Cr3(P2O7)2 crystallizes in the triclinic P-1 space group. There are four inequivalent Cr sites. In the first Cr site, Cr(1) is bonded in a 6-coordinate geometry to one O(10), one O(13), one O(14), one O(3), one O(6), and one O(9) atom. In the second Cr site, Cr(2) is bonded to one O(12), one O(14), one O(4), one O(7), one O(8), and one O(9) atom to form CrO6 octahedra that share  a cornercorner with one P(3)O4 tetrahedra,  a cornercorner with one P(4)O4 tetrahedra, corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, and  an edgeedge with one Cr(4)O6 octahedra. In the third Cr site, Cr(3) is bonded to two equivalent O(13), two equivalent O(2), and two equivalent O(6) atoms to form CrO6 octahedra that share corners with two equivalent P(2)O4 tetrahedra and corners with four equivalent P(3)O4 tetrahedra. In the fourth Cr site, Cr(4) is bonded to two equivalent O(11), two equivalent O(12), and two equivalent O(7) atoms to form CrO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with four equivalent P(4)O4 tetrahedra, and edges with two equivalent Cr(2)O6 octahedra. There are four inequivalent P sites. In the first P site, P(1) is bonded to one O(10), one O(5), one O(7), and one O(9) atom to form PO4 tetrahedra that share  a cornercorner with one Cr(4)O6 octahedra, corners with two equivalent Cr(2)O6 octahedra, and  a cornercorner with one P(4)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 43-56°. In the second P site, P(2) is bonded to one O(1), one O(13), one O(14), and one O(4) atom to form PO4 tetrahedra that share  a cornercorner with one Cr(3)O6 octahedra, corners with two equivalent Cr(2)O6 octahedra, and  a cornercorner with one P(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 25-56°. In the third P site, P(3) is bonded to one O(1), one O(2), one O(6), and one O(8) atom to form PO4 tetrahedra that share  a cornercorner with one Cr(2)O6 octahedra, corners with two equivalent Cr(3)O6 octahedra, and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 25-54°. In the fourth P site, P(4) is bonded to one O(11), one O(12), one O(3), and one O(5) atom to form PO4 tetrahedra that share  a cornercorner with one Cr(2)O6 octahedra, corners with two equivalent Cr(4)O6 octahedra, and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 41-58°. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one P(2) and one P(3) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Cr(3) and one P(3) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Cr(1) and one P(4) 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 150 degrees geometry to one P(1) and one P(4) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Cr(1), one Cr(3), and one P(3) atom. In the seventh O site, O(7) is bonded in a trigonal planar geometry to one Cr(2), one Cr(4), and one P(1) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Cr(2) and one P(3) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to one Cr(1), one Cr(2), and one P(1) atom. In the tenth O site, O(10) is bonded in a bent 150 degrees geometry to one Cr(1) and one P(1) atom. In the eleventh O site, O(11) is bonded in a bent 150 degrees geometry to one Cr(4) and one P(4) atom. In the twelfth O site, O(12) is bonded in a distorted trigonal planar geometry to one Cr(2), one Cr(4), and one P(4) atom. In the thirteenth O site, O(13) is bonded in a distorted trigonal planar geometry to one Cr(1), one Cr(3), and one P(2) atom. In the fourteenth O site, O(14) is bonded in a distorted bent 120 degrees geometry to one Cr(1), one Cr(2), and one P(2) atom.
Cr3(P2O7)2 crystallizes in the triclinic P-1 space group. There are four inequivalent Cr sites. In the first Cr site, Cr(1) is bonded in a 6-coordinate geometry to one O(10), one O(13), one O(14), one O(3), one O(6), and one O(9) atom. The Cr(1)-O(10) bond length is 2.05 Å. The Cr(1)-O(13) bond length is 2.17 Å. The Cr(1)-O(14) bond length is 2.72 Å. The Cr(1)-O(3) bond length is 1.99 Å. The Cr(1)-O(6) bond length is 2.08 Å. The Cr(1)-O(9) bond length is 2.65 Å. In the second Cr site, Cr(2) is bonded to one O(12), one O(14), one O(4), one O(7), one O(8), and one O(9) atom to form CrO6 octahedra that share  a cornercorner with one P(3)O4 tetrahedra,  a cornercorner with one P(4)O4 tetrahedra, corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, and  an edgeedge with one Cr(4)O6 octahedra. The Cr(2)-O(12) bond length is 2.10 Å. The Cr(2)-O(14) bond length is 2.06 Å. The Cr(2)-O(4) bond length is 1.97 Å. The Cr(2)-O(7) bond length is 2.07 Å. The Cr(2)-O(8) bond length is 1.98 Å. The Cr(2)-O(9) bond length is 2.05 Å. In the third Cr site, Cr(3) is bonded to two equivalent O(13), two equivalent O(2), and two equivalent O(6) atoms to form CrO6 octahedra that share corners with two equivalent P(2)O4 tetrahedra and corners with four equivalent P(3)O4 tetrahedra. Both Cr(3)-O(13) bond lengths are 2.05 Å. Both Cr(3)-O(2) bond lengths are 2.03 Å. Both Cr(3)-O(6) bond lengths are 1.98 Å. In the fourth Cr site, Cr(4) is bonded to two equivalent O(11), two equivalent O(12), and two equivalent O(7) atoms to form CrO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with four equivalent P(4)O4 tetrahedra, and edges with two equivalent Cr(2)O6 octahedra. Both Cr(4)-O(11) bond lengths are 1.97 Å. Both Cr(4)-O(12) bond lengths are 2.04 Å. Both Cr(4)-O(7) bond lengths are 2.03 Å. There are four inequivalent P sites. In the first P site, P(1) is bonded to one O(10), one O(5), one O(7), and one O(9) atom to form PO4 tetrahedra that share  a cornercorner with one Cr(4)O6 octahedra, corners with two equivalent Cr(2)O6 octahedra, and  a cornercorner with one P(4)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 43-56°. The P(1)-O(10) bond length is 1.49 Å. The P(1)-O(5) bond length is 1.61 Å. The P(1)-O(7) bond length is 1.58 Å. The P(1)-O(9) bond length is 1.53 Å. In the second P site, P(2) is bonded to one O(1), one O(13), one O(14), and one O(4) atom to form PO4 tetrahedra that share  a cornercorner with one Cr(3)O6 octahedra, corners with two equivalent Cr(2)O6 octahedra, and  a cornercorner with one P(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 25-56°. The P(2)-O(1) bond length is 1.61 Å. The P(2)-O(13) bond length is 1.57 Å. The P(2)-O(14) bond length is 1.54 Å. The P(2)-O(4) bond length is 1.51 Å. In the third P site, P(3) is bonded to one O(1), one O(2), one O(6), and one O(8) atom to form PO4 tetrahedra that share  a cornercorner with one Cr(2)O6 octahedra, corners with two equivalent Cr(3)O6 octahedra, and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 25-54°. The P(3)-O(1) bond length is 1.61 Å. The P(3)-O(2) bond length is 1.52 Å. The P(3)-O(6) bond length is 1.57 Å. The P(3)-O(8) bond length is 1.51 Å. In the fourth P site, P(4) is bonded to one O(11), one O(12), one O(3), and one O(5) atom to form PO4 tetrahedra that share  a cornercorner with one Cr(2)O6 octahedra, corners with two equivalent Cr(4)O6 octahedra, and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 41-58°. The P(4)-O(11) bond length is 1.51 Å. The P(4)-O(12) bond length is 1.59 Å. The P(4)-O(3) bond length is 1.49 Å. The P(4)-O(5) bond length is 1.61 Å. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one P(2) and one P(3) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Cr(3) and one P(3) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Cr(1) and one P(4) 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 150 degrees geometry to one P(1) and one P(4) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Cr(1), one Cr(3), and one P(3) atom. In the seventh O site, O(7) is bonded in a trigonal planar geometry to one Cr(2), one Cr(4), and one P(1) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Cr(2) and one P(3) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to one Cr(1), one Cr(2), and one P(1) atom. In the tenth O site, O(10) is bonded in a bent 150 degrees geometry to one Cr(1) and one P(1) atom. In the eleventh O site, O(11) is bonded in a bent 150 degrees geometry to one Cr(4) and one P(4) atom. In the twelfth O site, O(12) is bonded in a distorted trigonal planar geometry to one Cr(2), one Cr(4), and one P(4) atom. In the thirteenth O site, O(13) is bonded in a distorted trigonal planar geometry to one Cr(1), one Cr(3), and one P(2) atom. In the fourteenth O site, O(14) is bonded in a distorted bent 120 degrees geometry to one Cr(1), one Cr(2), and one P(2) atom.