CoFe Prussian Blue Analogues under Variable Pressure. Evidence of Departure from Cubic Symmetry: X-ray Diffraction and Absorption Study

Energy dispersive X-ray diffraction and X-ray absorption spectra of two CoFe Prussian blue analogues were collected under variable pressure at room temperature: one of them is essentially composed of Co-II and Fe-III ions and undergoes a Co-II-Fe-III -> Co-III-Fe-II pressure-induced electron transfer, whereas the other is essentially composed of Co-III and Fe-II ions whatever the pressure. In both compounds, the Co-III-Fe-II phase undergoes a structural distortion upon compression. The alkali cation free CoFe Prussian blue analogue, in which the pressure-induced electron transfer occurs, exhibits a more complicated interplay between structural and electronic events. Key interatomic interactions are proposed to account for the pressure behavior of both Co-III-Fe-II and Co-II-Fe-III phases.