Figure 4: A comparison of the atomic arrangements of the (401) Eu₂O₃ and (001) EuO planes.

(a) The crystal structure of the monoclinic polymorph of Eu₂O₃ viewed along the [010] zone axis. The unit cell of Eu₂O₃ is outlined with dashed lines and the (401) plane, which is viewed edge-on, is indicated by the blue line. (b) The atoms closest to the chosen (401) plane (the blue line) have overall composition EuO and form a closely packed layer. (c) The (401) plane of atoms selected in b viewed at normal incidence. The atomic arrangement is similar to that of the (001) EuO plane and can be made virtually identical by shifting the columns of atoms between the dashed lines in the direction of the yellow arrows by . (d) The (401) plane of Eu₂O₃ after performing the atomic shifts described in c. (e) The (001) EuO plane. (f) Emphasizes the similarity in atomic arrangement between d and e, by showing the overlap unit cell of shifted . The overlap unit cell between and (001)_EuO is also shown by the dashed quadrilateral (a rhombus for and a square for (001)_EuO) in c, before any shift of the atomic positions.