Rodalquilarite Revisited: The Hydrothermal Synthesis and Structural Reinvestigation of H3Fe2(TeO3)4Cl

The known mineral rodalquilarite, H3Fe2(TeO3)4Cl, was obtained as high quality single crystals via hydrothermal reactions. This material crystallizes in the triclinic space group,P , with cell constants ofa=5.103(2) ?,b=6.653(2) ?,c=9.012(3) ?,alpha=73.40(2)°,beta=78.03 (2),gamma=76.76(2),V=282.1(2) ?3and was obtained from an NH4Cl solution that was heated at 375°C for 4 days. A detailed structural characterization was performed (R= 0.039,Rw=0.050) and showed that this material is based on layers consisting of edge-sharing FeO6octahedra which are interconnected by TeO3pyramids which are completed by the presence of a terminal hydrogen atom. Additionally, a second set of TeO3pyramids attached to the FeO6octahedra are linked across the layers by a shared hydrogen atom. The layers are held together only through these O-H-O interactions and additional weak Te-Cl interactions. In this study, we compare this structure to a previous report of rodalquilarite and a reported triclinic form of Fe2Te4O11, which may have been misidentified and is also the title compound. In addition, we have obtained the band gap of this material by diffuse reflectance spectroscopy and find it to be a wide band gap (Eg=2.51eV) material. The DC magnetic susceptibility was also obtained and showed that the title compound is antiferromagnetic with aTNof 29 K.