DOI: 10.17188/1745702
title: Materials Data on RbHfMg14O15 by Materials Project

description: RbMg14HfO15 crystallizes in the orthorhombic Pmm2 space group. The structure is three-dimensional. Rb is bonded in a 4-coordinate geometry to four O atoms. There are two shorter (2.60 Å) and two longer (2.73 Å) Rb–O bond lengths. There are ten inequivalent Mg sites. In the first Mg site, Mg is bonded to five O atoms to form MgO5 square pyramids that share corners with four MgO5 square pyramids and edges with eight MgO6 octahedra. There are a spread of Mg–O bond distances ranging from 1.99–2.17 Å. In the second Mg site, Mg is bonded to five O atoms to form MgO5 square pyramids that share corners with four MgO5 square pyramids and edges with eight MgO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.01–2.10 Å. In the third Mg site, Mg is bonded to five O atoms to form MgO5 square pyramids that share a cornercorner with one MgO6 octahedra, corners with four equivalent MgO5 square pyramids, edges with four MgO6 octahedra, and edges with two equivalent HfO5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 4°. There are a spread of Mg–O bond distances ranging from 1.97–2.29 Å. In the fourth Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with four equivalent MgO6 octahedra, a cornercorner with one MgO5 square pyramid, edges with four MgO6 octahedra, and edges with four MgO5 square pyramids. The corner-sharing octahedra tilt angles range from 0–3°. There are a spread of Mg–O bond distances ranging from 2.06–2.29 Å. In the fifth Mg site, Mg is bonded in a T-shaped geometry to three O atoms. There are one shorter (2.06 Å) and two longer (2.18 Å) Mg–O bond lengths. In the sixth Mg site, Mg is bonded in a 5-coordinate geometry to five O atoms. There are a spread of Mg–O bond distances ranging from 2.08–2.67 Å. In the seventh Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with four MgO6 octahedra, edges with six MgO6 octahedra, and edges with four MgO5 square pyramids. The corner-sharing octahedra tilt angles range from 0–13°. There are a spread of Mg–O bond distances ranging from 2.04–2.30 Å. In the eighth Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with four MgO6 octahedra, corners with two equivalent HfO5 trigonal bipyramids, edges with six MgO6 octahedra, and edges with four MgO5 square pyramids. The corner-sharing octahedra tilt angles range from 0–2°. There are a spread of Mg–O bond distances ranging from 2.07–2.55 Å. In the ninth Mg site, Mg is bonded in a see-saw-like geometry to four O atoms. There are a spread of Mg–O bond distances ranging from 2.09–2.39 Å. In the tenth Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with four equivalent MgO6 octahedra, a cornercorner with one HfO5 trigonal bipyramid, edges with six MgO6 octahedra, and edges with four MgO5 square pyramids. The corner-sharing octahedra tilt angles range from 4–14°. There are a spread of Mg–O bond distances ranging from 2.09–2.37 Å. Hf is bonded to five O atoms to form distorted HfO5 trigonal bipyramids that share corners with four MgO6 octahedra, corners with two equivalent HfO5 trigonal bipyramids, and edges with four equivalent MgO5 square pyramids. The corner-sharing octahedra tilt angles range from 59–77°. There are a spread of Hf–O bond distances ranging from 2.01–2.14 Å. There are eleven inequivalent O sites. In the first O site, O is bonded in a 5-coordinate geometry to four Mg and one Hf atom. In the second O site, O is bonded to five Mg atoms to form OMg5 square pyramids that share corners with four OMg5 square pyramids, corners with two equivalent ORb2Mg3 trigonal bipyramids, and edges with eight OMg6 octahedra. In the third O site, O is bonded to five Mg atoms to form OMg5 square pyramids that share corners with four OMg5 square pyramids, corners with two equivalent OHf2Mg3 trigonal bipyramids, and edges with eight OMg6 octahedra. In the fourth O site, O is bonded to five Mg atoms to form OMg5 square pyramids that share a cornercorner with one OMg6 octahedra, corners with four equivalent OMg5 square pyramids, and edges with four OMg6 octahedra. The corner-sharing octahedral tilt angles are 0°. In the fifth O site, O is bonded to six Mg atoms to form OMg6 octahedra that share corners with four equivalent OMg6 octahedra, a cornercorner with one OMg5 square pyramid, edges with four OMg6 octahedra, edges with four OMg5 square pyramids, and edges with two ORb2Mg3 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 1–4°. In the sixth O site, O is bonded to two equivalent Rb and three Mg atoms to form ORb2Mg3 trigonal bipyramids that share a cornercorner with one OMg6 octahedra, corners with two equivalent OMg5 square pyramids, corners with four OHf2Mg3 trigonal bipyramids, and edges with two equivalent OMg6 octahedra. The corner-sharing octahedral tilt angles are 0°. In the seventh O site, O is bonded to three Mg and two equivalent Hf atoms to form distorted OHf2Mg3 trigonal bipyramids that share a cornercorner with one OMg6 octahedra, corners with two equivalent OMg5 square pyramids, corners with four ORb2Mg3 trigonal bipyramids, and edges with two equivalent OMg6 octahedra. The corner-sharing octahedral tilt angles are 0°. In the eighth O site, O is bonded to six Mg atoms to form OMg6 octahedra that share corners with four OMg6 octahedra, a cornercorner with one ORb2Mg3 trigonal bipyramid, edges with six OMg6 octahedra, and edges with four OMg5 square pyramids. The corner-sharing octahedra tilt angles range from 2–5°. In the ninth O site, O is bonded to six Mg atoms to form distorted OMg6 octahedra that share corners with four OMg6 octahedra, a cornercorner with one OHf2Mg3 trigonal bipyramid, edges with six OMg6 octahedra, and edges with four OMg5 square pyramids. The corner-sharing octahedra tilt angles range from 2–9°. In the tenth O site, O is bonded in a 5-coordinate geometry to one Rb, three Mg, and one Hf atom. In the eleventh O site, O is bonded to six Mg atoms to form OMg6 octahedra that share corners with four equivalent OMg6 octahedra, edges with six OMg6 octahedra, and edges with four OMg5 square pyramids. The corner-sharing octahedra tilt angles range from 2–15°.