title: A novel cobalt sodium phosphate hydroxide with the ellenbergerite topology: crystal structure and physical properties.
abstract: The novel phase Na2-xCo6(OH)3[HPO4][Hx/3PO4]3 (x≈ 1.1) was prepared by hydrothermal synthesis at 553 K. Its crystal structure was determined using single-crystal X-ray diffraction data and refined against F(2) to R = 0.052, including positions of all hydrogen atoms. The compound crystallizes in the hexagonal space group P63mc, with unit-cell parameters a = 12.630(3) Å, c = 5.017(1) Å, V = 693.1(3) Å(3), and Z = 2. The crystal structure is based on a 3D framework built from CoO6 octahedra and PO4 tetrahedra. Channels in the [001] direction accommodate columns of Na-centered octahedra sharing faces. The compound is a new structural representative of the topology shown by aluminosilicate mineral ellenbergerite and its numerous natural and synthetic varieties. Magnetic susceptibility measurements revealed a strong antiferromagnetic interaction and magnetic transition to low temperature spin-canted phase at TN = 44 K. The physical properties of the title compound are found to be very similar to those of the structurally related arsenate Co1-xCo6(OH)3[H2x/3AsO4]3[HAsO4] and vanadate Co7(OH)2(H2O)[VO4]4.
authors.affiliation: Lomonosov Moscow State University, Vorob'evy Gory, 119991 Moscow, Russia. yakubol@geol.msu.ru.
authors.forename: Olga V
authors.initials: OV
authors.lastname: Yakubovich
authors.forename: Galina V
authors.initials: GV
authors.lastname: Kiriukhina
authors.forename: Olga V
authors.initials: OV
authors.lastname: Dimitrova
authors.forename: Larisa V
authors.initials: LV
authors.lastname: Shvanskaya
authors.forename: Olga S
authors.initials: OS
authors.lastname: Volkova
authors.forename: Alexander N
authors.initials: AN
authors.lastname: Vasiliev