Li2W2O7 crystallizes in the triclinic P-1 space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded to one O(1), one O(2), one O(4), and one O(7) atom to form distorted LiO4 trigonal pyramids that share  a cornercorner with one Li(2)O6 octahedra, corners with two equivalent W(1)O6 octahedra, and  an edgeedge with one Li(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 21-82°. In the second Li site, Li(2) is bonded to one O(2), one O(3), one O(4), one O(7), and two equivalent O(6) atoms to form distorted LiO6 octahedra that share corners with two equivalent W(1)O6 octahedra,  a cornercorner with one Li(1)O4 trigonal pyramid,  an edgeedge with one Li(2)O6 octahedra,  an edgeedge with one W(1)O6 octahedra, and  an edgeedge with one Li(1)O4 trigonal pyramid. The corner-sharing octahedral tilt angles range from 23-27°. There are two inequivalent W sites. In the first W site, W(1) is bonded to one O(1), one O(3), one O(6), one O(7), and two equivalent O(5) atoms to form distorted WO6 octahedra that share corners with two equivalent Li(2)O6 octahedra, corners with two equivalent Li(1)O4 trigonal pyramids,  an edgeedge with one Li(2)O6 octahedra, and  an edgeedge with one W(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 23-27°. In the second W site, W(2) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to one Li(1), one W(1), and one W(2) atom. In the second O site, O(2) is bonded in a T-shaped geometry to one Li(1), one Li(2), and one W(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Li(2), one W(1), and one W(2) atom. In the fourth O site, O(4) is bonded in a T-shaped geometry to one Li(1), one Li(2), and one W(2) atom. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one W(2) and two equivalent W(1) atoms. In the sixth O site, O(6) is bonded to two equivalent Li(2), one W(1), and one W(2) atom to form edge-sharing OLi2W2 trigonal pyramids. In the seventh O site, O(7) is bonded in a trigonal non-coplanar geometry to one Li(1), one Li(2), and one W(1) atom.
Li2W2O7 crystallizes in the triclinic P-1 space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded to one O(1), one O(2), one O(4), and one O(7) atom to form distorted LiO4 trigonal pyramids that share  a cornercorner with one Li(2)O6 octahedra, corners with two equivalent W(1)O6 octahedra, and  an edgeedge with one Li(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 21-82°. The Li(1)-O(1) bond length is 2.02 Å. The Li(1)-O(2) bond length is 2.14 Å. The Li(1)-O(4) bond length is 1.95 Å. The Li(1)-O(7) bond length is 1.95 Å. In the second Li site, Li(2) is bonded to one O(2), one O(3), one O(4), one O(7), and two equivalent O(6) atoms to form distorted LiO6 octahedra that share corners with two equivalent W(1)O6 octahedra,  a cornercorner with one Li(1)O4 trigonal pyramid,  an edgeedge with one Li(2)O6 octahedra,  an edgeedge with one W(1)O6 octahedra, and  an edgeedge with one Li(1)O4 trigonal pyramid. The corner-sharing octahedral tilt angles range from 23-27°. The Li(2)-O(2) bond length is 1.99 Å. The Li(2)-O(3) bond length is 2.25 Å. The Li(2)-O(4) bond length is 2.19 Å. The Li(2)-O(7) bond length is 2.22 Å. There is one shorter (2.24 Å) and one longer (2.44 Å) Li(2)-O(6) bond length. There are two inequivalent W sites. In the first W site, W(1) is bonded to one O(1), one O(3), one O(6), one O(7), and two equivalent O(5) atoms to form distorted WO6 octahedra that share corners with two equivalent Li(2)O6 octahedra, corners with two equivalent Li(1)O4 trigonal pyramids,  an edgeedge with one Li(2)O6 octahedra, and  an edgeedge with one W(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 23-27°. The W(1)-O(1) bond length is 2.13 Å. The W(1)-O(3) bond length is 1.87 Å. The W(1)-O(6) bond length is 1.95 Å. The W(1)-O(7) bond length is 1.79 Å. There is one shorter (1.98 Å) and one longer (2.14 Å) W(1)-O(5) bond length. In the second W site, W(2) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom. The W(2)-O(1) bond length is 1.90 Å. The W(2)-O(2) bond length is 1.80 Å. The W(2)-O(3) bond length is 2.26 Å. The W(2)-O(4) bond length is 1.79 Å. The W(2)-O(5) bond length is 2.19 Å. The W(2)-O(6) bond length is 2.04 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to one Li(1), one W(1), and one W(2) atom. In the second O site, O(2) is bonded in a T-shaped geometry to one Li(1), one Li(2), and one W(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Li(2), one W(1), and one W(2) atom. In the fourth O site, O(4) is bonded in a T-shaped geometry to one Li(1), one Li(2), and one W(2) atom. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one W(2) and two equivalent W(1) atoms. In the sixth O site, O(6) is bonded to two equivalent Li(2), one W(1), and one W(2) atom to form edge-sharing OLi2W2 trigonal pyramids. In the seventh O site, O(7) is bonded in a trigonal non-coplanar geometry to one Li(1), one Li(2), and one W(1) atom.