DOE OSTI2020
RbNi2F6 crystallizes in the orthorhombic Imma space group. The structure is three-dimensional. Rb1+ is bonded to six F1- atoms to form RbF6 octahedra that share corners with twelve NiF6 octahedra. The corner-sharing octahedra tilt angles range from 65–69°. There are a spread of Rb–F bond distances ranging from 2.93–3.14 Å. There are two inequivalent Ni+2.50+ sites. In the first Ni+2.50+ site, Ni+2.50+ is bonded to six F1- atoms to form NiF6 octahedra that share corners with six equivalent RbF6 octahedra and corners with six NiF6 octahedra. The corner-sharing octahedra tilt angles range from 44–69°. There is two shorter (1.96 Å) and four longer (2.01 Å) Ni–F bond length. In the second Ni+2.50+ site, Ni+2.50+ is bonded to six F1- atoms to form NiF6 octahedra that share corners with six equivalent RbF6 octahedra and corners with six NiF6 octahedra. The corner-sharing octahedra tilt angles range from 42–69°. There is four shorter (1.85 Å) and two longer (1.99 Å) Ni–F bond length. There are three inequivalent F1- sites. In the first F1- site, F1- is bonded in a 2-coordinate geometry to one Rb1+ and two Ni+2.50+ atoms. In the second F1- site, F1- is bonded in a 3-coordinate geometry to one Rb1+ and two equivalent Ni+2.50+ atoms. In the third F1- site, F1- is bonded in a 3-coordinate geometry to one Rb1+ and two equivalent Ni+2.50+ atoms.