4,616 research outputs found
The AFP Project
AFP is a project to extend the diffractive physics programme of the ATLAS
experiment by installing new detectors that will be able to tag forward protons
scattered at very small angles. This will allow us to study Single Diffraction,
Double Pomeron Exchange, Central Exclusive Production and photon-photon
processes. This note presents the physics case for the AFP project and briefly
describes the proposed detector system.Comment: 10 pages, 8 figures, presented at the Cracow Epiphany Conference on
the first year of the LHC, Cracow, Poland, January 10--12, 201
A density functional study of the structure of tethered chains in a binary mixture
A density functional study of the structure of a layer formed by chain
molecules pinned to a solid surface is presented. The chains are modeled as
freely joined spheres. Segments and all components interact via Lennard-Jones
(12-6) potential. The interactions of fluid molecules with the wall are
described by the Lennard-Jones (9-3) potential. We analyze how different
parameters of the model affect the dependence of the brush height upon the
mixture composition. We consider the effect of grafting density and the
parameters characterizing the interactions of fluid molecules with the
substrate and with the chains as well as interactions within the mixture. The
changes in the brush height correlate with the adsorption of particular
components.Comment: 12 pages, 8 figure
Ordering and order-disorder phase transition in the (1x1) monolayer chemisorbed on the (111) face of an fcc crystal
In this paper we have considered a simple lattice gas model of chemisorbed
monolayer which allows for the harmonic fluctuations of the bond length between
the adsorbate atom and the surface site. The model also involves a short-ranged
attractive potential acting between the adsorbed atoms as well as the surface
periodic corrugation potential. It has been assumed that the adsorbed atoms are
bonded to the uppermost layer of the substrate atoms. In particular, using
Monte Carlo simulation method we have focused on the orderings appearing in the
dense monolayer formed on the (111) face of an fcc solid. Within the lattice
gas limit, the chemisorbed layer forms a (1x1) structure. On the other hand,
when the bonds are allowed to fluctuate, three other different ordered phases
have been found to be stable in the ground state. One of them has been found to
be stable at finite temperatures and to undergo a phase transition to the
disordered state. The remaining two ordered states have been found to be stable
in the ground state only. At finite temperatures, the ordering has been
demonstrated to be destroyed due to large entropic effects.Comment: 15 pages, 15 figure
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