MgFe4(PO4)4 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(13), one O(15), one O(2), and one O(4) atom to form MgO4 tetrahedra that share  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one P(3)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra, corners with two equivalent P(4)O4 tetrahedra, and corners with two equivalent Fe(2)O4 trigonal pyramids. 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 Mg(1)O4 tetrahedra, and corners with two equivalent P(4)O4 tetrahedra. 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 trigonal pyramids that share  a cornercorner with one P(2)O4 tetrahedra,  a cornercorner with one P(4)O4 tetrahedra, corners with two equivalent Mg(1)O4 tetrahedra, and corners with two equivalent P(3)O4 tetrahedra. In the third Fe site, Fe(3) is bonded to one O(11), one O(12), one O(16), and one O(8) atom to form FeO4 tetrahedra that share  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one P(3)O4 tetrahedra, and corners with two equivalent P(2)O4 tetrahedra. 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 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(1)O4 tetrahedra. 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 Mg(1)O4 tetrahedra,  a cornercorner with one Fe(1)O4 tetrahedra,  a cornercorner with one Fe(3)O4 tetrahedra, and corners with two equivalent Fe(4)O4 tetrahedra. 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(4)O4 tetrahedra, corners with two equivalent Fe(3)O4 tetrahedra, and  a cornercorner with one Fe(2)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 Mg(1)O4 tetrahedra,  a cornercorner with one Fe(1)O4 tetrahedra,  a cornercorner with one Fe(3)O4 tetrahedra, and corners with two equivalent Fe(2)O4 trigonal pyramids. 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(4)O4 tetrahedra, corners with two equivalent Mg(1)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra, and  a cornercorner with one Fe(2)O4 trigonal pyramid. There are sixteen inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to one Fe(2) and one P(2) atom. In the second O site, O(2) is bonded in a 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 120 degrees geometry to one Fe(1) and one P(4) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Mg(1), one Fe(2), and one P(4) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Fe(4) and one P(4) atom. In the sixth O site, O(6) is bonded in a distorted bent 150 degrees geometry to one Fe(4) and one P(1) atom. In the seventh O site, O(7) is bonded in a distorted bent 120 degrees geometry to one Fe(4) and one P(1) atom. In the eighth O site, O(8) is bonded in a distorted bent 120 degrees geometry to 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 bent 150 degrees geometry to one Fe(3) and one P(2) atom. In the twelfth O site, O(12) is bonded in a bent 120 degrees geometry to one Fe(3) and one P(3) atom. In the thirteenth O site, O(13) is bonded in a trigonal planar geometry to one Mg(1), one Fe(1), and one P(1) atom. In the fourteenth O site, O(14) is bonded in a bent 120 degrees geometry to one Fe(2) and one P(3) atom. In the fifteenth O site, O(15) is bonded in a trigonal planar geometry to one Mg(1), 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(13), one O(15), one O(2), and one O(4) atom to form MgO4 tetrahedra that share  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one P(3)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra, corners with two equivalent P(4)O4 tetrahedra, and corners with two equivalent Fe(2)O4 trigonal pyramids. The Mg(1)-O(13) bond length is 2.07 Å. The Mg(1)-O(15) bond length is 1.99 Å. The Mg(1)-O(2) bond length is 2.04 Å. The Mg(1)-O(4) bond length is 2.00 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 Mg(1)O4 tetrahedra, and corners with two equivalent P(4)O4 tetrahedra. The Fe(1)-O(10) bond length is 1.96 Å. The Fe(1)-O(13) bond length is 2.15 Å. The Fe(1)-O(2) bond length is 2.16 Å. The Fe(1)-O(3) bond length is 2.00 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 trigonal pyramids that share  a cornercorner with one P(2)O4 tetrahedra,  a cornercorner with one P(4)O4 tetrahedra, corners with two equivalent Mg(1)O4 tetrahedra, and corners with two equivalent P(3)O4 tetrahedra. The Fe(2)-O(1) bond length is 1.95 Å. The Fe(2)-O(14) bond length is 1.97 Å. The Fe(2)-O(15) bond length is 2.06 Å. The Fe(2)-O(4) bond length is 2.21 Å. In the third Fe site, Fe(3) is bonded to one O(11), one O(12), one O(16), and one O(8) atom to form FeO4 tetrahedra that share  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one P(3)O4 tetrahedra, and corners with two equivalent P(2)O4 tetrahedra. The Fe(3)-O(11) bond length is 1.87 Å. The Fe(3)-O(12) bond length is 1.89 Å. The Fe(3)-O(16) bond length is 1.87 Å. The Fe(3)-O(8) bond length is 1.93 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 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(1)O4 tetrahedra. The Fe(4)-O(5) bond length is 1.87 Å. The Fe(4)-O(6) bond length is 1.89 Å. The Fe(4)-O(7) bond length is 1.90 Å. The Fe(4)-O(9) bond length is 1.87 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 Mg(1)O4 tetrahedra,  a cornercorner with one Fe(1)O4 tetrahedra,  a cornercorner with one Fe(3)O4 tetrahedra, and corners with two equivalent Fe(4)O4 tetrahedra. The P(1)-O(13) bond length is 1.57 Å. The P(1)-O(6) bond length is 1.55 Å. The P(1)-O(7) bond length is 1.56 Å. The P(1)-O(8) bond length is 1.54 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(4)O4 tetrahedra, corners with two equivalent Fe(3)O4 tetrahedra, and  a cornercorner with one Fe(2)O4 trigonal pyramid. The P(2)-O(1) bond length is 1.52 Å. The P(2)-O(11) bond length is 1.55 Å. The P(2)-O(16) bond length is 1.55 Å. The P(2)-O(9) bond length is 1.56 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 Mg(1)O4 tetrahedra,  a cornercorner with one Fe(1)O4 tetrahedra,  a cornercorner with one Fe(3)O4 tetrahedra, and corners with two equivalent Fe(2)O4 trigonal pyramids. The P(3)-O(10) bond length is 1.53 Å. The P(3)-O(12) bond length is 1.56 Å. The P(3)-O(14) bond length is 1.53 Å. The P(3)-O(15) bond length is 1.59 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(4)O4 tetrahedra, corners with two equivalent Mg(1)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra, and  a cornercorner with one Fe(2)O4 trigonal pyramid. The P(4)-O(2) bond length is 1.58 Å. The P(4)-O(3) bond length is 1.52 Å. The P(4)-O(4) bond length is 1.57 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 bent 120 degrees geometry to one Fe(2) and one P(2) atom. In the second O site, O(2) is bonded in a 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 120 degrees geometry to one Fe(1) and one P(4) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Mg(1), one Fe(2), and one P(4) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Fe(4) and one P(4) atom. In the sixth O site, O(6) is bonded in a distorted bent 150 degrees geometry to one Fe(4) and one P(1) atom. In the seventh O site, O(7) is bonded in a distorted bent 120 degrees geometry to one Fe(4) and one P(1) atom. In the eighth O site, O(8) is bonded in a distorted bent 120 degrees geometry to 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 bent 150 degrees geometry to one Fe(3) and one P(2) atom. In the twelfth O site, O(12) is bonded in a bent 120 degrees geometry to one Fe(3) and one P(3) atom. In the thirteenth O site, O(13) is bonded in a trigonal planar geometry to one Mg(1), one Fe(1), and one P(1) atom. In the fourteenth O site, O(14) is bonded in a bent 120 degrees geometry to one Fe(2) and one P(3) atom. In the fifteenth O site, O(15) is bonded in a trigonal planar geometry to one Mg(1), 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.