Mg14CrCO16 crystallizes in the tetragonal P4/mmm space group. There are six inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(5) atoms to form MgO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra; corners with two equivalent Cr(1)O6 octahedra; corners with two equivalent C(1)O6 octahedra; edges with four equivalent Mg(2)O6 octahedra; edges with four Mg(3,3)O6 octahedra; and edges with four equivalent Mg(4)O6 octahedra. The corner-sharing octahedra are not tilted. In the second Mg site, Mg(2) is bonded to one O(4), one O(5), two equivalent O(1), and two equivalent O(3) atoms to form MgO6 octahedra that share corners with two equivalent Mg(3)O6 octahedra; corners with four equivalent Mg(2)O6 octahedra; edges with two equivalent Mg(1)O6 octahedra; edges with two equivalent Mg(2)O6 octahedra; edges with two Mg(3,3)O6 octahedra; edges with two equivalent Cr(1)O6 octahedra; and edges with four equivalent Mg(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. In the third Mg site, Mg(3) is bonded to one O(5), one O(6), two equivalent O(2), and two equivalent O(3) atoms to form MgO6 octahedra that share corners with two equivalent Mg(2)O6 octahedra; corners with four Mg(3,3)O6 octahedra; edges with two equivalent Mg(1)O6 octahedra; edges with two equivalent Mg(2)O6 octahedra; edges with two Mg(3,3)O6 octahedra; edges with two equivalent C(1)O6 octahedra; and edges with four equivalent Mg(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-5°. In the fourth Mg site, Mg(3) is bonded to one O(5), one O(6), two equivalent O(2), and two equivalent O(3) atoms to form MgO6 octahedra that share corners with two equivalent Mg(2)O6 octahedra; corners with four Mg(3,3)O6 octahedra; edges with two equivalent Mg(1)O6 octahedra; edges with two equivalent Mg(2)O6 octahedra; edges with two Mg(3,3)O6 octahedra; edges with two equivalent C(1)O6 octahedra; and edges with four equivalent Mg(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-5°. In the fifth Mg site, Mg(3) is bonded to one O(5), one O(6), two equivalent O(2), and two equivalent O(3) atoms to form MgO6 octahedra that share corners with two equivalent Mg(2)O6 octahedra; corners with four Mg(3,3)O6 octahedra; edges with two equivalent Mg(1)O6 octahedra; edges with two equivalent Mg(2)O6 octahedra; edges with two Mg(3,3)O6 octahedra; edges with two equivalent C(1)O6 octahedra; and edges with four equivalent Mg(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-5°. In the sixth Mg site, Mg(4) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form MgO6 octahedra that share corners with six equivalent Mg(4)O6 octahedra,  an edgeedge with one Cr(1)O6 octahedra,  an edgeedge with one C(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with four equivalent Mg(2)O6 octahedra, and edges with four equivalent Mg(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 2-4°. Cr(1) is bonded to two equivalent O(4) and four equivalent O(1) atoms to form CrO6 octahedra that share corners with two equivalent Cr(1)O6 octahedra, corners with four equivalent Mg(1)O6 octahedra, edges with four equivalent Mg(4)O6 octahedra, and edges with eight equivalent Mg(2)O6 octahedra. The corner-sharing octahedra are not tilted. C(1) is bonded to two equivalent O(6) and four equivalent O(2) atoms to form distorted CO6 octahedra that share corners with two equivalent C(1)O6 octahedra; corners with four equivalent Mg(1)O6 octahedra; edges with four equivalent Mg(4)O6 octahedra; and edges with eight Mg(3,3,3)O6 octahedra. The corner-sharing octahedra are not tilted. There are six inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), two equivalent Mg(2), two equivalent Mg(4), and one Cr(1) atom to form OMg5Cr octahedra that share corners with four equivalent O(1)Mg5Cr octahedra, corners with two equivalent O(2)Mg5C square pyramids, edges with two equivalent O(4)Mg4Cr2 octahedra, edges with two equivalent O(1)Mg5Cr octahedra, edges with two equivalent O(5)Mg6 octahedra, edges with four equivalent O(3)Mg6 octahedra, and edges with two equivalent O(2)Mg5C square pyramids. The corner-sharing octahedral tilt angles range from 0-1°. In the second O site, O(2) is bonded to one Mg(1), two equivalent Mg(3), two equivalent Mg(4), and one C(1) atom to form OMg5C square pyramids that share corners with two equivalent O(1)Mg5Cr octahedra, corners with four equivalent O(2)Mg5C square pyramids, edges with two equivalent O(1)Mg5Cr octahedra, edges with two equivalent O(5)Mg6 octahedra, edges with four equivalent O(3)Mg6 octahedra, and edges with two equivalent O(2)Mg5C square pyramids. The corner-sharing octahedral tilt angles are 3°. In the third O site, O(3) is bonded to two equivalent Mg(2), two equivalent Mg(3), and two equivalent Mg(4) atoms to form OMg6 octahedra that share corners with six equivalent O(3)Mg6 octahedra,  an edgeedge with one O(4)Mg4Cr2 octahedra, edges with two equivalent O(5)Mg6 octahedra, edges with four equivalent O(1)Mg5Cr octahedra, and edges with four equivalent O(2)Mg5C square pyramids. The corner-sharing octahedral tilt angles range from 1-3°. In the fourth O site, O(4) is bonded to four equivalent Mg(2) and two equivalent Cr(1) atoms to form OMg4Cr2 octahedra that share corners with two equivalent O(4)Mg4Cr2 octahedra, corners with four equivalent O(5)Mg6 octahedra, edges with four equivalent O(3)Mg6 octahedra, and edges with eight equivalent O(1)Mg5Cr octahedra. The corner-sharing octahedra are not tilted. In the fifth O site, O(5) is bonded to two equivalent Mg(1); two equivalent Mg(2); and two Mg(3,3) atoms to form OMg6 octahedra that share corners with two equivalent O(4)Mg4Cr2 octahedra, corners with two equivalent O(5)Mg6 octahedra, edges with four equivalent O(1)Mg5Cr octahedra, edges with four equivalent O(3)Mg6 octahedra, and edges with four equivalent O(2)Mg5C square pyramids. The corner-sharing octahedra are not tilted. In the sixth O site, O(6) is bonded in a distorted square co-planar geometry to four Mg(3,3,3) and two equivalent C(1) atoms.
Mg14CrCO16 crystallizes in the tetragonal P4/mmm space group. There are six inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(5) atoms to form MgO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra; corners with two equivalent Cr(1)O6 octahedra; corners with two equivalent C(1)O6 octahedra; edges with four equivalent Mg(2)O6 octahedra; edges with four Mg(3,3)O6 octahedra; and edges with four equivalent Mg(4)O6 octahedra. The corner-sharing octahedra are not tilted. Both Mg(1)-O(1) bond lengths are 2.13 Å. Both Mg(1)-O(2) bond lengths are 2.08 Å. Both Mg(1)-O(5) bond lengths are 2.15 Å. In the second Mg site, Mg(2) is bonded to one O(4), one O(5), two equivalent O(1), and two equivalent O(3) atoms to form MgO6 octahedra that share corners with two equivalent Mg(3)O6 octahedra; corners with four equivalent Mg(2)O6 octahedra; edges with two equivalent Mg(1)O6 octahedra; edges with two equivalent Mg(2)O6 octahedra; edges with two Mg(3,3)O6 octahedra; edges with two equivalent Cr(1)O6 octahedra; and edges with four equivalent Mg(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. The Mg(2)-O(4) bond length is 2.14 Å. The Mg(2)-O(5) bond length is 2.11 Å. Both Mg(2)-O(1) bond lengths are 2.15 Å. Both Mg(2)-O(3) bond lengths are 2.12 Å. In the third Mg site, Mg(3) is bonded to one O(5), one O(6), two equivalent O(2), and two equivalent O(3) atoms to form MgO6 octahedra that share corners with two equivalent Mg(2)O6 octahedra; corners with four Mg(3,3)O6 octahedra; edges with two equivalent Mg(1)O6 octahedra; edges with two equivalent Mg(2)O6 octahedra; edges with two Mg(3,3)O6 octahedra; edges with two equivalent C(1)O6 octahedra; and edges with four equivalent Mg(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-5°. The Mg(3)-O(5) bond length is 2.17 Å. The Mg(3)-O(6) bond length is 2.08 Å. Both Mg(3)-O(2) bond lengths are 2.15 Å. Both Mg(3)-O(3) bond lengths are 2.12 Å. In the fourth Mg site, Mg(3) is bonded to one O(5), one O(6), two equivalent O(2), and two equivalent O(3) atoms to form MgO6 octahedra that share corners with two equivalent Mg(2)O6 octahedra; corners with four Mg(3,3)O6 octahedra; edges with two equivalent Mg(1)O6 octahedra; edges with two equivalent Mg(2)O6 octahedra; edges with two Mg(3,3)O6 octahedra; edges with two equivalent C(1)O6 octahedra; and edges with four equivalent Mg(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-5°. The Mg(3)-O(5) bond length is 2.17 Å. The Mg(3)-O(6) bond length is 2.08 Å. Both Mg(3)-O(2) bond lengths are 2.15 Å. Both Mg(3)-O(3) bond lengths are 2.12 Å. In the fifth Mg site, Mg(3) is bonded to one O(5), one O(6), two equivalent O(2), and two equivalent O(3) atoms to form MgO6 octahedra that share corners with two equivalent Mg(2)O6 octahedra; corners with four Mg(3,3)O6 octahedra; edges with two equivalent Mg(1)O6 octahedra; edges with two equivalent Mg(2)O6 octahedra; edges with two Mg(3,3)O6 octahedra; edges with two equivalent C(1)O6 octahedra; and edges with four equivalent Mg(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-5°. The Mg(3)-O(5) bond length is 2.17 Å. The Mg(3)-O(6) bond length is 2.08 Å. Both Mg(3)-O(2) bond lengths are 2.15 Å. Both Mg(3)-O(3) bond lengths are 2.12 Å. In the sixth Mg site, Mg(4) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form MgO6 octahedra that share corners with six equivalent Mg(4)O6 octahedra,  an edgeedge with one Cr(1)O6 octahedra,  an edgeedge with one C(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with four equivalent Mg(2)O6 octahedra, and edges with four equivalent Mg(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 2-4°. Both Mg(4)-O(1) bond lengths are 2.16 Å. Both Mg(4)-O(2) bond lengths are 2.09 Å. Both Mg(4)-O(3) bond lengths are 2.15 Å. Cr(1) is bonded to two equivalent O(4) and four equivalent O(1) atoms to form CrO6 octahedra that share corners with two equivalent Cr(1)O6 octahedra, corners with four equivalent Mg(1)O6 octahedra, edges with four equivalent Mg(4)O6 octahedra, and edges with eight equivalent Mg(2)O6 octahedra. The corner-sharing octahedra are not tilted. Both Cr(1)-O(4) bond lengths are 2.15 Å. All Cr(1)-O(1) bond lengths are 2.11 Å. C(1) is bonded to two equivalent O(6) and four equivalent O(2) atoms to form distorted CO6 octahedra that share corners with two equivalent C(1)O6 octahedra; corners with four equivalent Mg(1)O6 octahedra; edges with four equivalent Mg(4)O6 octahedra; and edges with eight Mg(3,3,3)O6 octahedra. The corner-sharing octahedra are not tilted. Both C(1)-O(6) bond lengths are 2.15 Å. All C(1)-O(2) bond lengths are 2.17 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), two equivalent Mg(2), two equivalent Mg(4), and one Cr(1) atom to form OMg5Cr octahedra that share corners with four equivalent O(1)Mg5Cr octahedra, corners with two equivalent O(2)Mg5C square pyramids, edges with two equivalent O(4)Mg4Cr2 octahedra, edges with two equivalent O(1)Mg5Cr octahedra, edges with two equivalent O(5)Mg6 octahedra, edges with four equivalent O(3)Mg6 octahedra, and edges with two equivalent O(2)Mg5C square pyramids. The corner-sharing octahedral tilt angles range from 0-1°. In the second O site, O(2) is bonded to one Mg(1), two equivalent Mg(3), two equivalent Mg(4), and one C(1) atom to form OMg5C square pyramids that share corners with two equivalent O(1)Mg5Cr octahedra, corners with four equivalent O(2)Mg5C square pyramids, edges with two equivalent O(1)Mg5Cr octahedra, edges with two equivalent O(5)Mg6 octahedra, edges with four equivalent O(3)Mg6 octahedra, and edges with two equivalent O(2)Mg5C square pyramids. The corner-sharing octahedral tilt angles are 3°. In the third O site, O(3) is bonded to two equivalent Mg(2), two equivalent Mg(3), and two equivalent Mg(4) atoms to form OMg6 octahedra that share corners with six equivalent O(3)Mg6 octahedra,  an edgeedge with one O(4)Mg4Cr2 octahedra, edges with two equivalent O(5)Mg6 octahedra, edges with four equivalent O(1)Mg5Cr octahedra, and edges with four equivalent O(2)Mg5C square pyramids. The corner-sharing octahedral tilt angles range from 1-3°. In the fourth O site, O(4) is bonded to four equivalent Mg(2) and two equivalent Cr(1) atoms to form OMg4Cr2 octahedra that share corners with two equivalent O(4)Mg4Cr2 octahedra, corners with four equivalent O(5)Mg6 octahedra, edges with four equivalent O(3)Mg6 octahedra, and edges with eight equivalent O(1)Mg5Cr octahedra. The corner-sharing octahedra are not tilted. In the fifth O site, O(5) is bonded to two equivalent Mg(1); two equivalent Mg(2); and two Mg(3,3) atoms to form OMg6 octahedra that share corners with two equivalent O(4)Mg4Cr2 octahedra, corners with two equivalent O(5)Mg6 octahedra, edges with four equivalent O(1)Mg5Cr octahedra, edges with four equivalent O(3)Mg6 octahedra, and edges with four equivalent O(2)Mg5C square pyramids. The corner-sharing octahedra are not tilted. In the sixth O site, O(6) is bonded in a distorted square co-planar geometry to four Mg(3,3,3) and two equivalent C(1) atoms.