CsRb2SiF7 crystallizes in the tetragonal P4/mbm space group. Cs(1) is bonded to two equivalent F(2) and four equivalent F(3) atoms to form distorted CsF6 octahedra that share corners with four equivalent Si(1)F6 octahedra and corners with six equivalent Cs(1)F6 octahedra. The corner-sharing octahedral tilt angles range from 0-68°. Rb(1) is bonded in a 10-coordinate geometry to two equivalent F(2), two equivalent F(3), and six equivalent F(1) atoms. Si(1) is bonded to two equivalent F(3) and four equivalent F(1) atoms to form SiF6 octahedra that share corners with four equivalent Cs(1)F6 octahedra. The corner-sharing octahedral tilt angles are 68°. There are three inequivalent F sites. In the first F site, F(1) is bonded in a distorted single-bond geometry to three equivalent Rb(1) and one Si(1) atom. In the second F site, F(2) is bonded to two equivalent Cs(1) and four equivalent Rb(1) atoms to form corner-sharing FCs2Rb4 octahedra. The corner-sharing octahedral tilt angles range from 0-25°. In the third F site, F(3) is bonded in a single-bond geometry to two equivalent Cs(1), two equivalent Rb(1), and one Si(1) atom.
CsRb2SiF7 crystallizes in the tetragonal P4/mbm space group. Cs(1) is bonded to two equivalent F(2) and four equivalent F(3) atoms to form distorted CsF6 octahedra that share corners with four equivalent Si(1)F6 octahedra and corners with six equivalent Cs(1)F6 octahedra. The corner-sharing octahedral tilt angles range from 0-68°. Both Cs(1)-F(2) bond lengths are 2.98 Å. All Cs(1)-F(3) bond lengths are 3.15 Å. Rb(1) is bonded in a 10-coordinate geometry to two equivalent F(2), two equivalent F(3), and six equivalent F(1) atoms. Both Rb(1)-F(2) bond lengths are 2.98 Å. Both Rb(1)-F(3) bond lengths are 3.03 Å. There are two shorter (2.92 Å) and four longer (3.12 Å) Rb(1)-F(1) bond lengths. Si(1) is bonded to two equivalent F(3) and four equivalent F(1) atoms to form SiF6 octahedra that share corners with four equivalent Cs(1)F6 octahedra. The corner-sharing octahedral tilt angles are 68°. Both Si(1)-F(3) bond lengths are 1.72 Å. All Si(1)-F(1) bond lengths are 1.73 Å. There are three inequivalent F sites. In the first F site, F(1) is bonded in a distorted single-bond geometry to three equivalent Rb(1) and one Si(1) atom. In the second F site, F(2) is bonded to two equivalent Cs(1) and four equivalent Rb(1) atoms to form corner-sharing FCs2Rb4 octahedra. The corner-sharing octahedral tilt angles range from 0-25°. In the third F site, F(3) is bonded in a single-bond geometry to two equivalent Cs(1), two equivalent Rb(1), and one Si(1) atom.