66 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
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
Autocorrected Off-axis Holography of 2D Materials
The reduced dimensionality in two-dimensional materials leads a wealth of
unusual properties, which are currently explored for both fundamental and
applied sciences. In order to study the crystal structure, edge states, the
formation of defects and grain boundaries, or the impact of adsorbates, high
resolution microscopy techniques are indispensible. Here we report on the
development of an electron holography (EH) transmission electron microscopy
(TEM) technique, which facilitates high spatial resolution by an automatic
correction of geometric aberrations. Distinguished features of EH beyond
conventional TEM imaging are the gap-free spatial information signal transfer
and higher dose efficiency for certain spatial frequency bands as well as
direct access to the projected electrostatic potential of the 2D material. We
demonstrate these features at the example of h-BN, at which we measure the
electrostatic potential as a function of layer number down to the monolayer
limit and obtain evidence for a systematic increase of the potential at the
zig-zag edges.Comment: 8 pages, 5 figure
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