First-principles study on effects of mechanical deformation on outer surface reactivity of carbon nanotubes

The first-principles approach of Car-Parrinello molecular dynamics is used to study the chemisorption of a single oxygen atom on the outer surface of zigzag single-wall carbon nanotubes (SWCNT) under various axial strains and bending deformation. The effect of mechanical deformation on adsorption of oxygen atom on carbon nanotubes (CNTs) is demonstrated by linking the chemical reactivity and structural deformation. The adsorption energy E-b and pyramidalization angle theta(p) are obtained by structural relaxation calculations, and ground-state electronic structures are described according to the density functional theory (DFT) within a plane-wave pseudopotential framework. Our results show that the surface reactivity of CNT is mostly determined by its pyramidalization angle of carbon atom. For bending SWCNT, both E-b and theta(p) vary with adsorption sites, E-b is higher at sites with a larger pyramidalization angle. An approximate linear relation of strain and adsorption energy can be obtained. It is indicated that the structure of CNT is crucial for its surface reactivity, and the mechanical deformation can be used to control the surface reactivity of CNT and offer adsorption site selectivity as the adsorption is facilitated on the sites with higher pyramidalization angles. (C) 2008 Elsevier B.V. All rights reserved.