277 research outputs found
Trends in structural and electronic properties for layered SrRu2As2, BaRu2As2, SrRh2As2 and BaRh2As2 from ab initio calculations
Based on first-principle FLAPW-GGA calculations, we have investigated the
systematic trends in structural and electronic properties of a newly discovered
group of ThCr2Si2-like arsenides: SrRu2As2, BaRu2As2, SrRh2As2 and BaRh2As2.
Our results show that the replacement of an alkaline earth metal (Sr - Ba) and
4d metal (Ru - Rh) leads to various types of anisotropic deformations of the
crystal structure caused by strong anisotropy of inter-atomic bonds.
The band structure, density of states and Fermi surfaces have been evaluated
and discussed. Appreciable changes in the near-Fermi bands and the Fermi
surface topology found as going from (Sr,Ba)Ru2As2 to (Sr,Ba)Rh2As2 reflect the
growth of the 3D-like type of dispersion for these systems, which is
accompanied by an increase in the near-Fermi density of states. The
inter-atomic bonding in (Sr,Ba)(Ru,Rh)2As2 phases adopts a complex anisotropic
character, where the bonding in [(Ru,Rh)2As2] blocks is of a mixed
metallic-ionic-covalent type whereas between adjacent [(Ru,Rh)2As2] blocks and
(Sr,Ba) atomic sheets, ionic interactions emerge; thus these systems may be
classified as ionic metals.Comment: 17 pages, 5 figure
Elastic properties and chemical bonding in ternary arsenide SrFe2As2 and quaternary oxyarsenide LaFeAsO - basic phases for new 38-55K superconductors
We report the first-principle FLAPW-GGA calculations of the elastic
properties of two related layered phases, namely, the ternary arsenide SrFe2As2
and the quaternary oxyarsenide LaFeAsO - basic phases for the newly discovered
"122" and "1111" 38-55K superconductors. The independent elastic constants
(Cij), bulk moduli, compressibility, and shear moduli are evaluated and
discussed. The numerical estimates of the elastic parameters of the
polycrystalline SrFe2As2 and LaFeAsO ceramics are performed for the first time.
Additionally, the peculiarities of chemical bonding in these phases are
discussed.Comment: 8 pages, 2 figure
The band structure of hexagonal diborides ZrB2, VB2, NbB2 and TaB2 in comparison with the superconducting MgB2
The band structure and the Fermi surface of hexagonal diborides ZrB2, VB2,
NbB2, TaB2 have been studied by the self-consistent full-potential LMTO method
and compared with those for the isostructural superconductor MgB2. Factors
responsible for the superconducting properties of AlB2-like diborides are
analyzed, and the results obtained are compared with previous calculations and
available experimental data.Comment: 7 pages, 4 figure
Elastic properties of superconducting LiFeAs from first principles
The first-principles FLAPW-GGA calculations of the elastic properties of
recently discovered superconducting LiFeAs are reported. The independent
elastic constants (Cij), bulk modulus, compressibility, and shear modulus are
evaluated and discussed. Additionally, numerical estimates of the elastic
parameters of the polycrystalline LiFeAs ceramics are performed for the first
time.Comment: 7 pager
Electronic properties and Fermi surface for new Fe-free layered superconductor BaTi2Bi2O from first principles
Very recently, as an important step in the development of layered Fe-free
pnictide-oxide superconductors, the new phase BaTi2Bi2O was discovered which
has the highest TC (about 4.6 K) among all related non-doped systems. In this
Letter, we report for the first time the electronic bands, Fermi surface
topology, total and partial densities of electronic states for BaTi2Bi2O
obtained by means of the first-principles FLAPW-GGA calculations. The
inter-atomic bonding picture is described as a high-anisotropic mixture of
metallic, covalent, and ionic contributions. Besides, the structural and
electronic factors, which can be responsible for the increased transition
temperature for BaTi2Bi2O (as compared with related pnictide-oxides BaTi2As2O
and BaTi2Sb2O), are discussed.Comment: 7 pages, 3 figure
Electronic properties of superconducting Sr4V2Fe2As2O6 versus Sr4Sc2Fe2As2O6
First principle FLAPW-GGA calculations have been performed with the purpose
to understand the peculiarities of band structure and Fermi surface topology
for recently discovered superconductor: Sr4V2Fe2As2O - in comparison with
isostructural phase Sr4Sc2Fe2As2O6. Our main finding is that the replacement of
Sc on vanadium leads to drastic transformation of electronic, magnetic and
conductive properties of these materials: as against non-magnetic
Sr4Sc2Fe2As2O6 which is formed from non-magnetic conducting [Fe2As2] and
insulating [Sr4Sc2O6] blocks, Sr4V2Fe2As2O6 consists from non-magnetic
conducting [Fe2As2] blocks and [Sr4V2O6] blocks which exhibit magnetic
half-metallic properties.Comment: 12 pages, 5 figure
Trends in structural, electronic properties, Fermi surface topology, and inter-atomic bonding in the series of ternary layered dichalcogenides KNi2S2, KNi2Se2, and KNi2Te2 from first principles calculations
By means of the FLAPW-GGA approach, we have systematically studied the
structural and electronic properties of tetragonal dichalcogenides KNi2Ch2 (Ch
= S, Se, and Te). Our results show that replacements of chalcogens (S -> Se ->
Te) lead to anisotropic deformations of the crystals structure, which are
related to the strong anisotropic character of the inter-atomic bonds, where
inside the [Ni2Ch2] blocks, mixed covalent-ionic-metallic bonds occur, whereas
between the adjacent [Ni2Ch2] blocks and K atomic sheets, ionic bonds emerge.
We found that in the sequence KNi2S2 -> KNi2Se2 -> KNi2Te2 (i) the overall band
structure (where the near-Fermi valence bands are due mainly to the Ni states)
is preserved, but the width of the common valence band and the widths of the
separate subbands and the gaps decrease; (ii) the total DOSs at the Fermi level
also decrease; and (iii) for the Fermi surfaces, the most appreciable changes
are demonstrated by the hole-like sheets, when a necklace-like topology is
formed for the 2D-like sheets and the volume of the closed pockets decreases.
Some trends in structural and electronic parameters for ThCr2Si2-type layered
dichalcogenides, KNi2Ch2, KFe2Ch2, KCo2Se2, are discussed.Comment: 10 pagers, 6 figure
Electronic band structure and Fermi surface for new layered superconductor LaO0.5F0.5BiS2 in comparison with parent phase LaOBiS2 from first principles
By means of first-principles calculations? we have probed the peculiarities
of the elecrtonic band structure and Fermi surface for the recently discovered
layered superconductor LaO0.5F0.5BiSi2 in comparison with the parent phase
LaOBiO2. The electronic factors prpmoting the transition of LaOBiS2 upon
fluorine doping to superconducting state: inter-layer charge transfer, the
evolution of the Fermi surface, and the dependence of the near-Fermi densities
of states on x for LaO1-xFxBiS2 are evaluated and discussed in comparison with
the available experiments.Comment: 8 pages, 4 figure
First-principles study of electronic band structure and elastic properties of superconducting nanolaminate Ti2InC
The full-potential linearized augmented plane wave method with the
generalized gradient approximation for the exchange-correlation potential
(FLAPW-GGA) is used to predict the electronic and elastic properties of the
newly discovered superconducting nanolaminate Ti2InC. The band structure,
density of states and Fermi surface features are discussed. The optimized
lattice parameters, independent elastic constants, bulk and shear moduli,
compressibility are evaluated and discussed. The elastic parameters of the
polycrystalline Ti2InC ceramics are estimated numerically for the first time.Comment: 11 pages, 3 figure
Structural, electronic properties and Fermi surface of ThCr2Si2-type tetragonal KFe2S2, KFe2Se2, and KFe2Te2 phases as parent systems of new ternary iron-chalcogenide superconductors
First principles FLAPW-GGA method was used for the comparative study of the
structural and electronic properties of three related tetragonal ThCr2Si2-type
phases KFe2Ch2, where Ch are S, Se, and Te. The main trends in electronic
bands, densities of states and Fermi surfaces for AFe2Ch2 are analyzed in
relation to their structural parameters. We found that at the anion
replacements (SSeTe) any critical changes in electronic structure of
KFe2Ch2 phases are absent. On the other hand, our analysis of structural and
electronic parameters for hypothetical KFe2Te2 allows to assume that this
system may be proposed as perspective parent phase for search of new
iron-chalcogenide superconducting materials.Comment: 7 pages, 4 figure
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