The modified embedded atom method (MEAM) is an empirical extension of the embedded atom method (EAM) that includes angular forces. By fitted to the lattice constants, the cohesive energy, the APE (anti-phase boundary)...The modified embedded atom method (MEAM) is an empirical extension of the embedded atom method (EAM) that includes angular forces. By fitted to the lattice constants, the cohesive energy, the APE (anti-phase boundary) energy, and the vacancy formation energy of TiAl, an accurate MEAM potential is obtained for the TiAl system with L10 structure. The calculation results of the properties of TiAl are in good agreement with experiments and the results of first principle (F.P.) calculations.展开更多
Based on the principle of minimal energy and the coherent rotation model, two types of the jump phenomena, complete and incomplete jump phenomenon, are proved to exist in the angular dependence of the exchange bias wi...Based on the principle of minimal energy and the coherent rotation model, two types of the jump phenomena, complete and incomplete jump phenomenon, are proved to exist in the angular dependence of the exchange bias with noncollinear unidirectional and uniaxial anisotropies. It is found that the transition between complete and incomplete jump phenomena occurs on condition that the exchange-coupling constant exceeds a critical value. Additionally, two different modes of the magnetization rotation, the whole-plane rotation, and the half-plane rotation are present in the magnetization reversal process, and they are dependent on the direction of the external field. Furthermore, the equations of the critical angle, at which orientation the exchange bias field reaches a maximum value and the coercivity disappears, are also derived in this paper. The numerical calculations in this paper are consistent with the relevant experimental observations, indicating that our method to study the angular dependence of the exchange bias as well as the magnetization reversal behaviors is valid. Our discussion about the jump phenomenon, the critical angle, and the modes of the magnetization reversal can explain the observed differences in results between different experiments.展开更多
We determine the structure parameters for the asymmetric heteronuclear diatomic molecule HeH2＋ at several internuclear distances with the molecular wavefunctions obtained by solving the time-independent Schr6dinger e...We determine the structure parameters for the asymmetric heteronuclear diatomic molecule HeH2＋ at several internuclear distances with the molecular wavefunctions obtained by solving the time-independent Schr6dinger equation with B-spline basis. Then the angular dependence of strong-field ionization rates of HeH2＋ are investigated with the molecular tunneling ionization theory. We show that the shape of several lowly excited states （i.e. 2pσ, 2pπ, 3dσ） for HeH2＋ are reflected in the orientation dependent ionization rates very well, however, the angle-dependent ionization rate fails to follow the angular distribution of the asymptotic electron density for the ground state lsσ. We also show that the internuclear distance dependent ionization probabilities are in a good agreement with the more accurate result obtained from the numerical solution of the time-dependent Schr6dinger equation.展开更多
We theoretically study the dependence of photoelectron angular distribution on laser polarization direction in nitrogen molecules. The approach is based on the time-dependent density functional theory at the level of ...We theoretically study the dependence of photoelectron angular distribution on laser polarization direction in nitrogen molecules. The approach is based on the time-dependent density functional theory at the level of local density approximation complemented by self-interaction correction. It is found that photoelectron emission in one photon regime could be considered as a probing tool for the main character of different types of molecular orbitals （σ or π）. The pattern of emitted photoelectrons strongly depends on the polarized angle of the laser, for σ orbital, the number of photoelectron decreases with increasing the polarized angle, while for π orbital, it has the inverse relation to the polarized angle, which reveals the multi-electron effect in molecules. On the other hand, concerning the total photoelectron emission, one should take into account a few occupied orbitals instead of only the outmost one.展开更多
X-Ray Absorption Spectroscopy (XAS) on the carbon K edge of carbon nanostructures (nanotubes, nanofibers, nanowalls) is reported here. They are grown on plain SiO2 (8 nm thick)/Si(100) substrates by a Plasma and Hot F...X-Ray Absorption Spectroscopy (XAS) on the carbon K edge of carbon nanostructures (nanotubes, nanofibers, nanowalls) is reported here. They are grown on plain SiO2 (8 nm thick)/Si(100) substrates by a Plasma and Hot Filaments-enhanced Catalytic Chemical Vapor Deposition (PE HF CCVD) process. The morphology and the nature of these carbon nanostructures are characterized by SEM, TEM and Raman spectroscopy. According to conditions of catalyst preparation and DC HF CCVD process, carbon nanotubes (CNTs), carbon nanofibers (CNFs), carbon nanowalls (CNWs), carbon nanoparticles (CNPs) with different orientation of the graphene plans or shells can be prepared. From the angular dependence of the incident light and geometrical morphology of the nanostructures, wide variations of the C K-edge intensity of the transitions to the empty π* and σ* states occur. A full lineshape analysis of the XAS spectra has been carried out using a home-made software, allowing estimating the relative proportion of π* and σ* transitions. A geometrical model of the angular dependence with the incidence angle of the light and the morphology of the carbon nanostructures is derived. With normalization to the HOPG (Highly Oriented Pyrolytic Graphite graphite) reference case, a degree of alignment can be extracted which is representative of the localized orientation of the graphitic carbon π bonds, accounting not only for the overall orientation, but also for local defects like impurities incorporation, structural defects ... This degree of alignment shows good agreement with SEM observations. Thus CNTs films display degrees of alignment around 50%, depending on the occurrence of defects in the course of the growth, whereas no special alignment can be detected with CNFs and CNPs, and a weak one (about 20%) is detected on CNWs.展开更多
Based on the theoretical models for light nuclei, the calculations of reaction cross sections and the angular distributions for d ＋^8Li reaction are performed. Since all of the particle emissions are from the compoun...Based on the theoretical models for light nuclei, the calculations of reaction cross sections and the angular distributions for d ＋^8Li reaction are performed. Since all of the particle emissions are from the compound nucleus to the discrete levels, the angular momentum coupling effect in pre-equilibrium mechanism is taken into account. The three- body break-up process and the recoil effect are involved. The theoretical calculated results are compared to existing experimental data.展开更多
The Paulie’s principle is used for development of the orbital-free (OF) version of the density functional theory. On the example of the three-atomic clusters, Al<sub>3</sub>, Si<sub>3</sub>, a...The Paulie’s principle is used for development of the orbital-free (OF) version of the density functional theory. On the example of the three-atomic clusters, Al<sub>3</sub>, Si<sub>3</sub>, and C<sub>3</sub>, it is shown that the OF approach may lead to equilibrium configurations of atomic systems with both the metallic and covalent bonding. The equilibrium interatomic distances, interbonding angles and binding energies are found in good accordance with the known data. Results will be useful for developing of theoretical study of huge molecules and nanoparticles.展开更多
The resonant frequencies of the excited surface waves on a metal hole array with respect to the incident angle were studied in the terahertz region.The experimental and theoretical results demonstrate that the resonan...The resonant frequencies of the excited surface waves on a metal hole array with respect to the incident angle were studied in the terahertz region.The experimental and theoretical results demonstrate that the resonant peak of surface wave excitation splits into two when transmitted through a metal hole array off-normally.The high-order mode with resonant frequency above the cutoff frequency fc(plasma frequency effect)has a shorter attenuation length than that of the low-order mode whose resonant frequency is below fc.The reason is that the high-order mode is a coupled mode consisting of surface wave and hole modes,while the low-order mode is just an excited surface wave(which can be considered as the spoof surface plasmons).Our investigation may open a door to distinguish the spoof surface plasmons and the coupled modes of surface waves and hole modes.展开更多
High-spin states in 161Er have been studied experimentally using the 150Nd（16O, 5n） reaction at a beam energy of 86 MeV. The relatively enhanced E1 transitions between the 5/2＋[642] and 3/2-[521] bands are observed...High-spin states in 161Er have been studied experimentally using the 150Nd（16O, 5n） reaction at a beam energy of 86 MeV. The relatively enhanced E1 transitions between the 5/2＋[642] and 3/2-[521] bands are observed in 161Er, and the B（E1） values are extracted experimentally. The systematics of the R（E1） values in the N = 93 isotones are presented. It is found that the strength of the E1 transitions obviously exhibits angular momentum dependence, and the occurrence of the relatively enhanced E1 transitions could be attributed to octupole softness.展开更多
基金the National Natural Science Foundation of China.
文摘The modified embedded atom method (MEAM) is an empirical extension of the embedded atom method (EAM) that includes angular forces. By fitted to the lattice constants, the cohesive energy, the APE (anti-phase boundary) energy, and the vacancy formation energy of TiAl, an accurate MEAM potential is obtained for the TiAl system with L10 structure. The calculation results of the properties of TiAl are in good agreement with experiments and the results of first principle (F.P.) calculations.
基金supported by the Fundamental Research Foundation of Shanxi Province,China(Grant No.2013021010-3)the Natural Science Foundation of Shanxi Normal University,China(Grant No.872014)
文摘Based on the principle of minimal energy and the coherent rotation model, two types of the jump phenomena, complete and incomplete jump phenomenon, are proved to exist in the angular dependence of the exchange bias with noncollinear unidirectional and uniaxial anisotropies. It is found that the transition between complete and incomplete jump phenomena occurs on condition that the exchange-coupling constant exceeds a critical value. Additionally, two different modes of the magnetization rotation, the whole-plane rotation, and the half-plane rotation are present in the magnetization reversal process, and they are dependent on the direction of the external field. Furthermore, the equations of the critical angle, at which orientation the exchange bias field reaches a maximum value and the coercivity disappears, are also derived in this paper. The numerical calculations in this paper are consistent with the relevant experimental observations, indicating that our method to study the angular dependence of the exchange bias as well as the magnetization reversal behaviors is valid. Our discussion about the jump phenomenon, the critical angle, and the modes of the magnetization reversal can explain the observed differences in results between different experiments.
基金Supported by the National Natural Science Foundation of China under Grant Nos.11164025,11044007,11064013the Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant Nos.20096203110001,20116203120001the Foundation of Northwest Normal University under Grant No.NWNU-KJCXGC-03-62
文摘We determine the structure parameters for the asymmetric heteronuclear diatomic molecule HeH2＋ at several internuclear distances with the molecular wavefunctions obtained by solving the time-independent Schr6dinger equation with B-spline basis. Then the angular dependence of strong-field ionization rates of HeH2＋ are investigated with the molecular tunneling ionization theory. We show that the shape of several lowly excited states （i.e. 2pσ, 2pπ, 3dσ） for HeH2＋ are reflected in the orientation dependent ionization rates very well, however, the angle-dependent ionization rate fails to follow the angular distribution of the asymptotic electron density for the ground state lsσ. We also show that the internuclear distance dependent ionization probabilities are in a good agreement with the more accurate result obtained from the numerical solution of the time-dependent Schr6dinger equation.
文摘We theoretically study the dependence of photoelectron angular distribution on laser polarization direction in nitrogen molecules. The approach is based on the time-dependent density functional theory at the level of local density approximation complemented by self-interaction correction. It is found that photoelectron emission in one photon regime could be considered as a probing tool for the main character of different types of molecular orbitals （σ or π）. The pattern of emitted photoelectrons strongly depends on the polarized angle of the laser, for σ orbital, the number of photoelectron decreases with increasing the polarized angle, while for π orbital, it has the inverse relation to the polarized angle, which reveals the multi-electron effect in molecules. On the other hand, concerning the total photoelectron emission, one should take into account a few occupied orbitals instead of only the outmost one.
文摘X-Ray Absorption Spectroscopy (XAS) on the carbon K edge of carbon nanostructures (nanotubes, nanofibers, nanowalls) is reported here. They are grown on plain SiO2 (8 nm thick)/Si(100) substrates by a Plasma and Hot Filaments-enhanced Catalytic Chemical Vapor Deposition (PE HF CCVD) process. The morphology and the nature of these carbon nanostructures are characterized by SEM, TEM and Raman spectroscopy. According to conditions of catalyst preparation and DC HF CCVD process, carbon nanotubes (CNTs), carbon nanofibers (CNFs), carbon nanowalls (CNWs), carbon nanoparticles (CNPs) with different orientation of the graphene plans or shells can be prepared. From the angular dependence of the incident light and geometrical morphology of the nanostructures, wide variations of the C K-edge intensity of the transitions to the empty π* and σ* states occur. A full lineshape analysis of the XAS spectra has been carried out using a home-made software, allowing estimating the relative proportion of π* and σ* transitions. A geometrical model of the angular dependence with the incidence angle of the light and the morphology of the carbon nanostructures is derived. With normalization to the HOPG (Highly Oriented Pyrolytic Graphite graphite) reference case, a degree of alignment can be extracted which is representative of the localized orientation of the graphitic carbon π bonds, accounting not only for the overall orientation, but also for local defects like impurities incorporation, structural defects ... This degree of alignment shows good agreement with SEM observations. Thus CNTs films display degrees of alignment around 50%, depending on the occurrence of defects in the course of the growth, whereas no special alignment can be detected with CNFs and CNPs, and a weak one (about 20%) is detected on CNWs.
基金supported by IAEA Coordinated Research Projects (CRPs) on Parameters for Calculation of Nuclear Reactions of Relevance to Non-energy Nuclear Applications under Grant No.12842/R2
文摘Based on the theoretical models for light nuclei, the calculations of reaction cross sections and the angular distributions for d ＋^8Li reaction are performed. Since all of the particle emissions are from the compound nucleus to the discrete levels, the angular momentum coupling effect in pre-equilibrium mechanism is taken into account. The three- body break-up process and the recoil effect are involved. The theoretical calculated results are compared to existing experimental data.
文摘The Paulie’s principle is used for development of the orbital-free (OF) version of the density functional theory. On the example of the three-atomic clusters, Al<sub>3</sub>, Si<sub>3</sub>, and C<sub>3</sub>, it is shown that the OF approach may lead to equilibrium configurations of atomic systems with both the metallic and covalent bonding. The equilibrium interatomic distances, interbonding angles and binding energies are found in good accordance with the known data. Results will be useful for developing of theoretical study of huge molecules and nanoparticles.
基金This work is supported by the National Natural Science Foundation of China(11174207,61138001,61007059,61205094)the Key Scientific and Technological Project of Science and Technology Commission of Shanghai Municipality(11DZ1110800)+2 种基金the Major National Development Project of Scientific Instrument and Equipment(2011YQ150021)National Program on Key Basic Research Project of China(2012CB934203)the Leading Academic Discipline Project of Shanghai Municipal Government(S30502).
文摘The resonant frequencies of the excited surface waves on a metal hole array with respect to the incident angle were studied in the terahertz region.The experimental and theoretical results demonstrate that the resonant peak of surface wave excitation splits into two when transmitted through a metal hole array off-normally.The high-order mode with resonant frequency above the cutoff frequency fc(plasma frequency effect)has a shorter attenuation length than that of the low-order mode whose resonant frequency is below fc.The reason is that the high-order mode is a coupled mode consisting of surface wave and hole modes,while the low-order mode is just an excited surface wave(which can be considered as the spoof surface plasmons).Our investigation may open a door to distinguish the spoof surface plasmons and the coupled modes of surface waves and hole modes.
基金Supported by National Natural Science Foundation of China (10825522, 10735010, 10575120)National Basic Research Program of China (2007CB815001)Chinese Academy of Sciences
文摘High-spin states in 161Er have been studied experimentally using the 150Nd（16O, 5n） reaction at a beam energy of 86 MeV. The relatively enhanced E1 transitions between the 5/2＋[642] and 3/2-[521] bands are observed in 161Er, and the B（E1） values are extracted experimentally. The systematics of the R（E1） values in the N = 93 isotones are presented. It is found that the strength of the E1 transitions obviously exhibits angular momentum dependence, and the occurrence of the relatively enhanced E1 transitions could be attributed to octupole softness.
