Materials Data on HfMg14SiO16 by Materials Project

Abstract

Mg14HfSiO16 is Caswellsilverite-derived structured and crystallizes in the orthorhombic Pmmm 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 a mixture of corner and edge-sharing MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Mg–O bond distances ranging from 1.95–2.23 Å. In the second Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with two equivalent HfO6 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 2.10–2.23 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 HfO6 octahedra, and edges with eight MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–8°. There are a spread of Mg–O bond distances ranging from 2.08–2.25 Å. In the fourth 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 0–4°. There are a spread of Mg–O bond distances ranging from 2.14–2.24 Å. In the fifth 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 0–11°. There are a spread of Mg–O bond distances ranging from 2.15–2.30 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 HfO6 octahedra, and edges with ten MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–5°. There are a spread of Mg–O bond distances ranging from 2.13–2.32 Å. In the seventh 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 0–11°. There are a spread of Mg–O bond distances ranging from 2.15–2.30 Å. In the eighth 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 HfO6 octahedra, and edges with ten MgO6 octahedra. The corner-sharing octahedra tilt angles range from 4–11°. There are a spread of Mg–O bond distances ranging from 2.10–2.31 Å. Hf is bonded to six O atoms to form HfO6 octahedra that share corners with two equivalent MgO6 octahedra, corners with two equivalent HfO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Hf–O bond distances ranging from 2.11–2.22 Å. Si is bonded in a distorted square co-planar geometry to four O atoms. There are two shorter (2.14 Å) and two longer (2.23 Å) Si–O bond lengths. There are nine inequivalent O sites. In the first O site, O is bonded to five Mg atoms to form distorted OMg5 square pyramids that share corners with six OHfMg5 octahedra, corners with three equivalent OMg5 square pyramids, and edges with eight OMg6 octahedra. The corner-sharing octahedra tilt angles range from 3–85°. In the second O site, O is bonded to five Mg and one Hf atom to form OHfMg5 octahedra that share corners with four equivalent OHfMg5 octahedra, corners with two equivalent OMg5 square pyramids, and edges with twelve OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–5°. 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 ten OHfMg5 octahedra, and edges with two equivalent OMg5 square pyramids. The corner-sharing octahedra tilt angles range from 1–6°. In the fourth O site, O is bonded to four Mg and two equivalent Si atoms to form OMg4Si2 octahedra that share corners with six OMg4Si2 octahedra, corners with four equivalent OMg5 square pyramids, and edges with eight OHfMg4Si octahedra. The corner-sharing octahedral tilt angles are 0°. In the fifth O site, O is bonded to four Mg and two equivalent Hf atoms to form OHf2Mg4 octahedra that share corners with six OMg4Si2 octahedra and edges with twelve OHfMg5 octahedra. 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 OMg4Si2 octahedra, edges with eight OMg6 octahedra, and edges with four equivalent OMg5 square pyramids. 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 OHf2Mg4 octahedra and edges with twelve OHfMg5 octahedra. The corner-sharing octahedral tilt angles are 0°. In the eighth O site, O is bonded to four Mg, one Hf, and one Si atom to form OHfMg4Si octahedra that share corners with six OHfMg4Si octahedra, corners with two equivalent OMg5 square pyramids, and edges with ten OMg4Si2 octahedra. The corner-sharing octahedra tilt angles range from 0–8°. In the ninth O site, O is bonded to six Mg atoms to form OMg6 octahedra that share corners with six OHfMg4Si octahedra, edges with ten OHfMg5 octahedra, and edges with two equivalent OMg5 square pyramids. The corner-sharing octahedra tilt angles range from 0–7°.