DOE OSTI2020
Mg30WBO32 is Molybdenum Carbide MAX Phase-derived structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. there are eight 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 MgO6 octahedra, corners with two equivalent WO6 octahedra, corners with two equivalent BO6 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 2.01–2.16 Å. In the second Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with two equivalent WO6 octahedra, corners with four equivalent MgO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (2.10 Å) and four longer (2.13 Å) Mg–O bond lengths. In the third Mg site, Mg is bonded to six O atoms to form a mixture of corner and edge-sharing MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.12 Å) and two longer (2.15 Å) Mg–O bond lengths. In the fourth Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with two equivalent BO6 octahedra, corners with four equivalent MgO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (2.02 Å) and four longer (2.16 Å) Mg–O bond lengths. In the fifth Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with six MgO6 octahedra, an edgeedge with one WO6 octahedra, an edgeedge with one BO6 octahedra, and edges with ten MgO6 octahedra. The corner-sharing octahedra tilt angles range from 2–11°. There are a spread of Mg–O bond distances ranging from 2.09–2.21 Å. In the sixth Mg site, Mg is bonded to six O atoms to form a mixture of corner and edge-sharing MgO6 octahedra. The corner-sharing octahedra tilt angles range from 1–3°. There are two shorter (2.13 Å) and four longer (2.15 Å) Mg–O bond lengths. In the seventh Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with six MgO6 octahedra, an edgeedge with one WO6 octahedra, and edges with eleven MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–3°. There are a spread of Mg–O bond distances ranging from 2.10–2.19 Å. In the eighth Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with six MgO6 octahedra, an edgeedge with one BO6 octahedra, and edges with eleven MgO6 octahedra. The corner-sharing octahedra tilt angles range from 2–9°. There are a spread of Mg–O bond distances ranging from 2.12–2.17 Å. W is bonded to six O atoms to form WO6 octahedra that share corners with six MgO6 octahedra and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.17 Å) and two longer (2.18 Å) W–O bond lengths. B is bonded to six O atoms to form distorted BO6 octahedra that share corners with six MgO6 octahedra and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (2.26 Å) and four longer (2.27 Å) B–O bond lengths. There are twelve inequivalent O sites. In the first O site, O is bonded to five Mg and one W atom to form a mixture of corner and edge-sharing OMg5W octahedra. The corner-sharing octahedral tilt angles are 0°. In the second O site, O is bonded to six Mg atoms to form OMg6 octahedra that share corners with four OMg5W octahedra, corners with two equivalent OMg5B square pyramids, edges with ten OMg6 octahedra, and edges with two OMg5B square pyramids. The corner-sharing octahedral tilt angles are 0°. In the third O site, O is bonded to five Mg and one B atom to form distorted OMg5B square pyramids that share corners with four equivalent OMg6 octahedra, corners with two equivalent OMg5B square pyramids, edges with eight OMg6 octahedra, and edges with four OMg5B square pyramids. The corner-sharing octahedral tilt angles are 5°. In the fourth O site, O is bonded to six Mg atoms to form OMg6 octahedra that share corners with four OMg5W octahedra, corners with two equivalent OMg5B square pyramids, edges with ten OMg6 octahedra, and edges with two OMg5B square pyramids. The corner-sharing octahedral tilt angles are 0°. There are two shorter (2.10 Å) and two longer (2.17 Å) O–Mg bond lengths. In the fifth O site, O is bonded to six Mg atoms to form OMg6 octahedra that share corners with six equivalent OMg6 octahedra, edges with nine OMg5W octahedra, and edges with three OMg5B square pyramids. The corner-sharing octahedra tilt angles range from 1–5°. In the sixth O site, O is bonded to five Mg and one W atom to form OMg5W octahedra that share corners with four OMg5W octahedra, corners with two equivalent OMg5B square pyramids, edges with ten OMg5W octahedra, and edges with two OMg5B square pyramids. The corner-sharing octahedra tilt angles range from 0–2°. In the seventh O site, O is bonded to five Mg and one B atom to form distorted OMg5B square pyramids that share corners with four OMg5W octahedra, corners with two equivalent OMg5B square pyramids, edges with eight OMg6 octahedra, and edges with four OMg5B square pyramids. The corner-sharing octahedral tilt angles are 6°. The O–Mg bond length is 2.01 Å. In the eighth O site, O is bonded to five Mg and one B atom to form distorted OMg5B square pyramids that share corners with four OMg5W octahedra, corners with two equivalent OMg5B square pyramids, edges with eight OMg6 octahedra, and edges with four OMg5B square pyramids. The corner-sharing octahedral tilt angles are 6°. There are a spread of O–Mg bond distances ranging from 2.01–2.13 Å. In the ninth O site, O is bonded to six Mg atoms to form a mixture of corner and edge-sharing OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–2°. In the tenth O site, O is bonded to six Mg atoms to form OMg6 octahedra that share corners with four OMg6 octahedra, corners with two equivalent OMg5B square pyramids, edges with ten OMg6 octahedra, and edges with two equivalent OMg5B square pyramids. The corner-sharing octahedra tilt angles range from 0–2°. In the eleventh O site, O is bonded to five Mg and one B atom to form distorted OMg5B square pyramids that share corners with four OMg5W octahedra, corners with two equivalent OMg5B square pyramids, edges with eight OMg6 octahedra, and edges with four OMg5B square pyramids. The corner-sharing octahedral tilt angles are 6°. Both O–Mg bond lengths are 2.13 Å. In the twelfth O site, O is bonded to five Mg and one B atom to form distorted OMg5B square pyramids that share corners with four OMg5W octahedra, corners with two equivalent OMg5B square pyramids, edges with eight OMg6 octahedra, and edges with four OMg5B square pyramids. The corner-sharing octahedral tilt angles are 6°. There are two shorter (2.09 Å) and two longer (2.13 Å) O–Mg bond lengths.