Fig. 3
Examples of reciprocal lattice planes (hkl) of Fe4O5. These plots correspond to different pressure and temperature conditions (indicated for each plot). a Basic reflections corresponding to the original Fe4O5-I structure, highlighted by red circles. b, c Emergence of superlattice reflections, highlighted by blue circles (in b these reflections are rather weak and blurred, but in c they are strong and clear). d Reconstruction of (hkl) reciprocal lattice planes, which reveals two possible unit cells of Fe4O5-III. The first option is an orthorhombic C-centered “average” cell, shown in the upper left corner together with its modulation wave vector q (Fe4O5-III-b). The second option is a C-centered unit cell with a tripled lattice parameter a, compared to the average cell (Fe4O5-III-a), highlighted at the bottom of the plot
