By use of self-consistent field Xα scattered-wave (SCF-Xα-SW) method, the electronic structure was calculated for four models of Ti4Al14X (X=Al, Fe, Ni and Cu) clusters. The Ti4Al14X cluster was developed based on L...By use of self-consistent field Xα scattered-wave (SCF-Xα-SW) method, the electronic structure was calculated for four models of Ti4Al14X (X=Al, Fe, Ni and Cu) clusters. The Ti4Al14X cluster was developed based on L12 Al3Ti-base intermetallic compound. The results are presented using the density of states (DOS) and one-electron properties, such as relative binding tendency between the atom and the model cluster, and hybrid bonding tendency between the alloying element and the host atoms. By comparing the four models of Ti4Al14X cluster, the effect of the Fe, Ni or Cu atom on the physical properties of Al3Ti-based L12 intermetallic compounds is analyzed. The results indicate that the addition of the Fe, Ni or Cu atom intensifies the relative binding tendency between Ti atom and Ti4Al14X cluster. It was found that the Fermi level (EF) lies in a maximum in the DOS for Ti4Al14Al cluster; on the contrary, the EF comes near a minimum tn the DOS for Ti4Al14X (X=Fe, Ni and Cu) cluster. Thus the L12 crystal structure for binary Al3Ti alloy is unstable, and the addition of the Fe, Ni or Cu atom to Al3Ti is benefical to stabilize L12 crystal structure. The calculation also shows that the Fe, Ni or Cu atom strengthens the hybrid bonding tendency between the central atom and the host atoms for Ti4Al14X cluster and thereby may lead to the constriction of the lattice of Al3Ti-base intermetallic compounds.展开更多
In this work, we choose Nb3Al/Nb3Sn as a new test case for flat/steep band model of superconductivity. Based on the density functional theory in the generalized gradient approximation, the electronic structure of Nb3A...In this work, we choose Nb3Al/Nb3Sn as a new test case for flat/steep band model of superconductivity. Based on the density functional theory in the generalized gradient approximation, the electronic structure of Nb3Al/ Nb3Sn has been studied. The obtained results agree well with those of the earlier studies and show clearly fiat bands around the Fermi level. The steep bands as characterized in this work locate around the M point in the first Brillouin zone. The obtained results reveal that Nb3Al/Nb3Sn fits more to the ＂Flat/steep＂ band model than to the van-Hove singularity scenario. The fiat/steep band condition for superconductivity implies a different thermodynamic behavior of superconductors other than that predicted from the conventional BCS theory. This observation sets up an indicator for selecting a suitable superconductor when its large-scale industrial use is needed, for example, in superconducting maglev system or ITER project.展开更多
Using our recently published electron’s charge electromagnetic flux manifold fiber model of the electron, described by analytical method and numerical simulations, we show how the fine structure constant is embedded ...Using our recently published electron’s charge electromagnetic flux manifold fiber model of the electron, described by analytical method and numerical simulations, we show how the fine structure constant is embedded as a geometrical proportionality constant in three dimensional space of its charge manifold and how this dictates the first QED term one-loop contribution of its anomalous magnetic moment making for the first time a connection of its intrinsic characteristics with physical geometrical dimensions and therefore demonstrating that the physical electron charge cannot be dimensionless. We show that the fine structure constant (FSC) α, and anomalous magnetic moment α<sub>μ</sub> of the electron is related to the sphericity of its charge distribution which is not perfectly spherical and thus has a shape, and therefore its self-confined charge possesses measurable physical dimensions. We also explain why these are not yet able to be measured by past and current experiments and how possible we could succeed.展开更多
In the present study, two models of atom occupation in LaNi4Co were put forward and corresponding valence electron structures （VESs） of these two models were investigated according to empirical electron theory （EET...In the present study, two models of atom occupation in LaNi4Co were put forward and corresponding valence electron structures （VESs） of these two models were investigated according to empirical electron theory （EET） of solids and molecules. Results demonstrate that the VES-concerned hardness factor （FH） of LaNi4Co is lower than that of LaNi5, so LaNi4Co has lower hardness, higher plasticity and improved anti-pulverization ability. In the mean time, the difference of the equilibrium hydrogen pressure between LaNiaCo and LaNi5 was analyzed in the electronic level. The analysis shows that the strength of the weakest bond net in octahedron lattice interstices of LaNi4Co is much lower than that in LaNis; consequently, LaNi4Co＇s bond net easily deforms to accommodate hydrogen so that LaNi4Co has lower equilibrium hydrogen pressure in comparison with LaNis. The results can provide some theory guide on the design of hydrogen storage alloys.展开更多
We evaluate three of the quantum constants of hydrogen, the electron, e<sup>-</sup>, the Bohr radius, a<sub>0</sub>, and the Rydberg constants, , as natural unit frequency equivalents, v. This ...We evaluate three of the quantum constants of hydrogen, the electron, e<sup>-</sup>, the Bohr radius, a<sub>0</sub>, and the Rydberg constants, , as natural unit frequency equivalents, v. This is equivalent to Planck’s constant, h, the speed of light, c, and the electron charge, e, all scaled to 1 similar in concept to the Hartree atomic, and Planck units. These frequency ratios are analyzed as fundamental coupling constants. We recognize that the ratio of the product of 8π<sup>2</sup>, the v<sub>e</sub><sub>-</sub> times the v<sub>R</sub> divided by v<sub>a</sub><sub>0</sub> squared equals 1. This is a power law defining Planck’s constant in a dimensionless domain as 1. We also find that all of the possible dimensionless and dimensioned ratios correspond to other constants or classic relationships, and are systematically inter-related by multiple power laws to the fine structure constant, α;and the geometric factors 2, and π. One is related to an angular momentum scaled by Planck’s constant, and another is the kinetic energy law. There are harmonic sinusoidal relationships based on 2π circle geometry. In the dimensionless domain, α is equivalent to the free space constant of permeability, and its reciprocal to permittivity. If any two quanta are known, all of the others can be derived within power laws. This demonstrates that 8π2 represents the logical geometric conversion factor that links the Euclid geometric factors/three dimensional space, and the quantum domain. We conclude that the relative scale and organization of many of the fundamental constants even beyond hydrogen are related to a unified power law system defined by only three physical quanta of v<sub>e</sub><sub>-</sub>, v<sub>R</sub>, and v<sub>a</sub><sub>0</sub>.展开更多
A model of liquid ZA27 cast alloy is established according to molecular dynamics theory and an atomic structural model of co-existent a phase and liquid is also presented by means of computer programming. Recursion me...A model of liquid ZA27 cast alloy is established according to molecular dynamics theory and an atomic structural model of co-existent a phase and liquid is also presented by means of computer programming. Recursion method is adopted to calculate the electronic structure of RE (rare earth) in grains and around phase boundaries respectively. The calculation shows that RE is more stable around phase boundaries than in grains, which explains the fact that the solution of RE in a phase is less, and RE mainly aggregates in front of phase boundary. The calculations of bonding order integrals also show that RE in front of phases hardly solidify onto the grain surfaces as active element so as to prevent grains growth and refine the grains. As a result, the modification mechanism of RE may be explained from the view of electronic structure.展开更多
Intercalation provides to the host materials a means for controlled variation of many physical/chemical properties and dominates the reactions in metal‐ion batteries.Of particular interest is the graphite intercalati...Intercalation provides to the host materials a means for controlled variation of many physical/chemical properties and dominates the reactions in metal‐ion batteries.Of particular interest is the graphite intercalation compounds with intriguing staging structures,which however are still unclear,especially in their nanostructure and dynamic transition mechanism.Herein,the nature of the staging structure and evolution of the lithium(Li)‐intercalated graphite was revealed by cryogenic‐transmission electron microscopy and other methods at the nanoscale.The intercalated Li‐ions distribute unevenly,generating local stress and dislocations in the graphitic structure.Each staging compound is found macroscopically ordered but microscopically inhomogeneous,exhibiting a localized‐domains structural model.Our findings uncover the correlation between the long‐range ordered structure and short‐range domains,refresh the insights on the staging structure and transition of Li‐intercalated/deintercalated graphite,and provide effective ways to enhance the reaction kinetic in rechargeable batteries by defect engineering.展开更多
Transient electronics are an emerging class of electronics with the unique characteristic to completely dissolve within a programmed period of time. Since no harmful byproducts are released, these electronics can be u...Transient electronics are an emerging class of electronics with the unique characteristic to completely dissolve within a programmed period of time. Since no harmful byproducts are released, these electronics can be used in the human body as a diagnostic tool, for instance, or they can be used as environmentally friendly alternatives to existing electronics which disintegrate when exposed to water. Thus, the most crucial aspect of transient electronics is their ability to disintegrate in a practical manner and a review of the literature on this topic is essential for understanding the current capabilities of transient electronics and areas of future research. In the past, only partial dissolution of transient electronics was possible, however, total dissolution has been achieved with a recent discovery that silicon nanomembrane undergoes hydrolysis. The use of single- and multi-layered structures has also been explored as a way to extend the lifetime of the electronics. Analytical models have been developed to study the dissolution of various functional materials as well as the devices constructed from this set of functional materials and these models prove to be useful in the design of the transient electronics.展开更多
A new modulated structure consisting of periodic （1120） stacking faults （SFs） in the α-Fe2O3 nanowires （NWs） formed by the thermal oxidation of Fe foils is reported, using a combination of high-resolution trans...A new modulated structure consisting of periodic （1120） stacking faults （SFs） in the α-Fe2O3 nanowires （NWs） formed by the thermal oxidation of Fe foils is reported, using a combination of high-resolution transmission electron microscopy （HRTEM） observations and HRTEM image simulations. The periodicity of the modulated structure is 1.53 nm, which is ten times （3500） interplanar spacing and can be described by a shift of every ten （3500） planes with 1/2 the interplanar spacing of the （1120） plane. An atomic model for the Fe203 structure is proposed to simulate the modulated structure. HRTEM simulation results confirm that the modulated structure in α-Fe2O3 NWs is caused by SFs.展开更多
Very high-energy electrons(VHEEs)are potential candidates for FLASH radiotherapy for deep-seated tumors.We proposed a compact VHEE facility based on an X-band high-gradient high-power technique.In this study,we invest...Very high-energy electrons(VHEEs)are potential candidates for FLASH radiotherapy for deep-seated tumors.We proposed a compact VHEE facility based on an X-band high-gradient high-power technique.In this study,we investigated and realized the first X-band backward traveling-wave(BTW)accelerating structure as the buncher for a VHEE facility.A method for calculating the parameters of single cell from the field distribution was introduced to simplify the design of the BTW structure.Time-domain circuit equations were applied to calculate the transient beam parameters of the buncher in the unsteady state.A prototype of the BTW structure with a thermionic cathode-diode electron gun was designed,fabricated,and tested at high power at the Tsinghua X-band high-power test stand.The structure successfully operated with 5-MW microwave pulses from the pulse compressor and outputted electron bunches with an energy of 8 MeV and a pulsed current of 108 mA.展开更多
Previous models of the free electron using classical physics equations have predicted attributes that are inconsistent with the experimentally observed attributes. For example, the magnetic moment has been calculated ...Previous models of the free electron using classical physics equations have predicted attributes that are inconsistent with the experimentally observed attributes. For example, the magnetic moment has been calculated for the observed spinning electric charge. For the calculated moment to equal the observed moment, the electron would either have to spin at two hundred times the speed of light or have a charge radius two hundred times greater than the classical radius. A similar inconsistency results when the mass derived from the spin angular momentum is compared with the observed mass. A classical model is herein proposed which eliminates the magnetic moment inconsistency and also predicts the radius of the electron. The novel feature of the model is the replacement of a single charge with two opposite charges, one on the outer surface of the electron and the other at the center.展开更多
A model for the internal structure of the electron using classical physics equations has been previously published by the author. The model employs both positive and negative charges and positive and negative masses. ...A model for the internal structure of the electron using classical physics equations has been previously published by the author. The model employs both positive and negative charges and positive and negative masses. The internal attributes of the electron structure were calculated for both ring and spherical shapes. Further examination of the model reveals an instability for the ring shape. The spherical shape appears to be stable, but relies on tensile or compressive forces of the electron material for stability. The model is modified in this document to eliminate the dependency on material forces. Uniform stability is provided solely by balancing electrical and centrifugal forces. This stability is achieved by slightly elongating the sphere along the spin axis to create a prolate ellipsoid. The semi-major axis of the ellipsoid is the spin axis of the electron, and is calculated to be 1.20% longer than the semi-minor axis, which is the radius of the equator. Although the shape deviates slightly from a perfect sphere, the electric dipole moment is zero. In the author’s previously published document, the attributes of the internal components of the electron, such as charge and mass, were calculated and expressed as ratios to the classically measured values for the composite electron. It is interesting to note that all of these ratios are nearly the same as the inverse of the Fine Structure Constant, with differences of less than 15%. The electron model assumed that the outer surface charge was fixed and uniform. By allowing the charge to be mobile and the shape to have a particular ellipticity, it is shown that the calculated charge and mass ratios for the model can be exactly equal to the Fine Structure Constant and the Constant plus one. The electron radius predicted by the model is 15% greater than the Classical Electron Radius.展开更多
Sodium 3,5-bis(hydroxyimino)-1-methyl-2,4,6-trioxocyclohexanide C7H5N2NaO5 (I) has been isolated as the only product of the reaction of nitrosation of methylphloroglucinol. The structure of the titled compound has bee...Sodium 3,5-bis(hydroxyimino)-1-methyl-2,4,6-trioxocyclohexanide C7H5N2NaO5 (I) has been isolated as the only product of the reaction of nitrosation of methylphloroglucinol. The structure of the titled compound has been determined from single crystal X-ray diffraction data. The hydrated C7H5N2NaO52.5H2O crystallizes in the monoclinic space group C2/c, with a(?) 16.408(3);b(?) 12.446(3);c(?) 13.716(3);(o) 126.34(3). The planar organic anion exists in a triketo-dihydroxyimino form with the C–O and C–N distances from 1.220(2) to 1.271(2)?? and from 1.292(2) to 1.293?? respectively. In the IR spectrum of I, the sharp absorption band occurred at 1681 cm-1 due to C=O stretching indicating the strong H-interactions. The correlations of theoretical (DFT-B3LYP/aug-cc-pVDZ) and experimental UV-vis absorption spectra in neutral and alkaline ethanolic solutions showed the existence of hydroxyimino-nitroso tautomerism while ionization of I.展开更多
The local electronic structure and magnetic properties of GaAs doped with 3d transition metal (Sc, Ti, V, Cr, Mn, Fe, Co, Ni) were studied by using discrete variational method (DVM) based on density functional theory....The local electronic structure and magnetic properties of GaAs doped with 3d transition metal (Sc, Ti, V, Cr, Mn, Fe, Co, Ni) were studied by using discrete variational method (DVM) based on density functional theory. The calculated result indicated that the magnetic moment of transition metal increases first and then decreases, and reaches the maximum value when Mn is doped into GaAs. In the case of Mn concentration of 1.4%, the magnetic moment of Mn is in good agreement with the experimental result. The coupling between impure atoms in the system with two impure atoms was found to have obvious variation. For different transition metal, the coupling between the impure atom and the nearest neighbor As also has different variation.展开更多
The electronic structures and optical properties of graphyne consisting of sp-and sp 2-hybridized carbon atoms are studied using first-principles calculations.A tight-binding model of the 2p z orbitals are proposed to...The electronic structures and optical properties of graphyne consisting of sp-and sp 2-hybridized carbon atoms are studied using first-principles calculations.A tight-binding model of the 2p z orbitals are proposed to describe the electronic bands near the Fermi level.The results show that the natural band gap of graphyne originates from the inhomogeneous bindings between differently-hybridized carbon atoms.The interlayer interactions of bulk graphyne narrow the band gap to 0.16 eV and result in redshift of the optical spectral peaks as compared to single-layered graphyne.展开更多
Despite their rich information content,electronic structure data amassed at high volumes in ab initio molecular dynamics simulations are generally under-utilized.We introduce a transferable high-fidelity neural networ...Despite their rich information content,electronic structure data amassed at high volumes in ab initio molecular dynamics simulations are generally under-utilized.We introduce a transferable high-fidelity neural network representation of such data in the form of tight-binding Hamiltonians for crystalline materials.This predictive representation of ab initio electronic structure,combined with machinelearning boosted molecular dynamics,enables efficient and accurate electronic evolution and sampling.When it is applied to a one-dimension charge-density wave material,carbyne,we are able to compute the spectral function and optical conductivity in the canonical ensemble.The spectral functions evaluated during soliton-antisoliton pair annihilation process reveal significant renormalization of low-energy edge modes due to retarded electron-lattice coupling beyond the Born-Oppenheimer limit.The availability of an efficient and reusable surrogate model for the electronic structure dynamical system will enable calculating many interesting physical properties,paving the way to previously inaccessible or challenging avenues in materials modeling.展开更多
The(continuous) finite element approximations of different orders for the computation of the solution to electronic structures were proposed in some papers and the performance of these approaches is becoming appreciab...The(continuous) finite element approximations of different orders for the computation of the solution to electronic structures were proposed in some papers and the performance of these approaches is becoming appreciable and is now well understood.In this publication,the author proposes to extend this discretization for full-potential electronic structure calculations by combining the refinement of the finite element mesh,where the solution is most singular with the increase of the degree of the polynomial approximations in the regions where the solution is mostly regular.This combination of increase of approximation properties,done in an a priori or a posteriori manner,is well-known to generally produce an optimal exponential type convergence rate with respect to the number of degrees of freedom even when the solution is singular.The analysis performed here sustains this property in the case of Hartree-Fock and Kohn-Sham problems.展开更多
The local electronic structure and mag- netic properties of diluted magnetic semiconductor (Ga,Cr)N have been studied by using discrete varia- tional method (DVM) based on density functional theory. The magnetic momen...The local electronic structure and mag- netic properties of diluted magnetic semiconductor (Ga,Cr)N have been studied by using discrete varia- tional method (DVM) based on density functional theory. The magnetic moments per Cr atom vary significantly with Cr concentration, and the trend of variation is in agreement with that of the experiment. The coupling between Cr atoms in the system with two Cr atoms considered is found to be ferromagnetic, and the magnetic moment per Cr atom is similar to the case in which only one Cr atom is considered in the same doping concentration. For all doping con- centrations, the coupling between Cr and the nearest neighbor N is found to be antiferromagnetic, and the Cr 3d states hybridize strongly with N 2p states, which are in agreement with the band calculations.展开更多
文摘By use of self-consistent field Xα scattered-wave (SCF-Xα-SW) method, the electronic structure was calculated for four models of Ti4Al14X (X=Al, Fe, Ni and Cu) clusters. The Ti4Al14X cluster was developed based on L12 Al3Ti-base intermetallic compound. The results are presented using the density of states (DOS) and one-electron properties, such as relative binding tendency between the atom and the model cluster, and hybrid bonding tendency between the alloying element and the host atoms. By comparing the four models of Ti4Al14X cluster, the effect of the Fe, Ni or Cu atom on the physical properties of Al3Ti-based L12 intermetallic compounds is analyzed. The results indicate that the addition of the Fe, Ni or Cu atom intensifies the relative binding tendency between Ti atom and Ti4Al14X cluster. It was found that the Fermi level (EF) lies in a maximum in the DOS for Ti4Al14Al cluster; on the contrary, the EF comes near a minimum tn the DOS for Ti4Al14X (X=Fe, Ni and Cu) cluster. Thus the L12 crystal structure for binary Al3Ti alloy is unstable, and the addition of the Fe, Ni or Cu atom to Al3Ti is benefical to stabilize L12 crystal structure. The calculation also shows that the Fe, Ni or Cu atom strengthens the hybrid bonding tendency between the central atom and the host atoms for Ti4Al14X cluster and thereby may lead to the constriction of the lattice of Al3Ti-base intermetallic compounds.
基金financially supported by the Science Foundation for International Cooperation of Sichuan Province (2014HH0016)the Fundamental Research Funds for the Central Universities (SWJTU2014: A0920502051113-10000)National Magnetic Confinement Fusion Science Program (2011GB112001)
文摘In this work, we choose Nb3Al/Nb3Sn as a new test case for flat/steep band model of superconductivity. Based on the density functional theory in the generalized gradient approximation, the electronic structure of Nb3Al/ Nb3Sn has been studied. The obtained results agree well with those of the earlier studies and show clearly fiat bands around the Fermi level. The steep bands as characterized in this work locate around the M point in the first Brillouin zone. The obtained results reveal that Nb3Al/Nb3Sn fits more to the ＂Flat/steep＂ band model than to the van-Hove singularity scenario. The fiat/steep band condition for superconductivity implies a different thermodynamic behavior of superconductors other than that predicted from the conventional BCS theory. This observation sets up an indicator for selecting a suitable superconductor when its large-scale industrial use is needed, for example, in superconducting maglev system or ITER project.
文摘Using our recently published electron’s charge electromagnetic flux manifold fiber model of the electron, described by analytical method and numerical simulations, we show how the fine structure constant is embedded as a geometrical proportionality constant in three dimensional space of its charge manifold and how this dictates the first QED term one-loop contribution of its anomalous magnetic moment making for the first time a connection of its intrinsic characteristics with physical geometrical dimensions and therefore demonstrating that the physical electron charge cannot be dimensionless. We show that the fine structure constant (FSC) α, and anomalous magnetic moment α<sub>μ</sub> of the electron is related to the sphericity of its charge distribution which is not perfectly spherical and thus has a shape, and therefore its self-confined charge possesses measurable physical dimensions. We also explain why these are not yet able to be measured by past and current experiments and how possible we could succeed.
基金financially supported by National Natural Science Foundations of China(Nos.51301149 and 50371059)
文摘In the present study, two models of atom occupation in LaNi4Co were put forward and corresponding valence electron structures （VESs） of these two models were investigated according to empirical electron theory （EET） of solids and molecules. Results demonstrate that the VES-concerned hardness factor （FH） of LaNi4Co is lower than that of LaNi5, so LaNi4Co has lower hardness, higher plasticity and improved anti-pulverization ability. In the mean time, the difference of the equilibrium hydrogen pressure between LaNiaCo and LaNi5 was analyzed in the electronic level. The analysis shows that the strength of the weakest bond net in octahedron lattice interstices of LaNi4Co is much lower than that in LaNis; consequently, LaNi4Co＇s bond net easily deforms to accommodate hydrogen so that LaNi4Co has lower equilibrium hydrogen pressure in comparison with LaNis. The results can provide some theory guide on the design of hydrogen storage alloys.
文摘We evaluate three of the quantum constants of hydrogen, the electron, e<sup>-</sup>, the Bohr radius, a<sub>0</sub>, and the Rydberg constants, , as natural unit frequency equivalents, v. This is equivalent to Planck’s constant, h, the speed of light, c, and the electron charge, e, all scaled to 1 similar in concept to the Hartree atomic, and Planck units. These frequency ratios are analyzed as fundamental coupling constants. We recognize that the ratio of the product of 8π<sup>2</sup>, the v<sub>e</sub><sub>-</sub> times the v<sub>R</sub> divided by v<sub>a</sub><sub>0</sub> squared equals 1. This is a power law defining Planck’s constant in a dimensionless domain as 1. We also find that all of the possible dimensionless and dimensioned ratios correspond to other constants or classic relationships, and are systematically inter-related by multiple power laws to the fine structure constant, α;and the geometric factors 2, and π. One is related to an angular momentum scaled by Planck’s constant, and another is the kinetic energy law. There are harmonic sinusoidal relationships based on 2π circle geometry. In the dimensionless domain, α is equivalent to the free space constant of permeability, and its reciprocal to permittivity. If any two quanta are known, all of the others can be derived within power laws. This demonstrates that 8π2 represents the logical geometric conversion factor that links the Euclid geometric factors/three dimensional space, and the quantum domain. We conclude that the relative scale and organization of many of the fundamental constants even beyond hydrogen are related to a unified power law system defined by only three physical quanta of v<sub>e</sub><sub>-</sub>, v<sub>R</sub>, and v<sub>a</sub><sub>0</sub>.
基金Authors deeply appreciate the support from the National Natural Science Foundation of China(No.50275098)the Natural Science Foundation of Liaoning Province(No.20022031)
文摘A model of liquid ZA27 cast alloy is established according to molecular dynamics theory and an atomic structural model of co-existent a phase and liquid is also presented by means of computer programming. Recursion method is adopted to calculate the electronic structure of RE (rare earth) in grains and around phase boundaries respectively. The calculation shows that RE is more stable around phase boundaries than in grains, which explains the fact that the solution of RE in a phase is less, and RE mainly aggregates in front of phase boundary. The calculations of bonding order integrals also show that RE in front of phases hardly solidify onto the grain surfaces as active element so as to prevent grains growth and refine the grains. As a result, the modification mechanism of RE may be explained from the view of electronic structure.
基金support from the National Natural Science Foundation of China(NSFC nos.52172257,22005334,21773301 and 52022106)the Natural Science Foundation of Beijing(grant no.Z200013).
文摘Intercalation provides to the host materials a means for controlled variation of many physical/chemical properties and dominates the reactions in metal‐ion batteries.Of particular interest is the graphite intercalation compounds with intriguing staging structures,which however are still unclear,especially in their nanostructure and dynamic transition mechanism.Herein,the nature of the staging structure and evolution of the lithium(Li)‐intercalated graphite was revealed by cryogenic‐transmission electron microscopy and other methods at the nanoscale.The intercalated Li‐ions distribute unevenly,generating local stress and dislocations in the graphitic structure.Each staging compound is found macroscopically ordered but microscopically inhomogeneous,exhibiting a localized‐domains structural model.Our findings uncover the correlation between the long‐range ordered structure and short‐range domains,refresh the insights on the staging structure and transition of Li‐intercalated/deintercalated graphite,and provide effective ways to enhance the reaction kinetic in rechargeable batteries by defect engineering.
基金the start-up fund provided by the Engineering Science and Mechanics Department, College of Engineering, and Materials Research Institute at the Pennsylvania State University (215-37 1001 cc:H.Cheng)
文摘Transient electronics are an emerging class of electronics with the unique characteristic to completely dissolve within a programmed period of time. Since no harmful byproducts are released, these electronics can be used in the human body as a diagnostic tool, for instance, or they can be used as environmentally friendly alternatives to existing electronics which disintegrate when exposed to water. Thus, the most crucial aspect of transient electronics is their ability to disintegrate in a practical manner and a review of the literature on this topic is essential for understanding the current capabilities of transient electronics and areas of future research. In the past, only partial dissolution of transient electronics was possible, however, total dissolution has been achieved with a recent discovery that silicon nanomembrane undergoes hydrolysis. The use of single- and multi-layered structures has also been explored as a way to extend the lifetime of the electronics. Analytical models have been developed to study the dissolution of various functional materials as well as the devices constructed from this set of functional materials and these models prove to be useful in the design of the transient electronics.
基金Project supported by the National Key Basic Research Development Program of China (Grant No.2012CB722705)the Natural Science Foundation for Outstanding Young Scientists in Shandong Province,China (Grant No.JQ201002)+2 种基金the Program for Foreign Cultural and Educational Experts (Grant No.20123702083)the Program for Higher Education Science and Technology in Shandong Province (Grant No.J12LA17)Wang Yi-Qian would like to thank the financial support from Taishan Outstanding Overseas Scholar Program of Shandong Province,China
文摘A new modulated structure consisting of periodic （1120） stacking faults （SFs） in the α-Fe2O3 nanowires （NWs） formed by the thermal oxidation of Fe foils is reported, using a combination of high-resolution transmission electron microscopy （HRTEM） observations and HRTEM image simulations. The periodicity of the modulated structure is 1.53 nm, which is ten times （3500） interplanar spacing and can be described by a shift of every ten （3500） planes with 1/2 the interplanar spacing of the （1120） plane. An atomic model for the Fe203 structure is proposed to simulate the modulated structure. HRTEM simulation results confirm that the modulated structure in α-Fe2O3 NWs is caused by SFs.
基金supported by the National Natural Science Foundation of China(No.11922504).
文摘Very high-energy electrons(VHEEs)are potential candidates for FLASH radiotherapy for deep-seated tumors.We proposed a compact VHEE facility based on an X-band high-gradient high-power technique.In this study,we investigated and realized the first X-band backward traveling-wave(BTW)accelerating structure as the buncher for a VHEE facility.A method for calculating the parameters of single cell from the field distribution was introduced to simplify the design of the BTW structure.Time-domain circuit equations were applied to calculate the transient beam parameters of the buncher in the unsteady state.A prototype of the BTW structure with a thermionic cathode-diode electron gun was designed,fabricated,and tested at high power at the Tsinghua X-band high-power test stand.The structure successfully operated with 5-MW microwave pulses from the pulse compressor and outputted electron bunches with an energy of 8 MeV and a pulsed current of 108 mA.
文摘Previous models of the free electron using classical physics equations have predicted attributes that are inconsistent with the experimentally observed attributes. For example, the magnetic moment has been calculated for the observed spinning electric charge. For the calculated moment to equal the observed moment, the electron would either have to spin at two hundred times the speed of light or have a charge radius two hundred times greater than the classical radius. A similar inconsistency results when the mass derived from the spin angular momentum is compared with the observed mass. A classical model is herein proposed which eliminates the magnetic moment inconsistency and also predicts the radius of the electron. The novel feature of the model is the replacement of a single charge with two opposite charges, one on the outer surface of the electron and the other at the center.
文摘A model for the internal structure of the electron using classical physics equations has been previously published by the author. The model employs both positive and negative charges and positive and negative masses. The internal attributes of the electron structure were calculated for both ring and spherical shapes. Further examination of the model reveals an instability for the ring shape. The spherical shape appears to be stable, but relies on tensile or compressive forces of the electron material for stability. The model is modified in this document to eliminate the dependency on material forces. Uniform stability is provided solely by balancing electrical and centrifugal forces. This stability is achieved by slightly elongating the sphere along the spin axis to create a prolate ellipsoid. The semi-major axis of the ellipsoid is the spin axis of the electron, and is calculated to be 1.20% longer than the semi-minor axis, which is the radius of the equator. Although the shape deviates slightly from a perfect sphere, the electric dipole moment is zero. In the author’s previously published document, the attributes of the internal components of the electron, such as charge and mass, were calculated and expressed as ratios to the classically measured values for the composite electron. It is interesting to note that all of these ratios are nearly the same as the inverse of the Fine Structure Constant, with differences of less than 15%. The electron model assumed that the outer surface charge was fixed and uniform. By allowing the charge to be mobile and the shape to have a particular ellipticity, it is shown that the calculated charge and mass ratios for the model can be exactly equal to the Fine Structure Constant and the Constant plus one. The electron radius predicted by the model is 15% greater than the Classical Electron Radius.
文摘Sodium 3,5-bis(hydroxyimino)-1-methyl-2,4,6-trioxocyclohexanide C7H5N2NaO5 (I) has been isolated as the only product of the reaction of nitrosation of methylphloroglucinol. The structure of the titled compound has been determined from single crystal X-ray diffraction data. The hydrated C7H5N2NaO52.5H2O crystallizes in the monoclinic space group C2/c, with a(?) 16.408(3);b(?) 12.446(3);c(?) 13.716(3);(o) 126.34(3). The planar organic anion exists in a triketo-dihydroxyimino form with the C–O and C–N distances from 1.220(2) to 1.271(2)?? and from 1.292(2) to 1.293?? respectively. In the IR spectrum of I, the sharp absorption band occurred at 1681 cm-1 due to C=O stretching indicating the strong H-interactions. The correlations of theoretical (DFT-B3LYP/aug-cc-pVDZ) and experimental UV-vis absorption spectra in neutral and alkaline ethanolic solutions showed the existence of hydroxyimino-nitroso tautomerism while ionization of I.
基金the National Natural Science Foundation of China(Grant No.10347010)
文摘The local electronic structure and magnetic properties of GaAs doped with 3d transition metal (Sc, Ti, V, Cr, Mn, Fe, Co, Ni) were studied by using discrete variational method (DVM) based on density functional theory. The calculated result indicated that the magnetic moment of transition metal increases first and then decreases, and reaches the maximum value when Mn is doped into GaAs. In the case of Mn concentration of 1.4%, the magnetic moment of Mn is in good agreement with the experimental result. The coupling between impure atoms in the system with two impure atoms was found to have obvious variation. For different transition metal, the coupling between the impure atom and the nearest neighbor As also has different variation.
基金supported by the National Basic Research Program of China(2012CB932302)the National Natural Science Foundation of China(10974119)the Natural Science Fund for Distinguished Young Scholars of Shandong Province(JQ201001)
文摘The electronic structures and optical properties of graphyne consisting of sp-and sp 2-hybridized carbon atoms are studied using first-principles calculations.A tight-binding model of the 2p z orbitals are proposed to describe the electronic bands near the Fermi level.The results show that the natural band gap of graphyne originates from the inhomogeneous bindings between differently-hybridized carbon atoms.The interlayer interactions of bulk graphyne narrow the band gap to 0.16 eV and result in redshift of the optical spectral peaks as compared to single-layered graphyne.
基金supported by the National Natural Science Foundation of China(11725415 and 11934001)the Ministry of Science and Technology of China(2018YFA0305601 and2016YFA0301004)+1 种基金by the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB28000000)supported in part by the Center for Chemistry in Solution and at Interfaces(CSI)at Princeton University,funded by the DOE Award DE-SC0019394。
文摘Despite their rich information content,electronic structure data amassed at high volumes in ab initio molecular dynamics simulations are generally under-utilized.We introduce a transferable high-fidelity neural network representation of such data in the form of tight-binding Hamiltonians for crystalline materials.This predictive representation of ab initio electronic structure,combined with machinelearning boosted molecular dynamics,enables efficient and accurate electronic evolution and sampling.When it is applied to a one-dimension charge-density wave material,carbyne,we are able to compute the spectral function and optical conductivity in the canonical ensemble.The spectral functions evaluated during soliton-antisoliton pair annihilation process reveal significant renormalization of low-energy edge modes due to retarded electron-lattice coupling beyond the Born-Oppenheimer limit.The availability of an efficient and reusable surrogate model for the electronic structure dynamical system will enable calculating many interesting physical properties,paving the way to previously inaccessible or challenging avenues in materials modeling.
文摘The(continuous) finite element approximations of different orders for the computation of the solution to electronic structures were proposed in some papers and the performance of these approaches is becoming appreciable and is now well understood.In this publication,the author proposes to extend this discretization for full-potential electronic structure calculations by combining the refinement of the finite element mesh,where the solution is most singular with the increase of the degree of the polynomial approximations in the regions where the solution is mostly regular.This combination of increase of approximation properties,done in an a priori or a posteriori manner,is well-known to generally produce an optimal exponential type convergence rate with respect to the number of degrees of freedom even when the solution is singular.The analysis performed here sustains this property in the case of Hartree-Fock and Kohn-Sham problems.
基金supported by the National Natural Science Foundation of China(Grant No.10347010)the Anhui Institute of Solid State Physics of CAS.
文摘The local electronic structure and mag- netic properties of diluted magnetic semiconductor (Ga,Cr)N have been studied by using discrete varia- tional method (DVM) based on density functional theory. The magnetic moments per Cr atom vary significantly with Cr concentration, and the trend of variation is in agreement with that of the experiment. The coupling between Cr atoms in the system with two Cr atoms considered is found to be ferromagnetic, and the magnetic moment per Cr atom is similar to the case in which only one Cr atom is considered in the same doping concentration. For all doping con- centrations, the coupling between Cr and the nearest neighbor N is found to be antiferromagnetic, and the Cr 3d states hybridize strongly with N 2p states, which are in agreement with the band calculations.
