QM(DPT) and MD studies on formation mechanisms of C-60 fullerenes

One of the most puzzling aspects of fullerenes is how such complicated symm etric molecules are formed from a gas of atomic carbons, namely, the atomis tic or chemical mechanisms. Are the atoms added one by one or as molecules (C-2, C-3)? Is there a critical nucleus beyond which formation proceeds at gas kinetic rates? What determines the balance between forming buckyballs, buckytubes, graphite and soot? The answer to these questions is extremely i mportant in manipulating the systems to achieve particular products. A diff iculty in current experiments is that the products can only be detected on time scales of microseconds long after many of the important formation step s have been completed. Consequently, it is necessary to use simulations, qu antum mechanics and molecular dynamics, to determine these initial states. Experiments serve to provide the boundary conditions that severely limit th e possibilities. Using quantum mechanical methods (density functional theor y (DFT)) we derived a force field (MSXX FF) to describe one-dimensional (ri ngs) and two-dimensional (fullerene) carbon molecules. Combining DFT with t he MSXX FF,we calculated the energetics for the ring fusion spiral zipper ( RFSZ) mechanism for formation of C-60 fullerenes. Our results shows that th e RFSZ mechanism is consistent with the quantum mechanics (with a slight mo dification for some of the intermediates).