For our analysis of these four in situ datasets, we tracked the change in area of specific key peaks in the XPDF [Figure ]. Based on our analysis of the room-temperature DFW 65:25:10 dataset [see Figures ], we established that the area under the peak at 3.5 Å (the nearest neighbour Hf-Hf) is larger for the hexamer than for the tetramer. In all our in situ reactions the area under this peak initially increases, corresponding to a reduction in the proportion of tetramer. This is further corroborated by the increase in the area under the peak at 4.9 Å at the start of the reaction, corresponding to an increase in the amount of next-nearest neighbour Hf-Hf interactions, which also indicates the formation of clusters other than the tetramer. The growth of the peaks at 3.5 and 4.9 Å indicates species of higher nuclearity than the tetramer are forming, but cannot distinguish between the growth of single cluster and the Hf12 double cluster. However, these peaks generally precede the growth of the peak at 9.2 Å, which is only seen in the Hf12 double cluster [Figure ],