Generating polarisation via collective distortions of MX 3 framework is difficult as the conventional cooperative tilts of the MX 6 Fig. (a) Crystal structure of Fe[Bi(SCN) 6 ] viewed along the [110] direction . (b) Extended tolerance factor plot for A x M(NCS) 3 structures including known and target phases, with the M site cations shown in square brackets. The lower limit of τ = 0.8 is found not to hold for NCSperovskites [ESI Section 3].