共查询到20条相似文献,搜索用时 625 毫秒
1.
G. Zwicknagl 《Zeitschrift für Physik B Condensed Matter》1980,40(1-2):23-29
Densities of states and electronic parameters related to superconductivity have been calculated for the transition metals Nb and Tc, representing the bulk materials by a finite cluster of atoms. The Schrödinger equation is solved for atomic potentials which have been obtained in a self-consistent band structure calculation. The results show that, in these systems, the electronic structure is determind predominantly by short-range order. 相似文献
2.
X.-M. Wang H.-P. Zheng C.-J. Li 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(2):255-263
In order to get more reliable electronic structure of
protein in aqueous solution, it is necessary to construct a simple, easy-use
equivalent potential of water molecules for protein's electronic structure
calculation. The first-principles, all-electron, ab initio calculations have been
performed to construct the equivalent potential of water molecules for the
electronic structure of Cys. The process consists of three steps. First, the
electronic structure of the cluster containing Cys and water molecules is
calculated. Then, based on the structure, the electronic structure of Cys
with the potential of water molecules is calculated using the
self-consistent cluster-embedding method. Finally, the electronic structure
of Cys with the potential of dipoles is calculated. The dipoles are adjusted
so the electronic structure of Cys with the potential of dipoles is close to
that of water molecules. The calculations show that the major effect of
water molecules on Cys' electronic structure is lowering the occupied
electronic states by about 0.032 Ry, and broadening energy gap by 16%.
The effect of water molecules on the electronic structure of Cys can be
simulated by dipoles potential. 相似文献
3.
G Kuhn S Polesya S Mankovsky J Minár H Ebert M Regus W Bensch 《J Phys Condens Matter》2012,24(30):306005
The electronic structure and magnetic properties of Cr-Sb compounds with zinc-blende and wurtzite structure have been studied by means of the Korringa-Kohn-Rostoker (KKR) band structure method. The occurrence of a half-metallic behavior has been investigated for the bulk systems as a function of lattice parameter, as well as for thin films deposited on different substrates. In the latter case the influence of the surface and interface on the electronic structure is discussed in addition. To study magnetic order in the bulk and within the films, exchange coupling parameters have been calculated from first principles. They have been used for subsequent Monte Carlo simulations, based on a classical Heisenberg Hamiltonian, to obtain the Curie temperature. 相似文献
4.
LI ChunJie ZHENG HaoPing & WANG XueMei Pohl Institute of Solid State Physics Tongji University Shanghai China 《中国科学G辑(英文版)》2007,50(1):15-30
In order to get more reliable electronic structures of proteins in aqueous solution, it is necessary to construct a potential of water molecules for protein’s electronic structure calculation. The lysine is a hydrophilic amino acid. It is positively charged (Lys+) in neutral water solution. The first-principles, all-electron, ab initio calcula-tions, based on the density functional theory, have been performed to construct such an equivalent potential of water molecules for lysine (Lys+). The process consists of three parts. First, the electronic structure of the cluster containing Lys+ and water molecules is calculated. By adjusting the positions of water molecules, the geometric structure of the cluster having minimum total energy is determined. Then, based on the structure, the electronic structure of Lys+ with the potential of water molecules is calculated using the self-consistent cluster-embedding (SCCE) method. Finally, the electronic structure of Lys+ with the potential of dipoles is calculated. The dipoles are adjusted so that the electronic structure of Lys+ with the potential of dipoles is close to that of water molecules. Thus the equivalent potential of water molecules for the electronic structure of lysine is obtained. The major effect of water molecules on lysine’s electronic structure is raising the occupied eigenvalues about 0.5032 eV, and broadening energy gap 89%. The effect of water molecules on the electronic structure of lysine can be simulated by dipoles potential. 相似文献
5.
Jonas R.F. Lima 《The European Physical Journal B - Condensed Matter and Complex Systems》2017,90(1):5
Graphene superlattices have attracted much research interest in the last years, since it is possible to manipulate the electronic properties of graphene in these structures. It has been verified that extra Dirac points appear in the electronic structure of the system. The electronic structure in the vicinity of these points has been studied for a gapless and gapped graphene superlattice and for a graphene superlattice with a spatially modulated energy gap. In each case a different behavior was obtained. In this work we show that via Fermi velocity engineering it is possible to tune the electronic properties of a graphene superlattice to match all the previous cases studied. We also obtained new features of the system never observed before, reveling that the electronic structure of graphene is very sensitive to the modulation of the Fermi velocity. The results obtained here are relevant for the development of novel graphene-based electronic devices. 相似文献
6.
The electronic and magnetic properties of ferromagnet-semiconductor (FM-SC) heterostructure systems have been studied by means of scalar-relativistic KKR-CPA band structure calculations. As a structural model for our calculations periodic multilayer systems have been assumed, taking for the ferromagnet Fe and for the semiconductor GaAs. A justification for the applicability of this geometrical model in describing the electronic and magnetic properties of the real Fe-GaAs-Fe trilayer system is given. Making use of the Coherent Potential Approximation (CPA), the influence of interdiffusion at the Fe-GaAs interface within the multilayer system has been investigated in addition. On the basis of the electronic structure calculations, the magnetic circular X-ray dichroism (MCXD) has been investigated for the L 3 -edges absorption spectra of Ga and As in the near-edge regime (XANES). In both cases the MCXD signal was found to be pronounced enough to be detectable and should motivate corresponding experimental studies. 相似文献
7.
V. G. Nazin M. N. Mikheeva M. Yu. Kuznetsov E. G. Maksimov M. V. Magnitskaya 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2007,1(1):18-25
The electronic structure of the zirconium surface with different degrees of oxidation is studied by photoelectron spectroscopy using synchrotron radiation and by electron-energy-loss spectroscopy (EELS). Measurements are performed in one experimental run in the same samples. Some previously unobserved features of the electronic structure have been disclosed. To explain the experimental results, first-principles electronic-structure calculations have been performed for hcp zirconium and for cubic and monoclinic zirconium oxide. The calculated dielectric and loss functions are compared with the EELS data. In spite of small quantitative distinctions, the experimental and calculated results are in qualitative agreement. 相似文献
8.
S. Nannarone P. Perfetti C. Quaresima C. Quaresima A. Savioa C.M. Bertoni C. Calandra F. Manghi 《Solid State Communications》1980,34(6):409-412
We present the results of an investigation of the electronic structure of heterojunctions formed by deposition of Germanium on Si (lll) surfaces. Energy Loss Spectra for various Ge coverages have been taken and compared with theoretical calculations. The results indicate that the interface is abrupt and at low coverages Ge is deposited uniformly on the substrate. Above 2 monolayers coverage modifications in the electronic structure appear probably caused by the growth mechanism. 相似文献
9.
Methanol/TiO2(110) is a model system in the surface science study of photocatalysis where methanol is taken as a hole capture. However, the highest occupied molecular orbital of adsorbed methanol lies below the valence band maximum of TiO2, preventing the hole transfer. To study the level alignment of this system, electronic structure of methanol covered TiO2(110) surface has been measured by ultraviolet photoelectron spectroscopy and the molecular orbitals of adsorbed methanol have been clearly identified. The results indicate the weak interaction between methanol and TiO2 substrate. The static electronic structure also suggests the mismatch of the energy levels. These static experiments have been performed without band gap excitation which is the prerequisite of a photocatalytic process. Future study of the transient electronic structure using time-resolved UPS has also been discussed. 相似文献
10.
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
11.
First-principles, all-electron, \textit{ab initio} calculations
have been performed to construct an equivalent water potential
for the electronic structure of serine (Ser) in solution. The
calculation is composed of three steps. The first step is to search
for the configuration of the Ser + NH2O system with a minimum
energy. The second step is to calculate the electronic structure of
Ser with the water molecule potential via the self-consistent
cluster-embedding method (SCCE), based on the result obtained in the
first step. The last step is to calculate the electronic structure
of Ser with the dipole potential after replacing the water molecules
with dipoles. The results show that the occupied states of Ser are
raised by about 0.017~Ry on average due to the effect of water. The
water effect can be successfully simulated by using the dipole potential.
The obtained equivalent potential can be applied directly to the
electronic structure calculation of protein in solution by using the
SCCE method. 相似文献
12.
13.
14.
The Tamm-type surface electronic states at the boundary of the one-dimensional structure with periodically potential profile
have been theoretically studied under the condition that the δ-shaped quantum well is at this boundary. The properties of
surface electronic states in such a structure have been compared with Tamm electronic states in the absence of a quantum well
at the lattice boundary and with electronic states localized near the δ-shaped potential well deep in the lattice. In particular,
it has been shown that the existence of the δ-shaped potential well at the lattice boundary facilitates a significant increase
in the degree of localization of Tamm-type surface electronic states and makes possible the appearance of these states at
arbitrarily small heights of lattice potential barriers. 相似文献
15.
The electronic structure of GdCuGe intermetallic compound has been studied. Spin-polarized energy spectrum calculations have been performed by the band method with allowance for strong electron correlations in the 4f-shell of gadolinium ions. Antiferromagnetic ordering of GdCuGe at low temperatures has been obtained in a theoretical calculation, with the value of the effective magnetic moment of gadolinium ions reproduced in fair agreement with experimental data. The electronic density of states has been analyzed. An optical conductivity spectrum has been calculated for GdCuGe; it reveals specific features that are analogous to the ones discovered previously in the GdCuSi compound with a similar hexagonal structure. 相似文献
16.
Generalov A. V. Brzhezinskaya M. M. Vinogradov A. S. Püttner R. Chernysheva M. V. Lukashin A. V. Eliseev A. A. 《Physics of the Solid State》2011,53(3):643-653
The Cu 2p, I 3d, and C 1sX-ray absorption spectra of the CuI@SWCNT nanocomposite prepared by filling single-walled carbon nanotubes (SWCNTs) with the
CuI melt by the capillary technique have been measured with a high-energy resolution using the equipment of the Russian-German
beamline at the BESSY electron storage ring. In order to characterize the electronic structure of the nanocomposite and possible
changes in the atomic and electronic structures of CuI and SWCNTs in the CuI@SWCNT nanocomposite, the spectra obtained have
been analyzed in the framework of the quasi-molecular approach by comparing with the spectra of the pristine (CuI and SWCNT)
and reference (CuO) systems. It has been revealed that the encapsulation of the CuI compound inside SWCNTs is accompanied
by changes in the electronic structure of CuI and SWCNTs due to the chemical interaction between the filler and carbon nanotubes
and the change in the atomic structure of CuI. 相似文献
17.
基于第一性原理平面波赝势(PWP)和广义梯度近似(GGA)方法,对闪锌矿结构(ZB)和岩盐结构(RS)的ZnSe在0—20GPa高压下的几何结构、态密度、能带结构进行了计算研究,分析了闪锌矿结构ZnSe和岩盐结构ZnSe的几何结构.在此基础上,研究了ZnSe的结构相变、弹性常数、成键情况以及相变压强下电子结构的变化机理.结果发现:通过焓相等原理得到的ZB相到RS相的相变压强为15.3GPa,而由弹性常数判据得到的相变压强为11.52GPa,但在9.5GPa左右并没有发现简单立方相的出现;在结构相变过程中,sp3轨道杂化现象并未消除,Zn原子的4s电子在RS相ZnSe的导电性中起主要贡献. 相似文献
18.
《Current Applied Physics》2003,3(2-3):293-305
Molecular electronics (ME) is rapidly evolving from physics, chemistry, biology, electronics and information technology. This is because the present-day advanced silicon chip can store about 16 million bytes of information within an area less than 1 cm2. Organic materials such as proteins, pigments and conducting polymers (CPs) have been considered as alternatives for carrying out the same functions that are presently being performed by semiconductor silicon. Among these, CPs have demanded the maximum attention. These ME materials differ from conventional polymers by having a delocalized electronic structure that can accommodate charge carriers such as electrons and holes. Besides, these conjugated electronic materials exhibit Peierl’s instabilities due to built-in highly anisotropic interactions. It has been proposed that electrical conduction in CPs occurs via non-linear (or topological) defects (solitons/polarons) generated either during polymerization or as a consequence of doping. Solitons and polarons have recently been shown to have implications in the technical development of ME devices.CPs such as polypyrroles, polythiophenes and polyanilines have been projected for applications for a wide range of ME devices. One of the main reasons for such a wide-spread interest is due to the reported observation that these interesting electronic materials exhibit full range of properties from insulator to superconductor depending upon chemical modification. CPs have been found to have applications as optical, electronic, drug-delivery, memory and biosensing devices. The major challenge confronting the material scientists including chemists and physicists is how do the properties of these electronic materials differ from those of conventional semiconductors. Another advantage lies in the fact that these materials possess specific advantages such as high packing density, possibility of controlling shape and electronic properties by chemical modification.Our group has been actively working towards the application of CPs to Schottky diodes, metal–insulator–semiconductor devices and biosensors for the past about 10 years. This paper is a review of some of the results obtained at our laboratory in the area of CP ME. 相似文献
19.
Metal-semiconductor (Schottky barrier) and semiconductor-semiconductor (heterojunction) interfaces show rectifying barrier
heights and band offsets, which are two key quantities required to optimize the performance of a device. A large number of
models and empirical theories have been put forward by various workers in the field during the last 50 years. But a proper
understanding of the microscopic origin of these quantities is still missing. In this article, our focus is mainly to present
a unified framework for first principles investigation of the electronic structure of epitaxial interfaces, in which one of
the constituents is a semiconductor. LMTO method is now a well established tool for self-consistent electronic structure calculations
of solids within LDA. Such calculations, when performed on supercell geometries, are quite successful in predicting a wide
range of interface specific electronic properties accurately and efficiently. We describe here the basic formalism of this
LMTO-supercell approach in its various levels of sophistication and apply it to investigate the electronic structure of A-
and B-type NiSi2/Si(111) interface as a prototype metal-semiconductor system, and CaF2/Si(111) interface as a prototype insulator-semiconductor system. These are a few of the most ideal lattice matched epitaxial
interfaces whose atomic and electronic structures have been extensively studied using a wide range of experimental probes.
We give here a glimpse of these experimental results and discuss the success as well as limitations of LDA calculations to
achieve accuracies useful for the device physicists. 相似文献
20.
Ernesto Lpez-Chvez J. M. Martínez Magadn Fray de Landa Castillo-Alvarado 《Journal of magnetism and magnetic materials》2004,280(2-3):293-303
A theory of disordered binary alloys AxB1−x (A=Ni, Co; B=Fe; x0.06) is used to determine the changes in the electronic structure and magnetic properties of body centered cubic (BCC) iron induced by doping with nickel and cobalt impurities. This approximation is an extension of the cluster-Bethe lattice method, in which we incorporate electronic correlations, itinerant and localized nature of electrons 3d, and both long-range and short-range chemical correlations. The magnetism is described by means of a Hubbard Hamiltonian that in conjunction with Green's functions techniques is used to calculate local densities of electronic states. For it we take an atom in the real lattice and it is joined to a Bethe's lattice with like coordination number. The magnetic moments on sites occupied for A and B atoms are obtained self-consistently. Nickel and cobalt impurities in BCC iron can provide crucial information on the modification of the electronic band structure and magnetic moments from pure Fe. The results obtained are compared with those of both pure Fe and binary alloys of Co–Fe and Ni–Fe, which have been obtained by other authors using methods such as: first-principles electronic structure calculations using the layer Korringa–Kohn–Rostoker (KKR), the full-potential linearized augmented plane wave method, the KKR coherent potential approximation combined with the local-density functional method and by the tight-binding linear-muffin-tin orbitals method, obtained good agree. These results and other that recently we have published indicate to us that our methodology can be a new alternative for calculations of the electronic structure and magnetic properties of impurities and alloys of ferromagnetic transition metals. 相似文献