Über Oxocuprate. XVIII. Zur Kenntnis von Sr₂CuO₂Br₂ mit einem Beitrag über La₂NiO₄

Abstract

Sr2CuO2Br2 (A) und La2NiO4 (B) wurden dargestellt und an Einkristallen röntgenographisch untersucht. (A) ist mit Sr2CuO2Cl2, (B) mit K2NiF4 isotyp. Beide Verbindungen gehören zur Raumgruppe D 4h17–I4/mmm, mit den Gitterkonstanten (A): a = 399,1, c = 1 713,6 pm. (B): a = 387,6, c = 1 268,3 pm. Die Verzerrung der Oktaeder um Cu2+ und Ni2+ wird im Hinblick auf andere isotype Verbindungen diskutiert.

Charge states of transition metal in “Cr, Co and Ni” doped Ln Ca MnO CMR manganites

“…Both the energies of the midheight of the main absorption jump and the calculated mean edge energies for the four compounds (Tab. 1) [29][30][31][32] allow to conclude that cobalt is in the Co 2+ formal state in the substituted manganites within the experimental error on such a determination estimated to ± 10%. Note that the long Co-O distances in CoCO 3 (Tab.…”

Modelling the structures of La2NiO4

“…Two mechanisms are used to relieve the resulting stress: rotation of the NiOg octahedra and the addition of interstitial O atoms. Since Rabenau und Eckerlin (1958) first reported that La2Ni04 has the K2NiF4 structure, it has been the subject of several investigations (Grande and Müller-Buschbaum, 1977;Müller-Buschbaum and Lehmann, 1978;Goodenough and Ramaseshan, 1982;Rodriguez-Carvajal, Martinez, Pannetier and Saez-Puche, 1988;Saez-Puche, Fernandez, Martinez and Rodriguez-Carvajal, 1989;Lander, Brown, Honig and Spalek, 1989) some of which suggest that there are deviations from the archetypal structure. Recent careful investigations by Jorgensen et al (1989) and Rodriguez-Carvajal, Femändez-Diaz and Martinez (1991) have provided details of these deviations and present a consistent picture of the phase diagram.…”

Crystal Chemistry and Magnetic Properties of Layered Metal Oxides Possessing the K2NiF4 or Related Structures

“…Investigations on polycrystalline as well as single crystal samples (6,10,11) of La2 Ni04 have established the structure of this oxide to be tetragonal. Indeed, it was the first oxide to be shown to have the K2NiF4 structure.…”

“…There is no Ni-F-Ni interaction in the direction parallel to the c axis. A variety of oxides are known to crystallize in structures related to K2NiF4 (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14). Besides the tetragonal K2NiF4 structure, A2BO4 type oxides with monoclinic, orthorhombic, and other tetragonal structures have been characterized in recent years (6)(7)(8)(9)(13)(14)(15).…”