Showing papers in "Acta Crystallographica Section C-crystal Structure Communications in 1984"

Structure of fluorene, C13H10, at 159 K

Abstract: Cristallisation dans Pnma avec Z=4; affinement jusqu'a R=0,043. La molecule fluorene a la symetrie miroir, mais est legerement non plane. La maille asymetrique, toutefois, est plane, donnant a la molecule une forme «V». Le cristal est bien ordonne

The structure of magnetite: two annealed natural magnetites, Fe3.005O4 and Fe2.96Mg0.04O4

Abstract: Fe 3,005 O 4 (magnetite naturelle recuite a 1373K) cristallise dans Fd3m avec a=8,3969 A, Z=8; affinement jusqu'a R=0,015• Fe 2,96 Mg 0,04 O 4 (magnetite naturelle recuite a 1073 K) cristallise dans Fd3m avec a=8,3975 A, Z=8; affinement jusqu'a R=0,014. Dans les deux cas, structure spinelle inverse ideale. Pas d'observation de defauts cationiques interstitiels, presents dans les echantillons naturels non recuits

Structure of dealuminated Linde Y‐zeolite; Si139.7Al52.3O384 and Si173.1Al18.9O384: presence of non‐framework Al species

Abstract: Utilisation des techniques de diffraction de neutrons sur poudre pour etudier des echantillons de zeolite Y de Linde traites par de la vapeur NH 3 et SiCl 4 gazeux. Cristallisation dans Fd3m (origine au centre (3m) avec Z=1 et a=24,358 A, affinement jusqu'a R=6,57 % dans le premier cas (Si 139,7 Al 52,3 O 384 ); a=24,188 A, affinement jusqu'a R=5,29% dans le second cas (Si 173,1 Al 18,9 O 384 )

Structure studies of thortveitite‐like dimanganese diphosphate, Mn2P2O7

Abstract: Cristallisation dans C2/m avec a=6,633, b=8,584 et c=4,546 A, β=102,67°, Z=2; affinement jusqu'a R=0,083 (diffraction RX sur poudre), R=0,040 (diffraction RX sur monocristal) et R=0,051 (diffraction de neutrons sur poudre). Confirmation de l'isomorphisme avec la thortveitite Sc 2 Si 2 O 7 , mais avec un oxygene pourtant desordonne dans l'anion diphosphate avec une liaison P−O−P non lineaire de 165,9°

Refinement of barium tetratitanate, BaTi4O9, and hexabarium 17‐titanate, Ba6Ti17O40

Abstract: BaTi409: M r = 472.9, orthorhombic, Pmmn, a = 1 4 . 5 2 7 ( 2 ) , b = 3 . 7 9 4 ( 1 ) , c = 6 . 2 9 3 ( 1 ) A , V = 346.8/k 3, Z = 2 , D x = 4 . 5 3 M g m -a, 2(MoK~t)= 0.71069 A, /t = 10.00 mm -~, F(000) = 431.9, T = 293 K, final R = 0 . 0 3 3 for 1614 unique reflexions. Ba6Ti17040: M r = 2278.3, monoclinic, C2/c, a = 9.887(1), b = 17.097 (2), c = 18.918 (2)/k, f l= 98.72 (2) °, V = 3160.9/k 3, Z = 4, D x= 4.79 Mg m -a, 2(Mo Kct) = 0.71069/k, # = 11.47 mm -~, F(000) = 3958.9, T = 293 K, final R = 0.051 for 6945 unique reflexions. Single crystals from both compounds were grown from the melt. The BaTi40 9 compound is best described as a '4 .0 /~ ' structure similar to many alkali titanates, in which the long axes of the octahedra are lined up parallel to the short cell constant. The Ba6Ti17040 compound can be described as a hexagonal closest packing of Ba and O atoms, with Ti in octahedral interstices. Introduction. With the determination of the crystal structure of Ba2Ti9020 (Tillmanns, Hofmeister & Baur, 1983) all the structures of the compounds in the system BaO-TiO 2 are known. Structure determinations have been reported for BaTi40 9 by Lukaszewicz (1957) and Templeton & Dauben (1960) and for Ba6TilTO40 by Tillmanns & Baur (1970). In the course of an investigation of the crystal chemistry of the barium titanate system a refinement of these structures proved necessary in order to obtain more precise coordinates and distances. With bond distances from these newly refined structures a statistically significant dependence of mean bond lengths on octahedral distortions can be established for the titanates (Tillmanns, Hofmeister & Baur, 1984). Experimental. Single crystals of Ba6Ti17040 and BaTi40 9 were taken from a sample of composition BaO:TiO 2 = 1:3 partly melted on a platinum plate at about 1673 K and quenched. Three-dimensional X-ray diffraction intensities were collected with a Nonius CAD-4 computer-controlled diffractometer. For Ba6Ti~7040: crystal irregularly shaped, approximate diameter 0-2 mm; 25 reflexions with 20 < 0 < 30 ° used for determination of lattice parameters; a total of 7464 reflexions collected in range 0.03 < sin0/2 < 0.81 ,/~-i with 0 < h < 1 5 , 0 _ < k < 2 7 and 3 0 < l _ < 3 0 giving 6945 unique reflexions (Rln t = 0 . 0 3 8 ) of which 699 considered unobserved (1 < 2ai); intensities of three standard reflexions monitored after every 6 h, their orientation after every 400 reflexions, measurement instability 0.008; rain. and max. transmission factors for absorption correction 0.09 and 0.27; function minimized ~w(IFol -IF c I) 2, where w for each reflexion is set to 1/a2(F); ratio of max. least-squares shift to error in final cycle 0.2; after a secondary extinction correction (g = 0.0005) final R = 0.051, R w-0.053; final difference synthesis had max. dp excursions of -1 .9e /k -3 at the Ba positions and 1.1 e/k -a at distances of 0 .6-0 .7 ,&. Atomic scattering factors and real and imaginary anomalous-dispersion coefficients from International Tables for X-ray Crystallography (1974). Most experimental conditions were the same for BaTi409: orthorhombic prism with dimensions 0.15 x 0.1 × 0.325 mm; min. and max. transmission factors 0.23 and 0.40; a total of 1614 unique reflexions collected between 0.02 < sin0/2 < 0-90 ,/~-i (measurement instability 0.008, 0_

Structural studies of tetraaquabis(saccharinato-N)zinc(II) dihydrate, [Zn(C7H4NO3S)2(H2O)4].2H2O, and tetraaquabis(saccharinato-N)cadmium(II) dihydrate, [Cd(C7H4NO3S)2(H2O)4].2H2O

Abstract: Zn compound\" M r = 5 3 7 . 8 2 , monoclinic, P2Jc, a = 7.939 (2), b = 16. 120 (2), c = 7.691 (2)/~, fl = 99.87 (2) °, V = 969.7 A 3, Z = 2, O m = 1.83, D x -1.84 g cm -3, Mo Kt~, ~. = 0.71069 ~, g = 14.7 cm -~, F(000) = 552, T = 294 (2) K. Cd compound: M r = 584.85, monoclinic, P2Jc, a = 8.036 (2), b = 16.145(3), c = 7 . 8 7 0 ( 1 ) A , f l = 1 0 0 . 2 4 ( 1 ) °, V = 1004.8 ,~3, Z = 2, D m = 1.92, D x = 1.93 gcm -3, Mo K~t, 2 = 0.71069 ,~, g = 12.4 cm -l, F(000) = 588, T = 294 (2) K. R = 0 . 0 2 8 and 0.025 for 1581 and * Saccharin is 1,2-benzisothiazol-3 (2H)-one 1,1-dioxide. \"t\" To whom correspondence should be addressed. 1850 intensities, respectively. The isostructural pair of complexes have centrosymmetric trans octahedral geometry. Delocalization of the charge away from the N atom may explain the weakness of the M N bond. The structures of the Cd H and Zn ~ compounds are compared with those involving Mn H, Fe II, Co H, Ni x~ and Cu ~I and trends in the metal-ligand M--N, M--OH 2 bond lengths are discussed. Introduction. We have described the syntheses and properties of a series of complexes with general formula [M(C7H4NO3S)2(H20)4].2H20 ( M M n Ix, Fe II, Co n, Ni II, Cu II and Zn II) (Haider, Malik & Ahmed, 1981; 0108-2701/84/071147-04501.50 © 1984 International Union of Crystallography 1148 [Zn(CTH4NO3S)2(H20)4].2H20 AND [Cd(CTH4NOaS)2(H20)4].2H20 Haider & Malik, 1982) and reported the crystal structure analyses of the Fe, Co, Ni and Cu complexes (Ahmed, Habib, Haider, Malik & Hursthouse, 1981; Haider, Malik, Ahmed, Hess, Riffel & Hursthouse, 1983). While our work was in progress an independent structural report of the corresponding Mn complex appeared (Kamenar & Jovanovski, 1982). In the present paper, we describe the crystal structure determinations of the Zn and Cd derivatives and discuss the structural variations in all seven related complexes. Experimental. Zn complex (ZNSAC) prepared as described earlier (Haider & Malik, 1982). Cd complex (CDSAC) prepared by reacting cadmium chloride with Na-saccharin in aqueous medium (Haider, Malik, Hursthouse & Wadsten, 1984). D m by flotation. Crystals suitable for X-ray work obtained by recrystallization from water. Lattice parameters determined by least-squares refinement of setting angles for 25 reflections [16 < 8(Mo K0t) < 17°], automatically centred on Enraf-Nonius CAD-4 diffractometer; intensity data recorded on same instrument, MoK~t radiation (graphite monochromator), following procedures described earlier (Hursthouse, Jones, Malik & Wilkinson, 1979). Semi-empirical absorption corrections applied to both data sets, using ~-scan values for 3 reflections in each case. Merging equivalent reflections and omitting those with F o < 3a(Fo) yielded 1581 (ZNSAC) and 1850 (CDSAC) unique data, which were used in structure analyses. Further experimental information is given in Table 1. Structures solved by heavy-atom method and refined by least squares. All non-hydrogen atoms refined anisotropically, hydrogen atoms (located from difference maps) isotropically. In final stage of refinement empirical isotropic extinction parameter x varied in modified expression for calculated structure factor, F c' = F~(1 x Fc2/sin8), and weighting scheme based on w = 1/[a2(Fo) + gFo 2] applied. Refinement on F converged at R =0.0281 (ZNSAC) and 0.0246 (CDSAC), with d / a < 0.1, absolute values of peaks and troughs in final difference maps <0.3e/% -3. Calculations performed on DEC VAXll /750 computer using S H E L X 7 6 (Sheldrick, 1976). Neutral-atom scattering factors from Cromer & Mann (1968) and Stewart, Davidson & Simpson (1965) for non-H and H atoms, respectively. Final atomic parameters and the bond lengths and angles involving the non-H atoms are given in Tables 2 and 3, respectively.* * Lists of structure factors, anisotropic thermal parameters, coordinates, bond lengths and angles involving the saccharinato hydrogen atoms, hydrogen-bond dimensions and data related to least-squares plane and dihedral angle calculations have been deposited with the British Library Lending Division as Supplementary Publication No. SUP 39313 (22 pp.). Copies may be obtained through The Executive Secretary, International Union of Crystallography, 5 Abbey Square, Chester CH 1 2HU, England. Table 1. Exper imenta l details

Hexagonal Y13Pd40Sn31, a new structure type containing intergrown CaCu5- and MnCu2Al-type derived structure segments

Abstract: Cristallisation dans P6/mmm avec a=19,891 et c=9,246 A, Z=2. Affinement jusqu'a R=0,067. La structure peut etre interpretee comme une intercroissance de trois types de segments de structure: Le premier est une variante d'ordre ternaire de type CaCu 5 , le second a un arrangement atomique semblable a celui de YPd 2 Sn, avec le type MnCu 2 Al et le troisieme est une colonne de prismes Sn a centre Pd et des prismes Pd a centre Sn. CeNi 5 Sn peut etre egalement interprete comme une intercroissance de deux types de structure