DOI: 10.17188/1690663
title: Materials Data on Ca4HfN4 by Materials Project

description: Ca4HfN4 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are four inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to four N3- atoms to form distorted CaN4 trigonal pyramids that share corners with four CaN5 square pyramids, corners with four equivalent CaN4 tetrahedra, corners with four equivalent HfN4 tetrahedra, and edges with three CaN5 square pyramids. There are a spread of Ca–N bond distances ranging from 2.39–2.48 Å. In the second Ca2+ site, Ca2+ is bonded to four N3- atoms to form distorted CaN4 tetrahedra that share corners with four CaN5 square pyramids, corners with four equivalent HfN4 tetrahedra, corners with four equivalent CaN4 trigonal pyramids, and edges with two equivalent CaN4 tetrahedra. There are a spread of Ca–N bond distances ranging from 2.39–2.52 Å. In the third Ca2+ site, Ca2+ is bonded to five N3- atoms to form CaN5 square pyramids that share corners with three equivalent CaN5 square pyramids, corners with two equivalent CaN4 tetrahedra, corners with three equivalent HfN4 tetrahedra, a cornercorner with one CaN4 trigonal pyramid, edges with five CaN5 square pyramids, an edgeedge with one HfN4 tetrahedra, and edges with two equivalent CaN4 trigonal pyramids. There are a spread of Ca–N bond distances ranging from 2.46–2.59 Å. In the fourth Ca2+ site, Ca2+ is bonded to five N3- atoms to form CaN5 square pyramids that share corners with three equivalent CaN5 square pyramids, a cornercorner with one HfN4 tetrahedra, corners with two equivalent CaN4 tetrahedra, corners with three equivalent CaN4 trigonal pyramids, edges with five CaN5 square pyramids, edges with two equivalent HfN4 tetrahedra, and an edgeedge with one CaN4 trigonal pyramid. There are a spread of Ca–N bond distances ranging from 2.48–2.64 Å. Hf4+ is bonded to four N3- atoms to form HfN4 tetrahedra that share corners with four CaN5 square pyramids, corners with four equivalent CaN4 tetrahedra, corners with four equivalent CaN4 trigonal pyramids, and edges with three CaN5 square pyramids. There are a spread of Hf–N bond distances ranging from 2.06–2.10 Å. There are four inequivalent N3- sites. In the first N3- site, N3- is bonded to five Ca2+ and one Hf4+ atom to form NCa5Hf octahedra that share corners with four NCa5Hf octahedra, corners with two equivalent NCa3Hf tetrahedra, and edges with eight NCa5Hf octahedra. The corner-sharing octahedra tilt angles range from 8–19°. In the second N3- site, N3- is bonded to three Ca2+ and one Hf4+ atom to form distorted NCa3Hf tetrahedra that share corners with ten NCa5Hf octahedra and an edgeedge with one NCa3Hf tetrahedra. The corner-sharing octahedra tilt angles range from 54–69°. In the third N3- site, N3- is bonded to five Ca2+ and one Hf4+ atom to form NCa5Hf octahedra that share corners with two equivalent NCa5Hf octahedra, corners with six equivalent NCa3Hf tetrahedra, and edges with six NCa5Hf octahedra. The corner-sharing octahedra tilt angles range from 8–10°. In the fourth N3- site, N3- is bonded to five Ca2+ and one Hf4+ atom to form NCa5Hf octahedra that share corners with two equivalent NCa5Hf octahedra, corners with two equivalent NCa3Hf tetrahedra, and edges with nine NCa5Hf octahedra. The corner-sharing octahedra tilt angles range from 9–19°.