LiFeSiO4 crystallizes in the monoclinic Pc space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded to one O(3), one O(5), one O(6), 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, and corners with two equivalent Si(2)O4 tetrahedra. In the second Li site, Li(2) is bonded to one O(1), one O(2), one O(4), and one O(8) atom to form distorted LiO4 tetrahedra that share corners with two equivalent Fe(1)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)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(4), one O(5), one O(6), 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 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(2), one O(3), and one O(7) atom to form FeO4 tetrahedra that share corners with two equivalent Li(1)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and  an edgeedge with one Li(2)O4 tetrahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(2), one O(4), one O(5), and one O(7) 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 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(1), one O(3), one O(6), 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 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 in a distorted trigonal planar geometry to one Li(2), one Fe(2), and one Si(2) atom. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Li(2), one Fe(2), and one Si(1) atom. In the third O site, O(3) is bonded in a trigonal planar geometry to one Li(1), one Fe(2), and one Si(2) 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 non-coplanar geometry to one Li(1), one Fe(1), and one Si(1) atom. In the sixth O site, O(6) is bonded in a trigonal planar geometry to one Li(1), one Fe(1), and one Si(2) atom. In the seventh O site, O(7) is bonded in a trigonal planar geometry to one Li(1), one Fe(2), and one Si(1) atom. In the eighth O site, O(8) is bonded in a trigonal planar geometry to one Li(2), one Fe(1), and one Si(2) atom.
LiFeSiO4 crystallizes in the monoclinic Pc space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded to one O(3), one O(5), one O(6), 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, and corners with two equivalent Si(2)O4 tetrahedra. The Li(1)-O(3) bond length is 2.06 Å. The Li(1)-O(5) bond length is 2.09 Å. The Li(1)-O(6) bond length is 2.01 Å. The Li(1)-O(7) bond length is 2.05 Å. In the second Li site, Li(2) is bonded to one O(1), one O(2), one O(4), and one O(8) atom to form distorted LiO4 tetrahedra that share corners with two equivalent Fe(1)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and  an edgeedge with one Fe(2)O4 tetrahedra. The Li(2)-O(1) bond length is 2.07 Å. The Li(2)-O(2) bond length is 2.10 Å. The Li(2)-O(4) bond length is 2.02 Å. The Li(2)-O(8) bond length is 2.06 Å. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(4), one O(5), one O(6), 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 Si(1)O4 tetrahedra, and corners with two equivalent Si(2)O4 tetrahedra. The Fe(1)-O(4) bond length is 1.90 Å. The Fe(1)-O(5) bond length is 1.90 Å. The Fe(1)-O(6) bond length is 1.91 Å. The Fe(1)-O(8) bond length is 1.90 Å. In the second Fe site, Fe(2) is bonded to one O(1), one O(2), one O(3), and one O(7) atom to form FeO4 tetrahedra that share corners with two equivalent Li(1)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and  an edgeedge with one Li(2)O4 tetrahedra. The Fe(2)-O(1) bond length is 1.91 Å. The Fe(2)-O(2) bond length is 1.90 Å. The Fe(2)-O(3) bond length is 1.90 Å. The Fe(2)-O(7) bond length is 1.91 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(2), one O(4), one O(5), and one O(7) 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 Fe(1)O4 tetrahedra, and corners with two equivalent Fe(2)O4 tetrahedra. The Si(1)-O(2) bond length is 1.64 Å. The Si(1)-O(4) bond length is 1.65 Å. The Si(1)-O(5) bond length is 1.65 Å. The Si(1)-O(7) bond length is 1.65 Å. In the second Si site, Si(2) is bonded to one O(1), one O(3), one O(6), 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 Fe(1)O4 tetrahedra, and corners with two equivalent Fe(2)O4 tetrahedra. The Si(2)-O(1) bond length is 1.65 Å. The Si(2)-O(3) bond length is 1.65 Å. The Si(2)-O(6) bond length is 1.65 Å. The Si(2)-O(8) bond length is 1.65 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Li(2), one Fe(2), and one Si(2) atom. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Li(2), one Fe(2), and one Si(1) atom. In the third O site, O(3) is bonded in a trigonal planar geometry to one Li(1), one Fe(2), and one Si(2) 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 non-coplanar geometry to one Li(1), one Fe(1), and one Si(1) atom. In the sixth O site, O(6) is bonded in a trigonal planar geometry to one Li(1), one Fe(1), and one Si(2) atom. In the seventh O site, O(7) is bonded in a trigonal planar geometry to one Li(1), one Fe(2), and one Si(1) atom. In the eighth O site, O(8) is bonded in a trigonal planar geometry to one Li(2), one Fe(1), and one Si(2) atom.