Reinvestigation of KMg1/3Nb2/3OPO4 1

The crystal structure of potassium magnesium niobium oxide phosphate, KMg(1/3)Nb(2/3)OPO(4), which was described in the space group P4(3)22 [McCarron & Calabrese, (1993 ▶). J. Solid State Chem.102, 354-361], has been redetermined in the revised space group P4(1). Accordingly, the assignment of the space group P4(3)22 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 KTiOPO(4) structure analogues. It has been shown that the geometry of the {M(II) (1/3)Nb(2/3)O(6/2)}(∞) framework is almost unaffected by the lowering of symmetry.