As anticipated, therefore, variable temperature X-ray diffraction experiments confirmed that both Fe[Bi(SCN) 6 ] and Cr[Bi(SCN) 6 ] remain in this monoclinic structure until their decomposition: single crystal diffraction on Fe[Bi(SCN) 6 ] shows no phase transitions between -93 and 102 • C, and variable temperature PXRD studies on Cr[Bi(SCN) 6 ] show that it remains isostructural from room temperature up to 300 • C. The single crystal structures of Fe[Bi(SCN) 6 at different temperatures show that the changes in tilt angles are comparatively small compared to their magnitude: they decrease by approximately 1 size of the tilts in these perovskites mean that the magnitude of the decomposed rotations will depend strongly upon which order the rotations are applied, and so there no unique description. ] over this region (1.7 %) is significantly smaller than the volume difference between the hypothetical aristotype and the room temperature structure (54 %). As the changes in sin(θ ) are two orders of magnitude smaller than the strains along the unit cell axis directions the strain eigenvalues are to a good approximation equal to the unit cell axis strains.