MgCr2Fe3Ni(PO4)6 crystallizes in the trigonal R3 space group. Mg(1) is bonded to three equivalent O(1) and three equivalent O(4) atoms to form MgO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, and  a faceface with one Cr(2)O6 octahedra. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to three equivalent O(2) and three equivalent O(6) atoms to form distorted CrO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra,  a faceface with one Fe(1)O6 octahedra, and  a faceface with one Ni(1)O6 octahedra. In the second Cr site, Cr(2) is bonded to three equivalent O(4) and three equivalent O(7) atoms to form distorted CrO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, and  a faceface with one Mg(1)O6 octahedra. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to three equivalent O(2) and three equivalent O(5) atoms to form FeO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, and  a faceface with one Cr(1)O6 octahedra. In the second Fe site, Fe(2) is bonded in a 6-coordinate geometry to three equivalent O(1) and three equivalent O(5) atoms. In the third Fe site, Fe(3) is bonded in a 6-coordinate geometry to three equivalent O(7) and three equivalent O(8) atoms. Ni(1) is bonded to three equivalent O(3) and three equivalent O(6) atoms to form distorted NiO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, and  a faceface with one Cr(1)O6 octahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(2), one O(3), one O(4), and one O(8) atom to form PO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Cr(1)O6 octahedra,  a cornercorner with one Cr(2)O6 octahedra,  a cornercorner with one Fe(1)O6 octahedra, and  a cornercorner with one Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 27-57°. In the second P site, P(2) is bonded to one O(1), one O(5), one O(6), and one O(7) atom to form PO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Cr(1)O6 octahedra,  a cornercorner with one Cr(2)O6 octahedra,  a cornercorner with one Fe(1)O6 octahedra, and  a cornercorner with one Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 9-55°. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to one Mg(1), one Fe(2), and one P(2) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Cr(1), one Fe(1), and one P(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Ni(1) and one P(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Mg(1), one Cr(2), and one P(1) atom. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Fe(1), one Fe(2), and one P(2) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Cr(1), one Ni(1), and one P(2) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Cr(2), one Fe(3), and one P(2) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Fe(3) and one P(1) atom.
MgCr2Fe3Ni(PO4)6 crystallizes in the trigonal R3 space group. Mg(1) is bonded to three equivalent O(1) and three equivalent O(4) atoms to form MgO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, and  a faceface with one Cr(2)O6 octahedra. All Mg(1)-O(1) bond lengths are 2.10 Å. All Mg(1)-O(4) bond lengths are 2.02 Å. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to three equivalent O(2) and three equivalent O(6) atoms to form distorted CrO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra,  a faceface with one Fe(1)O6 octahedra, and  a faceface with one Ni(1)O6 octahedra. All Cr(1)-O(2) bond lengths are 2.12 Å. All Cr(1)-O(6) bond lengths are 2.06 Å. In the second Cr site, Cr(2) is bonded to three equivalent O(4) and three equivalent O(7) atoms to form distorted CrO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, and  a faceface with one Mg(1)O6 octahedra. All Cr(2)-O(4) bond lengths are 2.10 Å. All Cr(2)-O(7) bond lengths are 2.10 Å. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to three equivalent O(2) and three equivalent O(5) atoms to form FeO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, and  a faceface with one Cr(1)O6 octahedra. All Fe(1)-O(2) bond lengths are 2.04 Å. All Fe(1)-O(5) bond lengths are 2.16 Å. In the second Fe site, Fe(2) is bonded in a 6-coordinate geometry to three equivalent O(1) and three equivalent O(5) atoms. All Fe(2)-O(1) bond lengths are 2.05 Å. All Fe(2)-O(5) bond lengths are 2.01 Å. In the third Fe site, Fe(3) is bonded in a 6-coordinate geometry to three equivalent O(7) and three equivalent O(8) atoms. All Fe(3)-O(7) bond lengths are 2.18 Å. All Fe(3)-O(8) bond lengths are 1.91 Å. Ni(1) is bonded to three equivalent O(3) and three equivalent O(6) atoms to form distorted NiO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, and  a faceface with one Cr(1)O6 octahedra. All Ni(1)-O(3) bond lengths are 1.98 Å. All Ni(1)-O(6) bond lengths are 2.18 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(2), one O(3), one O(4), and one O(8) atom to form PO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Cr(1)O6 octahedra,  a cornercorner with one Cr(2)O6 octahedra,  a cornercorner with one Fe(1)O6 octahedra, and  a cornercorner with one Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 27-57°. The P(1)-O(2) bond length is 1.60 Å. The P(1)-O(3) bond length is 1.50 Å. The P(1)-O(4) bond length is 1.58 Å. The P(1)-O(8) bond length is 1.54 Å. In the second P site, P(2) is bonded to one O(1), one O(5), one O(6), and one O(7) atom to form PO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Cr(1)O6 octahedra,  a cornercorner with one Cr(2)O6 octahedra,  a cornercorner with one Fe(1)O6 octahedra, and  a cornercorner with one Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 9-55°. The P(2)-O(1) bond length is 1.56 Å. The P(2)-O(5) bond length is 1.56 Å. The P(2)-O(6) bond length is 1.54 Å. The P(2)-O(7) bond length is 1.56 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to one Mg(1), one Fe(2), and one P(2) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Cr(1), one Fe(1), and one P(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Ni(1) and one P(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Mg(1), one Cr(2), and one P(1) atom. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Fe(1), one Fe(2), and one P(2) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Cr(1), one Ni(1), and one P(2) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Cr(2), one Fe(3), and one P(2) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Fe(3) and one P(1) atom.