BaCuP2O7 crystallizes in the triclinic P-1 space group. Ba(1) is bonded in a 10-coordinate geometry to one O(1), one O(3), one O(5), two equivalent O(2), two equivalent O(7), and three equivalent O(6) atoms. Cu(1) is bonded to one O(3), one O(5), one O(7), and two equivalent O(1) atoms to form distorted CuO5 square pyramids that share corners with two equivalent P(2)O4 tetrahedra, corners with three equivalent P(1)O4 tetrahedra, and  an edgeedge with one Cu(1)O5 square pyramid. There are two inequivalent P sites. In the first P site, 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 corners with three equivalent Cu(1)O5 square pyramids and  a cornercorner with one P(2)O4 tetrahedra. In the second P site, P(2) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with two equivalent Cu(1)O5 square pyramids and  a cornercorner with one P(1)O4 tetrahedra. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ba(1), two equivalent Cu(1), and one P(1) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to two equivalent Ba(1) and one P(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Ba(1), one Cu(1), and one P(1) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom. In the fifth O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Ba(1), one Cu(1), and one P(2) atom. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to three equivalent Ba(1) and one P(2) atom. In the seventh O site, O(7) is bonded in a 2-coordinate geometry to two equivalent Ba(1), one Cu(1), and one P(2) atom.
BaCuP2O7 crystallizes in the triclinic P-1 space group. Ba(1) is bonded in a 10-coordinate geometry to one O(1), one O(3), one O(5), two equivalent O(2), two equivalent O(7), and three equivalent O(6) atoms. The Ba(1)-O(1) bond length is 2.91 Å. The Ba(1)-O(3) bond length is 2.80 Å. The Ba(1)-O(5) bond length is 2.98 Å. There is one shorter (2.73 Å) and one longer (3.14 Å) Ba(1)-O(2) bond length. There is one shorter (2.90 Å) and one longer (3.07 Å) Ba(1)-O(7) bond length. There are a spread of Ba(1)-O(6) bond distances ranging from 2.83-2.93 Å. Cu(1) is bonded to one O(3), one O(5), one O(7), and two equivalent O(1) atoms to form distorted CuO5 square pyramids that share corners with two equivalent P(2)O4 tetrahedra, corners with three equivalent P(1)O4 tetrahedra, and  an edgeedge with one Cu(1)O5 square pyramid. The Cu(1)-O(3) bond length is 1.97 Å. The Cu(1)-O(5) bond length is 1.98 Å. The Cu(1)-O(7) bond length is 2.01 Å. There is one shorter (2.02 Å) and one longer (2.39 Å) Cu(1)-O(1) 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(3), and one O(4) atom to form PO4 tetrahedra that share corners with three equivalent Cu(1)O5 square pyramids and  a cornercorner with one P(2)O4 tetrahedra. The P(1)-O(1) bond length is 1.56 Å. The P(1)-O(2) bond length is 1.50 Å. The P(1)-O(3) bond length is 1.55 Å. The P(1)-O(4) bond length is 1.63 Å. In the second P site, P(2) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with two equivalent Cu(1)O5 square pyramids and  a cornercorner with one P(1)O4 tetrahedra. The P(2)-O(4) bond length is 1.62 Å. The P(2)-O(5) bond length is 1.54 Å. The P(2)-O(6) bond length is 1.52 Å. The P(2)-O(7) bond length is 1.55 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ba(1), two equivalent Cu(1), and one P(1) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to two equivalent Ba(1) and one P(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Ba(1), one Cu(1), and one P(1) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom. In the fifth O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Ba(1), one Cu(1), and one P(2) atom. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to three equivalent Ba(1) and one P(2) atom. In the seventh O site, O(7) is bonded in a 2-coordinate geometry to two equivalent Ba(1), one Cu(1), and one P(2) atom.