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Search Results: 1 - 10 of 16972 matches for " Electron Localized Function "
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Bonding Characteristics of TiC and TiN  [PDF]
Kuiying Chen, Sami Kamran
Modeling and Numerical Simulation of Material Science (MNSMS) , 2013, DOI: 10.4236/mnsms.2013.31002
Abstract:

Using ab initio density functional theory calculations, the electron localization function (ELF) of typical transition metal carbide TiC and nitride TiN were computed and analyzed to reveal their nature of the chemical bonds. The ELF approach was initially validated through typical examples of covalent-bonding Diamond (C) and ionic-bonding sodium chloride NaCl. Our results clearly demonstrate the dominantly ionic bonding characteristics of TiC and TiN. It is also suggested that the high mechanical hardness of TiC and TiN can be explained without evoking strong covalence.

Superconducting transition temperature with interband interaction
带间作用与超导转变温度

Cao Tian-De,
曹天德

物理学报 , 2002,
Abstract: The d-p model is studied using Green functions.It is shown that the interband interaction U dp can lead to superconductivity and raising the critical temperature,but the local electron-electron interaction U d decreases the transition temperature.We also argue that the interband interaction could make both the normal states and superconducting states show non-Fermi-liquid behaviours.
Wave Function as Geometric Entity  [PDF]
Bohdan I. Lev
Journal of Modern Physics (JMP) , 2012, DOI: 10.4236/jmp.2012.38096
Abstract: A spacial approach to the geometrization the theory of the electron has been proposed. The particle wave function is represented by a geometric entity, i.e., Clifford number, with the translation rules possessing the structure of Dirac equation for any manifold. A solution of this equation is obtained in terms of geometric treatment. New experiments concerning the geometric nature wave function of electrons are proposed.
Computational Study of Resonantly Ionizing Rubidium Vapor by Nanosecond Laser Pulses  [PDF]
Mohamed Abd El-Hameid Mahmoud, Yosr Ez El Din Gamal
Journal of Modern Physics (JMP) , 2012, DOI: 10.4236/jmp.2012.39121
Abstract: An investigation of the resonant interaction of the rubidium atoms with an intensity (10 kWcm-2 ≤ I ≤ 2 MWcm-2) and a wavelength close to that of the D1 and D2 transitions of the rubidium atom (5S1/2 → 5P3/2 or 5S1/2 → 5P1/2, λD1 = 780 nm, λD2 = 795 nm), which has passes through rubidium vapor with density (1011 - 1014 cm-3) been studied theoretically. The system of equations describing the processes of Collisional ionization and multiphoton ionization of rubidium vapour resonantly excited with nanosecond pulsed laser is solved. The dependence of the ion density on the laser intensity and the atomic density of rubidium are considered. The result of calculations revealed that, both quadratic ion density dependence on laser intensity and linear behaviour of the ion density versus rubidium density for 5S1/2 → 5P3/2 transition is due to photoioization process. In contrast, for 5S1/2 → 5P1/2 transition, the ion density dependence is nonlinear and indicates that the collisional processes play the major contribution in the total ionization. Also, the obtained results showed reasonable agreement with the experimentally measured values of the ion density dependence given by Bakhramov et al. In addition, the analysis of mutual competition between the different ionization processes considered for the ion yield as a function of both laser intensity and atoms density are also presented this work.
The localized electronic states and transmission spectra in N-layer superlattice with structural defects in finite magnetic fields
磁场下含结构缺陷多组分超晶格中的局域电子态和电子输运

Wang Xin-Jun,Wang Ling-Ling,Huang Wei-Qing,Tang Li-Ming,Chen Ke-Qiu,
王新军
,王玲玲,黄维清,唐黎明,陈克求

物理学报 , 2006,
Abstract: Within the framework of effective-mass approximation, the properties of the localized electronic states in a N-layer superlattice (SL) with structural defects in finite magnetic fields are investigated by utilizing the transfer matrix and effective barrier-height methods. When the mismatch of electron effective mass in different constituent layers is considered, an external magnetic field will lead to the magneto-coupling. The numerical results show that the magneto-coupling brings about not only quantization of localized electron levels but also the degree of the strong dependence of the localized levels on Landau indices and magnetic fields, especially for the localized levels in higher energy region. In addition, we demonstrate in detail the correlations between the localized electronic states inside the minigaps of the infinite SL with structural defect layer and the resonant transmission peaks in dips of the finite SL. A good coincidence between the localized states and transmission peaks is found, which provides a theoretical basis for experimental observation of the localized electronic states in SLs.
On the Importance of Clar Structures of Polybenzenoid Hydrocarbons as Revealed by the π-Contribution to the Electron Localization Function
Jun Zhu,Christian Dahlstrand,Joshua R. Smith,Sébastien Villaume,Henrik Ottosson
Symmetry , 2010, DOI: 10.3390/sym2031653
Abstract: The degree of p-electron (de)localization and aromaticity of a series of polybenzenoid hydrocarbons (PBHs) has been analyzed through the π-contribution to the electron localization function (ELFπ), calculated at the B3LYP/6-311G(d,p) hybrid density functional theory level. The extent of p-electron delocalization in the various hexagons of a PBH was determined through analysis of the bifurcation values of the ELFp basins (BV(ELFp)), the spans in the bifurcation values in each hexagon (ΔBV(ELFπ)), and the ring-closure bifurcation values of the ELFπ (RCBV(ELFπ)). These computed results were compared to the qualitative description of local aromaticities of the different hexagons in terms of Clar structures with p-sextets. Benzene, [18]annulene, and thirty two PBHs were analyzed at their equilibrium geometries, and benzene and triphenylene were also analyzed at bond length distorted structures. In general, the description of PBHs in terms of Clar valence structures is supported by the ELFp properties, although there are exceptions. For PBHs at their equilibrium geometries there is a clear sigmoidal relationship between the CC bond lengths and the amount of p-electron (de)localization at these bonds, however, this relationship is lost for bond distorted geometries. In the latter cases, we specifically examined benzene in D3h symmetric “1,3,5-cyclohexatriene” structures and triphenylene in eight different structures. From the distorted benzenes and triphenylenes it becomes clear that there is a distinct tendency for the p-electron network to retain delocalization (aromaticity). The ELFp analysis thus reveals an antidistortive rather than a distortive behavior of the p-electrons in these investigated compounds.
Work Functions of Pd_(83.5)Si_(16.5)and Cu_(70)Ti_(30)Glassy Alloys
By FENG Benzheng YANG Deqing Institute of Precious Metals,Kunming,Yunnan,ChinaPhysics,
冯本政
,杨德清

材料科学技术学报 , 1991,
Abstract: The work functions before and after crystallization of two glassy alloys,Pd_(83.5)Si_(16.5) and Cu_(70)Ti_(30) have been measured by means of the con- tact potential difference method in the secondary electron field at room temperature under 10~(-5) Pa vacuum.The results show that the work functions of both glassy alloys are higher than those of the corresponding crystalline alloys.
Mathematical Modeling for Quantum Electron Wave Therapy  [PDF]
Gianamar Giovannetti-Singh, Sixian Zhao
Journal of Modern Physics (JMP) , 2012, DOI: 10.4236/jmp.2012.33031
Abstract: The hypothesis suggesting that the physical process of quantum tunneling can be used as a form of cancer therapy in electron ionization radiotherapy was suggested in the IEEE International Conference on Electric Information and Control Engineering by G. Giovannetti-Singh (2012) [1]. The hypothesis used quantum wave functions and probability amplitudes to find probabilities of electrons tunneling into a cancer cell. In addition, the paper explained the feasibilities of the therapy, with the use of nanomagnets. In this paper, we calculate accurate probability densities for the electron beams to tunnel into cancer cells. We present our results of mathematical modeling based on the helical electron wave function, which “tunnel” into a cancer cell, therefore ionizing it more effectively than in conventional forms of radiotherapy. We discuss the advantages of the therapy, and we explain how quantum mechanics can be used to create new cancer therapies, in particular our suggested Quantum Electron Wave Therapy.
Numerical Study of the Threshold Intensity Dependence on Wavelength in Laser Spark Ignition of Molecular Hydrogen Combustion  [PDF]
Kholoud A. Hamam, Galila Abdellatif, Yosr E. E.-D. Gamal
Journal of Modern Physics (JMP) , 2013, DOI: 10.4236/jmp.2013.43042
Abstract:

A numerical investigation of laser wavelength dependence on the threshold intensity of spark ignition in molecular hydrogen over a wide pressure range is presented. A modified electron cascade model (Gamal et al., 1993) is applied under the experimental conditions that carried out by Phuoc (2000) to determine the threshold intensity dependence on gas pressure for spark ignition in hydrogen combustion using two laser wavelengths namely; 1064 nm and 532 nm. The model involves the solution of the time dependent Boltzmann equation for the electron energy distribution function (EEDF) and a set of rate equations that describe the change of the formed excited molecules population. The model takes into account most of the physical processes that expected to occur in the interaction region. The results showed good agreement between the calculated thresholds for spark ignition and those measured ones for both wavelengths, where the threshold intensities corresponding to the short wavelength (532 nm) are found to be higher than those calculated for the longer one (1064 nm). This result indicates the depletion of the high density of low energy electrons generated through multi-photon ionization at the short wavelength via electron diffusion and vibrational excitation. The study of the EEDF and its parameters (viz, the temporal evolution of: the electron density, ionization rate electron mean energy, …) revealed the important role played by each physical process to the spark ignition as a function of both laser wavelength and gas pressure. More over the study of the time variation of the EEDF explains the characteristics of the ignited spark at the two wavelengths for the tested pressure values.

Studies of Electron Energy Distribution Function (EEDF) in Lithium Vapor Excitation at 2S→3D Two-Photon Resonance  [PDF]
Mohamed A. Mahmoud, Kholoud A. Hamam
Optics and Photonics Journal (OPJ) , 2014, DOI: 10.4236/opj.2014.48020
Abstract:

We have developed a computational model which quantitatively studies the Electron Energy Distribution Function (EEDF) in laser excited lithium vapor at 2s→3d two-photon resonance. A kinetic model has been constructed which includes essentially all the important collisional ionization, photoionization, electron collisions and radiative interactions that come into play when lithium vapor (density range 1013 - 1014 cm-3) is subject to a sudden pulse of intense laser radiation (power range 105 - 106 W·cm-2) at wavelength 639.1 nm and pulse duration 20 ns. The applied computer simulation model is based on the numerical solution of the time-dependent Boltzman equation and a set of rate equations that describe the rate of change of the formed excited states populations. Using the measured values for the cross-sections and rate coefficients of each physical process considered in the model available in literature, relations are obtained as a function of the electron energy and included in the computational model. We have also studied the time evolution and the laser power dependences of the ion population (atomic and molecular ions) as well as the electron density which are produced during the interaction. The energy spectra of the electrons emerging from the interaction contains a number of peaks corresponding to the low-energy electrons produced by photoionization and collisional ionization such as assosicative and Penning ionization processes. The non-equilibrium shape of these electrons occurs due to relaxation of fast electrons produced by super-elastic collisions with residual excited lithium atoms. Moreover, a reasonable agreement between McGeoch results and our calculations for the temporal behaviour of the electron density is obtained.

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