RbMgCl3 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 Cl(1) and six equivalent Cl(2) atoms to form RbCl12 cuboctahedra that share corners with six equivalent Rb(1)Cl12 cuboctahedra, corners with six equivalent Mg(1)Cl6 octahedra, faces with two equivalent Rb(1)Cl12 cuboctahedra, faces with six equivalent Rb(2)Cl12 cuboctahedra, and faces with six equivalent Mg(1)Cl6 octahedra. The corner-sharing octahedral tilt angles are 16°. In the second Rb site, Rb(2) is bonded to six equivalent Cl(1) and six equivalent Cl(2) atoms to form RbCl12 cuboctahedra that share corners with twelve equivalent Rb(2)Cl12 cuboctahedra, faces with six equivalent Rb(1)Cl12 cuboctahedra, and faces with eight equivalent Mg(1)Cl6 octahedra. Mg(1) is bonded to three equivalent Cl(1) and three equivalent Cl(2) atoms to form MgCl6 octahedra that share corners with three equivalent Rb(1)Cl12 cuboctahedra, corners with three equivalent Mg(1)Cl6 octahedra, faces with three equivalent Rb(1)Cl12 cuboctahedra, faces with four equivalent Rb(2)Cl12 cuboctahedra, and  a faceface with one Mg(1)Cl6 octahedra. The corner-sharing octahedra are not tilted. There are two inequivalent Cl sites. In the first Cl site, Cl(1) is bonded in a distorted linear geometry to two equivalent Rb(1), two equivalent Rb(2), and two equivalent Mg(1) atoms. In the second Cl site, Cl(2) is bonded to two equivalent Rb(1), two equivalent Rb(2), and two equivalent Mg(1) atoms to form a mixture of distorted corner and face-sharing ClRb4Mg2 octahedra. The corner-sharing octahedral tilt angles range from 0-61°.
RbMgCl3 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 Cl(1) and six equivalent Cl(2) atoms to form RbCl12 cuboctahedra that share corners with six equivalent Rb(1)Cl12 cuboctahedra, corners with six equivalent Mg(1)Cl6 octahedra, faces with two equivalent Rb(1)Cl12 cuboctahedra, faces with six equivalent Rb(2)Cl12 cuboctahedra, and faces with six equivalent Mg(1)Cl6 octahedra. The corner-sharing octahedral tilt angles are 16°. All Rb(1)-Cl(1) bond lengths are 3.55 Å. All Rb(1)-Cl(2) bond lengths are 3.66 Å. In the second Rb site, Rb(2) is bonded to six equivalent Cl(1) and six equivalent Cl(2) atoms to form RbCl12 cuboctahedra that share corners with twelve equivalent Rb(2)Cl12 cuboctahedra, faces with six equivalent Rb(1)Cl12 cuboctahedra, and faces with eight equivalent Mg(1)Cl6 octahedra. All Rb(2)-Cl(1) bond lengths are 3.61 Å. All Rb(2)-Cl(2) bond lengths are 3.55 Å. Mg(1) is bonded to three equivalent Cl(1) and three equivalent Cl(2) atoms to form MgCl6 octahedra that share corners with three equivalent Rb(1)Cl12 cuboctahedra, corners with three equivalent Mg(1)Cl6 octahedra, faces with three equivalent Rb(1)Cl12 cuboctahedra, faces with four equivalent Rb(2)Cl12 cuboctahedra, and  a faceface with one Mg(1)Cl6 octahedra. The corner-sharing octahedra are not tilted. All Mg(1)-Cl(1) bond lengths are 2.48 Å. All Mg(1)-Cl(2) bond lengths are 2.51 Å. There are two inequivalent Cl sites. In the first Cl site, Cl(1) is bonded in a distorted linear geometry to two equivalent Rb(1), two equivalent Rb(2), and two equivalent Mg(1) atoms. In the second Cl site, Cl(2) is bonded to two equivalent Rb(1), two equivalent Rb(2), and two equivalent Mg(1) atoms to form a mixture of distorted corner and face-sharing ClRb4Mg2 octahedra. The corner-sharing octahedral tilt angles range from 0-61°.