Sr3Mg crystallizes in the orthorhombic Pmm2 space group. There are three inequivalent Sr sites. In the first Sr site, Sr(1) is bonded to two equivalent Sr(1), four equivalent Sr(2), four equivalent Sr(3), and two equivalent Mg(1) atoms to form distorted SrSr10Mg2 cuboctahedra that share corners with eight equivalent Sr(2)Sr8Mg4 cuboctahedra, corners with ten equivalent Sr(1)Sr10Mg2 cuboctahedra, edges with two equivalent Sr(1)Sr10Mg2 cuboctahedra, edges with four equivalent Sr(2)Sr8Mg4 cuboctahedra, edges with eight equivalent Sr(3)Sr8Mg4 cuboctahedra, faces with four equivalent Sr(1)Sr10Mg2 cuboctahedra, faces with four equivalent Sr(2)Sr8Mg4 cuboctahedra, and faces with four equivalent Sr(3)Sr8Mg4 cuboctahedra. In the second Sr site, Sr(2) is bonded to two equivalent Sr(2), two equivalent Sr(3), four equivalent Sr(1), and four equivalent Mg(1) atoms to form distorted SrSr8Mg4 cuboctahedra that share corners with eight equivalent Sr(1)Sr10Mg2 cuboctahedra, corners with ten equivalent Sr(2)Sr8Mg4 cuboctahedra, edges with two equivalent Sr(2)Sr8Mg4 cuboctahedra, edges with four equivalent Sr(1)Sr10Mg2 cuboctahedra, edges with four equivalent Sr(3)Sr8Mg4 cuboctahedra, faces with four equivalent Sr(1)Sr10Mg2 cuboctahedra, faces with four equivalent Sr(2)Sr8Mg4 cuboctahedra, and faces with eight equivalent Sr(3)Sr8Mg4 cuboctahedra. In the third Sr site, Sr(3) is bonded to two equivalent Sr(2), two equivalent Sr(3), four equivalent Sr(1), and four equivalent Mg(1) atoms to form distorted SrSr8Mg4 cuboctahedra that share corners with ten equivalent Sr(3)Sr8Mg4 cuboctahedra, edges with two equivalent Sr(3)Sr8Mg4 cuboctahedra, edges with four equivalent Sr(2)Sr8Mg4 cuboctahedra, edges with eight equivalent Sr(1)Sr10Mg2 cuboctahedra, faces with four equivalent Sr(1)Sr10Mg2 cuboctahedra, faces with four equivalent Sr(3)Sr8Mg4 cuboctahedra, and faces with eight equivalent Sr(2)Sr8Mg4 cuboctahedra. Mg(1) is bonded in a 10-coordinate geometry to two equivalent Sr(1), four equivalent Sr(2), and four equivalent Sr(3) atoms.
Sr3Mg crystallizes in the orthorhombic Pmm2 space group. There are three inequivalent Sr sites. In the first Sr site, Sr(1) is bonded to two equivalent Sr(1), four equivalent Sr(2), four equivalent Sr(3), and two equivalent Mg(1) atoms to form distorted SrSr10Mg2 cuboctahedra that share corners with eight equivalent Sr(2)Sr8Mg4 cuboctahedra, corners with ten equivalent Sr(1)Sr10Mg2 cuboctahedra, edges with two equivalent Sr(1)Sr10Mg2 cuboctahedra, edges with four equivalent Sr(2)Sr8Mg4 cuboctahedra, edges with eight equivalent Sr(3)Sr8Mg4 cuboctahedra, faces with four equivalent Sr(1)Sr10Mg2 cuboctahedra, faces with four equivalent Sr(2)Sr8Mg4 cuboctahedra, and faces with four equivalent Sr(3)Sr8Mg4 cuboctahedra. Both Sr(1)-Sr(1) bond lengths are 4.22 Å. There are two shorter (3.89 Å) and two longer (4.12 Å) Sr(1)-Sr(2) bond lengths. All Sr(1)-Sr(3) bond lengths are 3.97 Å. Both Sr(1)-Mg(1) bond lengths are 3.90 Å. In the second Sr site, Sr(2) is bonded to two equivalent Sr(2), two equivalent Sr(3), four equivalent Sr(1), and four equivalent Mg(1) atoms to form distorted SrSr8Mg4 cuboctahedra that share corners with eight equivalent Sr(1)Sr10Mg2 cuboctahedra, corners with ten equivalent Sr(2)Sr8Mg4 cuboctahedra, edges with two equivalent Sr(2)Sr8Mg4 cuboctahedra, edges with four equivalent Sr(1)Sr10Mg2 cuboctahedra, edges with four equivalent Sr(3)Sr8Mg4 cuboctahedra, faces with four equivalent Sr(1)Sr10Mg2 cuboctahedra, faces with four equivalent Sr(2)Sr8Mg4 cuboctahedra, and faces with eight equivalent Sr(3)Sr8Mg4 cuboctahedra. Both Sr(2)-Sr(2) bond lengths are 4.22 Å. Both Sr(2)-Sr(3) bond lengths are 4.01 Å. All Sr(2)-Mg(1) bond lengths are 3.95 Å. In the third Sr site, Sr(3) is bonded to two equivalent Sr(2), two equivalent Sr(3), four equivalent Sr(1), and four equivalent Mg(1) atoms to form distorted SrSr8Mg4 cuboctahedra that share corners with ten equivalent Sr(3)Sr8Mg4 cuboctahedra, edges with two equivalent Sr(3)Sr8Mg4 cuboctahedra, edges with four equivalent Sr(2)Sr8Mg4 cuboctahedra, edges with eight equivalent Sr(1)Sr10Mg2 cuboctahedra, faces with four equivalent Sr(1)Sr10Mg2 cuboctahedra, faces with four equivalent Sr(3)Sr8Mg4 cuboctahedra, and faces with eight equivalent Sr(2)Sr8Mg4 cuboctahedra. Both Sr(3)-Sr(3) bond lengths are 4.22 Å. There are two shorter (3.97 Å) and two longer (4.04 Å) Sr(3)-Mg(1) bond lengths. Mg(1) is bonded in a 10-coordinate geometry to two equivalent Sr(1), four equivalent Sr(2), and four equivalent Sr(3) atoms.