The results of a high-resolution powder diffraction study of the effect of high hydrostatic pressure up to 8 GPa on the pure

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Two novel sodium salts of the antibiotic ciprofloxacin were crystallised at pressures of 0.25 and 0.6 GPa and subsequently recovered to ambient pressure. The structures are the first reported examples of ciprofloxacin chelating a Group IA monovalent cation. Ambient-pressure crystallisation of the same solution used for high-pressure experiments, yielded crystals of the known hexahydrate. In a parallel study, the previously unknown structure of anhydrous ciprofloxacin was determined from powder diffraction data. The structures are described and compared using the XPac method

A high-pressure cell for single-crystal investigations requires large opening angles. If it does not contain any beryllium but only two diamonds mounted on steel backing plates, normally only lower pressures can be attained without risk of disruption of the diamond anvils [Ahsbahs (2004). Z. Kristallogr. 219,[305][306][307][308]. In order to enable pressures up to at least 10 GPa, specially shaped anvils were designed. In a first study with such anvils, the high-pressure behaviour of zincite ZnO was investigated up to the transition pressure of about 9.5 GPa. A slight decrease of the axial ratio c/a with increasing pressure was observed. The fit of the Birch-Murnaghan equation of state gave a bulk modulus K = 146.5 (8) GPa with a fixed pressure derivative K 0 = 4. During the phase transformation, the single crystals were destroyed. The pronounced preferred orientation of the obtained material, however, enabled the determination of the orientation relations between the low-pressure wurtzite-type and the highpressure NaCl-type phase. The orientation relations are similar to those in CdS and CdSe.

Key indicatorsSingle-crystal X-ray study T = 295 K Mean (C-C) = 0.016 Å R factor = 0.045 wR factor = 0.087 Data-to-parameter ratio = 7.2 For details of how these key indicators were automatically derived from the article, see

High-pressure X-ray investigations on crystal powders of the TiF3, titanium trifluoride, and FeF3, iron trifluoride, phases with VF3-type structures were performed up to 7.67 (7) and 9.00 (7) GPa, respectively. Both compounds are highly compressible and show strong anisotropic behavior. While the hexagonal a lattice parameters are shortened under pressure, the c parameters are elongated. These changes are associated with distortions of the TiF6 and FeF6 coordination octahedra, whereby the octahedron strain is stronger in TiF3 than in FeF3. The high-pressure behavior is characterized by cooperative tiltings of the octahedra, while simultaneously repulsive interactions between the cations probably cause the octahedral distortions.

SummaryThe anisotropy of lattice strain in the crystals of DL-serine (