Disodium tris­(dioxidomolybdenum) bis­(diarsenate)

The asymmetric unit of the title compound, Na2(MoO2)3(As2O7)2, is composed of two cyclic MoAs2O11 units and an MoO6 corner-sharing octa­hedron. The anionic framework can be decomposed into two types of layers, viz. MoO2As2O7 and Mo2As2O14, which use mixed Mo—O—As and As—O—Mo bridges to achieve a new three-dimensional structure with two types of large channels in which the Na+ cations are located. Two O atoms are disordered and are located in two positions close to their initial positions with occupancy ratios of 0.612 (17):0.388 (17) and 0.703 (12):0.298 (12)

K0.8Ag0.2Nb4O9AsO4

The title compound, potassium silver tetra­niobium nona­oxide arsenate, K0.8Ag0.2Nb4O9AsO4, was prepared by a solid-state reaction at 1183 K. The structure consists of infinite (Nb2AsO14)n chains parallel to the b axis and cross-linked by corner sharing via pairs of edge-sharing octa­hedra. Each pair links together four infinite chains to form a three-dimensional framework. The K+ and Ag+ ions partially occupy several independent close positions in the inter­connected cavities delimited by the framework. K0.8Ag0.2Nb4O9AsO4 is likely to exhibit fast alkali-ion mobility and ion-exchange properties. The Wyckoff symbols of special positions are as follows: one Nb 8e, one Nb 8g, As 4c, two K 8f, one Ag 8f, one Ag 4c, one O 8g, one O 4c

La variété β-NaMoO2(AsO4)

The title compound, sodium dioxidomolybdenum(VI) arsenate(V), β-NaMoO2AsO4, was prepared by solid-state reaction at 953 K. In the crystal structure, the AsO4 tetra­hedra and MoO6 octa­hedra (both with m symmetry) share corner atoms to form a three-dimensional framework that delimits cavities parallel to [010] where disordered six-coordinated sodium cations (half-occupation) are located. Structural relationships between the different orthoarsenates of the AMoO2AsO4 series (A = Ag, Li, Na, K and Rb) are discussed

AgNa2Mo3O9AsO4

The title compound, silver disodium trimolybdenum(VI) nonaoxide arsenate, AgNa2Mo3O9AsO4, was prepared by a solid-state reaction at 808 K. The structure consists of an infinite (Mo3AsO13)n ribbon, parallel to the c axis, composed of AsO4 tetra­hedra and MoO6 octa­hedra sharing edges and corners. The Na and Ag ions partially occupy several independent close positions, with various occupancies, in the inter-ribbon space delimited by the one-dimensional framework. The composition was refined to Ag1.06(1)Na1.94(1)Mo3O9AsO4