CsMgBr3 crystallizes in the hexagonal P6_3/mmc space group. Cs(1) is bonded to twelve equivalent Br(1) atoms to form CsBr12 cuboctahedra that share corners with six equivalent Cs(1)Br12 cuboctahedra, corners with six equivalent Mg(1)Br6 octahedra, faces with eight equivalent Cs(1)Br12 cuboctahedra, and faces with six equivalent Mg(1)Br6 octahedra. The corner-sharing octahedral tilt angles are 17°. Mg(1) is bonded to six equivalent Br(1) atoms to form MgBr6 octahedra that share corners with six equivalent Cs(1)Br12 cuboctahedra, faces with six equivalent Cs(1)Br12 cuboctahedra, and faces with two equivalent Mg(1)Br6 octahedra. Br(1) is bonded in a 2-coordinate geometry to four equivalent Cs(1) and two equivalent Mg(1) atoms.
CsMgBr3 crystallizes in the hexagonal P6_3/mmc space group. Cs(1) is bonded to twelve equivalent Br(1) atoms to form CsBr12 cuboctahedra that share corners with six equivalent Cs(1)Br12 cuboctahedra, corners with six equivalent Mg(1)Br6 octahedra, faces with eight equivalent Cs(1)Br12 cuboctahedra, and faces with six equivalent Mg(1)Br6 octahedra. The corner-sharing octahedral tilt angles are 17°. There are six shorter (3.83 Å) and six longer (3.98 Å) Cs(1)-Br(1) bond lengths. Mg(1) is bonded to six equivalent Br(1) atoms to form MgBr6 octahedra that share corners with six equivalent Cs(1)Br12 cuboctahedra, faces with six equivalent Cs(1)Br12 cuboctahedra, and faces with two equivalent Mg(1)Br6 octahedra. All Mg(1)-Br(1) bond lengths are 2.67 Å. Br(1) is bonded in a 2-coordinate geometry to four equivalent Cs(1) and two equivalent Mg(1) atoms.