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1.
A. Bouhemadou R. Khenata M. Chegaar 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,56(3):209-215
Using first-principles density functional calculations, the effect of high
pressures, up to 20 GPa, on the structural and elastic properties of
Zr2AlX and Ti2AlX, with X = C and N, were studied by means of the
pseudo-potential plane-waves method. Calculations were performed within the
local density approximation to the exchange-correlation approximation
energy. The lattice constants and the internal parameters are in agreement
with the available results. The elastic constants and their pressure
dependence are calculated using the static finite strain technique. We
derived the bulk and shear moduli, Young's moduli and Poisson's ratio for
ideal polycrystalline Zr2AlX and Ti2AlX aggregates. We estimated
the Debye temperature of Zr2AlX and Ti2AlX from the average sound
velocity. This is the first quantitative theoretical prediction of the
elastic properties of Zr2AlC, Zr2AlN and Ti2AlN compounds,
and it still awaits experimental confirmation. 相似文献
2.
G. Rakotovelo P. S. Moussounda M. F. Haroun P. Légaré A. Rakotomahevitra J. C. Parlebas 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,57(3):291-297
Progress of scanning tunneling microscopy (STM) allowed to handle various molecules adsorbed on a given surface. New concepts
emerged with molecules on surfaces considered as nano machines by themselves. In this context, a thorough knowledge of surfaces
and adsorbed molecules at an atomic scale is thus particularly invaluable. In this work, within the framework of density functional
theory (DFT), we present an electronic and structural ab initio study of a BaTiO3 (001) surface (perovskite structure) in its paraelectric phase. As far as we know the atomic and molecular adsorption of
oxygen at surface is then analyzed for the first time in the literature. Relaxation is taken into account for several layers.
Its analysis for a depth of at least four layers enables us to conclude that a reasonable approximation for a BaTiO3 (001) surface is provided with a slab made up of nine plans. The relative stability of two possible terminations is considered.
By using a kinetic energy cut off of 400 eV, we found that a surface with BaO termination is more stable than with TiO2 termination. Consequently, a surface with BaO termination was chosen to adsorb either O atom or O2 molecule and the corresponding calculations were performed with a coverage 1 on a (1×1) cell. A series of cases with O2 molecule adsorbed in various geometrical configurations are also analyzed. For O2, the most favorable adsorption is obtained when the molecule is placed horizontally, with its axis, directed along the Ba-Ba
axis and with its centre of gravity located above a Ba atom. The corresponding value of the adsorption energy is -9.70 eV
per molecule (-4.85 eV per O atom). The molecule is then rather extended since the O–O distance measures 1.829 ?. By comparison,
the adsorption energy of an O atom directly located above a Ba atom is only -3.50 eV. Therefore we are allowed to conclude
that the O–O interaction stabilizes atomic adsorption. Also the local densities of states (LDOS) corresponding to various
situations are discussed in the present paper. Up to now, we are not aware of experimental data to be compared to our calculated
results. 相似文献
3.
A.K. Ray J.C. Boettger 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(3):429-433
The linear combinations of Gaussian type orbitals fitting function (LCGTO-FF) method is used to study the electronic and geometrical
properties of plutonium monolayers with square and hexagonal symmetry. The effects of several common approximations are examined:
(1) scalar-relativity vs. full-relativity (i.e., with spin-orbit coupling included); (2) paramagnetic vs. spin-polarized; and (3) local-density approximation (LDA) vs. generalized- gradient approximation (GGA). The results indicate that spin-orbit coupling has a much stronger effect on the
monolayer properties compared to the effects of spin-polarization. In general, the GGA is found to predict a larger lattice
constant and a smaller cohesive energy compared to LDA predictions. We also find a significant compression of the monolayers
compared to the bulk, contradicting the only other published result on a Pu monolayer. The current result supports the existence
of a δ-like surface on α-Pu.
Received 17 October 2001 Published online 6 June 2002 相似文献
4.
Hao Wang Ying Chen Yasunori Kaneta Shuichi Iwata 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(2):155-165
The Si3N4 and Ge3N4 are important
structural ceramics with many applications because of their
attractive high temperature and oxidation resistant properties. The
high-pressure and high-temperature spinel phases of these two
materials were noticed to have wide, direct electronic band gaps.
Other single and double spinel nitrides formed from IVA and IVB
group elements have also attracted much attention. Present research
focuses on selecting a special substance with promising optical
properties and stability besides the attractive electronic
properties. The formation energies of spinel nitrides are calculated
and stabilities of a group of spinel nitrides are discussed, the
structural and electronic properties of them are investigated in
detail. By random phase approximation (RPA), the optical properties
of spinel nitrides are researched. We obtain that
γ-SiGe2N4 has some promising properties with
potential technological applications from various aspects. The band
transitions which contribute most to the peak of ε2
have been identified. An assumption is proposed to raise the peak of
ε2. 相似文献
5.
H. Salehi N. Shahtahmasebi S.M. Hosseini 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(2):177-180
The electronic structure, total density of states DOS and electronic density in ferroelectric tetragonal crystal BaTiO3 are studied using WIEN2k package. This employs the full potential-linearized augmented plan wave FP-LAPW method in the framework
of the density functional theory DFT with the generalized gradient approximation (GGA). The results show an indirect band
gap of 2.30 eV at the Γ point in the Brillouin zone. The calculated band structure and density of states of BaTiO3 agree with the previous experimental and theoretical results, as do the charge distribution and the prediction of the nature
of the chemical bonding.
Received 11 December 2002 / Received in final form 3 February 2003 Published online 1st April 2003
RID="a"
ID="a"e-mail: salehihamid@yahoo.com 相似文献
6.
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
7.
Z. Lu Z. Yang 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(4):455-460
First-principles electronic structure calculations of noble metals (NM=Pd, Pt)/Ce0.75Zr0.25O2 systems are presented. It is found that: the NM adatoms do not prefer to stay at the atop or the bridge sites of the cations
(Ce and Zr), but prefer to be adsorbed at or around the anion sites. The most preferable adsorption sites for both the Pd
and Pt adatoms are the O-bridge sites neighboring the Zr dopant. The Pt adatom show much stronger interaction with the Ce0.75Zr0.25O2(111) surface than does the Pd adatom. The interactions of the NM/Ce0.75Zr0.25O2(111) interfaces are stronger than those of the corresponding NM/ceria(111) interfaces. There are some metal induced gap states
(MIGS) appeared in the gaps of the NM/Ce0.75Zr0.25O2(111) interfaces, which are important to catalytic properties of the NM/Ce0.75Zr0.25O2(111) catalysts. 相似文献
8.
S. Saib N. Bouarissa P. Rodríguez-Hernández A. Muñoz 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(4):435-438
We present a theoretical study of the structural properties, namely
lattice constant, bulk modulus and its pressure derivative of zinc-blende
GaxIn1-xN. The calculations are performed using first-principles
calculations in the framework of the density-functional-theory
within the local density approximation under the virtual
crystal approximation. The computed values are in good
agreement with the available experimental data. The composition dependence
of the studied quantities is examined. Besides, the deviation of the alloy
lattice constant from Vegard's law is evaluated. 相似文献
9.
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
10.
A. Shaukat Y. Saeed N. Ikram H. Akbarzadeh 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(4):439-446
First principles calculations have been performed within the
framework of density functional theory to investigate the structural,
electronic and optical properties of all four possible B1, B2, B3 and B4
phases of CaS. Apart from the standard local density approximation (LDA) and
GGA (PBE), a more accurate nonempirical density functional generalized
gradient approximation (GGA), as proposed by Wu and Cohen [Phys. Rev. B 73,
235116 (2006)] for the exchange-correlation energy, EXC, has been
attempted in these calculations. Calculated electronic structure and the
density of states are analyzed in terms of the contribution of Ca d states
and S s and p states in determining the nature of the fundamental band gap
in various phases. Reflectivity, R (ω), the real and imaginary part
of the dielectric functions, ε(ω), have been
calculated for all the phases and the results have been discussed and
compared with the existing experimental data. 相似文献
11.
X. D. Zhang M. L. Guo C. L. Liu L. A. Zhang W. Y. Zhang Y. Q. Ding Q. Wu X. Feng 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(4):417-421
A first-principles study has been performed to evaluate the electronic and
optical properties of wurtzite Zn1-xMgxO. Substitutional doping is
considered with Mg concentrations of x = 0, 0.0625, 0.125, 0.1875 and 0.25,
respectively. Mg incorporation can induce band gap widening due to the
decrease of Zn 4s states. The imaginary part of the dielectric function shows
that the optical transition from band edge emission decreases slightly with
increasing Mg contents. The optical band gap also increases from 3.2 to 3.7
eV with increasing Mg contents from 0.0625 to 0.25. The calculated results
suggest that relatively high Mg concentration is necessary for effective
band gap engineering of wurtzite Zn1-xMgxO. 相似文献
12.
A. H. Reshak Z. Charifi H. Baaziz 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(4):463-468
We present the results of the ab initio theoretical study of the optical properties for PbFX (X = Cl, Br, I) compounds in its matlockite-type structure using the
full potential linearized augmented plane wave (FP-LAPW) method as
implemented in the WIEN2K code. We employed generalized gradient
approximation (GGA), which is based on exchange-correlation energy
optimization to calculate the total energy. Also we have used the
Engel-Vosko GGA formalism, which optimizes the corresponding potential for
band structure calculations. Our calculations show that the valence band
maximum (VBM) and conduction band minimum (CBM) are located at Z resulting
in a direct energy gap. We present calculations of the frequency-dependent
complex dielectric function ε( ω) and its
zero-frequency limit ε1 ( 0 ). We find that the
values of ε1 ( 0 ) increases with decreasing the
energy gap. The reflectivity spectra and absorption coefficient has been
calculated and compared with the available experimental data. The optical
properties are analyzed and the origin of some of the peaks in the spectra
is discussed in terms of the calculated electronic structure. 相似文献
13.
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
14.
E. Krotscheck E. R. Hernández S. Janecek M. S. Kaczmarski R. Wahl 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):173-176
We present the implementation of a fast real-space
algorithm for density functional calculations for atomic
nanoclusters. The numerical method is based on a fourth-order
operator splitting technique for the solution of the Kohn-Sham
equation [1]. The convergence of the procedure is about one
order of magnitude better than that of previously used second-order operator
factorizations. The method has now been extended to deal with
non-local pseudopotentials of the Kleinman-Bylander [2]
type, permitting calculations for realistic systems, without
significantly degrading the convergence rate. We demonstrate the
convergence of the method for the examples C and C60 and
present examples of structure calculations of Na and Mg clusters. 相似文献
15.
Elastic and brittle properties of the B2-MgRE (RE = Sc,Y, Ce,Pr,
Nd,Gd, Tb,Dy, Ho,Er) intermetallics
Y. Wu W. Hu 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(1):75-81
The brittle and elastic properties of the B2-MgRE (RE = Sc, Y, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er) intermetallics have been investigated
using
first-principles density functional calculations. The calculated equilibrium
lattice constants and enthalpies of formation are in overall agreement with
the available experiment and theoretical results. The related physical
properties of those compounds are compared with that of ductile YCu. The
Fermi energy occurs above a peak in the DOS for B2-MgRE intermetallics,
whereas for ductile YCu the Fermi energy occurs near a minimum in the DOS.
For B2-YCu, the partial density of states of d-states at the Fermi energy is
low, while for B2-MgRE the RE d-states are partially occupied, indicating
their important roles in the directional bonding for this material. The
Cauchy pressure (C12-C44) and the ratio of bulk to shear modulus
B/G are used to assess the brittle/ductile behavior of B2-MgRE and YCu
compounds. It can be concluded that the B2-MgRE alloys have brittle
behavior. MgSc is the most brittle, and MgHo is the least brittle amongst
those alloys. 相似文献
16.
V. Hizhnyakov I. Tehver G. Benedek 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,70(4):507-512
We investigate, using first-principles calculations, the electronic
structure of substitutional and vacancy defects in a boron nitride
monolayer. We found that the incorporation of a substitutional carbon atom
induces appreciable modification on the electronic properties, when compared
to a non-defective boron nitride sheet. The incorporation of substitutional
carbon impurity also induces a significant reduction of the work function.
In addition, we found that defects introduce electronic states in the
energy-gap region, with strong impact on the optical properties of the
material. The calculation results indicate that spin polarization is
obtained when substitutional impurities or vacancy defects are introduced in
the structure 相似文献
17.
S. Ramasubramanian M. Rajagoplan R. Thangavel J. Kumar 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,69(2):265-268
Elastic and Thermodynamical properties of Ti1-xZrxC have been investigated using LAPW + lo within the density-functional theory with the generalized gradient approximation.
We have studied the stability of the alloy Ti1-xZrxC as a function of Zr composition in rocksalt (B1) structure by calculating the elastic constants C11, C12 and C44 using the tetragonal and trigonal distortions. Mechanical properties such as Poisson ratio, bulk, shear and Young’s modulii
of Ti1-xZrxC are calculated. The Debye temperature and hardness are also computed for the first time to our knowledge for Ti1-xZrxC in various compositions. 相似文献
18.
Carmine Autieri 《哲学杂志》2013,93(34):3276-3295
AbstractWe report ab initio density functional calculations of the structural and magnetic properties, and the electronic structure of CrAs. To simulate the observed pressure-driven experimental results, we perform our analysis for different volumes of the unit cell, showing that the structural, magnetic and electronic properties strongly depend on the size of the cell. We find that the calculated quantities are in good agreement with the experimental data, and we review our results in terms of the observed superconductivity. 相似文献
19.
C. Wang C. Y. Wang 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,54(2):243-247
An ideal single vacancy can be formed by removing one carbon atom
from a hexagonal network. The vacancy is one of the most important
defect structures in carbon nanotubes (CNTs). Vacancies can
affect the mechanical, chemical, and electronic properties of CNTs.
We have systematically investigated single vacancies and their
related point defects for achiral, single-walled carbon nanotubes
(SWNTs) using first-principles calculations. The structures around
single vacancies undergo reconstruction without constraint, forming ground-stateor metastable-state structures. The 5-1DB
and 3DB point defects can be
formed in armchair CNTS, while the 5-1DB-P and 5-1DB-T point defects can be
formed in zigzag CNTs. The related point defects can transform into
each other under certain conditions. The formation energies of
armchair CNTs change smoothly with the tube radius, while in the
case of the 3DB defect, as the radius get larger, the formation energies
tend towards a constant value. 相似文献
20.
A. Alsaad A. Ahmad 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,54(2):151-156
First-principles calculations are performed to compute the e33
piezoelectric coefficients of GaN, ScN and (ScxGa1-xN) alloys
exhibiting an alternation of hexagonal GaN, with hexagonal ScN along the c-axis. For Sc compositions larger than 50%, each atom has nearly five nearest
neighbors (i.e., the ground state exhibits a phase that is five-fold
coordinated). On the other hand, Sc-deficient (Sc, Ga) N alloys adopt a
ground-state that is four-fold coordinated). The magnitude of e33 in
the Sc-deficient ideally ordered (Sc0.25Ga0.75N) is found to be larger
than the magnitude of the corresponding e33 coefficients resulting from
the compositional weighted average over the hexagonal (h-ScN) and the wurtzite (w-GaN) parent compounds. On the other hand, the e33 coefficients of the Sc-rich
ordered (Sc0.75Ga0.25N) is found to be negligibly small. In addition, e33
piezoelectric coefficients in ordered (Sc0.5Ga0.5N) exhibit quite
large magnitudes, due to the nonpolar to polar transition occurs at Sc composition x = 0.5, and thus can bridge the corresponding coefficients of (Ga, In) N and
ferroelectric alloys. The microscopic origins for this huge enhancement in
the piezoelectric behavior in Sc-low and Sc-intermediate alloys and the role
of each atom are revealed and discussed. 相似文献