Nb5SnSe8 crystallizes in the monoclinic C2/m space group. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to two equivalent Se(2) and four equivalent Se(1) atoms to form a mixture of distorted corner and edge-sharing NbSe6 octahedra. The corner-sharing octahedral tilt angles are 49°. In the second Nb site, Nb(2) is bonded in a 6-coordinate geometry to one Se(1), two equivalent Se(2), and three equivalent Se(4) atoms. In the third Nb site, Nb(3) is bonded to one Se(1), two equivalent Se(4), and three equivalent Se(3) atoms to form a mixture of distorted corner and edge-sharing NbSe6 octahedra. The corner-sharing octahedral tilt angles are 49°. Sn(1) is bonded in a 4-coordinate geometry to four equivalent Se(3) atoms. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded in a 4-coordinate geometry to one Nb(2), one Nb(3), and two equivalent Nb(1) atoms. In the second Se site, Se(2) is bonded in a 3-coordinate geometry to one Nb(1) and two equivalent Nb(2) atoms. In the third Se site, Se(3) is bonded in a 3-coordinate geometry to three equivalent Nb(3) and two equivalent Sn(1) atoms. In the fourth Se site, Se(4) is bonded in a 5-coordinate geometry to two equivalent Nb(3) and three equivalent Nb(2) atoms.
Nb5SnSe8 crystallizes in the monoclinic C2/m space group. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to two equivalent Se(2) and four equivalent Se(1) atoms to form a mixture of distorted corner and edge-sharing NbSe6 octahedra. The corner-sharing octahedral tilt angles are 49°. Both Nb(1)-Se(2) bond lengths are 2.67 Å. All Nb(1)-Se(1) bond lengths are 2.67 Å. In the second Nb site, Nb(2) is bonded in a 6-coordinate geometry to one Se(1), two equivalent Se(2), and three equivalent Se(4) atoms. The Nb(2)-Se(1) bond length is 2.54 Å. Both Nb(2)-Se(2) bond lengths are 2.56 Å. There are two shorter (2.74 Å) and one longer (2.94 Å) Nb(2)-Se(4) bond length. In the third Nb site, Nb(3) is bonded to one Se(1), two equivalent Se(4), and three equivalent Se(3) atoms to form a mixture of distorted corner and edge-sharing NbSe6 octahedra. The corner-sharing octahedral tilt angles are 49°. The Nb(3)-Se(1) bond length is 2.78 Å. Both Nb(3)-Se(4) bond lengths are 2.78 Å. There is one shorter (2.57 Å) and two longer (2.60 Å) Nb(3)-Se(3) bond lengths. Sn(1) is bonded in a 4-coordinate geometry to four equivalent Se(3) atoms. All Sn(1)-Se(3) bond lengths are 3.28 Å. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded in a 4-coordinate geometry to one Nb(2), one Nb(3), and two equivalent Nb(1) atoms. In the second Se site, Se(2) is bonded in a 3-coordinate geometry to one Nb(1) and two equivalent Nb(2) atoms. In the third Se site, Se(3) is bonded in a 3-coordinate geometry to three equivalent Nb(3) and two equivalent Sn(1) atoms. In the fourth Se site, Se(4) is bonded in a 5-coordinate geometry to two equivalent Nb(3) and three equivalent Nb(2) atoms.