Nonmonotonic variation of the electrical conductivity of C60 fullerene crystals dynamically compressed to 300 kbar as evidence of anomalously strong reduction of the energy barrier of C60 polymerization at high pressures

The electrical conductivity of a C₆₀ fullerene crystal is measured under the conditions of quasi-isentropic loading by a diffuse shock wave to a pressure of 30 GPa at room temperature. Nonmonotonic behavior of the conductivity of the samples with an increase in pressure is observed: first, conductivity increases by several orders of magnitude and, then, decreases rapidly. An increase in conductivity is explained by a decrease in the band gap under pressure, whereas a decrease in conductivity may be explained under the assumption that the energy barrier of C₆₀ polymerization decreases similarly to the band gap with an increase in pressure. As a result, the rate of C₆₀ polymerization at high pressures increases considerably (by more than seven orders of magnitude).