Li2CuP2O7 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 6-coordinate geometry to one O(1), one O(3), one O(4), one O(7), and two equivalent O(5) atoms. In the second Li site, Li(2) is bonded to one O(1), one O(3), one O(4), one O(5), and one O(6) atom to form distorted LiO5 square pyramids that share  a cornercorner with one P(2)O4 tetrahedra, corners with two equivalent P(1)O4 tetrahedra,  a cornercorner with one Cu(1)O5 trigonal bipyramid,  an edgeedge with one P(2)O4 tetrahedra, and  an edgeedge with one Cu(1)O5 trigonal bipyramid. Cu(1) is bonded to one O(1), one O(4), one O(6), and two equivalent O(2) atoms to form distorted CuO5 trigonal bipyramids that share  a cornercorner with one Li(2)O5 square pyramid,  a cornercorner with one P(2)O4 tetrahedra, corners with four equivalent P(1)O4 tetrahedra,  an edgeedge with one Li(2)O5 square pyramid, and  an edgeedge with one Cu(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(6), and one O(7) atom to form PO4 tetrahedra that share corners with two equivalent Li(2)O5 square pyramids,  a cornercorner with one P(2)O4 tetrahedra, and corners with four equivalent Cu(1)O5 trigonal bipyramids. In the second P site, P(2) is bonded to one O(3), one O(4), one O(5), and one O(7) atom to form PO4 tetrahedra that share  a cornercorner with one Li(2)O5 square pyramid,  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one Cu(1)O5 trigonal bipyramid, and  an edgeedge with one Li(2)O5 square pyramid. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Li(1), one Li(2), one Cu(1), and one P(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to two equivalent Cu(1) and one P(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Li(1), one Li(2), and one P(2) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Li(1), one Li(2), one Cu(1), and one P(2) atom. In the fifth O site, O(5) is bonded to one Li(2), two equivalent Li(1), and one P(2) atom to form distorted edge-sharing OLi3P trigonal pyramids. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Li(2), one Cu(1), and one P(1) atom. In the seventh O site, O(7) is bonded in a distorted bent 150 degrees geometry to one Li(1), one P(1), and one P(2) atom.
Li2CuP2O7 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 6-coordinate geometry to one O(1), one O(3), one O(4), one O(7), and two equivalent O(5) atoms. The Li(1)-O(1) bond length is 2.67 Å. The Li(1)-O(3) bond length is 1.98 Å. The Li(1)-O(4) bond length is 2.25 Å. The Li(1)-O(7) bond length is 2.58 Å. There is one shorter (2.13 Å) and one longer (2.47 Å) Li(1)-O(5) bond length. In the second Li site, Li(2) is bonded to one O(1), one O(3), one O(4), one O(5), and one O(6) atom to form distorted LiO5 square pyramids that share  a cornercorner with one P(2)O4 tetrahedra, corners with two equivalent P(1)O4 tetrahedra,  a cornercorner with one Cu(1)O5 trigonal bipyramid,  an edgeedge with one P(2)O4 tetrahedra, and  an edgeedge with one Cu(1)O5 trigonal bipyramid. The Li(2)-O(1) bond length is 2.02 Å. The Li(2)-O(3) bond length is 2.24 Å. The Li(2)-O(4) bond length is 2.34 Å. The Li(2)-O(5) bond length is 2.04 Å. The Li(2)-O(6) bond length is 2.05 Å. Cu(1) is bonded to one O(1), one O(4), one O(6), and two equivalent O(2) atoms to form distorted CuO5 trigonal bipyramids that share  a cornercorner with one Li(2)O5 square pyramid,  a cornercorner with one P(2)O4 tetrahedra, corners with four equivalent P(1)O4 tetrahedra,  an edgeedge with one Li(2)O5 square pyramid, and  an edgeedge with one Cu(1)O5 trigonal bipyramid. The Cu(1)-O(1) bond length is 1.98 Å. The Cu(1)-O(4) bond length is 1.96 Å. The Cu(1)-O(6) bond length is 2.31 Å. There is one shorter (1.99 Å) and one longer (2.01 Å) Cu(1)-O(2) bond length. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(2), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with two equivalent Li(2)O5 square pyramids,  a cornercorner with one P(2)O4 tetrahedra, and corners with four equivalent Cu(1)O5 trigonal bipyramids. The P(1)-O(1) bond length is 1.54 Å. The P(1)-O(2) bond length is 1.57 Å. The P(1)-O(6) bond length is 1.50 Å. The P(1)-O(7) bond length is 1.61 Å. In the second P site, P(2) is bonded to one O(3), one O(4), one O(5), and one O(7) atom to form PO4 tetrahedra that share  a cornercorner with one Li(2)O5 square pyramid,  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one Cu(1)O5 trigonal bipyramid, and  an edgeedge with one Li(2)O5 square pyramid. The P(2)-O(3) bond length is 1.52 Å. The P(2)-O(4) bond length is 1.56 Å. The P(2)-O(5) bond length is 1.52 Å. The P(2)-O(7) bond length is 1.64 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Li(1), one Li(2), one Cu(1), and one P(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to two equivalent Cu(1) and one P(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Li(1), one Li(2), and one P(2) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Li(1), one Li(2), one Cu(1), and one P(2) atom. In the fifth O site, O(5) is bonded to one Li(2), two equivalent Li(1), and one P(2) atom to form distorted edge-sharing OLi3P trigonal pyramids. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Li(2), one Cu(1), and one P(1) atom. In the seventh O site, O(7) is bonded in a distorted bent 150 degrees geometry to one Li(1), one P(1), and one P(2) atom.