LiFeSi2O6 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(5), one O(6), and one O(9) atom to form LiO4 trigonal pyramids that share  a cornercorner with one Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra,  an edgeedge with one Fe(1)O6 octahedra, and  an edgeedge with one Fe(2)O6 octahedra. In the second Li site, Li(2) is bonded in a 4-coordinate geometry to two equivalent O(5) and two equivalent O(8) atoms. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(2), one O(4), one O(6), one O(7), and one O(8) atom to form distorted FeO6 octahedra that share  a cornercorner with one Si(3)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra,  an edgeedge with one Fe(2)O6 octahedra,  an edgeedge with one Si(3)O4 tetrahedra, and  an edgeedge with one Li(1)O4 trigonal pyramid. In the second Fe site, Fe(2) is bonded to two equivalent O(5), two equivalent O(6), and two equivalent O(7) atoms to form FeO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra, edges with two equivalent Fe(1)O6 octahedra, and edges with two equivalent Li(1)O4 trigonal pyramids. There are three 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 Fe(2)O6 octahedra, corners with two equivalent Fe(1)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and  a cornercorner with one Li(1)O4 trigonal pyramid. The corner-sharing octahedral tilt angles range from 36-50°. In the second Si site, Si(2) is bonded to one O(1), one O(3), one O(7), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Fe(2)O6 octahedra, corners with two equivalent Fe(1)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and corners with two equivalent Li(1)O4 trigonal pyramids. The corner-sharing octahedral tilt angles range from 36-57°. In the third Si site, Si(3) is bonded to one O(4), one O(6), one O(8), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Fe(1)O6 octahedra,  a cornercorner with one Fe(2)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, corners with two equivalent Li(1)O4 trigonal pyramids, and  an edgeedge with one Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 51-62°. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Li(1), one Fe(1), and one Si(2) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Fe(1) and one Si(1) atom. In the third O site, O(3) is bonded in a linear geometry to one Si(1) and one Si(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Fe(1), one Si(1), and one Si(3) atom. In the fifth O site, O(5) is bonded to one Li(1), one Li(2), one Fe(2), and one Si(1) atom to form distorted corner-sharing OLi2FeSi tetrahedra. In the sixth O site, O(6) is bonded in a distorted rectangular see-saw-like geometry to one Li(1), one Fe(1), one Fe(2), and one Si(3) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Fe(1), one Fe(2), and one Si(2) atom. In the eighth O site, O(8) is bonded in a distorted T-shaped geometry to one Li(2), one Fe(1), and one Si(3) atom. In the ninth O site, O(9) is bonded in a trigonal planar geometry to one Li(1), one Si(2), and one Si(3) atom.
LiFeSi2O6 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(5), one O(6), and one O(9) atom to form LiO4 trigonal pyramids that share  a cornercorner with one Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra,  an edgeedge with one Fe(1)O6 octahedra, and  an edgeedge with one Fe(2)O6 octahedra. The Li(1)-O(1) bond length is 2.04 Å. The Li(1)-O(5) bond length is 2.02 Å. The Li(1)-O(6) bond length is 2.16 Å. The Li(1)-O(9) bond length is 2.10 Å. In the second Li site, Li(2) is bonded in a 4-coordinate geometry to two equivalent O(5) and two equivalent O(8) atoms. Both Li(2)-O(5) bond lengths are 2.38 Å. Both Li(2)-O(8) bond lengths are 2.07 Å. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(2), one O(4), one O(6), one O(7), and one O(8) atom to form distorted FeO6 octahedra that share  a cornercorner with one Si(3)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra,  an edgeedge with one Fe(2)O6 octahedra,  an edgeedge with one Si(3)O4 tetrahedra, and  an edgeedge with one Li(1)O4 trigonal pyramid. The Fe(1)-O(1) bond length is 1.94 Å. The Fe(1)-O(2) bond length is 1.90 Å. The Fe(1)-O(4) bond length is 2.21 Å. The Fe(1)-O(6) bond length is 2.29 Å. The Fe(1)-O(7) bond length is 2.03 Å. The Fe(1)-O(8) bond length is 2.07 Å. In the second Fe site, Fe(2) is bonded to two equivalent O(5), two equivalent O(6), and two equivalent O(7) atoms to form FeO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra, edges with two equivalent Fe(1)O6 octahedra, and edges with two equivalent Li(1)O4 trigonal pyramids. Both Fe(2)-O(5) bond lengths are 2.03 Å. Both Fe(2)-O(6) bond lengths are 2.04 Å. Both Fe(2)-O(7) bond lengths are 2.07 Å. There are three 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 Fe(2)O6 octahedra, corners with two equivalent Fe(1)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and  a cornercorner with one Li(1)O4 trigonal pyramid. The corner-sharing octahedral tilt angles range from 36-50°. The Si(1)-O(2) bond length is 1.61 Å. The Si(1)-O(3) bond length is 1.63 Å. The Si(1)-O(4) bond length is 1.68 Å. The Si(1)-O(5) bond length is 1.63 Å. In the second Si site, Si(2) is bonded to one O(1), one O(3), one O(7), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Fe(2)O6 octahedra, corners with two equivalent Fe(1)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and corners with two equivalent Li(1)O4 trigonal pyramids. The corner-sharing octahedral tilt angles range from 36-57°. The Si(2)-O(1) bond length is 1.61 Å. The Si(2)-O(3) bond length is 1.61 Å. The Si(2)-O(7) bond length is 1.65 Å. The Si(2)-O(9) bond length is 1.68 Å. In the third Si site, Si(3) is bonded to one O(4), one O(6), one O(8), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Fe(1)O6 octahedra,  a cornercorner with one Fe(2)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, corners with two equivalent Li(1)O4 trigonal pyramids, and  an edgeedge with one Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 51-62°. The Si(3)-O(4) bond length is 1.68 Å. The Si(3)-O(6) bond length is 1.64 Å. The Si(3)-O(8) bond length is 1.61 Å. The Si(3)-O(9) bond length is 1.67 Å. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Li(1), one Fe(1), and one Si(2) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Fe(1) and one Si(1) atom. In the third O site, O(3) is bonded in a linear geometry to one Si(1) and one Si(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Fe(1), one Si(1), and one Si(3) atom. In the fifth O site, O(5) is bonded to one Li(1), one Li(2), one Fe(2), and one Si(1) atom to form distorted corner-sharing OLi2FeSi tetrahedra. In the sixth O site, O(6) is bonded in a distorted rectangular see-saw-like geometry to one Li(1), one Fe(1), one Fe(2), and one Si(3) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Fe(1), one Fe(2), and one Si(2) atom. In the eighth O site, O(8) is bonded in a distorted T-shaped geometry to one Li(2), one Fe(1), and one Si(3) atom. In the ninth O site, O(9) is bonded in a trigonal planar geometry to one Li(1), one Si(2), and one Si(3) atom.