Figure 3.

Simulation cells of ${\alpha }^{\prime \prime }$-${\mathrm{Fe}}_{16}{\mathrm{C}}_2$ with different arrangements of carbon atoms (black) in the BCC lattice of Fe atoms (brown) used in the density-functional theory (DFT) calculations. The ordering of configuration I (a) to configuration IV (d) reflects the energetic ordering of most stable to least stable (cf. Table 1).