DOI: 10.17188/1291740
title: Materials Data on Hf5N5O2 by Materials Project

description: Hf5N5O2 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are five inequivalent Hf sites. In the first Hf site, Hf is bonded to six N atoms to form HfN6 octahedra that share corners with three HfN5O octahedra and edges with five HfN6 octahedra. The corner-sharing octahedra tilt angles range from 7–57°. There are a spread of Hf–N bond distances ranging from 2.10–2.30 Å. In the second Hf site, Hf is bonded in a 7-coordinate geometry to five N and three O atoms. There are four shorter (2.28 Å) and one longer (2.81 Å) Hf–N bond lengths. There are two shorter (2.20 Å) and one longer (2.48 Å) Hf–O bond lengths. In the third Hf site, Hf is bonded in a 7-coordinate geometry to five N and two equivalent O atoms. There are a spread of Hf–N bond distances ranging from 2.15–2.45 Å. Both Hf–O bond lengths are 2.36 Å. In the fourth Hf site, Hf is bonded to five N and one O atom to form a mixture of corner and edge-sharing HfN5O octahedra. The corner-sharing octahedra tilt angles range from 7–61°. There are a spread of Hf–N bond distances ranging from 2.17–2.21 Å. The Hf–O bond length is 2.18 Å. In the fifth Hf site, Hf is bonded to three N and three O atoms to form HfN3O3 octahedra that share corners with two HfN6 octahedra and edges with two equivalent HfN3O3 octahedra. The corner-sharing octahedra tilt angles range from 57–61°. There are one shorter (2.05 Å) and two longer (2.15 Å) Hf–N bond lengths. There are one shorter (2.17 Å) and two longer (2.25 Å) Hf–O bond lengths. There are five inequivalent N sites. In the first N site, N is bonded in a distorted rectangular see-saw-like geometry to five Hf atoms. In the second N site, N is bonded to five Hf atoms to form NHf5 trigonal bipyramids that share a cornercorner with one OHf4 tetrahedra, corners with four equivalent NHf4 tetrahedra, corners with two equivalent NHf5 trigonal bipyramids, corners with two equivalent OHf5 trigonal bipyramids, an edgeedge with one NHf4 tetrahedra, an edgeedge with one OHf5 trigonal bipyramid, and edges with four NHf5 trigonal bipyramids. In the third N site, N is bonded to five Hf atoms to form NHf5 trigonal bipyramids that share a cornercorner with one NHf4 tetrahedra, corners with four equivalent OHf4 tetrahedra, corners with two equivalent NHf5 trigonal bipyramids, corners with two equivalent OHf5 trigonal bipyramids, an edgeedge with one OHf4 tetrahedra, and edges with five NHf5 trigonal bipyramids. In the fourth N site, N is bonded to five Hf atoms to form distorted NHf5 trigonal bipyramids that share corners with four equivalent OHf4 tetrahedra, corners with two equivalent OHf5 trigonal bipyramids, corners with four NHf5 trigonal bipyramids, an edgeedge with one OHf4 tetrahedra, edges with two equivalent NHf4 tetrahedra, edges with three NHf5 trigonal bipyramids, and edges with three equivalent OHf5 trigonal bipyramids. In the fifth N site, N is bonded to four Hf atoms to form NHf4 tetrahedra that share a cornercorner with one OHf4 tetrahedra, corners with two equivalent NHf4 tetrahedra, corners with four equivalent OHf5 trigonal bipyramids, corners with five NHf5 trigonal bipyramids, an edgeedge with one OHf5 trigonal bipyramid, and edges with three NHf5 trigonal bipyramids. There are two inequivalent O sites. In the first O site, O is bonded to four Hf atoms to form OHf4 tetrahedra that share a cornercorner with one NHf4 tetrahedra, corners with two equivalent OHf4 tetrahedra, corners with nine NHf5 trigonal bipyramids, edges with two NHf5 trigonal bipyramids, and edges with two equivalent OHf5 trigonal bipyramids. In the second O site, O is bonded to five Hf atoms to form distorted OHf5 trigonal bipyramids that share corners with four equivalent NHf4 tetrahedra, corners with six NHf5 trigonal bipyramids, an edgeedge with one NHf4 tetrahedra, edges with two equivalent OHf4 tetrahedra, edges with two equivalent OHf5 trigonal bipyramids, and edges with four NHf5 trigonal bipyramids.