Materials Data on Na3Si17 by Materials Project
NaNa2Si17 crystallizes in the cubic Fd-3m space group. The structure is three-dimensional and consists of eight sodium molecules and one Na2Si17 framework. In the Na2Si17 framework, Na is bonded in a 8-coordinate geometry to twenty Si atoms. There are a spread of Na–Si bond distances ranging from 3.20–3.39 Å. There are three inequivalent Si sites. In the first Si site, Si is bonded in a body-centered cubic geometry to four equivalent Na and four equivalent Si atoms. All Si–Si bond lengths are 2.39 Å. In the second Si site, Si is bonded in a 7-coordinate geometry to three equivalent Na and four Si atoms. All Si–Si bond lengths are 2.39 Å. In the third Si site, Si is bonded in a 4-coordinate geometry to two equivalent Na and four Si atoms. There are two shorter (2.38 Å) and one longer (2.40 Å) Si–Si bond lengths.