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Redetermination of kovdorskite, Mg(2)PO(4)(OH)·3H(2)O.

ABSTRACT: The crystal structure of kovdorskite, ideally Mg(2)PO(4)(OH)·3H(2)O (dimagnesium phosphate hydroxide trihydrate), was reported previously with isotropic displacement paramaters only and without H-atom positions [Ovchinnikov et al. (1980 ?). Dokl. Akad. Nauk SSSR.255, 351-354]. In this study, the kovdorskite structure is redetermined based on single-crystal X-ray diffraction data from a sample from the type locality, the Kovdor massif, Kola Peninsula, Russia, with anisotropic displacement parameters for all non-H atoms, with all H-atom located and with higher precision. Moreover, inconsistencies of the previously published structural data with respect to reported and calculated X-ray powder patterns are also discussed. The structure of kovdorskite contains a set of four edge-sharing MgO(6) octa-hedra inter-connected by PO(4) tetra-hedra and O-H?O hydrogen bonds, forming columns and channels parallel to [001]. The hydrogen-bonding system in kovdorskite is formed through the water mol-ecules, with the OH(-) ions contributing little, if any, to the system, as indicated by the long H?A distances (>2.50?Å) to the nearest O atoms. The hydrogen-bond lengths determined from the structure refinement agree well with Raman spectroscopic data.

SUBMITTER: Morrison SM

PROVIDER: S-EPMC3274836 | biostudies-other | 2012 Feb

REPOSITORIES: biostudies-other

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Redetermination of kovdorskite, Mg(2)PO(4)(OH)·3H(2)O.

Morrison Shaunna M SM Downs Robert T RT Yang Hexiong H

Acta crystallographica. Section E, Structure reports online 20120111 Pt 2

The crystal structure of kovdorskite, ideally Mg(2)PO(4)(OH)·3H(2)O (dimagnesium phosphate hydroxide trihydrate), was reported previously with isotropic displacement paramaters only and without H-atom positions [Ovchinnikov et al. (1980 ▶). Dokl. Akad. Nauk SSSR.255, 351-354]. In this study, the kovdorskite structure is redetermined based on single-crystal X-ray diffraction data from a sample from the type locality, the Kovdor massif, Kola Peninsula, Russia, with anisotropic displacement paramet ...[more]

PMID: 22346789

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Project description:The crystal structure of brackebuschite, ideally Pb2Mn(3+)(VO4)2(OH) [dilead(II) manganese(III) vanadate(V) hydroxide], was redetermined based on single-crystal X-ray diffraction data of a natural sample from the type locality Sierra de Cordoba, Argentina. Improving on previous results, anisotropic displacement parameters for all non-H atoms were refined and the H atom located, obtaining a significant improvement of accuracy and an unambiguous hydrogen-bonding scheme. Brackebuschite belongs to the brackebuschite group of minerals with general formula A 2 M(T1O4)(T2O4)(OH, H2O), with A = Pb(2+), Ba, Ca, Sr; M = Cu(2+), Zn, Fe(2+), Fe(3+), Mn(3+), Al; T1 = As(5+), P, V(5+); and T2 = As(5+), P, V(5+), S(6+). The crystal structure of brackebuschite is based on a cubic closest-packed array of O and Pb atoms with infinite chains of edge-sharing [Mn(3+)O6] octa-hedra located about inversion centres and decorated by two unique VO4 tetra-hedra (each located on a special position 2e, site symmetry m). One type of VO4 tetra-hedra is linked with the (1) ?[MnO4/2O2/1] chain by one common vertex, alternating with H atoms along the chain, while the other type of VO4 tetra-hedra link two adjacent octa-hedra by sharing two vertices with them and thereby participating in the formation of a three-membered Mn2V ring between the central atoms. The (1) ?[Mn(3+)(VO4)2OH] chains run parallel to [010] and are held together by two types of irregular [PbO x ] polyhedra (x = 8, 11), both located on special position 2e (site symmetry m). The magnitude of the libration component of the O atoms of the (1) ?[Mn(3+)(VO4)2OH] chain increases linearly with the distance from the centerline of the chain, indicating a significant twisting to and fro of the chain along [010]. The hy-droxy group bridges one Pb(2+) cation with two Mn(3+) cations and forms an almost linear hydrogen bond with a vanadate group of a neighbouring chain. The O?O distance of this inter-action determined from the structure refinement agrees well with Raman spectroscopic data.

Dataset Information

Redetermination of kovdorskite, Mg(2)PO(4)(OH)·3H(2)O.

Publications

Redetermination of kovdorskite, Mg(2)PO(4)(OH)·3H(2)O.

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