The symmetry of the convex hull is only 𝐷 2ℎ . By normalising all A-B i bond vectors, the resulting polytope is the square planar (SP-4) configuration of 𝐷 4ℎ symmetry as shown in Fig. . To formalise this approach mathematically, for a general coordination centre ABn ⊆ ℝ 3 , we normalise the A-B i bond vectors.