Li2Fe5(Si2O7)2 crystallizes in the triclinic P-1 space group. Li(1) is bonded to one O(3), one O(4), one O(5), and two equivalent O(1) atoms to form distorted LiO5 trigonal bipyramids that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, corners with two equivalent Fe(3)O5 trigonal bipyramids,  an edgeedge with one Si(2)O4 tetrahedra, and  an edgeedge with one Li(1)O5 trigonal bipyramid. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a rectangular see-saw-like geometry to one O(1), one O(4), and two equivalent O(2) atoms. In the second Fe site, Fe(2) is bonded in a square co-planar geometry to two equivalent O(5) and two equivalent O(7) atoms. In the third Fe site, Fe(3) is bonded to one O(4), one O(5), one O(7), and two equivalent O(6) atoms to form distorted FeO5 trigonal bipyramids that share corners with two equivalent Si(1)O4 tetrahedra, corners with three equivalent Si(2)O4 tetrahedra, corners with two equivalent Li(1)O5 trigonal bipyramids, and  an edgeedge with one Fe(3)O5 trigonal bipyramid. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(2), one O(3), one O(4), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(2)O4 tetrahedra, corners with two equivalent Li(1)O5 trigonal bipyramids, and corners with two equivalent Fe(3)O5 trigonal bipyramids. In the second Si site, Si(2) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra, corners with two equivalent Li(1)O5 trigonal bipyramids, corners with three equivalent Fe(3)O5 trigonal bipyramids, and  an edgeedge with one Li(1)O5 trigonal bipyramid. There are seven inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Li(1), one Fe(1), and one Si(2) atom to form OLi2FeSi trigonal pyramids that share  a cornercorner with one O(4)LiFe2Si tetrahedra,  a cornercorner with one O(5)LiFe2Si trigonal pyramid,  an edgeedge with one O(4)LiFe2Si tetrahedra,  an edgeedge with one O(1)Li2FeSi trigonal pyramid, and  an edgeedge with one O(5)LiFe2Si trigonal pyramid. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to two equivalent Fe(1) and one Si(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Li(1), one Si(1), and one Si(2) atom. In the fourth O site, O(4) is bonded to one Li(1), one Fe(1), one Fe(3), and one Si(1) atom to form distorted OLiFe2Si tetrahedra that share  a cornercorner with one O(1)Li2FeSi trigonal pyramid, corners with two equivalent O(5)LiFe2Si trigonal pyramids, and  an edgeedge with one O(1)Li2FeSi trigonal pyramid. In the fifth O site, O(5) is bonded to one Li(1), one Fe(2), one Fe(3), and one Si(2) atom to form distorted OLiFe2Si trigonal pyramids that share corners with two equivalent O(4)LiFe2Si tetrahedra,  a cornercorner with one O(1)Li2FeSi trigonal pyramid,  a cornercorner with one O(5)LiFe2Si trigonal pyramid, and  an edgeedge with one O(1)Li2FeSi trigonal pyramid. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to two equivalent Fe(3) and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Fe(2), one Fe(3), and one Si(1) atom.
Li2Fe5(Si2O7)2 crystallizes in the triclinic P-1 space group. Li(1) is bonded to one O(3), one O(4), one O(5), and two equivalent O(1) atoms to form distorted LiO5 trigonal bipyramids that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, corners with two equivalent Fe(3)O5 trigonal bipyramids,  an edgeedge with one Si(2)O4 tetrahedra, and  an edgeedge with one Li(1)O5 trigonal bipyramid. The Li(1)-O(3) bond length is 2.25 Å. The Li(1)-O(4) bond length is 2.20 Å. The Li(1)-O(5) bond length is 2.27 Å. There is one shorter (1.99 Å) and one longer (2.26 Å) Li(1)-O(1) bond length. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a rectangular see-saw-like geometry to one O(1), one O(4), and two equivalent O(2) atoms. The Fe(1)-O(1) bond length is 1.98 Å. The Fe(1)-O(4) bond length is 2.06 Å. There is one shorter (2.05 Å) and one longer (2.06 Å) Fe(1)-O(2) bond length. In the second Fe site, Fe(2) is bonded in a square co-planar geometry to two equivalent O(5) and two equivalent O(7) atoms. Both Fe(2)-O(5) bond lengths are 2.02 Å. Both Fe(2)-O(7) bond lengths are 2.07 Å. In the third Fe site, Fe(3) is bonded to one O(4), one O(5), one O(7), and two equivalent O(6) atoms to form distorted FeO5 trigonal bipyramids that share corners with two equivalent Si(1)O4 tetrahedra, corners with three equivalent Si(2)O4 tetrahedra, corners with two equivalent Li(1)O5 trigonal bipyramids, and  an edgeedge with one Fe(3)O5 trigonal bipyramid. The Fe(3)-O(4) bond length is 2.16 Å. The Fe(3)-O(5) bond length is 2.17 Å. The Fe(3)-O(7) bond length is 2.07 Å. There is one shorter (2.08 Å) and one longer (2.17 Å) Fe(3)-O(6) bond length. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(2), one O(3), one O(4), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(2)O4 tetrahedra, corners with two equivalent Li(1)O5 trigonal bipyramids, and corners with two equivalent Fe(3)O5 trigonal bipyramids. The Si(1)-O(2) bond length is 1.64 Å. The Si(1)-O(3) bond length is 1.67 Å. The Si(1)-O(4) bond length is 1.66 Å. The Si(1)-O(7) bond length is 1.64 Å. In the second Si site, Si(2) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra, corners with two equivalent Li(1)O5 trigonal bipyramids, corners with three equivalent Fe(3)O5 trigonal bipyramids, and  an edgeedge with one Li(1)O5 trigonal bipyramid. The Si(2)-O(1) bond length is 1.64 Å. The Si(2)-O(3) bond length is 1.68 Å. The Si(2)-O(5) bond length is 1.65 Å. The Si(2)-O(6) bond length is 1.63 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Li(1), one Fe(1), and one Si(2) atom to form OLi2FeSi trigonal pyramids that share  a cornercorner with one O(4)LiFe2Si tetrahedra,  a cornercorner with one O(5)LiFe2Si trigonal pyramid,  an edgeedge with one O(4)LiFe2Si tetrahedra,  an edgeedge with one O(1)Li2FeSi trigonal pyramid, and  an edgeedge with one O(5)LiFe2Si trigonal pyramid. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to two equivalent Fe(1) and one Si(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Li(1), one Si(1), and one Si(2) atom. In the fourth O site, O(4) is bonded to one Li(1), one Fe(1), one Fe(3), and one Si(1) atom to form distorted OLiFe2Si tetrahedra that share  a cornercorner with one O(1)Li2FeSi trigonal pyramid, corners with two equivalent O(5)LiFe2Si trigonal pyramids, and  an edgeedge with one O(1)Li2FeSi trigonal pyramid. In the fifth O site, O(5) is bonded to one Li(1), one Fe(2), one Fe(3), and one Si(2) atom to form distorted OLiFe2Si trigonal pyramids that share corners with two equivalent O(4)LiFe2Si tetrahedra,  a cornercorner with one O(1)Li2FeSi trigonal pyramid,  a cornercorner with one O(5)LiFe2Si trigonal pyramid, and  an edgeedge with one O(1)Li2FeSi trigonal pyramid. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to two equivalent Fe(3) and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Fe(2), one Fe(3), and one Si(1) atom.