A comparison of the calculated structural properties between the cubic and rhombohedral phases of PW, as well as experimental data for two rhombohedral PW compounds is This displacement has to be an angular shift of the cyanide ligands with respect to the Fe-CN-Fe axis, as it causes a shortening of the Fe-Fe distance, while keeping all other distances constant. The fact that the observed bond angles are deviating from their ideal values verifies this conclusion. Due to the strong π-backbonding interactions that dominate the Fe-cyanide interactions, linear Fe-C bonds are favoured and the carbon atoms are found to show a lower mobility compared to the nitrogen end of the ligand. This is expressed by the larger deviation from the ideal 180°angle in α(Fe ls 2+ -C-N) as compared to α(Fe hs 2+ -N-C). These calculated angular values are in great agreement with the experimental data.