DOI: 10.17188/1663093
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 5-coordinate geometry to five O atoms. There are two shorter (2.60 Å) and three longer (2.75 Å) Rb–O bond lengths. There are ten 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 MgO5 square pyramids, edges with eight MgO6 octahedra, and edges with two equivalent MgO5 square pyramids. The corner-sharing octahedral tilt angles are 3°. There are a spread of Mg–O bond distances ranging from 2.00–2.18 Å. In the second Mg site, Mg is bonded to five O atoms to form MgO5 square pyramids that share corners with two equivalent MgO6 octahedra, corners with two equivalent MgO5 square pyramids, and edges with eight MgO6 octahedra. The corner-sharing octahedral tilt angles are 8°. There are a spread of Mg–O bond distances ranging from 2.01–2.09 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, and edges with four MgO6 octahedra. The corner-sharing octahedral tilt angles are 4°. There are a spread of Mg–O bond distances ranging from 1.98–2.24 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 six MgO6 octahedra, and edges with three MgO5 square pyramids. The corner-sharing octahedra tilt angles range from 1–9°. There are a spread of Mg–O bond distances ranging from 2.07–2.25 Å. In the fifth Mg site, Mg is bonded to five O atoms to form MgO5 square pyramids that share a cornercorner with one MgO6 octahedra, corners with two equivalent MgO5 square pyramids, and edges with four MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Mg–O bond distances ranging from 2.03–2.09 Å. In the sixth Mg site, Mg is bonded in a distorted T-shaped geometry to three O atoms. There are two shorter (2.17 Å) and one longer (2.41 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 four MgO6 octahedra, a cornercorner with one MgO5 square pyramid, edges with eight MgO6 octahedra, and edges with two equivalent MgO5 square pyramids. The corner-sharing octahedra tilt angles range from 4–12°. There are a spread of Mg–O bond distances ranging from 2.06–2.27 Å. In the eighth 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 4–12°. There are a spread of Mg–O bond distances ranging from 2.08–2.53 Å. In the ninth Mg site, Mg is bonded in a rectangular see-saw-like geometry to four O atoms. There are a spread of Mg–O bond distances ranging from 2.04–2.10 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, edges with seven MgO6 octahedra, and edges with three MgO5 square pyramids. The corner-sharing octahedra tilt angles range from 3–11°. There are a spread of Mg–O bond distances ranging from 2.07–2.32 Å. Hf is bonded in a 4-coordinate geometry to four O atoms. There are two shorter (2.00 Å) and two longer (2.21 Å) Hf–O bond lengths. There are eleven inequivalent O sites. In the first O site, O is bonded to one Rb and five Mg atoms to form ORbMg5 octahedra that share corners with two equivalent ORbMg5 octahedra, a cornercorner with one OMg5 square pyramid, corners with four ORbHfMg3 trigonal bipyramids, edges with four OMg6 octahedra, and edges with four equivalent OMg5 square pyramids. The corner-sharing octahedral tilt angles are 6°. In the second O site, O is bonded to five Mg atoms to form OMg5 square pyramids that share a cornercorner with one ORbMg5 octahedra, corners with four OMg5 square pyramids, corners with four ORb2Mg3 trigonal bipyramids, and edges with eight OMg6 octahedra. The corner-sharing octahedral tilt angles are 0°. 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 four 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 six ORbMg5 octahedra. The corner-sharing octahedral tilt angles are 2°. 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 four ORb2Mg3 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 2–6°. In the sixth O site, O is bonded to two equivalent Rb and three Mg atoms to form ORb2Mg3 trigonal bipyramids that share corners with three ORbMg5 octahedra, corners with two equivalent OMg5 square pyramids, corners with four ORb2Mg3 trigonal bipyramids, edges with two equivalent OMg6 octahedra, and edges with four equivalent ORbHfMg3 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 0–53°. In the seventh O site, O is bonded to three Mg and two equivalent Hf atoms to form OHf2Mg3 trigonal bipyramids that share a cornercorner with one OMg6 octahedra, corners with two equivalent OMg5 square pyramids, corners with four OHf2Mg3 trigonal bipyramids, edges with two equivalent OMg6 octahedra, and edges with four equivalent ORbHfMg3 trigonal bipyramids. 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 eight ORbMg5 octahedra, and edges with four OMg5 square pyramids. The corner-sharing octahedra tilt angles range from 3–4°. In the ninth O site, O is bonded to six Mg atoms to form 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 4–16°. In the tenth O site, O is bonded to one Rb, three Mg, and one Hf atom to form distorted ORbHfMg3 trigonal bipyramids that share corners with two ORbMg5 octahedra, corners with two OMg5 square pyramids, corners with four equivalent ORbHfMg3 trigonal bipyramids, edges with two equivalent OMg6 octahedra, and edges with four OHf2Mg3 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 9–60°. In the eleventh 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 ORbHfMg3 trigonal bipyramid, edges with seven ORbMg5 octahedra, and edges with four OMg5 square pyramids. The corner-sharing octahedra tilt angles range from 3–10°.