7,302 research outputs found
Electric-Field Gradient at Cd Impurities in In2o3. A FLAPW Study
We report an ab initio study of the electric-field gradient tensor (EFG) at
Cd impurities located at both inequivalent cationic sites in the semiconductor
In2O3. Calculations were performed with the FLAPW method, that allows us to
treat the electronic structure of the doped system and the atomic relaxations
introduced by the impurities in the host lattice in a fully self-consistent
way. From our results for the EFG (in excellent agreement with the
experiments), it is clear that the problem of the EFG at impurities in In2O3
cannot be described by the point-charge model and antishielding factors.Comment: 4 pages, 2 figures, and 2 table
Fourier law, phase transitions and the stationary Stefan problem
We study the one-dimensional stationary solutions of an integro-differential
equation derived by Giacomin and Lebowitz from Kawasaki dynamics in Ising
systems with Kac potentials, \cite{GiacominLebowitz}. We construct stationary
solutions with non zero current and prove the validity of the Fourier law in
the thermodynamic limit showing that below the critical temperature the limit
equilibrium profile has a discontinuity (which defines the position of the
interface) and satisfies a stationary free boundary Stefan problem.
Under-cooling and over-heating effects are also studied. We show that if
metastable values are imposed at the boundaries then the mesoscopic stationary
profile is no longer monotone and therefore the Fourier law is not satisfied.
It regains however its validity in the thermodynamic limit where the limit
profile is again monotone away from the interface
Symmetric simple exclusion process with free boundaries
We consider the one dimensional symmetric simple exclusion process (SSEP)
with additional births and deaths restricted to a subset of configurations
where there is a leftmost hole and a rightmost particle. At a fixed rate birth
of particles occur at the position of the leftmost hole and at the same rate,
independently, the rightmost particle dies. We prove convergence to a
hydrodynamic limit and discuss its relation with a free boundary problem.Comment: 29 pages, 4 figure
Phase Transitions in Ferromagnetic Ising Models with spatially dependent magnetic fields
In this paper we study the nearest neighbor Ising model with ferromagnetic
interactions in the presence of a space dependent magnetic field which vanishes
as , , as . We prove that in
dimensions for all large enough if there is a phase
transition while if there is a unique DLR state.Comment: to appear in Communications in Mathematical Physic
XAS study of the local environment of impurities in doped TiO2 thin films
In this work we present an X-ray Absorption Spectroscopy characterization of
the local environment of the impurity in room temperature ferromagnetic anatase
TiO2 thin films doped with Co, Ni, Cu, or Zn, deposited on LaAlO3 substrate by
Pulsed Laser Deposition. It was found that there is a considerable amount of
impurity atoms substituting Ti in TiO2 anatase, although the presence of metal
transition monoxide clusters can not be discarded. From our results we infer
that the observed room temperature ferromagnetism of the samples could be
assigned to the metal transition atoms replacing Ti in TiO2 anatase.Comment: 4 pages, 3 figures, 1 table, Physica B (in press
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