Na15Pb4 crystallizes in the cubic I-43d 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 Pb(1) atoms to form distorted NaNa8Pb4 cuboctahedra that share corners with eight equivalent Pb(1)Na12 cuboctahedra, edges with eight equivalent Na(1)Na8Pb4 cuboctahedra, and faces with four equivalent Pb(1)Na12 cuboctahedra. In the second Na site, Na(2) is bonded in a 3-coordinate geometry to two equivalent Na(1) and three equivalent Pb(1) atoms. Pb(1) is bonded to three equivalent Na(1) and nine equivalent Na(2) atoms to form distorted PbNa12 cuboctahedra that share corners with six equivalent Na(1)Na8Pb4 cuboctahedra, edges with six equivalent Pb(1)Na12 cuboctahedra, faces with three equivalent Na(1)Na8Pb4 cuboctahedra, and faces with five equivalent Pb(1)Na12 cuboctahedra.
Na15Pb4 crystallizes in the cubic I-43d 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 Pb(1) atoms to form distorted NaNa8Pb4 cuboctahedra that share corners with eight equivalent Pb(1)Na12 cuboctahedra, edges with eight equivalent Na(1)Na8Pb4 cuboctahedra, and faces with four equivalent Pb(1)Na12 cuboctahedra. All Na(1)-Na(2) bond lengths are 3.41 Å. All Na(1)-Pb(1) bond lengths are 3.55 Å. In the second Na site, Na(2) is bonded in a 3-coordinate geometry to two equivalent Na(1) and three equivalent Pb(1) atoms. There are a spread of Na(2)-Pb(1) bond distances ranging from 3.22-3.52 Å. Pb(1) is bonded to three equivalent Na(1) and nine equivalent Na(2) atoms to form distorted PbNa12 cuboctahedra that share corners with six equivalent Na(1)Na8Pb4 cuboctahedra, edges with six equivalent Pb(1)Na12 cuboctahedra, faces with three equivalent Na(1)Na8Pb4 cuboctahedra, and faces with five equivalent Pb(1)Na12 cuboctahedra.