1,097 research outputs found
theoretical and experimental results for Co-OEP on Ni(100)
Metal octaethylporphyrins (M-OEP), M-N4C20H4(C2H5)8, adsorbed at a metallic
substrate are promising candidates to provide spin dependent electric
transport. Despite these systems having been studied extensively by
experiment, details of the adsorbate geometry and surface binding are still
unclear. We have carried out density functional theory calculations for cobalt
octaethyl porphyrin (Co-OEP) adsorbate at clean and oxygen-covered Ni(100)
surfaces as well as for the free Co-OEP molecule where equilibrium structures
were obtained by corresponding energy optimizations. These geometries were
then used in calculations of Co-OEP carbon and nitrogen 1s core excitations
yielding theoretical excitation spectra to be compared with corresponding
K-edge x-ray absorption fine structure (NEXAFS) measurements. The experimental
NEXAFS spectra near the carbon K-edge of Co-OEP bulk material show large
intensity close to the ionization threshold and a triple-peak structure at
lower energies, which can be reproduced by the calculations on free Co-OEP.
The experimental nitrogen K-edge spectra of adsorbed Co-OEP layers exhibit
always a double-peak structure below ionization threshold, independent of the
layer thickness. The peaks are shifted slightly and their separation varies
with adsorbate-substrate distance. This can be explained by hybridization of N
2p with corresponding 3d contributions of the Ni substrate in the excited
final state orbitals as a result of adsorbate-substrate binding via N–Ni bond
formation
Iron porphyrin molecules on Cu(001): Influence of adlayers and ligands on the magnetic properties
The structural and magnetic properties of Fe octaethylporphyrin (OEP)
molecules on Cu(001) have been investigated by means of density functional
theory (DFT) methods and X-ray absorption spectroscopy. The molecules have been
adsorbed on the bare metal surface and on an oxygen-covered surface, which
shows a reconstruction. In order to allow
for a direct comparison between magnetic moments obtained from sum-rule
analysis and DFT we calculate the dipolar term , which is also
important in view of the magnetic anisotropy of the molecule. The measured
X-ray magnetic circular dichroism shows a strong dependence on the photon
incidence angle, which we could relate to a huge value of , e.g. on
Cu(001) amounts to -2.07\,\mbo{} for normal incidence leading to a
reduction of the effective spin moment . Calculations have also
been performed to study the influence of possible ligands such as Cl and O
atoms on the magnetic properties of the molecule and the interaction between
molecule and surface, because the experimental spectra display a clear
dependence on the ligand, which is used to stabilize the molecule in the gas
phase. Both types of ligands weaken the hybridization between surface and
porphyrin molecule and change the magnetic spin state of the molecule, but the
changes in the X-ray absorption are clearly related to residual Cl ligands.Comment: 17 figures, full articl
Ferromagnetic coupling of mononuclear Fe centers in a self-assembled metal-organic network on Au(111)
The magnetic state and magnetic coupling of individual atoms in nanoscale
structures relies on a delicate balance between different interactions with the
atomic-scale surrounding. Using scanning tunneling microscopy, we resolve the
self-assembled formation of highly ordered bilayer structures of Fe atoms and
organic linker molecules (T4PT) when deposited on a Au(111) surface. The Fe
atoms are encaged in a three-dimensional coordination motif by three T4PT
molecules in the surface plane and an additional T4PT unit on top. Within this
crystal field, the Fe atoms retain a magnetic ground state with easy-axis
anisotropy, as evidenced by X-ray absorption spectroscopy and X-ray magnetic
circular dichroism. The magnetization curves reveal the existence of
ferromagnetic coupling between the Fe centers
Magnetic coupling of porphyrin molecules through graphene
Graphene is expected to complement todays Si-based information technology. In
particular, magnetic molecules in contact with graphene constitute a
tantalizing approach towards organic spin electronics because of the reduced
conductivity mismatch at the interface. In such a system a bit is represented
by a single molecular magnetic moment, which must be stabilized against thermal
fluctuations. Here, we show in a combined experimental and theoretical study
that the moments of paramagnetic Co-octaethylporphyrin (CoOEP) molecules on
graphene can be aligned by a remarkable antiferromagnetic coupling to a Ni
substrate underneath the graphene. This coupling is mediated via the \pi\
electronic system of graphene, while no covalent bonds between the molecule and
the substrate are established.Comment: 27 pages, 12 figures, Accepted at Adv. Mate
Транспортная логистика: проблемы и перспективы развития в таможенном деле
Выпускная квалификационная работа посвящена исследованию транспортной логистике в таможенном деле. Целью данной работы является комплексный анализ факторов, механизмов и проблем трансформации таможенной логистики в глобальной торговой системе и обоснование направлений адаптации таможенной логистики России в условиях либерализации международной торговли. Задачи: •Понятие, виды, функции логистики •Задачи транспортной логистики •Сущность таможенной логистики •Проблемы становления таможенной логистики •Ключевые проблемы таможенной логистики •Перспективы развития таможенной логистики.
Объектом исследования является процесс формирования и реализации таможенной логистики в глобальной торговой системе.The final qualifying work is devoted to the study of transport logistics in the customs business.
The purpose of this work is a comprehensive analysis of the factors, mechanisms and problems of the transformation of customs logistics in the global trading system and the rationale for adapting the customs logistics of Russia in the context of the liberalization of international trade
On Combining Functional Verification and Performance Evaluation using CADP
Considering functional correctness and performance evaluation in a common framework is desirable, both for scientific and economic reasons. In this report, we describe how the CADP toolbox, originally designed for verifying the functional correctness of LOTOS specifications, can also be used for performance evaluation. We illustrate the proposed approach by the performance study of the SCSI-2 bus arbitration protocol
PrIC3: Property Directed Reachability for MDPs
IC3 has been a leap forward in symbolic model checking. This paper proposes
PrIC3 (pronounced pricy-three), a conservative extension of IC3 to symbolic
model checking of MDPs. Our main focus is to develop the theory underlying
PrIC3. Alongside, we present a first implementation of PrIC3 including the key
ingredients from IC3 such as generalization, repushing, and propagation
Hierarchical structure in the orbital entanglement spectrum in Fractional Quantum Hall systems
We investigate the non-universal part of the orbital entanglement spectrum
(OES) of the nu = 1/3 fractional quantum Hall effect (FQH) ground-state with
Coulomb interactions. The non-universal part of the spectrum is the part that
is missing in the Laughlin model state OES whose level counting is completely
determined by its topological order. We find that the OES levels of the Coulomb
interaction ground-state are organized in a hierarchical structure that mimic
the excitation-energy structure of the model pseudopotential Hamiltonian which
has a Laughlin ground state. These structures can be accurately modeled using
Jain's "composite fermion" quasihole-quasiparticle excitation wavefunctions. To
emphasize the connection between the entanglement spectrum and the energy
spectrum, we also consider the thermodynamical OES of the model pseudopotential
Hamiltonian at finite temperature. The observed good match between the
thermodynamical OES and the Coulomb OES suggests a relation between the
entanglement gap and the true energy gap.Comment: 16 pages, 19 figure
Probabilistic Model-Based Safety Analysis
Model-based safety analysis approaches aim at finding critical failure
combinations by analysis of models of the whole system (i.e. software,
hardware, failure modes and environment). The advantage of these methods
compared to traditional approaches is that the analysis of the whole system
gives more precise results. Only few model-based approaches have been applied
to answer quantitative questions in safety analysis, often limited to analysis
of specific failure propagation models, limited types of failure modes or
without system dynamics and behavior, as direct quantitative analysis is uses
large amounts of computing resources. New achievements in the domain of
(probabilistic) model-checking now allow for overcoming this problem.
This paper shows how functional models based on synchronous parallel
semantics, which can be used for system design, implementation and qualitative
safety analysis, can be directly re-used for (model-based) quantitative safety
analysis. Accurate modeling of different types of probabilistic failure
occurrence is shown as well as accurate interpretation of the results of the
analysis. This allows for reliable and expressive assessment of the safety of a
system in early design stages
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