Synthesis and Crystal Structure of Nd_2Si_2O_7 in Low Temperature Form

The title compound was obtained by high temperature solid state reaction and flux method. The crystal belongs to tetragonal system, space group P41, withcell dimensions a= 6. 738(2), c= 24. 532 (3) A, V= 1113. 8(3) A 3, Z= 8, Mr =456. 65, Dc= 5. 45 g/cm3, F(000) = 1632, μ= 189. 3 cm-1. R=0.052, Rw=0. 059.The structure consists of isolated Si2O7 double tetrahedra which are arranged in layersperpendicular to the c axis. Four crystallographically different rare earth atoms in oneunit cell are located on each side of the layers and connect the four nearest SiO4 tetrahedra to form a three-dimensional network structure.