Vibrational spectroscopy of 2:1 family of Prussian Blue Analogues

Prussian Blue Analogues (PBAs) have important technological applications in negative thermal expansion, hydrogen storage and magneto optical devices. It provides large tolerances for atomic substitutions, which opens up the prospect that one can tune their functional properties to specialized applications. In the PBAs framework structure there are coordinated water molecules and interstitial water molecules that affect the properties. We synthesized 5 different compounds with compositions M^II₂[Fe^II(CN)₆]. xH₂O, where M = Mn, Co, Ni, Cu, and Zn and x is number of water molecules. Thermogravimetric Analysis was used to find the number of water molecule in each compound. The positions of water molecules were determined using Rietveld refinement of X-ray diffraction data. The neutron vibrational spectrum for all those compounds were studied in detail. It shows well-defined, well-separated bands corresponding to stretching and deformation modes of the Fe and M^II octahedra.