Pressure induced dimerisation of C-70

Solid C-70 has been subjected simultaneously to high pressures and temperatures (HPHT), with pressures upto 7.5 GPa and temperatures upto 750 degrees C. X-ray diffraction measurements on the recovered samples indicate that the initial h.c.p. solid C-70 transforms to a rhombohedral structure which recovers to an f.c.c. structure on annealing. The associated changes in the intra molecular vibrational modes have been probed through infrared: (IR) and Raman measurements. The IR measurements on these HPHT samples; show splitting of some of the pristine modes and occurrence of several new modes These sharp IR modes in the HPHT treated samples, which are seen to-be different from that reported for photopolymerised C-70, have been attributed to the formation of C-70 dimers. (C) 1997 Published by Elsevier Science Ltd.