Cr2P5O16 crystallizes in the monoclinic P2/c space group. Cr(1) is bonded to one O(1), one O(2), one O(4), one O(5), one O(6), and one O(7) atom to form CrO6 octahedra that share  a cornercorner with one P(1)O4 tetrahedra, corners with two equivalent P(3)O4 tetrahedra, and corners with three equivalent P(2)O4 tetrahedra. There are three inequivalent P sites. In the first P site, P(1) is bonded to two equivalent O(7) and two equivalent O(8) atoms to form PO4 tetrahedra that share corners with two equivalent Cr(1)O6 octahedra and corners with two equivalent P(3)O4 tetrahedra. The corner-sharing octahedral tilt angles are 44°. In the second P site, P(2) is bonded to one O(1), one O(2), one O(3), and one O(6) atom to form PO4 tetrahedra that share corners with three equivalent Cr(1)O6 octahedra and  a cornercorner with one P(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 40-42°. In the third P site, P(3) is bonded to one O(3), one O(4), one O(5), and one O(8) atom to form PO4 tetrahedra that share corners with two equivalent Cr(1)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra, and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 43-47°. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Cr(1) and one P(2) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Cr(1) and one P(2) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one P(2) and one P(3) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one Cr(1) and one P(3) atom. In the fifth O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Cr(1) and one P(3) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Cr(1) and one P(2) atom. In the seventh O site, O(7) is bonded in a distorted bent 150 degrees geometry to one Cr(1) and one P(1) atom. In the eighth O site, O(8) is bonded in a bent 120 degrees geometry to one P(1) and one P(3) atom.
Cr2P5O16 crystallizes in the monoclinic P2/c space group. Cr(1) is bonded to one O(1), one O(2), one O(4), one O(5), one O(6), and one O(7) atom to form CrO6 octahedra that share  a cornercorner with one P(1)O4 tetrahedra, corners with two equivalent P(3)O4 tetrahedra, and corners with three equivalent P(2)O4 tetrahedra. The Cr(1)-O(1) bond length is 1.95 Å. The Cr(1)-O(2) bond length is 2.00 Å. The Cr(1)-O(4) bond length is 2.00 Å. The Cr(1)-O(5) bond length is 1.97 Å. The Cr(1)-O(6) bond length is 1.94 Å. The Cr(1)-O(7) bond length is 2.01 Å. There are three inequivalent P sites. In the first P site, P(1) is bonded to two equivalent O(7) and two equivalent O(8) atoms to form PO4 tetrahedra that share corners with two equivalent Cr(1)O6 octahedra and corners with two equivalent P(3)O4 tetrahedra. The corner-sharing octahedral tilt angles are 44°. Both P(1)-O(7) bond lengths are 1.50 Å. Both P(1)-O(8) bond lengths are 1.60 Å. In the second P site, P(2) is bonded to one O(1), one O(2), one O(3), and one O(6) atom to form PO4 tetrahedra that share corners with three equivalent Cr(1)O6 octahedra and  a cornercorner with one P(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 40-42°. The P(2)-O(1) bond length is 1.52 Å. The P(2)-O(2) bond length is 1.52 Å. The P(2)-O(3) bond length is 1.62 Å. The P(2)-O(6) bond length is 1.54 Å. In the third P site, P(3) is bonded to one O(3), one O(4), one O(5), and one O(8) atom to form PO4 tetrahedra that share corners with two equivalent Cr(1)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra, and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 43-47°. The P(3)-O(3) bond length is 1.59 Å. The P(3)-O(4) bond length is 1.51 Å. The P(3)-O(5) bond length is 1.51 Å. The P(3)-O(8) bond length is 1.61 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Cr(1) and one P(2) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Cr(1) and one P(2) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one P(2) and one P(3) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one Cr(1) and one P(3) atom. In the fifth O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Cr(1) and one P(3) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Cr(1) and one P(2) atom. In the seventh O site, O(7) is bonded in a distorted bent 150 degrees geometry to one Cr(1) and one P(1) atom. In the eighth O site, O(8) is bonded in a bent 120 degrees geometry to one P(1) and one P(3) atom.