CsFeF4 crystallizes in the tetragonal P4/nmm space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 12-coordinate geometry to four equivalent F(2) and eight equivalent F(1) atoms. In the second Cs site, Cs(2) is bonded in a 12-coordinate geometry to four equivalent F(2) and eight equivalent F(1) atoms. Fe(1) is bonded to two equivalent F(1) and four equivalent F(2) atoms to form corner-sharing FeF6 octahedra. The corner-sharing octahedral tilt angles are 19°. There are two inequivalent F sites. In the first F site, F(1) is bonded in a distorted single-bond geometry to two equivalent Cs(1), two equivalent Cs(2), and one Fe(1) atom. In the second F site, F(2) is bonded in a distorted bent 150 degrees geometry to one Cs(1), one Cs(2), and two equivalent Fe(1) atoms.
CsFeF4 crystallizes in the tetragonal P4/nmm space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 12-coordinate geometry to four equivalent F(2) and eight equivalent F(1) atoms. All Cs(1)-F(2) bond lengths are 3.50 Å. All Cs(1)-F(1) bond lengths are 3.12 Å. In the second Cs site, Cs(2) is bonded in a 12-coordinate geometry to four equivalent F(2) and eight equivalent F(1) atoms. All Cs(2)-F(2) bond lengths are 3.24 Å. There are four shorter (3.00 Å) and four longer (3.27 Å) Cs(2)-F(1) bond lengths. Fe(1) is bonded to two equivalent F(1) and four equivalent F(2) atoms to form corner-sharing FeF6 octahedra. The corner-sharing octahedral tilt angles are 19°. Both Fe(1)-F(1) bond lengths are 1.87 Å. All Fe(1)-F(2) bond lengths are 1.98 Å. There are two inequivalent F sites. In the first F site, F(1) is bonded in a distorted single-bond geometry to two equivalent Cs(1), two equivalent Cs(2), and one Fe(1) atom. In the second F site, F(2) is bonded in a distorted bent 150 degrees geometry to one Cs(1), one Cs(2), and two equivalent Fe(1) atoms.