Rietveld analyses performed on high-temperature X-ray (HTXRD) and neutron (HTND) powder patterns of β-(Zr 2 O)(PO 4 ) 2 have allowed us to follow accurately the thermal variations of the cell parameters and to explain its strong dilatometric anisotropy in terms of structural distortions. It appeared that the anomaly resulted from two simultaneous mechanical effects: libration movements of the bridging oxygen atoms related to a rocking of the ZrO 7 and PO 4 polyhedra and a rotation effect resulting from electrostatic repulsions between Zr IV cations of neighbor polyhedra. Both effects lead to a strong shrinkage of the b parameter and contribute to the ultralow overall expansion that has made β-(Zr 2 O)(PO 4 ) 2 famous as a thermal-shock resistant material.
The crystallographic characterization of N-(2-hydroxybenzylideneamino)benzamide, C14 HI2 N2 O2, reveals quasi coplanarity of the whole molecular skeleton, localization of the double bonds in the central --C~N--N--C=~ chain, which has an E configuration with respect to the double bond of the hydrazone bridge, and an amide trans, s-cis configuration around the single N--N bond. The molecules are held together by hydrogen bonds linking them into layers along the [ 100] direction.
CommentAroyl hydrazones are currently being investigated as orally active iron chelators for the treatment of iron
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