THEORY–EXPERIMENT RELATIONSHIP OF THE "SHRINKING HOT GIANT" ROAD OF DYNAMIC FULLERENE SELF-ASSEMBLY IN HOT CARBON VAPOR

Abstract

Though subject to intensive studies, the formation mechanism of buckminsterfullerene C 60 and related higher fullerenes has long evaded discovery. To elucidate their atomistic self-assembly mechanism, we have performed high-temperature quantum chemical molecular dynamics simulations on carbon vapor model systems initially consisting of C 2 molecules. Our simulations reveal a coherent mechanism how highly ordered fullerene cages naturally self-assemble under nonequilibrium conditions, following a series of irreversible processes from the polymerization of C 2 molecules to vibrationally excited giant fullerenes, which then shrink by C 2 evaporation down to the smallest spherical, isolated pentagon rule obeying species C 70 and C 60 as the smallest and kinetically most stable species of the shrinking process. We show that the potential energy surface associated with giant fullerene cage growth, measured by an average cluster curvature, is downhill all the way, and in agreement with high-level energetics from density functional theory. This fullerene formation mechanism is a good example of dynamic self-assembly leading to dissipative structures far from thermodynamic equilibrium, and the "shrinking hot giant" road provides a natural explanation for the observed cage size distributions in a random optimization process consistent with several important experimental observations.