Li2FeP2O7 crystallizes in the monoclinic C2/m space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded to two equivalent O(2) and two equivalent O(4) atoms to form LiO4 tetrahedra that share corners with two equivalent Li(2)O4 tetrahedra and corners with four equivalent P(1)O4 tetrahedra. In the second Li site, Li(2) is bonded to two equivalent O(2) and two equivalent O(3) atoms to form distorted LiO4 tetrahedra that share corners with two equivalent Li(1)O4 tetrahedra and corners with four equivalent P(1)O4 tetrahedra. Fe(1) is bonded in a square co-planar geometry to two equivalent O(3) and two equivalent O(4) atoms. P(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form PO4 tetrahedra that share  a cornercorner with one P(1)O4 tetrahedra, corners with two equivalent Li(1)O4 tetrahedra, and corners with two equivalent Li(2)O4 tetrahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to two equivalent P(1) atoms. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Li(1), one Li(2), and one P(1) atom. In the third O site, O(3) is bonded in a trigonal planar geometry to one Li(2), one Fe(1), and one P(1) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Li(1), one Fe(1), and one P(1) atom.
Li2FeP2O7 crystallizes in the monoclinic C2/m space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded to two equivalent O(2) and two equivalent O(4) atoms to form LiO4 tetrahedra that share corners with two equivalent Li(2)O4 tetrahedra and corners with four equivalent P(1)O4 tetrahedra. Both Li(1)-O(2) bond lengths are 1.91 Å. Both Li(1)-O(4) bond lengths are 2.02 Å. In the second Li site, Li(2) is bonded to two equivalent O(2) and two equivalent O(3) atoms to form distorted LiO4 tetrahedra that share corners with two equivalent Li(1)O4 tetrahedra and corners with four equivalent P(1)O4 tetrahedra. Both Li(2)-O(2) bond lengths are 1.91 Å. Both Li(2)-O(3) bond lengths are 2.03 Å. Fe(1) is bonded in a square co-planar geometry to two equivalent O(3) and two equivalent O(4) atoms. Both Fe(1)-O(3) bond lengths are 2.08 Å. Both Fe(1)-O(4) bond lengths are 2.09 Å. P(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form PO4 tetrahedra that share  a cornercorner with one P(1)O4 tetrahedra, corners with two equivalent Li(1)O4 tetrahedra, and corners with two equivalent Li(2)O4 tetrahedra. The P(1)-O(1) bond length is 1.64 Å. The P(1)-O(2) bond length is 1.50 Å. The P(1)-O(3) bond length is 1.55 Å. The P(1)-O(4) bond length is 1.55 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to two equivalent P(1) atoms. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Li(1), one Li(2), and one P(1) atom. In the third O site, O(3) is bonded in a trigonal planar geometry to one Li(2), one Fe(1), and one P(1) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Li(1), one Fe(1), and one P(1) atom.