Cu2P2O7 crystallizes in the monoclinic C2/c space group. Cu(1) is bonded to one O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted CuO5 trigonal bipyramids that share corners with five equivalent P(1)O4 tetrahedra and edges with two equivalent Cu(1)O5 trigonal bipyramids. 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 Cu(1)O5 trigonal bipyramids. There are four inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Cu(1) and one P(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to two equivalent Cu(1) and one P(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to two equivalent P(1) atoms. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to two equivalent Cu(1) and one P(1) atom.
Cu2P2O7 crystallizes in the monoclinic C2/c space group. Cu(1) is bonded to one O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted CuO5 trigonal bipyramids that share corners with five equivalent P(1)O4 tetrahedra and edges with two equivalent Cu(1)O5 trigonal bipyramids. The Cu(1)-O(1) bond length is 1.91 Å. There is one shorter (1.93 Å) and one longer (2.28 Å) Cu(1)-O(2) bond length. There is one shorter (1.98 Å) and one longer (1.99 Å) Cu(1)-O(4) bond length. 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 Cu(1)O5 trigonal bipyramids. The P(1)-O(1) bond length is 1.50 Å. The P(1)-O(2) bond length is 1.52 Å. The P(1)-O(3) bond length is 1.59 Å. The P(1)-O(4) bond length is 1.54 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Cu(1) and one P(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to two equivalent Cu(1) and one P(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to two equivalent P(1) atoms. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to two equivalent Cu(1) and one P(1) atom.