A HIGH-PRESSURE INVESTIGATION OF C-60 BY DIFFUSE NEUTRON-SCATTERING

Results of a diffuse neutron scattering experiment on C-60 powder unde r pressure are presented. A sapphire anvil pressure cell was used and pressures up to 1.6 GPa were applied. The results confirm that an orie ntational order-disorder transition occurs at room temperature under h igh pressure. The data indicate a 70% occupancy of the 38 degrees orie ntational variant in C-60 under high pressure. The presence of elastic diffuse scattering shows that static orientational disorder persists at least up to 1.3 GPa which is the highest pressure up to which the d iffuse scattering was investigated. The compressibility at room temper ature was determined to be 5.4 x 10(-2) GPa(-1) in agreement with resu lts of Duclos et al.