LiFeP2O7 crystallizes in the monoclinic P2_1/c space group. Li(1) is bonded to one O(2), one O(5), one O(7), and two equivalent O(1) atoms to form distorted LiO5 square pyramids that share corners with two equivalent Li(1)O5 square pyramids,  a cornercorner with one P(1)O4 tetrahedra, corners with four equivalent P(2)O4 tetrahedra,  a cornercorner with one Fe(1)O5 trigonal bipyramid, and  an edgeedge with one Fe(1)O5 trigonal bipyramid. Fe(1) is bonded to one O(2), one O(3), one O(4), one O(5), and one O(7) atom to form FeO5 trigonal bipyramids that share  a cornercorner with one Li(1)O5 square pyramid, corners with two equivalent P(2)O4 tetrahedra, corners with three equivalent P(1)O4 tetrahedra, and  an edgeedge with one Li(1)O5 square pyramid. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(3), one O(4), one O(6), and one O(7) atom to form PO4 tetrahedra that share  a cornercorner with one Li(1)O5 square pyramid,  a cornercorner with one P(2)O4 tetrahedra, and corners with three equivalent Fe(1)O5 trigonal bipyramids. In the second P site, P(2) is bonded to one O(1), one O(2), one O(5), and one O(6) atom to form PO4 tetrahedra that share corners with four equivalent Li(1)O5 square pyramids,  a cornercorner with one P(1)O4 tetrahedra, and corners with two equivalent Fe(1)O5 trigonal bipyramids. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Li(1) and one P(2) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Li(1), one Fe(1), and one P(2) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Fe(1) and one P(1) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one Fe(1) and one P(1) atom. In the fifth O site, O(5) is bonded in a trigonal planar geometry to one Li(1), one Fe(1), and one P(2) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Li(1), one Fe(1), and one P(1) atom.
LiFeP2O7 crystallizes in the monoclinic P2_1/c space group. Li(1) is bonded to one O(2), one O(5), one O(7), and two equivalent O(1) atoms to form distorted LiO5 square pyramids that share corners with two equivalent Li(1)O5 square pyramids,  a cornercorner with one P(1)O4 tetrahedra, corners with four equivalent P(2)O4 tetrahedra,  a cornercorner with one Fe(1)O5 trigonal bipyramid, and  an edgeedge with one Fe(1)O5 trigonal bipyramid. The Li(1)-O(2) bond length is 2.10 Å. The Li(1)-O(5) bond length is 2.19 Å. The Li(1)-O(7) bond length is 2.44 Å. There is one shorter (2.17 Å) and one longer (2.54 Å) Li(1)-O(1) bond length. Fe(1) is bonded to one O(2), one O(3), one O(4), one O(5), and one O(7) atom to form FeO5 trigonal bipyramids that share  a cornercorner with one Li(1)O5 square pyramid, corners with two equivalent P(2)O4 tetrahedra, corners with three equivalent P(1)O4 tetrahedra, and  an edgeedge with one Li(1)O5 square pyramid. The Fe(1)-O(2) bond length is 2.02 Å. The Fe(1)-O(3) bond length is 1.98 Å. The Fe(1)-O(4) bond length is 1.97 Å. The Fe(1)-O(5) bond length is 1.99 Å. The Fe(1)-O(7) bond length is 1.93 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(3), one O(4), one O(6), and one O(7) atom to form PO4 tetrahedra that share  a cornercorner with one Li(1)O5 square pyramid,  a cornercorner with one P(2)O4 tetrahedra, and corners with three equivalent Fe(1)O5 trigonal bipyramids. The P(1)-O(3) bond length is 1.53 Å. The P(1)-O(4) bond length is 1.53 Å. The P(1)-O(6) bond length is 1.60 Å. The P(1)-O(7) bond length is 1.54 Å. In the second P site, P(2) is bonded to one O(1), one O(2), one O(5), and one O(6) atom to form PO4 tetrahedra that share corners with four equivalent Li(1)O5 square pyramids,  a cornercorner with one P(1)O4 tetrahedra, and corners with two equivalent Fe(1)O5 trigonal bipyramids. The P(2)-O(1) bond length is 1.51 Å. The P(2)-O(2) bond length is 1.55 Å. The P(2)-O(5) bond length is 1.54 Å. The P(2)-O(6) bond length is 1.63 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Li(1) and one P(2) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Li(1), one Fe(1), and one P(2) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Fe(1) and one P(1) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one Fe(1) and one P(1) atom. In the fifth O site, O(5) is bonded in a trigonal planar geometry to one Li(1), one Fe(1), and one P(2) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Li(1), one Fe(1), and one P(1) atom.