Professor Ulrich Mu È ller zum 60. Geburtstag gewidmet Inhaltsu È bersicht. Die Kristallstrukturen der Oxidnitride SrTaO 2 N, LaTaON 2 und CaTaO 2 N wurden mit Blick auf eine eventuell vorhandene Ordnung in der anionischen Teilstruktur mit Hilfe von Rietveld-Analysen auf Grundlage von Ro È ntgen-und Neutronenpulverdiffraktometerdaten aufgekla È rt. Die Ro È ntgen-und Neutronenpulverdiffraktogramme wurden zuna È chst individuell verfeinert, um dann durch ¹Joint-Refinementsª zusa È tzlich u È berpru È ft und abgesichert zu werden. Zumindest zwei der drei vermessenen Verbindungen haben eine vollsta È ndig geordnete anionische Teilstruktur. Die Kristallstruktur von SrTaO 2 N wurde in der Raumgruppe I4/mcm (a = 5.7049(3) A Ê , c = 8.0499 (5) A Ê , R p = 0.0706, R wp = 0.0904, Reflexe: 70 (Neutronen) /36 (Ro È ntgen), R(F 2 )(N) = 0.147, R(F 2 )(Ro È ) = 0.0952) mit einer geordneten anionischen Teilstruktur gelo È st. LaTaON 2 kristallisiert monoklin (C2/m, a = 8.0922(3) A Ê , b = 8.0603(2) A Ê , c = 5.7118(2) A Ê , b = 134.815(1)°, R p = 0.0592, R wp = 0.0766, Reflexe 235(N)/113(Ro È ), R(F 2 )(N) = 0.0944, R(F 2 )(Ro È ) = 0.165) und zeigt ebenfalls eine vollsta È ndige Ausordnung der Anionen. Im Falle von CaTaO 2 N (Pnma, a = 5.6239(3) A Ê , b = 7.8954(4) A Ê , c = 5.5473(3) A Ê , R p = 0.0503, R wp = 0.0656, Reflexe 206(N)/110(Ro È ), R(F 2 )(N) = 0.0985, R(F 2 )(Ro È ) = 0.0405) deuten leicht unausgewogene Temperaturparameter (Neutronendaten, Modell mit geordneter O/N-Verteilung) einen partiellen O/N-Austausch an.Abstract. The crystal structures of the perovskite related oxidenitrides SrTaO 2 N, LaTaON 2 and CaTaO 2 N have been determined with special regard to the structures of the respective anionic partial structure. The structure refinements were performed by individual Rietveld analyses of both X-ray and neutron powder diffractograms and in addition by joint refinements in order to confirm the results. Both refinement methods yield consistent structure solutions. At least the first two compounds have fully ordered anionic sublattices. The crystal structure of SrTaO 2 N has been solved in the space group I4/mcm (a = 5.7049(3) A Ê , c = 8.0499(5) A Ê , R p = 0.0706, R wp = 0.0904, reflections: 70 (neutrons)/36 (X-ray), R(F 2 )(n) = 0.147, R(F 2 )(X) = 0.0952), with an ordered anionic partial structure. LaTaON 2 crystallizes monoclinic (C2/m, a = 8.0922(3) A Ê , b = 8.0603(2) A Ê , c = 5.7118(2) A Ê , b = 134.815(1)°, R p = 0.0592, R wp = 0.0766, reflections: 235(n)/ 113(X), R(F 2 )(n) = 0.0944, R(F 2 )(X) = 0.165) and also shows a totally ordered distribution of the anions. In the case of CaTaO 2 N (Pnma, a = 5.6239(3) A Ê , b = 7.8954(4) A Ê , c = 5.5473(3) A Ê , R p = 0.0503, R wp = 0.0656, reflections 206(n)/ 110(X), R(F 2 )(n) = 0.0985, R(F 2 )(X) = 0.0405) slightly unbalanced displacement parameters (neutron data, ordered O/N distribution model) hint at a partial exchange of oxygen and nitrogen.
Professor Klaus-Jürgen Range zum 65. Geburtstag gewidmet Inhaltsübersicht. Durch simultane Bedampfung eines Saphirsubstrates mit Kalium und Stickstoff bei 77 K und anschließendem Aufwärmen wurden zwei Kaliumnitrid-Phasen erhalten. Das Diffraktogramm der einen Phase läßt sich befriedigend unter der Annahme der Zusammensetzung K 3 N und Isotypie zu Cs 3 O (anti-TiI 3 Typ) interpretieren (hexagonal, P6 3 /mcm, a ϭ 779.8(2), c ϭ 759.2(9) pm, Z ϭ 2). Ein Vergleich mit Strukturmodellen, die mit theoretischen Methoden generiert und anschließend auf Hartree-Fock-und DFT Niveau verfeinert wurden, zeigt, dass die hier für Abstract. Two phases in the binary system K/N have been obtained via co-deposition of potassium and nitrogen onto polished sapphire at 77 K and subsequent heating to room temperature. The powder diffraction pattern of one of these phases can be satisfactorily interpreted by assuming the composition K 3 N, and the anti-TiI 3 structure-type, which is also adopted by Cs 3 O. The resulting hexagonal lattice constants are: a ϭ 779.8(2), c ϭ 759.2(9) pm, Z ϭ 2, P6 3 /mcm. Comparison with possible structures of K 3 N generated by computational methods and refined at Hartree-Fock-and DFT level, reveals that the energetically most favoured structure has not
Single crystals of Sb205 were obtained by high oxygen pressure synthesis [P(O2) = 200 MPa]. The crystal structure has been refined by full-matrix least-squares procedures using diffractometer data to a final R value of 0.033 for 695 reflexions; the unit cell is monoclinic, space group C2/c, with dimensions a = 12.646 (1), b --4.7820 (4), c = 5.4247 (5) ,/k, fl = 103.91 (1) °. Sb205 is isostructural with B-Nb205 and consists of distortedcorner and edge-sharing SbO 6 octahedra; the crystal structure can be derived from the rutile-type structure. Sb205 exhibits a strong tendency for polysynthetical twinning.
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