Na2TeSe3 crystallizes in the monoclinic C2/c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to one Se(2), one Se(3), and four equivalent Se(1) atoms to form a mixture of edge and corner-sharing NaSe6 octahedra. The corner-sharing octahedral tilt angles range from 5-7°. In the second Na site, Na(2) is bonded to one Se(1), two equivalent Se(3), and three equivalent Se(2) atoms to form a mixture of distorted edge and corner-sharing NaSe6 octahedra. The corner-sharing octahedral tilt angles range from 7-15°. Te(1) is bonded in a trigonal non-coplanar geometry to one Se(1), one Se(2), and one Se(3) atom. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to one Na(2), four equivalent Na(1), and one Te(1) atom to form SeNa5Te octahedra that share corners with four equivalent Se(1)Na5Te octahedra, corners with two equivalent Se(2)Na4Te square pyramids, edges with four equivalent Se(1)Na5Te octahedra, and edges with three equivalent Se(2)Na4Te square pyramids. The corner-sharing octahedral tilt angles range from 5-7°. In the second Se site, Se(2) is bonded to one Na(1), three equivalent Na(2), and one Te(1) atom to form SeNa4Te square pyramids that share corners with two equivalent Se(1)Na5Te octahedra, corners with two equivalent Se(2)Na4Te square pyramids, edges with three equivalent Se(1)Na5Te octahedra, and edges with two equivalent Se(2)Na4Te square pyramids. The corner-sharing octahedral tilt angles range from 4-88°. In the third Se site, Se(3) is bonded in a rectangular see-saw-like geometry to one Na(1), two equivalent Na(2), and one Te(1) atom.
Na2TeSe3 crystallizes in the monoclinic C2/c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to one Se(2), one Se(3), and four equivalent Se(1) atoms to form a mixture of edge and corner-sharing NaSe6 octahedra. The corner-sharing octahedral tilt angles range from 5-7°. The Na(1)-Se(2) bond length is 3.02 Å. The Na(1)-Se(3) bond length is 3.03 Å. There are three shorter (3.01 Å) and one longer (3.02 Å) Na(1)-Se(1) bond length. In the second Na site, Na(2) is bonded to one Se(1), two equivalent Se(3), and three equivalent Se(2) atoms to form a mixture of distorted edge and corner-sharing NaSe6 octahedra. The corner-sharing octahedral tilt angles range from 7-15°. The Na(2)-Se(1) bond length is 3.47 Å. Both Na(2)-Se(3) bond lengths are 3.02 Å. There are a spread of Na(2)-Se(2) bond distances ranging from 3.01-3.05 Å. Te(1) is bonded in a trigonal non-coplanar geometry to one Se(1), one Se(2), and one Se(3) atom. The Te(1)-Se(1) bond length is 2.51 Å. The Te(1)-Se(2) bond length is 2.53 Å. The Te(1)-Se(3) bond length is 2.52 Å. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to one Na(2), four equivalent Na(1), and one Te(1) atom to form SeNa5Te octahedra that share corners with four equivalent Se(1)Na5Te octahedra, corners with two equivalent Se(2)Na4Te square pyramids, edges with four equivalent Se(1)Na5Te octahedra, and edges with three equivalent Se(2)Na4Te square pyramids. The corner-sharing octahedral tilt angles range from 5-7°. In the second Se site, Se(2) is bonded to one Na(1), three equivalent Na(2), and one Te(1) atom to form SeNa4Te square pyramids that share corners with two equivalent Se(1)Na5Te octahedra, corners with two equivalent Se(2)Na4Te square pyramids, edges with three equivalent Se(1)Na5Te octahedra, and edges with two equivalent Se(2)Na4Te square pyramids. The corner-sharing octahedral tilt angles range from 4-88°. In the third Se site, Se(3) is bonded in a rectangular see-saw-like geometry to one Na(1), two equivalent Na(2), and one Te(1) atom.