Li2FeP2O7 crystallizes in the triclinic P-1 space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded in a 2-coordinate geometry to one O(4) and one O(7) atom. In the second Li site, Li(2) is bonded in a 5-coordinate geometry to one P(2), one O(1), one O(2), one O(3), and one O(4) atom. Fe(1) is bonded in a 4-coordinate geometry to one O(1), one O(2), one O(3), and one O(6) atom. There are two inequivalent P sites. In the first P site, P(1) is bonded in a 3-coordinate geometry to one O(1), one O(2), one O(6), and one O(7) atom. In the second P site, P(2) is bonded in a 3-coordinate geometry to one Li(2), one O(3), one O(4), one O(5), and one O(7) atom. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted water-like geometry to one Li(2), one Fe(1), and one P(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Li(2), one Fe(1), and one P(1) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Li(2), one Fe(1), and one P(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Li(1), one Li(2), and one P(2) atom. In the fifth O site, O(5) is bonded in a single-bond geometry to one P(2) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Fe(1) and one P(1) atom. In the seventh O site, O(7) is bonded in a distorted single-bond geometry to one Li(1), one P(1), and one P(2) atom.
Li2FeP2O7 crystallizes in the triclinic P-1 space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded in a 2-coordinate geometry to one O(4) and one O(7) atom. The Li(1)-O(4) bond length is 1.54 Å. The Li(1)-O(7) bond length is 1.95 Å. In the second Li site, Li(2) is bonded in a 5-coordinate geometry to one P(2), one O(1), one O(2), one O(3), and one O(4) atom. The Li(2)-P(2) bond length is 2.08 Å. The Li(2)-O(1) bond length is 1.69 Å. The Li(2)-O(2) bond length is 2.15 Å. The Li(2)-O(3) bond length is 2.04 Å. The Li(2)-O(4) bond length is 1.80 Å. Fe(1) is bonded in a 4-coordinate geometry to one O(1), one O(2), one O(3), and one O(6) atom. The Fe(1)-O(1) bond length is 2.22 Å. The Fe(1)-O(2) bond length is 2.43 Å. The Fe(1)-O(3) bond length is 2.13 Å. The Fe(1)-O(6) bond length is 1.76 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded in a 3-coordinate geometry to one O(1), one O(2), one O(6), and one O(7) atom. The P(1)-O(1) bond length is 1.17 Å. The P(1)-O(2) bond length is 1.54 Å. The P(1)-O(6) bond length is 1.57 Å. The P(1)-O(7) bond length is 2.41 Å. In the second P site, P(2) is bonded in a 3-coordinate geometry to one Li(2), one O(3), one O(4), one O(5), and one O(7) atom. The P(2)-O(3) bond length is 1.31 Å. The P(2)-O(4) bond length is 1.53 Å. The P(2)-O(5) bond length is 1.57 Å. The P(2)-O(7) bond length is 2.31 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted water-like geometry to one Li(2), one Fe(1), and one P(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Li(2), one Fe(1), and one P(1) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Li(2), one Fe(1), and one P(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Li(1), one Li(2), and one P(2) atom. In the fifth O site, O(5) is bonded in a single-bond geometry to one P(2) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Fe(1) and one P(1) atom. In the seventh O site, O(7) is bonded in a distorted single-bond geometry to one Li(1), one P(1), and one P(2) atom.