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K 3 NiO 2 Revisited, Phase Transition and Crystal Structure Refinement
Author(s) -
Đuriš Katarina,
Müller Ulrich,
Jansen Martin
Publication year - 2012
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.201100511
Subject(s) - non blocking i/o , crystallography , crystal structure , stoichiometry , materials science , phase (matter) , microcrystalline , phase transition , single crystal , crystal (programming language) , analytical chemistry (journal) , chemistry , physics , thermodynamics , biochemistry , organic chemistry , chromatography , catalysis , computer science , programming language
Single crystals as well as microcrystalline powders of K 3 NiO 2 were obtained via the azide/nitrate route, starting from stoichiometric mixtures of KN 3 , KNO 3 and NiO, at 923 K. According to temperature dependent X‐ray investigations, K 3 NiO 2 exhibits a phase transition at approx. 423 K. Single crystal X‐ray analysis at 500 K has shown that the high temperature modification ( β ‐K 3 NiO 2 , tP 12) crystallizes in P 4 2 / mnm ( Z = 2, a = 6.0310(9), c = 7.156(1) Å, R 1 = 0.037, R 2 = 0.105). The ambient temperature modification ( α ‐K 3 NiO 2 , tP 24) was refined as a racemic twin ( P 4 1 2 1 2/ P 4 3 2 1 2; a = 6.012(4), c = 13.843(8) Å, R 1 = 0.029, R 2 = 0.070 at 100 K; a = 6.0300(9), c = 14.065(3) Å, R 1 = 0.032, R 2 = 0.082 at 298 K) yielding nearly equal volumes for both enantiomorphs. The structural relationship within the A 3 MX 2 family is analyzed and displayed as a Bärnighausen tree. The essential feature of the low and high temperature phases are isolated NiO 2 3– dumbbells, which are linked by potassium atoms to infinite chains.