Synthesis and Crystal Structure of a New Orthorhombic Polytype of Potassium Ferricyanide

Abstract A new four‐layer orthorhombic polytype of potassium ferricyanide, K 3 Fe(CN) 6 , has been determined by single‐crystal X‐ray diffraction supported by powder X‐ray diffraction measurements. It crystallizes in the space group Pbcn with lattice parameters a = 10.3922(7) Å, b = 8.3508(5) Å, c = 26.838(2) Å and Z = 8, indicating a doubled orthorhombic cell along the c direction compared with the previously reported two‐layer orthorhombic polymorph. The structural relationship between these two forms is then discussed with the support of DFT calculations.