Table 1.

Lattice constants a, b, c and elastic moduli $C_{ij}$ of ${\alpha }^{\prime \prime }$-${\mathrm{Fe}}_{16}{\mathrm{C}}_2$ with carbon distributions I–IV (cf. Figure 3) as obtained from DFT calculations. The corresponding values for α-Fe and α-FeC₃ are given for comparison. The carbon distributions I-IV are ordered by relative energetic stability $\Delta E$ with respect to the most stable configuration I.

	α-Fe	α-FeC3	${\alpha }^{\prime \prime }$-Fe16C2-I	${\alpha }^{\prime \prime }$-Fe16C2-II	${\alpha }^{\prime \prime }$-Fe16C2-III	${\alpha }^{\prime \prime }$-Fe-Fe16C2-IV
a (Å)	5.67	7.86	5.66	5.62	5.63	5.07
b (Å)					5.66
c (Å)			6.25	6.33	6.27	7.50
$C_{11}$ (GPa)	278.2	251.7	269.3	276.7	265.3	215.7
$C_{22}$ (GPa)					278.1
$C_{33}$ (GPa)			297.5	289.9	288.4	238.5
$C_{12}$ (GPa)	147.8	204.1	144.3	143.3	128.5	171.1
$C_{13}$ (GPa)			149.4	151.9	153.5	148.2
$C_{23}$ (GPa)					137.1
$C_{44}$ (GPa)	95.1	30.6	94.5	95.1	93.5	14.8
$C_{55}$ (GPa)					80.1
$C_{66}$ (GPa)			123.1	123.1	99.0	–131.3
$\Delta E$ (meV/atom)			0	8	17	77