Mg2Cr5(PO4)6 crystallizes in the triclinic P-1 space group. Mg(1) is bonded to one O(10), one O(11), one O(2), one O(3), and one O(9) atom to form MgO5 trigonal bipyramids that share  a cornercorner with one Cr(3)O6 octahedra,  a cornercorner with one P(2)O4 tetrahedra, corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(3)O4 tetrahedra,  an edgeedge with one Cr(1)O6 octahedra, and  an edgeedge with one Cr(2)O6 octahedra. The corner-sharing octahedral tilt angles are 64°. There are three inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(11), one O(12), one O(3), one O(7), and two equivalent O(5) atoms to form CrO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, corners with two equivalent P(3)O4 tetrahedra,  an edgeedge with one Cr(1)O6 octahedra, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. In the second Cr site, Cr(2) is bonded to one O(1), one O(10), one O(4), one O(9), and two equivalent O(8) atoms to form CrO6 octahedra that share  a cornercorner with one Cr(3)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra, corners with two equivalent P(3)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra,  an edgeedge with one Cr(2)O6 octahedra, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 65°. 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 CrO6 octahedra that share corners with two equivalent Cr(2)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, corners with two equivalent P(3)O4 tetrahedra, and corners with two equivalent Mg(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 65°. There are three inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(12), one O(2), and one O(3) atom to form PO4 tetrahedra that share  a cornercorner with one Cr(2)O6 octahedra,  a cornercorner with one Cr(3)O6 octahedra, corners with two equivalent Cr(1)O6 octahedra, and corners with two equivalent Mg(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 27-61°. In the second P site, P(2) is bonded to one O(5), one O(6), one O(8), and one O(9) atom to form PO4 tetrahedra that share  a cornercorner with one Cr(3)O6 octahedra, corners with two equivalent Cr(1)O6 octahedra, corners with three equivalent Cr(2)O6 octahedra, and  a cornercorner with one Mg(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 25-55°. In the third P site, P(3) is bonded to one O(10), one O(11), one O(4), and one O(7) atom to form PO4 tetrahedra that share  a cornercorner with one Cr(3)O6 octahedra, corners with two equivalent Cr(1)O6 octahedra, corners with two equivalent Cr(2)O6 octahedra, and corners with two equivalent Mg(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 34-61°. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Cr(2) and one P(1) atom. In the second O site, O(2) is bonded in a trigonal planar geometry to one Mg(1), one Cr(3), and one P(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Mg(1), one Cr(1), and one P(1) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Cr(2), one Cr(3), and one P(3) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to two equivalent Cr(1) and one P(2) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Cr(3) and one P(2) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Cr(1) and one P(3) atom. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to two equivalent Cr(2) and one P(2) atom. In the ninth O site, O(9) is bonded in a distorted trigonal planar geometry to one Mg(1), one Cr(2), and one P(2) atom. In the tenth O site, O(10) is bonded in a distorted trigonal planar geometry to one Mg(1), one Cr(2), and one P(3) atom. In the eleventh O site, O(11) is bonded in a distorted trigonal planar geometry to one Mg(1), one Cr(1), and one P(3) atom. In the twelfth O site, O(12) is bonded in a bent 150 degrees geometry to one Cr(1) and one P(1) atom.
Mg2Cr5(PO4)6 crystallizes in the triclinic P-1 space group. Mg(1) is bonded to one O(10), one O(11), one O(2), one O(3), and one O(9) atom to form MgO5 trigonal bipyramids that share  a cornercorner with one Cr(3)O6 octahedra,  a cornercorner with one P(2)O4 tetrahedra, corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(3)O4 tetrahedra,  an edgeedge with one Cr(1)O6 octahedra, and  an edgeedge with one Cr(2)O6 octahedra. The corner-sharing octahedral tilt angles are 64°. The Mg(1)-O(10) bond length is 2.04 Å. The Mg(1)-O(11) bond length is 2.09 Å. The Mg(1)-O(2) bond length is 2.01 Å. The Mg(1)-O(3) bond length is 2.08 Å. The Mg(1)-O(9) bond length is 2.07 Å. There are three inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(11), one O(12), one O(3), one O(7), and two equivalent O(5) atoms to form CrO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, corners with two equivalent P(3)O4 tetrahedra,  an edgeedge with one Cr(1)O6 octahedra, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. The Cr(1)-O(11) bond length is 2.01 Å. The Cr(1)-O(12) bond length is 1.94 Å. The Cr(1)-O(3) bond length is 2.07 Å. The Cr(1)-O(7) bond length is 1.96 Å. There is one shorter (2.06 Å) and one longer (2.15 Å) Cr(1)-O(5) bond length. In the second Cr site, Cr(2) is bonded to one O(1), one O(10), one O(4), one O(9), and two equivalent O(8) atoms to form CrO6 octahedra that share  a cornercorner with one Cr(3)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra, corners with two equivalent P(3)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra,  an edgeedge with one Cr(2)O6 octahedra, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 65°. The Cr(2)-O(1) bond length is 1.94 Å. The Cr(2)-O(10) bond length is 2.08 Å. The Cr(2)-O(4) bond length is 2.06 Å. The Cr(2)-O(9) bond length is 2.04 Å. There is one shorter (2.04 Å) and one longer (2.05 Å) Cr(2)-O(8) bond length. 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 CrO6 octahedra that share corners with two equivalent Cr(2)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, corners with two equivalent P(3)O4 tetrahedra, and corners with two equivalent Mg(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 65°. Both Cr(3)-O(2) bond lengths are 2.29 Å. Both Cr(3)-O(4) bond lengths are 2.27 Å. Both Cr(3)-O(6) bond lengths are 2.05 Å. There are three inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(12), one O(2), and one O(3) atom to form PO4 tetrahedra that share  a cornercorner with one Cr(2)O6 octahedra,  a cornercorner with one Cr(3)O6 octahedra, corners with two equivalent Cr(1)O6 octahedra, and corners with two equivalent Mg(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 27-61°. The P(1)-O(1) bond length is 1.53 Å. The P(1)-O(12) bond length is 1.53 Å. The P(1)-O(2) bond length is 1.56 Å. The P(1)-O(3) bond length is 1.59 Å. In the second P site, P(2) is bonded to one O(5), one O(6), one O(8), and one O(9) atom to form PO4 tetrahedra that share  a cornercorner with one Cr(3)O6 octahedra, corners with two equivalent Cr(1)O6 octahedra, corners with three equivalent Cr(2)O6 octahedra, and  a cornercorner with one Mg(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 25-55°. The P(2)-O(5) bond length is 1.57 Å. The P(2)-O(6) bond length is 1.50 Å. The P(2)-O(8) bond length is 1.58 Å. The P(2)-O(9) bond length is 1.57 Å. In the third P site, P(3) is bonded to one O(10), one O(11), one O(4), and one O(7) atom to form PO4 tetrahedra that share  a cornercorner with one Cr(3)O6 octahedra, corners with two equivalent Cr(1)O6 octahedra, corners with two equivalent Cr(2)O6 octahedra, and corners with two equivalent Mg(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 34-61°. The P(3)-O(10) bond length is 1.57 Å. The P(3)-O(11) bond length is 1.57 Å. The P(3)-O(4) bond length is 1.57 Å. The P(3)-O(7) bond length is 1.51 Å. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Cr(2) and one P(1) atom. In the second O site, O(2) is bonded in a trigonal planar geometry to one Mg(1), one Cr(3), and one P(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Mg(1), one Cr(1), and one P(1) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Cr(2), one Cr(3), and one P(3) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to two equivalent Cr(1) and one P(2) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Cr(3) and one P(2) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Cr(1) and one P(3) atom. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to two equivalent Cr(2) and one P(2) atom. In the ninth O site, O(9) is bonded in a distorted trigonal planar geometry to one Mg(1), one Cr(2), and one P(2) atom. In the tenth O site, O(10) is bonded in a distorted trigonal planar geometry to one Mg(1), one Cr(2), and one P(3) atom. In the eleventh O site, O(11) is bonded in a distorted trigonal planar geometry to one Mg(1), one Cr(1), and one P(3) atom. In the twelfth O site, O(12) is bonded in a bent 150 degrees geometry to one Cr(1) and one P(1) atom.