Mg6NbC crystallizes in the orthorhombic Amm2 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 11-coordinate geometry to one Mg(1), two equivalent Mg(2), two equivalent Mg(4), four equivalent Mg(3), and two equivalent Nb(1) atoms. In the second Mg site, Mg(2) is bonded in a 10-coordinate geometry to two equivalent Mg(4), four equivalent Mg(1), and four equivalent Mg(3) atoms. In the third Mg site, Mg(3) is bonded in a single-bond geometry to two equivalent Mg(2), four equivalent Mg(1), and one C(1) atom. In the fourth Mg site, Mg(4) is bonded in a single-bond geometry to two equivalent Mg(2), four equivalent Mg(1), and one C(1) atom. Nb(1) is bonded in a linear geometry to four equivalent Mg(1) and two equivalent C(1) atoms. C(1) is bonded to one Mg(4), two equivalent Mg(3), and two equivalent Nb(1) atoms to form corner-sharing CMg3Nb2 square pyramids.
Mg6NbC crystallizes in the orthorhombic Amm2 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 11-coordinate geometry to one Mg(1), two equivalent Mg(2), two equivalent Mg(4), four equivalent Mg(3), and two equivalent Nb(1) atoms. The Mg(1)-Mg(1) bond length is 3.02 Å. There is one shorter (3.08 Å) and one longer (3.31 Å) Mg(1)-Mg(2) bond length. Both Mg(1)-Mg(4) bond lengths are 3.26 Å. There are two shorter (3.27 Å) and two longer (3.37 Å) Mg(1)-Mg(3) bond lengths. There is one shorter (3.07 Å) and one longer (3.26 Å) Mg(1)-Nb(1) bond length. In the second Mg site, Mg(2) is bonded in a 10-coordinate geometry to two equivalent Mg(4), four equivalent Mg(1), and four equivalent Mg(3) atoms. Both Mg(2)-Mg(4) bond lengths are 3.02 Å. All Mg(2)-Mg(3) bond lengths are 2.89 Å. In the third Mg site, Mg(3) is bonded in a single-bond geometry to two equivalent Mg(2), four equivalent Mg(1), and one C(1) atom. The Mg(3)-C(1) bond length is 2.12 Å. In the fourth Mg site, Mg(4) is bonded in a single-bond geometry to two equivalent Mg(2), four equivalent Mg(1), and one C(1) atom. The Mg(4)-C(1) bond length is 2.21 Å. Nb(1) is bonded in a linear geometry to four equivalent Mg(1) and two equivalent C(1) atoms. Both Nb(1)-C(1) bond lengths are 2.21 Å. C(1) is bonded to one Mg(4), two equivalent Mg(3), and two equivalent Nb(1) atoms to form corner-sharing CMg3Nb2 square pyramids.