Cr4(PO4)3 crystallizes in the monoclinic C2/c space group. There are three inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(1), one O(2), one O(3), one O(4), and two equivalent O(5) atoms to form CrO6 octahedra that share corners with two equivalent P(2)O4 tetrahedra, corners with four equivalent P(1)O4 tetrahedra,  an edgeedge with one Cr(1)O6 octahedra, and  an edgeedge with one Cr(3)O6 octahedra. In the second Cr site, Cr(2) is bonded in a rectangular see-saw-like geometry to two equivalent O(3) and two equivalent O(6) atoms. In the third Cr site, Cr(3) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(6) atoms to form distorted CrO6 octahedra that share corners with two equivalent P(2)O4 tetrahedra, corners with four equivalent P(1)O4 tetrahedra, and edges with two equivalent Cr(1)O6 octahedra. 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 corners with two equivalent Cr(3)O6 octahedra and corners with four equivalent Cr(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 26-57°. In the second P site, P(2) is bonded to two equivalent O(3) and two equivalent O(4) atoms to form PO4 tetrahedra that share corners with two equivalent Cr(3)O6 octahedra and corners with four equivalent Cr(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 53-58°. There are six inequivalent O sites. In the first O site, O(5) is bonded in a 3-coordinate geometry to two equivalent Cr(1) and one P(1) atom. In the second O site, O(6) is bonded in a distorted trigonal planar geometry to one Cr(2), one Cr(3), and one P(1) atom. In the third O site, O(1) is bonded in a bent 150 degrees geometry to one Cr(1) and one P(1) atom. In the fourth O site, O(2) is bonded in a distorted trigonal planar geometry to one Cr(1), one Cr(3), and one P(1) atom. In the fifth O site, O(3) is bonded in a distorted trigonal planar geometry to one Cr(1), one Cr(2), and one P(2) atom. In the sixth O site, O(4) is bonded in a distorted trigonal planar geometry to one Cr(1), one Cr(3), and one P(2) atom.
Cr4(PO4)3 crystallizes in the monoclinic C2/c space group. There are three inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(1), one O(2), one O(3), one O(4), and two equivalent O(5) atoms to form CrO6 octahedra that share corners with two equivalent P(2)O4 tetrahedra, corners with four equivalent P(1)O4 tetrahedra,  an edgeedge with one Cr(1)O6 octahedra, and  an edgeedge with one Cr(3)O6 octahedra. The Cr(1)-O(1) bond length is 2.00 Å. The Cr(1)-O(2) bond length is 2.19 Å. The Cr(1)-O(3) bond length is 2.06 Å. The Cr(1)-O(4) bond length is 2.07 Å. There is one shorter (2.09 Å) and one longer (2.29 Å) Cr(1)-O(5) bond length. In the second Cr site, Cr(2) is bonded in a rectangular see-saw-like geometry to two equivalent O(3) and two equivalent O(6) atoms. Both Cr(2)-O(3) bond lengths are 2.05 Å. Both Cr(2)-O(6) bond lengths are 2.02 Å. In the third Cr site, Cr(3) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(6) atoms to form distorted CrO6 octahedra that share corners with two equivalent P(2)O4 tetrahedra, corners with four equivalent P(1)O4 tetrahedra, and edges with two equivalent Cr(1)O6 octahedra. Both Cr(3)-O(2) bond lengths are 2.16 Å. Both Cr(3)-O(4) bond lengths are 2.35 Å. Both Cr(3)-O(6) bond lengths are 2.14 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 corners with two equivalent Cr(3)O6 octahedra and corners with four equivalent Cr(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 26-57°. The P(1)-O(1) bond length is 1.51 Å. The P(1)-O(2) bond length is 1.56 Å. The P(1)-O(5) bond length is 1.57 Å. The P(1)-O(6) bond length is 1.59 Å. In the second P site, P(2) is bonded to two equivalent O(3) and two equivalent O(4) atoms to form PO4 tetrahedra that share corners with two equivalent Cr(3)O6 octahedra and corners with four equivalent Cr(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 53-58°. Both P(2)-O(3) bond lengths are 1.59 Å. Both P(2)-O(4) bond lengths are 1.53 Å. There are six inequivalent O sites. In the first O site, O(5) is bonded in a 3-coordinate geometry to two equivalent Cr(1) and one P(1) atom. In the second O site, O(6) is bonded in a distorted trigonal planar geometry to one Cr(2), one Cr(3), and one P(1) atom. In the third O site, O(1) is bonded in a bent 150 degrees geometry to one Cr(1) and one P(1) atom. In the fourth O site, O(2) is bonded in a distorted trigonal planar geometry to one Cr(1), one Cr(3), and one P(1) atom. In the fifth O site, O(3) is bonded in a distorted trigonal planar geometry to one Cr(1), one Cr(2), and one P(2) atom. In the sixth O site, O(4) is bonded in a distorted trigonal planar geometry to one Cr(1), one Cr(3), and one P(2) atom.