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Goumri-Said S. Salomon L. Dufour J. P. De Fornel F. 《Optical and Quantum Electronics》2004,36(9):787-806
Numerical simulation of a two-dimensional probe–object system for photon scanning tunneling microscope is presented. The R-matrix propagation algorithm incorporated into the Fourier modal method was used to achieve an extended capability for modeling of a realistic system consisting of both a probe and a sample. The type of the mode guided through the dielectric probe and the coupling of the near-field to fundamental guiding mode in the probe are discussed. The influence of the probe parameters on the near-field images is investigated. Three different probe shapes were simulated in the constant height scanning mode. The transmitted flux intensity through the probe was found to be strongly dependent on the tip shape. The analysis shows a good agreement of the obtained results with the available theoretical works and confirming experimental results. The proposed numerical scheme can find applications for near-field probe characterization and provides an understanding of the degree of perturbation introduced by a probe tip in the experiment. 相似文献
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In this work, we aimed to examine the spin-polarized electronic band structures, the local densities of states as well as the magnetism of ZnMnTe- and CdMnTe-diluted magnetic semiconductors (DMSs) in the ferromagnetic phase, and with 25% of Mn. The calculations are performed by the recent ab initio full potential augmented plane waves plus local orbitals (FP−L/APW+lo) method within the spin-polarized density-functional theory and the local spin density approximation. We have determined the exchange splittings produced by the Mn d states: Δx(d) and Δx(pd), and we found that the effective potential for the minority spin is more attractive than that for the majority spin. Also, we show the nature of the bonding from the charge spin-densities calculations, and we calculate the exchange constants N0α and N0β, which mimics a typical magneto-optical experiment. The calculated total magnetic moment is found to be equal to 5μB for both DMSs. This value indicates that every Mn impurity adds no hole carriers to the perfect ZnTe and CdTe crystals. Furthermore, we found that p–d hybridization reduces the local magnetic moment of Mn and produces small local magnetic moments on the nonmagnetic Te, Zn and Cd sites. 相似文献
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Mazmira Mohamad Rashid Ahmed Amirudin Shaari Souraya Goumri-Said 《Chemistry Central journal》2017,11(1):125
Theoretical simulations were designed by first principles approach of density functional theory to investigate the structural and optoelectronic properties of different structural classes of perylene; isolated perylene, diindeno[1,2,3-cd:1′,2′,3′-lm]perylene (DIP) molecule and DIP molecular crystal. The presence of molecular interactions in DIP crystal proved its structure-dependent behaviours. The herringbone molecular arrangement of DIP crystal has influenced the electronic properties by triggering the intermolecular interactions that reduced the energy gaps between HOMO and LUMO of the crystal. Strong hybridization resulting from dense charges population near zero Fermi energy has pushed valence band maxima in the density of states of all perylene structures to higher energies. Under small energy input, charges are transferred continuously as observed in the spectra of conductivity and dielectric. The existence of strong absorption intensities are consistent with the former works and supported by the obtained polarized reflectivity and loss spectra.
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Mohammed Benali Kanoun Igor R. Shein Souraya Goumri-Said 《Solid State Communications》2010,150(23-24):1095-1098
We study structural, elastic, and electronic properties for three RuB2 phases using ab initio total-energy calculations within the density functional theory. The orthorhombic and hexagonal structures are mechanically stable. More precisely, the orthorhombic is more stable than the hexagonal form. Results of bulk modulus, which are in good agreement with experimental data, show that the considered structures are potentially highly compressible materials. This is confirmed by the calculation of the hardness, indicating that RuB2 is an ultracompressible material, but not a superhard material. 相似文献
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Nawel Kanoun-Bouayed Mohammed Benali Kanoun Souraya Goumri-Said 《Central European Journal of Physics》2011,9(1):205-212
We report plane-wave pseudo-potential ab initio calculations using density functional theory in order to investigate the structural parameters, elastic constants, bonding
properties and polycrystalline parameters of copper nitrides in zincblende, rocksalt and fluorite structures. Total and partial
densities of states indicate a metallic character of these copper nitrides. We estimate bond strengths and types of atomic
bonds using Mulliken charge density population analysis and by calculating the electronic localized function. These results
reveal the coexistence of covalent, ionic, and metallic bonding. 相似文献
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Mohammed Benali Kanoun Souraya Goumri-Said Ali H. Reshak Abdelkarim E. Merad 《Solid State Sciences》2010,12(5):887-898
We have performed ab initio calculations for the nanolaminates Zr2AC (A = Ti, In, Tl, Si, Ge, Sn, Pb, P, As, S) ceramics to study their electronic structure, elastic and optical properties. In this work, we used the accurate augmented plane wave plus local orbital method with density functional theory to find the equilibrium structural parameters, dielectric functions and to compute the full elastic tensors. The obtained elastic constants were used to quantify the stiffness of the Zr2AC phases and to appraise their mechanical stability. The relationship between elastic, electronic and valence electron concentration is discussed. Our results show that the bulk modulus and shear modulus increase across the periodic table for Zr2AC. Furthermore, trends in elastic stiffness are well explained in terms of electronic structure analysis, as occupation of valence electrons in states near the Fermi level of Zr2AC. We show that increments of bulk moduli originate from additional valence electrons filling states involving Zr d–A p. We show also that Zr d–A p hybridizations are located just below the Fermi level and are weaker bonds than the Zr d–C p hybridizations, which are deeper in energy. As a function of the p-state filling of the A element the Zr d–A p bands are driven to deeper energy. The optical spectra were analyzed by means of the electronic structure, which provides theoretical understanding of the conduction mechanism of these ceramics. 相似文献
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Bakhtiar Ul Haq R. Ahmed Souraya Goumri-Said A. Shaari A. Afaq 《Phase Transitions》2013,86(12):1167-1177
In this study, we report investigations of structural and electronic properties of ZnO in wurtzite (WZ), rock salt (RS) and zinc-blende (ZB) phases. Calculations have been done with full-potential linearized augmented plane wave plus local orbital method developed within the frame work of Density Functional Theory (DFT). For structural properties investigations, Perdew and Wang proposed local density approximations (LDA) and Perdew et al. proposed generalized gradient approximations (GGA) have been applied. Where for electronic properties in addition to these, Tran–Blaha modified Becke–Johnson (mBJ) potential has been used. Our computed band gap values of ZnO in WZ and ZB phases with mBJ potential are significantly improved compared to those with LDA and GGA; however, in RS phase, energy gap is significantly overestimated compared to experimental measurements. The Zn-d band was found to be more narrower with mBJ potential than that of LDA and GGA. On the other hand, our evaluated crystal field splitting energy values overestimate the experimental values. 相似文献
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Frontiers of Physics - This article presents a review of our present understanding of the spin structure of the unpolarized hadron. Particular attention is paid to the quark sector at leading... 相似文献
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