Coulomb Stability Limit of Highly Charged ${\mathrm{C}}_{60}^{q+}$ Fullerenes

We perform density functional theory calculations of ${\mathrm{C}}_{60}^{q+}$ and ${\mathrm{C}}_{58}^{q+}$ fullerenes as well as of transition states related to dissociation of ${\mathrm{C}}_{60}^{q+}$ into ${\mathrm{C}}_{58}^{(q-s)+}$ and ${\mathrm{C}}_2^{s+}$ for charges $q=0–14$. For $q\le 8$, the lowest fission barrier corresponds to ${\mathrm{C}}_2^{+}$ emission, whereas, for higher $q$ values, the lowest barrier corresponds to the emission of two atomic fragments $[2\mathrm{C}{]}^{s+}$ with $s\ge 2$. We conclude that the Coulomb stability limit corresponds to $q=14$.

Figure 1

Schematic representation of the relevant energy differences between ${\mathrm{C}}_{60}^{q+}$ and the various dissociation channels.

Figure 2

Dissociation energies for the reactions ${\mathrm{C}}_{60}^{q+}\to {\mathrm{C}}_{58}^{(q-s)+}+{\mathrm{C}}_2^{s+}$ and ${\mathrm{C}}_{60}^{q+}\to {\mathrm{C}}_{58}^{(q-s)+}+[2\mathrm{C}{]}^{s+}$. The inset shows the results for $s=0$ in an expanded scale.

Figure 3

TSs for the dissociation processes ${\mathrm{C}}_{60}^{8+}\to {\mathrm{C}}_{58}^{(8-s)+}+{\mathrm{C}}_2^{s+}$ and ${\mathrm{C}}_{60}^{9+}\to {\mathrm{C}}_{58}^{(9-s)+}+[2\mathrm{C}{]}^{s+}$.

Figure 4

Kinetic energy of ${\mathrm{C}}_2^{+}$ fragments emitted from ${\mathrm{C}}_{60}^{q+}$. Present results: circles connected by a full line. Experimental results are connected by dashed lines: diamonds [5], triangles [7], and inverted triangles [6].