Materials Data on Na15Sn4 by Materials Project
Na15Sn4 crystallizes in the cubic I-43d space group. The structure is three-dimensional. there are two inequivalent Na sites. In the first Na site, Na is bonded to eight equivalent Na and four equivalent Sn atoms to form NaNa8Sn4 cuboctahedra that share corners with eight equivalent SnNa12 cuboctahedra, edges with eight equivalent NaNa8Sn4 cuboctahedra, and faces with four equivalent SnNa12 cuboctahedra. There are four shorter (3.39 Å) and four longer (3.45 Å) Na–Na bond lengths. All Na–Sn bond lengths are 3.56 Å. In the second Na site, Na is bonded in a 3-coordinate geometry to two equivalent Na and three equivalent Sn atoms. There are a spread of Na–Sn bond distances ranging from 3.23–3.52 Å. Sn is bonded to twelve Na atoms to form distorted SnNa12 cuboctahedra that share corners with six equivalent NaNa8Sn4 cuboctahedra, edges with six equivalent SnNa12 cuboctahedra, faces with three equivalent NaNa8Sn4 cuboctahedra, and faces with five equivalent SnNa12 cuboctahedra.