DOI: 10.17188/1672122
title: Materials Data on HfMg6NiO8 by Materials Project

description: Mg6HfNiO8 is Caswellsilverite-derived structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. there are three 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 NiO6 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 (2.06 Å) and four longer (2.13 Å) Mg–O bond lengths. 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 equivalent MgO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.13 Å) and two longer (2.29 Å) Mg–O bond lengths. In the third Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with six equivalent MgO6 octahedra, edges with two equivalent HfO6 octahedra, edges with two equivalent NiO6 octahedra, and edges with eight MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–7°. There are a spread of Mg–O bond distances ranging from 2.13–2.39 Å. Hf is bonded to six O atoms to form HfO6 octahedra that share corners with two equivalent MgO6 octahedra, corners with four equivalent HfO6 octahedra, edges with four equivalent NiO6 octahedra, and edges with eight equivalent MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.13 Å) and two longer (2.26 Å) Hf–O bond lengths. Ni is bonded to six O atoms to form NiO6 octahedra that share corners with two equivalent MgO6 octahedra, corners with four equivalent NiO6 octahedra, edges with four equivalent HfO6 octahedra, and edges with eight equivalent MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.13 Å) and two longer (2.50 Å) Ni–O bond lengths. There are six inequivalent O sites. In the first O site, O is bonded to five Mg and one Ni atom to form distorted OMg5Ni octahedra that share corners with six equivalent OMg5Ni octahedra and edges with twelve OHfMg5 octahedra. The corner-sharing octahedra tilt angles range from 0–6°. In the second O site, O is bonded to five Mg and one Hf atom to form OHfMg5 octahedra that share corners with six equivalent OHfMg5 octahedra and edges with twelve OMg5Ni octahedra. The corner-sharing octahedra tilt angles range from 0–7°. In the third O site, O is bonded to two equivalent Mg, two equivalent Hf, and two equivalent Ni atoms to form OHf2Mg2Ni2 octahedra that share corners with six OHf2Mg2Ni2 octahedra and edges with twelve OMg5Ni octahedra. The corner-sharing octahedral tilt angles are 0°. In the fourth O site, O is bonded to six Mg atoms to form OMg6 octahedra that share corners with six OHf2Mg2Ni2 octahedra and edges with twelve OMg5Ni octahedra. The corner-sharing octahedral tilt angles are 0°. In the fifth O site, O is bonded to two equivalent Mg, two equivalent Hf, and two equivalent Ni atoms to form OHf2Mg2Ni2 octahedra that share corners with six OHf2Mg2Ni2 octahedra and edges with twelve OMg5Ni octahedra. The corner-sharing octahedral tilt angles are 0°. Both O–Mg bond lengths are 2.39 Å. In the sixth O site, O is bonded to six Mg atoms to form OMg6 octahedra that share corners with six OHf2Mg2Ni2 octahedra and edges with twelve OMg5Ni octahedra. The corner-sharing octahedral tilt angles are 0°. Both O–Mg bond lengths are 2.17 Å.