RbMgF3 is (Cubic) Perovskite-like structured and crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded to six equivalent F(1) and six equivalent F(2) atoms to form RbF12 cuboctahedra that share corners with six equivalent Rb(1)F12 cuboctahedra, corners with six equivalent Rb(2)F12 cuboctahedra, faces with six equivalent Rb(2)F12 cuboctahedra, faces with two equivalent Mg(1)F6 octahedra, and faces with six equivalent Mg(2)F6 octahedra. In the second Rb site, Rb(2) is bonded to three equivalent F(1) and nine equivalent F(2) atoms to form RbF12 cuboctahedra that share corners with three equivalent Rb(1)F12 cuboctahedra, corners with six equivalent Rb(2)F12 cuboctahedra, corners with three equivalent Mg(2)F6 octahedra, faces with three equivalent Rb(1)F12 cuboctahedra, faces with four equivalent Rb(2)F12 cuboctahedra, faces with three equivalent Mg(1)F6 octahedra, and faces with four equivalent Mg(2)F6 octahedra. The corner-sharing octahedral tilt angles are 6°. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to six equivalent F(2) atoms to form MgF6 octahedra that share corners with six equivalent Mg(2)F6 octahedra, faces with two equivalent Rb(1)F12 cuboctahedra, and faces with six equivalent Rb(2)F12 cuboctahedra. The corner-sharing octahedral tilt angles are 2°. In the second Mg site, Mg(2) is bonded to three equivalent F(1) and three equivalent F(2) atoms to form MgF6 octahedra that share corners with three equivalent Rb(2)F12 cuboctahedra, corners with three equivalent Mg(1)F6 octahedra, faces with three equivalent Rb(1)F12 cuboctahedra, faces with four equivalent Rb(2)F12 cuboctahedra, and  a faceface with one Mg(2)F6 octahedra. The corner-sharing octahedral tilt angles are 2°. There are two inequivalent F sites. In the first F site, F(1) is bonded in a distorted L-shaped geometry to two equivalent Rb(1), two equivalent Rb(2), and two equivalent Mg(2) atoms. In the second F site, F(2) is bonded in a distorted linear geometry to one Rb(1), three equivalent Rb(2), one Mg(1), and one Mg(2) atom.
RbMgF3 is (Cubic) Perovskite-like structured and crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded to six equivalent F(1) and six equivalent F(2) atoms to form RbF12 cuboctahedra that share corners with six equivalent Rb(1)F12 cuboctahedra, corners with six equivalent Rb(2)F12 cuboctahedra, faces with six equivalent Rb(2)F12 cuboctahedra, faces with two equivalent Mg(1)F6 octahedra, and faces with six equivalent Mg(2)F6 octahedra. All Rb(1)-F(1) bond lengths are 2.92 Å. All Rb(1)-F(2) bond lengths are 2.94 Å. In the second Rb site, Rb(2) is bonded to three equivalent F(1) and nine equivalent F(2) atoms to form RbF12 cuboctahedra that share corners with three equivalent Rb(1)F12 cuboctahedra, corners with six equivalent Rb(2)F12 cuboctahedra, corners with three equivalent Mg(2)F6 octahedra, faces with three equivalent Rb(1)F12 cuboctahedra, faces with four equivalent Rb(2)F12 cuboctahedra, faces with three equivalent Mg(1)F6 octahedra, and faces with four equivalent Mg(2)F6 octahedra. The corner-sharing octahedral tilt angles are 6°. All Rb(2)-F(1) bond lengths are 2.86 Å. There are six shorter (2.92 Å) and three longer (3.03 Å) Rb(2)-F(2) bond lengths. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to six equivalent F(2) atoms to form MgF6 octahedra that share corners with six equivalent Mg(2)F6 octahedra, faces with two equivalent Rb(1)F12 cuboctahedra, and faces with six equivalent Rb(2)F12 cuboctahedra. The corner-sharing octahedral tilt angles are 2°. All Mg(1)-F(2) bond lengths are 2.02 Å. In the second Mg site, Mg(2) is bonded to three equivalent F(1) and three equivalent F(2) atoms to form MgF6 octahedra that share corners with three equivalent Rb(2)F12 cuboctahedra, corners with three equivalent Mg(1)F6 octahedra, faces with three equivalent Rb(1)F12 cuboctahedra, faces with four equivalent Rb(2)F12 cuboctahedra, and  a faceface with one Mg(2)F6 octahedra. The corner-sharing octahedral tilt angles are 2°. All Mg(2)-F(1) bond lengths are 2.02 Å. All Mg(2)-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 L-shaped geometry to two equivalent Rb(1), two equivalent Rb(2), and two equivalent Mg(2) atoms. In the second F site, F(2) is bonded in a distorted linear geometry to one Rb(1), three equivalent Rb(2), one Mg(1), and one Mg(2) atom.