Na3Mg is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to eight equivalent Na(2) and four equivalent Mg(1) atoms to form distorted NaNa8Mg4 cuboctahedra that share corners with four equivalent Na(1)Na8Mg4 cuboctahedra, corners with eight equivalent Mg(1)Na12 cuboctahedra, edges with eight equivalent Na(1)Na8Mg4 cuboctahedra, edges with sixteen equivalent Na(2)Na8Mg4 cuboctahedra, faces with four equivalent Na(1)Na8Mg4 cuboctahedra, faces with six equivalent Mg(1)Na12 cuboctahedra, and faces with eight equivalent Na(2)Na8Mg4 cuboctahedra. In the second Na site, Na(2) is bonded to four equivalent Na(1), four equivalent Na(2), and four equivalent Mg(1) atoms to form NaNa8Mg4 cuboctahedra that share corners with twelve equivalent Na(2)Na8Mg4 cuboctahedra, edges with eight equivalent Na(1)Na8Mg4 cuboctahedra, edges with eight equivalent Na(2)Na8Mg4 cuboctahedra, edges with eight equivalent Mg(1)Na12 cuboctahedra, faces with four equivalent Na(1)Na8Mg4 cuboctahedra, faces with four equivalent Mg(1)Na12 cuboctahedra, and faces with ten equivalent Na(2)Na8Mg4 cuboctahedra. Mg(1) is bonded to four equivalent Na(1) and eight equivalent Na(2) atoms to form MgNa12 cuboctahedra that share corners with four equivalent Mg(1)Na12 cuboctahedra, corners with eight equivalent Na(1)Na8Mg4 cuboctahedra, edges with eight equivalent Mg(1)Na12 cuboctahedra, edges with sixteen equivalent Na(2)Na8Mg4 cuboctahedra, faces with four equivalent Mg(1)Na12 cuboctahedra, faces with six equivalent Na(1)Na8Mg4 cuboctahedra, and faces with eight equivalent Na(2)Na8Mg4 cuboctahedra.
Na3Mg is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to eight equivalent Na(2) and four equivalent Mg(1) atoms to form distorted NaNa8Mg4 cuboctahedra that share corners with four equivalent Na(1)Na8Mg4 cuboctahedra, corners with eight equivalent Mg(1)Na12 cuboctahedra, edges with eight equivalent Na(1)Na8Mg4 cuboctahedra, edges with sixteen equivalent Na(2)Na8Mg4 cuboctahedra, faces with four equivalent Na(1)Na8Mg4 cuboctahedra, faces with six equivalent Mg(1)Na12 cuboctahedra, and faces with eight equivalent Na(2)Na8Mg4 cuboctahedra. All Na(1)-Na(2) bond lengths are 3.60 Å. All Na(1)-Mg(1) bond lengths are 3.49 Å. In the second Na site, Na(2) is bonded to four equivalent Na(1), four equivalent Na(2), and four equivalent Mg(1) atoms to form NaNa8Mg4 cuboctahedra that share corners with twelve equivalent Na(2)Na8Mg4 cuboctahedra, edges with eight equivalent Na(1)Na8Mg4 cuboctahedra, edges with eight equivalent Na(2)Na8Mg4 cuboctahedra, edges with eight equivalent Mg(1)Na12 cuboctahedra, faces with four equivalent Na(1)Na8Mg4 cuboctahedra, faces with four equivalent Mg(1)Na12 cuboctahedra, and faces with ten equivalent Na(2)Na8Mg4 cuboctahedra. All Na(2)-Na(2) bond lengths are 3.49 Å. All Na(2)-Mg(1) bond lengths are 3.60 Å. Mg(1) is bonded to four equivalent Na(1) and eight equivalent Na(2) atoms to form MgNa12 cuboctahedra that share corners with four equivalent Mg(1)Na12 cuboctahedra, corners with eight equivalent Na(1)Na8Mg4 cuboctahedra, edges with eight equivalent Mg(1)Na12 cuboctahedra, edges with sixteen equivalent Na(2)Na8Mg4 cuboctahedra, faces with four equivalent Mg(1)Na12 cuboctahedra, faces with six equivalent Na(1)Na8Mg4 cuboctahedra, and faces with eight equivalent Na(2)Na8Mg4 cuboctahedra.