Shock compression and equation of state of C$_{60}$ fullerite

Recently, we have experimentally studied shock compressibility of C$_{60}$ fullerite and sound velocity in shock-compressed fullerite [1]. The Hugoniot of C$_{60}$ fullerite had a set of peculiarities. Appearance of a rather hard carbon phase was detected at shock pressure $\sim$ 9 GPa. We assume that it is a 2D-polymerized C$_{60}$ phase. With increase of shock pressure, destruction of this phase and formation of a graphite-like carbon occurs. With further increase of shock pressure, the graphite- like carbon transforms to a diamond-like phase. If shock pressure is higher than $\sim$ 33 GPa, shock compressibility of C$_{60}$ fullerite is determined by the thermodynamic properties of the diamond-like phase. The results of the shock-wave measurements were used for the description of thermodynamic properties of C$_{60}$ fullerite and products of its transformations in a wide range of pressures and temperatures. A semiempirical equation of state for the simple cubic phase of C$_{60}$ fullerite is proposed. The EOS we have developed for fullerite C$_{60}$ provides a consistent representation of the available experimental data. The work was supported by RFBR. [1] Milyavskiy V.V., Utkin A.V., Zhuk A.Z., Yakushev V.V. and Fortov V.E. Diamond and Rel. Mat. 14 (2005) 1920.