100 research outputs found
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
Ab initio prediction of Boron compounds arising from Borozene: Structural and electronic properties
Structure and electronic properties of two unusual boron clusters obtained by
fusion of borozene rings has been studied by means of first principles
calculations, based on the generalized-gradient approximation of the density
functional theory, and the semiempirical tight-binding method was used for the
transport calculations. The role of disorder has also been considered with
single vacancies and substitutional atoms. Results show that the pure boron
clusters are topologically planar and characterized by (3c-2e) bonds, which can
explain, together with the aromaticity (estimated by means of NICS), the
remarkable cohesive energy values obtained. Such feature makes these systems
competitive with the most stable boron clusters to date. On the contrary, the
introduction of impurities compromises stability and planarity in both cases.
The energy gap values indicate that these clusters possess a semiconducting
character, while when the larger system is considered, zero-values of the
density of states are found exclusively within the HOMO-LUMO gap. Electron
transport calculations within the Landauer formalism confirm these indications,
showing semiconductor-like low bias differential conductance for these
stuctures. Differences and similarities with Carbon clusters are highlighted in
the discussion.Comment: 10 pages, 2 tables, 5 figure
Combustion of Methane over Palladium-Based Catalysts: Catalytic Deactivation and Role of the Support
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