Li2FeP2O7 crystallizes in the monoclinic C2/c space group. Li(1) is bonded to one O(1), two equivalent O(3), and two equivalent O(4) atoms to form distorted LiO5 trigonal bipyramids that share corners with five equivalent P(1)O4 tetrahedra, corners with two equivalent Li(1)O5 trigonal bipyramids, and  an edgeedge with one Li(1)O5 trigonal bipyramid. Fe(1) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(3) 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 and corners with five equivalent Li(1)O5 trigonal bipyramids. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Li(1), one Fe(1), and one P(1) atom. In the second O site, O(2) is bonded in a bent 120 degrees geometry to two equivalent P(1) atoms. In the third O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Li(1), one Fe(1), and one P(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to two equivalent Li(1) and one P(1) atom.
Li2FeP2O7 crystallizes in the monoclinic C2/c space group. Li(1) is bonded to one O(1), two equivalent O(3), and two equivalent O(4) atoms to form distorted LiO5 trigonal bipyramids that share corners with five equivalent P(1)O4 tetrahedra, corners with two equivalent Li(1)O5 trigonal bipyramids, and  an edgeedge with one Li(1)O5 trigonal bipyramid. The Li(1)-O(1) bond length is 2.06 Å. There is one shorter (2.47 Å) and one longer (2.51 Å) Li(1)-O(3) bond length. There is one shorter (1.98 Å) and one longer (2.00 Å) Li(1)-O(4) bond length. Fe(1) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(3) atoms. Both Fe(1)-O(1) bond lengths are 2.01 Å. Both Fe(1)-O(3) bond lengths are 2.05 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 and corners with five equivalent Li(1)O5 trigonal bipyramids. The P(1)-O(1) bond length is 1.54 Å. The P(1)-O(2) bond length is 1.64 Å. The P(1)-O(3) bond length is 1.55 Å. The P(1)-O(4) bond length is 1.51 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Li(1), one Fe(1), and one P(1) atom. In the second O site, O(2) is bonded in a bent 120 degrees geometry to two equivalent P(1) atoms. In the third O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Li(1), one Fe(1), and one P(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to two equivalent Li(1) and one P(1) atom.