High-Pressure Phase Transition in Cyclo-octane

Structural behaviour of cyclo-octane under high pressure is studied by using a synchrotron x-ray source in a diamond anvil cell (DAC) up to 40.2GPa at room temperature. The cyclo-octane firstly solidifies to the triclinic phase at 0.87GPa. With the increasing pressure, the phase of cyclo-octane changes to the tetragonal phase at about 6.0GPa and then transforms to amorphous phase above 18.2GPa, which is kept till to 40.2GPa. All the phase transitions of cyclo-octane are irreversible.