Th2Se3 is Stibnite structured and crystallizes in the orthorhombic Pnma space group. There are two inequivalent Th sites. In the first Th site, Th(1) is bonded to two equivalent Se(1), two equivalent Se(3), and three equivalent Se(2) atoms to form a mixture of distorted edge and corner-sharing ThSe7 pentagonal bipyramids. In the second Th site, Th(2) is bonded in a 7-coordinate geometry to two equivalent Se(2), two equivalent Se(3), and three equivalent Se(1) atoms. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Th(1) and three equivalent Th(2) atoms to form a mixture of distorted edge and corner-sharing SeTh5 trigonal bipyramids. In the second Se site, Se(2) is bonded to two equivalent Th(2) and three equivalent Th(1) atoms to form a mixture of edge and corner-sharing SeTh5 square pyramids. In the third Se site, Se(3) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Th(1) and two equivalent Th(2) atoms.
Th2Se3 is Stibnite structured and crystallizes in the orthorhombic Pnma space group. There are two inequivalent Th sites. In the first Th site, Th(1) is bonded to two equivalent Se(1), two equivalent Se(3), and three equivalent Se(2) atoms to form a mixture of distorted edge and corner-sharing ThSe7 pentagonal bipyramids. Both Th(1)-Se(1) bond lengths are 3.03 Å. There is one shorter (2.97 Å) and one longer (3.00 Å) Th(1)-Se(3) bond length. There is one shorter (2.98 Å) and two longer (3.01 Å) Th(1)-Se(2) bond lengths. In the second Th site, Th(2) is bonded in a 7-coordinate geometry to two equivalent Se(2), two equivalent Se(3), and three equivalent Se(1) atoms. Both Th(2)-Se(2) bond lengths are 2.99 Å. Both Th(2)-Se(3) bond lengths are 2.97 Å. There are two shorter (3.05 Å) and one longer (3.10 Å) Th(2)-Se(1) bond length. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Th(1) and three equivalent Th(2) atoms to form a mixture of distorted edge and corner-sharing SeTh5 trigonal bipyramids. In the second Se site, Se(2) is bonded to two equivalent Th(2) and three equivalent Th(1) atoms to form a mixture of edge and corner-sharing SeTh5 square pyramids. In the third Se site, Se(3) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Th(1) and two equivalent Th(2) atoms.