Abstract
Na4SrSi3O9 is monoclinic, C2, a = 10.706(2), b = 10.866(2), c = 6.509(1) Å, β = 144.14(2)°, Z = 2. The structure was determined using 411 independent reflexions measured on a Nicolet P3 4-circle diffractometer; the coordinates (including anisotropic temperature factors for Sr only) refined to R = 10.4%. Extra very weak reflexions on film (with CuKα suggested a superstructure, but these could not be detected using the diffractometer (with MoKα). The compound contains infinite SiO3 chains, of a conformation not described previously. Bond lengths and angles are normal, although the Si – O – Si angle is nearly 180°; this rather large value is associated with large temperature factors for the bridging oxygen atoms. The structure is compared with those of other compounds of formula M4′M″(TO3)3 where M′ = Na, K; M″ = Ca, Sr, Ba; T = Si, Ge.
