DOE OSTI2020
Ni2SiO4 is Ilmenite-like structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Ni2+ sites. In the first Ni2+ site, Ni2+ is bonded to six O2- atoms to form NiO6 octahedra that share corners with eight NiO6 octahedra, corners with four equivalent SiO4 tetrahedra, edges with two equivalent NiO6 octahedra, and an edgeedge with one SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 51–61°. There are a spread of Ni–O bond distances ranging from 2.06–2.19 Å. In the second Ni2+ site, Ni2+ is bonded to six O2- atoms to form NiO6 octahedra that share corners with four equivalent NiO6 octahedra, corners with two equivalent SiO4 tetrahedra, edges with four NiO6 octahedra, and edges with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 56–61°. There are four shorter (2.09 Å) and two longer (2.13 Å) Ni–O bond lengths. Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with six NiO6 octahedra and edges with three NiO6 octahedra. The corner-sharing octahedra tilt angles range from 55–60°. There are a spread of Si–O bond distances ranging from 1.63–1.67 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to three Ni2+ and one Si4+ atom. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three Ni2+ and one Si4+ atom. In the third O2- site, O2- is bonded in a 4-coordinate geometry to three Ni2+ and one Si4+ atom.