Fe7C3 crystallizes in the orthorhombic Pnma space group. There are five inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 3-coordinate geometry to one C(2) and two equivalent C(1) atoms. In the second Fe site, Fe(2) is bonded in a 3-coordinate geometry to one C(2) and two equivalent C(1) atoms. In the third Fe site, Fe(3) is bonded in a water-like geometry to two equivalent C(1) atoms. In the fourth Fe site, Fe(4) is bonded in a distorted trigonal planar geometry to one C(2) and two equivalent C(1) atoms. In the fifth Fe site, Fe(5) is bonded in a 4-coordinate geometry to two equivalent C(1) and two equivalent C(2) atoms. There are two inequivalent C sites. In the first C site, C(1) is bonded in a 7-coordinate geometry to one Fe(2), one Fe(3), one Fe(4), two equivalent Fe(1), and two equivalent Fe(5) atoms. In the second C site, C(2) is bonded in a 6-coordinate geometry to one Fe(2), one Fe(4), two equivalent Fe(1), and four equivalent Fe(5) atoms.
Fe7C3 crystallizes in the orthorhombic Pnma space group. There are five inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 3-coordinate geometry to one C(2) and two equivalent C(1) atoms. The Fe(1)-C(2) bond length is 2.03 Å. There is one shorter (1.97 Å) and one longer (2.04 Å) Fe(1)-C(1) bond length. In the second Fe site, Fe(2) is bonded in a 3-coordinate geometry to one C(2) and two equivalent C(1) atoms. The Fe(2)-C(2) bond length is 1.93 Å. Both Fe(2)-C(1) bond lengths are 1.98 Å. In the third Fe site, Fe(3) is bonded in a water-like geometry to two equivalent C(1) atoms. Both Fe(3)-C(1) bond lengths are 1.98 Å. In the fourth Fe site, Fe(4) is bonded in a distorted trigonal planar geometry to one C(2) and two equivalent C(1) atoms. The Fe(4)-C(2) bond length is 1.96 Å. Both Fe(4)-C(1) bond lengths are 1.99 Å. In the fifth Fe site, Fe(5) is bonded in a 4-coordinate geometry to two equivalent C(1) and two equivalent C(2) atoms. There is one shorter (2.05 Å) and one longer (2.23 Å) Fe(5)-C(1) bond length. There is one shorter (2.02 Å) and one longer (2.44 Å) Fe(5)-C(2) bond length. There are two inequivalent C sites. In the first C site, C(1) is bonded in a 7-coordinate geometry to one Fe(2), one Fe(3), one Fe(4), two equivalent Fe(1), and two equivalent Fe(5) atoms. In the second C site, C(2) is bonded in a 6-coordinate geometry to one Fe(2), one Fe(4), two equivalent Fe(1), and four equivalent Fe(5) atoms.