Li2FeSiO5 crystallizes in the tetragonal P4mm space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded to one O(1), one O(4), two equivalent O(5), and two equivalent O(8) atoms to form distorted LiO6 octahedra that share corners with two equivalent Li(1)O6 octahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, edges with four equivalent Li(1)O6 octahedra,  a faceface with one Fe(1)O6 octahedra, and  a faceface with one Fe(4)O6 octahedra. The corner-sharing octahedral tilt angles are 32°. In the second Li site, Li(2) is bonded to one O(2), one O(3), two equivalent O(6), and two equivalent O(7) atoms to form distorted LiO6 octahedra that share  a cornercorner with one Fe(1)O6 octahedra,  a cornercorner with one Fe(4)O6 octahedra, corners with two equivalent Li(2)O6 octahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with four equivalent Li(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-63°. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(2), and four equivalent O(8) atoms to form distorted FeO6 octahedra that share corners with four equivalent Li(2)O6 octahedra, corners with four equivalent Si(2)O4 tetrahedra, and faces with four equivalent Li(1)O6 octahedra. The corner-sharing octahedral tilt angles are 63°. In the second Fe site, Fe(2) is bonded in a 5-coordinate geometry to one O(4) and four equivalent O(6) atoms. In the third Fe site, Fe(3) is bonded in a 5-coordinate geometry to one O(1) and four equivalent O(7) atoms. In the fourth Fe site, Fe(4) is bonded to one O(3), one O(4), and four equivalent O(5) atoms to form distorted FeO6 octahedra that share corners with four equivalent Li(2)O6 octahedra, corners with four equivalent Si(1)O4 tetrahedra, and faces with four equivalent Li(1)O6 octahedra. The corner-sharing octahedral tilt angles are 63°. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to two equivalent O(5) and two equivalent O(7) atoms to form SiO4 tetrahedra that share corners with two equivalent Fe(4)O6 octahedra, corners with four equivalent Li(1)O6 octahedra, and corners with four equivalent Li(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-63°. In the second Si site, Si(2) is bonded to two equivalent O(6) and two equivalent O(8) atoms to form SiO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with four equivalent Li(1)O6 octahedra, and corners with four equivalent Li(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-63°. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to four equivalent Li(1), one Fe(1), and one Fe(3) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to four equivalent Li(2) and one Fe(1) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to four equivalent Li(2) and one Fe(4) atom. In the fourth O site, O(4) is bonded in a 6-coordinate geometry to four equivalent Li(1), one Fe(2), and one Fe(4) atom. In the fifth O site, O(5) is bonded to two equivalent Li(1), one Fe(4), and one Si(1) atom to form a mixture of distorted corner and edge-sharing OLi2FeSi trigonal pyramids. In the sixth O site, O(6) is bonded to two equivalent Li(2), one Fe(2), and one Si(2) atom to form a mixture of distorted corner and edge-sharing OLi2FeSi tetrahedra. In the seventh O site, O(7) is bonded to two equivalent Li(2), one Fe(3), and one Si(1) atom to form a mixture of distorted corner and edge-sharing OLi2FeSi trigonal pyramids. In the eighth O site, O(8) is bonded to two equivalent Li(1), one Fe(1), and one Si(2) atom to form a mixture of distorted corner and edge-sharing OLi2FeSi trigonal pyramids.
Li2FeSiO5 crystallizes in the tetragonal P4mm space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded to one O(1), one O(4), two equivalent O(5), and two equivalent O(8) atoms to form distorted LiO6 octahedra that share corners with two equivalent Li(1)O6 octahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, edges with four equivalent Li(1)O6 octahedra,  a faceface with one Fe(1)O6 octahedra, and  a faceface with one Fe(4)O6 octahedra. The corner-sharing octahedral tilt angles are 32°. The Li(1)-O(1) bond length is 2.36 Å. The Li(1)-O(4) bond length is 2.39 Å. Both Li(1)-O(5) bond lengths are 2.06 Å. Both Li(1)-O(8) bond lengths are 2.06 Å. In the second Li site, Li(2) is bonded to one O(2), one O(3), two equivalent O(6), and two equivalent O(7) atoms to form distorted LiO6 octahedra that share  a cornercorner with one Fe(1)O6 octahedra,  a cornercorner with one Fe(4)O6 octahedra, corners with two equivalent Li(2)O6 octahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with four equivalent Li(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-63°. The Li(2)-O(2) bond length is 2.56 Å. The Li(2)-O(3) bond length is 2.58 Å. Both Li(2)-O(6) bond lengths are 2.05 Å. Both Li(2)-O(7) bond lengths are 2.05 Å. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(2), and four equivalent O(8) atoms to form distorted FeO6 octahedra that share corners with four equivalent Li(2)O6 octahedra, corners with four equivalent Si(2)O4 tetrahedra, and faces with four equivalent Li(1)O6 octahedra. The corner-sharing octahedral tilt angles are 63°. The Fe(1)-O(1) bond length is 2.18 Å. The Fe(1)-O(2) bond length is 1.73 Å. All Fe(1)-O(8) bond lengths are 1.97 Å. In the second Fe site, Fe(2) is bonded in a 5-coordinate geometry to one O(4) and four equivalent O(6) atoms. The Fe(2)-O(4) bond length is 1.85 Å. All Fe(2)-O(6) bond lengths are 2.02 Å. In the third Fe site, Fe(3) is bonded in a 5-coordinate geometry to one O(1) and four equivalent O(7) atoms. The Fe(3)-O(1) bond length is 1.85 Å. All Fe(3)-O(7) bond lengths are 2.02 Å. In the fourth Fe site, Fe(4) is bonded to one O(3), one O(4), and four equivalent O(5) atoms to form distorted FeO6 octahedra that share corners with four equivalent Li(2)O6 octahedra, corners with four equivalent Si(1)O4 tetrahedra, and faces with four equivalent Li(1)O6 octahedra. The corner-sharing octahedral tilt angles are 63°. The Fe(4)-O(3) bond length is 1.73 Å. The Fe(4)-O(4) bond length is 2.18 Å. All Fe(4)-O(5) bond lengths are 1.96 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to two equivalent O(5) and two equivalent O(7) atoms to form SiO4 tetrahedra that share corners with two equivalent Fe(4)O6 octahedra, corners with four equivalent Li(1)O6 octahedra, and corners with four equivalent Li(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-63°. Both Si(1)-O(5) bond lengths are 1.65 Å. Both Si(1)-O(7) bond lengths are 1.64 Å. In the second Si site, Si(2) is bonded to two equivalent O(6) and two equivalent O(8) atoms to form SiO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with four equivalent Li(1)O6 octahedra, and corners with four equivalent Li(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-63°. Both Si(2)-O(6) bond lengths are 1.64 Å. Both Si(2)-O(8) bond lengths are 1.65 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to four equivalent Li(1), one Fe(1), and one Fe(3) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to four equivalent Li(2) and one Fe(1) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to four equivalent Li(2) and one Fe(4) atom. In the fourth O site, O(4) is bonded in a 6-coordinate geometry to four equivalent Li(1), one Fe(2), and one Fe(4) atom. In the fifth O site, O(5) is bonded to two equivalent Li(1), one Fe(4), and one Si(1) atom to form a mixture of distorted corner and edge-sharing OLi2FeSi trigonal pyramids. In the sixth O site, O(6) is bonded to two equivalent Li(2), one Fe(2), and one Si(2) atom to form a mixture of distorted corner and edge-sharing OLi2FeSi tetrahedra. In the seventh O site, O(7) is bonded to two equivalent Li(2), one Fe(3), and one Si(1) atom to form a mixture of distorted corner and edge-sharing OLi2FeSi trigonal pyramids. In the eighth O site, O(8) is bonded to two equivalent Li(1), one Fe(1), and one Si(2) atom to form a mixture of distorted corner and edge-sharing OLi2FeSi trigonal pyramids.