  We present a comprehensive study of the structural properties and the thermal
expansion behavior of 17 different Prussian Blue Analogs (PBAs) with
compositions MII3[(M')III(CN)6]2.nH2O and MII2[FeII(CN)6].nH2O, where MII = Mn,
Fe, Co, Ni, Cu and Zn, (M')III = Co, Fe and n is the number of water molecules,
which range from 5 to 18 for these compounds. The PBAs were synthesized via
standard chemical precipitation methods, and temperature-dependent X-ray
diffraction studies were performed in the temperature range between -150oC (123
K) and room-temperature. The vast majority of the studied PBAs were found to
crystallize in cubic structures of space groups, and . The temperature
dependence of the lattice parameters was taken to compute an average
coefficient of linear thermal expansion in the studied temperature range. Of
the 17 compounds, 9 display negative values for the average coefficient of
linear thermal expansion, which can be as large as 39.7 x 10-6 K-1 for
Co3[Co(CN)6]2.12H2O. All of the MII3[CoIII(CN)6]2.nH2O compounds show negative
thermal expansion behavior, which correlates with the Irving-Williams series
for metal complex stability. The thermal expansion behavior for the PBAs of the
MII3[FeIII(CN)6]2.nH2O family are found to switch between positive (for M = Mn,
Co, Ni) and negative (M = Cu, Zn) behavior, depending on the choice of the
metal cation (M). On the other hand, all of the MII2[FeII(CN)6].nH2O compounds
show positive thermal expansion behavior.
