SrSi_6N_8 - A Reduced Nitridosilicate with a Si-Si Bond

摘要

Silicates are a very important class of minerals that form about 80 wt % of the earth's crust. Nearly all naturally occurring silicates are oxosilicates. However, sinoite (Si2N2O), a mineral that occurs in meteorites, contains a framework of corner-sharing Si(O,N)_4 tetrahedrons.[1], [2] In the past few years an increasing number of nitridosilicates has been synthesized. The characteristic structural entities in oxo- and nitridosilicates as well as in oxonitridosilicates (sions) are SiX4 tetrahedrons (X=O, N), which are typically connected through common corners (X=O, N)[3a] or edges (X=N).[3b] Higher coordination numbers of silicon (CN>4) mainly occur in high-pressure phases (e.g. the SiO_2 polymorph stishovite or perovskite-type (Mg,Fe)SiO_3).