Atomistic potentials for cupric element and cupric oxide are derived based on the analytical bond-order scheme that was presented by Brenner [Brenner D W, Erratum： Empirical potential for hydrocarbons for use in simu...Atomistic potentials for cupric element and cupric oxide are derived based on the analytical bond-order scheme that was presented by Brenner [Brenner D W, Erratum： Empirical potential for hydrocarbons for use in simulating the chemical vapor deposition of diamond films, Phys. Rev. B 1992, 46 1948]. In this paper, for the pure cupric element, the energy and structural parameters for several bulk phases as well as dimmer structure are well reproduced. The reference data are taken from our density functional theory calculations and the available experiments. The model potential also provides a good description of the bulk properties of various solid structures of cupric oxide compound structures, including cohesive energies, lattice parameters, and elastic constants.展开更多
The point defects and their related physical properties in L10 FePt are investigated by molecular dynamics simulations based on an analytic bond-order potential. The calculated results agree well with the experimental...The point defects and their related physical properties in L10 FePt are investigated by molecular dynamics simulations based on an analytic bond-order potential. The calculated results agree well with the experimental value, indicating that the analytic bond-order potential is suitable to describe the structural properties and surface energies of the FePt alloy in the L10 phase. However, the calculated vacancy formation energy of an Fe atom is higher than that of a Pt atom, which disagrees with some other previously calculated results. This result indicates that the analytic bond-order potential is unable to describe the related point defect properties. The analytic bond-order potential needs to be modified in order to study these defect properties of an FePt alloy.展开更多
The lattice parameters, elastic constants, cohesive energy, structural energy differences, as well as the properties of point defects and planar defects of hexagonal closepacked yttrium （hcpY） have been studied with...The lattice parameters, elastic constants, cohesive energy, structural energy differences, as well as the properties of point defects and planar defects of hexagonal closepacked yttrium （hcpY） have been studied with ab initio density functional theory for constructing an ex tensive database. Based on an analytical bondorder poial scheme, empirical manybody interatomic potential for hcpY has been developed. The model is fitted to some properties of Y, e.g., the lattice parameters, elastic constants, bulk modulus, cohesive energy, vacancy formation energy, and the structural energy differences. The present potential has ability to reproduce defect properties including the selfinterstitial atoms formation energies, vacancy formation energy, divacancy binding energy, as well as the bulk properties and the thermal dynamic properties.展开更多
In this paper, by using the level spectroscopy method and bosonization theory, we discuss the evolution of the bond-order-wave （BOW） phase in a one-dimensional half-filled extended Hubbard model wlth the on-site Cou...In this paper, by using the level spectroscopy method and bosonization theory, we discuss the evolution of the bond-order-wave （BOW） phase in a one-dimensional half-filled extended Hubbard model wlth the on-site Coulomb repulsion U as well as the inter-site Coulomb repulsion V and antiferromagnetic exchange J. After clarifying the generic phase diagrams in three limiting cases with one of the parameters being fixed at zero individually, we find that the BOW phase in the U-V phase diagram is initially enlarged as J increases from zero but is eventually suppressed as J increases further in the strong-coupling regime. A three-dimensional phase diagram is suggested where the BOW phase exists in an extended region separated from the spin-density-wave and charge-density-wave phases.展开更多
The results from the molecular dynamics simulations on crystalline, superionic, molten and quenched-amorphous states of calcium fluoride system are reported. The Ca++ and F- sublattices are studied by using the method...The results from the molecular dynamics simulations on crystalline, superionic, molten and quenched-amorphous states of calcium fluoride system are reported. The Ca++ and F- sublattices are studied by using the method of bond order parameters. The result shows that both Ca++ and F- sublattices can be described with the bond-orientation normal distribution model. In the superionic phase the Ca++ cations keep their original stable fcc frame, but in the F- case random distortion generates from their original simple cubic (sc) structure. The simulation on the molten phase gives three radial distribution functions that are difficult to separate from the experimental X-ray diffraction data. The simulation of quenched-amorphous state shows that a dense random packing of equivalent spheres centered by Ca++ cations occurs in the system simulated. However, the system quenched is not stable enough because the Ca++ cation and F- anions around it do not form themselves into a certain configuration.展开更多
By using the density matrix renormalization group technique, the phase diagram of the half-tilting extended Hubbard model is investigated. The conventional order parameter, the two-site entanglement entropy, and the b...By using the density matrix renormalization group technique, the phase diagram of the half-tilting extended Hubbard model is investigated. The conventional order parameter, the two-site entanglement entropy, and the block- block entanglement entropy are analyzed in detail. According to the numerical results, in the weak coupling region, an intermediate bond-order-wave （BOW） phase is shown to exist indeed between the charge-density-wave （CDW） and the spin-density-wave （SDW） phases. The critical phase transition points are determined by the singularity of the first order derivative of two-site entanglement entropy. In strong coupling region, a direct phase transition occurs from SDW phase to CDW phase, and shows discontinuous （first order） character accompanied with energy level crossing. The numerical results support the phase diagram proposed previously by some authors Sengupta et al., （2002）; Sandvik et al., （2004）; Zhang, （2004）. Therefore, the quantum entanglement is a sensitive tool to describe quantum phase transitions in strongly correlated electron systems.展开更多
Uranyl （VI） amidoxime complexes are investigated using relativistic density functional theory. The equilibrium structures, bond orders, and Mulliken populations of the complexes have been systematically investigated...Uranyl （VI） amidoxime complexes are investigated using relativistic density functional theory. The equilibrium structures, bond orders, and Mulliken populations of the complexes have been systematically investigated under a generalized gradient approximation （GGA）. Comparison of （acet） uranyl amidoxime complexes （[UO2（AO）n]2-n, 1≤ n≤4） with available experimental data shows an excellent agreement. In addition, the U-O（1）, U-O（3）, C（1）-N（2）, and C（3） N（4） bond lengths of [UO2（CH3AO）4]2- are longer than experimental data by about 0.088, 0.05, 0.1, and 0.056 A. The angles of N（3） O（3）-U, O（2）-N（1）-C（1）, N（3）-C（3）-N（4）, N（4）-C（3） C（4）, and C（4）-C（3）-N（3） are different from each other, which is due to existing interaction between oxygen in uranyl and hydrogen in amino group. This interaction is found to be intra-molecular hydrogen bond. Studies on the bond orders, Mulliken charges, and Mulliken populations demonstrate that uranyl oxo group functions as hydrogen-bond acceptors and H atoms in ligands act as hydrogen-bond donors forming hydrogen bonds within the complex.展开更多
基金Project supported by the Doctoral Program of Higher Education of China(Grant No.20111415120002)the National Natural Science Foundation of China(Grant Nos.11204199,61178067,and 51135007)+1 种基金the Program for the Outstanding Innovative Teams of Higher Learning Institutions of Shanxi Province,Chinathe Youth Foundation of Taiyuan University of Science and Technology,China(Grant No.20113020)
文摘Atomistic potentials for cupric element and cupric oxide are derived based on the analytical bond-order scheme that was presented by Brenner [Brenner D W, Erratum： Empirical potential for hydrocarbons for use in simulating the chemical vapor deposition of diamond films, Phys. Rev. B 1992, 46 1948]. In this paper, for the pure cupric element, the energy and structural parameters for several bulk phases as well as dimmer structure are well reproduced. The reference data are taken from our density functional theory calculations and the available experiments. The model potential also provides a good description of the bulk properties of various solid structures of cupric oxide compound structures, including cohesive energies, lattice parameters, and elastic constants.
基金supported by the National Natural Science Foundation of China (Grant No. 50971011)the Beijing Natural Science Foundation (Grant No. 1102025)the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20091102110038)
文摘The point defects and their related physical properties in L10 FePt are investigated by molecular dynamics simulations based on an analytic bond-order potential. The calculated results agree well with the experimental value, indicating that the analytic bond-order potential is suitable to describe the structural properties and surface energies of the FePt alloy in the L10 phase. However, the calculated vacancy formation energy of an Fe atom is higher than that of a Pt atom, which disagrees with some other previously calculated results. This result indicates that the analytic bond-order potential is unable to describe the related point defect properties. The analytic bond-order potential needs to be modified in order to study these defect properties of an FePt alloy.
文摘The lattice parameters, elastic constants, cohesive energy, structural energy differences, as well as the properties of point defects and planar defects of hexagonal closepacked yttrium （hcpY） have been studied with ab initio density functional theory for constructing an ex tensive database. Based on an analytical bondorder poial scheme, empirical manybody interatomic potential for hcpY has been developed. The model is fitted to some properties of Y, e.g., the lattice parameters, elastic constants, bulk modulus, cohesive energy, vacancy formation energy, and the structural energy differences. The present potential has ability to reproduce defect properties including the selfinterstitial atoms formation energies, vacancy formation energy, divacancy binding energy, as well as the bulk properties and the thermal dynamic properties.
基金The project supported in part by National Natural Science Foundation of China and the Natural Science Foundation of Zhejiang Province of China. We acknowledge useful discussions with X. Feng, T. Xiang, and Y. Yu.
文摘In this paper, by using the level spectroscopy method and bosonization theory, we discuss the evolution of the bond-order-wave （BOW） phase in a one-dimensional half-filled extended Hubbard model wlth the on-site Coulomb repulsion U as well as the inter-site Coulomb repulsion V and antiferromagnetic exchange J. After clarifying the generic phase diagrams in three limiting cases with one of the parameters being fixed at zero individually, we find that the BOW phase in the U-V phase diagram is initially enlarged as J increases from zero but is eventually suppressed as J increases further in the strong-coupling regime. A three-dimensional phase diagram is suggested where the BOW phase exists in an extended region separated from the spin-density-wave and charge-density-wave phases.
基金Project supported by the National Natural Science Foundation of China.
文摘The results from the molecular dynamics simulations on crystalline, superionic, molten and quenched-amorphous states of calcium fluoride system are reported. The Ca++ and F- sublattices are studied by using the method of bond order parameters. The result shows that both Ca++ and F- sublattices can be described with the bond-orientation normal distribution model. In the superionic phase the Ca++ cations keep their original stable fcc frame, but in the F- case random distortion generates from their original simple cubic (sc) structure. The simulation on the molten phase gives three radial distribution functions that are difficult to separate from the experimental X-ray diffraction data. The simulation of quenched-amorphous state shows that a dense random packing of equivalent spheres centered by Ca++ cations occurs in the system simulated. However, the system quenched is not stable enough because the Ca++ cation and F- anions around it do not form themselves into a certain configuration.
基金Supported by the National Natural Science Foundation of China under Grant No.11047160the National Basic Research Program of China under Grant No.2009CB939901the Foundation of Tianjin Polytechnic University under Grant No.029289
文摘By using the density matrix renormalization group technique, the phase diagram of the half-tilting extended Hubbard model is investigated. The conventional order parameter, the two-site entanglement entropy, and the block- block entanglement entropy are analyzed in detail. According to the numerical results, in the weak coupling region, an intermediate bond-order-wave （BOW） phase is shown to exist indeed between the charge-density-wave （CDW） and the spin-density-wave （SDW） phases. The critical phase transition points are determined by the singularity of the first order derivative of two-site entanglement entropy. In strong coupling region, a direct phase transition occurs from SDW phase to CDW phase, and shows discontinuous （first order） character accompanied with energy level crossing. The numerical results support the phase diagram proposed previously by some authors Sengupta et al., （2002）; Sandvik et al., （2004）; Zhang, （2004）. Therefore, the quantum entanglement is a sensitive tool to describe quantum phase transitions in strongly correlated electron systems.
基金Project supported by the Science and Technology Development Foundation of China Academy of Engineering Physics （Grant No. 2011A0301003）.
文摘Uranyl （VI） amidoxime complexes are investigated using relativistic density functional theory. The equilibrium structures, bond orders, and Mulliken populations of the complexes have been systematically investigated under a generalized gradient approximation （GGA）. Comparison of （acet） uranyl amidoxime complexes （[UO2（AO）n]2-n, 1≤ n≤4） with available experimental data shows an excellent agreement. In addition, the U-O（1）, U-O（3）, C（1）-N（2）, and C（3） N（4） bond lengths of [UO2（CH3AO）4]2- are longer than experimental data by about 0.088, 0.05, 0.1, and 0.056 A. The angles of N（3） O（3）-U, O（2）-N（1）-C（1）, N（3）-C（3）-N（4）, N（4）-C（3） C（4）, and C（4）-C（3）-N（3） are different from each other, which is due to existing interaction between oxygen in uranyl and hydrogen in amino group. This interaction is found to be intra-molecular hydrogen bond. Studies on the bond orders, Mulliken charges, and Mulliken populations demonstrate that uranyl oxo group functions as hydrogen-bond acceptors and H atoms in ligands act as hydrogen-bond donors forming hydrogen bonds within the complex.
