Large Lattice Responses in a Mixed-Valence Prussian Blue Analogue Owing to Electronic and Spin Transitions Induced by X-ray Irradiation^†

Illuminating phase changes: Absorption of X-ray photons induces reversible internal charge-transfer processes in the mixed-valence Mn/Fe cyanide Rb_0.7Mn^II_1.15[Fe^III(CN)₆]⋅2 H₂O over a broad temperature range. Both continuous and abrupt phase transformations can be triggered (see scheme; HS=high spin, LS=low spin) and because the X-rays simultaneously probe the structural properties of the material, the resulting phase diagram can be elucidated in detail.