Materials Data on Si3N4 by Materials Project
Si3N4 crystallizes in the trigonal P31c space group. The structure is three-dimensional. there are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded in a trigonal non-coplanar geometry to three N3- atoms. There is one shorter (1.75 Å) and two longer (1.76 Å) Si–N bond length. In the second Si4+ site, Si4+ is bonded to four N3- atoms to form corner-sharing SiN4 tetrahedra. There is one shorter (1.73 Å) and three longer (1.75 Å) Si–N bond length. There are four inequivalent N3- sites. In the first N3- site, N3- is bonded in a trigonal planar geometry to three Si4+ and two equivalent N3- atoms. There are one shorter (2.57 Å) and one longer (3.15 Å) N–N bond lengths. In the second N3- site, N3- is bonded in a trigonal planar geometry to three equivalent Si4+ atoms. In the third N3- site, N3- is bonded in a trigonal planar geometry to three Si4+ and one N3- atom. The N–N bond length is 2.83 Å. In the fourth N3- site, N3- is bonded in a 3-coordinate geometry to nine N3- atoms.