Li4Fe2Si3O10 crystallizes in the monoclinic C2/c space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded to one O(3), one O(5), and two equivalent O(2) atoms to form LiO4 tetrahedra that share corners with four equivalent Si(1)O4 tetrahedra, corners with three equivalent Fe(1)O5 trigonal bipyramids,  an edgeedge with one Li(1)O4 tetrahedra, and  an edgeedge with one Fe(1)O5 trigonal bipyramid. In the second Li site, Li(2) is bonded in a 5-coordinate geometry to one O(3), two equivalent O(1), and two equivalent O(4) atoms. Fe(1) is bonded to one O(1), one O(2), one O(3), and two equivalent O(5) atoms to form FeO5 trigonal bipyramids that share  a cornercorner with one Si(2)O4 tetrahedra, corners with three equivalent Li(1)O4 tetrahedra, corners with four equivalent Si(1)O4 tetrahedra,  an edgeedge with one Li(1)O4 tetrahedra, and  an edgeedge with one Fe(1)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(5) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(2)O4 tetrahedra, corners with four equivalent Li(1)O4 tetrahedra, and corners with four equivalent Fe(1)O5 trigonal bipyramids. In the second Si site, Si(2) is bonded to two equivalent O(1) and two equivalent O(4) atoms to form SiO4 tetrahedra that share corners with two equivalent Si(1)O4 tetrahedra and corners with two equivalent Fe(1)O5 trigonal bipyramids. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Li(2), one Fe(1), and one Si(2) atom to form distorted OLi2FeSi trigonal pyramids that share  a cornercorner with one O(3)Li2FeSi tetrahedra, corners with two equivalent O(5)LiFe2Si tetrahedra, corners with three equivalent O(1)Li2FeSi trigonal pyramids, and  an edgeedge with one O(3)Li2FeSi tetrahedra. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Li(1), one Fe(1), and one Si(1) atom. In the third O site, O(3) is bonded to one Li(1), one Li(2), one Fe(1), and one Si(1) atom to form distorted OLi2FeSi tetrahedra that share corners with four equivalent O(5)LiFe2Si tetrahedra,  a cornercorner with one O(1)Li2FeSi trigonal pyramid, and  an edgeedge with one O(1)Li2FeSi trigonal pyramid. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to two equivalent Li(2), one Si(1), and one Si(2) atom. In the fifth O site, O(5) is bonded to one Li(1), two equivalent Fe(1), and one Si(1) atom to form distorted OLiFe2Si tetrahedra that share corners with four equivalent O(3)Li2FeSi tetrahedra, corners with two equivalent O(1)Li2FeSi trigonal pyramids, and  an edgeedge with one O(5)LiFe2Si tetrahedra.
Li4Fe2Si3O10 crystallizes in the monoclinic C2/c space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded to one O(3), one O(5), and two equivalent O(2) atoms to form LiO4 tetrahedra that share corners with four equivalent Si(1)O4 tetrahedra, corners with three equivalent Fe(1)O5 trigonal bipyramids,  an edgeedge with one Li(1)O4 tetrahedra, and  an edgeedge with one Fe(1)O5 trigonal bipyramid. The Li(1)-O(3) bond length is 2.00 Å. The Li(1)-O(5) bond length is 2.04 Å. There is one shorter (1.92 Å) and one longer (2.00 Å) Li(1)-O(2) bond length. In the second Li site, Li(2) is bonded in a 5-coordinate geometry to one O(3), two equivalent O(1), and two equivalent O(4) atoms. The Li(2)-O(3) bond length is 2.11 Å. There is one shorter (2.00 Å) and one longer (2.06 Å) Li(2)-O(1) bond length. There is one shorter (2.40 Å) and one longer (2.51 Å) Li(2)-O(4) bond length. Fe(1) is bonded to one O(1), one O(2), one O(3), and two equivalent O(5) atoms to form FeO5 trigonal bipyramids that share  a cornercorner with one Si(2)O4 tetrahedra, corners with three equivalent Li(1)O4 tetrahedra, corners with four equivalent Si(1)O4 tetrahedra,  an edgeedge with one Li(1)O4 tetrahedra, and  an edgeedge with one Fe(1)O5 trigonal bipyramid. The Fe(1)-O(1) bond length is 2.22 Å. The Fe(1)-O(2) bond length is 2.10 Å. The Fe(1)-O(3) bond length is 2.05 Å. There is one shorter (2.08 Å) and one longer (2.25 Å) Fe(1)-O(5) 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(5) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(2)O4 tetrahedra, corners with four equivalent Li(1)O4 tetrahedra, and corners with four equivalent Fe(1)O5 trigonal bipyramids. The Si(1)-O(2) bond length is 1.63 Å. The Si(1)-O(3) bond length is 1.64 Å. The Si(1)-O(4) bond length is 1.68 Å. The Si(1)-O(5) bond length is 1.64 Å. In the second Si site, Si(2) is bonded to two equivalent O(1) and two equivalent O(4) atoms to form SiO4 tetrahedra that share corners with two equivalent Si(1)O4 tetrahedra and corners with two equivalent Fe(1)O5 trigonal bipyramids. Both Si(2)-O(1) bond lengths are 1.62 Å. Both Si(2)-O(4) bond lengths are 1.67 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Li(2), one Fe(1), and one Si(2) atom to form distorted OLi2FeSi trigonal pyramids that share  a cornercorner with one O(3)Li2FeSi tetrahedra, corners with two equivalent O(5)LiFe2Si tetrahedra, corners with three equivalent O(1)Li2FeSi trigonal pyramids, and  an edgeedge with one O(3)Li2FeSi tetrahedra. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Li(1), one Fe(1), and one Si(1) atom. In the third O site, O(3) is bonded to one Li(1), one Li(2), one Fe(1), and one Si(1) atom to form distorted OLi2FeSi tetrahedra that share corners with four equivalent O(5)LiFe2Si tetrahedra,  a cornercorner with one O(1)Li2FeSi trigonal pyramid, and  an edgeedge with one O(1)Li2FeSi trigonal pyramid. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to two equivalent Li(2), one Si(1), and one Si(2) atom. In the fifth O site, O(5) is bonded to one Li(1), two equivalent Fe(1), and one Si(1) atom to form distorted OLiFe2Si tetrahedra that share corners with four equivalent O(3)Li2FeSi tetrahedra, corners with two equivalent O(1)Li2FeSi trigonal pyramids, and  an edgeedge with one O(5)LiFe2Si tetrahedra.