Crystal structure of a vivianite-type mineral: Mg-rich erythrite, (Co2.16Ni0.24Mg0.60)(AsO4)2 · 8 H2O

Abstract

The crystal structure of erythrite from Bouzaer, south Morocco, was refined through single crystal X-ray diffraction data, within monoclinic space group C2/m, with the following unit cell constants: a = 10.187(1) Å, b = 13.470(1) Å, c = 4.755(1) Å, β = 104.971(2)°, V = 630.3(2) Å3. Transition metal and magnesium cations are randomly distributed over two special positions Me(1) and Me(2), making up single and dimerical octahedral groups, connected by (AsO4) tetrahedra groups, in order to form infinite sheets down b. Such sheets are held together within the three-dimensional framework owing to the presence of an intricate hydrogen bond network. An infrared spectrum was collected in order to achieve information on the HOH bending modes of the erythrite.