Damaging fullerene ${\mathrm{C}}_{60}$ upon energetic irradiation has been modeled with molecular-dynamics simulations. The angular dependence of the threshold energy of the primary knock-on atom (PKA) escaping from the cage is investigated in the case of the initial PKA direction within a plane through the cage center and 6-6 ring fusions. The average threshold value is estimated to be about 29 eV. The simulations provided a detailed picture of the damaging processes, in which three mechanisms were revealed. Those included ${\mathrm{C}}_{60}$-C→${\mathrm{C}}_{59}$, ${\mathrm{C}}_{60}$→C${\mathit{C}}_{59}$, and ${\mathrm{C}}_{60}$-2C→${\mathrm{C}}_{58}$. The interactions between carbon atoms are described with the Tersoff mode modified to match a screened Coulomb potential at short range.

• Received 21 October 1993

DOI:https://doi.org/10.1103/PhysRevB.49.9962