Li3Fe2(SiO4)2 crystallizes in the monoclinic P2_1 space group. There are three inequivalent Li sites. In the first Li site, Li(1) is bonded to one O(2), one O(3), one O(5), and one O(7) atom to form LiO4 tetrahedra that share corners with two equivalent Fe(1)O4 tetrahedra, corners with two equivalent Fe(2)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and  an edgeedge with one Li(3)O4 tetrahedra. In the second Li site, Li(2) is bonded to one O(1), one O(4), one O(6), and one O(8) atom to form LiO4 tetrahedra that share corners with two equivalent Li(3)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra, corners with two equivalent Fe(2)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, and corners with two equivalent Si(2)O4 tetrahedra. In the third Li site, Li(3) is bonded to one O(1), one O(2), one O(7), and one O(8) atom to form distorted LiO4 tetrahedra that share corners with two equivalent Li(2)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra,  an edgeedge with one Li(1)O4 tetrahedra, and  an edgeedge with one Fe(2)O4 tetrahedra. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(2), one O(4), one O(5), and one O(8) atom to form FeO4 tetrahedra that share corners with two equivalent Li(1)O4 tetrahedra, corners with two equivalent Li(2)O4 tetrahedra, corners with two equivalent Li(3)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, and corners with two equivalent Si(2)O4 tetrahedra. In the second Fe site, Fe(2) is bonded to one O(1), one O(3), one O(6), and one O(7) atom to form FeO4 tetrahedra that share corners with two equivalent Li(1)O4 tetrahedra, corners with two equivalent Li(2)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and  an edgeedge with one Li(3)O4 tetrahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share corners with two equivalent Li(1)O4 tetrahedra, corners with two equivalent Li(2)O4 tetrahedra, corners with two equivalent Li(3)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra, and corners with two equivalent Fe(2)O4 tetrahedra. In the second Si site, Si(2) is bonded to one O(5), one O(6), one O(7), and one O(8) atom to form SiO4 tetrahedra that share corners with two equivalent Li(1)O4 tetrahedra, corners with two equivalent Li(2)O4 tetrahedra, corners with two equivalent Li(3)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra, and corners with two equivalent Fe(2)O4 tetrahedra. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Li(2), one Li(3), one Fe(2), and one Si(1) atom to form a mixture of corner and edge-sharing OLi2FeSi tetrahedra. In the second O site, O(2) is bonded to one Li(1), one Li(3), one Fe(1), and one Si(1) atom to form a mixture of corner and edge-sharing OLi2FeSi tetrahedra. In the third O site, O(3) is bonded in a trigonal planar geometry to one Li(1), one Fe(2), and one Si(1) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Li(2), one Fe(1), and one Si(1) atom. In the fifth O site, O(5) is bonded in a trigonal planar geometry to one Li(1), one Fe(1), and one Si(2) atom. In the sixth O site, O(6) is bonded in a trigonal planar geometry to one Li(2), one Fe(2), and one Si(2) atom. In the seventh O site, O(7) is bonded to one Li(1), one Li(3), one Fe(2), and one Si(2) atom to form a mixture of distorted corner and edge-sharing OLi2FeSi trigonal pyramids. In the eighth O site, O(8) is bonded to one Li(2), one Li(3), one Fe(1), and one Si(2) atom to form corner-sharing OLi2FeSi tetrahedra.
Li3Fe2(SiO4)2 crystallizes in the monoclinic P2_1 space group. There are three inequivalent Li sites. In the first Li site, Li(1) is bonded to one O(2), one O(3), one O(5), and one O(7) atom to form LiO4 tetrahedra that share corners with two equivalent Fe(1)O4 tetrahedra, corners with two equivalent Fe(2)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and  an edgeedge with one Li(3)O4 tetrahedra. The Li(1)-O(2) bond length is 1.99 Å. The Li(1)-O(3) bond length is 2.00 Å. The Li(1)-O(5) bond length is 1.93 Å. The Li(1)-O(7) bond length is 2.12 Å. In the second Li site, Li(2) is bonded to one O(1), one O(4), one O(6), and one O(8) atom to form LiO4 tetrahedra that share corners with two equivalent Li(3)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra, corners with two equivalent Fe(2)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, and corners with two equivalent Si(2)O4 tetrahedra. The Li(2)-O(1) bond length is 2.12 Å. The Li(2)-O(4) bond length is 1.91 Å. The Li(2)-O(6) bond length is 2.02 Å. The Li(2)-O(8) bond length is 2.02 Å. In the third Li site, Li(3) is bonded to one O(1), one O(2), one O(7), and one O(8) atom to form distorted LiO4 tetrahedra that share corners with two equivalent Li(2)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra,  an edgeedge with one Li(1)O4 tetrahedra, and  an edgeedge with one Fe(2)O4 tetrahedra. The Li(3)-O(1) bond length is 2.26 Å. The Li(3)-O(2) bond length is 1.99 Å. The Li(3)-O(7) bond length is 2.13 Å. The Li(3)-O(8) bond length is 1.93 Å. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(2), one O(4), one O(5), and one O(8) atom to form FeO4 tetrahedra that share corners with two equivalent Li(1)O4 tetrahedra, corners with two equivalent Li(2)O4 tetrahedra, corners with two equivalent Li(3)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, and corners with two equivalent Si(2)O4 tetrahedra. The Fe(1)-O(2) bond length is 2.08 Å. The Fe(1)-O(4) bond length is 1.96 Å. The Fe(1)-O(5) bond length is 1.99 Å. The Fe(1)-O(8) bond length is 2.13 Å. In the second Fe site, Fe(2) is bonded to one O(1), one O(3), one O(6), and one O(7) atom to form FeO4 tetrahedra that share corners with two equivalent Li(1)O4 tetrahedra, corners with two equivalent Li(2)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and  an edgeedge with one Li(3)O4 tetrahedra. The Fe(2)-O(1) bond length is 1.93 Å. The Fe(2)-O(3) bond length is 1.87 Å. The Fe(2)-O(6) bond length is 1.89 Å. The Fe(2)-O(7) bond length is 1.96 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share corners with two equivalent Li(1)O4 tetrahedra, corners with two equivalent Li(2)O4 tetrahedra, corners with two equivalent Li(3)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra, and corners with two equivalent Fe(2)O4 tetrahedra. The Si(1)-O(1) bond length is 1.70 Å. The Si(1)-O(2) bond length is 1.64 Å. The Si(1)-O(3) bond length is 1.66 Å. The Si(1)-O(4) bond length is 1.61 Å. In the second Si site, Si(2) is bonded to one O(5), one O(6), one O(7), and one O(8) atom to form SiO4 tetrahedra that share corners with two equivalent Li(1)O4 tetrahedra, corners with two equivalent Li(2)O4 tetrahedra, corners with two equivalent Li(3)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra, and corners with two equivalent Fe(2)O4 tetrahedra. The Si(2)-O(5) bond length is 1.62 Å. The Si(2)-O(6) bond length is 1.67 Å. The Si(2)-O(7) bond length is 1.69 Å. The Si(2)-O(8) bond length is 1.64 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Li(2), one Li(3), one Fe(2), and one Si(1) atom to form a mixture of corner and edge-sharing OLi2FeSi tetrahedra. In the second O site, O(2) is bonded to one Li(1), one Li(3), one Fe(1), and one Si(1) atom to form a mixture of corner and edge-sharing OLi2FeSi tetrahedra. In the third O site, O(3) is bonded in a trigonal planar geometry to one Li(1), one Fe(2), and one Si(1) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Li(2), one Fe(1), and one Si(1) atom. In the fifth O site, O(5) is bonded in a trigonal planar geometry to one Li(1), one Fe(1), and one Si(2) atom. In the sixth O site, O(6) is bonded in a trigonal planar geometry to one Li(2), one Fe(2), and one Si(2) atom. In the seventh O site, O(7) is bonded to one Li(1), one Li(3), one Fe(2), and one Si(2) atom to form a mixture of distorted corner and edge-sharing OLi2FeSi trigonal pyramids. In the eighth O site, O(8) is bonded to one Li(2), one Li(3), one Fe(1), and one Si(2) atom to form corner-sharing OLi2FeSi tetrahedra.