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Chinese Physics B 2011年第9期20卷 295-301页

作者：夏雄平蔡泽彬易林 Department of Physics Huazhong University of Science and Technology Department of Basis Air Force Radar Academy

Effects of electron temperature on dielectric function and localization of laser beams in underdense collisional plasmas are investigated. Simulation results show that the electron temperature has a strong effect on the dielectric constant and the laser beam localization. It is observed that due to the influence of the electron temperature, the dielectric function presents some interesting and complicated nonlinear variations, and gives rise to the laser beam lo- calization. Moreover, the amplitudes of the beam width and the beam intensity are subjected to continuously oscillatory variation in the region of localization. In addition, the effects of several parameters on the dielectric function and the beam localization are discussed.

关键词： underdense collisional plasmas electron temperature dielectric function laser beamlocalization

Calculation of dielectric function of a Quark-Gluon Plasma

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Communications in Theoretical Physics 2008年第6期49卷 1567-1572页

作者： JIANG Bing-Feng LI Jia-Rong Institute of Purticles Physics Centrul Chinu Normul University Wuhun 430079 China Department of Physics Hubei Institute for Nutionulities Enshi 445000 China

With the hard thermal loop （HTL） resummation technique, we calculate the dielectric function excited by hard gluon in quark-gluon plasma （QCP）. We find that in a section of the space-like region po/p ∈ [0.78, 0.95], there are two extremum structures on the dielectric function curve, while the dielectric function in the HTL approximation decreases monotonously without these properties. Through the analyses of the imaginary part of the dielectric function, we conclude that the character of the dielectric function in this region reflects effects of the Landau damping.

关键词： quark-gluon plasma dielectric function hard thermal loop effective perturbation theory

GGA + U Study of the Optical Properties of α-BeH2

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Open Journal of Applied Sciences 2024年第6期14卷 1507-1511页

作者： Uko Ofe Department of Pure and Applied Physics Veritas University Abuja Nigeria

The optical properties of α-BeH2 in an Orthorhombic crystal structure with the space group (Ibam) are investigated. We have calculated the optical properties including dielelectric function, refractive index and extinction coefficient, using density functional approach. A theoretical explanation of the relationship between the dielectric function and other optical constants has been provided. Furthermore, the real and imaginary components of the dielectric function have been examined. The effects of the exchange-correlation potentials (GGA and GGA + U) applied on this compound’s absorption peaks and edges have also been investigated. It was found that using the GGA + U approximation caused the conduction band to shift, which in turn caused the initial absorption peak to shift.

关键词： dielectric function Optical Properties GGA and GGA + U Approximations

Calculations of Energy-Loss function for 26 Materials

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Chinese Journal of Chemical Physics 2016年第6期29卷 663-670,I0001页

作者： Yang Sun Huan Xu Bo Da Shi-feng Mao Ze-jun Ding HefeiNationalLaboratoryforPhysicalSciencesattheMicroscaleandDepartmentofPhysics UniversityofScienceandTechnologyofChinaHefei230025China

We present a fitting calculation of energy-loss function for 26 bulk materials, including 18 pure elements （Ag, A1, Au, C, Co, Cs, Cu, Er, Fe, Ge, Mg, Mo, Nb, Ni, Pd, Pt, Si, Te） and 8 compounds （AgCl, Al2O3, AlAs, CdS, SiO2, ZnS, ZnSe, ZnTe） for application to surface electron spectroscopy analysis. The experimental energy-loss function, which is derived from measured optical data, is fitted into a finite sum of formula based on the Drude-Lindhard dielectric model. By checking the oscillator strength-sum and perfect- screening-sum rules, we have validated the high accuracy of the fitting results. Further-more, based on the fitted parameters, the simulated reflection electron energy-loss spec- troscopy （REELS） spectrum shows a good agreement with experiment. The calculated fitting parameters of energy loss function are stored in an open and online database at http：//***/ELF/***.

关键词： Energy loss function dielectric function Optical data

A study on strain affecting electronic structures and optical properties of wurtzite Mg_(0.25) Zn_(0.75) O by first-principles

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Chinese Physics B 2009年第2期18卷 726-733页

作者：史力斌李明标任骏原王立锦徐翠艳 Department of Physics Bohai University School of Material Science and Engineering University of Science and Technology Beijing Department of Mathematics and Physics Liaoning University of Technology

We have made a first principles study to investigate density of states, band structure, the dielectric function and absorption spectra of wurtzite Mg0.25Zn0.75O. The calculation is carried out in a-axis and c-axis strain changing in the range from 0.3 to -0.2 in intervals of 0.1. The results calculated from density of states show that the bottom of conduction band is always dominated by Zn 4s and the top of valence band is always dominated by O 2p in a-axis and c-axis strain. Zn 4s will shift to higher energy range when a-axis strain changes in the range from 0.3 to 0, and then shift to lower energy range when a-axis strain changes in the range from 0 to -0.2. But Zn 4s will always shift to higher energy range when c-axis strain changes in the range from 0.3 to -0.2. The variations of band gap calculated from band structure and absorption spectra are also investigated, which are consistent with the results obtained from density of states. In addition, we analyse and discuss the imaginary part of the dielectric function ε2.

关键词： first principles density of states band structure dielectric function

Design of an efficient collector for the HIAF electron cooling system

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Nuclear Science and Techniques 2021年第10期32卷 39-49页

作者： Mei-Tang Tang Li-Jun Mao Hai-Jiao Lu Li-Xia Zhao Jie Li Xiao-Ping Sha Fu Ma Yun-Bin Zhou Kai-Min Yan Xiao-Ming Ma Xiao-Dong Yang Jian-Cheng Yang Institute of Modern Physics Chinese Academy of ScienceLanzhou 730000China University of Chinese Academy of Sciences Beijing 100049China

A collector with high perveance,efficient recu-peration,and low secondary emissions is required for the 450-keV electron cooler in the HIAF accelerator *** optimize the collection efficiency of the collector,a simulation program,based on the Monte Carlo simulations,was developed in the world’s first attempt to calculate the electron collection *** this program,the backscattering electrons and secondary electrons generated on the collector surface are calculated using a Monte Carlo approach,and all electron trajectories in the collector region are tracked by the Runge–Kutta *** this paper,the features and structure of our program are *** backscattering electron yields,with various collector surface materials,are calculated using our ***,the collector efficiencies for various col-lector structures and electromagnetic fields are simulated and *** measurement results of the collection efficiency of the HIAF collector prototype and the CSRm synchrotron are also *** experimental results were in good agreement with the simulation results of our program.

关键词： Electron cooler Secondary electron Backscattering electron Monte Carlo method dielectric function

Density-functional Theory Investigation of Sr2CrOsO6 with Cubic Symmetry Using Modified Becke-Johnson Potential

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Chinese Physics Letters 2014年第1期31卷 144-147页

作者：郭三栋 Department of Physics School of Sciences China University of Mining and Technology Xuzhou 221116

We investigate the electronic structures and optical dielectric functions of the high temperature phase of Sr2 CrOs06 with cubic structure by using Tran and Blaha＇s modified Becke and Johnson exchange potential. In the absence of spin-orbit coupling, the total spin moment is OμB. When spin-orbit coupling is included, the small total spin moment and an unquenched Os orbital moment appear, and the spin non-conservation gap becomes smaller. The calculated net magnetic moment is smaller than the popular generalized gradient approximation result, and the spin non-conservation gap is larger. The optical dielectric functions with spin-orbit coupling are not very different from the ones without spin-orbit coupling.

关键词： SPIN-orbit coupling RESEARCH ELECTRONIC structure dielectric function NONRELATIVISTIC quantum mechanics SPIN-orbit interactions (Physics)

Optical Constants of SiO2 Films Deposited on Si Substrates

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Chinese Physics Letters 2014年第4期31卷 114-117页

作者： JI Yi-Qin JIANG Yu-Gang LIU Hua-Song WANG Li-Shuan LIU Dan-Dan JIANG Cheng-Hui FAN Rong-Wei CHEN De-Ying Ti_anjin Key Laboratory of Optical Thin Film Tianjin Jinhang Instittzte of Technical Physics Tianjin 300192 National Key Laboratory of Science and Technology on Tunable Laser Institute of Optical-Electronics Harbin Institute of Technology Harbin 150080

SiO2 films were deposited on single-crystalline silicon substrates by ion beam sputtering technology. Optical constants of SiO2 films are calculated from spectroscopic ellipsometry data, transmittance spectra and reflectance spectra by WVASE32 software, and the best fitted method is oStained for calculating optical constants of dielectric materials in the ultraviolet-visible-infrared （UV-VIS-IR） range. In the UV-VIS-NIR spectral range, refractive indices of SiO2 films are calculated separately by both ellipsometry data and reflectance spectra, and the obtained results are almost the same. Complex dielectric functions of SiO2films in the IR spectral range are accurately calculated with infrared transmission spectra using the GenOsc model. The obtained accuracy complex refractive index of SiO2 films in the wavelength region from 0.19μm to 25 #m is of great importance for the design of high quality coatings, such as ultra-low loss coating.

关键词： SILICA films ULTRAVIOLET-visible spectroscopy ELLIPSOMETRY dielectric function TRANSMITTANCE (Physics) REFLECTANCE

Determination of the In-Plane Optical Conductivity of Multilayer Graphene Supported on a Transparent Substrate of Finite Thickness from Normal-Incidence Transmission Spectra

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Chinese Physics Letters 2014年第5期31卷 174-178页

作者：谌雅琴 Key Laboratory of Microelectronics Devices and Integrated Technology Institute of Microelectronics Chinese Academy of Sciences Beijing 100029

Normal-incidence transmission measurements are commonly used for determining the real part of the in-plane optical conductivities σ1 （ω） of graphene layers. We present an accurate expression for σ1 （ω） in a closed form for a multilayer graphene film supported on a finite-thickness transparent substrate. This form takes into account the coherent and incoherent multiple reflections of the system, whereas the traditional method assumes a semi-infinite substrate. The simulated results for graphene sheets with a layer number N ≤ 10 show that no matter what the transparent substrate is, the accuracy to which σ1 （ω） is determined by applying this expression is improved with no systematic error. Moreover, the layer number N can be exactly determined by simply dividing the σ1 （ω） value of N-layer graphene by the corresponding σ1 （ω） of monolayer graphene, where ωp is the peak frequency of the ordinary dielectric function＇s imaginary part ε1 （ω）of graphene.

关键词： GRAPHENE -- Optical properties RESEARCH OPTICAL conductivity dielectric function SIGNAL-to-noise ratio OPTICAL spectroscopy

AC-electronic and dielectric properties of semiconducting phthalocyanine compounds: a comparative study

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Journal of Semiconductors 2013年第11期34卷 1-6页

作者： Safa’a M.Hraibat Rushdi M-L.Kitaneh Mohammad M.Abu- Samreh Abdelkarim M.Saleh Al-Quds University Physics Dept.Abu DeesJerusalem P.O.Box 20002 Palestine via Israel

The AC-electronic and dielectric properties of different phthalocyanine films （ZnPc, CuPc, FePc, and H2Pc） were investigated over a wide range of temperature. Both real and imaginary parts of the dielectric constant （ε = ε1 - ε2） were found to be influenced by temperature and frequency. Qualitatively the behavior was the same for those compounds; however, the central atom, film thickness, and the electrode type play an important role in the variation of their values. The relaxation time, r, was strongly frequency-dependent at all temperatures and low frequencies, while a weak dependency is observed at higher frequencies. The relaxation activation energy was derived from the slopes of the fitted lines of In r and the reciprocal of the temperature （l/T）. The values of the activation energy were accounted for the hopping process at low temperatures, while a thermally activated conduction process was dominant at higher temperatures. The maximum barrier height, Wm, was found to be temperature and frequency dependent for all phthalocyanine compounds. The value Wm depends greatly on the nature of the central atom and electrode material type. The correlated barrier hopping model was found to be the appropriate mechanism to describe the charge carrier＇s transport in phthalocyanine films.

关键词： dielectric function organic semiconductor phthalocyanine relaxation time