Reactivities of C60 and C70

We study the reactivities Of I-h C-60 and D-5h C-70 fullerenes in the framework of the density-functional theory. To quantify the reactivities of fullerenes, we calculate the total energies of the system consisting of a fullerene and a C atom as a function of the distance from each C site on the fullerene surface to the C atom, and obtain the reaction energy defined as energy gain at the minimum-energy configuration from the infinite distance configuration. Surprisingly, it is found that some of the C-70 sites have larger reaction energies than that of C-60, although C-70 is energetically more stable than C-60. This result sheds new light on the formation process of fullerenes and the abundance of C-60 in soot. (c) 2007 Elsevier B.V. All rights reserved.