Li2FeSiO4 is beta beryllia-derived structured and crystallizes in the monoclinic P2_1 space group. There are four inequivalent Li sites. In the first Li site, Li(1) is bonded to one O(2), one O(7), and two equivalent O(3) atoms to form LiO4 tetrahedra that share  a cornercorner with one Li(3)O4 tetrahedra,  a cornercorner with one Li(4)O4 tetrahedra,  a cornercorner with one Fe(1)O4 tetrahedra,  a cornercorner with one Fe(2)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra, corners with two equivalent Li(1)O4 tetrahedra, corners with three equivalent Si(2)O4 tetrahedra, and  an edgeedge with one Fe(1)O4 tetrahedra. In the second Li site, Li(2) is bonded to one O(1), one O(8), and two equivalent O(4) atoms to form LiO4 tetrahedra that share  a cornercorner with one Li(3)O4 tetrahedra,  a cornercorner with one Li(4)O4 tetrahedra,  a cornercorner with one Fe(1)O4 tetrahedra,  a cornercorner with one Fe(2)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, corners with two equivalent Li(2)O4 tetrahedra, corners with three equivalent Si(1)O4 tetrahedra, and  an edgeedge with one Fe(2)O4 tetrahedra. In the third Li site, Li(3) is bonded to one O(1), one O(5), one O(6), and one O(7) atom to form LiO4 tetrahedra that share  a cornercorner with one Li(1)O4 tetrahedra,  a cornercorner with one Li(2)O4 tetrahedra,  a cornercorner with one Fe(1)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra, corners with three equivalent Fe(2)O4 tetrahedra, corners with three equivalent Si(2)O4 tetrahedra, and  an edgeedge with one Li(4)O4 tetrahedra. In the fourth Li site, Li(4) is bonded to one O(2), one O(5), one O(6), and one O(8) atom to form LiO4 tetrahedra that share  a cornercorner with one Li(1)O4 tetrahedra,  a cornercorner with one Li(2)O4 tetrahedra,  a cornercorner with one Fe(2)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, corners with three equivalent Fe(1)O4 tetrahedra, corners with three equivalent Si(1)O4 tetrahedra, and  an edgeedge with one Li(3)O4 tetrahedra. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(2), one O(3), one O(5), and one O(8) atom to form FeO4 tetrahedra that share  a cornercorner with one Li(1)O4 tetrahedra,  a cornercorner with one Li(2)O4 tetrahedra,  a cornercorner with one Li(3)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, corners with three equivalent Li(4)O4 tetrahedra, corners with three equivalent Si(1)O4 tetrahedra, and  an edgeedge with one Li(1)O4 tetrahedra. In the second Fe site, Fe(2) is bonded to one O(1), one O(4), one O(6), and one O(7) atom to form FeO4 tetrahedra that share  a cornercorner with one Li(1)O4 tetrahedra,  a cornercorner with one Li(2)O4 tetrahedra,  a cornercorner with one Li(4)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra, corners with three equivalent Li(3)O4 tetrahedra, corners with three 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(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Li(1)O4 tetrahedra,  a cornercorner with one Li(3)O4 tetrahedra,  a cornercorner with one Fe(2)O4 tetrahedra, corners with three equivalent Li(2)O4 tetrahedra, corners with three equivalent Li(4)O4 tetrahedra, and corners with three equivalent Fe(1)O4 tetrahedra. In the second Si site, Si(2) is bonded to one O(1), one O(3), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Li(2)O4 tetrahedra,  a cornercorner with one Li(4)O4 tetrahedra,  a cornercorner with one Fe(1)O4 tetrahedra, corners with three equivalent Li(1)O4 tetrahedra, corners with three equivalent Li(3)O4 tetrahedra, and corners with three 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(2) atom to form a mixture of distorted corner and edge-sharing OLi2FeSi tetrahedra. In the second O site, O(2) is bonded to one Li(1), one Li(4), one Fe(1), and one Si(1) atom to form a mixture of distorted corner and edge-sharing OLi2FeSi tetrahedra. In the third O site, O(3) 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 tetrahedra. In the fourth O site, O(4) is bonded to two equivalent Li(2), one Fe(2), and one Si(1) atom to form a mixture of distorted corner and edge-sharing OLi2FeSi tetrahedra. In the fifth O site, O(5) is bonded to one Li(3), one Li(4), one Fe(1), and one Si(1) atom to form a mixture of distorted corner and edge-sharing OLi2FeSi tetrahedra. In the sixth O site, O(6) is bonded to one Li(3), one Li(4), 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 one Li(1), one Li(3), one Fe(2), and one Si(2) atom to form corner-sharing OLi2FeSi tetrahedra. In the eighth O site, O(8) is bonded to one Li(2), one Li(4), one Fe(1), and one Si(1) atom to form corner-sharing OLi2FeSi tetrahedra.
Li2FeSiO4 is beta beryllia-derived structured and crystallizes in the monoclinic P2_1 space group. There are four inequivalent Li sites. In the first Li site, Li(1) is bonded to one O(2), one O(7), and two equivalent O(3) atoms to form LiO4 tetrahedra that share  a cornercorner with one Li(3)O4 tetrahedra,  a cornercorner with one Li(4)O4 tetrahedra,  a cornercorner with one Fe(1)O4 tetrahedra,  a cornercorner with one Fe(2)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra, corners with two equivalent Li(1)O4 tetrahedra, corners with three equivalent Si(2)O4 tetrahedra, and  an edgeedge with one Fe(1)O4 tetrahedra. The Li(1)-O(2) bond length is 2.00 Å. The Li(1)-O(7) bond length is 1.94 Å. There is one shorter (1.97 Å) and one longer (2.05 Å) Li(1)-O(3) bond length. In the second Li site, Li(2) is bonded to one O(1), one O(8), and two equivalent O(4) atoms to form LiO4 tetrahedra that share  a cornercorner with one Li(3)O4 tetrahedra,  a cornercorner with one Li(4)O4 tetrahedra,  a cornercorner with one Fe(1)O4 tetrahedra,  a cornercorner with one Fe(2)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, corners with two equivalent Li(2)O4 tetrahedra, corners with three equivalent Si(1)O4 tetrahedra, and  an edgeedge with one Fe(2)O4 tetrahedra. The Li(2)-O(1) bond length is 2.00 Å. The Li(2)-O(8) bond length is 1.94 Å. There is one shorter (1.97 Å) and one longer (2.05 Å) Li(2)-O(4) bond length. In the third Li site, Li(3) is bonded to one O(1), one O(5), one O(6), and one O(7) atom to form LiO4 tetrahedra that share  a cornercorner with one Li(1)O4 tetrahedra,  a cornercorner with one Li(2)O4 tetrahedra,  a cornercorner with one Fe(1)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra, corners with three equivalent Fe(2)O4 tetrahedra, corners with three equivalent Si(2)O4 tetrahedra, and  an edgeedge with one Li(4)O4 tetrahedra. The Li(3)-O(1) bond length is 1.99 Å. The Li(3)-O(5) bond length is 1.98 Å. The Li(3)-O(6) bond length is 2.03 Å. The Li(3)-O(7) bond length is 2.00 Å. In the fourth Li site, Li(4) is bonded to one O(2), one O(5), one O(6), and one O(8) atom to form LiO4 tetrahedra that share  a cornercorner with one Li(1)O4 tetrahedra,  a cornercorner with one Li(2)O4 tetrahedra,  a cornercorner with one Fe(2)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, corners with three equivalent Fe(1)O4 tetrahedra, corners with three equivalent Si(1)O4 tetrahedra, and  an edgeedge with one Li(3)O4 tetrahedra. The Li(4)-O(2) bond length is 1.99 Å. The Li(4)-O(5) bond length is 2.02 Å. The Li(4)-O(6) bond length is 1.98 Å. The Li(4)-O(8) bond length is 2.00 Å. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(2), one O(3), one O(5), and one O(8) atom to form FeO4 tetrahedra that share  a cornercorner with one Li(1)O4 tetrahedra,  a cornercorner with one Li(2)O4 tetrahedra,  a cornercorner with one Li(3)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, corners with three equivalent Li(4)O4 tetrahedra, corners with three equivalent Si(1)O4 tetrahedra, and  an edgeedge with one Li(1)O4 tetrahedra. The Fe(1)-O(2) bond length is 2.11 Å. The Fe(1)-O(3) bond length is 2.02 Å. The Fe(1)-O(5) bond length is 2.02 Å. The Fe(1)-O(8) bond length is 2.06 Å. In the second Fe site, Fe(2) is bonded to one O(1), one O(4), one O(6), and one O(7) atom to form FeO4 tetrahedra that share  a cornercorner with one Li(1)O4 tetrahedra,  a cornercorner with one Li(2)O4 tetrahedra,  a cornercorner with one Li(4)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra, corners with three equivalent Li(3)O4 tetrahedra, corners with three equivalent Si(2)O4 tetrahedra, and  an edgeedge with one Li(2)O4 tetrahedra. The Fe(2)-O(1) bond length is 2.11 Å. The Fe(2)-O(4) bond length is 2.02 Å. The Fe(2)-O(6) bond length is 2.02 Å. The Fe(2)-O(7) bond length is 2.06 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(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Li(1)O4 tetrahedra,  a cornercorner with one Li(3)O4 tetrahedra,  a cornercorner with one Fe(2)O4 tetrahedra, corners with three equivalent Li(2)O4 tetrahedra, corners with three equivalent Li(4)O4 tetrahedra, and corners with three equivalent Fe(1)O4 tetrahedra. The Si(1)-O(2) bond length is 1.66 Å. The Si(1)-O(4) bond length is 1.66 Å. The Si(1)-O(5) bond length is 1.66 Å. The Si(1)-O(8) 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(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Li(2)O4 tetrahedra,  a cornercorner with one Li(4)O4 tetrahedra,  a cornercorner with one Fe(1)O4 tetrahedra, corners with three equivalent Li(1)O4 tetrahedra, corners with three equivalent Li(3)O4 tetrahedra, and corners with three equivalent Fe(2)O4 tetrahedra. The Si(2)-O(1) bond length is 1.66 Å. The Si(2)-O(3) bond length is 1.66 Å. The Si(2)-O(6) bond length is 1.66 Å. The Si(2)-O(7) bond length is 1.65 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(2) atom to form a mixture of distorted corner and edge-sharing OLi2FeSi tetrahedra. In the second O site, O(2) is bonded to one Li(1), one Li(4), one Fe(1), and one Si(1) atom to form a mixture of distorted corner and edge-sharing OLi2FeSi tetrahedra. In the third O site, O(3) 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 tetrahedra. In the fourth O site, O(4) is bonded to two equivalent Li(2), one Fe(2), and one Si(1) atom to form a mixture of distorted corner and edge-sharing OLi2FeSi tetrahedra. In the fifth O site, O(5) is bonded to one Li(3), one Li(4), one Fe(1), and one Si(1) atom to form a mixture of distorted corner and edge-sharing OLi2FeSi tetrahedra. In the sixth O site, O(6) is bonded to one Li(3), one Li(4), 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 one Li(1), one Li(3), one Fe(2), and one Si(2) atom to form corner-sharing OLi2FeSi tetrahedra. In the eighth O site, O(8) is bonded to one Li(2), one Li(4), one Fe(1), and one Si(1) atom to form corner-sharing OLi2FeSi tetrahedra.