1,569 research outputs found
Generalized momenta of mass and their applications to the flow of compressible fluid
We present a technique that allows to obtain certain results in the
compressible fluid theory: in particular, it is a nonexistence result for the
highly decreasing at infinity solutions to the Navier-Stokes equations, the
construction of the solutions with uniform deformation and the study of
behavior of the boundary of a material volume of liquid.Comment: 10 pages, Proceedings of the International Conference on Hyperbolic
Problems, Lyon, 2006, France. In pres
Doping-driven Mott transition in La_{1-x}Sr_xTiO_3 via simultaneous electron and hole doping of t2g subbands
The insulator to metal transition in LaTiO_3 induced by La substitution via
Sr is studied within multi-band exact diagonalization dynamical mean field
theory at finite temperatures. It is shown that weak hole doping triggers a
large interorbital charge transfer, with simultaneous electron and hole doping
of t2g subbands. The transition is first-order and exhibits phase separation
between insulator and metal. In the metallic phase, subband compressibilities
become very large and have opposite signs. Electron doping gives rise to an
interorbital charge flow in the same direction as hole doping. These results
can be understood in terms of a strong orbital depolarization.Comment: 4 pages, 5 figure
Post density functional theoretical studies of highly polar semiconductive Pb(TiNi)O solid solutions: The effects of cation arrangement on band gap
We use a combination of conventional density functional theory (DFT) and
post-DFT methods, including the local density approximation plus Hubbard
(LDA+), PBE0, and self-consistent to study the electronic properties of
Ni-substituted PbTiO (Ni-PTO) solid solutions. We find that LDA
calculations yield unreasonable band structures, especially for Ni-PTO solid
solutions that contain an uninterrupted NiO layer. Accurate treatment of
localized states in transition-metal oxides like Ni-PTO requires post-DFT
methods. -site Ni/Ti cation ordering is also investigated. The -site
cation arrangement alters the bonding between Ni and O, and therefore strongly
affects the band gap () of Ni-PTO. We predict that Ni-PTO solid
solutions should have a direct band gap in the visible light energy range, with
polarization similar to the parent PbTiO. This combination of properties
make Ni-PTO solid solutions promising candidate materials for solar energy
conversion devices.Comment: 19 pages, 6 figure
Nonmonotonical crossover of the effective susceptibility exponent
We have numerically determined the behavior of the magnetic susceptibility
upon approach of the critical point in two-dimensional spin systems with an
interaction range that was varied over nearly two orders of magnitude. The full
crossover from classical to Ising-like critical behavior, spanning several
decades in the reduced temperature, could be observed. Our results convincingly
show that the effective susceptibility exponent gamma_eff changes
nonmonotonically from its classical to its Ising value when approaching the
critical point in the ordered phase. In the disordered phase the behavior is
monotonic. Furthermore the hypothesis that the crossover function is universal
is supported.Comment: 4 pages RevTeX 3.0/3.1, 5 Encapsulated PostScript figures. Uses
epsf.sty. Accepted for publication in Physical Review Letters. Also available
as PostScript and PDF file at http://www.tn.tudelft.nl/tn/erikpubs.htm
Study of exclusive semileptonic and nonleptonic decays of B-c(-) in a nonrelativistic quark model
We present results for different observables measured in semileptonic and nonleptonic decays of the B-c(-) meson. The calculations have been done within the framework of a nonrelativistic constituent quark model. In order to check the sensitivity of all our results against the interquark interaction we use five different quark-quark potentials. We obtain form factors, decay widths, and asymmetry parameters for semileptonic B-c(-)-> c (c) over bar and B-c(-)->(B) over bar decays. In the limit of infinite heavy quark mass, our model reproduces the constraints of heavy quark spin symmetry. For the actual heavy quark masses we find nonetheless large corrections to that limiting situation for some form factors. We also analyze exclusive nonleptonic two-meson decay channels within the factorization approximation
Electronic structure and effects of dynamical electron correlation in ferromagnetic bcc-Fe, fcc-Ni and antiferromagnetic NiO
LDA+DMFT method in the framework of the iterative perturbation theory (IPT)
with full LDA Hamiltonian without mapping onto the effective Wannier orbitals.
We then apply this LDA+DMFT method to ferromagnetic bcc-Fe and fcc-Ni as a test
of transition metal, and to antiferromagnetic NiO as an example of transition
metal oxide. In Fe and Ni, the width of occupied 3d bands is narrower than
those in LDA and Ni 6eV satellite appears. In NiO, the resultant electronic
structure is of charge-transfer insulator type and the band gap is 4.3eV. These
results are in good agreement with the experimental XPS. The configuration
mixing and dynamical correlation effects play a crucial role in these results
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