Li6Si2O7 crystallizes in the tetragonal P-42_1m space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded in a distorted rectangular see-saw-like geometry to one O(2) and three equivalent O(1) atoms. In the second Li site, Li(2) is bonded to one O(3), two equivalent O(1), and two equivalent O(2) atoms to form distorted LiO5 trigonal bipyramids that share corners with four equivalent Si(1)O4 tetrahedra,  an edgeedge with one Si(1)O4 tetrahedra, and  a faceface with one Li(2)O5 trigonal bipyramid. Si(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra, corners with four equivalent Li(2)O5 trigonal bipyramids, and  an edgeedge with one Li(2)O5 trigonal bipyramid. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to one Li(2), three equivalent Li(1), and one Si(1) atom. In the second O site, O(2) is bonded in a 5-coordinate geometry to two equivalent Li(1), two equivalent Li(2), and one Si(1) atom. In the third O site, O(3) is bonded in a distorted tetrahedral geometry to two equivalent Li(2) and two equivalent Si(1) atoms.
Li6Si2O7 crystallizes in the tetragonal P-42_1m space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded in a distorted rectangular see-saw-like geometry to one O(2) and three equivalent O(1) atoms. The Li(1)-O(2) bond length is 1.98 Å. There are a spread of Li(1)-O(1) bond distances ranging from 1.93-2.04 Å. In the second Li site, Li(2) is bonded to one O(3), two equivalent O(1), and two equivalent O(2) atoms to form distorted LiO5 trigonal bipyramids that share corners with four equivalent Si(1)O4 tetrahedra,  an edgeedge with one Si(1)O4 tetrahedra, and  a faceface with one Li(2)O5 trigonal bipyramid. The Li(2)-O(3) bond length is 2.18 Å. Both Li(2)-O(1) bond lengths are 2.31 Å. Both Li(2)-O(2) bond lengths are 2.04 Å. Si(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra, corners with four equivalent Li(2)O5 trigonal bipyramids, and  an edgeedge with one Li(2)O5 trigonal bipyramid. The Si(1)-O(2) bond length is 1.64 Å. The Si(1)-O(3) bond length is 1.72 Å. Both Si(1)-O(1) bond lengths are 1.63 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to one Li(2), three equivalent Li(1), and one Si(1) atom. In the second O site, O(2) is bonded in a 5-coordinate geometry to two equivalent Li(1), two equivalent Li(2), and one Si(1) atom. In the third O site, O(3) is bonded in a distorted tetrahedral geometry to two equivalent Li(2) and two equivalent Si(1) atoms.