Seminário "Alkali Halide Nanotubes: Structure, Stability and Mechanism of Formation"
Na sexta-feira, 22/02/2013, teremos o seminário intitulado "Alkali Halide Nanotubes: Structure, Stability and Mechanism of Formation", a ser ministrado pelo Prof. Marco Antonio Chaer do Nascimento, do Instituto de Química-UFRJ. O evento ocorrerá no Auditório do PPGFIS às 15 H.
Segue o resumo:
ALKALI HALIDE NANOTUBES: STRUCTURE, STABILITY AND
MECHANISM OF FORMATION
Aline Veronica Henkes, Felipe Fantuzzi and Marco Antonio Chaer Nascimento
Instituto de Quimica
Universidade Federal do Rio de Janeiro, Brazil
chaer01 [at] gmail.com
ABSTRACT
Results of accurate quantum-mechanical calculations for alkali halide nanotubes (LiF,
NaCl, KBr) will be presented. The relative stability of the nanotubes (MX)n=3-60 was
studied at the DFT/B3LYP/LAVCV3P** level of theory. Coupled Cluster CCSD/SDD
and Moeller-Plesset (MP2) calculations were also performed in order to verify possible
inconsistencies of the DFT results for the smaller tubes (MX)n=3-10. Conjugated
nanotubes were also investigated at the B3LYP/ LAVCV3P** level of calculations and
the results obtained for (LiF)n n£ 48 indicate the stability of these species.
Quantum dynamical calculations (NVT ensemble, at T=25oC and 1 atm) at the
DFT/B3LYP/6-31G level of theory were performed for the (LiF)28 nanotube with
octagonal cross section in order to verify its thermal stability. The results indicate that
these species should be stable at room temperature and prompted us to study their
mechanism of formation.
The number of possible reaction paths for the formation of these nanotubes is very large
and only a few of them will be considered in this presentation. Starting from the basic
LiF units, quantum dynamics calculations (NVT, 1 atm and 25oC, DFT/B3LYP/6-
31G**) indicate that small ring structures will be formed preferentially to the cubic-like
and that up to (LiF) the nanotubes with octagonal cross-section are more stable than the
typical cubic structures for this class of compounds. As the size of the tubes increase,
they become less stable than the corresponding cubic ones. However, since the
formation of the nanotubes is kinetically controlled and the barriers of interconversion
from the tubes to the corresponding cubic structures are apparently large, the
calculations predict that the tube-like structures should be stable enough to allow for
their isolation and characterization. The authors acknowledge financial support from
CNPq, FAPERJ and INOMAT.
