Mg3Os is alpha bismuth trifluoride structured and crystallizes in the tetragonal I4/mmm space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to eight equivalent Mg(2) and four equivalent Os(1) atoms to form MgMg8Os4 cuboctahedra that share corners with four equivalent Mg(1)Mg8Os4 cuboctahedra, corners with eight equivalent Os(1)Mg12 cuboctahedra, edges with eight equivalent Mg(1)Mg8Os4 cuboctahedra, faces with four equivalent Mg(1)Mg8Os4 cuboctahedra, and faces with six equivalent Os(1)Mg12 cuboctahedra. In the second Mg site, Mg(2) is bonded in a 4-coordinate geometry to four equivalent Mg(1) and four equivalent Os(1) atoms. Os(1) is bonded to four equivalent Mg(1) and eight equivalent Mg(2) atoms to form OsMg12 cuboctahedra that share corners with four equivalent Os(1)Mg12 cuboctahedra, corners with eight equivalent Mg(1)Mg8Os4 cuboctahedra, edges with eight equivalent Os(1)Mg12 cuboctahedra, faces with four equivalent Os(1)Mg12 cuboctahedra, and faces with six equivalent Mg(1)Mg8Os4 cuboctahedra.
Mg3Os is alpha bismuth trifluoride structured and crystallizes in the tetragonal I4/mmm space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to eight equivalent Mg(2) and four equivalent Os(1) atoms to form MgMg8Os4 cuboctahedra that share corners with four equivalent Mg(1)Mg8Os4 cuboctahedra, corners with eight equivalent Os(1)Mg12 cuboctahedra, edges with eight equivalent Mg(1)Mg8Os4 cuboctahedra, faces with four equivalent Mg(1)Mg8Os4 cuboctahedra, and faces with six equivalent Os(1)Mg12 cuboctahedra. All Mg(1)-Mg(2) bond lengths are 2.86 Å. All Mg(1)-Os(1) bond lengths are 2.99 Å. In the second Mg site, Mg(2) is bonded in a 4-coordinate geometry to four equivalent Mg(1) and four equivalent Os(1) atoms. All Mg(2)-Os(1) bond lengths are 2.86 Å. Os(1) is bonded to four equivalent Mg(1) and eight equivalent Mg(2) atoms to form OsMg12 cuboctahedra that share corners with four equivalent Os(1)Mg12 cuboctahedra, corners with eight equivalent Mg(1)Mg8Os4 cuboctahedra, edges with eight equivalent Os(1)Mg12 cuboctahedra, faces with four equivalent Os(1)Mg12 cuboctahedra, and faces with six equivalent Mg(1)Mg8Os4 cuboctahedra.