse dipole moments and spectro-scopic constants.The anharmonic force field and spectroscopic con-stants of thiocarbonyl thioketen and its isomers are calculated using MP2,B3LYP,and CCSD(T)methods employing correlation consistent basis sets.Molecule structures,rotational spectroscopic constants,and fundamental frequencies are compared with the available experimental data for thiocarbonyl thioketen.Ro-vibrational interaction constants,anharmonic constants,cubic and quartic force constants are predicted for thiocarbonyl thioketen.In addition,some rotational and vibrational spectroscopic parameters are predict-ed with the same level of theory for thioacetylene,HCCSH,and thiirene,(CH)_(2)S.The predic-tions of these spectroscopic constants are expected to guide the future astronomical observa-tion and high resolution experimental work for C_(2)H_(2)S isomers.展开更多
Large-scale molecular dynamics(MD) simulations of crosslinked epoxy with quantum-level accuracy while capturing complex reactivity is a compelling yet unrealized challenge. In this work, through the construction of a ...Large-scale molecular dynamics(MD) simulations of crosslinked epoxy with quantum-level accuracy while capturing complex reactivity is a compelling yet unrealized challenge. In this work, through the construction of a chemical-environment-directing dataset, a reactive machine learning force field that accurately captures both reactive events and thermos-mechanical properties is developed. The force field achieves energy and force root-mean-square errors of 1.3 meV/atom and 159 meV/A, respectively, and operates approximately 1200 times faster than ab initio molecular dynamics. MD simulations demonstrate excellent predictive capabilities across multiple critical thermos-mechanical properties(radial distribution function, density, and elastic modulus), with results being well consistent with experimental values. In particular, the force field can provide accurate prediction of the bond dissociation energies for typical bonds with a mean absolute error of 7.8 kcal/mol(<8%), which enables the simulation of tensile-induced failure caused by chemical bond breaking. Our work demonstrates the capability of the machine learning force field to handle the extraordinary complexity of crosslinked epoxy systems, providing a valuable blueprint for future development of more generalized reactive force fields applicable to most polymers.展开更多
Bimetallic surfaces play a pivotal role in heterogeneous catalysis,yet their theoretical modeling has long been hindered by the computational chal-lenges of capturing configurational disorder,a critical feature govern...Bimetallic surfaces play a pivotal role in heterogeneous catalysis,yet their theoretical modeling has long been hindered by the computational chal-lenges of capturing configurational disorder,a critical feature governing their catalytic properties.Tradition-al approaches rely on oversimplified ordered surface models or restrict dis-order to a few atomic layers,limiting their predictive power.Here,we Cu_(1-x)Zn_(x)Cu_(1-x)Zn_(x)present an accurate and efficient computational framework that integrates machine learning force fields(MLFFs)with the cluster expansion(CE)method to study configurationally dis-ordered bimetallic surfaces at finite temperatures.We have developed an efficient workflow in which the MLFF is first trained iteratively via an active learning protocol,and then used to generate accurate energetic data for thousands of configurations that enable robust CE model construction.By treating bulk and surface clusters separately,we can build CE models for surface slabs with an arbitrary number of layers.Using as a case study,our CE-based Monte Carlo simulations reveal key structural insights that are relevant to the under-standing of catalytic properties of surfaces.This work demonstrates how MLFF-aided CE can overcome traditional limitations in theoretical modeling of bimetallic surfaces and highlights pathways toward more realistic modeling of heterogeneous catalysts.展开更多
The purpose of this article is to provide,from the perspective of deformable solid mechanics,a correct justification for the expressions of all forces acting on the surface of a ferromagnetic material in a magnetic fi...The purpose of this article is to provide,from the perspective of deformable solid mechanics,a correct justification for the expressions of all forces acting on the surface of a ferromagnetic material in a magnetic field,initiated only by this field.It is shown that the moment of force applied to any closed body surface S,corresponding to the asymmetric part TAof the stress tensor T(denoted as the force pA),balances the mass magnetic moment Lmagacting in the volume V bounded by the surface S.The emergence of the asymmetric part TAof the stress tensor arises as a consequence of a special case within the moment theory of elasticity,the use of which is necessary for accurately describing the behavior of a ferromagnetic material in a magnetic field.The force pa acts in a plane tangential to the surface S at any point,while,in addition to this force,the normal force pn also acts on the body surface.It is shown in the article that the latter force arises as a result of a jump in the normal component of the magnetic field strength appearing at the body surface,and its expression is defined by the mass' s(ponderomotive) magnetic forces Fmag.Usually,this force is introduced based on the Maxwell stress tensor,which is used in the classical electromagnetism to represent the interaction between electromagnetic forces and mechanical momentum.However,as we believe and justify this in the article,such an approach is unacceptable in deformable solid mechanics.展开更多
The rapid development of molecular dynamics(MD)simulations,as well as classical and reactive atomic potentials,has enabled tribologists to gain new insights into lubrication performance at the fundamental level.Howeve...The rapid development of molecular dynamics(MD)simulations,as well as classical and reactive atomic potentials,has enabled tribologists to gain new insights into lubrication performance at the fundamental level.However,the impact of adopted potentials on the rheological properties and tribological performance of hydrocarbons has not been researched adequately.This extensive study analyzed the effects of surface structure,applied load,and force field(FF)on the thin film lubrication of hexadecane.The lubricant film became more solid‐like as the applied load increased.In particular,with increasing applied load,there was an increase in the velocity slip,shear viscosity,and friction.The degree of ordering structure also changed with the applied load but rather insignificantly.It was also significantly dependent on the surface structure.The chosen FFs significantly influenced the lubrication performance,rheological properties,and molecular structure.The adaptive intermolecular reactive empirical bond order(AIREBO)potential resulted in more significant liquid‐like behaviors,and the smallest velocity slip,degree of ordering structure,and shear stress were compared using the optimized potential for liquid simulations of united atoms(OPLS‐UAs),condensed‐phase optimized molecular potential for atomic simulation studies(COMPASS),and ReaxFF.Generally,classical potentials,such as OPLS‐UA and COMPASS,exhibit more solid‐like behavior than reactive potentials do.Furthermore,owing to the solid‐like behavior,the lubricant temperatures obtained from OPLS‐UA and COMPASS were much lower than those obtained from AIREBO and ReaxFF.The increase in shear stress,as well as the decrease in velocity slip with an increase in the surface potential parameterζ,remained conserved for all chosen FFs,thus indicating that the proposed surface potential parameterζfor the COMPASS FF can be verified for a wide range of atomic models.展开更多
Threofuranosyl nucleic acid(TNA)is an analogue of DNA with a shift in the internucleotide linkages from the wild-type 5’-to-3’direction to 3’-to-2.’This alteration leads to higher chemical stability,less reactive ...Threofuranosyl nucleic acid(TNA)is an analogue of DNA with a shift in the internucleotide linkages from the wild-type 5’-to-3’direction to 3’-to-2.’This alteration leads to higher chemical stability,less reactive groups,and lower conformational flexibility.Experimental observations indicate that these characteristic changes are attributable to a minimal perturbation of the interaction network,but the thermodynamic stability of the duplex remains unaltered in the TNA mutation.We applied the equilibrium and nonequilibrium free-energy simulations employing three popular assisted model building with energy refinement(AMBER)force fields for nucleotides to investigate this mutation-dependent behavior in the base flipping from T(DNA)residue to the T-to-TFT mutation(TNA)computationally.The force fields were performed similarly,as described in the base-paired state.However,after exploring the high-energy regions with free-energy simulations,we observed that these three force fields behaved differently.Previous reports conclude that the net-neutral and excess-salt simulations provided similar results.Nonetheless,our free-energy simulation indicated that the presence of excess salt affected the thermodynamic stability.The free-energy barrier along the base-flipping pathway was generally elevated upon the addition of excess salts,but the relative height of the free-energy barriers in DNA and TNA duplexes did not change significantly.This phenomenon emphasizes the importance of adding sufficient salts in the simulation scheme to reproduce the experimental condition.展开更多
Levitated optomechanical systems represent an excellent candidate platform for force and acceleration sensing.We propose a force-sensing protocol utilizing an optically levitated nanoparticle array.In our scheme,N nan...Levitated optomechanical systems represent an excellent candidate platform for force and acceleration sensing.We propose a force-sensing protocol utilizing an optically levitated nanoparticle array.In our scheme,N nanoparticles are trapped in an optical cavity using holographic optical tweezers.An external laser drives the cavity,exciting N cavity modes interacting simultaneously with the N nanoparticles.The optomechanical interaction encodes the information of the force acting on each nanoparticle onto the intracavity photons,which can be detected directly at the output ports of the cavity.Consequently,our protocol enables real-time imaging of a force field.展开更多
It is discovered that the product of the current and the electric field in a PN junction should be regarded as the rate of work(power)done by the electric field force on moving charges(hole current and electron curren...It is discovered that the product of the current and the electric field in a PN junction should be regarded as the rate of work(power)done by the electric field force on moving charges(hole current and electron current),which was previously misinterpreted as solely a Joule heating effect.We clarify that it is exactly the work done by the electric field force on the moving charges to stimulate the emergence of non-equilibrium carriers,which triggers the novel physical phenomena.As regards to Joule heat,we point out that it should be calculated from Ohm’s law,rather than simply from the product of the current and the electric field.Based on this understanding,we conduct thorough discussion on the role of the electric field force in the process of carrier recombination and carrier generation.The thermal effects of carrier recombination and carrier generation followed are incorporated into the thermal equation of energy.The present study shows that the exothermic effect of carrier recombination leads to a temperature rise at the PN interface,while the endothermic effect of carrier generation causes a temperature reduction at the interface.These two opposite effects cause opposite heat flow directions in the PN junction under forward and backward bias voltages,highlighting the significance of managing device heating phenomena in design considerations.Therefore,this study possesses referential significance for the design and tuning on the performance of piezotronic devices.展开更多
Self-assembly of block copolymers(BCPs)is highly intricate and is adsorbing extensive experimental and simulation efforts to reveal it for maximizing structural order and device performances.The coarse-grained(CG)mole...Self-assembly of block copolymers(BCPs)is highly intricate and is adsorbing extensive experimental and simulation efforts to reveal it for maximizing structural order and device performances.The coarse-grained(CG)molecular dynamics(MD)simulation offers a microscopic angle to view the self-assembly of BCPs.Although some molecular details are sacrificed during CG processes,this method exhibits remarkable computational efficiency.In this study,a comprehensive CG model for polystyrene-block-poly(2-vinylpyridine),PS-b-P2VP,one of the most extensively studied BCPs for its high Flory-Huggins interaction parameter,is constructed,with parameters optimized using target values derived from all-atom MD simulations.The CG model precisely coincides with various classical self-assembling morphologies observed in experimental studies,matching the theoretical phase diagrams.Moreover,the conformational asymmetry of the experimental phase diagram is also clearly revealed by our simulation results,and the phase boundaries obtained from simulations are highly consistent with experimental results.The CG model is expected to extend to simulate the self-assembly behaviors of other BCPs in addition to PS-b-P2VP,thus increasing understanding of the microphase separation of BCPs from the molecular level.展开更多
In nature,cavitation bubbles typically appear in clusters,engaging in interactions that create a variety of dynamicmotion patterns.To better understand the behavior ofmultiple bubble collapses and the mechanisms of in...In nature,cavitation bubbles typically appear in clusters,engaging in interactions that create a variety of dynamicmotion patterns.To better understand the behavior ofmultiple bubble collapses and the mechanisms of interbubble interaction,this study employs molecular dynamics simulation combined with a coarse-grained force field.By focusing on collapsemorphology,local density,and pressure,it elucidates how the number and arrangement of bubbles influence the collapse process.The mechanisms behind inter-bubble interactions are also considered.The findings indicate that the collapse speed of unbounded bubbles located in lateral regions is greater than that of the bubbles in the center.Moreover,it is shown that asymmetrical bubble distributions lead to a shorter collapse time overall.展开更多
This paper studies a mirror-assisted rehabilitation training method based on a dual-arm robot,which aims to provide an effective rehabilitation training program for patients with upper limb dysfunction due to stroke o...This paper studies a mirror-assisted rehabilitation training method based on a dual-arm robot,which aims to provide an effective rehabilitation training program for patients with upper limb dysfunction due to stroke or other causes.During the mirror training task scenario,the subjects are visually guided to perform the mirror movement of both arms,and the dual-arm robot is used to facilitate the mirror-assisted rehabilitation from the healthy side to the affected side.Adaptive imped-ance control and force field channel design ensure the stability and safety of the rehabilitation process.In the rehabilitation training,appropriate assistance forces are provided within the channel to correct trajectory deviations,ensuring that the subjects'movement path aligns with the predetermined trajectory.Outside the channel,the superposition of stiffness and correction force fields prevents the subjects from deviating from the predetermined trajectory,thus avoiding injuries.In addition,the adaptive impedance control is capable of dynamically adjusting the impedance parameters according to the real-time state of the subjects,providing a personalized rehabilitation training program.This method significantly enhances both the safety and effectiveness of the rehabilitation training.The experimental results showed that the subjects'motion flexibility and safety were significantly improved during the mirror-assisted rehabilitation training.This study offers a new approach for the future development of rehabilitation robotics with broad application potential.展开更多
Batteries power numerous technolo-gies,yet higher energy density de-mands push lithium cobalt oxide(Li-CoO_(2)referred as LCO)cathodes to higher voltages,triggering unwanted chemical reactions.In this work,we in-vesti...Batteries power numerous technolo-gies,yet higher energy density de-mands push lithium cobalt oxide(Li-CoO_(2)referred as LCO)cathodes to higher voltages,triggering unwanted chemical reactions.In this work,we in-vestigate how carbonate-based elec-trolytes degrade on deeply delithiated LCO surfaces via extensive reactive molecular dynamics simulations.These simulations unveil the forma-tion of characteristic gas products and unstable surface species,which can undermine the cathode structure and reduce battery performance.By examining different solvent composi-tions,the simulations reveal that partial fluorination reduces oxidative degradation and gas evolution,thus offering a route to improve interface stability.Overall,this study provides an atomic-level perspective on preventing unwanted reactions and guiding the design of safer and more robust battery systems for high-voltage applications.展开更多
The short-range repulsive interactions of any force field must be modified to be applicable for high energy atomic collisions because of extremely far from equilibrium state when used in molecular dynamics(MD)simulati...The short-range repulsive interactions of any force field must be modified to be applicable for high energy atomic collisions because of extremely far from equilibrium state when used in molecular dynamics(MD)simulations.In this work,the short-range repulsive interaction of a reactive force field(ReaxFF),describing Fe-Ni-Al alloy system,is well modified by adding a tabulated function form based on Ziegler-Biersack-Littmark(ZBL)potential.The modified interaction covers three ranges,including short range,smooth range,and primordial range.The short range is totally predominated by ZBL potential.The primordial range means the interactions in this range is the as-is ReaxFF with no changes.The smooth range links the short-range ZBL and primordial-range ReaxFF potentials with a taper function.Both energies and forces are guaranteed to be continuous,and qualified to the consistent requirement in LAMMPS.This modified force field is applicable for simulations of energetic particle bombardments and reproducing point defects'booming and recombination effectively.展开更多
Ab initio study of the equilibrium structure, spectroscopy constants, and anharmonic force field for several isotopomers of germanium dichloride （70GeCl2, 72GECl2, and 76GeCl2） have been carried out at the MP2 and C...Ab initio study of the equilibrium structure, spectroscopy constants, and anharmonic force field for several isotopomers of germanium dichloride （70GeCl2, 72GECl2, and 76GeCl2） have been carried out at the MP2 and CCSD（T） levels of theory using cc-pVTZ basis set. The cal- culated geometries, rotational constants, vibration-rotation interaction constants, harmonic frequencies, anharmonic constants, quartic and sextic centrifugal distortion constants, cubic and quartic force constants are compared with experimental data. For small mass differences of the Ge isotopes, the isotopic effects for germanium dichloride are much weaker. The agreements are satisfactory for these two methods, but the deviations of CCSD（T） results are slightly larger than that of MP2, because of CCSD（T）＇s inadequate treatment of electron correlation in hypervalent Cl atom.展开更多
基金funding support from the National Natural Science Foundation of China(92472109,T2325012)the Program for HUST Academic Frontier Youth Team+1 种基金support from the Fundamental Research Funds for the Central Universities(HUST,5003120083)supported by the Postdoctoral Fellowship Program of CPSF(GZC20240532)。
文摘Batteries play a critical role in electric vehicles and distributed energy generation.With the growing demand for energy storage solutions,new battery materials and systems are continually being developed.In this process,molecular dynamics(MD)simulations can reveal the microscopic mechanisms of battery processes,thereby boosting the design of batteries.Compared to other MD simulation techniques,the machine learning force field(MLFF)holds the advantages of first-principles accuracy along with large spatial and temporal scale,offering opportunities to uncover new mechanisms in battery systems.This review presents a detailed overview of the fundamental principles and model types of MLFFs,as well as their applications in simulating the structure,transport properties,and chemical reaction properties of bulk battery materials and interfaces.Notably,we emphasize the long-range interaction corrections and constant-potential methods in the model design of MLFFs.Finally,we discuss the challenges and prospects of applying MLFF models in the research of batteries.
基金This work was supported by the National Natural Science Foundation of China （No.21506053） and Doctoral Scientific Research Foundation Project （KYY15023）.
文摘Developing a widely-used reactive force field is meaningful to explore the fundamental reaction mechanism on gas-surface chemical reaction dynamics due to its very high computational efficiency. We here present a study of hydrogen and its deuterated molecules dissociation on Pd surfaces based on a full-dimensional potential energy surface （PES） constructed by using a simple second moment approximation reactive force field （SMA RFF）. Although the descriptions of the adsorbate-substrate interaction contain only the dissociation reaction of H2/Pd（111） system, a good transferability of SMA potential energy surface （PES） is shown to investigate the hydrogen dissociation on Pd（100）. Our simulation results show that, the dissociation probabilities of H2 and its deuterated molecules on Pd（111） and Pd（100） surfaces keep non-monotonous variations with respect to the incident energy Ei, which is in good agreement with the previous ab initio molecular dynamics. Furthermore, for the oriented molecules, the dissociation probabilities of the oriented H2 （D2 and T2） molecule have the same orientation dependence behavior as those oriented HD （HT and DT） molecules.
文摘We present a new method for image deformation. The warping technique provides smooth distortion with intuitive and easy manipulation. Driven by a restrained force field, the input image is deformed gradually and continuously. The method allows us to customize the force fields and the region of interest manually through some simple steps. Experimental results demonstrate the effectiveness and convenience of the approach.
基金Project supported by the National Science Fund for Outstanding Young Scholars of China(Grant No.11722548)the National Natural Science Foundation of China(Grant Nos.11574339 and 11404361)
文摘Carbon nanotubes （CNTs） have long been expected to be excellent nanochannels for use in desalination membranes and other bio-inspired human-made channels owing to their experimentally confirmed ultrafast water flow and theoretically predicted ion rejection. The correct classical force field potential for the interactions between cations and CNTs plays a cru- cial role in understanding the transport behaviors of ions near and inside the CNT, which is key to these expectations. Here, using density functional theory calculations, we provide classical force field potentials for the interactions of Na＋/hydrated Na＋ with （7,7）, （8,8）, （9,9）, and （10,10）-type CNTs. These potentials can be directly used in current popular classical soft- ware such as nanoscale molecular dynamics （NAMD） by employing the tclBC interface. By incorporating the potential of hydrated cation-g interactions to classical all-atom force fields, we show that the ions will move inside the CNT and accu- mulate, which will block the water flow in wide CNTs. This blockage of water flow in wide CNTs is consistent with recent experimental observations. These results will be helpful for the understanding and design of desalination membranes, new types of nanofluidic channels, nanosensors, and nanoreactors based on CNT platforms.
基金Supported by the National Natural Science Foundation of China
文摘The harmonic force field and the vibrational spectrum of nitramide were calculated by using the ab initio gradient program TEXAS at the Hartree-Fock level with a 4-21G basis set. The directly computed theoretical harmonic force field was scaled by using empirical scale factors which are transferred from other molecules and provided an a priori prediction of fundamental frequencies and intensities. The average deviations between predicted vibrational frequencies of nitramide and experimental IR spectrum in an argon matrix are 63 cm-1 for symmetric vibrations and 41 cm-1 for antisymmetric modes. A new set of scale factors was optimized in this paper. These scale factors reduced the average deviations to 2. 3 cm-1 for symmetric modes and 0. 8 cm-1 for antisymmetric ones. The vibrational spectra of three isotopic derivatives of nitramide were predicted by using the force field resulted from the optimized set of scale factors, which are in good agreement with their experimental data in an argon matrix.
基金supported by the Basic Science Center Project of NSFC(grant no.52388201)the Ministry of Science and Technology of China(grant no.2023YFA1406400)+3 种基金the National Natural Science Foundation of China(grant no.12334003)the National Science Fund for Distinguished Young Scholars(grant no.12025405)the Beijing Advanced Innovation Center for Future Chip(ICFC)the Beijing Advanced Innovation Center for Materials Genome Engineering.
文摘Neural network force fields have significantly advanced ab initio atomistic simulations across diverse fields.However,their application in the realm of magnetic materials is still in its early stage due to challenges posed by the subtle magnetic energy landscape and the difficulty of obtaining training data.Here we introduce a data-efficient neural network architecture to represent density functional theory total energy,atomic forces,and magnetic forces as functions of atomic and magnetic structures.Our approach incorporates the principle of equivariance under the three-dimensional Euclidean group into the neural network model.Through systematic experiments on various systems,including monolayer magnets,curved nanotube magnets,and moiré-twisted bilayer magnets of CrI_(3),we showcase the method’s high efficiency and accuracy,as well as exceptional generalization ability.The work creates opportunities for exploring magnetic phenomena in large-scale materials systems.
基金supported by the Natural Science Foundation of Inner Mongolia(No.2020MS01023).
文摘The interstellar medium molecule thiocarbonyl thioketen,H_(2)CCS,has several stable isomers and has received considerable attention of as-tronomical observation in recent years.The positions of H,C,and S atoms of three isomers lead to di-verse dipole moments and spectro-scopic constants.The anharmonic force field and spectroscopic con-stants of thiocarbonyl thioketen and its isomers are calculated using MP2,B3LYP,and CCSD(T)methods employing correlation consistent basis sets.Molecule structures,rotational spectroscopic constants,and fundamental frequencies are compared with the available experimental data for thiocarbonyl thioketen.Ro-vibrational interaction constants,anharmonic constants,cubic and quartic force constants are predicted for thiocarbonyl thioketen.In addition,some rotational and vibrational spectroscopic parameters are predict-ed with the same level of theory for thioacetylene,HCCSH,and thiirene,(CH)_(2)S.The predic-tions of these spectroscopic constants are expected to guide the future astronomical observa-tion and high resolution experimental work for C_(2)H_(2)S isomers.
基金supported by the National Natural Science Foundation of China(Nos.52303116,52403125)the Natural Science Foundation of Hunan Province(No.2024JJ6461)+2 种基金the Science and Technology Innovation Program of Hunan Province(Nos.2022RC1080,2023RC3006)the Innovation Research Foundation of NUDT(Nos.22-ZZCX-076 and 23-ZZCX-ZZGC-01-10)the Key Research and Development Program of Hunan Province of China(No.2023ZJ1040).
文摘Large-scale molecular dynamics(MD) simulations of crosslinked epoxy with quantum-level accuracy while capturing complex reactivity is a compelling yet unrealized challenge. In this work, through the construction of a chemical-environment-directing dataset, a reactive machine learning force field that accurately captures both reactive events and thermos-mechanical properties is developed. The force field achieves energy and force root-mean-square errors of 1.3 meV/atom and 159 meV/A, respectively, and operates approximately 1200 times faster than ab initio molecular dynamics. MD simulations demonstrate excellent predictive capabilities across multiple critical thermos-mechanical properties(radial distribution function, density, and elastic modulus), with results being well consistent with experimental values. In particular, the force field can provide accurate prediction of the bond dissociation energies for typical bonds with a mean absolute error of 7.8 kcal/mol(<8%), which enables the simulation of tensile-induced failure caused by chemical bond breaking. Our work demonstrates the capability of the machine learning force field to handle the extraordinary complexity of crosslinked epoxy systems, providing a valuable blueprint for future development of more generalized reactive force fields applicable to most polymers.
基金supported by the National Natural Science Foundation of China(No.22273002)the National Key Research and Development Program of China(No.2022YFB4101401).We acknowledge the High-performance Computing Platform of Peking University for providing the computational facility.
文摘Bimetallic surfaces play a pivotal role in heterogeneous catalysis,yet their theoretical modeling has long been hindered by the computational chal-lenges of capturing configurational disorder,a critical feature governing their catalytic properties.Tradition-al approaches rely on oversimplified ordered surface models or restrict dis-order to a few atomic layers,limiting their predictive power.Here,we Cu_(1-x)Zn_(x)Cu_(1-x)Zn_(x)present an accurate and efficient computational framework that integrates machine learning force fields(MLFFs)with the cluster expansion(CE)method to study configurationally dis-ordered bimetallic surfaces at finite temperatures.We have developed an efficient workflow in which the MLFF is first trained iteratively via an active learning protocol,and then used to generate accurate energetic data for thousands of configurations that enable robust CE model construction.By treating bulk and surface clusters separately,we can build CE models for surface slabs with an arbitrary number of layers.Using as a case study,our CE-based Monte Carlo simulations reveal key structural insights that are relevant to the under-standing of catalytic properties of surfaces.This work demonstrates how MLFF-aided CE can overcome traditional limitations in theoretical modeling of bimetallic surfaces and highlights pathways toward more realistic modeling of heterogeneous catalysts.
基金supported by the Ministry of Science and Higher Education of the Russian Federation(No.075-15-2024-535)。
文摘The purpose of this article is to provide,from the perspective of deformable solid mechanics,a correct justification for the expressions of all forces acting on the surface of a ferromagnetic material in a magnetic field,initiated only by this field.It is shown that the moment of force applied to any closed body surface S,corresponding to the asymmetric part TAof the stress tensor T(denoted as the force pA),balances the mass magnetic moment Lmagacting in the volume V bounded by the surface S.The emergence of the asymmetric part TAof the stress tensor arises as a consequence of a special case within the moment theory of elasticity,the use of which is necessary for accurately describing the behavior of a ferromagnetic material in a magnetic field.The force pa acts in a plane tangential to the surface S at any point,while,in addition to this force,the normal force pn also acts on the body surface.It is shown in the article that the latter force arises as a result of a jump in the normal component of the magnetic field strength appearing at the body surface,and its expression is defined by the mass' s(ponderomotive) magnetic forces Fmag.Usually,this force is introduced based on the Maxwell stress tensor,which is used in the classical electromagnetism to represent the interaction between electromagnetic forces and mechanical momentum.However,as we believe and justify this in the article,such an approach is unacceptable in deformable solid mechanics.
基金This project is supported by the Australian Research Council Discovery Projects DP170103173 and Linkage Project LP160101871.
文摘The rapid development of molecular dynamics(MD)simulations,as well as classical and reactive atomic potentials,has enabled tribologists to gain new insights into lubrication performance at the fundamental level.However,the impact of adopted potentials on the rheological properties and tribological performance of hydrocarbons has not been researched adequately.This extensive study analyzed the effects of surface structure,applied load,and force field(FF)on the thin film lubrication of hexadecane.The lubricant film became more solid‐like as the applied load increased.In particular,with increasing applied load,there was an increase in the velocity slip,shear viscosity,and friction.The degree of ordering structure also changed with the applied load but rather insignificantly.It was also significantly dependent on the surface structure.The chosen FFs significantly influenced the lubrication performance,rheological properties,and molecular structure.The adaptive intermolecular reactive empirical bond order(AIREBO)potential resulted in more significant liquid‐like behaviors,and the smallest velocity slip,degree of ordering structure,and shear stress were compared using the optimized potential for liquid simulations of united atoms(OPLS‐UAs),condensed‐phase optimized molecular potential for atomic simulation studies(COMPASS),and ReaxFF.Generally,classical potentials,such as OPLS‐UA and COMPASS,exhibit more solid‐like behavior than reactive potentials do.Furthermore,owing to the solid‐like behavior,the lubricant temperatures obtained from OPLS‐UA and COMPASS were much lower than those obtained from AIREBO and ReaxFF.The increase in shear stress,as well as the decrease in velocity slip with an increase in the surface potential parameterζ,remained conserved for all chosen FFs,thus indicating that the proposed surface potential parameterζfor the COMPASS FF can be verified for a wide range of atomic models.
基金supported financially by the National Key R&D Program of China(grant no.2016YFA0501700)National Natural Science Foundation of China(grant nos.21433004,31700646,and 21933010),and NYU Global Seed Grant.
文摘Threofuranosyl nucleic acid(TNA)is an analogue of DNA with a shift in the internucleotide linkages from the wild-type 5’-to-3’direction to 3’-to-2.’This alteration leads to higher chemical stability,less reactive groups,and lower conformational flexibility.Experimental observations indicate that these characteristic changes are attributable to a minimal perturbation of the interaction network,but the thermodynamic stability of the duplex remains unaltered in the TNA mutation.We applied the equilibrium and nonequilibrium free-energy simulations employing three popular assisted model building with energy refinement(AMBER)force fields for nucleotides to investigate this mutation-dependent behavior in the base flipping from T(DNA)residue to the T-to-TFT mutation(TNA)computationally.The force fields were performed similarly,as described in the base-paired state.However,after exploring the high-energy regions with free-energy simulations,we observed that these three force fields behaved differently.Previous reports conclude that the net-neutral and excess-salt simulations provided similar results.Nonetheless,our free-energy simulation indicated that the presence of excess salt affected the thermodynamic stability.The free-energy barrier along the base-flipping pathway was generally elevated upon the addition of excess salts,but the relative height of the free-energy barriers in DNA and TNA duplexes did not change significantly.This phenomenon emphasizes the importance of adding sufficient salts in the simulation scheme to reproduce the experimental condition.
基金the useful discussion.This work is supported by the Natural Science Foundation of Zhe-jiang Province(Grant No.LQ22A040010)the National Natural Science Foundation of China(Grant Nos.12304545 and 12204434).
文摘Levitated optomechanical systems represent an excellent candidate platform for force and acceleration sensing.We propose a force-sensing protocol utilizing an optically levitated nanoparticle array.In our scheme,N nanoparticles are trapped in an optical cavity using holographic optical tweezers.An external laser drives the cavity,exciting N cavity modes interacting simultaneously with the N nanoparticles.The optomechanical interaction encodes the information of the force acting on each nanoparticle onto the intracavity photons,which can be detected directly at the output ports of the cavity.Consequently,our protocol enables real-time imaging of a force field.
基金the National Natural Science Foundation of China(Nos.12232007,11972164,and 12102141)。
文摘It is discovered that the product of the current and the electric field in a PN junction should be regarded as the rate of work(power)done by the electric field force on moving charges(hole current and electron current),which was previously misinterpreted as solely a Joule heating effect.We clarify that it is exactly the work done by the electric field force on the moving charges to stimulate the emergence of non-equilibrium carriers,which triggers the novel physical phenomena.As regards to Joule heat,we point out that it should be calculated from Ohm’s law,rather than simply from the product of the current and the electric field.Based on this understanding,we conduct thorough discussion on the role of the electric field force in the process of carrier recombination and carrier generation.The thermal effects of carrier recombination and carrier generation followed are incorporated into the thermal equation of energy.The present study shows that the exothermic effect of carrier recombination leads to a temperature rise at the PN interface,while the endothermic effect of carrier generation causes a temperature reduction at the interface.These two opposite effects cause opposite heat flow directions in the PN junction under forward and backward bias voltages,highlighting the significance of managing device heating phenomena in design considerations.Therefore,this study possesses referential significance for the design and tuning on the performance of piezotronic devices.
基金supported by the National Natural Science Foundation of China(22438005,22108117).
文摘Self-assembly of block copolymers(BCPs)is highly intricate and is adsorbing extensive experimental and simulation efforts to reveal it for maximizing structural order and device performances.The coarse-grained(CG)molecular dynamics(MD)simulation offers a microscopic angle to view the self-assembly of BCPs.Although some molecular details are sacrificed during CG processes,this method exhibits remarkable computational efficiency.In this study,a comprehensive CG model for polystyrene-block-poly(2-vinylpyridine),PS-b-P2VP,one of the most extensively studied BCPs for its high Flory-Huggins interaction parameter,is constructed,with parameters optimized using target values derived from all-atom MD simulations.The CG model precisely coincides with various classical self-assembling morphologies observed in experimental studies,matching the theoretical phase diagrams.Moreover,the conformational asymmetry of the experimental phase diagram is also clearly revealed by our simulation results,and the phase boundaries obtained from simulations are highly consistent with experimental results.The CG model is expected to extend to simulate the self-assembly behaviors of other BCPs in addition to PS-b-P2VP,thus increasing understanding of the microphase separation of BCPs from the molecular level.
基金funded by the Natural Science Foundation of China[U20A20292]Shandong Province Science andTechnology SMES InnovationAbility Improvement Project[2023TSGC0005]China Postdoctoral Science Foundation[2024M752697].
文摘In nature,cavitation bubbles typically appear in clusters,engaging in interactions that create a variety of dynamicmotion patterns.To better understand the behavior ofmultiple bubble collapses and the mechanisms of interbubble interaction,this study employs molecular dynamics simulation combined with a coarse-grained force field.By focusing on collapsemorphology,local density,and pressure,it elucidates how the number and arrangement of bubbles influence the collapse process.The mechanisms behind inter-bubble interactions are also considered.The findings indicate that the collapse speed of unbounded bubbles located in lateral regions is greater than that of the bubbles in the center.Moreover,it is shown that asymmetrical bubble distributions lead to a shorter collapse time overall.
基金supported by the Shanghai Municipal Economic and Information Commission(Project No.240404).
文摘This paper studies a mirror-assisted rehabilitation training method based on a dual-arm robot,which aims to provide an effective rehabilitation training program for patients with upper limb dysfunction due to stroke or other causes.During the mirror training task scenario,the subjects are visually guided to perform the mirror movement of both arms,and the dual-arm robot is used to facilitate the mirror-assisted rehabilitation from the healthy side to the affected side.Adaptive imped-ance control and force field channel design ensure the stability and safety of the rehabilitation process.In the rehabilitation training,appropriate assistance forces are provided within the channel to correct trajectory deviations,ensuring that the subjects'movement path aligns with the predetermined trajectory.Outside the channel,the superposition of stiffness and correction force fields prevents the subjects from deviating from the predetermined trajectory,thus avoiding injuries.In addition,the adaptive impedance control is capable of dynamically adjusting the impedance parameters according to the real-time state of the subjects,providing a personalized rehabilitation training program.This method significantly enhances both the safety and effectiveness of the rehabilitation training.The experimental results showed that the subjects'motion flexibility and safety were significantly improved during the mirror-assisted rehabilitation training.This study offers a new approach for the future development of rehabilitation robotics with broad application potential.
基金support from the National Key Research and Development Program of China(No.2022YFB2502200)the Natural Science Foun-dation of Jiangsu Province(BK20230065)+2 种基金the Key Laboratory of Functional Nano&Soft Materials,the Collaborative Innovation Center of Suzhou Nano Sci-ence&Technology,the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)the 111 Project,Joint International Research Laboratory of Carbon-Based Functional Materials and Devices,Yue Liu acknowledges support from the National Natural Science Foundation of China(22303058)the Natural Science Foundation of Jiangsu Province(BK20230475).
文摘Batteries power numerous technolo-gies,yet higher energy density de-mands push lithium cobalt oxide(Li-CoO_(2)referred as LCO)cathodes to higher voltages,triggering unwanted chemical reactions.In this work,we in-vestigate how carbonate-based elec-trolytes degrade on deeply delithiated LCO surfaces via extensive reactive molecular dynamics simulations.These simulations unveil the forma-tion of characteristic gas products and unstable surface species,which can undermine the cathode structure and reduce battery performance.By examining different solvent composi-tions,the simulations reveal that partial fluorination reduces oxidative degradation and gas evolution,thus offering a route to improve interface stability.Overall,this study provides an atomic-level perspective on preventing unwanted reactions and guiding the design of safer and more robust battery systems for high-voltage applications.
基金Project supported by the National Magnetic Confinement Fusion Energy Research Project(Grant Nos.2019YFE03120003,2018YFE0307100,and 2017YFE0302500)the National Natural Science Foundation of China(Grant Nos.11975034,11921006,12004010,and U20B2025).
文摘The short-range repulsive interactions of any force field must be modified to be applicable for high energy atomic collisions because of extremely far from equilibrium state when used in molecular dynamics(MD)simulations.In this work,the short-range repulsive interaction of a reactive force field(ReaxFF),describing Fe-Ni-Al alloy system,is well modified by adding a tabulated function form based on Ziegler-Biersack-Littmark(ZBL)potential.The modified interaction covers three ranges,including short range,smooth range,and primordial range.The short range is totally predominated by ZBL potential.The primordial range means the interactions in this range is the as-is ReaxFF with no changes.The smooth range links the short-range ZBL and primordial-range ReaxFF potentials with a taper function.Both energies and forces are guaranteed to be continuous,and qualified to the consistent requirement in LAMMPS.This modified force field is applicable for simulations of energetic particle bombardments and reproducing point defects'booming and recombination effectively.
文摘Ab initio study of the equilibrium structure, spectroscopy constants, and anharmonic force field for several isotopomers of germanium dichloride （70GeCl2, 72GECl2, and 76GeCl2） have been carried out at the MP2 and CCSD（T） levels of theory using cc-pVTZ basis set. The cal- culated geometries, rotational constants, vibration-rotation interaction constants, harmonic frequencies, anharmonic constants, quartic and sextic centrifugal distortion constants, cubic and quartic force constants are compared with experimental data. For small mass differences of the Ge isotopes, the isotopic effects for germanium dichloride are much weaker. The agreements are satisfactory for these two methods, but the deviations of CCSD（T） results are slightly larger than that of MP2, because of CCSD（T）＇s inadequate treatment of electron correlation in hypervalent Cl atom.
