5 research outputs found
Water diffusion in carbon nanotubes for rigid and flexible models
We compared the diffusion of water confined in armchair and zigzag carbon
nanotubes for rigid and flexible water models. Using one rigid model,
TIP4P/2005, and two flexible models, SPC/Fw and SPC/FH, we found that the
number of the number of hydrogen bonds that water forms depends on the
structure of the nanotube, directly affecting the diffusion of water. The
simulation results reveal that due to the hydrophobic nature of carbon
nanotubes and the degrees of freedom imposed by the water force fields, water
molecules tend to avoid the surface of the carbon nanotube. This junction of
variables plays a central role in the diffusion of water, mainly in narrow
and/or deformed nanotubes, governing the mobility of confined water in a
non-trivial way, where the greater the degree of freedom of the water force
field, the smaller it will be mobility in confinement, as we limit the
competition between area/volume, and it no longer plays the unique role in
changing water diffusivity.Comment: 28 pages, 6 figure
Dióxido de Carbono: um estudo sobre o modelo de simulação computacional EPM2
Neste trabalho utilizamos o modelo de simulação EPM2 para descrever as interações do CO2 como podemos ver nos artigos de IKUSHIMA; SAITO e ARAI (1992), MURTHY; SINGER e MCDONALD (1981), GEIGER; LADANYI e CHAPIN (1990), MERKER et al. (2010) e ZHANG e DUAN (2005). Nosso objetivo, posteriormente, é investigar o comportamento do CO2 e compreender quais
modelos conseguem capturar corretamente as interações do bulk e em condições de extremo confinamento
Transport Properties of Hydrogenated Cubic Boron Nitride Nanofilms with Gold Electrodes from Density Functional Theory
The electrical transport properties of a fourlayered
hydrogen-terminated cubic boron nitride sub-nanometer
film in contact with gold electrodes are investigated via
density functional calculations. The sample exhibits asymmetric
metallic surfaces, a fundamental feature that triggers the system
to behave like a typical p?n junction diode for voltage bias in
the interval ?0.2 ? V ? 0.2, where a rectification ratio up to 62
is verified. Further, in the wider region ?0.3 ? V ? 0.3,
negative differential resistance with a peak-to-valley ratio of 10
is observed. The qualitative behavior of the I?V characteristics
is described in terms of the hydrogenated cBN film equilibrium electronic structure. Such a film shows metallic surfaces due to
surface electronic states at a fraction of eV above and below the Fermi level of the N?H terminated and B?H terminated
surfaces, respectively, with a wide bulk-band gap characteristic of BN materials. Such a mechanism is supported by transmission
coefficient calculations, with the Landauer?Bu?ttiker formula governing the I?V characteristics