554 research outputs found
Universality of (2+1)-dimensional restricted solid-on-solid models
Extensive dynamical simulations of Restricted Solid on Solid models in
dimensions have been done using parallel multisurface algorithms
implemented on graphics cards. Numerical evidence is presented that these
models exhibit KPZ surface growth scaling, irrespective of the step heights
. We show that by increasing the corrections to scaling increase, thus
smaller step-sized models describe better the asymptotic, long-wave-scaling
behavior
Bit-Vectorized GPU Implementation of a Stochastic Cellular Automaton Model for Surface Growth
Stochastic surface growth models aid in studying properties of universality
classes like the Kardar--Paris--Zhang class. High precision results obtained
from large scale computational studies can be transferred to many physical
systems. Many properties, such as roughening and some two-time functions can be
studied using stochastic cellular automaton (SCA) variants of stochastic
models. Here we present a highly efficient SCA implementation of a surface
growth model capable of simulating billions of lattice sites on a single GPU.
We also provide insight into cases requiring arbitrary random probabilities
which are not accessible through bit-vectorization.Comment: INES 2016, Budapest http://www.ines-conf.org/ines-conf/2016index.htm
Electronic transport properties through thiophenes on switchable domains
The electronic transport of electrons and holes through stacks of
,\ome ga-dicyano-,'-dibutyl- quaterthiophene (DCNDBQT)
as part of a nov el organic ferroic field-effect transistor (OFFET) is
investigated. The novel ap plication of a ferroelectric instead of a dielectric
substrate provides the poss ibility to switch bit-wise the ferroelectric
domains and to employ the polarizat ion of these domains as a gate field in an
organic semiconductor. A device conta ining very thin DCNDBQT films of around
20 nm thickness is intended to be suitab le for logical as well as optical
applications. We investigate the device proper ties with the help of a
phenomenological model called multilayer organic light-e mitting diodes
(MOLED), which was extended to transverse fields. The results sho wed, that
space charge and image charge effects play a crucial role in these org anic
devices
First-principles study of ferroelectric domain walls in multiferroic bismuth ferrite
We present a first-principles density functional study of the structural,
electronic and magnetic properties of the ferroelectric domain walls in
multiferroic BiFeO3. We find that domain walls in which the rotations of the
oxygen octahedra do not change their phase when the polarization reorients are
the most favorable, and of these the 109 degree domain wall centered around the
BiO plane has the lowest energy. The 109 degree and 180 degree walls have a
significant change in the component of their polarization perpendicular to the
wall; the corresponding step in the electrostatic potential is consistent with
a recent report of electrical conductivity at the domain walls. Finally, we
show that changes in the Fe-O-Fe bond angles at the domain walls cause changes
in the canting of the Fe magnetic moments which can enhance the local
magnetization at the domain walls.Comment: 9 pages, 20 figure
Defect-induced magnetism in graphite through neutron irradiation
We have investigated the variation in the magnetization of highly ordered
pyrolytic graphite (HOPG) after neutron irradiation, which introduces defects
in the bulk sample and consequently gives rise to a large magnetic signal. We
observe strong paramagnetism in HOPG, increasing with the neutron fluence. We
correlate the induced paramagnetism with structural defects by comparison with
density-functional theory calculations. In addition to the in-plane vacancies,
the trans-planar defects also contribute to the magnetization. The lack of any
magnetic order between the local moments is possibly due to the absence of
hydrogen/nitrogen chemisorption, or the magnetic order cannot be established at
all in the bulk form.Comment: 10 pages, 8 figure
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