Macroscopic theory of the electron work function in solids

The approach is based on the dielectric formalism theory. The relations for calculation of the electron work function in solids – metals, semiconductors and dielectrics, were obtained. The calculated results are in an agreement with experimental ones. This approach can be used for computation of work function values of numerous materials.     

Non-local corrections to the electronic structure of metal surfaces

A non-local exchange-correlation term, derived from the static dielectric function of Vashishta and Singwi (VS), is introduced into the density functional for an interacting electron gas. The coefficient is chosen to give the same surface energy for two adjacent jellium metals of nearly equal density as is obtained from the VS dielectric function. This density functional is then used to calculate surface energies and work functions for metal-vacuum interfaces. The results for both surface energies and work functions found in this way are significantly higher than the experimental values. Possible explanations for the discrepancies are discussed.     

Analysis of Frequency Selective Surfaces with Metallic and Dielectric Losses at Millimeter Wave Range

In this paper, a theoretical analysis of scattering from a doubly frequency selective surfaces (FSS) with dielectric and metallic losses in the millimeter wave range is presented. The theoretical analysis involves the solution of the electric field integral equation relating the induced current in the FSS in the presence of anisotropic dielectric layers. The method of moment is employed to obtain numerical results. The frequency selective surface structure considered is composed by conducting patch elements sandwiched between two anisotropic dielectric layers. Three different anisotropic materials are considered: Epsilam-10, Alumina, and Sapphire. The sapphire presents low losses when compared with the other two dielectric materials. The most common metals, as copper and aluminum, are considered in this analysis. None significant metallic losses were observed for any considered metal. Numerical results are presented for the scattering characteristics and for dielectric and metallic losses parameters.     

Theoretical Studies on Photoionization Cross Sections of Solid Gold

Accurate expression for photoabsorption (photoionization) cross sections of high density system proposed recently is used to study the photoionization of solid gold. The results show that the present theoretical photoionization cross sections have good agreement both in structure and in magnitude with the experimental results of gold crystal. The studies also indicate that both the real part ε' and the imaginary part ε" of the complex dielectric constant ε, and the dielectric influence function of a nonideal system have rich structures in low energy side with a range about 50 eV, and suggest that the influence of particle interactions of surrounding particles with the photoionized particle on the photoionization cross sections can be easily investigated using the dielectric influence function. The electron overlap effects are suggested to be implemented in the future studies to improve the accuracy of theoretical photoionization cross sections of a solid system.     

Electron work function and electronic affinity of intrinsic semiconductors

By using the simplest dielectric permittivity models, relationships are obtained on the basis of a dielectric formalism, by which the electron work function and electronic affinity of polycrystalline materials—metals, intrinsic semiconductors, and dielectrics—can be estimated. The electron work function and affinity are computed for 25 semiconductors for which there are no experimental data or there are single values.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 67–71, December, 1985.     

Macroscopic theory of adhesion in solids

The relations for calculation interaction energies and forces for solids: metals, semiconductors and dielectrics are obtained on dielectric formalism based theory. The results are compared with available ones and can be used as for theoretical strength forces and energies as for Van der Waals-Casimir forces estimations.     

金属中声学等离激元的产生条件

本文从相互作用布洛赫电子气的介电函数出发,导出了金属中存在确定的声学等离激元的条件,并对A-15化合物是否满足这个条件作了讨论,认为在A-15化合物中声学等离激元的存在尚缺乏足够的证据。 关键词：     

Surface excitation probabilities in surface electron spectroscopies

The phenomenon of surface excitation is competitive in nature for elastic and other inelastic scattering processes in surface electron spectroscopies; the knowledge of influence of surface excitations in electron energy loss spectra is then essential for quantitative surface analysis with these spectroscopies. The inelastic scattering of an electron moving in the vicinity of a surface is considered in a self-energy formalism to estimate the contribution of surface excitation in electron-solid interactions via the total surface excitation probability. The formulation uses the optical bulk dielectric function and provides the spatial and angular dependence of the differential and total inelastic cross-sections. The kinetic energy range of probing electrons considered is 100-5000 eV and the numerical evaluation of total surface excitation probabilities are performed for several metals, Au, Ag, Cu, Ni, Fe and Ti; empirical formulae for the surface excitation probability are given for each of these materials and compared with experimental results for the surface excitation parameter. The total surface excitation probability is higher in Ag as compared to other metals under consideration, for identical conditions of electron-solid interactions.     

Electron work function in alloys with alkali metals

The electron work function in alloys and compounds containing alkali metals, which are of interest for the designing of new photocathode materials and further development of the theory of electron emission, is studied. It is shown that a number of applied and theoretical issues in this field are poorly understood. These are the temperature and concentration dependences of the electron work function in binary metallic systems, the surface activity of components that are inactive in alloys with alkali metals, and some others.     

On the electronic contribution to the surface energy of metals

An expression for the exchange and correlation contributions to the surface energy of metals is derived using the dielectric formulation of the electron gas. The result which is obtained in the infinite barrier model for the surface is exact within the RPA and include the off-diagonal character of the response function.     

Effect of dielectric properties of metals on terahertz transmission subwavelength hole arrays

We study the influence of dielectric function of metals on the transmission properties of terahertz pulses through periodically patterned subwavelength holes. Because of a drastic increase in the value of dielectric constants, most metals become highly conductive at terahertz frequencies. Extraordinary terahertz transmission is observed in subwavelength hole arrays made from both good and poor electrical conductors. The measured transmittance of terahertz pulses is found to be enhanced with increasing ratio of the real to the imaginary dielectric constant of the constituent metals, for which the dielectric function follows the Drude model.     

Thermoelectric Coefficients of Silicon MOSFETS in Quantizing Magnetic Field

The phonon drag and electron diffusion contribution to the tensor M which determines 3 the heat flux U = M·E is calculated for a silicon MOSFETS in a perpendicular magnetic field B. We used nearly the same theoretical formalism as Ref [6], but improvements are made in several respects. First of all the dielectric function of Fermi-Thomas approximation which has been proved to result in overscreening of the interaction is replaced by rigorous Lindhard-type dielectric function to take account of the screening between electrons and phonons. Secondly the contributions of localized electrons are separated from those of the free state electrons which are the only part that contributes to both conductivity tensor and magnetothermopower tensor. The calculated M_yx and S_xx reveal magneto-oscillationsoriginating Gom oscillations in the density of states at the Fermi level. At T = 5.02 K, our new results show that the diffusion components of thermopower are negligibly small compared with those due to phonon drag. All the theoretical values of M_yx, S_xx and S_yx are in accordance with the experimental data better than previous theoretical results.     

Optical characterization of the polymer embedded alloyed bimetallic nanoparticles

A theoretical approach for the calculation of the bimetallic nanoparticles absorption spectra has been developed as an extension of the Mie theory in which nanoparticle dielectric function is found by the weighted linear combination of the dielectric functions for particles made of the corresponding pure metals. In the frame work of the theoretical model an expression for the resonance light absorption frequency were derived taking into account the interband transitions in the dielectric functions. We propose a simple method for the on-line monitoring of the bimetallic nanoparticles composition based on the measurement of the absorption peak position. Elaborated theoretical approach was used to investigate the polymer embedded Ag/Au nanoparticles which were prepared by reducing gold and silver salts (HAuCl4 and AgNO3, respectively) by ethylene glycol in presence of poly(vinyl pyrrolidone) (PVP) at room temperature. Calculated absorption spectra for the Ag/Au nanoscopic systems showed good agreement with the experimental data. Temporal evolution of the Ag/Au nanoparticles has also been investigated by this approach.     

“Instantaneous” spectrum of passively ionized electrons in a dielectric irradiated by a high-power electron beam

A technique is developed for theoretical analysis, and the “instantaneous energy spectrum,” that is, the energy spectrum of passively ionized electrons in a dielectric irradiated by an electron beam of moderate or high density which arises prior to electron-phonon relaxation is calculated. The source of the beam is usually a high-current electron accelerator. The computation algorithm is designed so as to make it possible to fully take into account and make use of the following data: first, the actual (measured) spectrum of the electron beam; second, the complete electron spectrum of the dielectric, including the spectrum of the density of occupied states, which is continuous within the valence bands and discrete in the region of the low-lying quasiatomic levels; and the spectrum of the density of unoccupied states, which begins in the conduction band and, in a continuous process, turns into the spectrum of quasi-free electrons in the crystal; third, the differential ionization cross-sections of the atoms due to electron impact, which the present report refines so as to take in into account the actual spectrum of the density of the final states; the latter spectrum is continuous within the valence bands and discrete in the region in which the law of dispersion of a band electron turns into the law of dispersion of a quasi-free electron. The results of the theoretical analysis are compared with the data of a numerical experiment carried out in the present report by the Monte-Carlo method using the same initial data. The agreement between the theoretical results and the data from the numerical experiment demonstrates the stability and reliability of the algorithm used to calculate the instantaneous spectrum. The precision of the calculation is determined solely by the initial data. The instantaneous spectrum which is obtained is the initial distribution function for all the kinetic equations describing subsequent relaxation of the electrons in the irradiated dielectric. Tomsk Polytechical Institute. Tomsk State University. Institute of High-Current Electronics, Russian Academy of Sciences (Siberian Division). Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 136–144, November, 1996.     

用赝势方法计算简单金属的弹性常数

本文利用单参数Heine-Abarenkov模型势及Hubbard-Sham介电函数计算了七种简单金属(Li,Na,K,Rb,Cs,Al和Pb)的二阶与三阶弹性常数,两个可调参数用零温零压下晶体的弹性常数C₄₄与晶格常数的实验值来确定,计算结果与实验值或其他作者的理论计算值符合得比较好,尤其是Al的三阶弹性常数,本文的计算结果比其他作者的计算结果更接近于实验值。 关键词：     

An FDTD method for the simulation of dispersive metallic structures

In this paper, we present a formulation of the finite-difference time-domain method for the simulation of metallic structures. The frequency dependent dielectric function of metals is approximated by a combined Drude–Lorentzian multi-pole expansion and fitting errors of only a few percent are obtained. An auxiliary differential equation technique is used to extend the standard FDTD algorithm with the dispersive material equations. The algorithm is validated by calculating reflection and transmission coefficients for thin metal layers, elliptical nano-particles and by simulating a surface plasmon resonance device. Excellent agreement between the FDTD simulations and exact theoretical results are obtained.     

高压下稳态六方Ge2Sb2Te5结构、电子和光学性质的第一性原理研究

采用基于密度泛函理论的广义梯度近似方法研究了稳态六方petrov原子序列结构Ge2Sb2Te5的结构、电子和光学性质。计算所得的平衡态晶格参数与实验数据和先前的理论结果吻合很好。基态的能带结构和态密度表明了稳态六方petrov原子序列结构的Ge2Sb2Te5持有金属性。从压强影响下体积的变化趋势发现稳态六方Ge2Sb2Te5在17 GPa和34 GPa 出现不稳定,暗示在此压强下的相变发生,这与2009年Krbal等人的实验结果相吻合。同时,还系统地研究了稳态六方petrov原子序列结构的Ge2Sb2Te5高压下的光学性质,得到了高压下介电函数、吸收率、光反射率、折射率、消光系数和电子能量损失谱在20 eV内的变化情况。     

Optical and spectral tunability of multilayer spherical and cylindrical nanoshells

This theoretical work presents a comparative study of the optical properties and spectral tunability of hybrid multilayer spherical and cylindrical nanoshells based on the quasi-static approximation of classical electrodynamics. The interband transitions have been considered using the Drude–Lorentz model for the complex dielectric function of metallic layers because the optical properties of metals arise from both the optical excitation of interband transitions and the free-electron response. A general formula for N-ayer concentric nanoshells is arranged, and numerical calculations are performed for the four-layer nanoshells as an example. We have analyzed in detail different configurations of nanoshells such as dielectric-metal-dielectric-metal with dielectric core, metal-dielectric-metal-dielectric with metal core and semiconductor-metal-dielectric-metal with semiconductor core because composition of nanoshells have dramatic influence on their optical properties. The absorbance spectrum behavior of the shell thicknesses, surrounding medium, shape and composition of each layer of the nanoshell is numerically investigated.     

Electron mean free path and conduction-band density-of-states in solid methane as determined from low-energy electron transmission experiments

Recently, Plenkiewicz et al. developed a theoretical model for analyzing the current I_t transmitted by a thin dielectric film as a function of incident electron energy E. The purpose of this paper is to apply this model to the analysis of recent I_t(E) results for solid methane. The analysis permits the determination of both the electron mean free path as a function of energy and the electronic conduction-band density-of-states in the quasi-elastic scattering region. The differences between our results and Kunz's solid methane band structure calculations are also discussed.