Cr3(P2O7)2 crystallizes in the triclinic P-1 space group. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(1), one O(3), one O(7), and two equivalent O(2) atoms to form CrO5 trigonal bipyramids that share corners with two equivalent P(2)O4 tetrahedra, corners with three equivalent P(1)O4 tetrahedra, and  an edgeedge with one Cr(1)O5 trigonal bipyramid. In the second Cr site, Cr(2) is bonded in a square co-planar geometry to two equivalent O(4) and two equivalent O(5) atoms. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(2), one O(5), and one O(6) atom to form PO4 tetrahedra that share  a cornercorner with one P(2)O4 tetrahedra and corners with three equivalent Cr(1)O5 trigonal bipyramids. In the second P site, P(2) is bonded to one O(3), one O(4), one O(6), and one O(7) atom to form PO4 tetrahedra that share  a cornercorner with one P(1)O4 tetrahedra and corners with two equivalent Cr(1)O5 trigonal bipyramids. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to one Cr(1) and one P(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to two equivalent Cr(1) and one P(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Cr(1) and one P(2) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Cr(2) and one P(2) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Cr(2) and one P(1) atom. In the sixth O site, O(6) is bonded in a distorted bent 150 degrees geometry to one P(1) and one P(2) atom. In the seventh O site, O(7) is bonded in a bent 120 degrees geometry to one Cr(1) and one P(2) atom.
Cr3(P2O7)2 crystallizes in the triclinic P-1 space group. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(1), one O(3), one O(7), and two equivalent O(2) atoms to form CrO5 trigonal bipyramids that share corners with two equivalent P(2)O4 tetrahedra, corners with three equivalent P(1)O4 tetrahedra, and  an edgeedge with one Cr(1)O5 trigonal bipyramid. The Cr(1)-O(1) bond length is 1.93 Å. The Cr(1)-O(3) bond length is 1.93 Å. The Cr(1)-O(7) bond length is 1.94 Å. There is one shorter (2.06 Å) and one longer (2.08 Å) Cr(1)-O(2) bond length. In the second Cr site, Cr(2) is bonded in a square co-planar geometry to two equivalent O(4) and two equivalent O(5) atoms. Both Cr(2)-O(4) bond lengths are 2.04 Å. Both Cr(2)-O(5) bond lengths are 2.07 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(2), one O(5), and one O(6) atom to form PO4 tetrahedra that share  a cornercorner with one P(2)O4 tetrahedra and corners with three equivalent Cr(1)O5 trigonal bipyramids. The P(1)-O(1) bond length is 1.54 Å. The P(1)-O(2) bond length is 1.59 Å. The P(1)-O(5) bond length is 1.49 Å. The P(1)-O(6) bond length is 1.61 Å. In the second P site, P(2) is bonded to one O(3), one O(4), one O(6), and one O(7) atom to form PO4 tetrahedra that share  a cornercorner with one P(1)O4 tetrahedra and corners with two equivalent Cr(1)O5 trigonal bipyramids. The P(2)-O(3) bond length is 1.53 Å. The P(2)-O(4) bond length is 1.50 Å. The P(2)-O(6) bond length is 1.63 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 bent 120 degrees geometry to one Cr(1) and one P(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to two equivalent Cr(1) and one P(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Cr(1) and one P(2) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Cr(2) and one P(2) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Cr(2) and one P(1) atom. In the sixth O site, O(6) is bonded in a distorted bent 150 degrees geometry to one P(1) and one P(2) atom. In the seventh O site, O(7) is bonded in a bent 120 degrees geometry to one Cr(1) and one P(2) atom.