798 research outputs found
Structural, electronic properties and the features of chemical bonding in layered 1111-oxyarsenides LaRhAsO and LaIrAsO: ab initio modeling
The comparative study of structural, electronic properties, topology of the
Fermi surface, and the features of chemical bonding in layered
1111-oxyarsenides LaRhAsO and LaIrAsO has been performed based on the results
of ab initio modeling of their electronic structure. It was established that
only weak sensitivity with respect both to electron and hole doping is expected
for LaIrAsO being non-magnetic metal, however, the Rh-containing compound
should be characterized with weak band magnetism, and the hole doping is
expected to be able to move its ground state away from the boundary of magnetic
instability. The mentioned feature allows to consider LaRhAsO oxyarsenide as a
possible "electron analogue" of LaFeAsO compound being the initial phase for
the layered FeAs-superconductors.Comment: 19 pages, 5 figure
Magnetic and electronic properties of nitrogen-doped lanthanum sesquioxide La2O3 as predicted from first principles
Using the ab initio FLAPW-GGA method we examine the electronic and magnetic
properties of nitrogen-doped non-magnetic sesquioxide La2O3 emphasizing the
role of doping sites in the occurrence of d0-magnetism. We predict the
magnetization of La2O3 induced by nitrogen impurity in both octahedral and
tetrahedral sites of the oxygen sublattice. The most interesting results are
that (i) the total magnetic moments (about 1 {\mu}B per supercells) are
independent of the doping site, whereas (ii) the electronic spectra of these
systems differ drastically: La2O3:N with six-fold coordinated nitrogen behaves
as a narrow-band-gap magnetic semiconductor, whereas with four-fold coordinated
nitrogen is predicted to be a magnetic half-metal. This effect is explained
taking into account the differences in N-2pz versus N-2px,y orbital splitting
for various doping sites. Thus, the type of the doping site is one of the
essential factors for designing of new d0-magnetic materials with promising
properties.Comment: 5 pages, 3 figure
Electronic properties of hexagonal tungsten monocarbide WC with 3d impurities from first-principles calculations
First principles FLAPW- GGA calculations have been performed to predict the
structural, electronic, cohesive and magnetic properties for hexagonal WC doped
with all 3d metals. The optimized lattice parameters, density of states,
cohesive and formation energies have been obtained and analyzed for ternary
solid solutions with nominal compositions W0.875M0.125C (where M = Sc, Ti, ...,
Ni, Cu). In addition, the magnetic properties of these solid solutions have
been examined, and magnetization has been established for W0.875Co0.125C.Comment: 14 pages, 5 figure
Structural, magnetic and electronic properties of quaternary oxybismuthides LaOMBi (where M = Sc, Ti ... Ni, Cu) - possible parent phases for new superconducting materials
The extensive ab initio total energy calculations using the VASP-PAW method
with the generalized gradient approximation (GGA) for the exchange-correlation
potential are applied to systematic investigation of structural, electronic and
magnetic properties in quaternary oxybismuthides LaOMBi (where M = Sc, Ti...Ni,
Cu). The energy spectrum features similar to lanthanum-iron oxyarsenide LaOFeAs
and non-magnetic ground state are indicative of superconductivity possible in
lanthanum-nickel oxybismuthide LaONiBi.Comment: 10 pages,3 figure
First-principles study of cubic perovskites SrMO_3 (M = Ti, V, Zr and Nb)
Using the full-potential linearized-augmented-plane-wave (FLAPW) method, we
have analyzed systematically the trends in the structural and electronic
properties of the 3d and 4d transition-metal oxides SrMO_3 (M = Ti, V, Zr and
Nb). The optimized lattice parameters, bulk modules, densities of states, band
structures and charge density distributions are obtained and compared with the
available theoretical and experimental data. The energy gap between O2p - Md
bands increases as the covalency of the system decreases going from 3d to 4d
based perovskites. The electron configurations of Sr(Ti,Zr)O_3 and Sr(V,Nb)O_3
usually referred to as d^0 and d^1 oxides, respectively, differ considerably
from these idealized "ionic" configurations, and the deviations increase with
increasing of the d-p covalent overlap in the oxides.Comment: 7 pager, 3 figure
Electronic band structure of low-temperature YB12, YB6 superconductors and layered YB2, MgB2 diborides
Electronic band structure of boron-rich low-temperature superconductors
UB12-like dodecaboride YB12 and CaB6-like hexaboride YB6 are investigated using
the first-principle FLMTO calculations and compared with one for layered YB2
and the new "medium-Tc" superconductor MgB2 diborides.Comment: 6 pages, 4 figure
Electronic structure for new layered high-temperature superconductors CaAFe4As4 (A=K, Rb, Cs): FLAPW-GGA calculations
Recently, new FeAs based high-temperature superconductors CaAFe4As4 (A=K, Rb,
Cs) with a layered tetragonal crystal structure were synthesized (TC ~ 30 K).
In this Letter, we report for the first time the band structures, Fermi surface
topology, total and partial densities of electronic states and interatomic
interactions for CaAFe4As4 as estimated by means of the first-principles
FLAPW-GGA calculations. The interatomic bonding picture can be represented as a
highly anisotropic mixture of metallic, covalent, and ionic contributions,
which are realized inside Fe4As4 layered blocks and between these blocks and
Ca, A atomic sheets. The Fermi surfaces of these systems have a multisheet
character and are compiled of a large number of cylinders at the edges and in
the central part of the Brillouin zone. It is established that the
high-temperature superconductivity in CaAFe4As4 compounds as in other related
systems correlates well with such structure parameters as bond angles and anion
height.Comment: 15 pagers, 6 tables, 5 figure
Electronic band structures and intra-atomic interactions in layered quaternary oxyarsenides LaZnAsO and YZnAsO
First-principle FLAPW-GGA band structure calculations are employed to obtain
the structural, electronic properties and chemical bonding picture for two
related layered phases, namely, quaternary oxyarsenides LaZnAsO and YZnAsO.
These compounds are found to be direct-transition type semiconductors with the
GGA gaps of about 0.65-1.30 eV. The peculiarities of chemical bonding in these
phases are investigated and discussed in comparison with quaternary oxyarsenide
LaFeAsO - a basic phase for the newly discovered 26-52K superconductors.Comment: 13 pages, 3 figure
Electronic band structure and inter-atomic bonding in layered 1111-like Th-based pnictide oxides ThCuPO, ThCuAsO, ThAgPO, and ThAgAsO from first principles calculations
First-principles FLAPW-GGA band structure calculations were employed to
examine the structural, electronic properties and the chemical bonding picture
for four ZrCuSiAs-like Th-based quaternary pnictide oxides ThCuPO, ThCuAsO,
ThAgPO, and ThAgAsO. These compounds were found to be semimetals and may be
viewed as "intermediate" systems between two main isostructural groups of
superconducting and semiconducting 1111 phases. The Th 5f states participate
actively in the formation of valence bands and the Th 5f states for ThMPnO
phases are itinerant and partially occupied. We found also that the bonding
picture in ThMPnO phases can be classified as a high-anisotropic mixture of
ionic and covalent contributions: inside [Th2O2] and [M2Pn2] blocks, mixed
covalent-ionic bonds take place, whereas between the adjacent [Th2O2]/[M2Pn2]
blocks, ionic bonds emerge owing to [Th2O2] \to [M2Pn2] charge transfer.Comment: 16 pages, 6 figure
First-Principles Prediction of Novel Magnetic Materials Based on ZrCuSiAs-like Semiconducting Pnictide-Oxides
We assumed that significant enlargement of the functional properties of the
family of quaternary ZrCuSiAs-like pnictide-oxides, often called also as 1111
phases, which are known now first of all as parent phases for new FeAs
superconductors, may be achieved by replacement of nonmagnetic ions by magnetic
ions in semiconducting ZrCuSiAs-like phases. We checked this assumption by
means of first-principles FLAPW-GGA calculations using a wide-band-gap
semiconductor YZnAsO doped with Mn, Fe, and Co as an example. Our main finding
is that substitution of Mn, Fe, and Co for Zn leads to drastic transformations
of electronic and magnetic properties of the parent material: as distinct from
the non-magnetic YZnAsO, the examined doped phases YZn0.89Mn0.11AsO,
YZn0.89Fe0.11AsO, and YZn0.89Co0.11AsO behave as a magnetic semiconductor, a
magnetic half-metal or as a magnetic gapless semi-metal, respectively.Comment: 2 figure
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