Investigating the relationship between pressure-induced tilting and A-site cations in Prussian blue analogues

We propose a high-pressure study of a number of Prussian blue analogues (PBAs) of formula AMn[Co(CN)6] (where A = Cs+, Rb+, K+) to investigate the influence of the A-site cation size on the high-pressure behaviour. Preliminary X-ray experiments show that CsMn[Co(CN)6] transforms to a tetragonal phase upon compression, whereas A-site deficient PBAs of similar composition behave fundamentally differently. We now wish to understand the compression behaviour in more detail by using neutron radiation to accurately locate the cyanide ions. Amongst other things, this will enable us to monitor changes in tilt angles upon compression. The interplay between cations and tilting distortion is a crucial consideration for the development of PBAs as cathodes in alkali ion batteries, and our study—although fundamental in nature—has implications for applications in electrochemical energy storage.