Li2FeSiO4 is beta beryllia-derived structured and crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form LiO4 tetrahedra that share corners with two equivalent Fe(1)O4 tetrahedra, corners with four equivalent Li(2)O4 tetrahedra, corners with four equivalent Si(1)O4 tetrahedra, and  an edgeedge with one Li(1)O4 tetrahedra. In the second Li site, Li(2) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form LiO4 tetrahedra that share corners with four equivalent Li(1)O4 tetrahedra, corners with four equivalent Fe(1)O4 tetrahedra, and corners with four equivalent Si(1)O4 tetrahedra. Fe(1) is bonded to one O(2), one O(3), and two equivalent O(4) atoms to form FeO4 tetrahedra that share corners with two equivalent Li(1)O4 tetrahedra, corners with four equivalent Li(2)O4 tetrahedra, corners with four equivalent Si(1)O4 tetrahedra, and  an edgeedge with one Fe(1)O4 tetrahedra. 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 four equivalent Li(1)O4 tetrahedra, corners with four equivalent Li(2)O4 tetrahedra, and corners with four equivalent Fe(1)O4 tetrahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Li(2), two equivalent Li(1), and one Si(1) atom to form OLi3Si tetrahedra that share corners with two equivalent O(4)LiFe2Si tetrahedra, corners with four equivalent O(2)Li2FeSi tetrahedra, corners with four equivalent O(3)Li2FeSi tetrahedra, and  an edgeedge with one O(1)Li3Si tetrahedra. In the second O site, O(2) is bonded to one Li(1), one Li(2), one Fe(1), and one Si(1) atom to form OLi2FeSi tetrahedra that share corners with four equivalent O(3)Li2FeSi tetrahedra, corners with four equivalent O(1)Li3Si tetrahedra, and corners with four equivalent O(4)LiFe2Si tetrahedra. In the third O site, O(3) is bonded to one Li(1), one Li(2), one Fe(1), and one Si(1) atom to form OLi2FeSi tetrahedra that share corners with four equivalent O(2)Li2FeSi tetrahedra, corners with four equivalent O(1)Li3Si tetrahedra, and corners with four equivalent O(4)LiFe2Si tetrahedra. In the fourth O site, O(4) is bonded to one Li(2), two equivalent Fe(1), and one Si(1) atom to form distorted OLiFe2Si tetrahedra that share corners with two equivalent O(1)Li3Si tetrahedra, corners with four equivalent O(2)Li2FeSi tetrahedra, corners with four equivalent O(3)Li2FeSi tetrahedra, and  an edgeedge with one O(4)LiFe2Si tetrahedra.
Li2FeSiO4 is beta beryllia-derived structured and crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form LiO4 tetrahedra that share corners with two equivalent Fe(1)O4 tetrahedra, corners with four equivalent Li(2)O4 tetrahedra, corners with four equivalent Si(1)O4 tetrahedra, and  an edgeedge with one Li(1)O4 tetrahedra. The Li(1)-O(2) bond length is 1.97 Å. The Li(1)-O(3) bond length is 2.02 Å. There is one shorter (1.96 Å) and one longer (1.98 Å) Li(1)-O(1) bond length. In the second Li site, Li(2) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form LiO4 tetrahedra that share corners with four equivalent Li(1)O4 tetrahedra, corners with four equivalent Fe(1)O4 tetrahedra, and corners with four equivalent Si(1)O4 tetrahedra. The Li(2)-O(1) bond length is 1.96 Å. The Li(2)-O(2) bond length is 1.99 Å. The Li(2)-O(3) bond length is 2.02 Å. The Li(2)-O(4) bond length is 2.18 Å. Fe(1) is bonded to one O(2), one O(3), and two equivalent O(4) atoms to form FeO4 tetrahedra that share corners with two equivalent Li(1)O4 tetrahedra, corners with four equivalent Li(2)O4 tetrahedra, corners with four equivalent Si(1)O4 tetrahedra, and  an edgeedge with one Fe(1)O4 tetrahedra. The Fe(1)-O(2) bond length is 2.00 Å. The Fe(1)-O(3) bond length is 1.97 Å. There is one shorter (2.06 Å) and one longer (2.15 Å) Fe(1)-O(4) bond length. 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 four equivalent Li(1)O4 tetrahedra, corners with four equivalent Li(2)O4 tetrahedra, and corners with four equivalent Fe(1)O4 tetrahedra. The Si(1)-O(1) bond length is 1.62 Å. The Si(1)-O(2) bond length is 1.65 Å. The Si(1)-O(3) bond length is 1.66 Å. The Si(1)-O(4) bond length is 1.69 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Li(2), two equivalent Li(1), and one Si(1) atom to form OLi3Si tetrahedra that share corners with two equivalent O(4)LiFe2Si tetrahedra, corners with four equivalent O(2)Li2FeSi tetrahedra, corners with four equivalent O(3)Li2FeSi tetrahedra, and  an edgeedge with one O(1)Li3Si tetrahedra. In the second O site, O(2) is bonded to one Li(1), one Li(2), one Fe(1), and one Si(1) atom to form OLi2FeSi tetrahedra that share corners with four equivalent O(3)Li2FeSi tetrahedra, corners with four equivalent O(1)Li3Si tetrahedra, and corners with four equivalent O(4)LiFe2Si tetrahedra. In the third O site, O(3) is bonded to one Li(1), one Li(2), one Fe(1), and one Si(1) atom to form OLi2FeSi tetrahedra that share corners with four equivalent O(2)Li2FeSi tetrahedra, corners with four equivalent O(1)Li3Si tetrahedra, and corners with four equivalent O(4)LiFe2Si tetrahedra. In the fourth O site, O(4) is bonded to one Li(2), two equivalent Fe(1), and one Si(1) atom to form distorted OLiFe2Si tetrahedra that share corners with two equivalent O(1)Li3Si tetrahedra, corners with four equivalent O(2)Li2FeSi tetrahedra, corners with four equivalent O(3)Li2FeSi tetrahedra, and  an edgeedge with one O(4)LiFe2Si tetrahedra.