Web Release Date: February 19,
Electronic Properties of Adsorption Nitrogen Monoxide on Inside and Outside of the Armchair Single Wall Carbon Nanotubes: A Density Functional Theory Calculations
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Faculty of Chemistry, Bu-Ali Sina University, Hamedan, Iran, and College of Chemistry, Iran University of Science and Technology, Tehran, Iran
Received: October 12, 2007
In Final Form: December 12, 2007
Abstract:
Density functional theory (DFT) was used to study the adsorption of nitrogen monoxide (NO) on the armchair (4, 4), (5, 5), (6, 6), and (7, 7) carbon nanotubes. The effect of molecular orientation on the adsorption process was also studied. Both the external (two modes, N-down and O-down; NO molecular axis perpendicular to the C atoms of the nanotubes) and internal (one mode, NO molecular axis perpendicular to the z axis of a nanotube) adsorption orientations were studied. The adsorption energies, equilibrium distances, highest-occupied molecular orbital-lowest-unoccupied molecular orbital energy gap, and partial charges of the C atoms were also found. The global indices were calculated using the Kopmann's theorem. Computational results show that NO molecules are physisorbed on both sites (external and internal) of the nanotubes; for the O-down mode, the NO molecules were strongly physisorbed. Stability of tube-molecule for the adsorption of NO molecules on the outer wall of a nanotube decreases as the tube diameter increases. In contrast, NO penetration into a nanotube increases as the tube diameter increases. The results show that NO molecules cannot be adsorbed on the inner walls of the nanotubes with diameters lower than 5.38 Å. Finally, physisorption of the NO molecules via the oxygen head (the O-down mode) was stronger than the other adsorption mode.
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