Materials Data on Si3N4 by Materials Project

Abstract

Si3N4 is Hausmannite-like structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are three inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four N3- atoms to form a mixture of corner and edge-sharing SiN4 tetrahedra. The corner-sharing octahedra tilt angles range from 62–66°. There are a spread of Si–N bond distances ranging from 1.71–1.77 Å. In the second Si4+ site, Si4+ is bonded to six N3- atoms to form SiN6 octahedra that share corners with eight SiN6 octahedra, corners with four equivalent SiN4 tetrahedra, edges with two equivalent SiN6 octahedra, and an edgeedge with one SiN4 tetrahedra. The corner-sharing octahedra tilt angles range from 49–54°. There are a spread of Si–N bond distances ranging from 1.87–2.12 Å. In the third Si4+ site, Si4+ is bonded to six N3- atoms to form SiN6 octahedra that share corners with four equivalent SiN6 octahedra, corners with two equivalent SiN4 tetrahedra, edges with four SiN6 octahedra, and edges with two equivalent SiN4 tetrahedra. The corner-sharing octahedra tilt angles range from 50–54°. There are a spread of Si–N bond distances ranging from 1.85–1.95 Å. There are three inequivalent N3- sites. In the first N3- site, N3- is bonded to four Si4+ atoms to form corner-sharing NSi4 tetrahedra. In the second N3- site, N3- is bonded in a rectangular see-saw-like geometry to four Si4+ atoms. In the third N3- site, N3- is bonded in a rectangular see-saw-like geometry to four Si4+ atoms.