Notes

1Table 2 is available in the online version of this article and from the IUCr electronic archives (Reference: HW0085 ). Services for accessing these data are described at the back of the journal.

2D[4,3] = [\textstyle\sum]Vidi/[\textstyle\sum]Vi, where Vi is the relative volume in group i and di is the mean group diameter.

3Figs. 8 to 15 are available in the online version of this article and from the IUCr electronic archives (Reference: HW0085) . Services for accessing these data are described at the back of the journal.