LiFeSi2O6 crystallizes in the orthorhombic C222_1 space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded in a 4-coordinate geometry to two equivalent O(2) and two equivalent O(4) atoms. In the second Li site, Li(2) is bonded in a 4-coordinate geometry to two equivalent O(5) and two equivalent O(6) atoms. Fe(1) is bonded to one O(1), one O(2), one O(3), and one O(6) atom to form FeO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and corners with two equivalent Si(2)O4 tetrahedra. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to two equivalent O(2) and two equivalent O(4) atoms to form SiO4 tetrahedra that share corners with two equivalent Fe(1)O4 tetrahedra and corners with two equivalent Si(2)O4 tetrahedra. In the second Si site, Si(2) is bonded to one O(1), one O(3), one O(4), and one O(5) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and corners with two equivalent Fe(1)O4 tetrahedra. In the third Si site, Si(3) is bonded to two equivalent O(5) and two equivalent O(6) atoms to form SiO4 tetrahedra that share corners with two equivalent Fe(1)O4 tetrahedra and corners with two equivalent Si(2)O4 tetrahedra. There are six inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to one Fe(1) and one Si(2) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Li(1), one Fe(1), and one Si(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Fe(1) and one Si(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Li(1), one Si(1), and one Si(2) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Li(2), one Si(2), and one Si(3) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Li(2), one Fe(1), and one Si(3) atom.
LiFeSi2O6 crystallizes in the orthorhombic C222_1 space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded in a 4-coordinate geometry to two equivalent O(2) and two equivalent O(4) atoms. Both Li(1)-O(2) bond lengths are 2.07 Å. Both Li(1)-O(4) bond lengths are 2.37 Å. In the second Li site, Li(2) is bonded in a 4-coordinate geometry to two equivalent O(5) and two equivalent O(6) atoms. Both Li(2)-O(5) bond lengths are 2.33 Å. Both Li(2)-O(6) bond lengths are 2.04 Å. Fe(1) is bonded to one O(1), one O(2), one O(3), and one O(6) atom to form FeO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and corners with two equivalent Si(2)O4 tetrahedra. The Fe(1)-O(1) bond length is 1.83 Å. The Fe(1)-O(2) bond length is 1.92 Å. The Fe(1)-O(3) bond length is 1.83 Å. The Fe(1)-O(6) bond length is 1.92 Å. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to two equivalent O(2) and two equivalent O(4) atoms to form SiO4 tetrahedra that share corners with two equivalent Fe(1)O4 tetrahedra and corners with two equivalent Si(2)O4 tetrahedra. Both Si(1)-O(2) bond lengths are 1.64 Å. Both Si(1)-O(4) bond lengths are 1.66 Å. In the second Si site, Si(2) is bonded to one O(1), one O(3), one O(4), and one O(5) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and corners with two equivalent Fe(1)O4 tetrahedra. The Si(2)-O(1) bond length is 1.60 Å. The Si(2)-O(3) bond length is 1.60 Å. The Si(2)-O(4) bond length is 1.66 Å. The Si(2)-O(5) bond length is 1.66 Å. In the third Si site, Si(3) is bonded to two equivalent O(5) and two equivalent O(6) atoms to form SiO4 tetrahedra that share corners with two equivalent Fe(1)O4 tetrahedra and corners with two equivalent Si(2)O4 tetrahedra. Both Si(3)-O(5) bond lengths are 1.66 Å. Both Si(3)-O(6) bond lengths are 1.63 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to one Fe(1) and one Si(2) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Li(1), one Fe(1), and one Si(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Fe(1) and one Si(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Li(1), one Si(1), and one Si(2) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Li(2), one Si(2), and one Si(3) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Li(2), one Fe(1), and one Si(3) atom.