Mechanical properties and electronic structure of MgCu2, Mg2 Ca and MgZn2 phases were investigated by means of first principles calculations from CASTEP program based on density functional theory（DFT）. The calculate...Mechanical properties and electronic structure of MgCu2, Mg2 Ca and MgZn2 phases were investigated by means of first principles calculations from CASTEP program based on density functional theory（DFT）. The calculated lattice parameters are in good agreement with the experimental and literature values. The calculated heat of formation and cohesive energies showed that MgCu2 has the strongest alloying ability and structural stability. Elastic constants of MgCu2, Mg2 Ca and MgZn2 were calculated, and the bulk moduli, shear moduli, elastic moduli and Poisson ratio were derived. The calculated results show that MgCu2, Mg2 Ca and MgZn2 are all ductile phases. Among the three phases, MgCu2 has the strongest stiffness and the plasticity of MgZn2 phase is the best. Melting points of the three phases were predicted using cohesive energy and elastic constants. Density of states（DOS）, Mulliken population, electron occupation number and charge density difference were discussed. Finally, Debye temperature was calculated and discussed.展开更多
The present work concerns the study of the dielectric relaxation of dielectric oil based on Lagenaria siceraria (calabash) seeds. Dielectric spectroscopy was used to measure the loss angle, the dielectric constant and...The present work concerns the study of the dielectric relaxation of dielectric oil based on Lagenaria siceraria (calabash) seeds. Dielectric spectroscopy was used to measure the loss angle, the dielectric constant and the electrical modulus. Three relaxation processes in calabash oil were identified. It was also found that the relative permittivity decreases with increasing temperature and frequency. A study of the imaginary part of the electrical modulus was done and revealed a relaxation process at low frequencies. At higher frequencies, the dielectric relaxation is thermally activated. The increase in temperature leads to a decrease in the relaxation rate. The result obtained indicates that relaxation type is not of the Debye type in the high-frequency region. The Cole-Cole model of the imaginary part of the permittivity as a function of its real part in calabash oil for different temperatures was drawn and analyzed. It shows the existence of a negative temperature coefficient of resistance in the fluid and helps identifying a relaxation process in the conductivity of the sample studied. It highlights the presence of Debye relaxation which characterizes the presence of an abnormal dispersion of the dielectric constant over a frequency range. Calabash seed oil exhibits better dielectric constant (relative permittivity) compared to other oils.展开更多
Within the framework of the quasiharmonic approximation, the thermodynamics and elastic properties of Ta, including phonon density of states （DOS）, equation of state, linear thermal expansion coefficient, entropy, e...Within the framework of the quasiharmonic approximation, the thermodynamics and elastic properties of Ta, including phonon density of states （DOS）, equation of state, linear thermal expansion coefficient, entropy, enthalpy, heat capacity, elastic constants, bulk modulus, shear modulus, Young＇s modulus, microhardness, and sound velocity, are studied using the first-principles projector-augmented wave method. The vibrational contribution to Helmholtz free energy is evaluated from the first-principles phonon DOS and the Debye model. The thermal electronic contribution to Helmholtz free energy is estimated from the integration over the electronic DOS. By comparing the experimental results with the calculation results from the first-principles and the Debye model, it is found that the thermodynamic properties of Ta are depicted well by the first-principles. The elastic properties of Ta from the first-principles are consistent with the available experimental data.展开更多
In this work,the impacts of pressure on the structural,mechanical,thermodynamic and electronic properties of typical Pt_(3)M(M=Al,Co,Hf,Sc,Y,Zr)compounds were investigated systematically by the firstprinciples density...In this work,the impacts of pressure on the structural,mechanical,thermodynamic and electronic properties of typical Pt_(3)M(M=Al,Co,Hf,Sc,Y,Zr)compounds were investigated systematically by the firstprinciples density function theory calculations.The calculated lattice parameters,volume and elastic constants of Pt_(3)M compounds are in good agreement with available experimental and calculation values.With the increase in pressure,the lattice parameters and volume of Pt_(3)M compounds decrease,while the elastic constants,bulk modulus,shear modulus and Young’s modulus increase.The variations in Pugh’s ratio and Poisson’s ratio indicate that these Pt_(3)M compounds are mechanically stable and ductile.The mechanical anisotropy of these Pt_(3)M compounds is enhanced by rising pressure.Thermodynamic analysis indicates that sound velocity and Debye temperature increase with the increase in stress.The charge distribution does not change obviously,implying that no phase transition occurs in the range of 0-100 GPa.展开更多
We demonstrate an all-optical strategy for realizing spherical three-dimensional(3D)super-resolution(∼λ3/22)spot arrays of pure longitudinal magnetization by exploiting a 4πoptical microscopic setup with two high n...We demonstrate an all-optical strategy for realizing spherical three-dimensional(3D)super-resolution(∼λ3/22)spot arrays of pure longitudinal magnetization by exploiting a 4πoptical microscopic setup with two high numerical aperture(NA)objective lenses,which focus and interfere two modulated vectorial beams.Multiple phase filters(MPFs)are designed via an analytical approach derived from the vectorial Debye diffraction theory to modulate the two circularly polarized beams.The system is tailored to constructively interfere the longitudinal magnetization components,while simultaneously destructively interfering the azimuthal ones.As a result,the magnetization field is not only purely longitudinal but also super-resolved in all three dimensions.Furthermore,the MPFs can be designed analytically to control the number and locations of the super-resolved magnetization spots to produce both uniform and nonuniform arrays in a 3D volume.Thus,an all-optical control of all the properties of light-induced magnetization spot arrays has been demonstrated for the first time.These results open up broad applications in magnetic-optical devices such as confocal and multifocal magnetic resonance microscopy,3D ultrahigh-density magneto-optic memory,and light-induced magneto-lithography.展开更多
The shot-range interaction and the atomic anharmonic vibration are both considered, and then the analytic functions of the Debye temperature, the specific capacity and the thermal conductivity of graphene with the tem...The shot-range interaction and the atomic anharmonic vibration are both considered, and then the analytic functions of the Debye temperature, the specific capacity and the thermal conductivity of graphene with the temperature are obtained. The influence of anharmonic vibration on these thermal physical properties is also investigated. Some theoretical results are given. If only the harmonic approximation is considered, the Debye temperature of the graphene is unrelated to the temperature. If the anharmonic terms are considered, it increases slowly with the increasing temperature. The molar heat capacity of the graphene increases nonlinearly with the increasing temperature. The mean free path of phonons and the thermal conductivity of the graphene decrease nonlinearly with the increasing temperature. The relative changes of the Debye temperature, the specific heat capacity and the thermal conductivity caused by the anharmonic terms increase with the increasing temperature. The anharmonic effect of atomic vibration becomes more significant under higher temperature.展开更多
Studies on electro-osmotic flows of various types of fluids in microchannel are of great importance owing to their multifold applications in the transport of liquids, particularly when the ionized liquid flows with re...Studies on electro-osmotic flows of various types of fluids in microchannel are of great importance owing to their multifold applications in the transport of liquids, particularly when the ionized liquid flows with respect to a charged surface in the presence of an external electric field. In the case of viscoelastic fluids, the volumetric flow rate differs significantly from that of Newtonian fluids, even when the flow takes place under the same pressure gradient and the same electric field. With this end in view, this paper is devoted to a study concerning the flow pattern of an electro-osmotic flow in a porous microchannel, which is under the action of an alternating electric field. The influence of various rheological and electro-osmotic parameters, e.g., the Reynolds number, Debye-Huckel parameter, shape factor and fluid viscoelasticity on the kinematics of the fluid, has been investigated for a secondgrade viscoelastic fluid. The problem is first treated by using analytical methods, but the quantitative estimates are obtained numerically with the help of the software MATHEMATICA. The results presented here are applicable to the cases where the channel height is much greater than the thickness of the electrical double layer comprising the Stern and diffuse layers. The study reveals that a larger value of the Debye-Huckel parameter creates sharper profile near the wall and also that the velocity of electro-osmotic flow increases as the permeability of the porous microchannel is enhanced. The study further shows that the electro-osmotic flow dominates at lower values of Reynolds number. The results presented here will be quite useful to validate the observations of experimental investigations on the characteristics of electro-osmotic flows and also the results of complex numerical models that are necessary to deal with more realistic situations, where electro-osmotic flows come into the picture, as in blood flow in the micro-circulatory system subject to an electric field.展开更多
The static electric dipole polarizabilities of the ground state and n ≤ 3 excited states of a lithium atom embedded in a weekly coupled plasma environment are investigated as a function of the plasma screening radium...The static electric dipole polarizabilities of the ground state and n ≤ 3 excited states of a lithium atom embedded in a weekly coupled plasma environment are investigated as a function of the plasma screening radium. The plasma screening of the Coulomb interaction is described by the Debye-Hiickel potential and the interaction between the valence electron and the atomic core is described by a model potential. The electron energies and wave functions for both the bound and continuum states are calculated by solving the SchrSdinger equation numerically using the symplectic integrator. The oscillator strengths, partial-wave, and total static dipole polarizabilities of the ground state and n ≤ 3 excited states of the lithium atom are calculated. Comparison of present results with those of other authors, when available, is made. The results for the 2s ground state demonstrated that the oscillator strengths and the static dipole polarizabilities from np orbitals do not always increase or decrease with the plasma screening effect increasing, unlike that for hydrogen-like ions, especially for 2s→3p transition there is a zero value for both the oscillator strength and the static dipole polarizability for screening length D = 10.3106a0, which is associated with the Cooper minima.展开更多
Hot,dense plasmas exhibit screened Coulomb interactions,resulting from the collective effects of correlated many-particle interactions.In the lowest particle correlation order(pair-wise correlations),the interaction b...Hot,dense plasmas exhibit screened Coulomb interactions,resulting from the collective effects of correlated many-particle interactions.In the lowest particle correlation order(pair-wise correlations),the interaction between charged plasma particles reduces to the DebyeeHu¨ckel(Yukawa-type)potential,characterized by the Debye screening length.Due to the importance of Coulomb interaction screening in dense laboratory and astrophysical plasmas,hundreds of theoretical investigations have been carried out in the past few decades on the plasma screening effects on the electronic structure of atoms and their collision processes employing the DebyeeHu¨ckel screening model.The present article aims at providing a comprehensive review of the recent studies in atomic physics in Debye plasmas.Specifically,the work on atomic electronic structure,photon excitation and ionization,electron/positron impact excitation and ionization,and excitation,ionization and charge transfer of ion-atom/ion collisions will be reviewed.展开更多
First-principles calculations based on density functional theory were perfo rmed to investigate the cohesive energies,elastic modulus,Debye temperatures,thermal conductivities and density of states of La_(2-x)Yb_(x)Zr...First-principles calculations based on density functional theory were perfo rmed to investigate the cohesive energies,elastic modulus,Debye temperatures,thermal conductivities and density of states of La_(2-x)Yb_(x)Zr_(2)O_(7),La_(2)Zr_(2-x)Ce_(x)O_(7)and La_(2-x)Yb_(x)Zr_(2-x)Ce_(x)O_(7)(x=0.00,0.25,0.50,0.75,1.00)ceramics.The results show that doping Yb~(3+)or Ce~(4+)into La_(2)Zr_(2)O_(7)reduces its elastic modulus,thermal conductivity and Debye temperature.Compared with La_(2-x)Yb_(x)Zr_(2)O_(7)(x≠0.00),La_(2)Zr_(2-x)Ce_(x)O_(7)compounds have better ductility and lower Debye te mperature.The Debye temperature values of La_(2)Zr_(2-x)Ce_(x)O_(7)(x≠0.00)co mpounds are in the range of 485.0-511.5 K.Among all components,the fluorite-type La_(2-x)Yb_(x)Zr_(2-x)Ce_(x)O_(7)(x=0.75,1.00)compounds exhibit better mechanical and thermophysical properties,and their thermal conductivity values are only 1.213-1.246 W/(m·K)(1073 K),which are 14.5%-16.7%lower than that of the pure La_(2)Zr_(2)O_(7).Thus,our findings open an entirely new avenue for TBCs.展开更多
The equilibrium lattice parameter, heat capacity, thermal expansion coefficient and bulk modulus of Ni2MnGa Heusler alloy are successfully obtained using the first-principles plane-wave pseudopotential （PW-PP） metho...The equilibrium lattice parameter, heat capacity, thermal expansion coefficient and bulk modulus of Ni2MnGa Heusler alloy are successfully obtained using the first-principles plane-wave pseudopotential （PW-PP） method as well as the quasi-harmonic Debye model. We analyse the relationship between bulk modulus B and temperature T up to 800 K and obtain the relationship between bulk modulus B and pressure at different temperatures. It is found that the bulk modulus B increases monotonically with increasing pressure and decreases with increasing temperature. The pressure dependence of heat capacity Cv and thermal expansion α at various temperatures are also analysed. Finally, the Debye temperature of Ni2MnGa is determined from the non-equilibrium Gibbs function. Our calculated results are in excellent agreement with the experimental data.展开更多
High-temperature superconductivity in ceramic oxides is a new technology in which advances are occurring at a rapid pace. Here, the author describes some properties of a new nano crystalline ceramic Type II supercondu...High-temperature superconductivity in ceramic oxides is a new technology in which advances are occurring at a rapid pace. Here, the author describes some properties of a new nano crystalline ceramic Type II superconductor, PbSrCaCuO. Type II superconductors are usually made of metal alloys or complex oxide ceramics. The PSCCO perovskite phase structure was prepared by the conventional solid state reaction technique. In order to show the viability of the proposed method, super-conducting powder was prepared in special furnace. The sample was analyzed by X-ray Diffraction (XRD), Particle size determination, SEM and EDX. The comparison of XRD results with JCPDS files confirmed the orthorhombic structure of the sample with a ≠ b ≠ c and α = β = γ = 90°. Scanning electron microscopy (SEM) studies revealed that its particle size is in the nanometer range. It also confirmed the calculated value of particle size from Debye Scherrer’s formula. EDX spectrum shows the elements of the sample. X-ray instrumental peak broadening analysis was used to evaluate the size and lattice strain by the Williamson-Hall Plot method.展开更多
In the present paper, we report on the results of various thermodynamic properties of 3C-SiC at high pressure and temperature using first principles calculations. We use the plane-wave pseudopotential density function...In the present paper, we report on the results of various thermodynamic properties of 3C-SiC at high pressure and temperature using first principles calculations. We use the plane-wave pseudopotential density functional theory as im- plemented in Quantum ESPRESSO code for calculating various cohesive properties in ambient condition. Further, ionic motion at a finite temperature is taken into account using the quasiharmonic Debye model. The calculated thermody- namic properties, phonon dispersion curves, and phonon densities of states at different temperatures and structural phase transitions at high pressures are found to be in good agreement with experimental and other theoretical results.展开更多
In dielectrics and semiconductors, a plasma model of the generation and slip of dislocations is considered, where under shock loads in a generalized space of rectangular pulses an alternating field forms a distributio...In dielectrics and semiconductors, a plasma model of the generation and slip of dislocations is considered, where under shock loads in a generalized space of rectangular pulses an alternating field forms a distribution of pairs of photoelectrons and cations;these electrons with velocities <em>V<sub>e</sub></em> create <em>δ</em>-collisions with cold plasma from free electrons and holes with masses <em>m<sub>e</sub></em> and <em>m<sub>h</sub></em> (<em>m<sub>h</sub></em> <span style="white-space:normal;"><span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">≫</span></span> </span></span><em>m<sub>e</sub></em>), they emit and absorb longitudinal electron plasma waves whose phase velocities <em>w<sub>pw</sub></em> / <em>k<sub>pw</sub></em> are close to or are equal to the velocities <em>V<sub>e</sub></em>, while the frequencies <em>w<sub>pw</sub></em> and wave numbers <em>k<sub>pw</sub></em> of the wave packet of plasma waves are complex, the short-wave components <img src="Edit_3da65014-7fd8-4799-bcf1-02d90028f4e0.bmp" alt="" /> of this wave packet at <em>k<sub>pw</sub></em> <span style="white-space:normal;"><span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">⋅</span></span></span> </span><em>a<sub>e </sub></em><span style="white-space:nowrap;">≫ </span>1 (<em>a<sub>e</sub></em> -Debye screening radius) decay in the core linear defect, and its long-wavelength components <img src="Edit_4481889b-5097-4d26-9019-b0322f5ff8d0.bmp" alt="" /> propagate in the region of the medium surrounding the core of the defect at <em>k<sub>pw</sub></em> <span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">⋅</span></span></span> <em>a<sub>e</sub></em> <span style="white-space:nowrap;"><<span style="white-space:nowrap;"><span style="white-space:nowrap;">≅</span></span></span> 1. When a defect is generated, the distribution of cations under the influence of 展开更多
The paper shows that work in a quantum system is quantized with energy;the quantum work is equivalent to the highest eigenenergy(the Debye energy)of the system and the superlubricity of solids is derived from the quan...The paper shows that work in a quantum system is quantized with energy;the quantum work is equivalent to the highest eigenenergy(the Debye energy)of the system and the superlubricity of solids is derived from the quantum work.The prerequisite for the superlubricity is that the lateral force at contact surfaces in sliding is less than the Debye force so that the phonon of the solids is not excited.展开更多
Uncontrollable dendrite growth resulting from the non-uniform lithium ion(Li^(+))flux and volume expansion in lithium metal(Li)negative electrode leads to rapid performance degradation and serious safety problems of l...Uncontrollable dendrite growth resulting from the non-uniform lithium ion(Li^(+))flux and volume expansion in lithium metal(Li)negative electrode leads to rapid performance degradation and serious safety problems of lithium metal batteries.Although N-containing functional groups in carbon materials are reported to be effective to homogenize the Li^(+)flux,the effective interaction distance between lithium ions and N-containing groups should be relatively small(down to nanometer scale)according to the Debye length law.Thus,it is necessary to carefully design the microstructure of N-containing carbon materials to make the most of their roles in regulating the Li^(+)flux.In this work,porous carbon nitride microspheres(PCNMs)with abundant nanopores have been synthesized and utilized to fabricate a uniform lithiophilic coating layer having hybrid pores of both the nano-and micrometer scales on the Cu/Li foil.Physically,the three-dimensional(3D)porous framework is favorable for absorbing volume changes and guiding Li growth.Chemically,this coating layer can render a suitable interaction distance to effectively homogenize the Li^(+)flux and contribute to establishing a robust and stable solid electrolyte interphase(SEI)layer with Li-F,Li-N,and Li-O-rich contents based on the Debye length law.Such a physical-chemical synergic regulation strategy using PCNMs can lead to dendrite-free Li plating,resulting in a low nucleation overpotential and stable Li plating/stripping cycling performance in both the Li||Cu and the Li||Li symmetric cells.Meanwhile,a full cell using the PCNM coated Li foil negative electrode and a LiFePO4 positive electrode has delivered a high capacity retention of~80%after more than 200 cycles at 1 C and achieved a remarkable rate capability.The pouch cell fabricated by pairing the PCNM coated Li foil negative electrode with a NCM 811 positive electrode has retained~73%of the initial capacity after 150 cycles at 0.2 C.展开更多
We investigate the structural and elastic properties of γ TiAl under high pressures using the norm-conservingpseudopotentials within the local density approximation(LDA)in the frame of density functional theory.The c...We investigate the structural and elastic properties of γ TiAl under high pressures using the norm-conservingpseudopotentials within the local density approximation(LDA)in the frame of density functional theory.The calculatedpressure dependence of the elastic constants is in excellent agreement with the experimental results.The elastic constantsand anisotropy as a function of applied pressure are presented.Through the quasi-harmonic Debye model,we alsoinvestigate the thermodynamic properties of γ TiAl.展开更多
The realization of rapid and unidirectional single-file wate^molecule flow in nanochannels has posed a challenge to date. Here, we report unprecedentedly rapid unidirectional single-file water-molecule flow under a tr...The realization of rapid and unidirectional single-file wate^molecule flow in nanochannels has posed a challenge to date. Here, we report unprecedentedly rapid unidirectional single-file water-molecule flow under a translational terahertz electric field, which is obtained by developing a Debye double- relaxation theory. In addition, we demonstrate that all the single-file molecules undergo both stable translation and rotation, behaving like high-speed train wheels moving along a railway track. Inde- pendent molecular dynamics simulations help to confirm these theoretical results. The mechanism involves the resonant relaxation dynamics of H and O atoms. Purther, an experimental demon- stration is suggested and discussed. This work has implications for the design of high-efficiency nanochannels or smaller nanomachines in the field of nanotechnology, and the findings also aid in the understanding and control of water flow across biological nanochannels in biology-related research.展开更多
基金Project(2013201018)supported by Scientific and Technological Project of Liaoning Province,China
文摘Mechanical properties and electronic structure of MgCu2, Mg2 Ca and MgZn2 phases were investigated by means of first principles calculations from CASTEP program based on density functional theory（DFT）. The calculated lattice parameters are in good agreement with the experimental and literature values. The calculated heat of formation and cohesive energies showed that MgCu2 has the strongest alloying ability and structural stability. Elastic constants of MgCu2, Mg2 Ca and MgZn2 were calculated, and the bulk moduli, shear moduli, elastic moduli and Poisson ratio were derived. The calculated results show that MgCu2, Mg2 Ca and MgZn2 are all ductile phases. Among the three phases, MgCu2 has the strongest stiffness and the plasticity of MgZn2 phase is the best. Melting points of the three phases were predicted using cohesive energy and elastic constants. Density of states（DOS）, Mulliken population, electron occupation number and charge density difference were discussed. Finally, Debye temperature was calculated and discussed.
文摘The present work concerns the study of the dielectric relaxation of dielectric oil based on Lagenaria siceraria (calabash) seeds. Dielectric spectroscopy was used to measure the loss angle, the dielectric constant and the electrical modulus. Three relaxation processes in calabash oil were identified. It was also found that the relative permittivity decreases with increasing temperature and frequency. A study of the imaginary part of the electrical modulus was done and revealed a relaxation process at low frequencies. At higher frequencies, the dielectric relaxation is thermally activated. The increase in temperature leads to a decrease in the relaxation rate. The result obtained indicates that relaxation type is not of the Debye type in the high-frequency region. The Cole-Cole model of the imaginary part of the permittivity as a function of its real part in calabash oil for different temperatures was drawn and analyzed. It shows the existence of a negative temperature coefficient of resistance in the fluid and helps identifying a relaxation process in the conductivity of the sample studied. It highlights the presence of Debye relaxation which characterizes the presence of an abnormal dispersion of the dielectric constant over a frequency range. Calabash seed oil exhibits better dielectric constant (relative permittivity) compared to other oils.
基金Project supported by the Foundation of Key Laboratory of National Defense Science and Technology for Shock Wave and Detonation Physics and the Science and Research Foundation of Sichuan Educational Committee,China(Grant No.09ZC048)
文摘Within the framework of the quasiharmonic approximation, the thermodynamics and elastic properties of Ta, including phonon density of states （DOS）, equation of state, linear thermal expansion coefficient, entropy, enthalpy, heat capacity, elastic constants, bulk modulus, shear modulus, Young＇s modulus, microhardness, and sound velocity, are studied using the first-principles projector-augmented wave method. The vibrational contribution to Helmholtz free energy is evaluated from the first-principles phonon DOS and the Debye model. The thermal electronic contribution to Helmholtz free energy is estimated from the integration over the electronic DOS. By comparing the experimental results with the calculation results from the first-principles and the Debye model, it is found that the thermodynamic properties of Ta are depicted well by the first-principles. The elastic properties of Ta from the first-principles are consistent with the available experimental data.
基金financially supported by the National Natural Science Foundation of China(No.51801179)Yunnan Science and Technology Projects(Nos.2019ZE001-1,2018ZE001,2018ZE021 and 2018IC058)Yunnan Applied Basic Research Projects(Nos.2018FB083 and 2018FD011)。
文摘In this work,the impacts of pressure on the structural,mechanical,thermodynamic and electronic properties of typical Pt_(3)M(M=Al,Co,Hf,Sc,Y,Zr)compounds were investigated systematically by the firstprinciples density function theory calculations.The calculated lattice parameters,volume and elastic constants of Pt_(3)M compounds are in good agreement with available experimental and calculation values.With the increase in pressure,the lattice parameters and volume of Pt_(3)M compounds decrease,while the elastic constants,bulk modulus,shear modulus and Young’s modulus increase.The variations in Pugh’s ratio and Poisson’s ratio indicate that these Pt_(3)M compounds are mechanically stable and ductile.The mechanical anisotropy of these Pt_(3)M compounds is enhanced by rising pressure.Thermodynamic analysis indicates that sound velocity and Debye temperature increase with the increase in stress.The charge distribution does not change obviously,implying that no phase transition occurs in the range of 0-100 GPa.
基金supported by the National Natural Science Foundation of China(Nos.61575139,11474077,11374079,11604236,51602213,61605136 and 11404283)Fundamental&advanced research projects of Chongqing,China(cstc2013jcyjC00001)+3 种基金the Youth Foundation of the Taiyuan University of Technology(No.2015QN066)the Youth Science Foundation of the Taiyuan Institute of Technology(No.2015LQ14)the Science and Technology Program of Guangdong(2016A040403124)the Shanxi Scholarship Council of China(No.2013-037).
文摘We demonstrate an all-optical strategy for realizing spherical three-dimensional(3D)super-resolution(∼λ3/22)spot arrays of pure longitudinal magnetization by exploiting a 4πoptical microscopic setup with two high numerical aperture(NA)objective lenses,which focus and interfere two modulated vectorial beams.Multiple phase filters(MPFs)are designed via an analytical approach derived from the vectorial Debye diffraction theory to modulate the two circularly polarized beams.The system is tailored to constructively interfere the longitudinal magnetization components,while simultaneously destructively interfering the azimuthal ones.As a result,the magnetization field is not only purely longitudinal but also super-resolved in all three dimensions.Furthermore,the MPFs can be designed analytically to control the number and locations of the super-resolved magnetization spots to produce both uniform and nonuniform arrays in a 3D volume.Thus,an all-optical control of all the properties of light-induced magnetization spot arrays has been demonstrated for the first time.These results open up broad applications in magnetic-optical devices such as confocal and multifocal magnetic resonance microscopy,3D ultrahigh-density magneto-optic memory,and light-induced magneto-lithography.
基金Supported by the National Natural Science Foundation of China under Grant No 11574253the Scientific and Technological Research Program of Chongqing Municipal Education Commission under Grant Nos KJ1601111 and KJ1601118the Basic and Frontier Research Projects of Chongqing under Grant No cstc2015jcyjA40054
文摘The shot-range interaction and the atomic anharmonic vibration are both considered, and then the analytic functions of the Debye temperature, the specific capacity and the thermal conductivity of graphene with the temperature are obtained. The influence of anharmonic vibration on these thermal physical properties is also investigated. Some theoretical results are given. If only the harmonic approximation is considered, the Debye temperature of the graphene is unrelated to the temperature. If the anharmonic terms are considered, it increases slowly with the increasing temperature. The molar heat capacity of the graphene increases nonlinearly with the increasing temperature. The mean free path of phonons and the thermal conductivity of the graphene decrease nonlinearly with the increasing temperature. The relative changes of the Debye temperature, the specific heat capacity and the thermal conductivity caused by the anharmonic terms increase with the increasing temperature. The anharmonic effect of atomic vibration becomes more significant under higher temperature.
文摘Studies on electro-osmotic flows of various types of fluids in microchannel are of great importance owing to their multifold applications in the transport of liquids, particularly when the ionized liquid flows with respect to a charged surface in the presence of an external electric field. In the case of viscoelastic fluids, the volumetric flow rate differs significantly from that of Newtonian fluids, even when the flow takes place under the same pressure gradient and the same electric field. With this end in view, this paper is devoted to a study concerning the flow pattern of an electro-osmotic flow in a porous microchannel, which is under the action of an alternating electric field. The influence of various rheological and electro-osmotic parameters, e.g., the Reynolds number, Debye-Huckel parameter, shape factor and fluid viscoelasticity on the kinematics of the fluid, has been investigated for a secondgrade viscoelastic fluid. The problem is first treated by using analytical methods, but the quantitative estimates are obtained numerically with the help of the software MATHEMATICA. The results presented here are applicable to the cases where the channel height is much greater than the thickness of the electrical double layer comprising the Stern and diffuse layers. The study reveals that a larger value of the Debye-Huckel parameter creates sharper profile near the wall and also that the velocity of electro-osmotic flow increases as the permeability of the porous microchannel is enhanced. The study further shows that the electro-osmotic flow dominates at lower values of Reynolds number. The results presented here will be quite useful to validate the observations of experimental investigations on the characteristics of electro-osmotic flows and also the results of complex numerical models that are necessary to deal with more realistic situations, where electro-osmotic flows come into the picture, as in blood flow in the micro-circulatory system subject to an electric field.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11005049,10979007,and 10974021)
文摘The static electric dipole polarizabilities of the ground state and n ≤ 3 excited states of a lithium atom embedded in a weekly coupled plasma environment are investigated as a function of the plasma screening radium. The plasma screening of the Coulomb interaction is described by the Debye-Hiickel potential and the interaction between the valence electron and the atomic core is described by a model potential. The electron energies and wave functions for both the bound and continuum states are calculated by solving the SchrSdinger equation numerically using the symplectic integrator. The oscillator strengths, partial-wave, and total static dipole polarizabilities of the ground state and n ≤ 3 excited states of the lithium atom are calculated. Comparison of present results with those of other authors, when available, is made. The results for the 2s ground state demonstrated that the oscillator strengths and the static dipole polarizabilities from np orbitals do not always increase or decrease with the plasma screening effect increasing, unlike that for hydrogen-like ions, especially for 2s→3p transition there is a zero value for both the oscillator strength and the static dipole polarizability for screening length D = 10.3106a0, which is associated with the Cooper minima.
基金Wang was supported by the National Basic Research Program of China(Grant No.2013CB922200).
文摘Hot,dense plasmas exhibit screened Coulomb interactions,resulting from the collective effects of correlated many-particle interactions.In the lowest particle correlation order(pair-wise correlations),the interaction between charged plasma particles reduces to the DebyeeHu¨ckel(Yukawa-type)potential,characterized by the Debye screening length.Due to the importance of Coulomb interaction screening in dense laboratory and astrophysical plasmas,hundreds of theoretical investigations have been carried out in the past few decades on the plasma screening effects on the electronic structure of atoms and their collision processes employing the DebyeeHu¨ckel screening model.The present article aims at providing a comprehensive review of the recent studies in atomic physics in Debye plasmas.Specifically,the work on atomic electronic structure,photon excitation and ionization,electron/positron impact excitation and ionization,and excitation,ionization and charge transfer of ion-atom/ion collisions will be reviewed.
基金Project supported by the National Natural Science Foundation of China(52071172,51361026)the Key Research&Developement Plan of Jiangxi Province(20203BBE53046,20181ACH80009)+1 种基金the China Postdoctoral Science Foundation(2017M620576)the Aeronautical Science Foundation of China(2017ZE56015)。
文摘First-principles calculations based on density functional theory were perfo rmed to investigate the cohesive energies,elastic modulus,Debye temperatures,thermal conductivities and density of states of La_(2-x)Yb_(x)Zr_(2)O_(7),La_(2)Zr_(2-x)Ce_(x)O_(7)and La_(2-x)Yb_(x)Zr_(2-x)Ce_(x)O_(7)(x=0.00,0.25,0.50,0.75,1.00)ceramics.The results show that doping Yb~(3+)or Ce~(4+)into La_(2)Zr_(2)O_(7)reduces its elastic modulus,thermal conductivity and Debye temperature.Compared with La_(2-x)Yb_(x)Zr_(2)O_(7)(x≠0.00),La_(2)Zr_(2-x)Ce_(x)O_(7)compounds have better ductility and lower Debye te mperature.The Debye temperature values of La_(2)Zr_(2-x)Ce_(x)O_(7)(x≠0.00)co mpounds are in the range of 485.0-511.5 K.Among all components,the fluorite-type La_(2-x)Yb_(x)Zr_(2-x)Ce_(x)O_(7)(x=0.75,1.00)compounds exhibit better mechanical and thermophysical properties,and their thermal conductivity values are only 1.213-1.246 W/(m·K)(1073 K),which are 14.5%-16.7%lower than that of the pure La_(2)Zr_(2)O_(7).Thus,our findings open an entirely new avenue for TBCs.
基金supported by the National Natural Science Foundation of China (Grant No 60777012)the Program for Science &Technology Innovation Talents in Universities of Henan Province of China (Grant No 2008HASTIT008) the Science and Technology Foundation of Henan Province, China (Grant No 082300410050)
文摘The equilibrium lattice parameter, heat capacity, thermal expansion coefficient and bulk modulus of Ni2MnGa Heusler alloy are successfully obtained using the first-principles plane-wave pseudopotential （PW-PP） method as well as the quasi-harmonic Debye model. We analyse the relationship between bulk modulus B and temperature T up to 800 K and obtain the relationship between bulk modulus B and pressure at different temperatures. It is found that the bulk modulus B increases monotonically with increasing pressure and decreases with increasing temperature. The pressure dependence of heat capacity Cv and thermal expansion α at various temperatures are also analysed. Finally, the Debye temperature of Ni2MnGa is determined from the non-equilibrium Gibbs function. Our calculated results are in excellent agreement with the experimental data.
文摘High-temperature superconductivity in ceramic oxides is a new technology in which advances are occurring at a rapid pace. Here, the author describes some properties of a new nano crystalline ceramic Type II superconductor, PbSrCaCuO. Type II superconductors are usually made of metal alloys or complex oxide ceramics. The PSCCO perovskite phase structure was prepared by the conventional solid state reaction technique. In order to show the viability of the proposed method, super-conducting powder was prepared in special furnace. The sample was analyzed by X-ray Diffraction (XRD), Particle size determination, SEM and EDX. The comparison of XRD results with JCPDS files confirmed the orthorhombic structure of the sample with a ≠ b ≠ c and α = β = γ = 90°. Scanning electron microscopy (SEM) studies revealed that its particle size is in the nanometer range. It also confirmed the calculated value of particle size from Debye Scherrer’s formula. EDX spectrum shows the elements of the sample. X-ray instrumental peak broadening analysis was used to evaluate the size and lattice strain by the Williamson-Hall Plot method.
文摘In the present paper, we report on the results of various thermodynamic properties of 3C-SiC at high pressure and temperature using first principles calculations. We use the plane-wave pseudopotential density functional theory as im- plemented in Quantum ESPRESSO code for calculating various cohesive properties in ambient condition. Further, ionic motion at a finite temperature is taken into account using the quasiharmonic Debye model. The calculated thermody- namic properties, phonon dispersion curves, and phonon densities of states at different temperatures and structural phase transitions at high pressures are found to be in good agreement with experimental and other theoretical results.
文摘In dielectrics and semiconductors, a plasma model of the generation and slip of dislocations is considered, where under shock loads in a generalized space of rectangular pulses an alternating field forms a distribution of pairs of photoelectrons and cations;these electrons with velocities <em>V<sub>e</sub></em> create <em>δ</em>-collisions with cold plasma from free electrons and holes with masses <em>m<sub>e</sub></em> and <em>m<sub>h</sub></em> (<em>m<sub>h</sub></em> <span style="white-space:normal;"><span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">≫</span></span> </span></span><em>m<sub>e</sub></em>), they emit and absorb longitudinal electron plasma waves whose phase velocities <em>w<sub>pw</sub></em> / <em>k<sub>pw</sub></em> are close to or are equal to the velocities <em>V<sub>e</sub></em>, while the frequencies <em>w<sub>pw</sub></em> and wave numbers <em>k<sub>pw</sub></em> of the wave packet of plasma waves are complex, the short-wave components <img src="Edit_3da65014-7fd8-4799-bcf1-02d90028f4e0.bmp" alt="" /> of this wave packet at <em>k<sub>pw</sub></em> <span style="white-space:normal;"><span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">⋅</span></span></span> </span><em>a<sub>e </sub></em><span style="white-space:nowrap;">≫ </span>1 (<em>a<sub>e</sub></em> -Debye screening radius) decay in the core linear defect, and its long-wavelength components <img src="Edit_4481889b-5097-4d26-9019-b0322f5ff8d0.bmp" alt="" /> propagate in the region of the medium surrounding the core of the defect at <em>k<sub>pw</sub></em> <span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">⋅</span></span></span> <em>a<sub>e</sub></em> <span style="white-space:nowrap;"><<span style="white-space:nowrap;"><span style="white-space:nowrap;">≅</span></span></span> 1. When a defect is generated, the distribution of cations under the influence of
文摘The paper shows that work in a quantum system is quantized with energy;the quantum work is equivalent to the highest eigenenergy(the Debye energy)of the system and the superlubricity of solids is derived from the quantum work.The prerequisite for the superlubricity is that the lateral force at contact surfaces in sliding is less than the Debye force so that the phonon of the solids is not excited.
基金This work was supported by the National Key R&D Program of China(No.2016YFF0204302)the National Natural Science Foundation of China(Nos.51872305 and 52001320)S&T Innovation 2025 Major Special Programme of Ningbo(No.2018B10081)。
文摘Uncontrollable dendrite growth resulting from the non-uniform lithium ion(Li^(+))flux and volume expansion in lithium metal(Li)negative electrode leads to rapid performance degradation and serious safety problems of lithium metal batteries.Although N-containing functional groups in carbon materials are reported to be effective to homogenize the Li^(+)flux,the effective interaction distance between lithium ions and N-containing groups should be relatively small(down to nanometer scale)according to the Debye length law.Thus,it is necessary to carefully design the microstructure of N-containing carbon materials to make the most of their roles in regulating the Li^(+)flux.In this work,porous carbon nitride microspheres(PCNMs)with abundant nanopores have been synthesized and utilized to fabricate a uniform lithiophilic coating layer having hybrid pores of both the nano-and micrometer scales on the Cu/Li foil.Physically,the three-dimensional(3D)porous framework is favorable for absorbing volume changes and guiding Li growth.Chemically,this coating layer can render a suitable interaction distance to effectively homogenize the Li^(+)flux and contribute to establishing a robust and stable solid electrolyte interphase(SEI)layer with Li-F,Li-N,and Li-O-rich contents based on the Debye length law.Such a physical-chemical synergic regulation strategy using PCNMs can lead to dendrite-free Li plating,resulting in a low nucleation overpotential and stable Li plating/stripping cycling performance in both the Li||Cu and the Li||Li symmetric cells.Meanwhile,a full cell using the PCNM coated Li foil negative electrode and a LiFePO4 positive electrode has delivered a high capacity retention of~80%after more than 200 cycles at 1 C and achieved a remarkable rate capability.The pouch cell fabricated by pairing the PCNM coated Li foil negative electrode with a NCM 811 positive electrode has retained~73%of the initial capacity after 150 cycles at 0.2 C.
基金National Natural Science Foundation of China under Grant Nos.10376021 and 10274055the Research Fund for the Doctoral Program of High Education of China under Grant No.20020610001
文摘We investigate the structural and elastic properties of γ TiAl under high pressures using the norm-conservingpseudopotentials within the local density approximation(LDA)in the frame of density functional theory.The calculatedpressure dependence of the elastic constants is in excellent agreement with the experimental results.The elastic constantsand anisotropy as a function of applied pressure are presented.Through the quasi-harmonic Debye model,we alsoinvestigate the thermodynamic properties of γ TiAl.
基金We acknowledge the financial support by the National Natural Science Foundation of China under Grant No. 11222544, the Fok Ying Tung Education Foundation under Grant No. 131008, and the Program for New Century Excellent Talents in University （NCET-12-0121）. The computational resources uti- lized in this research were provided by Shanghai Supercomputer Center.
文摘The realization of rapid and unidirectional single-file wate^molecule flow in nanochannels has posed a challenge to date. Here, we report unprecedentedly rapid unidirectional single-file water-molecule flow under a translational terahertz electric field, which is obtained by developing a Debye double- relaxation theory. In addition, we demonstrate that all the single-file molecules undergo both stable translation and rotation, behaving like high-speed train wheels moving along a railway track. Inde- pendent molecular dynamics simulations help to confirm these theoretical results. The mechanism involves the resonant relaxation dynamics of H and O atoms. Purther, an experimental demon- stration is suggested and discussed. This work has implications for the design of high-efficiency nanochannels or smaller nanomachines in the field of nanotechnology, and the findings also aid in the understanding and control of water flow across biological nanochannels in biology-related research.
