DOI: 10.17188/1723275
title: Materials Data on CsHfMg14O15 by Materials Project

description: CsMg14HfO15 crystallizes in the orthorhombic Pmm2 space group. The structure is three-dimensional. Cs is bonded in a 4-coordinate geometry to four O atoms. There are two shorter (2.80 Å) and two longer (2.93 Å) Cs–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 two equivalent MgO5 square pyramids, corners with two equivalent MgO5 trigonal bipyramids, and edges with eight MgO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.00–2.12 Å. In the second Mg site, Mg is bonded to five O atoms to form MgO5 trigonal bipyramids that share corners with two equivalent MgO5 square pyramids, corners with two equivalent MgO5 trigonal bipyramids, edges with six MgO6 octahedra, and edges with two equivalent MgO5 square pyramids. There are a spread of Mg–O bond distances ranging from 2.02–2.07 Å. In the third Mg site, Mg is bonded to five O atoms to form distorted MgO5 square pyramids that share a cornercorner with one MgO6 octahedra, corners with five MgO5 square pyramids, edges with three MgO6 octahedra, and edges with two equivalent HfO5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 3°. There are a spread of Mg–O bond distances ranging from 1.96–2.30 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, a cornercorner with one MgO4 trigonal pyramid, edges with three MgO6 octahedra, edges with three MgO5 square pyramids, and edges with two equivalent MgO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 1–16°. There are a spread of Mg–O bond distances ranging from 2.02–2.53 Å. In the fifth Mg site, Mg is bonded in a T-shaped geometry to three O atoms. There are one shorter (2.07 Å) and two longer (2.23 Å) Mg–O bond lengths. In the sixth Mg site, Mg is bonded to four O atoms to form distorted MgO4 trigonal pyramids that share corners with two equivalent MgO6 octahedra, corners with two equivalent HfO5 trigonal bipyramids, and corners with two equivalent MgO4 trigonal pyramids. The corner-sharing octahedral tilt angles are 62°. There are two shorter (2.11 Å) and two longer (2.21 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 two equivalent MgO6 octahedra, corners with two equivalent MgO5 square pyramids, edges with six MgO6 octahedra, and edges with four MgO5 square pyramids. The corner-sharing octahedral tilt angles are 18°. There are a spread of Mg–O bond distances ranging from 2.07–2.53 Å. In the eighth Mg site, Mg is bonded to five O atoms to form MgO5 square pyramids that share corners with two equivalent MgO6 octahedra, corners with four MgO5 square pyramids, edges with six MgO6 octahedra, and edges with two equivalent MgO5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 6°. There are a spread of Mg–O bond distances ranging from 2.04–2.07 Å. In the ninth Mg site, Mg is bonded in a distorted T-shaped geometry to four O atoms. There are a spread of Mg–O bond distances ranging from 2.08–2.70 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 four MgO6 octahedra, edges with five MgO5 square pyramids, and an edgeedge with one MgO5 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 2–19°. There are a spread of Mg–O bond distances ranging from 2.07–2.59 Å. Hf is bonded to five O atoms to form HfO5 trigonal bipyramids that share corners with two equivalent MgO6 octahedra, corners with two equivalent HfO5 trigonal bipyramids, corners with two equivalent MgO4 trigonal pyramids, and edges with four equivalent MgO5 square pyramids. The corner-sharing octahedral tilt angles are 54°. There are a spread of Hf–O bond distances ranging from 2.01–2.10 Å. There are eleven inequivalent O sites. In the first O site, O is bonded in a 3-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 OCs2Mg3 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, edges with six OMg6 octahedra, and edges with two equivalent OMg5 square pyramids. In the fourth O site, O is bonded to five Mg atoms to form OMg5 trigonal bipyramids that share a cornercorner with one OMg6 octahedra, a cornercorner with one OMg5 square pyramid, corners with four equivalent OMg5 trigonal bipyramids, and edges with three OMg6 octahedra. The corner-sharing octahedral tilt angles are 1°. 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 trigonal bipyramid, edges with three OMg6 octahedra, edges with five OMg5 square pyramids, and an edgeedge with one OCs2Mg3 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 1–12°. In the sixth O site, O is bonded to two equivalent Cs and three Mg atoms to form distorted OCs2Mg3 trigonal bipyramids that share a cornercorner with one OMg6 octahedra, corners with two equivalent OMg5 square pyramids, corners with two equivalent OCs2Mg3 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 in a distorted see-saw-like geometry to two equivalent Mg and two equivalent Hf atoms. In the eighth O site, O is bonded to six Mg atoms to form OMg6 octahedra that share corners with two equivalent OMg6 octahedra, corners with two equivalent OMg5 square pyramids, a cornercorner with one OCs2Mg3 trigonal bipyramid, edges with six OMg6 octahedra, edges with two equivalent OMg5 square pyramids, and edges with two equivalent OMg5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 11°. In the ninth O site, O is bonded to five Mg atoms to form OMg5 square pyramids that share corners with two equivalent OMg6 octahedra, corners with two equivalent OMg5 square pyramids, corners with two equivalent OMg5 trigonal bipyramids, edges with six OMg6 octahedra, and edges with two equivalent OMg5 square pyramids. The corner-sharing octahedral tilt angles are 8°. In the tenth O site, O is bonded in a 5-coordinate geometry to one Cs, 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 four OMg6 octahedra, edges with four OMg5 square pyramids, and edges with two equivalent OMg5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 2–19°.