Na3Mg is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. Na(1) is bonded to eight equivalent Na(1) and four equivalent Mg(1) atoms to form distorted NaNa8Mg4 cuboctahedra that share corners with four equivalent Mg(1)Na12 cuboctahedra, corners with fourteen equivalent Na(1)Na8Mg4 cuboctahedra, edges with six equivalent Mg(1)Na12 cuboctahedra, edges with twelve equivalent Na(1)Na8Mg4 cuboctahedra, faces with four equivalent Mg(1)Na12 cuboctahedra, and faces with sixteen equivalent Na(1)Na8Mg4 cuboctahedra. Mg(1) is bonded to twelve equivalent Na(1) atoms to form MgNa12 cuboctahedra that share corners with six equivalent Mg(1)Na12 cuboctahedra, corners with twelve equivalent Na(1)Na8Mg4 cuboctahedra, edges with eighteen equivalent Na(1)Na8Mg4 cuboctahedra, faces with eight equivalent Mg(1)Na12 cuboctahedra, and faces with twelve equivalent Na(1)Na8Mg4 cuboctahedra.
Na3Mg is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. Na(1) is bonded to eight equivalent Na(1) and four equivalent Mg(1) atoms to form distorted NaNa8Mg4 cuboctahedra that share corners with four equivalent Mg(1)Na12 cuboctahedra, corners with fourteen equivalent Na(1)Na8Mg4 cuboctahedra, edges with six equivalent Mg(1)Na12 cuboctahedra, edges with twelve equivalent Na(1)Na8Mg4 cuboctahedra, faces with four equivalent Mg(1)Na12 cuboctahedra, and faces with sixteen equivalent Na(1)Na8Mg4 cuboctahedra. There are a spread of Na(1)-Na(1) bond distances ranging from 3.52-3.74 Å. There are two shorter (3.51 Å) and two longer (3.63 Å) Na(1)-Mg(1) bond lengths. Mg(1) is bonded to twelve equivalent Na(1) atoms to form MgNa12 cuboctahedra that share corners with six equivalent Mg(1)Na12 cuboctahedra, corners with twelve equivalent Na(1)Na8Mg4 cuboctahedra, edges with eighteen equivalent Na(1)Na8Mg4 cuboctahedra, faces with eight equivalent Mg(1)Na12 cuboctahedra, and faces with twelve equivalent Na(1)Na8Mg4 cuboctahedra.