94 research outputs found
Electronic Structure of the c(2x2)O/Cu(001) System
The locally self-consistent real space multiple scattering technique has been
applied to calculate the electronic structure and chemical binding for the
c(2x2)O/Cu(001) system, as a function of -- the height of oxygen
above the fourfold hollow sites. It is found that the chemical binding between
oxygen and copper has a mixed ionic-covalent character for all plausible values
of . Furthermore, the electron charge transfer from Cu to O depends
strongly on and is traced to the variation of the long-range
electrostatic part of the potential. A competition between the hybridization of
Cu1- with O- and Cu1- with O- states
controls modification of the electronic structure when oxygen atoms approach
the Cu(001) surface. The anisotropy of the oxygen valence electron charge
density is found to be strongly and non-monotonically dependent on .Comment: 14 pages, 7 figures, 1 tabl
Relationship between Electronic and Geometric Structures of the O/Cu(001) System
The electronic structure of the
O/Cu(001) system has been calculated using locally self-consistent, real space
multiple scattering technique based on first principles. Oxygen atoms are found
to perturb differentially the long-range Madelung potentials, and hence the
local electronic subbands at neighboring Cu sites. As a result the
hybridization of the oxygen electronic states with those of its neighbors leads
to bonding of varying ionic and covalent mix. Comparison of results with those
for the c(2x2) overlayer shows that the perturbation is much stronger and the
Coulomb lattice energy much higher for it than for the
phase. The main driving force for the
0.5ML oxygen surface structure formation on Cu(001) is thus the long-range
Coulomb interaction which also controls the charge transfer and chemical
binding in the system.Comment: 17 pages, 8 figure
Improving the quality of the industrial enterprise management based on the network-centric approach
The article examines the network-centric approach to the industrial enterprise management to improve the ef ciency and effectiveness in the implementation of production plans and maximize responsiveness to customers. A network-centric management means the decentralized enterprise group management. A group means a set of enterprise divisions, which should solve by joint efforts a certain case that occurs in the production process. The network-centric management involves more delegation of authority to the lower elements of the enterprise’s organizational structure. The industrial enterprise is considered as a large complex system (production system) functioning and controlled amidst various types of uncertainty: information support uncertainty and goal uncertainty or multicriteria uncertainty. The information support uncertainty occurs because the complex system functioning always takes place in the context of incomplete and fuzzy information. Goal uncertainty or multicriteria uncertainty caused by a great number of goalsestablished for the production system. The network-centric management task de nition by the production system is formulated. The authors offer a mathematical model for optimal planning of consumers’ orders production with the participation of the main enterprise divisions. The methods of formalization of various types of uncertainty in production planning tasks are considered on the basis of the application of the fuzzy sets theory. An enterprise command center is offered as an effective tool for making management decisions by divisions. The article demonstrates that decentralized group management methods can improve the ef ciency and effectiveness of the implementation of production plans through the self-organization mechanisms of enterprise divisions.The work has been prepared with the financial support from the Russian Ministry of Education and Science (Contract No. 02.G25.31.0068 of 23.05.2013 as part of the measure to implement Decision of the Russian Government No. 218)
C and S induces changes in the electronic and geometric structure of Pd(533) and Pd(320)
We have performed ab initio electronic structure calculations of C and S
adsorption on two vicinal surfaces of Pd with different terrace geometry and
width. We find both adsorbates to induce a significant perturbation of the
surface electronic and geometric structure of Pd(533) and Pd(320). In
particular C adsorbed at the bridge site at the edge of a Pd chain in Pd(320)
is found to penetrate the surface to form a sub-surface structure. The
adsorption energies show almost linear dependence on the number of
adsorbate-metal bonds, and lie in the ranges of 5.31eV to 8.58eV for C and
2.89eV to 5.40eV for S. A strong hybridization between adsorbate and surface
electronic states causes a large splitting of the bands leading to a drastic
decrease in the local densities of electronic states at the Fermi-level for Pd
surface atoms neighboring the adsorbate which may poison catalytic activity of
the surface. Comparison of the results for Pd(533) with those obtained earlier
for Pd(211) suggests the local character of the impact of the adsorbate on the
geometric and electronic structures of Pd surfaces.Comment: 14 pages 9 figs, Accepted J. Phys: Conden
Modeling the magnetostriction effect in elastomers with magnetically soft and hard particles
We analyze theoretically the field-induced microstructural deformations in a hybrid elastomer, that consists of a polymer matrix filled with a mixture of magnetically soft and magnetically hard spherical microparticles. These composites were introduced recently in order to obtain a material that allows the tuning of its properties by both, magnetically active and passive control. Our theoretical analysis puts forward two complementary models: a continuum magnetomechanical model and a bead-spring computer simulation model. We use both approaches to describe qualitatively the microstructural response of such elastomers to applied external fields, showing that the combination of magnetically soft and hard particles may lead to an unusual magnetostriction effect: either an elongation or a shrinking in the direction of the applied field depending on its magnitude. This behavior is observed for conditions (moderate particle densities, fields and deformations) under which the approximations of our models (linear response regime, negligible mutual magnetization between magnetically soft particles) are physically valid. © The Royal Society of Chemistry.Deutsche Forschungsgemeinschaft, DFG: OD 18/24-1Russian Foundation for Basic Research, RFBR: 19-52-12028, 19-52-12045, 17-41-590160Government Council on Grants, Russian FederationP. A. S. and S. S. K. acknowledge support by the DFG grant OD 18/24-1, by the Act 211 of the Government of the Russian Federation, contract No. 02.A03.21.0006, and by the FWF START-Projekt Y 627-N27. S. S. K. also acknowledges RFBR Grant 19-52-12028. O. V. S. and Yu. L. R. acknowledge support by RFBR projects 17-41-590160 and 19-52-12045, respectively. Computer simulations were carried out at the Vienna Scientific Cluster
On the origin of the C induced reconstruction of Ni(001)
First principles calculations of the geometric and electronic structures have
been performed for two coverages (0.25 ML and 0.5 ML) of C on Ni(001) to
understand the mechanism of the Ni(001) reconstruction induced by carbon
adsorption. The calculated structural behavior of the system is in a good
agreement with experimental observations. The calculated path and energetics of
the -- reconstruction in C/Ni(001) is provided. A
dramatic reduction of the local electronic charge on adsorbed carbon is found
to occur upon the reconstruction that decreases the electron-electron repulsion
on C site. This effect together with the formation of covalent bonds between C
and the second layer Ni atoms, leads to reconstruction of Ni(001).Comment: 11 pages, 7 fugure
Magnetostriction in elastomers with mixtures of magnetically hard and soft microparticles: effects of non-linear magnetization and matrix rigidity
In this contribution a magnetoactive elastomer (MAE) of mixed content, i.e.,
a polymer matrix filled with a mixture of magnetically soft and magnetically
hard spherical particles, is considered. The object we focus at is an
elementary unit of this composite, for which we take a set consisting of a
permanent spherical micromagnet surrounded by an elastomer layer filled with
magnetically soft microparticles. We present a comparative treatment of this
unit from two essentially different viewpoints. The first one is a
coarse-grained molecular dynamics simulation model, which presents the
composite as a bead-spring assembly and is able to deliver information of all
the microstructural changes of the assembly. The second approach is entirely
based on the continuum magnetomechanical description of the system, whose
direct yield is the macroscopic field-induced response of the MAE to external
field, as this model ignores all the microstructural details of the
magnetization process. We find that, differing in certain details, both
frameworks are coherent in predicting that a unit comprising magnetically soft
and hard particles may display a non-trivial re-entrant
(prolate/oblate/prolate) axial deformation under variation of the applied field
strength.
The flexibility of the proposed combination of the two complementary
frameworks enables us to look deeper into the manifestation of the magnetic
response: with respect to the magnetically soft particles, we compare the
linear regime of magnetization to that with saturation, which we describe by
the Fr\"{o}hlich-Kennelly approximation; with respect to the polymer matrix, we
analyze the dependence of the re-rentrant deformation on its rigidity
High CO tolerance of Pt/Ru nano-catalyst: insight from first principles calculation
Density functional theory based calculations of the energetics of adsorption
and diffusion of CO on Pt islets and on the Ru(0001) substrate show that CO has
the lowest adsorption energy at the center of the islet, and its bonding
increases as it moves to the edge of the island and further onto the substrate.
Activation energy barriers for CO diffusion from the islet to the Ru surface
are found to be lower than 0.3 eV making the process feasible and leading to
the conclusion that this hydrogen oxidation catalyst is CO tolerant because of
the spillover of CO from active Pt sites to the Ru substrate. We present the
rationale for this effect using insights from detailed electronic structure
calculations.Comment: 6 pages, 5 figure
- …