MnFe2(PO9)2 crystallizes in the triclinic P-1 space group. Mn(1) is bonded to two equivalent O(1), two equivalent O(6), and two equivalent O(7) atoms to form distorted MnO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(3), two equivalent O(5), and two equivalent O(9) atoms to form FeO6 octahedra that share corners with two equivalent Fe(2)O6 octahedra and corners with two equivalent P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 40°. In the second Fe site, Fe(2) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(9) atoms to form FeO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra and corners with four equivalent P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 40°. 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 Mn(1)O6 octahedra,  a cornercorner with one Fe(1)O6 octahedra, and corners with two equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 30-48°. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Mn(1) and one P(1) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Fe(2) and one P(1) atom. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to one Fe(1) and one P(1) atom. In the fourth O site, O(4) is bonded in a distorted bent 120 degrees geometry to one Fe(2) and one P(1) atom. In the fifth O site, O(5) is bonded in a single-bond geometry to one Fe(1) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Mn(1) and one O(8) atom. In the seventh O site, O(7) is bonded in a single-bond geometry to one Mn(1) atom. In the eighth O site, O(8) is bonded in a single-bond geometry to one O(6) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Fe(1) and one Fe(2) atom.
MnFe2(PO9)2 crystallizes in the triclinic P-1 space group. Mn(1) is bonded to two equivalent O(1), two equivalent O(6), and two equivalent O(7) atoms to form distorted MnO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra. Both Mn(1)-O(1) bond lengths are 1.96 Å. Both Mn(1)-O(6) bond lengths are 2.47 Å. Both Mn(1)-O(7) bond lengths are 1.65 Å. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(3), two equivalent O(5), and two equivalent O(9) atoms to form FeO6 octahedra that share corners with two equivalent Fe(2)O6 octahedra and corners with two equivalent P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 40°. Both Fe(1)-O(3) bond lengths are 1.91 Å. Both Fe(1)-O(5) bond lengths are 1.82 Å. Both Fe(1)-O(9) bond lengths are 1.82 Å. In the second Fe site, Fe(2) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(9) atoms to form FeO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra and corners with four equivalent P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 40°. Both Fe(2)-O(2) bond lengths are 2.00 Å. Both Fe(2)-O(4) bond lengths are 1.99 Å. Both Fe(2)-O(9) bond lengths are 2.03 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 Mn(1)O6 octahedra,  a cornercorner with one Fe(1)O6 octahedra, and corners with two equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 30-48°. The P(1)-O(1) bond length is 1.53 Å. The P(1)-O(2) bond length is 1.53 Å. The P(1)-O(3) bond length is 1.59 Å. The P(1)-O(4) bond length is 1.53 Å. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Mn(1) and one P(1) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Fe(2) and one P(1) atom. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to one Fe(1) and one P(1) atom. In the fourth O site, O(4) is bonded in a distorted bent 120 degrees geometry to one Fe(2) and one P(1) atom. In the fifth O site, O(5) is bonded in a single-bond geometry to one Fe(1) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Mn(1) and one O(8) atom. The O(6)-O(8) bond length is 1.23 Å. In the seventh O site, O(7) is bonded in a single-bond geometry to one Mn(1) atom. In the eighth O site, O(8) is bonded in a single-bond geometry to one O(6) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Fe(1) and one Fe(2) atom.