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The crystal structure of mayenite (12CaO·7Al(2)O(3)) has been investigated by single-crystal synchrotron diffraction with high resolution and accuracy, using a four-circle diffractometer equipped with an avalanche photodiode detector (APD) detector installed at PF14A in Tsukuba, Japan. Analysis revealed random displacements of ions by the electrostatic force of the O(2-) ion (O3) clathrated in two out of 12 cages. O3 ions are located at general positions close to the \bar 4 site at the centre of each cage. The difference-density map revealed two large peaks corresponding to displaced Ca ions. The positive ions close to O3 are displaced and one-to-one correspondence was found between one of the four equivalent O3 ions and the displaced ions. When an O3 ion is present in the cage the Al ion at the 16c position moves 0.946 (3) Å toward the O3 ion. One of the Al-O bonds is broken and a new Al-O3 bond is created. The result is an AlO(4) tetrahedron that is quite deformed. The three O1 ions and the O2 ion of the destroyed AlO(4) tetrahedron are forcibly displaced. O1 and O2 have two and one displaced ions, respectively. The local structure of the cage occupied by one of the four O3 ions was determined by calculating the electrostatic potential and electric field in the deformed cage, although the position of one of the displaced O1 ions was not clearly identified.

SENJU, a time-of-flight Laue-type single-crystal neutron diffractometer, was developed at the Materials and Life Science Experimental Facility of the Japan Accelerator Research Complex (J-PARC). Molecular structure analysis of a sub-millimetre taurine crystal and magnetic structure analysis of an MnF2 crystal were performed to evaluate its performance.

Single crystals of dineodymium(III) dititanium(IV) hepta­oxide, Nd2Ti2O7, were synthesized by the flux method and found to belong to the family of compounds with perovskite-type structural motifs. The asymmetric unit contains four Nd, four Ti and 14 O-atom sites. The perovskite-type slabs are stacked parallel to (010) with a thickness corresponding to four corner-sharing TiO6 octa­hedra. The Nd and Ti ions are displaced from the geometrical centres of respective coordin­ation polyhedra so that the net polarization occurs along the c axis. The investigated crystals were all twinned and have a halved monoclinic unit cell in comparison with the first structure determination of this compound [Scheunemann & Müller-Buschbaum (1975 ▶). J. Inorg. Nucl. Chem. 37, 2261–2263].

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