Reinvestigation of KMg1/3Nb2/3OPO4

Artem A Babaryk,Vasily Pekhnyo,Vladimir Bon,Nikolay S Slobodyanik,Igor V Zatovsky

doi:10.1107/s1600536810004617

Artem A Babaryk, Vasily Pekhnyo + Show 3 more

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https://doi.org/10.1107/s1600536810004617

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Abstract

The crystal structure of potassium magnesium niobium oxide phosphate, KMg1/3Nb2/3OPO4, which was described in the space group P4322 [McCarron & Calabrese, (1993 ▶). J. Solid State Chem. 102, 354–361], has been redetermined in the revised space group P41. Accordingly, the assignment of the space group P4322 and, therefore, localization of K at a single half-occupied position, as noted in the previous study, proved to be an artifact. As a consequence, two major and two minor positions of K are observed due to the splitting along [001], as first noted for KTiOPO4 structure analogues. It has been shown that the geometry of the {M II 1/3Nb2/3O6/2}∞ framework is almost unaffected by the lowering of symmetry.

Highlights

The crystal structure of potassium magnesium niobium oxide phosphate, KMg1/3Nb2/3OPO4, which was described in the space group P4322 [McCarron & Calabrese, (1993)
It has been shown that the geometry of the {MII1/3Nb2/3O6/2}1 framework is almost unaffected by the lowering of symmetry
For tetragonal aliovalent analogues related to KTiOPO4, see: Peuchert et al (1995); Babaryk et al (2007b)

Summary

Bruker APEXII diffractometer

Absorption correction: multi-scan [SORTAV (Blessing, 1995) and SADABS (Bruker, 2007)]. Key indicators: single-crystal X-ray study; T = 293 K; mean (P–O) = 0.004 Å; disorder in main residue; R factor = 0.025; wR factor = 0.055; data-to-parameter ratio = 9.7. The crystal structure of potassium magnesium niobium oxide phosphate, KMg1/3Nb2/3OPO4, which was described in the space group P4322 [McCarron & Calabrese, (1993). 102, 354–361], has been redetermined in the revised space group P41. The assignment of the space group P4322 and, localization of K at a single half-occupied position, as noted in the previous study, proved to be an artifact. Two major and two minor positions of K are observed due to the splitting along [001], as first noted for KTiOPO4 structure analogues. It has been shown that the geometry of the {MII1/3Nb2/3O6/2}1 framework is almost unaffected by the lowering of symmetry

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