The presence of both parent phase and intergrowth phase layers alongside the collapsed phase layers tallies with our stacking fault analysis of the XRD. Knowing the identity of the layer types, we attempted Rietveld refinements explicitly taking the presence of these residual Cu and Li layers into account. A custom-built code generated ~20000 unique 1500-layer supercell models containing combinations of the parent, intergrowth, and collapsed structures in an order determined by certain probabilities of transitioning from one to each of the others. Each of these base supercell models were refined against the data, in a procedure (see supporting information) similar to that of Bette et al. However, this did not produce convincing fits. Thus there is no single set of parameters to define the homogeneous mixing between the three phases at any given point. Instead the data are more consistent with each crystallite containing some regions which are highly mixed and some which are sparsely mixed. This is consistent with the inhomogeneous Cu distribution in the EDX mapping of Fig. : Point 1 with a composition of 0.05 Cu per Mn might be dominated by the collapsed phase while Point 2 with 0.3 Cu per Mn might be a highly mixed region of the three phases.