Acta Crystallographica Section C

Crystal Structure Communications

Volume 62, Part 11 (November 2006)

inorganic compounds

Acta Cryst. (2006). C62, i91-i93 [ doi:10.1107/S0108270106028678 ]

Centrosymmetric aliovalent KTP isomorphs KM^III_0.5Nb_0.5OPO₄ (M = Cr and Fe)

A. A. Babaryk, I. V. Zatovsky, V. N. Baumer, N. S. Slobodyanik and O. V. Shishkin

Abstract: Aliovalent KTP isomorphic compounds potassium chromium niobium oxide phosphate, KCr_0.5Nb_0.5OPO₄, and potassium iron niobium oxide phosphate, KFe_0.5Nb_0.5OPO₄, exhibit structures that differ from that of the non-centrosymmetric KTiOPO₄. There are two crystallographically independent octahedral sites, M1 and M2, statistically occupied by Nb and Cr (or Fe) atoms. The M1O₆ and M2O₆ octahedra are connected alternately to form a chain with a cis-trans arrangement. The Nb atoms prefer the M2 sites arranged in a cis-like configuration. Each PO₄ tetrahedon has the P atom on a twofold axis. Site-splitting at the K-atom position is observed in both compounds. In the isomorphous structures, one Nb atom lies on an inversion centre and the other on a twofold axis. Similarly with the pairs of Fe/Cr sites, one is on an inversion centre and the other on a twofold axis.

Formula: KCr_0.5Nb_0.5OPO₄ and KFe_0.5Nb_0.5OPO₄


	Structure factor file (CIF format) (52.2 kbytes) [ doi:10.1107/S0108270106028678/iz3009Isup2.hkl ] Contains datablock I

	Structure factor file (CIF format) (52.8 kbytes) [ doi:10.1107/S0108270106028678/iz3009IIsup3.hkl ] Contains datablock II

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