MgFe4(PO4)4 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(11), one O(2), one O(5), one O(7), and one O(8) atom to form distorted MgO5 trigonal bipyramids that share  a cornercorner with one Fe(1)O4 tetrahedra,  a cornercorner with one P(2)O4 tetrahedra, corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent Fe(4)O4 trigonal pyramids, and  an edgeedge with one P(4)O4 tetrahedra. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(10), one O(13), one O(2), and one O(3) atom to form FeO4 tetrahedra that share  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one P(3)O4 tetrahedra, corners with two equivalent P(4)O4 tetrahedra, and  a cornercorner with one Mg(1)O5 trigonal bipyramid. In the second Fe site, Fe(2) is bonded to one O(1), one O(14), one O(15), and one O(4) atom to form FeO4 tetrahedra that share  a cornercorner with one P(2)O4 tetrahedra,  a cornercorner with one P(4)O4 tetrahedra, and corners with two equivalent P(3)O4 tetrahedra. In the third Fe site, Fe(3) is bonded in a distorted rectangular see-saw-like geometry to one O(11), one O(12), one O(16), and one O(8) atom. In the fourth Fe site, Fe(4) is bonded to one O(5), one O(6), one O(7), and one O(9) atom to form FeO4 trigonal pyramids that share  a cornercorner with one P(2)O4 tetrahedra,  a cornercorner with one P(4)O4 tetrahedra, corners with two equivalent P(1)O4 tetrahedra, and corners with two equivalent Mg(1)O5 trigonal bipyramids. There are four inequivalent P sites. In the first P site, P(1) is bonded to one O(13), one O(6), one O(7), and one O(8) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(1)O4 tetrahedra, corners with two equivalent Mg(1)O5 trigonal bipyramids, and corners with two equivalent Fe(4)O4 trigonal pyramids. In the second P site, P(2) is bonded to one O(1), one O(11), one O(16), and one O(9) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(2)O4 tetrahedra,  a cornercorner with one Mg(1)O5 trigonal bipyramid, and  a cornercorner with one Fe(4)O4 trigonal pyramid. In the third P site, P(3) is bonded to one O(10), one O(12), one O(14), and one O(15) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(1)O4 tetrahedra and corners with two equivalent Fe(2)O4 tetrahedra. In the fourth P site, P(4) is bonded to one O(2), one O(3), one O(4), and one O(5) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(2)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra,  a cornercorner with one Fe(4)O4 trigonal pyramid, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. There are sixteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Fe(2) 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 Fe(1), and one P(4) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Fe(1) and one P(4) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Fe(2) and one P(4) atom. In the fifth O site, O(5) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1), one Fe(4), and one P(4) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Fe(4) and one P(1) atom. In the seventh O site, O(7) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1), one Fe(4), and one P(1) atom. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Mg(1), one Fe(3), and one P(1) atom. In the ninth O site, O(9) is bonded in a bent 120 degrees geometry to one Fe(4) and one P(2) atom. In the tenth O site, O(10) is bonded in a bent 120 degrees geometry to one Fe(1) and one P(3) atom. In the eleventh O site, O(11) is bonded in a 3-coordinate geometry to one Mg(1), one Fe(3), and one P(2) atom. In the twelfth O site, O(12) is bonded in a distorted bent 120 degrees geometry to one Fe(3) and one P(3) atom. In the thirteenth O site, O(13) is bonded in a bent 120 degrees geometry to one Fe(1) and one P(1) atom. In the fourteenth O site, O(14) is bonded in a distorted bent 150 degrees geometry to one Fe(2) and one P(3) atom. In the fifteenth O site, O(15) is bonded in a bent 150 degrees geometry to one Fe(2) and one P(3) atom. In the sixteenth O site, O(16) is bonded in a bent 150 degrees geometry to one Fe(3) and one P(2) atom.
MgFe4(PO4)4 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(11), one O(2), one O(5), one O(7), and one O(8) atom to form distorted MgO5 trigonal bipyramids that share  a cornercorner with one Fe(1)O4 tetrahedra,  a cornercorner with one P(2)O4 tetrahedra, corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent Fe(4)O4 trigonal pyramids, and  an edgeedge with one P(4)O4 tetrahedra. The Mg(1)-O(11) bond length is 2.04 Å. The Mg(1)-O(2) bond length is 2.24 Å. The Mg(1)-O(5) bond length is 2.11 Å. The Mg(1)-O(7) bond length is 2.13 Å. The Mg(1)-O(8) bond length is 2.18 Å. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(10), one O(13), one O(2), and one O(3) atom to form FeO4 tetrahedra that share  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one P(3)O4 tetrahedra, corners with two equivalent P(4)O4 tetrahedra, and  a cornercorner with one Mg(1)O5 trigonal bipyramid. The Fe(1)-O(10) bond length is 1.90 Å. The Fe(1)-O(13) bond length is 1.88 Å. The Fe(1)-O(2) bond length is 1.94 Å. The Fe(1)-O(3) bond length is 1.89 Å. In the second Fe site, Fe(2) is bonded to one O(1), one O(14), one O(15), and one O(4) atom to form FeO4 tetrahedra that share  a cornercorner with one P(2)O4 tetrahedra,  a cornercorner with one P(4)O4 tetrahedra, and corners with two equivalent P(3)O4 tetrahedra. The Fe(2)-O(1) bond length is 1.88 Å. The Fe(2)-O(14) bond length is 1.89 Å. The Fe(2)-O(15) bond length is 1.88 Å. The Fe(2)-O(4) bond length is 1.90 Å. In the third Fe site, Fe(3) is bonded in a distorted rectangular see-saw-like geometry to one O(11), one O(12), one O(16), and one O(8) atom. The Fe(3)-O(11) bond length is 2.13 Å. The Fe(3)-O(12) bond length is 1.93 Å. The Fe(3)-O(16) bond length is 1.95 Å. The Fe(3)-O(8) bond length is 2.12 Å. In the fourth Fe site, Fe(4) is bonded to one O(5), one O(6), one O(7), and one O(9) atom to form FeO4 trigonal pyramids that share  a cornercorner with one P(2)O4 tetrahedra,  a cornercorner with one P(4)O4 tetrahedra, corners with two equivalent P(1)O4 tetrahedra, and corners with two equivalent Mg(1)O5 trigonal bipyramids. The Fe(4)-O(5) bond length is 2.13 Å. The Fe(4)-O(6) bond length is 1.95 Å. The Fe(4)-O(7) bond length is 2.08 Å. The Fe(4)-O(9) bond length is 1.97 Å. There are four inequivalent P sites. In the first P site, P(1) is bonded to one O(13), one O(6), one O(7), and one O(8) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(1)O4 tetrahedra, corners with two equivalent Mg(1)O5 trigonal bipyramids, and corners with two equivalent Fe(4)O4 trigonal pyramids. The P(1)-O(13) bond length is 1.56 Å. The P(1)-O(6) bond length is 1.53 Å. The P(1)-O(7) bond length is 1.58 Å. The P(1)-O(8) bond length is 1.56 Å. In the second P site, P(2) is bonded to one O(1), one O(11), one O(16), and one O(9) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(2)O4 tetrahedra,  a cornercorner with one Mg(1)O5 trigonal bipyramid, and  a cornercorner with one Fe(4)O4 trigonal pyramid. The P(2)-O(1) bond length is 1.57 Å. The P(2)-O(11) bond length is 1.56 Å. The P(2)-O(16) bond length is 1.54 Å. The P(2)-O(9) bond length is 1.54 Å. In the third P site, P(3) is bonded to one O(10), one O(12), one O(14), and one O(15) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(1)O4 tetrahedra and corners with two equivalent Fe(2)O4 tetrahedra. The P(3)-O(10) bond length is 1.57 Å. The P(3)-O(12) bond length is 1.52 Å. The P(3)-O(14) bond length is 1.56 Å. The P(3)-O(15) bond length is 1.55 Å. In the fourth P site, P(4) is bonded to one O(2), one O(3), one O(4), and one O(5) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(2)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra,  a cornercorner with one Fe(4)O4 trigonal pyramid, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. The P(4)-O(2) bond length is 1.59 Å. The P(4)-O(3) bond length is 1.54 Å. The P(4)-O(4) bond length is 1.53 Å. The P(4)-O(5) bond length is 1.55 Å. There are sixteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Fe(2) 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 Fe(1), and one P(4) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Fe(1) and one P(4) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Fe(2) and one P(4) atom. In the fifth O site, O(5) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1), one Fe(4), and one P(4) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Fe(4) and one P(1) atom. In the seventh O site, O(7) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1), one Fe(4), and one P(1) atom. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Mg(1), one Fe(3), and one P(1) atom. In the ninth O site, O(9) is bonded in a bent 120 degrees geometry to one Fe(4) and one P(2) atom. In the tenth O site, O(10) is bonded in a bent 120 degrees geometry to one Fe(1) and one P(3) atom. In the eleventh O site, O(11) is bonded in a 3-coordinate geometry to one Mg(1), one Fe(3), and one P(2) atom. In the twelfth O site, O(12) is bonded in a distorted bent 120 degrees geometry to one Fe(3) and one P(3) atom. In the thirteenth O site, O(13) is bonded in a bent 120 degrees geometry to one Fe(1) and one P(1) atom. In the fourteenth O site, O(14) is bonded in a distorted bent 150 degrees geometry to one Fe(2) and one P(3) atom. In the fifteenth O site, O(15) is bonded in a bent 150 degrees geometry to one Fe(2) and one P(3) atom. In the sixteenth O site, O(16) is bonded in a bent 150 degrees geometry to one Fe(3) and one P(2) atom.