Diffuse X-ray scattering on molecular crystals
Richard Schubert, diploma work, 84 pages, 51 figures, University of Bayreuth / Germany, Oct. 1987


The diffuse X-ray scattering of 2,3-dimethyl-naphtalene has been measured in all three scattering planes. Overview measurements show two distinct kinds of diffuse scattering. First, there is a diffuse scattering which is observed over wide areas of the reciprocal lattice. It is caused by the practically statistical orientation of the molecules in the lattice (up/down). Comparing the measurement results with many calculated scattering diagrams an average statistical tilt of the molecules could be derived. The second kind of diffuse scattering is concentrated near the Bragg peaks. Analyzing these areas, it was possible to derive first values of the scale length of local lattice distortions. These local lattice distortions are caused by the statistical orientation of the molecules. X-ray measurements do not allow to determine, whether the scattering is elastic or inelastic. Elastic scattering is linked to static distortions, inelastic scattering to dynamic distortions (phonons). Comparing the results with diffuse-elastic neutron scattering measurements, which have been performed by another collaborator of the institute, the static nature of the lattice distortions could be verified. Thus, an essential assumption of the used model could be confirmed.

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(or in small pieces: Contents, Chap. 1, Chap. 2, Chap. 3, Chap. 4, References)


last modified May/26./03/01