排序方式: 共有333条查询结果,搜索用时 859 毫秒
81.
The density of states (DOS) of fcc and hcp structures of Al has been calculated for normal and high pressures. It has been found that the DOS of both structures, near the Fermi level, is similar over a range of compressed volumes close to the fcc-hcp transition volume (V/V0∼0.53). This similarity is the reason for the reported coexistence of fcc-hcp phases over a wide range of pressures near the fcc-hcp phase transition. All calculations have been performed using the FP-LAPW method with GGA. 相似文献
82.
A theoretical study of structural, electronic and optical properties of cubic BaTiO3 and BaZrO3 perovskites is presented, using the full-potential linear augmented plane wave (FP-LAPW) method as implemented in the WIEN2K code. In this approach the local density approximation (LDA) is used for the exchange-correlation (XC) potential. Results are given for lattice constant, bulk modulus, its pressure derivative, band structure, density of states, pressure coefficients of energy gaps and refractive indices. The results are compared with previous calculations and experimental data. 相似文献
83.
Hideki Koyama 《Solid State Communications》2006,138(12):567-570
Linearly-polarized infrared (1.06 μm) laser light with intensities ranging from 5.3 to 97 mW/cm2 has been used to obtain anisotropically luminescent porous silicon (PSi) layers by photoanodic etching in a hydrofluoric acid solution. Remarkably large photoluminescence (PL) anisotropy has been observed in samples prepared with the highest illumination intensity. These samples show very low degrees of linear polarization when the PL excitation light is polarized parallel to the polarization direction of the etching light. When the excitation light is polarized perpendicular to that, we obtain usual degrees of linear polarization of several percent. This result indicates that anisotropic Si nanostructures in PSi layers can be made isotropic with high orientation selectivity by the polarized-light assisted technique. A simple two-dimensional model is presented to explain the observed prominent anisotropy. 相似文献
84.
85.
Allen P. Mills Jr. 《Applied Surface Science》2008,255(1):3-20
The purpose of this paper is to remember as many good qualities of our friend Karl Canter as I can, as an antidote to the loss of such a magnanimous, generous, inventive and amusing person. The paper endeavours to distill the essence in simple terms of some of Karl's important scientific contributions and say what I know of how these accomplishments were made possible and molded by his various character traits, illustrated with the few anecdotes that I remember. 相似文献
86.
In the context of the search for environment-respectful, lead- and bismuth-free chemical compounds for devices such as actuators, SnTiO3 (ST) is investigated from first principles within DFT. Full geometry optimization provides a stable tetragonal structure relative to cubic one. From the equation of state the equilibrium volume of SnTiO3 is found smaller than ferroelectric PbTiO3 (PT) in agreement with a smaller Sn2+ radius. While ionic displacements exhibit similar trends between ST and PT, a larger tetragonality (c/a ratio) for ST results in a larger polarization, PST = 1.1 Cm−2. Within ST analyzes of site projected density of states and chemical bonding indicate a reinforcement of the bond covalence with respect to Pb homologue. Both PT and ST exhibit anomalous large effective charges and the dielectric constant of ST is calculated larger than PT. 相似文献
87.
The surfactant effect of Au in ZnO nanostructures growth is studied using first-principles slab calculations based on density functional theory. The atomic structure and electronic properties of one monolayer of Au atoms on polar ZnO surfaces are examined. It is found that (1) one monolayer (ML) of Au capping layer on the ZnO polar surfaces may modify the growing properties of ZnO nanostructures by enhancing the binding energy by 0.41 eV/atom for Zn adsorption on the polar surfaces; (2) the Au adlayer on the polar ZnO surfaces seems more active for the adsorption of Zn atoms, which may be at the very heart of the effect that Au acts as catalyst for the growth of the ZnO nanostructures; and (3) total energy calculations show that the gold on-top geometry is energetically favorable than the gold diffused geometry, which may be useful to understand the phenomenon that Au particles are only found at the end of ZnO nanostructures during the growth process. 相似文献
88.
M. Lemmer B. Hilling M. Wöhlecke M. Imlau A. A. Lebedev V. V. Bryksin M. P. Petrov 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(1):9-14
The structural parameters and hydrostatic pressure coefficients of
CdSxTe1-x in the two phases, namely zinc-blende and NaCl as well
as the transition pressures from zinc-blende to NaCl structures at various S
concentrations are presented. The calculations are performed using the full
potential linearized augmented plane wave (FP-LAPW) method within the
density functional theory (DFT) in the local density approximation (LDA),
and two developed refinements, namely the generalized gradient approximation
(GGA) of Perdew et al. for the structural properties and
Engel-Vosko for the band structure calculations. Detailed
comparisons are made with published experimental and theoretical data and
show generally good agreement. The present results regarding the studied
quantities for compositions x in the 0–1 range (0 < x < 1) and for the NaCl
phase are predictions and may serve as a reference for experimental work. 相似文献
89.
G. Ugur N. Arıkan 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(3):319-322
The structural and electronic properties of MgAuSn in the cubic
AlLiSi structure have been studied, using density functional theory
within the local density approximation. The calculated lattice
constant for MgAuSn is found to be in good agreement with its
experimental value. Our calculated electronic structure is also
compared in detail with a recent tight-binding. A
linear-response approach to density-functional theory is used to
calculate the phonon spectrum and density of states for MgAuSn. 相似文献
90.
First principles study of the electronic structures of erbium
silicides with non-frozen 4f treatment
C. L. Ma S. Picozzi X. Wang Z. Q. Yang 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(3):297-303
The electronic structures (especially 4f states) of hexagonal and
tetragonal erbium silicides are investigated within density functional
theory. Contrary to previous theoretical studies on these compounds, Er 4f
electrons are treated as valence state electrons, explicitly taking into
account the on-site Coulomb interactions. Total energy calculations show
that the relaxed hexagonal ErSi1.7 is more stable than the tetragonal
structure, consistently with related experimental observations. The
calculated total density of states of the hexagonal ErSi1.7 agrees well
with the experimental valence-band spectrum in a wide energy range from 0 to
12 eV below the Fermi level. In addition, our study indicates that the
occupied 4f states in erbium silicides can also locate in the energy range
of 0–4.0 eV below the Fermi energy, much different from the prediction of
the previously adopted Er ion model. 相似文献