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Density-functional formula for strongly correlated systems

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Progress in Natural Science:Materials International 2005年第5期15卷 395-401页

作者： WANG Huaiyu1.*, HAN Rushan2 and CHEN Nanxian1.1. department of {1., Tsinghua University, Beijing 1.0084, China 2. department of {1., Peking University, Beijing 1.0871. China) department of {1. Tsinghua University Beijing 100084 China department of {1. Peking University Beijing 100871 China

Density functional method is applied for strongly correlated systems. Based on the assumption that the systems are composed of electrons in singly-occupied orbitals and those in doubly-occupied orbitals, a set of self-consistent equations are obtained by standard variation procedure. The equations consist of two parts. One part is to solve the wave functions of the electrons in singly-occupied orbitals and the other is to solve the wave functions of the electrons in doubly-occupied orbitals. The physical meanings of the terms appearing in the equations are discussed.

关键词： density-functional theory strongly correlated systems doubly-occupied orbital two-particle wave function self-consistent equations.

Effects of Ca substitution and surface treatment on electrochemical performances of Ml_(1.0-x) Ca_xNi_(4.0) Co_(0.6) Al_(0.4) hydrogen storage alloy electrodes

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中国有色金属学会会刊：英文版 1999年第3期9卷 487-492页

作者： Chen Weixiang(陈卫祥) 1. Qi Jianqin(祁建琴) 1. Chen Changpin(陈长聘) 2 1. department of {1. 2. department of Materials Science and Engineering, Zhejiang University, Hangzhou 31.027, P. R. China Zhejiang Univ Dept Phys Hangzhou 310027 Peoples R China Zhejiang Univ Dept Mat Sci & Engn Hangzhou 310027 Peoples R China

The influences of Ca substitution for Ml and surface treatment on electrochemical performances of Ml 1.0- x Ca x Ni 4.0 Co 0.6 Al 0.4 hydrogen storage alloy electrode were investigated. Ca substitution with x 2 for Ml could improve its discharge capacity, but Ca substitution with x >0.2 could decrease the capacity. It was also found that Ca substitution deteriorates the electrocatalytic activity, high rate dischargeability and cycling durability of the alloy electrode. In order to improve these properties of Ml 1.0- x Ca x Ni 4.0 Co 0.6 Al 0.4 alloy electrode, the alloy was treated in 6 mol/L KOH+0.02 mol/L KBH 4 solution. The results showed that the surface treatment improves the electrochemical performances such as the electrocatalytic activity, high rate dischargeability and cycling durability of the alloy electrode. :The influences of Ca substitution for Ml and surface treatment on electrochemical performances of Ml 1.0- x Ca x Ni 4.0 Co 0.6 Al 0.4 hydrogen storage alloy electrode were investigated. Ca substitution with x 2 for Ml could improve its discharge capacity, but Ca substitution with x >0.2 could decrease the capacity. It was also found that Ca substitution deteriorates the electrocatalytic activity, high rate dischargeability and cycling durability of the alloy electrode. In order to improve these properties of Ml 1.0- x Ca x Ni 4.0 Co 0.6 Al 0.4 alloy electrode, the alloy was treated in 6 mol/L KOH+0.02 mol/L KBH 4 solution. The results showed that the surface treatment improves the electrochemical performances such as the electrocatalytic activity, high rate dischargeability and cycling durability of the alloy electrode.

关键词： hydrogen storage alloy electrode Ca substitution surface modification

Stochastic resonance in surface catalytic oxidation of carbon monoxide induced by colored noise

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Science China Chemistry 2004年第2期47卷 106-112页

作者： GONG Yubing1.2, HOU Zhonghuai1.& XIN Houwen1.1. department of Chemical {1., University of Science and Technology of China, Hefei 230026, China 2. department of {1., Yantai Teachers University, Yantai 264025, China 1. department of Chemical {1. University of Science and Technology of China 230026 Hefei China 2. department of {1. Yantai Teachers University 264025 Yantai China

The dynamical behavior of surface catalytic oxidation reaction of Pt(1.0)/CO+O2 modulated by colored noise, under the condition of specific temperature, has been investigated when the partial pressure of CO gas is near the supercritical Hopf bifurcation point. By computer simulation the oscillation and stochastic resonance induced by colored noise are observed. The influences of the intensity and correlation time of colored noise on stochastic resonance are discussed. The range of sensitivity of the system to the environmental fluctuation is analyzed.

关键词： colored noise, stochastic resonance, surface catalytic reaction of Pt(1.0)/CO+O2, supercritical Hopf bifurcation, signal-to-noise ratio (SNR).

Internal noise stochastic resonance in CO oxidation on nm-sized palladium particles

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Science China Chemistry 2005年第5期48卷 395-401页

Based on a stochastic mesoscopic model, the influence of internal noise on the oscillatory kinetics of the catalytic oxidation of CO on nm-sized palladium particles is studied, using the chemical Langevin equations, Poisson approximation algorithm, and exact stochastic simulation algorithm. The reaction rate oscillations are of stochastic nature due to considerable internal noise in such mesoscopic systems. It is found that the performance of the stochastic oscillations undergoes a maximum with the variation of internal noise level for a given CO partial pressure, which demonstrates the occurrence of internal noise stochastic resonance. This phe-nomenon implies that optimal internal noise would favor the reaction rate oscillation of CO oxi-dation on nm particles. Such a phenomenon is robust to the change of external parameters, such as CO pressures.

关键词： nanometer-sized palladium particles, surface catalytic CO oxidation, internal noise, stochastic resonance, chemical Langevin equation.

Mathematical stencil and its application in finite difference approximation to the Poisson equation

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Science China Mathematics 2005年第10期48卷 1421-1429页

作者： FENG Hui~1.ZHANG Baolin~(1.2) & LIU Yang~1.1. department of Mathematics,Wuhan University,Wuhan 430072,China 2. Laboratory of Computational {1.,Institute of Applied {1. and Computational Mathematics,Beijing 1.0088. China 1. department of Mathematics Wuhan University 430072 Wuhan China 2. Laboratory of Computational physics Institute of Applied Physics and Computational Mathematics 100088 Beijing China

The concept of mathematical stencil and the strategy of stencil elimination for solving the finite difference equation is presented, and then a new type of the iteration algorithm is established for the Poisson equation. The new algorithm has not only the obvious property of parallelism, but also faster convergence rate than that of the classical Jacobi iteration. Numerical experiments show that the time for the new algorithm is less than that of Jacobi and Gauss-Seidel methods to obtain the same precision, and the computational velocity increases obviously when the new iterative method, instead of Jacobi method, is applied to polish operation in multi-grid method, furthermore, the polynomial acceleration method is still applicable to the new iterative method.

关键词： mathematical stencil, stencil elimination, Poisson equation, finite difference, iterative algorithm,parallelism.

Anisotropic effect on the vibronic reduction factors

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Chinese Science Bulletin 2006年第21期51卷 2553-2558页

作者： QIU Qing-chun1.2 & QIAO Fen1.2 1. department of {1. and IT, Medical College, Shantou University,Shantou 51.041. China 2. department of {1., Shantou University, Shantou 51.063, China department of {1. and IT Medical College Shantou University Shantou 515041 China department of {1. Shantou University Shantou 515063 China

The reduction factors p and q defined by Ham in the Ee JT system and their relation 2q-p=1.have been well accepted and the concept of reduction factors is widely used in the studies of vibronic coupling. However, when the system is under the anisotropic conditions, the reduction factors and their relation will change accordingly. The first-order reduction factors p and q of Ee system were further studied using the method of unitary transformation here. The relation between p and q proposed by Ham was investigated under both conditions of the linear coupling and the anisotropic effects. The result demonstrated that the relation of 2q-p=1.was only correct for the linear vibronic coupling, but not correct when the anisotropic effect was considered. This result suggested that the anisotropic effect influence considerably the reduction factors, and hence the physical properties of materials. Our method could be also applied to other JT systems, especially the highly symmetric JT systems involving C60 molecules.

关键词：电子振动耦合声子交迭 Jahn-Teller效应各向异性

Probing proton halo of the exotic nucleus ^(28)S by elastic electron scattering

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Science China(physics,Mechanics & Astronomy) 2004年第1期47卷 42-51页

作者： WANG Zaijun1.& REN Zhongzhou1.2 1. department of {1., Nanjing University, Nanjing 21.008, China 2. center of Theoretical Nuclear {1., National Laboratory of Heavy-Ion Accelerator at Lanzhou, Lanzhou 730000, China Correspondence should be addressed to Ren Zhongzhou (email: zren@*** zren99@***) Received June 1., 2003 1. department of {1. Nanjing University 210008 Nanjing China 2. center of Theoretical Nuclear {1. National Laboratory of Heavy-Ion Accelerator at Lanzhou 730000 Lanzhou China

Elastic electron scattering on the exotic light nucleus 28S is investigated in the plane wave Born approximation. The variation of the squared form factors of 28S with momentum transfer is compared with that of 32S. It is found that the behavior of the form factors near the second minimum (with a moderate momentum transfer) is sensitive to the alteration of the charge density distribution of halo protons in 28S. This indicates that elastic electron scattering can be a good probe of the structure of proton-halo nuclei.

关键词： elastic electron scattering, cross section, form factor, proton-halo nucleus.

Direct CP violation in hadronic B decays

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Science China(physics,Mechanics & Astronomy) 2006年第3期49卷 357-366页

作者： HONG Bihai1.2 & Lü Caidian3 1. department of {1., Lishui University, Lishui 323000,China 2. department of {1., Shanghai Jiaotong University, Shanghai 200030, China 3. Institute of High Energy {1., Beijing 1.0049,China department of {1. Lishui University Lishui 323000 China department of {1. Shanghai Jiaotong University Shanghai 200030 China Institute of High Energy physics Beijing 100049 China

There are different approaches for the hadronic B decay calculations, recently. In this paper, we upgrade three of them, namely factorization, QCD factorization and the perturbative QCD approach based on kT factorization, using new parameters and full wave functions. Although they get similar results for many of the branching ratios, the direct CP asymmetries predicted by them are different, which can be tested by recent experimental measurements of B factories.

关键词： CP violation hadronic B decay factorization.

The influence of laser pulse on the photoabsorption spectra of Li atom in strong external field

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Science China(physics,Mechanics & Astronomy) 2006年第2期49卷 178-186页

作者： WANG Dehua1.& LIN Shenglu2 1. School of physics and Electronic Engineering, Yantai Normal University, Yantai 264025, China 2. {1. of physics, Shandong Normal University, Jinan 25001., China 1. School of physics and Electronic Engineering Yantai Normal University Yantai 264025 China 2. department of {1. Shandong Normal University Jinan 250014 China

Using the time-dependent perturbation theory and the calculation formula of the single- and double-pulse absorption spectra of the atom in strong external fields, we calculate the single- and double-pulse absorption spectra of Li atom in strong magnetic field for different pulse widths. The results show that a pulse of some width can reduce the contribution of the short period closed orbits and eliminate the contribution of the long period orbits. Compared with the single-pulse absorption spectra, we found that for some phase differences, the double-pulse laser absorption spectra are strengthened; while for others, they are reduced. Therefore, we can use the pulse laser to control the oscillation of the absorption spectra and obtain the optimization object.

关键词： laser pulse closed orbit absorption spectra.