In this research,we present a comprehensive investigation on the catalyst screening,reaction mechanism,and electrocatalytic properties of two-dimensional monoatomic metalloporphyrinoid(MPor)materials for the oxygen re...In this research,we present a comprehensive investigation on the catalyst screening,reaction mechanism,and electrocatalytic properties of two-dimensional monoatomic metalloporphyrinoid(MPor)materials for the oxygen reduction reaction(ORR).Through a combination of high-throughput screening,first-principles DFT calculations,and molecular dynamics simulations,we uncovered some promising oxygen reduction catalysts with limiting potentials of 0.60,0.57,0.56 V under acidic medium,and-0.17,-0.20,-0.21 V under basic medium for M=Co,Fe,Mn,respectively.Full reaction pathway search demonstrates that Co Por is a special case with 2e^(–)and 4e^(–)paths under both acidic and basic media,and for Fe Por and Mn Por,only 4e^(–)path is viable.In-depth analyses indicate that the adsorption free energy of OH and limiting potential shows the volcano curve relationship,which can guide the design and optimization of the ORR catalysts.The crystal orbital Hamiltonian population(COHP)between M and O in O_(2)-MPor can well explain why only Co Por has a 2e^(–)path,while other metals do not,because the Co–O bond is much weaker compared to other M–O bonds.Our research will shed some insights on designing efficient ORR catalysts,and stimulate the experimental efforts in this direction.展开更多
The one-dimensional monoatomic lattice chain connected by nonlinear springs is investigated, and the asymptotic solution is obtained through the Lindstedt-Poincar′e perturbation method. The dispersion relation is der...The one-dimensional monoatomic lattice chain connected by nonlinear springs is investigated, and the asymptotic solution is obtained through the Lindstedt-Poincar′e perturbation method. The dispersion relation is derived with the consideration of both the nonlocal and the active control effects. The numerical results show that the nonlocal effect can effectively enhance the frequency in the middle part of the dispersion curve.When the nonlocal effect is strong enough, zero and negative group velocities will be evoked at different points along the dispersion curve, which will provide different ways of transporting energy including the forward-propagation, localization, and backwardpropagation of wavepackets related to the phase velocity. Both the nonlinear effect and the active control can enhance the frequency, but neither of them is able to produce zero or negative group velocities. Specifically, the active control enhances the frequency of the dispersion curve including the point at which the reduced wave number equals zero, and therefore gives birth to a nonzero cutoff frequency and a band gap in the low frequency range. With a combinational adjustment of all these effects, the wave propagation behaviors can be comprehensively controlled, and energy transferring can be readily manipulated in various ways.展开更多
Structures and magnetic properties of transition metal （TM） Fe or Ni monoatomic chains （MACs） encapsulated by a Au （5, 5） nanotube （Fe@Au and Ni@Au） are investigated using the density functional theory （DFT）...Structures and magnetic properties of transition metal （TM） Fe or Ni monoatomic chains （MACs） encapsulated by a Au （5, 5） nanotube （Fe@Au and Ni@Au） are investigated using the density functional theory （DFT）. The calculated results show that both Fe@Au and Ni@Au prefer to adopt ferromagnetic （FM） orders as ground states. In particular, the Fe@Au keeps the magnetic properties of free-standing Fe MAC, indicating that this system may be viewed as a new candidate in electromagnetic devices.展开更多
The surface planarity and asperity removal behavior on atomic scale in an ultrathin water environment were studied for a nanoscale process by molecular dynamics simulation.Monolayer atomic removal is achieved under bo...The surface planarity and asperity removal behavior on atomic scale in an ultrathin water environment were studied for a nanoscale process by molecular dynamics simulation.Monolayer atomic removal is achieved under both noncontact and monoatomic layer contact conditions with different water film thicknesses.The newly formed surface is relatively smooth without deformed layers,and no plastic defects are present in the subsurface.The nanoscale processing is governed by the interatomic adhering action during which the water film transmits the loading forces to the Cu surface and thereby results in the migration and removal of the surface atoms.When the scratching depth≥0.5 nm,the abrasive particle squeezes out the water film from the scratching region and scratches the Cu surface directly.This leads to the formation of trenches and ridges,accumulation of chips ahead of the particles,and generation of dislocations within the Cu substrate.This process is mainly governed by the plowing action,leading to the deterioration of the surface quality.This study makes the"0 nm planarity,0 residual defects,and 0 polishing pressure"in a nanoscale process more achievable and is helpful in understanding the nanoscale removal of materials for developing an ultra-precision manufacture technology.展开更多
Hypersonic flows about space vehicles produce flowfields in thermodynamic non-equilibrium with the local Knudsen numbers Kn which may lie in all the three regimes:continuum,transition and rarefied.Continuum flows can ...Hypersonic flows about space vehicles produce flowfields in thermodynamic non-equilibrium with the local Knudsen numbers Kn which may lie in all the three regimes:continuum,transition and rarefied.Continuum flows can be modeled accurately by solving the Navier–Stokes(NS)equations;however,the flows in transition and rarefied regimes require a kinetic approach such as the direct simulation Monte Carlo(DSMC)method or the solution of the Boltzmann equation.The Boltzmann equation and the general solution approach,using the splitting method,will be introduced in this paper.Details of the method used for solving both the classical Boltzmann equation(CBE)and the generalized Boltzmann equation(GBE)are also provided.The gas mixture discussed in this paper may consist of both monoatomic and diatomic gases.In particular,the method is applied to simulate two of the three primary constituents of air(N_(2),O_(2),and Ar)in a binary mixture at 1:1 density ratio at Mach 2 and 5,with gases in translational,rotational and vibrational non-equilibrium.展开更多
基金financially supported by the National Key Research and Development Program of China(No.2021YFA1600800)the National Natural Science Foundation of China(Nos.22073033,21873032,21673087,and 21903032)+3 种基金the startup fund(Nos.2006013118 and 3004013105)from Huazhong University of Science and Technologythe Fundamental Research Funds for the Central Universities(No.2019kfy RCPY116)the Innovation and Talent Recruitment Base of New Energy Chemistry and Device(No.B21003)support from the Guangdong Basic and Applied Basic Research Foundation(No.2021A1515010382)。
文摘In this research,we present a comprehensive investigation on the catalyst screening,reaction mechanism,and electrocatalytic properties of two-dimensional monoatomic metalloporphyrinoid(MPor)materials for the oxygen reduction reaction(ORR).Through a combination of high-throughput screening,first-principles DFT calculations,and molecular dynamics simulations,we uncovered some promising oxygen reduction catalysts with limiting potentials of 0.60,0.57,0.56 V under acidic medium,and-0.17,-0.20,-0.21 V under basic medium for M=Co,Fe,Mn,respectively.Full reaction pathway search demonstrates that Co Por is a special case with 2e^(–)and 4e^(–)paths under both acidic and basic media,and for Fe Por and Mn Por,only 4e^(–)path is viable.In-depth analyses indicate that the adsorption free energy of OH and limiting potential shows the volcano curve relationship,which can guide the design and optimization of the ORR catalysts.The crystal orbital Hamiltonian population(COHP)between M and O in O_(2)-MPor can well explain why only Co Por has a 2e^(–)path,while other metals do not,because the Co–O bond is much weaker compared to other M–O bonds.Our research will shed some insights on designing efficient ORR catalysts,and stimulate the experimental efforts in this direction.
基金Project supported by the National Natural Science Foundation of China(Nos.11532001and 11621062)the Fundamental Research Funds for the Central Universities of China(No.2016XZZX001-05)
文摘The one-dimensional monoatomic lattice chain connected by nonlinear springs is investigated, and the asymptotic solution is obtained through the Lindstedt-Poincar′e perturbation method. The dispersion relation is derived with the consideration of both the nonlocal and the active control effects. The numerical results show that the nonlocal effect can effectively enhance the frequency in the middle part of the dispersion curve.When the nonlocal effect is strong enough, zero and negative group velocities will be evoked at different points along the dispersion curve, which will provide different ways of transporting energy including the forward-propagation, localization, and backwardpropagation of wavepackets related to the phase velocity. Both the nonlinear effect and the active control can enhance the frequency, but neither of them is able to produce zero or negative group velocities. Specifically, the active control enhances the frequency of the dispersion curve including the point at which the reduced wave number equals zero, and therefore gives birth to a nonzero cutoff frequency and a band gap in the low frequency range. With a combinational adjustment of all these effects, the wave propagation behaviors can be comprehensively controlled, and energy transferring can be readily manipulated in various ways.
基金Project supported by the National Natural Science Foundation of China (Grant No. 11104199)
文摘Structures and magnetic properties of transition metal （TM） Fe or Ni monoatomic chains （MACs） encapsulated by a Au （5, 5） nanotube （Fe@Au and Ni@Au） are investigated using the density functional theory （DFT）. The calculated results show that both Fe@Au and Ni@Au prefer to adopt ferromagnetic （FM） orders as ground states. In particular, the Fe@Au keeps the magnetic properties of free-standing Fe MAC, indicating that this system may be viewed as a new candidate in electromagnetic devices.
基金National Natural Science Foundation of China[Grant numbers 51375364 and 51475359]Natural Science Foundation of Shaanxi Province of China[2014JM6219]。
文摘The surface planarity and asperity removal behavior on atomic scale in an ultrathin water environment were studied for a nanoscale process by molecular dynamics simulation.Monolayer atomic removal is achieved under both noncontact and monoatomic layer contact conditions with different water film thicknesses.The newly formed surface is relatively smooth without deformed layers,and no plastic defects are present in the subsurface.The nanoscale processing is governed by the interatomic adhering action during which the water film transmits the loading forces to the Cu surface and thereby results in the migration and removal of the surface atoms.When the scratching depth≥0.5 nm,the abrasive particle squeezes out the water film from the scratching region and scratches the Cu surface directly.This leads to the formation of trenches and ridges,accumulation of chips ahead of the particles,and generation of dislocations within the Cu substrate.This process is mainly governed by the plowing action,leading to the deterioration of the surface quality.This study makes the"0 nm planarity,0 residual defects,and 0 polishing pressure"in a nanoscale process more achievable and is helpful in understanding the nanoscale removal of materials for developing an ultra-precision manufacture technology.
文摘Hypersonic flows about space vehicles produce flowfields in thermodynamic non-equilibrium with the local Knudsen numbers Kn which may lie in all the three regimes:continuum,transition and rarefied.Continuum flows can be modeled accurately by solving the Navier–Stokes(NS)equations;however,the flows in transition and rarefied regimes require a kinetic approach such as the direct simulation Monte Carlo(DSMC)method or the solution of the Boltzmann equation.The Boltzmann equation and the general solution approach,using the splitting method,will be introduced in this paper.Details of the method used for solving both the classical Boltzmann equation(CBE)and the generalized Boltzmann equation(GBE)are also provided.The gas mixture discussed in this paper may consist of both monoatomic and diatomic gases.In particular,the method is applied to simulate two of the three primary constituents of air(N_(2),O_(2),and Ar)in a binary mixture at 1:1 density ratio at Mach 2 and 5,with gases in translational,rotational and vibrational non-equilibrium.
