DOI: 10.17188/1688234
title: Materials Data on Ca5Ni9As7 by Materials Project

description: Ca5Ni9As7 crystallizes in the hexagonal P-6 space group. The structure is three-dimensional. there are three inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to five As3- atoms to form distorted CaAs5 trigonal bipyramids that share corners with four CaAs6 pentagonal pyramids, corners with eight NiAs4 tetrahedra, corners with four equivalent CaAs5 trigonal bipyramids, an edgeedge with one CaAs6 pentagonal pyramid, edges with seven NiAs4 tetrahedra, and edges with four equivalent CaAs5 trigonal bipyramids. There are a spread of Ca–As bond distances ranging from 2.81–2.86 Å. In the second Ca2+ site, Ca2+ is bonded to six equivalent As3- atoms to form distorted CaAs6 pentagonal pyramids that share corners with twelve NiAs4 tetrahedra, corners with six equivalent CaAs5 trigonal bipyramids, edges with twelve NiAs4 tetrahedra, and faces with two equivalent CaAs6 pentagonal pyramids. All Ca–As bond lengths are 2.97 Å. In the third Ca2+ site, Ca2+ is bonded to six equivalent As3- atoms to form distorted CaAs6 pentagonal pyramids that share corners with twelve NiAs4 tetrahedra, corners with six equivalent CaAs5 trigonal bipyramids, edges with nine NiAs4 tetrahedra, edges with three equivalent CaAs5 trigonal bipyramids, and faces with two equivalent CaAs6 pentagonal pyramids. All Ca–As bond lengths are 3.11 Å. There are three inequivalent Ni+1.22+ sites. In the first Ni+1.22+ site, Ni+1.22+ is bonded to four As3- atoms to form NiAs4 tetrahedra that share corners with two equivalent CaAs6 pentagonal pyramids, corners with twelve NiAs4 tetrahedra, corners with two equivalent CaAs5 trigonal bipyramids, edges with three CaAs6 pentagonal pyramids, edges with three NiAs4 tetrahedra, and edges with two equivalent CaAs5 trigonal bipyramids. There are a spread of Ni–As bond distances ranging from 2.29–2.80 Å. In the second Ni+1.22+ site, Ni+1.22+ is bonded to four As3- atoms to form NiAs4 tetrahedra that share corners with four CaAs6 pentagonal pyramids, corners with ten NiAs4 tetrahedra, corners with two equivalent CaAs5 trigonal bipyramids, an edgeedge with one CaAs6 pentagonal pyramid, edges with three NiAs4 tetrahedra, and edges with four equivalent CaAs5 trigonal bipyramids. There are three shorter (2.42 Å) and one longer (2.63 Å) Ni–As bond lengths. In the third Ni+1.22+ site, Ni+1.22+ is bonded to four As3- atoms to form NiAs4 tetrahedra that share corners with two equivalent CaAs6 pentagonal pyramids, corners with ten NiAs4 tetrahedra, corners with four equivalent CaAs5 trigonal bipyramids, edges with three CaAs6 pentagonal pyramids, edges with four NiAs4 tetrahedra, and an edgeedge with one CaAs5 trigonal bipyramid. There are a spread of Ni–As bond distances ranging from 2.32–2.44 Å. There are three inequivalent As3- sites. In the first As3- site, As3- is bonded in a 9-coordinate geometry to three Ca2+ and six Ni+1.22+ atoms. In the second As3- site, As3- is bonded in a 9-coordinate geometry to six equivalent Ca2+ and three equivalent Ni+1.22+ atoms. In the third As3- site, As3- is bonded in a 9-coordinate geometry to four Ca2+ and five Ni+1.22+ atoms.