Synthesis and crystal structure of silver nesosilicate, Ag4SiO4

The new silver silicate Ag4SiO4 has been obtained by solid state reactions, starting from stoichiometric amounts of the binary oxides at elevated temperatures and oxygen pressures. Ag4SiO4 crystallizes in space group P4(2/n) (No. 86) with a = 7.3169(3), c = 4.9595(4) angstrom, V = 265.52(3) angstrom(3), Z = 2; the structure refinement was based on 343 independent reflections and resulted in R-1 = 2.70 %, wR(2) = 5.85%. The crystal structure consists of isolated SiO4 tetrahedra which are linked by Ag cations. The Ag atoms are almost linearly coordinated by two oxygen atoms. The AgO2 dumbbells form chains, and every two of these chains are wound around each other forming double helices running along [001]. This arrangement of Ag and O atoms corresponds to a section of the Ag2O structure. Ag4SiO4 is photosensitive and decomposes within a few weeks into silver, SiO2 and oxygen.