共查询到20条相似文献,搜索用时 15 毫秒
1.
S. Massidda R. Monnier E. Stoll 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(4):645-649
The electronic structure and the Fermi surface BaB6 are studied as a function of doping in a conventional bandstructure approach based on the local density approximation to
density functional theory (LDA). In particular it is shown that magnetic breakthrough can occur between the two sheets of
the Fermi surface disconnected by electron-hole mixing and the spin-orbit interaction. It is further suggested that angle-resolved
photoemission will see a single ellipse in the (100) plane for certain doping values, due to the finite energy/momentum resolution
of the method. Transport properties, computed within Bloch-Boltzmann theory, are also presented. The bare plasma energy is
found to be 0.6 eV in the stoichiometric compound.
Received 23 May 2000 相似文献
2.
A. Šimůnek J. Vackář K. Kunc J. Hutter 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(2):245-249
A soft, norm-conserving pseudopotential for carbon is presented and its performance tested by calculations on atomic states
and on diamond: electronic energy levels of different atomic configurations, equilibrium lattice constant, bulk modulus, and
the TA(X) frozen-phonon frequency are accurately reproduced. Convergence of the total energy of diamond with the size of the
plane-wave basis set is compared for several frequently used pseudopotentials, and it is shown that calculations with the
reported pseudopotential can be performed at considerably lower cost than with the other norm-conserving pseudopotentials,
without loosing the accuracy of the latter in predicting structural and dynamical properties. The rapid convergence of the
results with the plane-wave cutoff is comparable to the performance of the Vanderbilt's ultrasoft pseudopotentials. The transferability
of the pseudopotential to other electronic configurations is discussed.
Received 8 September 1999 相似文献
3.
N. Bouarissa 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(2):153-158
Dependencies of electronic structure and lattice properties of InN with zinc-blende structure on hydrostatic pressure are
presented based on band structures computed using the empirical pseudopotential method. The pressure behavior of the pseudopotential
form factors have been analyzed. The effect of pressure on the density of states has been examined. Trends in bonding and
ionicity under pressure are also discussed. Our results show as well that the absolute value of the Fourier transform of the
valence charge density might be useful in the prediction of the phase transition in zinc-blende materials.
Received 25 May 2001 and Received in final form 16 January 2002 相似文献
4.
S. Ghosh B. Sanyal C.B. Chaudhuri A. Mookerjee 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,23(4):455-461
We study the electronic structure and magnetic properties of disordered bcc CoxFe1-x, CrxFe1-x and MnxFe1-x alloys in their ferromagnetic phases using the Augmented Space Recursion (ASR) technique coupled with the tight-binding linearized
muffin tin orbital (TB-LMTO) method. We calculate the density of states and magnetic moment of these alloys to show the variation
upon alloying Fe with the other neighbouring 3d transition metals using arguments based on charge transfer, exchange splitting and hybridization effects.
Received 10 April 2001 and Received in final form 15 August 2001 相似文献
5.
G. Fischer E. Dormann 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(1):21-27
High-resolution 13C nuclear magnetic resonance with 1H cross polarization and 1H decoupling under magic angle spinning is measured for the quasi-one dimensional organic conductor diperylene hexafluorophosphate
(including tetrahydrofurane solvent molecules) at temperatures between 160 K and 270 K. Ab initio molecular orbital calculations are used for chemical shift analysis and for assignment of Knight shifted lines and individual
carbon positions. The coexistence of neutral perylene molecules and perylene radicals in the same radical cation salt is revealed.
From Knight and chemical shifts we were able to distinguish two inequivalent perylene radicals within the conducting stack.
The spin density distribution of the molecular electronic wave function is determined quantitatively for these radicals.
Received 29 June 1999 and Received in final form 4 November 1999 相似文献
6.
M. Taguchi F. Le Normand J. Hommet S. Rey G. Schmerber J.C. Parlebas 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(4):611-615
We study the change of the electronic structures of nickel silicides, Ni3Si and NiSi2, as well as nickel and silicon through the evolution of their valence band X-ray photoelectron spectra (v-XPS) both experimentally
and theoretically. The experimental spectra are compared to the total and partial densities of states using tight-binding
linear muffin-tin orbital method (TB-LMTO) in the atomic sphere approximation (ASA). Good agreement is found between theory
and experiment.
Received 10 July 2000 相似文献
7.
V.R. Galakhov M.A. Korotin N.A. Ovechkina E.Z. Kurmaev V.S. Gorshkov D.G. Kellerman S. Bartkowski M. Neumann 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(2):281-286
The electronic structure of LiMnO2 and Li2MnO3 was studied by means of X-ray photoelectron and soft X-ray emission spectroscopy. For LiMnO2, LSDA and LSDA+U calculations were carried out. The LSDA+U calculations are in rather good agreement with the measured valence-band structure as well as with the magnetic and electrical
properties of LiMnO2. It is shown that the band gap in LiMnO2 is determined by the charge-transfer effect.
Received 15 March 1999 and Received in final form 14 July 1999 相似文献
8.
C. Jun L. Lin T. Lu L. Yong 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(4):593-598
The embedded-cluster numerical variational method has been developed to calculate the electronic structure of perfect MgO,
F and F+-centers in MgO. The energy band, bulk density of states has been calculated by cluster Mg14O13, Mg14O12F+ and Mg14O12F. The calculated absorption energy for F+ and F centers is in good agreement with experimental data. In our calculated defect energy levels, that the first excited
state of F+-center is at CB-3.46 eV, indicates the necessity of a large photoelectron yielding energy. We also calculate the radius of
color center electron, and plot the map of charge-density distribution of valence electrons in which the structure of the
color center is shown directly.
Received 22 May 1998 相似文献
9.
U. Schwingenschlögl C. Schuster 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(1):43-47
The incommensurate composite systems M14Cu24O41 (M = Ca, Sr, La)
are based on two fundamental structural units: CuO2 chains and
Cu2O3 ladders. We present electronic structure calculations
within density functional theory in order to address the interrelations
between chains and ladders. The calculations account for the
details of the crystal structure by means of a unit cell comprising 10
chain and 7 ladder units. It turns out that chains and ladders can be treated
independently, which allows us to introduce a model system based on a
reduced unit cell. For the CuO2 chains, we find two characteristic
bands at the Fermi energy. Tight binding fits yield
nearest and next-nearest neighbour interactions of the same order of
magnitude. 相似文献
10.
H. Zheng Y. Wang G. Ma 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(1):61-69
The electronic structure of LaNi5 and its hydride LaNi5H7 are obtained using the self-consistent cluster-embedding calculation method. The Fermi level of LaNi5H7 is 5.172 eV higher than that of LaNi5. In both materials, the La 5d electrons locate nearby the Fermi levels, and make only a small contribution to the density of states (DOS) of the valence
bands. There is no significant charge transfer from La to Ni in LaNi5. But for LaNi5H7, there is a charge transfer of 1.16 electrons from La to H, and H atoms are combined mainly with Ni to form hybridized orbitals
in the energy regions far below the Fermi level. An explanation of hydrogenation of LaNi5 is proposed: It is easy for hydrogens to take off some localized La 5
d electrons near the Fermi level, and combine with Ni to form hybridized orbitals in lower energy regions. This process is
therefore in favor of energy, and forces a lattice expansion until the Fermi level rises to zero.
Received 13 July 2001 / Received in final form 10 December 2001 Published online 17 September 2002 相似文献
11.
N. Gidopoulos S. Sorella E. Tosatti 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(2):217-226
We study the quantum phase transition between a band (“ionic”) insulator and a Mott-Hubbard insulator, realized at a critical
value in a bipartite Hubbard model with two inequivalent sites, whose on-site energies differ by an offset . The study is carried out both in D=1 and D=2 (square and honeycomb lattices), using exact Lanczos diagonalization, finite-size scaling, and Berry's phase calculations
of the polarization. The Born effective charge jump from positive infinity to negative infinity previously discovered in D=1 by Resta and Sorella is confirmed to be directly connected with the transition from the band insulator to the Mott insulating
state, in agreement with recent work of Ortiz et al. In addition, symmetry is analysed, and the transition is found to be associated with a reversal of inversion symmetry in
the ground state, of magnetic origin. We also study the D=1 excitation spectrum by Lanczos diagonalization and finite-size scaling. Not only the spin gap closes at the transition,
consistent with the magnetic nature of the Mott state, but also the charge gap closes, so that the intermediate state between
the two insulators appears to be metallic. This finding, rationalized within Hartree-Fock as due to a sign change of the effective
on-site energy offset for the minority spin electrons, underlines the profound difference between the two insulators. The band-to-Mott insulator
transition is also studied and found in the same model in D=2. There too we find an associated, although weaker, polarization anomaly, with some differences between square and honeycomb
lattices. The honeycomb lattice, which does not possess an inversion symmetry, is used to demonstrate the possibility of an
inverted piezoelectric effect in this kind of ionic Mott insulator.
Received 21 May 1999 相似文献
12.
M. Said F. Ben Zid C.M. Bertoni Stefano Ossicini 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,23(2):191-199
The electronic properties of rare-earth arsenides have been calculated from first principles. In the calculations we have
treated the rare-earth f electrons both as core-like and as valence-like electrons. We consider the changes in the energy bands and in the density
of states near the Fermi level which are found to be relevant, except for the case of LuAs, and discuss this in relation with
the role played from the rare-earth 5d derived states. Moreover we show that the rare-earth 5d related bands are particularly sensitive to the variation of the lattice constant; change in the lattice constant of less
than 1% leads to a different behaviour with respect to the crossing of the rare-earth 5d derived bands and the As 4p derived bands along the Δ-direction. This point is discussed in connection with the possibility of having a semimetal-semiconductor
transition in the rare-earth arsenides.
Received 22 February 2001 相似文献
13.
C.P. Beulshausen L. Fritsche 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(2):237-247
A characteristic feature of the Full Potential Linearized Augmented Plane Wave (FLAPW)-method consists in the spatial subdivision of the charge density analogous to that of the one-particle wavefunctions,
i.e. into a portion that is expanded in terms of spherical harmonics Ylm inside the muffin-tin spheres and into a plane wave expansion of the interstitial charge density. To obtain the Hartree potential
inside the spheres one is hence forced to solve a boundary value problem at the sphere surface. In addition, in all non-equivalent
spheres each (l,m)-component of the charge density is mapped onto 300-400 radial grid points. To ensure an accelerated convergence of the calculation,
the pertinent schemes require this rather large data set to be stored and mixed within 3-6 iteration steps. We show and illustrate
for the example of a spin-polarized Ni-film with and without an oxygen overlayer and for bulk Si that this data set can be
compressed by at least two orders of magnitude if one partitions the charge density in a different way so that the relevant
portion determining the interatomic bonding can be Fourier expanded throughout the lattice cell. One thereby arrives at a
modified FLAPW-scheme that combines favorable features of the original method with virtues of the pseudopotential method which
consist in the simple construction of the Hartree potential and the efficient way of achieving self-consistency. These advantages
can be exploited to the fullest by using Fast Fourier Transform. Moreover, forces that atoms experience in off-equilibrium
positions attain a particularly simple form in terms of the charge density expansion coefficients.
Received: 31 May 1997 / Revised: 12 December 1997 / Accepted: 18 December 1997 相似文献
14.
Z. Q. Liu J. Ni 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(1):29-34
We have investigated the properties of SiCAlN quaternary
compounds composed of SiC and AlN polytypes by first-principle
calculations. We find that their band gaps have a large tunability
and are sensitive to the polytype structures. Their electronic
properties vary from wide-band-gap semiconducting to metallic due to
the complex charge transfer between the two constituents SiC and
AlN. The formation energies are also calculated. These results show
SiCAlN quaternary compounds have potential applications in the
electronic devices that can be tuned over a large wavelength range. 相似文献
15.
C. L. Lu C. P. Chang M. F. Lin 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(2):161-169
In this study, we apply the tight-binding method to
magneto-electronic properties of the AA- and ABC-stacked graphites,
which are strongly dependent on the interlayer interactions, the
magnetic field, and the stacking sequences. First of all, the
interlayer interactions induce the significant changes in the energy
dispersions, the band symmetry about the Fermi level, the overlap
between valence and conduction bands, the band width, and the
band-edge states or the symmetry points. Then, the magnetic field
induces the Peierls phase in the Bloch functions and thus strongly
affects the energy dispersions of the Landau Levels, the subband
spacings, the energy width, and the special structures in density of
states (DOS). Finally, the stacking sequences dominates over the
low-energy band overlap and the anisotropy of energy bands. The
effects mentioned above are exactly reflected in the density of
state. Here, DOS exhibits the 3D, 2D, and 1D characteristics. 相似文献
16.
A. Honecker M. Kaulke K.D. Schotte 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(3):423-434
CsCuCl3 is a ferromagnetically stacked triangular spin-1/2 antiferromagnet. We discuss models for its zero-temperature magnetization
process. The models range from three antiferromagnetically coupled ferromagnetic chains to the full three-dimensional situation.
The situation with spin-1/2 is treated by expansions around the Ising limit and exact diagonalization. Further, weak-coupling
perturbation theory is used mainly for three coupled chains which are also investigated numerically using the density-matrix
renormalization group technique. We find that already the three-chain model gives rise to the plateau-like feature at one
third of the saturation magnetization which is observed in magnetization experiments on CsCuCl3 for a magnetic field perpendicular to the crystal axis. For a magnetic field parallel to the crystal axis, a jump is observed
in the experimental magnetization curve in the region of again about one third of the saturation magnetization. In contrast
to earlier spinwave computations, we do not find any evidence for such a jump with the model in the appropriate parameter
region.
Received 25 October 1999 and Received in final form 30 December 1999 相似文献
17.
C. Acha M. Monteverde M. Núñez-Regueiro A. Kuhn M. A. Alario Franco 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(4):421-428
The electronic and positronic properties of the pentanary semiconductor alloys GaxIn1-xPySbzAs1-y-z lattice matched to GaSb have been studied. The electron wave function is calculated semiempirically using the pseudopotential
band model under the virtual crystal approximation. The positron wave function is evaluated under the point core approximation
for the ionic potential. Electronic and positronic quantities namely, electronic structure and band gaps, positron band structure,
effective mass and affinity, and electron-positron momentum densities have been predicted and their dependence on the phosphorus
composition has been discussed.
Received 30 August 2002 / Received in final form 12 February 2003 Published online 24 April 2003 相似文献
18.
H. He W. Y. Zhang 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(4):457-463
The spin-states of cobalt based perovskite compounds depend sensitively
on the valence state and local crystal environment of Co ions and the
rich physical properties arise from strong coupling among charge, spin,
and orbital degrees of freedom. While extensive studies have been carried
out in the past, most of them concentrated on the isotropic compound
LaCoO3. In this paper, using the unrestricted Hartree-Fock approximation
and the real-space recursion method, we have investigated the competition
of various magnetically ordered spin-states of anisotropic double-layered
perovskite Sr2Y0.5Ca0.5Co2O7. The energy
comparison among these states shows that the nearest-neighbor
high-spin-intermediate-spin ferromagnetically ordered state is the relevant
magnetic ground state of the compound. The magnetic structure and sizes of
magnetic moments are consistent with the recent experimental observation. 相似文献
19.
N. Bouarissa 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(2):139-143
Pseudopotential investigation of energy band gaps and charge distribution in quasi-binary (GaSb)1-x(InAs)x crystals has been reported. To the best of our knowledge, there had been no reported theoretical work on these materials.
In agreement with experiment, the quasi-binary crystals of interest showed a significant narrowing of the optical band gap
compared to the conventional GaxIn1-xAsySb1-y quaternary alloys (with x
= 1 -
y). Moreover, the absorption at the optical gaps indicated that (GaSb)1-x(InAs)x is a direct Γ to Γ band-gap semiconductor within a whole range of the x composition. The information derived from the present study predicts that the band gaps cross very important technological
spectral regions and could be useful for thermophotovoltaic applications.
Received 30 August 2002 Published online 1st April 2003
RID="a"
ID="a"Present address: Physics Department, University of M'sila, 28000 M'sila, Algeria e-mail: N_Bouarissa@yahoo.fr 相似文献
20.
E.P. Nakhmedov H. Feldmann R. Oppermann 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(3):515-520
A new diagrammatic method, which is a reformulation of Berezinskii's technique, is constructed to study the density of electronic
states of a one-channel weakly disordered ring, threaded by an external magnetic flux. The exact result obtained for the density
of states shows an oscillation of with a period of the flux quantum . As the sample length (or the impurity concentration) is reduced, a transition takes place from the weak localization regime
() to the ballistic one (). The analytical expression for the density of states shows the exact dependence of on the ring's circumference and on disorder strength for both regimes.
Received 27 December 1999 相似文献