Orientation Dependence in C60 Surface-Impact Collisions

Q.-H. Tang, K. Runge, H .-P. Cheng, and Frank E. Harris

Quantum Theory Project, University of Florida
Department of Physics, University of Utah

J. Phys. Chem A 106, 893-896 (2002)

   The effect of molecular orientation on collisions between C60 (buckminsterfullerene) and a solid surface was studied by carrying out simulations based on the Tersoff potential for the C---C interaction and modeling the surface by a structureless wall.  Simulations were run with initial molecular kinetic energies of 100 eV and 300 eV, at impact angles relative to normal incidence of 10 , 20, and 30 degrees.  The simple nature of the simulations permitted the examination of thousands of trajectories with random initial C60 orientations, in contrast to all previous studies, which have been highly limited in this respect.  The data obtained included information about the redistribution of energy and angular momentum and about collisional fragmentation.    The results are strongly dependent upon the initial molecular orientation, and lead to wide distributions of the quantities studied.  Since structured surfaces are expected to intensify the orientation  dependence, it is concluded that one must use a substantial ensemble of trajectories to obtain meaningful average behavior.  The ensemble averages are qualitatively similar to relevant experimental results and thereby support the conclusions advanced.