Crystal shape of a nickel particle related to carbon nanotube growth

In order to investigate the relevance of the equilibrium crystal shape of a nickel particle during carbon nanotube growth, we have performed self-consistent pseudopotential density-functional calculations. The nickel particle's equilibrium shape is obtained front the Wulff construction using the calculated surface energies. TO understand the role of facets of the nickel particle, we investigate the adsorption and diffusion of the carbon atom on the nickel surfaces. The desorption energy of the carbon atom and the activation energy for carbon diffusion are found to be very different on different low-index facets, thus diffusion behaviors will also differ. It is found that the {111} and {110} facets are likely to tic more reactive compared to the 1001 facet. Therefore, the facets of the nickel particle will play an important role in carbon nanotube growth.