For [7]helicene, only one Z ′ = 1 polymorph is lower in energy than the experimental Z ′ = 1 structure, and this discrepancy can be explained due to the chirality once again. The experimental structure is racemic, whereas the lowest energy Z ′ = 1 predicted structure is enantiopure. Typically, compounds that have a lower-energy enantiopure structure tend not to form racemic crystals, instead forming twinned crystals of different chirality, as seen for [6]helicene. However, for [7]helicene, the lowest energy racemic structure falls within the polymorphic region (<7.2 kJ mol -1 above the global minimum in 95% of cases) and its formation may be favoured due to kinetic reasons. The enantiopure Z ′ = 1 structure has not been realised experimentally, likely due to the global minimum corresponding to the enantiopure experimental polymorph (Z ′ = 2), which is thermodynamically favoured.