The (2kl) plane at 84 K for (a) the ordered LS phase (LS-ord) and (b) the disordered phase (LS-dis). In the ordered phase (a) the marked reflections can all be indexed with integer hkl values in the hexagonal phase. (b) Triclinic indices of split main reflections and new non-split reflections. The split reflections correspond to two slightly separated reflections from all three twins, while the non-split reflections correspond to just one of the three twins. This latter group lies at k + ½ in the hexagonal reciprocal lattice.