159 research outputs found
Fullerenes with distant pentagons
For each , we find all the smallest fullerenes for which the least
distance between two pentagons is . We also show that for each there is
an such that fullerenes with pentagons at least distance apart and
any number of hexagons greater than or equal to exist.
We also determine the number of fullerenes where the minimum distance between
any two pentagons is at least , for , up to 400 vertices.Comment: 15 pages, submitted for publication. arXiv admin note: text overlap
with arXiv:1501.0268
Recursive generation of IPR fullerenes
We describe a new construction algorithm for the recursive generation of all
non-isomorphic IPR fullerenes. Unlike previous algorithms, the new algorithm
stays entirely within the class of IPR fullerenes, that is: every IPR fullerene
is constructed by expanding a smaller IPR fullerene unless it belongs to
limited class of irreducible IPR fullerenes that can easily be made separately.
The class of irreducible IPR fullerenes consists of 36 fullerenes with up to
112 vertices and 4 infinite families of nanotube fullerenes. Our implementation
of this algorithm is faster than other generators for IPR fullerenes and we
used it to compute all IPR fullerenes up to 400 vertices.Comment: 19 pages; to appear in Journal of Mathematical Chemistr
Decay and fusion as two different mechanisms of stability loss for the (C_20)_2 cluster dimer
The thermal stability of the (C_20)_2 cluster dimer consisting of two C_20
fullerenes is examined using a tight-binding approach. Molecular dynamics
simulations of the (C_20)_2 dimer at temperatures T = 2000 - 3500 K show that
the finite lifetime \tau of this metastable system is determined by two
fundamentally different processes, the decay of one of the C_20 fullerenes and
the fusion of two C_20 fullerenes into the C_40 cluster. The activation
energies for these processes Ea = 3.4 and 2.7 eV, respectively, as well as
their frequency factors, have been determined by analyzing the dependence of
\tau on T.Comment: Slightly modified version of the paper to appear in JETP Let
Boron Fullerenes: A First-Principles Study
A family of unusually stable boron cages was identified and examined using
first-principles local density functional method. The structure of the
fullerenes is similar to that of the B12 icosahedron and consists of six
crossing double-rings. The energetically most stable fullerene is made up of
180 boron atoms. A connection between the fullerene family and its precursors,
boron sheets, is made. We show that the most stable boron sheets are not
necessarily precursors of very stable boron cages. Our finding is a step
forward in the understanding of the structure of the recently produced boron
nanotubes.Comment: 10 pages, 4 figures, 1 tabl
Numerical simulation of the thermal fragmentation process in fullerene C60
The processes of defect formation and annealing in fullerene C60 at
T=(4000-6000)K are studied by the molecular dynamics technique with a
tight-binding potential. The cluster lifetime until fragmentation due to the
loss of a C2 dimer has been calculated as a function of temperature. The
activation energy and the frequency factor in the Arrhenius equation for the
fragmentation rate have been found to be Ea = (9.2 +- 0.4) eV and A = (8 +-
1)10^{19} 1/s. It is shown that fragmentation can occur after the C60 cluster
loses its spherical shape. This fact must be taken into account in theoretical
calculations of Ea.Comment: 12 pages, 3 figure
Atomistic potential for graphene and other sp carbon systems
We introduce a torsional force field for sp carbon to augment an in-plane
atomistic potential of a previous work (Kalosakas et al, J. Appl. Phys. {\bf
113}, 134307 (2013)) so that it is applicable to out-of-plane deformations of
graphene and related carbon materials. The introduced force field is fit to
reproduce DFT calculation data of appropriately chosen structures. The aim is
to create a force field that is as simple as possible so it can be efficient
for large scale atomistic simulations of various sp carbon structures
without significant loss of accuracy. We show that the complete proposed
potential reproduces characteristic properties of fullerenes and carbon
nanotubes. In addition, it reproduces very accurately the out-of-plane ZA and
ZO modes of graphene's phonon dispersion as well as all phonons with
frequencies up to 1000~cm.Comment: 9 pages, 6 figure
Topological Anisotropy of Stone-Wales Waves in Graphenic Fragments
Stone-Wales operators interchange four adjacent hexagons with two pentagon-heptagon 5|7 pairs that, graphically, may be iteratively propagated in the graphene layer, originating a new interesting structural defect called here Stone-Wales wave. By minimization, the Wiener index topological invariant evidences a marked anisotropy of the Stone-Wales defects that, topologically, are in fact preferably generated and propagated along the diagonal of the graphenic fragments, including carbon nanotubes and graphene nanoribbons. This peculiar edge-effect is shown in this paper having a predominant topological origin, leaving to future experimental investigations the task of verifying the occurrence in nature of wave-like defects similar to the ones proposed here. Graph-theoretical tools used in this paper for the generation and the propagation of the Stone-Wales defects waves are applicable to investigate isomeric modifications of chemical structures with various dimensionality like fullerenes, nanotubes, graphenic layers, schwarzites, zeolites
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