LiFeP2O7 crystallizes in the monoclinic P2_1/c space group. Li(1) is bonded to one O(2), one O(4), one O(5), and two equivalent O(3) atoms to form distorted LiO5 trigonal bipyramids that share corners with three equivalent Fe(1)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, corners with two equivalent Li(1)O5 trigonal bipyramids, and  an edgeedge with one Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 56-66°. Fe(1) is bonded to one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form FeO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, corners with three equivalent Li(1)O5 trigonal bipyramids, and  an edgeedge with one Li(1)O5 trigonal bipyramid. There are two inequivalent P sites. In the first P site, P(1) 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 three equivalent Fe(1)O6 octahedra,  a cornercorner with one P(2)O4 tetrahedra, and corners with two equivalent Li(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 38-53°. In the second P site, P(2) is bonded to one O(1), one O(3), one O(4), and one O(7) atom to form PO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra, and corners with three equivalent Li(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 22-58°. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Li(1), one Fe(1), and one P(1) atom. In the third O site, O(3) is bonded to two equivalent Li(1), one Fe(1), and one P(2) atom to form distorted corner-sharing OLi2FeP trigonal pyramids. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Li(1), one Fe(1), and one P(2) 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(1) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Fe(1) and one P(1) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Fe(1) and one P(2) atom.
LiFeP2O7 crystallizes in the monoclinic P2_1/c space group. Li(1) is bonded to one O(2), one O(4), one O(5), and two equivalent O(3) atoms to form distorted LiO5 trigonal bipyramids that share corners with three equivalent Fe(1)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, corners with two equivalent Li(1)O5 trigonal bipyramids, and  an edgeedge with one Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 56-66°. The Li(1)-O(2) bond length is 2.21 Å. The Li(1)-O(4) bond length is 2.11 Å. The Li(1)-O(5) bond length is 2.30 Å. There is one shorter (2.30 Å) and one longer (2.38 Å) Li(1)-O(3) bond length. Fe(1) is bonded to one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form FeO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, corners with three equivalent Li(1)O5 trigonal bipyramids, and  an edgeedge with one Li(1)O5 trigonal bipyramid. The Fe(1)-O(2) bond length is 2.05 Å. The Fe(1)-O(3) bond length is 2.12 Å. The Fe(1)-O(4) bond length is 2.09 Å. The Fe(1)-O(5) bond length is 2.10 Å. The Fe(1)-O(6) bond length is 1.98 Å. The Fe(1)-O(7) bond length is 1.92 Å. There are two inequivalent P sites. In the first P site, P(1) 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 three equivalent Fe(1)O6 octahedra,  a cornercorner with one P(2)O4 tetrahedra, and corners with two equivalent Li(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 38-53°. The P(1)-O(1) bond length is 1.62 Å. The P(1)-O(2) bond length is 1.54 Å. The P(1)-O(5) bond length is 1.54 Å. The P(1)-O(6) bond length is 1.51 Å. In the second P site, P(2) is bonded to one O(1), one O(3), one O(4), and one O(7) atom to form PO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra, and corners with three equivalent Li(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 22-58°. The P(2)-O(1) bond length is 1.62 Å. The P(2)-O(3) bond length is 1.55 Å. The P(2)-O(4) bond length is 1.54 Å. The P(2)-O(7) bond length is 1.51 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Li(1), one Fe(1), and one P(1) atom. In the third O site, O(3) is bonded to two equivalent Li(1), one Fe(1), and one P(2) atom to form distorted corner-sharing OLi2FeP trigonal pyramids. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Li(1), one Fe(1), and one P(2) 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(1) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Fe(1) and one P(1) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Fe(1) and one P(2) atom.