Direct-write atom lithography,one of the potential nanofabrication techniques,is restricted by some difficulties in producing optical masks for the deposition of complex structures.In order to make further progress,a ...Direct-write atom lithography,one of the potential nanofabrication techniques,is restricted by some difficulties in producing optical masks for the deposition of complex structures.In order to make further progress,a structured mirror array is developed to transversely collimate the chromium atomic beam in two dimensions.The best collimation is obtained when the laser red detunes by natural line-width of transition 7S3 → 7P40 of the chromium atom.The collimation ratio is 0.45 vertically（in x axis）,and it is 0.55 horizontally（in y axis）.The theoretical model is also simulated,and success of our structured mirror array is achieved.展开更多
Synthetic two-dimensional（2 D） polymers have totally different topology structures compared with traditional linear or branched polymers. The peculiar 2 D structures bring superior properties. Although, from linear ...Synthetic two-dimensional（2 D） polymers have totally different topology structures compared with traditional linear or branched polymers. The peculiar 2 D structures bring superior properties. Although, from linear to 2 D polymers, the study of these new materials is still in its infancy, they already show potential applications especially in optoelectronics, membranes, energy storage and catalysis, etc. In this review, we summarize the recent progress of the 2 D materials from three respects：（1） Chemistry—different types of polymerization reactions or supramolecular assembly to construct the 2 D networks were described;（2） Preparation methods—surface science, crystal engineering approaches and solution synthesis were introduced;（3） Functionalization and some early applications.展开更多
Light–matter interactions in two-dimensional(2D)materials have been the focus of research since the discovery of graphene.The light–matter interaction length in 2D materials is,however,much shorter than that in bulk...Light–matter interactions in two-dimensional(2D)materials have been the focus of research since the discovery of graphene.The light–matter interaction length in 2D materials is,however,much shorter than that in bulk materials owing to the atomic nature of 2D materials.Plasmonic nanostructures are usually integrated with 2D materials to enhance the light–matter interactions,offering great opportunities for both fundamental research and technological applications.Nanoparticle-on-mirror(NPo M)structures with extremely confined optical fields are highly desired in this aspect.In addition,2D materials provide a good platform for the study of plasmonic fields with subnanometer resolution and quantum plasmonics down to the characteristic length scale of a single atom.A focused and up-to-date review article is highly desired for a timely summary of the progress in this rapidly growing field and to encourage more research efforts in this direction.In this review,we will first introduce the basic concepts of plasmonic modes in NPo M structures.Interactions between plasmons and quasi-particles in 2D materials,e.g.,excitons and phonons,from weak to strong coupling and potential applications will then be described in detail.Related phenomena in subnanometer metallic gaps separated by 2D materials,such as quantum tunneling,will also be touched.We will finally discuss phenomena and physical processes that have not been understood clearly and provide an outlook for future research.We believe that the hybrid systems of2D materials and NPo M structures will be a promising research field in the future.展开更多
Two-dimensional function photonic crystals, in which the dielectric constants of medium columns are the functions of space coordinates , are proposed and studied numerically. The band gaps structures of the photonic c...Two-dimensional function photonic crystals, in which the dielectric constants of medium columns are the functions of space coordinates , are proposed and studied numerically. The band gaps structures of the photonic crystals for TE and TM waves are different from the two-dimensional conventional photonic crystals. Some absolute band gaps and semiDirac points are found. When the medium column radius and the function form of the dielectric constant are modulated, the numbers, width, and position of band gaps are changed, and the semi-Dirac point can either occur or disappear. Therefore,the special band gaps structures and semi-Dirac points can be achieved through the modulation on the two-dimensional function photonic crystals. The results will provide a new design method of optical devices based on the two-dimensional function photonic crystals.展开更多
The algebraic solitary wave and its associated eigenvalue problem in a deep stratified fluid with a free surface and a shallow upper layer were studied. And its vertical structure was examined. An exact solution for t...The algebraic solitary wave and its associated eigenvalue problem in a deep stratified fluid with a free surface and a shallow upper layer were studied. And its vertical structure was examined. An exact solution for the derived 2D Benjamin-Ono equation was obtained, and physical explanation was given with the corresponding dispersion relation. As a special case, the vertical structure of the weakly nonlinear internal wave for the Holmboe density distribution was numerically investigated, and the propagating mechanism of the internal wave was studied by using the ray theory.展开更多
This paper presents the theoretical investigation of hierarchical sub-wavelength photonic structures with various periods and numbers of layers, which were fabricated using a high-order waveguide-mode interference fie...This paper presents the theoretical investigation of hierarchical sub-wavelength photonic structures with various periods and numbers of layers, which were fabricated using a high-order waveguide-mode interference field. A 442-nm laser was used to excite high-order waveguide modes in an asymmetric metal-cladding dielectric waveguide structure. The dispersion curve of the waveguide modes was theoretically analyzed, and the distribution of the interference field of high-order waveguide modes was numerically simulated using the finite-element method. The various dependences of the characteristics of hierarchical sub-wavelength photonic structures on the thickness and refractive index of the photoresist and the waveguide mode were investigated in detail. These hierarchical sub-wavelength photonic structures have various periods and numbers of layers and can be fabricated by a simple and low-cost method.展开更多
With the development of the aerospace industry,space missions are becoming more complicated and diversified,and there is a demand for antenna mechanisms with a larger physical aperture.In this paper,a planar deployabl...With the development of the aerospace industry,space missions are becoming more complicated and diversified,and there is a demand for antenna mechanisms with a larger physical aperture.In this paper,a planar deployable mechanism is proposed,which can form a flat reflection surface with a small gap between plates.To this end,a novel large-scale two-dimensional deployable nine-grid planar antenna mechanism is designed.First,two antenna folding schemes and four supporting mechanism schemes are proposed.Through comparison analysis,the antenna configuration scheme with the best comprehensive performance is selected.A kinematic model of the deployable mechanism is established,and its kinematic characteristics are analyzed.Then,the correctness of the kinematic model is verified by comparing the analytical and simulation results of the kinematic model.Subsequently,a finite element model of the antenna is developed.Based on the response surface method,the structural parameters of the support rods of the antenna are optimized,and a set of optimized solutions with lightweight and high fundamental frequency characteristics are obtained.Finally,a prototype of the proposed nine-grid planar antenna is fabricated.The feasibility of the deployment principle and the rationality of the designed mechanism are verified by deployment experiments.展开更多
In recent years, structure design and predictions based on global optimization approach as implemented in CALYPSO software have gained great success in accelerating the discovery of novel two-dimensional(2D) materials...In recent years, structure design and predictions based on global optimization approach as implemented in CALYPSO software have gained great success in accelerating the discovery of novel two-dimensional(2D) materials. Here we highlight some most recent research progress on the prediction of novel 2D structures, involving elements, metal-free and metal-containing compounds using CALYPSO package. Particular emphasis will be given to those 2D materials that exhibit unique electronic and magnetic properties with great potentials for applications in novel electronics, optoelectronics,magnetronics, spintronics, and photovoltaics. Finally, we also comment on the challenges and perspectives for future discovery of multi-functional 2D materials.展开更多
Aviation fuel pumps of the future are required to be highly efficient and lightweight.As such,this work presents the designs of various mechanisms and structures of advanced twodimensional piston pumps for aero-engine...Aviation fuel pumps of the future are required to be highly efficient and lightweight.As such,this work presents the designs of various mechanisms and structures of advanced twodimensional piston pumps for aero-engines,and their universal kinematic design methods are detailed herein.The efficiency of various piston pump prototypes was experimentally tested at various speeds in an open circuit.The experimental results indicate that two-dimensional piston pumps have a volumetric efficiency>91%and a higher power–mass ratio than conventional fuel pumps under all the conditions studied.Furthermore,the structural and material problems encountered during testing can provide a blueprint for further improvement of the design and processing of two-dimensional piston fuel pumps.展开更多
We use the strong field approximation with a time window function controlling the release time of electrons to study the intra-cycle and inter-cycle interferences in few-cycle intense laser pulses impinging on He. The...We use the strong field approximation with a time window function controlling the release time of electrons to study the intra-cycle and inter-cycle interferences in few-cycle intense laser pulses impinging on He. The diffraction fringes, i.e., the vertical stripe-like structure, observed in the experimental two-dimensional photoelectron momentum distributions of Gopal et al. （2009 Phys. Rev. Lett. 103 053001） have been attributed to the interplay of the intra- and inter-cycle interferences. The pure numerical calculations by solving the time-dependent Schrrdinger equation are also performed and the results are compared with the experimental measurements directly. It has been found that the position of the stripe-like structure can be used to determine the duration of the laser pulses used in experiments.展开更多
The electronic structure,magnetic,and optical properties of two-dimensional(2D)GaSe doped with rare earth elements X(X=Sc,Y,La,Ce,Eu)were calculated using the first-principles plane wave method based on den-sity funct...The electronic structure,magnetic,and optical properties of two-dimensional(2D)GaSe doped with rare earth elements X(X=Sc,Y,La,Ce,Eu)were calculated using the first-principles plane wave method based on den-sity functional theory.The results show that intrinsic 2D GaSe is a p-type nonmagnetic semiconductor with an indi-rect bandgap of 2.6611 eV.The spin-up and spin-down channels of Sc-,Y-,and La-doped 2D GaSe are symmetric,they are non-magnetic semiconductors.The magnetic moments of Ce-and Eu-doped 2D GaSe are 0.908μ_(B)and 7.163μ_(B),which are magnetic semiconductors.Impurity energy levels appear in both spin-up and spin-down chan-nels of Eu-doped 2D GaSe,which enhances the probability of electron transition.Compared with intrinsic 2D GaSe,the static dielectric constant of the doped 2D GaSe increases,and the polarization ability is strengthened.The ab-sorption spectrum of the doped 2D GaSe shifts in the low-energy direction,and the red-shift phenomenon occurs,which extends the absorption spectral range.The optical reflection coefficient of the doped 2D GaSe is improved in the low energy region,and the improvement of Eu-doped 2D GaSe is the most obvious.展开更多
An inorganic-organic hybrid thioantimonate（Ⅲ） [CH3（CH2）3NH3]2Sb4S7 1 with layered structure was synthesized by solvothermal method. 1 crystallizes in the triclinic system, space group P1 with a = 7.0124（11）, b ...An inorganic-organic hybrid thioantimonate（Ⅲ） [CH3（CH2）3NH3]2Sb4S7 1 with layered structure was synthesized by solvothermal method. 1 crystallizes in the triclinic system, space group P1 with a = 7.0124（11）, b = 11.919（2）, c =14.879（3）A, α = 108.791（3）, β= 102.441（3）, γ = 92.846（2）°, V= 1140.1（3）A3, Mr = 859.71, Z= 2, Do = 2.504 g/cm^3 ,μ = 5.324 mm^-1, F（000） = 804, S = 1.013, the Final R = 0.0297 and wR = 0.0618 for 3534 observed reflections with Ⅰ 〉 2 σ（Ⅰ）. 1 consists of [C4HgNH3]＋ cations and two-dimensional [Sb4ST]n^2n- anion which is composed of three SbS3 trigonal pyranaids and one SbS4 unit joined by sharing common comers. The anionic layers are stacked perpendicularly to the c axis of the unit cell forming two-dimensional channels between the layers. The [C4H9NH3]^＋ cations interdigitate in a bilayer and reside in the 2D channels leading to a sandwich-like arrangement of the anion and cations.展开更多
By using the generalized characteristic analysis method, the two-dimensional four-wave Riemann problem for scalar conservation laws, which is nonconvex along the y direction, was studied. Riemann solutions, which invo...By using the generalized characteristic analysis method, the two-dimensional four-wave Riemann problem for scalar conservation laws, which is nonconvex along the y direction, was studied. Riemann solutions, which involve the Guckenheimer structure, were constructed.展开更多
Open-framework materials are of great interest from both the theoretical and practical points of view due to their catalytic, absorbent, and ion-exchange properties. In the past decade, the study of structurally and c...Open-framework materials are of great interest from both the theoretical and practical points of view due to their catalytic, absorbent, and ion-exchange properties. In the past decade, the study of structurally and chemically diverse open framework solids has been flourishing. A large variety of silicates, phosphates and carboxylates with open-framework structures have been synthesized with organic amines as templates. It has also been demonstrated that other oxysalts such as selenate, arsenate and germanate are used to build up open architectures. As far as the sulfate is concerned,展开更多
A two-dimensional photonic crystal with a one-dimensional periodic dielectric background is proposed. The photonic band modulation effects due to the periodic background are investigated based on the plane wave expans...A two-dimensional photonic crystal with a one-dimensional periodic dielectric background is proposed. The photonic band modulation effects due to the periodic background are investigated based on the plane wave expansion method. We find that periodic modulation of the dielectric background greatly alters photonic band structures, especially for the E-polarization modes. The number, width and position of the photonic band gaps （PBGs） sensitively depend on the structure parameters （the layer thicknesses and dielectric constants） of the one-dimensional periodic background,展开更多
Two-dimensional(2D) layered perovskites have emerged as potential alternates to traditional three-dimensional(3D)analogs to solve the stability issue of perovskite solar cells. In recent years, many efforts have been ...Two-dimensional(2D) layered perovskites have emerged as potential alternates to traditional three-dimensional(3D)analogs to solve the stability issue of perovskite solar cells. In recent years, many efforts have been spent on manipulating the interlayer organic spacing cation to improve the photovoltaic properties of Dion–Jacobson(DJ) perovskites. In this work, a serious of cycloalkane(CA) molecules were selected as the organic spacing cation in 2D DJ perovskites, which can widely manipulate the optoelectronic properties of the DJ perovskites. The underlying relationship between the CA interlayer molecules and the crystal structures, thermodynamic stabilities, and electronic properties of 58 DJ perovskites has been investigated by using automatic high-throughput workflow cooperated with density-functional(DFT) calculations.We found that these CA-based DJ perovskites are all thermodynamic stable. The sizes of the cycloalkane molecules can influence the degree of inorganic framework distortion and further tune the bandgaps with a wide range of 0.9–2.1 eV.These findings indicate the cycloalkane molecules are suitable as spacing cation in 2D DJ perovskites and provide a useful guidance in designing novel 2D DJ perovskites for optoelectronic applications.展开更多
Two compounds with 3-methylbenzoic acid（HL） [Co（L）2（4,4＇-bipy）]n 1 and [Zn2（L）4（4,4＇-bipy）]n 2（L = 3-methylbenzoic acid） have been hydrothermally synthesized directly and characterized by single-crystal ...Two compounds with 3-methylbenzoic acid（HL） [Co（L）2（4,4＇-bipy）]n 1 and [Zn2（L）4（4,4＇-bipy）]n 2（L = 3-methylbenzoic acid） have been hydrothermally synthesized directly and characterized by single-crystal X-ray diffraction analysis,elemental analyses,IR spectra and ultraviolet-visible diffuse reflection integral spectra（UV-Vis DRIS）.The two compounds are both one-dimensional infinite chains.The structural difference is that 1 is a double-chain structure and 2 is only a single chain one.At the same time,the carboxylate groups adopt different modes in the two compounds,relatively.Additionally,in order to explore the structural characteristic,two-dimen-sional IR spectra are investigated for 1 and 2.Photo-luminescent property of 2 is also researched in detail.展开更多
Solvothermal reaction of 3-aminoisonicotinic acid（Haina） and Cu（NO_3）_2·2.5H_2O gave a novel twodimensional（2D） microporous metal–organic framework, [Cu（aina）_2（DMF）]·DMF（1, DMF = N,N-dimethylfor...Solvothermal reaction of 3-aminoisonicotinic acid（Haina） and Cu（NO_3）_2·2.5H_2O gave a novel twodimensional（2D） microporous metal–organic framework, [Cu（aina）_2（DMF）]·DMF（1, DMF = N,N-dimethylformamide）. Single-crystal X-ray crystallographic study of compound 1 revealed that Cu（II）ions are linked by ainaàligands forming square grid-like layers, which stack together via multiple hydrogen bonding interactions. The solvent-free framework of 1a displayed considerable porosity（void = 46.5%） with one-dimensional（1D） open channels（4.7 ？ ？ 4.8 ？） functionalized by amino groups.Gas sorption measurements of 1 revealed selective carbon dioxide（CO_2） and acetylene（C_2H_2） adsorption over methane（CH_4） and nitrogen（N_2） at ambient temperature.展开更多
基金Project supported by the Shanghai Nanoscience Foundation,China (Grant Nos. 0852nm07000 and 0952nm07000)the National Natural Science Foundation of China (Grant Nos. 10804084 and 91123022)+1 种基金the National Key Technology R & D Program,China (Grant No. 2006BAF06B08)the Specialized Research Fund for the Doctoral Program of Ministry of High Education of China (Grant No. 200802471008)
文摘Direct-write atom lithography,one of the potential nanofabrication techniques,is restricted by some difficulties in producing optical masks for the deposition of complex structures.In order to make further progress,a structured mirror array is developed to transversely collimate the chromium atomic beam in two dimensions.The best collimation is obtained when the laser red detunes by natural line-width of transition 7S3 → 7P40 of the chromium atom.The collimation ratio is 0.45 vertically（in x axis）,and it is 0.55 horizontally（in y axis）.The theoretical model is also simulated,and success of our structured mirror array is achieved.
基金financially supported by the National Natural Science Foundation of China(No.21604046)the National Young Thousand Talents Program,Shandong Provincial Natural Science Foundation,China(No.ZR2016XJ004)
文摘Synthetic two-dimensional（2 D） polymers have totally different topology structures compared with traditional linear or branched polymers. The peculiar 2 D structures bring superior properties. Although, from linear to 2 D polymers, the study of these new materials is still in its infancy, they already show potential applications especially in optoelectronics, membranes, energy storage and catalysis, etc. In this review, we summarize the recent progress of the 2 D materials from three respects：（1） Chemistry—different types of polymerization reactions or supramolecular assembly to construct the 2 D networks were described;（2） Preparation methods—surface science, crystal engineering approaches and solution synthesis were introduced;（3） Functionalization and some early applications.
基金supported by the National Natural Science Foundation of China(62205183)the Research Grants Council of Hong Kong(ANR/RGC,Ref.No.A-CUHK404/21).
文摘Light–matter interactions in two-dimensional(2D)materials have been the focus of research since the discovery of graphene.The light–matter interaction length in 2D materials is,however,much shorter than that in bulk materials owing to the atomic nature of 2D materials.Plasmonic nanostructures are usually integrated with 2D materials to enhance the light–matter interactions,offering great opportunities for both fundamental research and technological applications.Nanoparticle-on-mirror(NPo M)structures with extremely confined optical fields are highly desired in this aspect.In addition,2D materials provide a good platform for the study of plasmonic fields with subnanometer resolution and quantum plasmonics down to the characteristic length scale of a single atom.A focused and up-to-date review article is highly desired for a timely summary of the progress in this rapidly growing field and to encourage more research efforts in this direction.In this review,we will first introduce the basic concepts of plasmonic modes in NPo M structures.Interactions between plasmons and quasi-particles in 2D materials,e.g.,excitons and phonons,from weak to strong coupling and potential applications will then be described in detail.Related phenomena in subnanometer metallic gaps separated by 2D materials,such as quantum tunneling,will also be touched.We will finally discuss phenomena and physical processes that have not been understood clearly and provide an outlook for future research.We believe that the hybrid systems of2D materials and NPo M structures will be a promising research field in the future.
基金Project supported by the National Natural Science Foundations of China(Grant No.61275047)the Research Project of Chinese Ministry of Education(Grant No.213009A)the Scientific and Technological Development Foundation of Jilin Province,China(Grant No.20130101031JC)
文摘Two-dimensional function photonic crystals, in which the dielectric constants of medium columns are the functions of space coordinates , are proposed and studied numerically. The band gaps structures of the photonic crystals for TE and TM waves are different from the two-dimensional conventional photonic crystals. Some absolute band gaps and semiDirac points are found. When the medium column radius and the function form of the dielectric constant are modulated, the numbers, width, and position of band gaps are changed, and the semi-Dirac point can either occur or disappear. Therefore,the special band gaps structures and semi-Dirac points can be achieved through the modulation on the two-dimensional function photonic crystals. The results will provide a new design method of optical devices based on the two-dimensional function photonic crystals.
文摘The algebraic solitary wave and its associated eigenvalue problem in a deep stratified fluid with a free surface and a shallow upper layer were studied. And its vertical structure was examined. An exact solution for the derived 2D Benjamin-Ono equation was obtained, and physical explanation was given with the corresponding dispersion relation. As a special case, the vertical structure of the weakly nonlinear internal wave for the Holmboe density distribution was numerically investigated, and the propagating mechanism of the internal wave was studied by using the ray theory.
基金Project supported by the National Natural Science Foundation of China(Grant No.61505074)the National Key Basic Research Program of China(Grant No.2013CBA01703)the Hong Liu Young Teachers Training Program Funded Projects of Lanzhou University of Technology(Grant No.Q201509)
文摘This paper presents the theoretical investigation of hierarchical sub-wavelength photonic structures with various periods and numbers of layers, which were fabricated using a high-order waveguide-mode interference field. A 442-nm laser was used to excite high-order waveguide modes in an asymmetric metal-cladding dielectric waveguide structure. The dispersion curve of the waveguide modes was theoretically analyzed, and the distribution of the interference field of high-order waveguide modes was numerically simulated using the finite-element method. The various dependences of the characteristics of hierarchical sub-wavelength photonic structures on the thickness and refractive index of the photoresist and the waveguide mode were investigated in detail. These hierarchical sub-wavelength photonic structures have various periods and numbers of layers and can be fabricated by a simple and low-cost method.
基金supported by the National Natural Science Foundation of China(No.52075467).
文摘With the development of the aerospace industry,space missions are becoming more complicated and diversified,and there is a demand for antenna mechanisms with a larger physical aperture.In this paper,a planar deployable mechanism is proposed,which can form a flat reflection surface with a small gap between plates.To this end,a novel large-scale two-dimensional deployable nine-grid planar antenna mechanism is designed.First,two antenna folding schemes and four supporting mechanism schemes are proposed.Through comparison analysis,the antenna configuration scheme with the best comprehensive performance is selected.A kinematic model of the deployable mechanism is established,and its kinematic characteristics are analyzed.Then,the correctness of the kinematic model is verified by comparing the analytical and simulation results of the kinematic model.Subsequently,a finite element model of the antenna is developed.Based on the response surface method,the structural parameters of the support rods of the antenna are optimized,and a set of optimized solutions with lightweight and high fundamental frequency characteristics are obtained.Finally,a prototype of the proposed nine-grid planar antenna is fabricated.The feasibility of the deployment principle and the rationality of the designed mechanism are verified by deployment experiments.
基金support by Australian Research Council under Discovery Project (Grant No. DP170103598)the Pawsey Supercomputing Centre through the National Computational Merit Allocation Scheme supported by the Australian Government and the Government of Western Australia
文摘In recent years, structure design and predictions based on global optimization approach as implemented in CALYPSO software have gained great success in accelerating the discovery of novel two-dimensional(2D) materials. Here we highlight some most recent research progress on the prediction of novel 2D structures, involving elements, metal-free and metal-containing compounds using CALYPSO package. Particular emphasis will be given to those 2D materials that exhibit unique electronic and magnetic properties with great potentials for applications in novel electronics, optoelectronics,magnetronics, spintronics, and photovoltaics. Finally, we also comment on the challenges and perspectives for future discovery of multi-functional 2D materials.
基金co-supported by the National Natural Science Foundation of China(No.51775500 and 51675482)the Open Found of the State Key Laboratory of Fluid Power and Mechatronic Systems of China(No.GZKF-201822)。
文摘Aviation fuel pumps of the future are required to be highly efficient and lightweight.As such,this work presents the designs of various mechanisms and structures of advanced twodimensional piston pumps for aero-engines,and their universal kinematic design methods are detailed herein.The efficiency of various piston pump prototypes was experimentally tested at various speeds in an open circuit.The experimental results indicate that two-dimensional piston pumps have a volumetric efficiency>91%and a higher power–mass ratio than conventional fuel pumps under all the conditions studied.Furthermore,the structural and material problems encountered during testing can provide a blueprint for further improvement of the design and processing of two-dimensional piston fuel pumps.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11274219 and 11264036)the STU Scientific Research Foundation forTalentsthe Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry,China
文摘We use the strong field approximation with a time window function controlling the release time of electrons to study the intra-cycle and inter-cycle interferences in few-cycle intense laser pulses impinging on He. The diffraction fringes, i.e., the vertical stripe-like structure, observed in the experimental two-dimensional photoelectron momentum distributions of Gopal et al. （2009 Phys. Rev. Lett. 103 053001） have been attributed to the interplay of the intra- and inter-cycle interferences. The pure numerical calculations by solving the time-dependent Schrrdinger equation are also performed and the results are compared with the experimental measurements directly. It has been found that the position of the stripe-like structure can be used to determine the duration of the laser pulses used in experiments.
文摘The electronic structure,magnetic,and optical properties of two-dimensional(2D)GaSe doped with rare earth elements X(X=Sc,Y,La,Ce,Eu)were calculated using the first-principles plane wave method based on den-sity functional theory.The results show that intrinsic 2D GaSe is a p-type nonmagnetic semiconductor with an indi-rect bandgap of 2.6611 eV.The spin-up and spin-down channels of Sc-,Y-,and La-doped 2D GaSe are symmetric,they are non-magnetic semiconductors.The magnetic moments of Ce-and Eu-doped 2D GaSe are 0.908μ_(B)and 7.163μ_(B),which are magnetic semiconductors.Impurity energy levels appear in both spin-up and spin-down chan-nels of Eu-doped 2D GaSe,which enhances the probability of electron transition.Compared with intrinsic 2D GaSe,the static dielectric constant of the doped 2D GaSe increases,and the polarization ability is strengthened.The ab-sorption spectrum of the doped 2D GaSe shifts in the low-energy direction,and the red-shift phenomenon occurs,which extends the absorption spectral range.The optical reflection coefficient of the doped 2D GaSe is improved in the low energy region,and the improvement of Eu-doped 2D GaSe is the most obvious.
基金the Natural Science Foundation of Universities of Jiangsu Province (No. 05KJB150110)
文摘An inorganic-organic hybrid thioantimonate（Ⅲ） [CH3（CH2）3NH3]2Sb4S7 1 with layered structure was synthesized by solvothermal method. 1 crystallizes in the triclinic system, space group P1 with a = 7.0124（11）, b = 11.919（2）, c =14.879（3）A, α = 108.791（3）, β= 102.441（3）, γ = 92.846（2）°, V= 1140.1（3）A3, Mr = 859.71, Z= 2, Do = 2.504 g/cm^3 ,μ = 5.324 mm^-1, F（000） = 804, S = 1.013, the Final R = 0.0297 and wR = 0.0618 for 3534 observed reflections with Ⅰ 〉 2 σ（Ⅰ）. 1 consists of [C4HgNH3]＋ cations and two-dimensional [Sb4ST]n^2n- anion which is composed of three SbS3 trigonal pyranaids and one SbS4 unit joined by sharing common comers. The anionic layers are stacked perpendicularly to the c axis of the unit cell forming two-dimensional channels between the layers. The [C4H9NH3]^＋ cations interdigitate in a bilayer and reside in the 2D channels leading to a sandwich-like arrangement of the anion and cations.
文摘By using the generalized characteristic analysis method, the two-dimensional four-wave Riemann problem for scalar conservation laws, which is nonconvex along the y direction, was studied. Riemann solutions, which involve the Guckenheimer structure, were constructed.
基金Supported by the National Natural Science Foundation of China(Nos.29873017, 20101004 and 29825504) the State BasicResearch Project(No.G2000077507).
文摘Open-framework materials are of great interest from both the theoretical and practical points of view due to their catalytic, absorbent, and ion-exchange properties. In the past decade, the study of structurally and chemically diverse open framework solids has been flourishing. A large variety of silicates, phosphates and carboxylates with open-framework structures have been synthesized with organic amines as templates. It has also been demonstrated that other oxysalts such as selenate, arsenate and germanate are used to build up open architectures. As far as the sulfate is concerned,
基金supported by the State Key Basic Research Program of China under Grant No.2006CB921607China-Australia Special Fund for Science and Technology
文摘A two-dimensional photonic crystal with a one-dimensional periodic dielectric background is proposed. The photonic band modulation effects due to the periodic background are investigated based on the plane wave expansion method. We find that periodic modulation of the dielectric background greatly alters photonic band structures, especially for the E-polarization modes. The number, width and position of the photonic band gaps （PBGs） sensitively depend on the structure parameters （the layer thicknesses and dielectric constants） of the one-dimensional periodic background,
基金supported by the National Natural Science Foundation of China (Grant No. 62004080)the Postdoctoral Innovative Talents Supporting Program (Grant No. BX20190143)the China Postdoctoral Science Foundation (Grant No. 2020M670834)。
文摘Two-dimensional(2D) layered perovskites have emerged as potential alternates to traditional three-dimensional(3D)analogs to solve the stability issue of perovskite solar cells. In recent years, many efforts have been spent on manipulating the interlayer organic spacing cation to improve the photovoltaic properties of Dion–Jacobson(DJ) perovskites. In this work, a serious of cycloalkane(CA) molecules were selected as the organic spacing cation in 2D DJ perovskites, which can widely manipulate the optoelectronic properties of the DJ perovskites. The underlying relationship between the CA interlayer molecules and the crystal structures, thermodynamic stabilities, and electronic properties of 58 DJ perovskites has been investigated by using automatic high-throughput workflow cooperated with density-functional(DFT) calculations.We found that these CA-based DJ perovskites are all thermodynamic stable. The sizes of the cycloalkane molecules can influence the degree of inorganic framework distortion and further tune the bandgaps with a wide range of 0.9–2.1 eV.These findings indicate the cycloalkane molecules are suitable as spacing cation in 2D DJ perovskites and provide a useful guidance in designing novel 2D DJ perovskites for optoelectronic applications.
基金supported by the National Natural Science Foundation of China (No. 20873021,21003020)New Century Excellent Talent Supported Plan of Fujian Province (SXSJRC2007-21)
文摘Two compounds with 3-methylbenzoic acid（HL） [Co（L）2（4,4＇-bipy）]n 1 and [Zn2（L）4（4,4＇-bipy）]n 2（L = 3-methylbenzoic acid） have been hydrothermally synthesized directly and characterized by single-crystal X-ray diffraction analysis,elemental analyses,IR spectra and ultraviolet-visible diffuse reflection integral spectra（UV-Vis DRIS）.The two compounds are both one-dimensional infinite chains.The structural difference is that 1 is a double-chain structure and 2 is only a single chain one.At the same time,the carboxylate groups adopt different modes in the two compounds,relatively.Additionally,in order to explore the structural characteristic,two-dimen-sional IR spectra are investigated for 1 and 2.Photo-luminescent property of 2 is also researched in detail.
基金supported by the grant AX-1593(JCGZ)and AX1730(BC)from the Welch Foundation
文摘Solvothermal reaction of 3-aminoisonicotinic acid（Haina） and Cu（NO_3）_2·2.5H_2O gave a novel twodimensional（2D） microporous metal–organic framework, [Cu（aina）_2（DMF）]·DMF（1, DMF = N,N-dimethylformamide）. Single-crystal X-ray crystallographic study of compound 1 revealed that Cu（II）ions are linked by ainaàligands forming square grid-like layers, which stack together via multiple hydrogen bonding interactions. The solvent-free framework of 1a displayed considerable porosity（void = 46.5%） with one-dimensional（1D） open channels（4.7 ？ ？ 4.8 ？） functionalized by amino groups.Gas sorption measurements of 1 revealed selective carbon dioxide（CO_2） and acetylene（C_2H_2） adsorption over methane（CH_4） and nitrogen（N_2） at ambient temperature.
