Zn1.86Cd0.14(OH)VO4

The title compound, dizinc cadmium hydroxide tetraoxidovanadate, Zn1.86Cd0.14(OH)VO4, was prepared under low-temperature hydrothermal conditions. It is isostructural with Zn2(OH)VO4 and Cu2(OH)VO4. In the crystal structure, chains of edge-sharing [ZnO6] octahedra are interconnected by VO4 tetrahedra (site symmetries of both V atoms and their coordination polyhedra are .m.) to form a three-dimensional [Zn(OH)VO4]2− framework with channels occupied by Zn and Zn/Cd cations adopting trigonal–bipyramidal and distorted octahedral coordinations, respectively. Zn1.86Cd0.14(OH)VO4 is topologically related to adamite-type phases, and descloizite- and tsumcorite-type structures.

The title compound, dizinc cadmium hydroxide tetraoxidovanadate, Zn 1.86 Cd 0.14 (OH)VO 4 , was prepared under lowtemperature hydrothermal conditions. It is isostructural with Zn 2 (OH)VO 4 and Cu 2 (OH)VO 4 . In the crystal structure, chains of edge-sharing [ZnO 6 ] octahedra are interconnected by VO 4 tetrahedra (site symmetries of both V atoms and their coordination polyhedra are .m.) to form a three-dimensional [Zn(OH)VO 4 ] 2À framework with channels occupied by Zn and Zn/Cd cations adopting trigonal-bipyramidal and distorted octahedral coordinations, respectively. Zn 1.86 -Cd 0.14 (OH)VO 4 is topologically related to adamite-type phases, and descloizite-and tsumcorite-type structures.

Structure Reports Online
Such case is found in mineral tsumcorite, where [ZnAs 2 O 9 ] chain is linked by sharing two of AsO 4 tetrahedra with each of its two neighbours thus forming a layered structure eighbor and one column with each of the other two neighbours (see

Experimental
Single crystals of (Zn 1.86 Cd 0.14 )(OH)VO 4 were obtained as reaction products from mixtures of Cd(OH) 2 (Alfa Products), 2ZnO.2CO 3 .4H 2 O (Alfa Products), and V 2 O 5 (Fluka Chemika 94710, 98%). The mixture was transferred into Teflon vessel and filled to approximately 70% of their inner volume with distilled water (pH of the mixture was 6). Finally it was enclosed supplementary materials sup-2 into stainless steel autoclave. The mixture was heated under heating regime with three steps: the autoclaves were heated from 293.15 to 473.15 K (4 h), held at 473.15 K for 192 h, and finally cooled to room temperature within 175 h. At the end of the reaction the pH of the solvent was 6. The reaction products were filtered and washed thoroughly with distilled water. (Zn 1.86 Cd 0.14 )(OH)VO 4 crystallized as transparent colourless needle-like crystals (yield ca 65%) and uninvestigated powder (yield ca 35%). All crystals are up to 0.2 mm in length.
Qualitative chemical analyses were performed using a Jeol JSM-6400LV scanning electron microscope (SEM) connected with a LINK energy-dispersive X-ray analysis (EDX) unit confirmed the presence of Zn, Cd and V.

Refinement
Studies of several single crystals of (Zn 1.86 Cd 0.14 )(OH)VO 4 all revealed orthorhombic unit cell. A sample exhibiting sharp reflection spots was chosen for data collection. The crystal structure was refined starting from the atomic coordinates of Zn 2 (OH)VO 4 (Wang et al., 1998) using standard procedures. The space-group symmetry Pnma was indicated by systematic absences and intensity statistics, and was confirmed by the structure refinement. Substitutional disorder was apparent and the occupancies of Zn2 2+ and Cd2 2+ were refined keeping the occupancy sum of Zn2+Cd2 fixed at 2.0 atoms per unit cell to satisfy the charge balance. The atomic coordinates and displacement parameters of Zn2 and Cd2 were kept equal.
Occupancy of 72.7 and 27.3% for Zn2 and Cd2, respectively, were obtained. Anisotropic displacement parameters were allowed to vary for all non-H atoms. The H atoms were located from difference Fourier map and refined as riding atoms, with restraints on the O-H bond distance of 0.82 (2) Å and U iso (H) values at 1.2U eq (O). Fig. 1 bsorption correction: multi-scan (Otwinowski & Minor, 1997;Otwinowski et al., 2003) h = −22→22

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ.