DOE OSTI2020
Ni9S8 crystallizes in the orthorhombic C222 space group. The structure is three-dimensional. there are eight inequivalent Ni+1.78+ sites. In the first Ni+1.78+ site, Ni+1.78+ is bonded to five S2- atoms to form NiS5 square pyramids that share corners with nine NiS4 tetrahedra, a cornercorner with one NiS5 trigonal bipyramid, edges with three equivalent NiS5 square pyramids, an edgeedge with one NiS4 tetrahedra, and an edgeedge with one NiS5 trigonal bipyramid. There are a spread of Ni–S bond distances ranging from 2.25–2.30 Å. In the second Ni+1.78+ site, Ni+1.78+ is bonded to four equivalent S2- atoms to form NiS4 tetrahedra that share corners with four equivalent NiS5 square pyramids, corners with eight equivalent NiS5 trigonal bipyramids, and edges with two equivalent NiS4 tetrahedra. All Ni–S bond lengths are 2.18 Å. In the third Ni+1.78+ site, Ni+1.78+ is bonded to four S2- atoms to form NiS4 tetrahedra that share corners with two equivalent NiS5 square pyramids, corners with six NiS4 tetrahedra, corners with two equivalent NiS5 trigonal bipyramids, an edgeedge with one NiS4 tetrahedra, and edges with two equivalent NiS5 trigonal bipyramids. There are two shorter (2.21 Å) and two longer (2.25 Å) Ni–S bond lengths. In the fourth Ni+1.78+ site, Ni+1.78+ is bonded to four S2- atoms to form NiS4 tetrahedra that share corners with two equivalent NiS5 square pyramids, corners with four NiS4 tetrahedra, corners with four equivalent NiS5 trigonal bipyramids, an edgeedge with one NiS4 tetrahedra, and edges with two equivalent NiS5 trigonal bipyramids. There are two shorter (2.24 Å) and two longer (2.26 Å) Ni–S bond lengths. In the fifth Ni+1.78+ site, Ni+1.78+ is bonded to four equivalent S2- atoms to form NiS4 tetrahedra that share corners with four equivalent NiS5 square pyramids, corners with four equivalent NiS5 trigonal bipyramids, and edges with four NiS4 tetrahedra. All Ni–S bond lengths are 2.21 Å. In the sixth Ni+1.78+ site, Ni+1.78+ is bonded to five S2- atoms to form distorted NiS5 trigonal bipyramids that share a cornercorner with one NiS5 square pyramid, corners with nine NiS4 tetrahedra, an edgeedge with one NiS5 square pyramid, edges with two NiS4 tetrahedra, and edges with two equivalent NiS5 trigonal bipyramids. There are a spread of Ni–S bond distances ranging from 2.22–2.36 Å. In the seventh Ni+1.78+ site, Ni+1.78+ is bonded to four S2- atoms to form NiS4 tetrahedra that share corners with six equivalent NiS5 square pyramids, corners with six NiS4 tetrahedra, and corners with four equivalent NiS5 trigonal bipyramids. All Ni–S bond lengths are 2.16 Å. In the eighth Ni+1.78+ site, Ni+1.78+ is bonded to four S2- atoms to form NiS4 tetrahedra that share corners with four equivalent NiS5 square pyramids, corners with four NiS4 tetrahedra, corners with two equivalent NiS5 trigonal bipyramids, edges with two equivalent NiS5 square pyramids, and an edgeedge with one NiS4 tetrahedra. There are two shorter (2.22 Å) and two longer (2.24 Å) Ni–S bond lengths. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a 5-coordinate geometry to five Ni+1.78+ atoms. In the second S2- site, S2- is bonded in a 5-coordinate geometry to five Ni+1.78+ atoms. In the third S2- site, S2- is bonded in a 5-coordinate geometry to five Ni+1.78+ atoms. In the fourth S2- site, S2- is bonded in a 5-coordinate geometry to five Ni+1.78+ atoms.