A molecular dynamics simulation study of diffuse x-ray scattering from Câ†1â†0Hâ†1â†6
Adamantane C10H16 is an interesting archetypal plastic crystal which has been extensively studied. It undergoes transition from a low temperature ordered phase to a high temperature disordered phase at T=208.6K. The C10H16 molecule has tetrahedral symmetry and the orientational disorder to the plastic phase has been interpreted in terms of the distribution of the molecules between two equally preferred orientations. A molecular dynamics simulation of C10H16 has been carried out using the CCP5 Library program moliq-dynamo, written by Dr. D Fincham of Keele University. The simulation model consists of rigid molecules interacting with an atom-atom pairwise additive potential. The dynamics of the adamantane molecules in the plastic phase have been investigated and results have been compared with previous work. The molecular trajectories generated by the simulation have been used to evaluate the intensity of diffuse x-ray scattering from the crystal. Results have been compared with experimental data obtained from energy-dispersive x-ray scattering measurements made at the Daresbury SRS. Using a series of simplified models of the crystal, the relative contributions to the scattered intensity from translational and orientational disorder have been investigated.