Cs3SiF7 crystallizes in the tetragonal P4/mbm space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 10-coordinate geometry to two equivalent F(2), two equivalent F(3), and six equivalent F(1) atoms. In the second Cs site, Cs(2) 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(2)F6 octahedra. The corner-sharing octahedral tilt angles range from 0-67°. 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(2)F6 octahedra. The corner-sharing octahedral tilt angles are 67°. There are three inequivalent F sites. In the first F site, F(1) is bonded in a distorted single-bond geometry to three equivalent Cs(1) and one Si(1) atom. In the second F site, F(2) is bonded to two equivalent Cs(2) and four equivalent Cs(1) atoms to form corner-sharing FCs6 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 Cs(2), and one Si(1) atom.
Cs3SiF7 crystallizes in the tetragonal P4/mbm space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 10-coordinate geometry to two equivalent F(2), two equivalent F(3), and six equivalent F(1) atoms. Both Cs(1)-F(2) bond lengths are 2.99 Å. Both Cs(1)-F(3) bond lengths are 3.13 Å. There are two shorter (3.01 Å) and four longer (3.18 Å) Cs(1)-F(1) bond lengths. In the second Cs site, Cs(2) 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(2)F6 octahedra. The corner-sharing octahedral tilt angles range from 0-67°. Both Cs(2)-F(2) bond lengths are 3.07 Å. All Cs(2)-F(3) bond lengths are 3.16 Å. 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(2)F6 octahedra. The corner-sharing octahedral tilt angles are 67°. Both Si(1)-F(3) bond lengths are 1.70 Å. All Si(1)-F(1) bond lengths are 1.70 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 Cs(1) and one Si(1) atom. In the second F site, F(2) is bonded to two equivalent Cs(2) and four equivalent Cs(1) atoms to form corner-sharing FCs6 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 Cs(2), and one Si(1) atom.