Fig. 3
From: Stability and nature of the volume collapse of ε-Fe2O3 under extreme conditions

Analysis of the volume and the quadratic elongation of the polyhedral units under pressure. Representation of the evolution under compression of theoretically simulated a polyhedral unit volume and b quadratic elongation of polyhedral units around Fe(1) (black circle), Fe(2) (green diamond), Fe(3) (red triangle down) and Fe(4) (blue triangle up before 40 GPa and blue square after 30 GPa)