Far-field properties dependent on array scale, separation, element width and emitted wavelength are system atically analyzed theoretically and experimentally. An array model based on the finite-difference method is es...Far-field properties dependent on array scale, separation, element width and emitted wavelength are system atically analyzed theoretically and experimentally. An array model based on the finite-difference method is established to simulate the far-field profile of the coherent arrays. Some important conclusions are obtained. To achieve a higher quality beam, it is necessary to decrease separation between elements, or to increase the element width. Higher brightness can be achieved in the array with larger scale. Emitted wavelength also has an influence on the far-field profile. These analyses can be extended to the future design of coherent vertical cavity surface emitting laser arrays.展开更多
The morphological changes of ABA amphiphilic triblock copolymer micelles in dilute solution were systematically studied by tuning the solvent property using self-consistent field simulation. The solvent property was t...The morphological changes of ABA amphiphilic triblock copolymer micelles in dilute solution were systematically studied by tuning the solvent property using self-consistent field simulation. The solvent property was tuned by changing the Flory-Huggins interaction parameters between each type of blocks and solvent, respectively. The simulation results show that by changing the solvent properties, a series of micelle morphologies such as vesicle, cage-like, ring-shaped, rod-like and spherical micelle morphologies can be obtained. Variations of the free energy of the solution system and the surface area of micelles with the Flory-Huggins interaction parameters were calculated to better understand the effect of solvent property on micelle morphologies. In addition, a phase diagram showing the morphological changes of micelles with the Flory-Huggins interaction parameters is provided.展开更多
Magnetic properties and magnetization processes of Co nanowire arrays with various packing densities are investigated by means of object-oriented micromagnetic framework(OOMMF) software package with finite differenc...Magnetic properties and magnetization processes of Co nanowire arrays with various packing densities are investigated by means of object-oriented micromagnetic framework(OOMMF) software package with finite difference micromagnetic simulations. The packing density of nanowires is changed with the diameter, number of nanowires and center-to-center spacing between the wires. The magnetization reversal mechanism and squareness of the hysteresis loops of the nanowire arrays are very sensitive to the packing density of nanowires. Clear steps and plateaux on the demagnetization are visible,which turns out that dipolar interactions among the wires have a significant influence on switching field.展开更多
Magnetics,ferroelectrics,and multiferroics have attracted great attentions because they are not only extremely im-portant for investigating fundamental physics,but also have important applications in information techn...Magnetics,ferroelectrics,and multiferroics have attracted great attentions because they are not only extremely im-portant for investigating fundamental physics,but also have important applications in information technology.Here,recent computational studies on magnetism and ferroelectricity are reviewed.We first give a brief introduction to magnets,fer-roelectrics,and multiferroics.Then,theoretical models and corresponding computational methods for investigating these materials are presented.In particular,a new method for computing the linear magnetoelectric coupling tensor without applying an external field in the first principle calculations is proposed for the first time.The functionalities of our home-made Property Analysis and Simulation Package for materials(PASP)and its applications in the field of magnetism and ferroelectricity are discussed.Finally,we summarize this review and give a perspective on possible directions of future computational studies on magnetism and ferroelectricity.展开更多
We present the specific ab-initio calculations that detail the variations of perovskite BaZrO3 caused by in-plane strain. Specifically, the internal relaxation, which was not captured in the widely used biaxial strain...We present the specific ab-initio calculations that detail the variations of perovskite BaZrO3 caused by in-plane strain. Specifically, the internal relaxation, which was not captured in the widely used biaxial strain model, was included in a complementary manner to lattice relaxation. Density functional theory as well as a hybrid functional method based on a plane wave basis set was employed to calculate the lattice structure, elastic constants, electronic properties and optical properties of perovskite BaZrO3. The lattice parameter c exhibited a clear linear dependence on the imposed in-plane strain, but the Poisson's ratio caused by internal relaxation was smaller than the elastic deformation, indicating an "inelastic" or "plastic" relaxation manner caused by the introduction of internal relaxation. As a result, the related electronic and optical properties of perovskite BaZrO3 were also strongly affected by the in-plane strain, which revealed an effective way to adjust the properties of perovskite BaZrO3 via internal relaxation.展开更多
Taking into account defect density in WSe2,interface recombination between ZnO and WSe2,we presented a simulation study of ZnO/crystalline WSe2 heterojunction(HJ) solar cell using wxAMPS simulation software.The opti...Taking into account defect density in WSe2,interface recombination between ZnO and WSe2,we presented a simulation study of ZnO/crystalline WSe2 heterojunction(HJ) solar cell using wxAMPS simulation software.The optimal conversion efficiency 39.07%for n-ZnO/p-c-WSe2 HJ solar cell can be realized without considering the impact of defects.High defect density(〉 1.0×10^11cm^-2) in c-WSe2 and large trap cross-section(〉 1.0×10^-10cm^2) have serious impact on solar cell efficiency.A thin p-WSe2 layer is intentionally inserted between ZnO layer and c-WSe2 to investigate the effect of the interface recombination.The interface properties are very crucial to the performance of ZnO/c-WSe2 HJ solar cell.The affinity of ZnO value range between 3.7-4.5 eV gives the best conversion efficiency.展开更多
Through molecular dynamics(MD) simulation, the dependencies of temperature, grain size and strain rate on the mechanical properties were studied. The simulation results demonstrated that the strain rate from 0.05 to...Through molecular dynamics(MD) simulation, the dependencies of temperature, grain size and strain rate on the mechanical properties were studied. The simulation results demonstrated that the strain rate from 0.05 to 2 ns–1 affected the Young's modulus of nickel nanowires slightly, whereas the yield stress increased. The Young's modulus decreased approximately linearly; however, the yield stress firstly increased and subsequently dropped as the temperature increased. The Young's modulus and yield stress increased as the mean grain size increased from 2.66 to 6.72 nm. Moreover, certain efforts have been made in the microstructure evolution with mechanical properties association under uniaxial tension. Certain phenomena such as the formation of twin structures, which were found in nanowires with larger grain size at higher strain rate and lower temperature, as well as the movement of grain boundaries and dislocation, were detected and discussed in detail. The results demonstrated that the plastic deformation was mainly accommodated by the motion of grain boundaries for smaller grain size. However, for larger grain size, the formations of stacking faults and twins were the main mechanisms of plastic deformation in the polycrystalline nickel nanowire.展开更多
Local melting and the eutectic film and liquation crack formation mechanisms during friction spot weld- ing (FSpW) of Al-Zn-Mg-Cu alloy were studied by both experiment and finite element simulation. Their effects on...Local melting and the eutectic film and liquation crack formation mechanisms during friction spot weld- ing (FSpW) of Al-Zn-Mg-Cu alloy were studied by both experiment and finite element simulation. Their effects on mechanical properties of the joint were examined. When the welding heat input was high, the peak temperature in the stir zone was higher than the incipient melting temperature of the Al-Zn-Mg-Cu alloy. This resulted in local melting along the grain boundaries in this zone. In the retreating stage of the welding process, the formed liquid phase was driven by the flowing plastic material and redistributed as a "U-shaped" line in the stir zone. In the following cooling stage, this liquid phase transformed into eutectic films and liquation cracks. As a result, a new characteristic of"U" line that consisted of eutectic films and liquation cracks is formed in the FSpWjoin. This "U" line was located in the high stress region when the FSpW joint was loaded, thus it was adverse to the mechanical properties of the FSpW joint. During tensile shear tests, the "U" line became a preferred crack propagation path, resulting in the occurrence of brittle fracture.展开更多
The single-layer black phosphorus is characterized by its puckered configuration that pos- sesses the hinge-like behavior, which leads to the highly anisotropic in-plane Poisson's ratios and the negative out-of-plane...The single-layer black phosphorus is characterized by its puckered configuration that pos- sesses the hinge-like behavior, which leads to the highly anisotropic in-plane Poisson's ratios and the negative out-of-plane Poisson's ratio. We demonstrate that the hinge-like mechanism can be described by the angle-angle cross interaction, which, combined with the bond stretching and angle bending interactions, is able to provide a good description for the mechanical properties of single-layer black phosphorus. We also propose a nonlinear angle-angle cross interaction, which follows the form of Stillinger-Weber potential and can be advantageous for molecular dynamics simulations of single-layer black phosphorus under large deformation.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 61376049,61076044,61107026 and 61204011the Scientific Research Fund Project of Municipal Education Commission of Beijing under Grant No PXM2014-014204-07-000018
文摘Far-field properties dependent on array scale, separation, element width and emitted wavelength are system atically analyzed theoretically and experimentally. An array model based on the finite-difference method is established to simulate the far-field profile of the coherent arrays. Some important conclusions are obtained. To achieve a higher quality beam, it is necessary to decrease separation between elements, or to increase the element width. Higher brightness can be achieved in the array with larger scale. Emitted wavelength also has an influence on the far-field profile. These analyses can be extended to the future design of coherent vertical cavity surface emitting laser arrays.
基金financially supported by the National Natural Science Foundation of China(No.21104078)the Project of Science and Technology of Jilin Province,China(No.201201096)the Scientific Research Starting Foundation for the Jilin Agricultural University,China(No.201212)
文摘The morphological changes of ABA amphiphilic triblock copolymer micelles in dilute solution were systematically studied by tuning the solvent property using self-consistent field simulation. The solvent property was tuned by changing the Flory-Huggins interaction parameters between each type of blocks and solvent, respectively. The simulation results show that by changing the solvent properties, a series of micelle morphologies such as vesicle, cage-like, ring-shaped, rod-like and spherical micelle morphologies can be obtained. Variations of the free energy of the solution system and the surface area of micelles with the Flory-Huggins interaction parameters were calculated to better understand the effect of solvent property on micelle morphologies. In addition, a phase diagram showing the morphological changes of micelles with the Flory-Huggins interaction parameters is provided.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51401001,51371002,and 51331003)the International S&T Cooperation Program of China(Grant No.2015DFG52020)
文摘Magnetic properties and magnetization processes of Co nanowire arrays with various packing densities are investigated by means of object-oriented micromagnetic framework(OOMMF) software package with finite difference micromagnetic simulations. The packing density of nanowires is changed with the diameter, number of nanowires and center-to-center spacing between the wires. The magnetization reversal mechanism and squareness of the hysteresis loops of the nanowire arrays are very sensitive to the packing density of nanowires. Clear steps and plateaux on the demagnetization are visible,which turns out that dipolar interactions among the wires have a significant influence on switching field.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11825403,12188101,and 11804138)the Natural Science Foundation of Anhui Province,China(Grant No.1908085MA10)the Opening Foundation of the State Key Laboratory of Surface Physics of Fudan University(Grant No.KF2019_07)。
文摘Magnetics,ferroelectrics,and multiferroics have attracted great attentions because they are not only extremely im-portant for investigating fundamental physics,but also have important applications in information technology.Here,recent computational studies on magnetism and ferroelectricity are reviewed.We first give a brief introduction to magnets,fer-roelectrics,and multiferroics.Then,theoretical models and corresponding computational methods for investigating these materials are presented.In particular,a new method for computing the linear magnetoelectric coupling tensor without applying an external field in the first principle calculations is proposed for the first time.The functionalities of our home-made Property Analysis and Simulation Package for materials(PASP)and its applications in the field of magnetism and ferroelectricity are discussed.Finally,we summarize this review and give a perspective on possible directions of future computational studies on magnetism and ferroelectricity.
基金Funded by the National Natural Science Foundation of China(No.51502179)the Colleges and Universities in Hebei Province Science and Technology Research Project(No.YQ2014033)the Hebei Key Discipline Construction Project(B2012210004 and E2013210038)
文摘We present the specific ab-initio calculations that detail the variations of perovskite BaZrO3 caused by in-plane strain. Specifically, the internal relaxation, which was not captured in the widely used biaxial strain model, was included in a complementary manner to lattice relaxation. Density functional theory as well as a hybrid functional method based on a plane wave basis set was employed to calculate the lattice structure, elastic constants, electronic properties and optical properties of perovskite BaZrO3. The lattice parameter c exhibited a clear linear dependence on the imposed in-plane strain, but the Poisson's ratio caused by internal relaxation was smaller than the elastic deformation, indicating an "inelastic" or "plastic" relaxation manner caused by the introduction of internal relaxation. As a result, the related electronic and optical properties of perovskite BaZrO3 were also strongly affected by the in-plane strain, which revealed an effective way to adjust the properties of perovskite BaZrO3 via internal relaxation.
基金Project supported by the Natural Science Foundation of Zhejiang Province(No.LY17F040001)the Open Project Program of Surface Physics Laboratory(National Key Laboratory)of Fudan University(No.KF2015_02)+2 种基金the Open Project Program of National Laboratory for Infrared Physics,Chinese Academy of Sciences(No.M201503)the Zhejiang Provincial Science and Technology Key Innovation Team(No.2011R50012)the Zhejiang Provincial Key Laboratory(No.2013E10022)
文摘Taking into account defect density in WSe2,interface recombination between ZnO and WSe2,we presented a simulation study of ZnO/crystalline WSe2 heterojunction(HJ) solar cell using wxAMPS simulation software.The optimal conversion efficiency 39.07%for n-ZnO/p-c-WSe2 HJ solar cell can be realized without considering the impact of defects.High defect density(〉 1.0×10^11cm^-2) in c-WSe2 and large trap cross-section(〉 1.0×10^-10cm^2) have serious impact on solar cell efficiency.A thin p-WSe2 layer is intentionally inserted between ZnO layer and c-WSe2 to investigate the effect of the interface recombination.The interface properties are very crucial to the performance of ZnO/c-WSe2 HJ solar cell.The affinity of ZnO value range between 3.7-4.5 eV gives the best conversion efficiency.
基金Supported by the National Natural Science Foundation of China(11102139,11472195)the Natural Science Foundation of Hubei Province of China(2014CFB713)
文摘Through molecular dynamics(MD) simulation, the dependencies of temperature, grain size and strain rate on the mechanical properties were studied. The simulation results demonstrated that the strain rate from 0.05 to 2 ns–1 affected the Young's modulus of nickel nanowires slightly, whereas the yield stress increased. The Young's modulus decreased approximately linearly; however, the yield stress firstly increased and subsequently dropped as the temperature increased. The Young's modulus and yield stress increased as the mean grain size increased from 2.66 to 6.72 nm. Moreover, certain efforts have been made in the microstructure evolution with mechanical properties association under uniaxial tension. Certain phenomena such as the formation of twin structures, which were found in nanowires with larger grain size at higher strain rate and lower temperature, as well as the movement of grain boundaries and dislocation, were detected and discussed in detail. The results demonstrated that the plastic deformation was mainly accommodated by the motion of grain boundaries for smaller grain size. However, for larger grain size, the formations of stacking faults and twins were the main mechanisms of plastic deformation in the polycrystalline nickel nanowire.
基金supports by the Project of Guangdong Provincial Science and Technology Program(2015B090922011)the 2017 GDAS’ Special Project of Science and Technology Development(2017GDASCX-0847)the Project of Guangdong Provincial Key Laboratory(2012A061400011)
文摘Local melting and the eutectic film and liquation crack formation mechanisms during friction spot weld- ing (FSpW) of Al-Zn-Mg-Cu alloy were studied by both experiment and finite element simulation. Their effects on mechanical properties of the joint were examined. When the welding heat input was high, the peak temperature in the stir zone was higher than the incipient melting temperature of the Al-Zn-Mg-Cu alloy. This resulted in local melting along the grain boundaries in this zone. In the retreating stage of the welding process, the formed liquid phase was driven by the flowing plastic material and redistributed as a "U-shaped" line in the stir zone. In the following cooling stage, this liquid phase transformed into eutectic films and liquation cracks. As a result, a new characteristic of"U" line that consisted of eutectic films and liquation cracks is formed in the FSpWjoin. This "U" line was located in the high stress region when the FSpW joint was loaded, thus it was adverse to the mechanical properties of the FSpW joint. During tensile shear tests, the "U" line became a preferred crack propagation path, resulting in the occurrence of brittle fracture.
基金supported by the Recruitment Program of Global Youth Experts of Chinathe National Natural Science Foundation of China (NNSFC) under grant no. 11504225the startup funding from Shanghai University
文摘The single-layer black phosphorus is characterized by its puckered configuration that pos- sesses the hinge-like behavior, which leads to the highly anisotropic in-plane Poisson's ratios and the negative out-of-plane Poisson's ratio. We demonstrate that the hinge-like mechanism can be described by the angle-angle cross interaction, which, combined with the bond stretching and angle bending interactions, is able to provide a good description for the mechanical properties of single-layer black phosphorus. We also propose a nonlinear angle-angle cross interaction, which follows the form of Stillinger-Weber potential and can be advantageous for molecular dynamics simulations of single-layer black phosphorus under large deformation.