Na6Ge2Se7 crystallizes in the monoclinic C2/c space group. There are four inequivalent Na sites. In the first Na site, Na(1) is bonded to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms to form NaSe6 octahedra that share corners with two equivalent Ge(1)Se4 tetrahedra and edges with two equivalent Ge(1)Se4 tetrahedra. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to one Se(1), one Se(4), two equivalent Se(2), and two equivalent Se(3) atoms. In the third Na site, Na(3) is bonded in a 4-coordinate geometry to two equivalent Se(1) and two equivalent Se(3) atoms. In the fourth Na site, Na(4) is bonded in a 6-coordinate geometry to one Se(3), one Se(4), two equivalent Se(1), and two equivalent Se(2) atoms. Ge(1) is bonded to one Se(1), one Se(2), one Se(3), and one Se(4) atom to form GeSe4 tetrahedra that share  a cornercorner with one Na(1)Se6 octahedra,  a cornercorner with one Ge(1)Se4 tetrahedra, and  an edgeedge with one Na(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 20°. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to one Na(1), one Na(2), one Na(3), two equivalent Na(4), and one Ge(1) atom to form a mixture of distorted edge, corner, and face-sharing SeNa5Ge octahedra. The corner-sharing octahedral tilt angles range from 0-71°. In the second Se site, Se(2) is bonded to one Na(1), two equivalent Na(2), two equivalent Na(4), and one Ge(1) atom to form a mixture of edge and corner-sharing SeNa5Ge octahedra. The corner-sharing octahedral tilt angles range from 0-54°. In the third Se site, Se(3) is bonded to one Na(1), one Na(3), one Na(4), two equivalent Na(2), and one Ge(1) atom to form a mixture of edge and corner-sharing SeNa5Ge octahedra. The corner-sharing octahedral tilt angles range from 0-75°. In the fourth Se site, Se(4) is bonded in a 2-coordinate geometry to two equivalent Na(2), two equivalent Na(4), and two equivalent Ge(1) atoms.
Na6Ge2Se7 crystallizes in the monoclinic C2/c space group. There are four inequivalent Na sites. In the first Na site, Na(1) is bonded to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms to form NaSe6 octahedra that share corners with two equivalent Ge(1)Se4 tetrahedra and edges with two equivalent Ge(1)Se4 tetrahedra. Both Na(1)-Se(1) bond lengths are 3.11 Å. Both Na(1)-Se(2) bond lengths are 2.88 Å. Both Na(1)-Se(3) bond lengths are 3.18 Å. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to one Se(1), one Se(4), two equivalent Se(2), and two equivalent Se(3) atoms. The Na(2)-Se(1) bond length is 2.99 Å. The Na(2)-Se(4) bond length is 3.47 Å. There is one shorter (2.99 Å) and one longer (3.02 Å) Na(2)-Se(2) bond length. There is one shorter (2.99 Å) and one longer (3.20 Å) Na(2)-Se(3) bond length. In the third Na site, Na(3) is bonded in a 4-coordinate geometry to two equivalent Se(1) and two equivalent Se(3) atoms. Both Na(3)-Se(1) bond lengths are 2.90 Å. Both Na(3)-Se(3) bond lengths are 2.83 Å. In the fourth Na site, Na(4) is bonded in a 6-coordinate geometry to one Se(3), one Se(4), two equivalent Se(1), and two equivalent Se(2) atoms. The Na(4)-Se(3) bond length is 2.98 Å. The Na(4)-Se(4) bond length is 3.56 Å. There is one shorter (2.97 Å) and one longer (3.40 Å) Na(4)-Se(1) bond length. There is one shorter (2.98 Å) and one longer (3.09 Å) Na(4)-Se(2) bond length. Ge(1) is bonded to one Se(1), one Se(2), one Se(3), and one Se(4) atom to form GeSe4 tetrahedra that share  a cornercorner with one Na(1)Se6 octahedra,  a cornercorner with one Ge(1)Se4 tetrahedra, and  an edgeedge with one Na(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 20°. The Ge(1)-Se(1) bond length is 2.35 Å. The Ge(1)-Se(2) bond length is 2.36 Å. The Ge(1)-Se(3) bond length is 2.33 Å. The Ge(1)-Se(4) bond length is 2.41 Å. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to one Na(1), one Na(2), one Na(3), two equivalent Na(4), and one Ge(1) atom to form a mixture of distorted edge, corner, and face-sharing SeNa5Ge octahedra. The corner-sharing octahedral tilt angles range from 0-71°. In the second Se site, Se(2) is bonded to one Na(1), two equivalent Na(2), two equivalent Na(4), and one Ge(1) atom to form a mixture of edge and corner-sharing SeNa5Ge octahedra. The corner-sharing octahedral tilt angles range from 0-54°. In the third Se site, Se(3) is bonded to one Na(1), one Na(3), one Na(4), two equivalent Na(2), and one Ge(1) atom to form a mixture of edge and corner-sharing SeNa5Ge octahedra. The corner-sharing octahedral tilt angles range from 0-75°. In the fourth Se site, Se(4) is bonded in a 2-coordinate geometry to two equivalent Na(2), two equivalent Na(4), and two equivalent Ge(1) atoms.