DOE OSTI2020
Mg14AlCO16 crystallizes in the orthorhombic Pmmm space group. The structure is three-dimensional. there are nine inequivalent Mg sites. In the first Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with two equivalent AlO6 octahedra, corners with four MgO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Mg–O bond distances ranging from 2.10–2.19 Å. In the second Mg site, Mg is bonded to six O atoms to form a mixture of edge and corner-sharing MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Mg–O bond distances ranging from 2.06–2.20 Å. In the third Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with six MgO6 octahedra, edges with two equivalent AlO6 octahedra, and edges with eight MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–22°. There are a spread of Mg–O bond distances ranging from 2.10–2.21 Å. In the fourth Mg site, Mg is bonded to six O atoms to form a mixture of edge and corner-sharing MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–2°. There are a spread of Mg–O bond distances ranging from 2.10–2.19 Å. In the fifth Mg site, Mg is bonded to six O atoms to form a mixture of edge and corner-sharing MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–2°. There are a spread of Mg–O bond distances ranging from 2.10–2.19 Å. In the sixth Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with six MgO6 octahedra, edges with two equivalent AlO6 octahedra, and edges with ten MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–4°. There are a spread of Mg–O bond distances ranging from 2.10–2.18 Å. In the seventh Mg site, Mg is bonded to six O atoms to form a mixture of edge and corner-sharing MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–4°. There are a spread of Mg–O bond distances ranging from 2.07–2.16 Å. In the eighth Mg site, Mg is bonded to six O atoms to form a mixture of edge and corner-sharing MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–4°. There are a spread of Mg–O bond distances ranging from 2.07–2.16 Å. In the ninth Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with six equivalent MgO6 octahedra, an edgeedge with one AlO6 octahedra, and edges with ten MgO6 octahedra. The corner-sharing octahedra tilt angles range from 2–22°. There are a spread of Mg–O bond distances ranging from 2.10–2.21 Å. Al is bonded to six O atoms to form AlO6 octahedra that share corners with two equivalent MgO6 octahedra, corners with two equivalent AlO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Al–O bond distances ranging from 1.81–2.10 Å. C is bonded in a distorted square co-planar geometry to four O atoms. There are two shorter (2.10 Å) and two longer (2.15 Å) C–O bond lengths. There are nine inequivalent O sites. In the first O site, O is bonded to five Mg and one Al atom to form OMg5Al octahedra that share corners with four equivalent OMg5Al octahedra, corners with two equivalent OMg5C square pyramids, edges with ten OMg6 octahedra, and edges with two equivalent OMg4Al square pyramids. The corner-sharing octahedra tilt angles range from 0–4°. In the second O site, O is bonded to five Mg and one C atom to form distorted OMg5C square pyramids that share corners with two equivalent OMg5Al octahedra, corners with six OMg5C square pyramids, and edges with ten OMg4C2 octahedra. The corner-sharing octahedral tilt angles are 1°. In the third O site, O is bonded to six Mg atoms to form OMg6 octahedra that share corners with six equivalent OMg6 octahedra, edges with eight OMg5Al octahedra, and edges with four OMg5C square pyramids. The corner-sharing octahedra tilt angles range from 0–2°. In the fourth O site, O is bonded to four Mg and two equivalent Al atoms to form OMg4Al2 octahedra that share corners with six OMg4Al2 octahedra, edges with eight OMg5Al octahedra, and edges with four equivalent OMg4Al square pyramids. The corner-sharing octahedral tilt angles are 0°. In the fifth O site, O is bonded to four Mg and two equivalent C atoms to form distorted OMg4C2 octahedra that share corners with six OMg4Al2 octahedra, corners with four equivalent OMg4Al square pyramids, edges with four equivalent OMg6 octahedra, and edges with four equivalent OMg5C square pyramids. The corner-sharing octahedral tilt angles are 0°. In the sixth O site, O is bonded to six Mg atoms to form OMg6 octahedra that share corners with six OMg4Al2 octahedra and edges with twelve OMg5Al octahedra. The corner-sharing octahedral tilt angles are 0°. In the seventh O site, O is bonded to six Mg atoms to form OMg6 octahedra that share corners with six OMg4C2 octahedra, edges with eight OMg6 octahedra, and edges with four equivalent OMg5C square pyramids. The corner-sharing octahedral tilt angles are 0°. In the eighth O site, O is bonded to four Mg and one Al atom to form distorted OMg4Al square pyramids that share corners with four OMg6 octahedra, corners with five OMg5C square pyramids, and edges with eight OMg5Al octahedra. The corner-sharing octahedra tilt angles range from 13–79°. In the ninth O site, O is bonded to six Mg atoms to form OMg6 octahedra that share corners with four equivalent OMg6 octahedra, corners with two equivalent OMg4Al square pyramids, edges with ten OMg5Al octahedra, and edges with two equivalent OMg5C square pyramids. The corner-sharing octahedra tilt angles range from 0–2°.