KMg3 crystallizes in the orthorhombic Pmm2 space group. K(1) is bonded to two equivalent K(1), two equivalent Mg(3), four equivalent Mg(1), and four equivalent Mg(2) atoms to form distorted KK2Mg10 cuboctahedra that share corners with eight equivalent Mg(1)K4Mg8 cuboctahedra, corners with ten equivalent K(1)K2Mg10 cuboctahedra, edges with two equivalent K(1)K2Mg10 cuboctahedra, edges with four equivalent Mg(1)K4Mg8 cuboctahedra, faces with four equivalent K(1)K2Mg10 cuboctahedra, and faces with four equivalent Mg(1)K4Mg8 cuboctahedra. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to four equivalent K(1), two equivalent Mg(1), two equivalent Mg(2), and four equivalent Mg(3) atoms to form MgK4Mg8 cuboctahedra that share corners with eight equivalent K(1)K2Mg10 cuboctahedra, corners with ten equivalent Mg(1)K4Mg8 cuboctahedra, edges with two equivalent Mg(1)K4Mg8 cuboctahedra, edges with four equivalent K(1)K2Mg10 cuboctahedra, faces with four equivalent K(1)K2Mg10 cuboctahedra, and faces with four equivalent Mg(1)K4Mg8 cuboctahedra. In the second Mg site, Mg(2) is bonded in a 10-coordinate geometry to four equivalent K(1), two equivalent Mg(1), two equivalent Mg(2), and two equivalent Mg(3) atoms. In the third Mg site, Mg(3) is bonded in a 10-coordinate geometry to two equivalent K(1), two equivalent Mg(2), two equivalent Mg(3), and four equivalent Mg(1) atoms.
KMg3 crystallizes in the orthorhombic Pmm2 space group. K(1) is bonded to two equivalent K(1), two equivalent Mg(3), four equivalent Mg(1), and four equivalent Mg(2) atoms to form distorted KK2Mg10 cuboctahedra that share corners with eight equivalent Mg(1)K4Mg8 cuboctahedra, corners with ten equivalent K(1)K2Mg10 cuboctahedra, edges with two equivalent K(1)K2Mg10 cuboctahedra, edges with four equivalent Mg(1)K4Mg8 cuboctahedra, faces with four equivalent K(1)K2Mg10 cuboctahedra, and faces with four equivalent Mg(1)K4Mg8 cuboctahedra. Both K(1)-K(1) bond lengths are 3.24 Å. Both K(1)-Mg(3) bond lengths are 3.64 Å. There are two shorter (3.93 Å) and two longer (4.04 Å) K(1)-Mg(1) bond lengths. All K(1)-Mg(2) bond lengths are 3.69 Å. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to four equivalent K(1), two equivalent Mg(1), two equivalent Mg(2), and four equivalent Mg(3) atoms to form MgK4Mg8 cuboctahedra that share corners with eight equivalent K(1)K2Mg10 cuboctahedra, corners with ten equivalent Mg(1)K4Mg8 cuboctahedra, edges with two equivalent Mg(1)K4Mg8 cuboctahedra, edges with four equivalent K(1)K2Mg10 cuboctahedra, faces with four equivalent K(1)K2Mg10 cuboctahedra, and faces with four equivalent Mg(1)K4Mg8 cuboctahedra. Both Mg(1)-Mg(1) bond lengths are 3.24 Å. Both Mg(1)-Mg(2) bond lengths are 3.13 Å. All Mg(1)-Mg(3) bond lengths are 3.27 Å. In the second Mg site, Mg(2) is bonded in a 10-coordinate geometry to four equivalent K(1), two equivalent Mg(1), two equivalent Mg(2), and two equivalent Mg(3) atoms. Both Mg(2)-Mg(2) bond lengths are 3.24 Å. Both Mg(2)-Mg(3) bond lengths are 3.19 Å. In the third Mg site, Mg(3) is bonded in a 10-coordinate geometry to two equivalent K(1), two equivalent Mg(2), two equivalent Mg(3), and four equivalent Mg(1) atoms. Both Mg(3)-Mg(3) bond lengths are 3.24 Å.