Crystal structure of the TbTe1.8 compound

The crystal structure of the TbTe1.8 (space group P4, a = 0.9607 (1) nm, c = 1.7875 (2) nm, Pearson symbol tP56, R1 = 0.0505) compound was determined using X-ray single crystal diffraction. Twenty atoms of Tb in the unit cell of the TbTe1.8 compound are stacked in a distorted close-packed arrangement with the layers in the sequence ABC. The Te1-Te8 atoms (20 atoms) occupy all octahedral interstices. Since these atoms are significantly shifted from the centeres of the respective octahedra five Tb atoms really surround every Te1-Te8 atoms. The remaining Te (Te9-Te14) atoms (16 atoms) are located in tetrahedral interstices. The structure of the TbTe1.8 compound represents a distinctive 5a×5a×2c superstructure of TbTe2 (UAs2 structure type, space group P4/nmm, a = 0.4334 nm, c = 0.8900 nm).