Synthesis, crystal structure determination of a novel phosphate Ag(1.64)Zn(1.64)Fe(1.36)(PO(4))(3) with an alluaudite-like structure

Single crystals of Ag(1.64)Zn(1.64)Fe(1.36)(PO(4))(3) [silver zinc iron phosphate (1.64/1.64/1.36/3)] have been synthesized by a conventional solid-state reaction and structurally characterized by single-crystal X-ray diffraction. The title compound crystallizes with an alluaudite-like structure. All atoms of the structure are in general positions except for four, which reside on special positions of the space group, C2/c. The Ag(+) cations reside at full occupancy on inversion centre sites and at partial occupancy (64%) on a twofold rotation axis. In this structure, the unique Fe(3+) ion with one of the two Zn(2+) cations are substitutionally disordered on the same general position (Wyckoff site 8f), with a respective ratio of 0.68/0.32 (occupancies were fixed so as to ensure electrical neutrality for the whole structure). The remaining O and P atoms are located in general positions. The three-dimensional framework of this structure consists of kinked chains of edge-sharing octa­hedra stacked parallel to [10[Image: see text]]. These chains are built up by a succession of [MO(6)] (M = Zn/Fe or Zn) units. Adjacent chains are connected by the PO(4) anions, forming sheets oriented perpendicular to [010]. These inter­connected sheets generate two types of channels parallel to the c axis, in which the Ag(+) cations are located. The validity and adequacy of the proposed structural model of Ag(1.64)Zn(1.64)Fe(1.36)(PO(4))(3) was established by means of bond-valence-sum (BVS) and charge-distribution (CHARDI) analysis tools.