Li2Fe2Si8O19 crystallizes in the monoclinic C2 space group. Li(1) is bonded in a 3-coordinate geometry to one O(10), one O(3), and one O(7) atom. Fe(1) is bonded to one O(4), one O(7), and two equivalent O(6) atoms to form FeO4 trigonal pyramids that share  a cornercorner with one Si(4)O4 tetrahedra, corners with three equivalent Si(3)O4 tetrahedra, and corners with two equivalent Fe(1)O4 trigonal pyramids. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(5), and one O(9) atom to form corner-sharing SiO4 tetrahedra. In the second Si site, Si(2) is bonded to one O(1), one O(2), one O(3), and one O(8) atom to form corner-sharing SiO4 tetrahedra. In the third Si site, Si(3) is bonded to one O(10), one O(3), one O(4), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and corners with three equivalent Fe(1)O4 trigonal pyramids. In the fourth Si site, Si(4) is bonded to one O(5), one O(7), one O(8), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(2)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, and  a cornercorner with one Fe(1)O4 trigonal pyramid. There are ten inequivalent O sites. In the first O site, O(9) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(4) atom. In the second O site, O(10) is bonded in a distorted tetrahedral geometry to two equivalent Li(1) and two equivalent Si(3) atoms. In the third O site, O(1) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the fourth O site, O(2) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. In the fifth O site, O(3) is bonded in a distorted trigonal planar geometry to one Li(1), one Si(2), and one Si(3) atom. In the sixth O site, O(4) is bonded in a distorted water-like geometry to one Fe(1) and one Si(3) atom. In the seventh O site, O(5) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(4) atom. In the eighth O site, O(6) is bonded in a trigonal planar geometry to two equivalent Fe(1) and one Si(3) atom. In the ninth O site, O(7) is bonded in a distorted trigonal planar geometry to one Li(1), one Fe(1), and one Si(4) atom. In the tenth O site, O(8) is bonded in a linear geometry to one Si(2) and one Si(4) atom.
Li2Fe2Si8O19 crystallizes in the monoclinic C2 space group. Li(1) is bonded in a 3-coordinate geometry to one O(10), one O(3), and one O(7) atom. The Li(1)-O(10) bond length is 2.16 Å. The Li(1)-O(3) bond length is 2.07 Å. The Li(1)-O(7) bond length is 2.09 Å. Fe(1) is bonded to one O(4), one O(7), and two equivalent O(6) atoms to form FeO4 trigonal pyramids that share  a cornercorner with one Si(4)O4 tetrahedra, corners with three equivalent Si(3)O4 tetrahedra, and corners with two equivalent Fe(1)O4 trigonal pyramids. The Fe(1)-O(4) bond length is 2.01 Å. The Fe(1)-O(7) bond length is 2.01 Å. Both Fe(1)-O(6) bond lengths are 2.07 Å. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(5), and one O(9) atom to form corner-sharing SiO4 tetrahedra. The Si(1)-O(1) bond length is 1.64 Å. The Si(1)-O(2) bond length is 1.62 Å. The Si(1)-O(5) bond length is 1.63 Å. The Si(1)-O(9) bond length is 1.63 Å. In the second Si site, Si(2) is bonded to one O(1), one O(2), one O(3), and one O(8) atom to form corner-sharing SiO4 tetrahedra. The Si(2)-O(1) bond length is 1.63 Å. The Si(2)-O(2) bond length is 1.62 Å. The Si(2)-O(3) bond length is 1.64 Å. The Si(2)-O(8) bond length is 1.62 Å. In the third Si site, Si(3) is bonded to one O(10), one O(3), one O(4), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and corners with three equivalent Fe(1)O4 trigonal pyramids. The Si(3)-O(10) bond length is 1.68 Å. The Si(3)-O(3) bond length is 1.67 Å. The Si(3)-O(4) bond length is 1.60 Å. The Si(3)-O(6) bond length is 1.63 Å. In the fourth Si site, Si(4) is bonded to one O(5), one O(7), one O(8), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(2)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, and  a cornercorner with one Fe(1)O4 trigonal pyramid. The Si(4)-O(5) bond length is 1.64 Å. The Si(4)-O(7) bond length is 1.62 Å. The Si(4)-O(8) bond length is 1.66 Å. The Si(4)-O(9) bond length is 1.65 Å. There are ten inequivalent O sites. In the first O site, O(9) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(4) atom. In the second O site, O(10) is bonded in a distorted tetrahedral geometry to two equivalent Li(1) and two equivalent Si(3) atoms. In the third O site, O(1) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the fourth O site, O(2) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. In the fifth O site, O(3) is bonded in a distorted trigonal planar geometry to one Li(1), one Si(2), and one Si(3) atom. In the sixth O site, O(4) is bonded in a distorted water-like geometry to one Fe(1) and one Si(3) atom. In the seventh O site, O(5) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(4) atom. In the eighth O site, O(6) is bonded in a trigonal planar geometry to two equivalent Fe(1) and one Si(3) atom. In the ninth O site, O(7) is bonded in a distorted trigonal planar geometry to one Li(1), one Fe(1), and one Si(4) atom. In the tenth O site, O(8) is bonded in a linear geometry to one Si(2) and one Si(4) atom.