The optimized crystal structure of rhombohedral Prussian White (R-PW) exhibits the R 3 symmetry as shown in Figure , with the octahedral coordination of the high spin and low spin Fe +2 still being the dominant feature. The cooperative out-of-phase rotation of the octahedra still allows for straight C≡N bonds after the distortion. The rotation is accompanied by a shift of the sodium atoms along the [111] axis of the cubic cell towards its vertices leading to a concentration of the sodium atoms within "layers" (along the c-axis) of FeN 6 octahedra. This in turn optimizes the Na-N interactions in the crystal, providing an octahedral coordination of nitrogen around the sodium atoms. Within these Na-N octahedra the sodium ions move towards the face site which is not face-connected to an FeC 6 octahedra as to optimize the space available to them.