As a more general representative example, the chiral compound chloro(fluoro)iodosilane was examined using 3a-R (having an Please do not adjust margins orientation as shown and corresponding to that in Fig. ) at a precisely tetrahedral T-4 configuration as the seed polytope. This system allows us to explore consequences of "non-idealised" geometries, distinct B-atoms, distinct A-B i bond lengths, and general issues concerning the molecular geometries near or at the "fusion" species. and their locations on the PES are displaced from these "idealised geometries". Despite this and unsurprisingly, the PES still closely resembles that for 1, this being in keeping with early empirical findings and discussions concerning the applicability of idealised polytopal forms for real chemical systems. The differing sizes of these real B-atoms (H, F, Cl, and I) of chlorofluoroiodosilane, in addition to the electronic effects they impose, lead to differing curvatures of the PESs' regions where close B i -B j steric interactions begin to dominate. In Fig. and Fig. , the omitted regions from the PES with energy values over 500 kJ mol -1 form three pairs with distinct extents which contrasts to those in Fig. and Fig. where all six regions are of identical extent.