MgCrP2O7 crystallizes in the monoclinic C2 space group. Mg(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted MgO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra and edges with two equivalent P(1)O4 tetrahedra. Cr(1) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(3) atoms. P(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form PO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra, and  an edgeedge with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles are 56°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Mg(1), one Cr(1), and one P(1) atom. In the second O site, O(2) is bonded in an L-shaped geometry to one Mg(1) and one P(1) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Mg(1), one Cr(1), and one P(1) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to two equivalent P(1) atoms.
MgCrP2O7 crystallizes in the monoclinic C2 space group. Mg(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted MgO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra and edges with two equivalent P(1)O4 tetrahedra. Both Mg(1)-O(1) bond lengths are 2.03 Å. Both Mg(1)-O(2) bond lengths are 2.02 Å. Both Mg(1)-O(3) bond lengths are 2.21 Å. Cr(1) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(3) atoms. Both Cr(1)-O(1) bond lengths are 2.10 Å. Both Cr(1)-O(3) bond lengths are 2.08 Å. P(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form PO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra, and  an edgeedge with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles are 56°. The P(1)-O(1) bond length is 1.55 Å. The P(1)-O(2) bond length is 1.51 Å. The P(1)-O(3) bond length is 1.56 Å. The P(1)-O(4) bond length is 1.63 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Mg(1), one Cr(1), and one P(1) atom. In the second O site, O(2) is bonded in an L-shaped geometry to one Mg(1) and one P(1) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Mg(1), one Cr(1), and one P(1) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to two equivalent P(1) atoms.