Fig. 2: Unit cell volume per formula unit (V/Z) as a function of pressure for Fe0.94O polymorphs.
From: Monoclinic distortion and magnetic transitions in FeO under pressure and temperature

B1-cubic phase (Z = 4), rB1-rhombohedral phase (Z = 3), mC4-monoclinic phase refined in C2/m space group (Z = 2), mP4-monoclinic phase with P21/m phase space group (Z = 2) obtained after the laser heating, SC-single crystal. Experimental data from ref. 23 are shown for the comparison. Error bars, estimated standard deviations of fittings, are smaller than the symbol size for both pressure and volume.