TbAgSe2 is Caswellsilverite-like structured and crystallizes in the tetragonal I4_1md space group. Tb(1) is bonded to three equivalent Se(1) and three equivalent Se(2) atoms to form TbSe6 octahedra that share corners with two equivalent Ag(1)Se6 octahedra, corners with four equivalent Tb(1)Se6 octahedra, edges with four equivalent Tb(1)Se6 octahedra, and edges with eight equivalent Ag(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 0-5°. Ag(1) is bonded to three equivalent Se(1) and three equivalent Se(2) atoms to form AgSe6 octahedra that share corners with two equivalent Tb(1)Se6 octahedra, corners with four equivalent Ag(1)Se6 octahedra, edges with four equivalent Ag(1)Se6 octahedra, and edges with eight equivalent Tb(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 0-7°. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to three equivalent Tb(1) and three equivalent Ag(1) atoms to form a mixture of corner and edge-sharing SeTb3Ag3 octahedra. The corner-sharing octahedral tilt angles range from 0-7°. In the second Se site, Se(2) is bonded to three equivalent Tb(1) and three equivalent Ag(1) atoms to form a mixture of corner and edge-sharing SeTb3Ag3 octahedra. The corner-sharing octahedral tilt angles range from 0-5°.
TbAgSe2 is Caswellsilverite-like structured and crystallizes in the tetragonal I4_1md space group. Tb(1) is bonded to three equivalent Se(1) and three equivalent Se(2) atoms to form TbSe6 octahedra that share corners with two equivalent Ag(1)Se6 octahedra, corners with four equivalent Tb(1)Se6 octahedra, edges with four equivalent Tb(1)Se6 octahedra, and edges with eight equivalent Ag(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 0-5°. There are two shorter (2.88 Å) and one longer (2.89 Å) Tb(1)-Se(1) bond length. There are two shorter (2.88 Å) and one longer (2.90 Å) Tb(1)-Se(2) bond length. Ag(1) is bonded to three equivalent Se(1) and three equivalent Se(2) atoms to form AgSe6 octahedra that share corners with two equivalent Tb(1)Se6 octahedra, corners with four equivalent Ag(1)Se6 octahedra, edges with four equivalent Ag(1)Se6 octahedra, and edges with eight equivalent Tb(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 0-7°. There are two shorter (2.88 Å) and one longer (3.19 Å) Ag(1)-Se(1) bond length. There are two shorter (2.88 Å) and one longer (3.07 Å) Ag(1)-Se(2) bond length. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to three equivalent Tb(1) and three equivalent Ag(1) atoms to form a mixture of corner and edge-sharing SeTb3Ag3 octahedra. The corner-sharing octahedral tilt angles range from 0-7°. In the second Se site, Se(2) is bonded to three equivalent Tb(1) and three equivalent Ag(1) atoms to form a mixture of corner and edge-sharing SeTb3Ag3 octahedra. The corner-sharing octahedral tilt angles range from 0-5°.