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Search Results: 1 - 10 of 129581 matches for " Hong-Jian Liu "
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Electronic structures and magnetoelectric properties of tetragonal BaFeO3: an ab initio density functional theory study

Feng Hong-Jian,Liu Fa-Min,

中国物理 B , 2008,
Abstract:
Ab initio prediction on ferrotoroidic and electronic properties of olivine Li4MnFeCoNiP4O16

Feng Hong-Jian,Liu Fa-Min,

中国物理 B , 2009,
Abstract:
Ab initio study on phase transition and magnetism of BiFeO3 under pressure

Feng Hong-Jian,Liu Fa-Min,

中国物理 B , 2009,
Abstract: In this paper the first-principles calculations within local spin density approximation (LSDA)+U show that BiFeO3 experiences a mixed phase state with P4mm structure being the intermediate phase before the pressure of phase transition is reached. The critical pressure for the insulator--metal transition (IMT) is found to be about 50 GPa. A pressure induced crossover of high-spin states and low-spin states is observed close to the IMT pressure in R3c structure. The LSDA+U calculations account well for the mechanism of the IMT and crossover of spin states predicted in recent experiment (Ref.1]).
First-principles prediction of coexistence of magnetism and ferroelectricity in rhombohedral Bi2FeTiO6
Hong-Jian Feng,Fa-Min Liu
Physics , 2007, DOI: 10.1016/j.physleta.2007.10.039
Abstract: First principles calculations based on the density functional theory within the local spin density approximation plus U(LSDA+U)scheme, show rhombohedral Bi$_2$FeTiO$_6$ is a potential multiferroic in which the magnetism and ferroelectricity coexist . A ferromagnetic configuration with magnetic moment of 4 $\mu_B$ per formula unit have been reported with respect to the minimum total energy. Spontaneous polarization of 27.3 $\mu$ C/cm$^2$, caused mainly by the ferroelectric distortions of Ti, was evaluated using the berry phase approach in the modern theory of polarization. The Bi-6s stereochemical activity of long-pair and the `d$^0$-ness' criterion in off-centring of Ti were coexisting in the predicted new system. In view of the oxidation state of Bi$^{3+}$,Fe$^{2+}$,Ti$^{4+}$, and O$^{2-}$ from the orbital-resolved density of states of the Bi-6p, Fe-3d,Ti-3d, and O-2p states,the valence state of Bi$_2$FeTiO$_6$ in the rhombohedral phase was found to be Bi$_2$$^{3+}$Fe$^{2+}$Ti$^{4+}$O$_6$.
Ab initio prediction on ferrotoroidic olivine Li4MnFeCoNiP4O16
Hong-Jian Feng,Fa-Min Liu
Physics , 2007,
Abstract: First-principles calculation predict that olivine Li4MnFeCoNiP4O16 has ferrotoroidic characteristic and ferrimagnetic configuration with magnetic moment of 1.56 \muB per formula unit. The ferrotoroidicity of this material makes it a potential candidate for magnetoelectric materials . Based on the orbital-resolved density of states for the transtion-metal ions in Li4MnFeCoNiP4O16, the spin configuration for Mn2+,Fe3+,Co2+, and Ni2+ is t2g3eg2, t2g3eg2,t2g1t2g3eg1eg2, and t2g2t2g3eg1eg2, respectively. Density functional theory plus U (DFT+U) shows a indirect band gap of 1.25 eV in this predicted material, which is not simply related to the electronic conductivity in terms of being used as cathode material in rechargeable Li-ion batteries.
Electronic structure of BaFeO3: an abinitio DFT study
Hong-Jian Feng,Fa-Min Liu
Physics , 2007,
Abstract: First principles calculations were performed to study the ground state electronic properties of BaFeO3 (BFO) within the density functional theory (DFT). Adopting generalized gradient approximation (GGA) exchange and correlation functional and Vosko-Wilk-Nusair correlation energy functional interpolation, we have systematically conducted the band structure, density of states and electronic distribution along different crystalline planes. Calculating results show that band gap in the majority spin band structure and band gap in the minority spin band structure were found to be 2.7012 eV and 0.6867 eV respectively. Up-spin Fe t2g were fully occupied and down-spin Fe eg were empty. Moreover, the up-spin Fe eg and down-spin Fe t2g were partially occupied near the Fermi energy, leading to a finite density of states. The Fe4+-O-Fe4+ plane superexchange coupling should rearrange the magnetic order to make the ferromagnetic characteristic being possible, moreover the tetragonal displacement along the c axis could induce the perovskites materials to acquire ferroelectric property. These reasons could lead to the fact that the tetragonal phase BFO could be a potential multiferroics while it was produced under the very experimental conditions. The charge density along different crystalline planes were illustrated to show that strong covalent bonding between O and Fe can be used to investigate the exchange coupling, and this strong hybridization may further increase the superexchange coupling to enhance the magnetic ordering.
Electronic structure of barium titanate : an abinitio DFT study
Hong-Jian Feng,Fa-Min Liu
Physics , 2007,
Abstract: First principle calculations were performed to study the ground state electronic properties of Barium titanate within the density functional theory (DFT). In our DFT computations, we used Vosko-Wilk-Nusair correlation energy functional and generalized gradient approximation (GGA) exchange and correlation energy functional as suggested by Perdew and Wang (PWGGA). The band structure, total density of states (DOS) and partial DOS have been systematically conducted to investigate the electronic configuration of this prototype ferroelectric perovskits compound. The band gap was 1.92 eV within our approach, and the quasi-flat band at -17 eV and -10 eV were attributed to the O 2s and Ba 5p states respectively, which was in good agreement with the corresponding total DOS and partial DOS. From the DOS investigation, it can be seen that the Ti eg state intended to interact with the oxygen octahedral orbitals to form the p-d hybridization. Moreover the strong p-d overlap and bonding can be observed in the electronic density redistribution along the different crystalline planes with respect to the corresponding space group, and the electronic isodense have been shown along the (001), (100), (110) and (111) crystal planes. From these electronic density maps, the strong bonding between Ti and O atoms can even be observed in the (111) crystalline plane.
Coupling of Magnetization and Structural Distortions in Multiferroic BiFeO3: an Ab Initio Density Functional Theory Study
Coupling of Magnetization and Structural Distortions in Multiferroic BiFeO3: an Ab Initio Density Functional Theory Study

FENG Hong-Jian,LIU Fa-Min,
冯宏剑
,刘发民

中国物理快报 , 2008,
Abstract: The coupling between magnetism and structural distortions in BiFeO3(BFO) is investigated using density functional theory by considering the spin--orbit effect. Computational results show that the resulting magnetization M isrotated by reversal of sense of rotation of the oxygen octahedra in the double cell. The resulting magnetization is determined by the antiferrodistortive (AFD) distortions and ferroelectric (FE) displacements. This work clarifies the previous view that magnetism is only coupled with, and determined by, FE displacements. The excellent ferroelectricity is attributed significantly to the anomaly of Born effective charge of Bi, which is caused by the stereochemically active long pair of Bi 6s.
Semi-supervised learning based on K-means clustering algorithm
基于半监督学习的K-均值聚类算法研究

LIU Tao,YIN Hong-jian,
刘涛
,尹红健

计算机应用研究 , 2010,
Abstract: This paper constructed a new classified function which mixed Euclidean distance with supervising information. Taking into account that K-means algorithm was sensitive to the initial center, used search space of particle swarm algorithm was used to simulate the clustering Euclidean space to find a better cluster center of clustering. At the same time, brought up a strategy of species dynamic management to improve the efficiency of particle swarm optimization search. The algorithm got a good clustering accuracy on a number of UCI testing data sets.
The Effect of D-( )-arabinose on Tyrosinase: An Integrated Study Using Computational Simulation and Inhibition Kinetics
Hong-Jian Liu,Sunyoung Ji,Yong-Qiang Fan,Li Yan
Enzyme Research , 2012, DOI: 10.1155/2012/731427
Abstract:
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