A systematic study of the distribution of the M-M distances in all the bina
ry, ternary and quaternary oxides of the rare earth elements (RE = Sc, Y, L
a-Lu), contained in the Inorganic Crystal Structure Database (ICSD) has bee
n carried out. The results indicate that the RE-RE distances are not distri
buted uniformly, but present maxima which are close to the corresponding di
stances in the pure metals. In some of the histograms (Y, Ce, Pr, Sm, Tb, D
y, Ho, Lu) two maxima appear which correspond to the nearest-neighbor (b.c.
c., h.c.p.) and second-nearest neighbor (b.c.c.) distances of the elemental
phases. As examples of this behavior, the cation arrays of the binary oxid
es, hydroxides and ternary oxides of both the delafossite and alpha-NaFeO2
type are analyzed. In all of them the cations form aggregates whose topolog
ies and distances can be related to the structure of the parent metals. The
size of the metal aggregates seems to decrease with increasing oxygen cont
ent.