论文信息 - Ab initio structure determination of lanthanum cyclo-tetratungstate α-La2W2O9 from X-ray and neutron powder diffraction

Ab initio structure determination of lanthanum cyclo-tetratungstate α-La2W2O9 from X-ray and neutron powder diffraction

Abstract Lanthanum tungstate α -La 2 W 2 O 9 has been successfully synthesized by the ceramic route. Its crystal structure was determined ab initio from neutron diffraction data (space group P 1 ; No. 2; a =7.2489(1) A b =7.2878(1) A c =7.0435(1) A α =96.367(1)°, β =94.715(1)°, γ =70.286(1)°; Z =2; reliability factors: R p =6.0%, R wp =6.9%, R B =3.0%). The structure exhibits isolated [W 4 O 18 ] 12− groups in the form of rings involving [WO 6 ] octahedra alternating with [WO 5 ] trigonal bipyramids sharing corners. These rings are inserted in the 3D framework built by the 9- and 10-fold coordination polyhedra of the lanthanum atoms.

[1] P. M. D. Wolff. A simplified criterion for the reliability of a powder pattern indexing , 1968 .

[2] Lars Eriksson,et al. TREOR, a semi-exhaustive trial-and-error powder indexing program for all symmetries , 1985 .

[3] J. Launay,et al. Substitution derivatives of the mixed-valence [W4O8Cl8(H2O)4]2- ion. Crystal and molecular structure of Cs5NH4[W4O8(NCS)12].6H2O , 1983 .

[4] R. Retoux,et al. Pb3Al2F12: Crystal structure of a cyclo‐fluoroaluminate related to Ba3Al2F12 , 1994 .

[5] Yvon Laligant,et al. Designing fast oxide-ion conductors based on La2Mo2O 9 , 2000, Nature.

[6] R. Retoux,et al. Pb3Fe2F12: A new fluorometallate with a tetrameric structural unit , 1993 .

[7] M. Yoshimura,et al. High temperature phase relation in the system La2O3WO3 , 1976 .

[8] Y. Shirota. Organic materials for electronic and optoelectronic devices , 2000 .

[9] M. Yoshimura,et al. Identification of binary compounds in the system Ce2O3WO3 , 1976 .

[10] G. S. Smith,et al. FN: A criterion for rating powder diffraction patterns and evaluating the reliability of powder-pattern indexing , 1979 .

[11] N. Bartlett,et al. THE CRYSTAL STRUCTURE OF RHODIUM PENTAFLUORIDE , 1973 .

[12] R. Hoppe,et al. Das erste Cyclo-Fluoroaluminat: Ba3Al2F12 = Ba6F4[Al4F20] (Mit einer Bemerkung über Ba3Ti2F10O2) , 1982 .

[13] F. Goutenoire,et al. Crystal Structure of La2Mo2O9, a New Fast Oxide−Ion Conductor , 2000 .