Na3SiTe3 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded in a 5-coordinate geometry to one Te(1), two equivalent Te(2), and two equivalent Te(3) atoms. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to two equivalent Te(1), two equivalent Te(2), and two equivalent Te(3) atoms. In the third Na site, Na(3) is bonded in a 6-coordinate geometry to two equivalent Te(1), two equivalent Te(2), and two equivalent Te(3) atoms. Si(1) is bonded to one Si(1), one Te(1), one Te(2), and one Te(3) atom to form SiSiTe3 tetrahedra that share  a cornercorner with one Te(2)Na6Si pentagonal bipyramid and  a cornercorner with one Te(3)Na6Si pentagonal bipyramid. There are three inequivalent Te sites. In the first Te site, Te(1) is bonded in a 6-coordinate geometry to one Na(1), two equivalent Na(2), two equivalent Na(3), and one Si(1) atom. In the second Te site, Te(2) is bonded to two equivalent Na(1), two equivalent Na(2), two equivalent Na(3), and one Si(1) atom to form distorted TeNa6Si pentagonal bipyramids that share corners with two equivalent Te(2)Na6Si pentagonal bipyramids, corners with three equivalent Te(3)Na6Si pentagonal bipyramids,  a cornercorner with one Si(1)SiTe3 tetrahedra, edges with two equivalent Te(2)Na6Si pentagonal bipyramids, edges with two equivalent Te(3)Na6Si pentagonal bipyramids, and faces with two equivalent Te(3)Na6Si pentagonal bipyramids. In the third Te site, Te(3) is bonded to two equivalent Na(1), two equivalent Na(2), two equivalent Na(3), and one Si(1) atom to form distorted TeNa6Si pentagonal bipyramids that share corners with three equivalent Te(2)Na6Si pentagonal bipyramids,  a cornercorner with one Si(1)SiTe3 tetrahedra, edges with two equivalent Te(2)Na6Si pentagonal bipyramids, faces with two equivalent Te(2)Na6Si pentagonal bipyramids, and faces with two equivalent Te(3)Na6Si pentagonal bipyramids.
Na3SiTe3 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded in a 5-coordinate geometry to one Te(1), two equivalent Te(2), and two equivalent Te(3) atoms. The Na(1)-Te(1) bond length is 3.12 Å. There is one shorter (3.38 Å) and one longer (3.60 Å) Na(1)-Te(2) bond length. There is one shorter (3.13 Å) and one longer (3.30 Å) Na(1)-Te(3) bond length. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to two equivalent Te(1), two equivalent Te(2), and two equivalent Te(3) atoms. There is one shorter (3.18 Å) and one longer (3.24 Å) Na(2)-Te(1) bond length. There is one shorter (3.29 Å) and one longer (3.43 Å) Na(2)-Te(2) bond length. There is one shorter (3.42 Å) and one longer (3.59 Å) Na(2)-Te(3) bond length. In the third Na site, Na(3) is bonded in a 6-coordinate geometry to two equivalent Te(1), two equivalent Te(2), and two equivalent Te(3) atoms. There is one shorter (3.22 Å) and one longer (3.56 Å) Na(3)-Te(1) bond length. There is one shorter (3.27 Å) and one longer (3.52 Å) Na(3)-Te(2) bond length. There is one shorter (3.18 Å) and one longer (3.39 Å) Na(3)-Te(3) bond length. Si(1) is bonded to one Si(1), one Te(1), one Te(2), and one Te(3) atom to form SiSiTe3 tetrahedra that share  a cornercorner with one Te(2)Na6Si pentagonal bipyramid and  a cornercorner with one Te(3)Na6Si pentagonal bipyramid. The Si(1)-Si(1) bond length is 2.38 Å. The Si(1)-Te(1) bond length is 2.54 Å. The Si(1)-Te(2) bond length is 2.53 Å. The Si(1)-Te(3) bond length is 2.54 Å. There are three inequivalent Te sites. In the first Te site, Te(1) is bonded in a 6-coordinate geometry to one Na(1), two equivalent Na(2), two equivalent Na(3), and one Si(1) atom. In the second Te site, Te(2) is bonded to two equivalent Na(1), two equivalent Na(2), two equivalent Na(3), and one Si(1) atom to form distorted TeNa6Si pentagonal bipyramids that share corners with two equivalent Te(2)Na6Si pentagonal bipyramids, corners with three equivalent Te(3)Na6Si pentagonal bipyramids,  a cornercorner with one Si(1)SiTe3 tetrahedra, edges with two equivalent Te(2)Na6Si pentagonal bipyramids, edges with two equivalent Te(3)Na6Si pentagonal bipyramids, and faces with two equivalent Te(3)Na6Si pentagonal bipyramids. In the third Te site, Te(3) is bonded to two equivalent Na(1), two equivalent Na(2), two equivalent Na(3), and one Si(1) atom to form distorted TeNa6Si pentagonal bipyramids that share corners with three equivalent Te(2)Na6Si pentagonal bipyramids,  a cornercorner with one Si(1)SiTe3 tetrahedra, edges with two equivalent Te(2)Na6Si pentagonal bipyramids, faces with two equivalent Te(2)Na6Si pentagonal bipyramids, and faces with two equivalent Te(3)Na6Si pentagonal bipyramids.