Shock compressibility and shock-induced phase transitions of C60 fullerite

Shock compressibility of C60 fullerite and sound velocities in shock-compressed fullerite were experimentally studied at the pressures range up to ∼50 GPa. In our experiments, we used polycrystalline C60 specimens with a density of 1.64 g/cc. The Hugoniot of C60 fullerite had a set of peculiarities, which may be attributed to a series of polymorphic phase transitions. The jump of sound velocity in shocked C60 at pressure ∼9 GPa indicates the formation of a rather hard carbon phase. It is possible to assume that it is a polymerized C60 phase. In the region of pressures 9–25 GPa, destruction of this phase and formation of a graphite-like carbon occurs. With further growth of shock pressure, phase transition of the graphite-like carbon to a diamond-like phase is observed with a transition onset pressure ∼25 GPa. If shock pressures are higher than ∼33 GPa, Hugoniot of C60 fullerite is determined by the thermodynamic properties of the diamond-like phase.