Synthesis and crystal structure of silicon pernitride SiN2 at 140 GPa

Abstract

Silicon pernitride, SiN2, was synthesized from the elements at 140 GPa in a laser-heated diamond anvil cell. Its crystal structure was solved and refined by means of synchrotron-based single-crystal X-ray diffraction data. The title compound crystallizes in the pyrite structure type (space group Pa\overline{3}, No. 205). The Si atom occupies a site with multiplicity 4 (Wyckoff letter b, site symmetry .\overline{3}.), while the N atom is located on a site with multiplicity 8 (Wyckoff letter c, site symmetry .3.). The crystal structure of SiN2 is comprised of slightly distorted [SiN6] octahedra interconnected with each other by sharing vertices. Crystal chemical analysis of bond lengths suggests that Si has a formal oxidation state of +IV, while nitrogen forms pernitride anions (N—N)4–.

Keywords

• nitrides
• pernitrides
• silicon nitrides
• high pressure
• crystal structure