On the phase-transition in anthracene induced by high pressure

The crystallographic structure of anthracene is studied under high pressure up to 27 GPa using diamond anvil cells. Different pressure-transmitting media (helium, a methanol–ethanol mixture, a normal- and iso-pentane mixture and no medium) were used up to specific critical pressures where the hydrostatic conditions are lost. It is clearly observed that the loss of hydrostaticity is associated with a crystallographic phase-transition in anthracene. The phase-transition is observed as reversible, and it is accompanied by a large hysteresis. These observations clarify conflicting reports in the literature on the high-pressure phase-transition of anthracene.