Cover illustration: The hydrogen-bonded tetramer in the structure of exo-8-(trifluoromethyl)pentacyclo[5.4.0.02,6.03,10.05,9]undecan-endo-8-ol. All H atoms have been omitted for clarity. See Linden, Romanski, Mloston & Heimgartner [Acta Cryst. (2005), C61, o221-o226].
Rietveld refinement shows that the structure of Tl2SeO4 in a paraelastic phase (above 661 K) is represented as consisting of SeO4 tetrahedra, between which Tl atoms are situated. Anomalously large disordering motions of the SeO4 tetrahedra and Tl atoms are observed in the paraelastic phase.