Synthesis and crystal structure of a new quaternary compound: La3AgSe7Si

A new quaternary compound La3AgSe7Si has been synthesized by solid state reaction at high temperature and its crystal structure determined. It crystallized in the hexagonal system, space group P63 with a=10.576(3) Å, c=5.907(5) Å; V=580.3(9) Å3; Z=2; Dc=6.33 g cm−3; F(000)=940; μ=34.32 cm−1. The final R and Rw are 0.0686 and 0.0839 respectively for 699 observed reflections. The structure consists of three kinds of polyhedra, LaSe8 bi-capped trigonal prism, SiSe4 tetrahedron and AgSe3 triangle. The packing of lanthanum selenide polyhedra creates channels and tetrahedral holes along the c direction which are occupied by silver and silicon atoms, respectively.