4,035 research outputs found
Interface Characteristics at an Organic/Metal Junction: Pentacene on Cu Stepped Surfaces
The adsorption of pentacene on Cu(221), Cu(511) and Cu(911) is investigated
using density functional theory (DFT) with the self-consistent inclusion of van
der Waals (vdW) interactions. Cu(211) is a vicinal of Cu(111) while Cu(511) and
(911) are vicinals of Cu(100). For all the three surfaces, we found pentacene
to prefer to adsorb parallel to the surface and near the steps. The addition of
vdW interactions resulted in an enhancement in adsorption energies, with
reference to the PBE functional, of around 2 eV. With vdWs inclusion, the
adsorption energies were found to be 2.98 eV, 3.20 eV and 3.49 eV for Cu(211),
Cu(511) and Cu(911) respectively. These values reflect that pentacene adsorbs
stronger on (100) terraces with a preference for larger terraces. The molecule
tilts upon adsorption with a small tilt angle on the (100) vicinals (about a
few degrees) as compared to a large one on Cu(221) where the tilt angle is
found to be about 20o. We find that the adsorption results in a net charge
transfer to the molecule of ~1 electron, for all surfaces.Comment: 11 pages, 4 figure
Subresultants and Generic Monomial Bases
Given n polynomials in n variables of respective degrees d_1,...,d_n, and a
set of monomials of cardinality d_1...d_n, we give an explicit
subresultant-based polynomial expression in the coefficients of the input
polynomials whose non-vanishing is a necessary and sufficient condition for
this set of monomials to be a basis of the ring of polynomials in n variables
modulo the ideal generated by the system of polynomials. This approach allows
us to clarify the algorithms for the Bezout construction of the resultant.Comment: 22 pages, uses elsart.cls. Revised version accepted for publication
in the Journal of Symbolic Computatio
Skew group algebras, invariants and Weyl Algebras
The aim of this paper is two fold:
First to study finite groups of automorphisms of the homogenized Weyl
algebra , the skew group algebra , the ring of invariants
, and the relations of these algebras with the Weyl algebra ,
with the skew group algebra , and with the ring of invariants
. Of particular interest is the case .
In the on the other hand, we consider the invariant ring \QTR{sl}{C}[X]^{G}
of the polynomial ring in generators, where is a finite subgroup
of Gl(n,\QTR{sl}{C}) such that any element in different from the identity
does not have one as an eigenvalue. We study the relations between the category
of finitely generated modules over \QTR{sl}{C}[X]^{G} and the corresponding
category over the skew group algebra \QTR{sl}{C}% [X]\ast G. We obtain a
generalization of known results for and a finite subgroup of
. In the last part of the paper we extend the results for the
polynomial algebra to the homogenized Weyl algebra
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