DOE OSTI2020
Rb2KGaF6 crystallizes in the tetragonal I4/m space group. The structure is three-dimensional. there are two inequivalent Rb1+ sites. In the first Rb1+ site, Rb1+ is bonded to twelve F1- atoms to form RbF12 cuboctahedra that share faces with two equivalent RbF12 cuboctahedra, faces with four equivalent GaF6 octahedra, and faces with four equivalent KF7 pentagonal bipyramids. There are eight shorter (3.12 Å) and four longer (3.16 Å) Rb–F bond lengths. In the second Rb1+ site, Rb1+ is bonded in a 11-coordinate geometry to eleven F1- atoms. There are a spread of Rb–F bond distances ranging from 2.82–3.37 Å. There are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to six F1- atoms to form KF6 octahedra that share corners with six GaF6 octahedra. The corner-sharing octahedra tilt angles range from 0–2°. There are four shorter (2.53 Å) and two longer (2.58 Å) K–F bond lengths. In the second K1+ site, K1+ is bonded to seven F1- atoms to form distorted KF7 pentagonal bipyramids that share corners with five equivalent GaF6 octahedra, corners with two equivalent KF7 pentagonal bipyramids, an edgeedge with one GaF6 octahedra, and faces with two equivalent RbF12 cuboctahedra. The corner-sharing octahedra tilt angles range from 1–13°. There are a spread of K–F bond distances ranging from 2.56–2.95 Å. There are two inequivalent Ga3+ sites. In the first Ga3+ site, Ga3+ is bonded to six F1- atoms to form GaF6 octahedra that share corners with two equivalent KF6 octahedra and edges with four equivalent KF7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 0°. There is two shorter (1.92 Å) and four longer (1.94 Å) Ga–F bond length. In the second Ga3+ site, Ga3+ is bonded to six F1- atoms to form GaF6 octahedra that share a cornercorner with one KF6 octahedra, corners with five equivalent KF7 pentagonal bipyramids, and faces with two equivalent RbF12 cuboctahedra. The corner-sharing octahedral tilt angles are 2°. There are a spread of Ga–F bond distances ranging from 1.90–1.95 Å. There are seven inequivalent F1- sites. In the first F1- site, F1- is bonded in a 1-coordinate geometry to two equivalent Rb1+, two equivalent K1+, and one Ga3+ atom. In the second F1- site, F1- is bonded in a distorted linear geometry to four equivalent Rb1+, one K1+, and one Ga3+ atom. In the third F1- site, F1- is bonded in a 2-coordinate geometry to four equivalent Rb1+, one K1+, and one Ga3+ atom. In the fourth F1- site, F1- is bonded in a distorted single-bond geometry to four Rb1+, one K1+, and one Ga3+ atom. In the fifth F1- site, F1- is bonded in a 2-coordinate geometry to four Rb1+, one K1+, and one Ga3+ atom. In the sixth F1- site, F1- is bonded in a 2-coordinate geometry to four Rb1+, one K1+, and one Ga3+ atom. In the seventh F1- site, F1- is bonded in a 1-coordinate geometry to four equivalent Rb1+, one K1+, and one Ga3+ atom.