INVESTIGATION OF HIGH-PRESSURE INDUCED ORIENTATIONAL PHASE-TRANSITIONIN C-60 SINGLE-CRYSTAL

By using a piston-cylinder type hydrostatic high pressure unit, the el ectrical de conductance of bulk C-60 Single crystal was measured in th e pressure range of 0 to 0.8 GPa at different temperatures. With incre asing pressure, a discontinuous increase of the conductance was observ ed, which can be ascribed to the orientational ordering phase transiti on. The slope of the phase line corresponding to the orientational ord ering transition in the P-T phase diagram is determined to be dT/dP(c) = 150 K/GPa. At elevated temperatures, the slopes of the conductance versus pressure give an anomalous discontinuous change before the orie ntational ordering transition.