MgMnP2O7 crystallizes in the triclinic P-1 space group. Mg(1) is bonded to one O(2), one O(3), one O(4), and two equivalent O(5) atoms to form MgO5 trigonal bipyramids that share corners with two equivalent Mn(1)O5 square pyramids, corners with two equivalent P(2)O4 tetrahedra, corners with three equivalent P(1)O4 tetrahedra, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. Mn(1) is bonded to one O(2), one O(4), one O(7), and two equivalent O(6) atoms to form distorted MnO5 square pyramids that share corners with two equivalent P(2)O4 tetrahedra, corners with three equivalent P(1)O4 tetrahedra, corners with two equivalent Mg(1)O5 trigonal bipyramids, and  an edgeedge with one Mn(1)O5 square pyramid. 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 three equivalent Mn(1)O5 square pyramids,  a cornercorner with one P(2)O4 tetrahedra, and corners with three equivalent Mg(1)O5 trigonal bipyramids. In the second P site, P(2) is bonded to one O(1), one O(3), one O(4), and one O(7) atom to form PO4 tetrahedra that share corners with two equivalent Mn(1)O5 square pyramids,  a cornercorner with one P(1)O4 tetrahedra, and corners with two equivalent Mg(1)O5 trigonal bipyramids. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 120 degrees geometry to one P(1) and one P(2) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mn(1), and one P(1) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Mg(1) and one P(2) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mn(1), and one P(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to two equivalent Mg(1) and one P(1) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to two equivalent Mn(1) and one P(1) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Mn(1) and one P(2) atom.
MgMnP2O7 crystallizes in the triclinic P-1 space group. Mg(1) is bonded to one O(2), one O(3), one O(4), and two equivalent O(5) atoms to form MgO5 trigonal bipyramids that share corners with two equivalent Mn(1)O5 square pyramids, corners with two equivalent P(2)O4 tetrahedra, corners with three equivalent P(1)O4 tetrahedra, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. The Mg(1)-O(2) bond length is 2.17 Å. The Mg(1)-O(3) bond length is 2.02 Å. The Mg(1)-O(4) bond length is 2.12 Å. Both Mg(1)-O(5) bond lengths are 2.10 Å. Mn(1) is bonded to one O(2), one O(4), one O(7), and two equivalent O(6) atoms to form distorted MnO5 square pyramids that share corners with two equivalent P(2)O4 tetrahedra, corners with three equivalent P(1)O4 tetrahedra, corners with two equivalent Mg(1)O5 trigonal bipyramids, and  an edgeedge with one Mn(1)O5 square pyramid. The Mn(1)-O(2) bond length is 2.29 Å. The Mn(1)-O(4) bond length is 2.15 Å. The Mn(1)-O(7) bond length is 2.03 Å. There is one shorter (2.15 Å) and one longer (2.26 Å) Mn(1)-O(6) bond length. 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 three equivalent Mn(1)O5 square pyramids,  a cornercorner with one P(2)O4 tetrahedra, and corners with three equivalent Mg(1)O5 trigonal bipyramids. The P(1)-O(1) bond length is 1.60 Å. The P(1)-O(2) bond length is 1.55 Å. The P(1)-O(5) bond length is 1.54 Å. The P(1)-O(6) bond length is 1.53 Å. In the second P site, P(2) is bonded to one O(1), one O(3), one O(4), and one O(7) atom to form PO4 tetrahedra that share corners with two equivalent Mn(1)O5 square pyramids,  a cornercorner with one P(1)O4 tetrahedra, and corners with two equivalent Mg(1)O5 trigonal bipyramids. The P(2)-O(1) bond length is 1.65 Å. The P(2)-O(3) bond length is 1.52 Å. The P(2)-O(4) bond length is 1.55 Å. The P(2)-O(7) bond length is 1.51 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 120 degrees geometry to one P(1) and one P(2) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mn(1), and one P(1) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Mg(1) and one P(2) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mn(1), and one P(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to two equivalent Mg(1) and one P(1) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to two equivalent Mn(1) and one P(1) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Mn(1) and one P(2) atom.