Figure 3 The crystal structure of (NH4)2[FeII3(H2O)2(P2O7)2] is built from zigzag chains of edge-sharing iron octahedra linked by P2O7 pyrophosphate groups to form layers parallel to (100), which are further linked by ammonium ions, sitting at the interlayer space, via the hydrogen bonds. Green octahedron: FeO6, orange tetrahedron: PO4, blue sphere: N atom, dark grey sphere: H atom.  [article HTML]