RESUMO
SENJU is a new single-crystal time-of-flight neutron diffractometer installed at BL18 at the Materials and Life Science Experimental Facility of the Japan Accelerator Research Complex (J-PARC). The diffractometer was designed for precise crystal and magnetic structure analyses under multiple extreme sample environments such as low temperature, high pressure and high magnetic field, and for diffraction measurements of small single crystals down to 0.1â mm3 in volume. SENJU comprises three choppers, an elliptical shape straight supermirror guide, a vacuum sample chamber and 37 scintillator area detectors. The moderator-to-sample distance is 34.8â m, and the sample-to-detector distance is 800â mm. The wavelength of incident neutrons is 0.4-4.4â Å (first frame). Because short-wavelength neutrons are available and the large solid angle around the sample position is covered by the area detectors, a large reciprocal space can be simultaneously measured. Furthermore, the vacuum sample chamber and collimator have been designed to produce a very low background level. Thus, the measurement of a small single crystal is possible. As sample environment devices, a newly developed cryostat with a two-axis (ω and φ axes) goniometer and some extreme environment devices, e.g. a vertical-field magnet, high-temperature furnace and high-pressure cell, are available. The structure analysis of a sub-millimetre size (0.1â mm3) single organic crystal, taurine, and a magnetic structure analysis of the antiferromagnetic phase of MnF2 have been performed. These results demonstrate that SENJU can be a powerful tool to promote materials science research.
RESUMO
Single crystals of dineodymium(III) dititanium(IV) hepta-oxide, 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 octa-hedra. The Nd and Ti ions are displaced from the geometrical centres of respective coordin-ation 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 â¶). J. Inorg. Nucl. Chem. 37, 2261-2263].
RESUMO
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.
RESUMO
A general expression of the polarization factor of multi-diffracted beams is formulated. By assigning the diffracted beam direction of each diffraction process as the y axis of a Cartesian coordinate system, the polarization factor of multi-diffraction processes can be easily calculated for polarized and unpolarized beams without being limited by the number of diffraction processes. The method can be applied to processes with more than three scattering events such as multiple diffraction and extinction.
RESUMO
The crystal structure of EuRu(4)P(12) is isotypic with filled skutterudite structures of rare earth transition metal poly-phosphides: RFe(4)P(12) (R = Ce, Pr, Nd, Sm and Eu), RRu(4)P(12) (R = La, Ce, Pr and Nd) and ROs(4)P(12) (R = La, Ce, Pr and Nd). The Ru cation is coordinated by six P anions in a distorted octa-hedral manner. The partially occupied Eu position (site occupancy 0.97) is enclosed by a cage formed by the corner-shared framework of the eight RuP(6) octa-hedra.
RESUMO
Single crystals of the title compound, strontium tetra-praseo-dymium tris-(silicate) oxide, SrPr(4)(SiO(4))(3)O, have been grown by the self-flux method using SrCl(2). The structure is isotypic with the apatite supergroup family having the generic formula (IX)M1(2) (VII)M2(3)((IV)TO(4))(3)X, where M = alkaline earth and rare earth metals, T = Si and X = O. The M1 site (3.. symmetry) is occupied by Pr and Sr atoms with almost even proportions and is surrounded by nine O atoms forming a tricapped trigonal prism. The M2 site (m.. symmetry) is almost exclusively occupied by Pr and surrounded by seven O atoms, forming a distorted penta-gonal bipyramid. The Si atom (m.. symmetry) is surrounded by two O (m.. symmetry) and two O atoms in general positions, forming an isolated SiO(4) tetra-hedron. Another O atom at the inversion centre (.. symmetry) is surrounded by three M2 sites, forming an equilateral triangle perpendicular to the c axis.
RESUMO
Single crystals of the title compound, calcium neodymium ruthenate, (Ca(x)Nd(11-x))Ru(4)O(24) (x = 4.175), have been grown by the flux method. The structure consists of two crystallographically independent RuO(6) octa-hedra, which are isolated from each other and embedded in a matrix composed of the Ca and Nd atoms. There are seven M sites which accommodate the Ca and Nd atoms with different populations. Four M sites at general positions are enriched with Nd, whereas the remaining three M sites on twofold rotation axes are enriched with Ca. The coordination numbers of O atoms to the M sites range from 6 to 9. The mean oxidation state of Ru was estimated at +4.79 from the composition analysis. The title compound is non-centrosymmetric and potentially multiferroic.
RESUMO
The title compound, Nd(3)Fe(5)O(12) (NdIG), has an iron garnet structure. One of the Fe atoms is coordinated by six O atoms in a slightly distorted octa-hedral geometry and has site symmetry. The other Fe atom is coordinated by four O atoms in a slightly distorted tetra-hedral geometry and has site symmetry. The FeO(6) octa-hedron and FeO(4) tetra-hedron are linked together by corners. The Nd atom is coordinated by eight O atoms in a distorted dodeca-hedral geometry and has 222 site symmetry. The O atoms occupy general positions.
RESUMO
The title compound, penta-iron tripraseodymium dodeca-oxide (PrIG), has an iron garnet structure. There are two Fe site symmetries. One of the Fe atoms is coordinated by six O atoms, forming a slightly distorted octa-hedron, and has site symmetry. The other Fe atom is coordinated by four O atoms, forming a slightly distorted tetra-hedron, and has site symmetry. FeO(6) octa-hedra and FeO(4) tetra-hedra are linked together by corners. The Pr atom is coordinated by eight O atoms, forming a distorted dodeca-hedron, and has 222 site symmetry. The O atoms occupy the general positions.
