Electroconductivity and pressure-temperature states of step shocked C60 fullerite

A study of electrophysical and thermodynamic properties of C-60 single crystals under step shock loading has been carried out. The increase and the following reduction in specific electroconductivity of C-60 fullerite single crystals at step shock compression up to pressure 30 GPa have been measured. The equations of state for face centred cubic (fcc) C-60 fullerite as well as for two-dimensional polymer C-60 and for three-dimensional polymer C-60 (3D-C-60) were constructed. The pressure-temperature states of C-60 fullerite were calculated at step shock compression up to pressure 30 GPa and temperature 550 K. The X-ray diffraction studies of shock-recovered samples reveal a mixture of fcc C-60 and a X-ray amorphous component of fullerite C-60. The start of the formation of the X-ray amorphous component occurs at a pressure P-m approximate to 19.8 GPa and a temperature T-m approximate to 520 K. At pressures exceeding P-m and temperatures exceeding T-m, the shock compressed fullerite consist of a two-phase mixture of fcc C-60 fullerite and an X-ray amorphous component presumably consisting of the nucleators of polymer 3D-C-60 fullerite. The decrease in electroconductivity of fullerite can be explained by the percolation effect caused by the change of pressure, size and number of polymeric phase nuclei.