COMPARATIVE INVESTIGATION OF ELASTIC DIFFUSE-SCATTERING IN C-60 POWDERS

C-60 powder samples of varying impurity content have been investigated by neutron scattering techniques. For Q > 2.5 Angstrom(-1) considerab le elastic diffuse scattering is found below T-c providing evidence of static disorder in the low-temperature phase. The elastic scattering increases on cooling from T-c to 150 K but remains virtually constant below this temperature. There is no marked dependence on the impurity level. For Q < 2.5 Angstrom(-1) elastic diffuse scattering obeying a [ sin(QR)/(QR)](2) law is observed both above and below the phase transi tion (R is the radius of the C-60 molecule). This scattering is nearly independent of temperature, however, it depends strongly on the amoun t of impurities in the sample. Model calculations have been performed which relate varying degrees of orientational disorder in C-60 to the elastic scattering observed in powder samples.