共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
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
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.
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
5.
C. Hébert M. Willinger D.S. Su P. Pongratz P. Schattschneider R. Schlögl 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(4):407-414
Band-structure (BS) calculations of the density of states (DOS) using the full potential augmented plane waves code WIEN97
were performed on the four single-valence vanadium oxides VO, V2O3, VO2 and V2O5. The DOS are discussed with respect to the distortions of the VO6 octahedra, the oxidation states of vanadium and the orbital hybridisations of oxygen atoms. The simulated oxygen K-edge fine
structures (ELNES) calculated with the TELNES program were compared with experimental results obtained by electron energy-loss
spectrometry (EELS), showing good agreement. We show that changes in the fine structures of the investigated vanadium oxides
mainly result from changes in the O-p DOS and not from the shift of the DOS according to a rigid band model.
Received 17 December 2001 / Received in final form 19 June 2002 Published online 13 August 2002 相似文献
6.
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
7.
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
8.
Y.M. Yarmoshenko M.I. Katsnelson E.I. Shreder E.Z. Kurmaev A. Slebarski S. Plogmann T. Schlathölter J. Braun M. Neumann 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(1):1-3
The XPS MnL-spectra of Co2MnSn, a nearly half-metallic ferromagnet (HMF) and Pd2MnSn were investigated. The most drastical feature of the spectra observed is the well-defined magnetic splitting of the Mn
2p
3/2
, 2p
1/2
lines. This gives direct evidence of the existence of well-defined local magnetic moments in Heusler alloys in comparison
with other itinerant-electron ferromagnets. The calculations of Mn2p XPS spectra of these materials were carried out using
a fully relativistic generalization of the one-step model of photoemission and show excellent agreement with experiment.
Received: 31 October 1997 / Received in final form: 28 November 1997 / Accepted: 18 December 1997 相似文献
9.
M. Talanana M. Benakki F. Amalou S. Bouarab C. Demangeat 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,22(4):497-503
We present an ab initio study of the magnetic surface reconstructions of the B2 FeV alloy using a self-consistent tight-binding linearized muffin
tin orbital method developed in the atomic spheres approximation. For (001) and (111), the surface reconstruction stabilizes
configurations unstable in the bulk alloy. When Fe is at the (001) surface, a c(2×2) in-plane antiferromagnetic order is found to be the ground state with magnetic moments of -2.32 and 2.27. A p(1×1) ↓ ferromagnetic order is displayed in case of V toplayer with a magnetic moment of -1.83. At the (111) surface, we obtain for Fe toplayer two solutions p(1×1)↑ and p(2×1). The configuration p(1×1)↑ is found to be the ground state with a magnetic moment per atom of 2.34. For V toplayer, only the p(1×1) ↓ solution is obtained with a moment of -0.84. In all cases, the Fe-V coupling is always antiparallel like in the bulk. Our results are discussed and compared to experiments.
Received 11 August 2000 and Received in final form 8 June 2001 相似文献
10.
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
11.
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
12.
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
13.
X. Wu A.K. Ray 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(3):345-351
The electronic and geometric structures of bulk PuO2 and its (110) surface have been studied using a periodic model within the generalized gradient approximation (GGA) of density
functional theory (DFT). The sixty core electrons of the Pu atom have been represented by a relativistic effective core potential
and scalar relativistic effects have been incorporated on the valence orbitals. For bulk PuO2, we predict an equilibrium lattice constant of 10.10 a.u. and a cohesive energy of 17.28 eV, in good agreement with experimental
data. For the (110) surface, upon relaxation, the distance between the top layer and the next layer is found to decrease by
0.12 ?, i.e. 5.3% of the corresponding interlayer distance in the bulk. The distance between the two oxygen atoms on the top layer is
found to increase by 0.15 ?, i.e. 5.6% of the corresponding bulk value. The small surface relaxation energy of 0.268 eV per unit cell indicates the fair stability
of this surface. The effective charges on Pu and O atoms show that the chemical bonding in this system is not purely ionic.
Together with the metallic feature of the density of states (DOS) on the surface, the effective charge distribution provides
some basis for understanding surface reactivity and corresponding support for catalysis.
Received 16 June 2000 相似文献
14.
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
15.
Phase evolution of layered cobalt oxides versus varying corrugation of the cobalt-oxygen basal plane
A general spin-state model and a qualitative physical picture have been proposed for a class of lately synthesized layered
cobalt oxides (LCOs) by means of density functional calculations. As the plane corrugation of the cobalt-oxygen layer decreases,
the LCOs evolve from a high-spin (HS) superexchange-coupled antiferromagnetic (AFM) insulator to an almost-HS AFM/ferromagnetic
(FM) competing system where the FM coupling is mediated via the p-d exchange by an increasing amount of delocalized pdσ holes having mainly the planar O 2p character. It is tentatively suggested that the delocalized holes more than 0.3 per CoO2 basal square are likely necessary for the insulator-metal and/or AFM-FM transitions in the corrugation-weakened LCOs. A phase
control may be realized in LCOs by varying the plane corrugation (thus modifying the hole concentration) through an ionic-size
change of the neighboring layers on both sides of the cobalt-oxygen layer. In addition, a few experiments are suggested for
a check of the present model and picture.
Received 28 July 2002 / Received in final form 10 October 2002 Published online 31 December 2002 相似文献
16.
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
17.
Nishant N. Patel K. B. Joshi 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(1):19-23
Using empirical pseudopotential method Γ-L crossover is found for
the Ga0.74Al0.26Sb. The conduction band minimum is observed to
switch at the (0.87, 0, 0) point for Ga0.51Al0.49Sb which shifts to
the X point for Ga0.21Al0.79Sb and remains at X leading finally to
indirect band gap in AlSb. Band structure calculations for a large number of
alloys are performed and bowing parameters bX and bL are proposed
for the EX and EL respectively. Our findings may serve as
directive to select the materials in a range of composition to examine the
bowing parameters and thereby effective mass experimentally for the
GaxAl1-xSb alloys. 相似文献
18.
R. Capelli P. Monachesi R. Del Sole G.C. Gazzadi 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(1):117-123
The dielectric and the loss functions of Ni(111) are calculated by the Full Potential Linear Muffin Tin Orbitals (FPLMTO)
ab initio method whithin the three-layers model (vacuum/surface/bulk). Particular attention is devoted to determine surface and bulk
state contributions to the spectra. Good agreement is found with recent experimental EELS data on the Fe-covered Ni(111) surface.
Received 10 July 2002 Published online 19 November 2002 相似文献
19.
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
20.
S. Haffner M. Dressel D. Groult C. Schlenker 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(2):167-175
The potassium doped monophosphate tungsten bronzes KxP4W8O32 are two-dimensional metals which show a metal-to-metal transition at a critical temperature which depends on the doping level.
The metal-to-metal transition is accompanied by the formation of a commensurate charge density wave with wave vector (π/b,0) which is independent of the doping level. Undoped P4W8O32, on the other hand, has two metal-to-metal transitions which are connected to the formation of incommensurate charge density
waves. We measured the infrared reflectivity of the series KxP4W8O32 (x
= 0 - 1.57) in the spectral range from 100 to 10 000 cm-1 for room temperature and well below the critical temperature. Polarization-dependent infrared spectra find a two-dimensional
behavior in the normal and the charge density wave state and show signatures of hybridization between one- and two-dimensional
conduction bands. In undoped P4W8O32 the essentials of the charge density wave state can be understood from the nesting vectors of the calculated Fermi surface
and two gaps are observed in the infrared spectra. The gap sizes are a factor of about 2.5 bigger than the predictions from
mean-field theory in the weak-coupling limit which suggests medium- or strong electron-phonon coupling. For potassium doped
KxP4W8O32 one gap is observed in the charge density wave state. The energetics of the charge density formation may be dominated by
the energy required for the lattice modulation.
Received 27 April 2001 and Received in final form 21 September 2001 相似文献