Ta2Se3 crystallizes in the monoclinic P2_1/m space group. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one Se(3), two equivalent Se(2), and three equivalent Se(1) atoms to form distorted edge-sharing TaSe6 octahedra. In the second Ta site, Ta(2) is bonded in a 6-coordinate geometry to three equivalent Se(2) and three equivalent Se(3) atoms. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted T-shaped geometry to three equivalent Ta(1) atoms. In the second Se site, Se(2) is bonded in a 5-coordinate geometry to two equivalent Ta(1) and three equivalent Ta(2) atoms. In the third Se site, Se(3) is bonded in a 4-coordinate geometry to one Ta(1) and three equivalent Ta(2) atoms.
Ta2Se3 crystallizes in the monoclinic P2_1/m space group. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one Se(3), two equivalent Se(2), and three equivalent Se(1) atoms to form distorted edge-sharing TaSe6 octahedra. The Ta(1)-Se(3) bond length is 2.76 Å. Both Ta(1)-Se(2) bond lengths are 2.74 Å. There is one shorter (2.52 Å) and two longer (2.56 Å) Ta(1)-Se(1) bond lengths. In the second Ta site, Ta(2) is bonded in a 6-coordinate geometry to three equivalent Se(2) and three equivalent Se(3) atoms. There are two shorter (2.72 Å) and one longer (3.07 Å) Ta(2)-Se(2) bond length. There are two shorter (2.56 Å) and one longer (2.58 Å) Ta(2)-Se(3) bond length. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted T-shaped geometry to three equivalent Ta(1) atoms. In the second Se site, Se(2) is bonded in a 5-coordinate geometry to two equivalent Ta(1) and three equivalent Ta(2) atoms. In the third Se site, Se(3) is bonded in a 4-coordinate geometry to one Ta(1) and three equivalent Ta(2) atoms.