MgFe4(PO4)4 crystallizes in the triclinic P1 space group. Mg(1) is bonded in a 5-coordinate geometry to one O(3), one O(4), one O(5), one O(6), and one O(9) atom. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(16), one O(5), one O(6), and one O(7) atom to form distorted FeO4 tetrahedra 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  a cornercorner with one Fe(4)O5 trigonal bipyramid. In the second Fe site, Fe(2) is bonded in a 5-coordinate geometry to one O(2), one O(3), one O(4), one O(7), and one O(9) atom. In the third Fe site, Fe(3) is bonded to one O(13), one O(14), one O(15), and one O(8) 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 fourth Fe site, Fe(4) is bonded to one O(1), one O(10), one O(11), one O(12), and one O(16) atom to form distorted FeO5 trigonal bipyramids that share  a cornercorner with one Fe(1)O4 tetrahedra,  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one P(3)O4 tetrahedra,  a cornercorner with one P(4)O4 tetrahedra, and  an edgeedge with one P(4)O4 tetrahedra. There are four inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form PO4 tetrahedra that share corners with two equivalent Fe(1)O4 tetrahedra and  a cornercorner with one Fe(4)O5 trigonal bipyramid. In the second P site, P(2) is bonded to one O(2), one O(4), one O(7), and one O(8) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(1)O4 tetrahedra and  a cornercorner with one Fe(3)O4 tetrahedra. In the third P site, P(3) is bonded to one O(10), one O(13), one O(15), and one O(9) atom to form PO4 tetrahedra that share corners with two equivalent Fe(3)O4 tetrahedra and  a cornercorner with one Fe(4)O5 trigonal bipyramid. In the fourth P site, P(4) is bonded to one O(11), one O(12), one O(14), and one O(16) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(1)O4 tetrahedra,  a cornercorner with one Fe(3)O4 tetrahedra,  a cornercorner with one Fe(4)O5 trigonal bipyramid, and  an edgeedge with one Fe(4)O5 trigonal bipyramid. There are sixteen inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Fe(4) and one P(1) atom. In the second O site, O(2) is bonded in a water-like geometry to one Fe(2) and one P(2) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Mg(1), one Fe(2), and one P(1) atom. In the fourth O site, O(4) is bonded in a distorted T-shaped geometry to one Mg(1), one Fe(2), and one P(2) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Mg(1), one Fe(1), and one P(1) atom. In the sixth O site, O(6) is bonded in a distorted T-shaped geometry to one Mg(1), one Fe(1), and one P(1) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Fe(1), one Fe(2), and one P(2) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Fe(3) and one P(2) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to one Mg(1), one Fe(2), and one P(3) atom. In the tenth O site, O(10) is bonded in a bent 150 degrees geometry to one Fe(4) and one P(3) atom. In the eleventh O site, O(11) is bonded in a bent 150 degrees geometry to one Fe(4) and one P(4) atom. In the twelfth O site, O(12) is bonded in a water-like geometry to one Fe(4) and one P(4) atom. In the thirteenth O site, O(13) is bonded in a bent 120 degrees geometry to one Fe(3) and one P(3) atom. In the fourteenth O site, O(14) is bonded in a bent 120 degrees geometry to one Fe(3) and one P(4) atom. In the fifteenth O site, O(15) is bonded in a bent 120 degrees geometry to one Fe(3) and one P(3) atom. In the sixteenth O site, O(16) is bonded in a 3-coordinate geometry to one Fe(1), one Fe(4), and one P(4) atom.
MgFe4(PO4)4 crystallizes in the triclinic P1 space group. Mg(1) is bonded in a 5-coordinate geometry to one O(3), one O(4), one O(5), one O(6), and one O(9) atom. The Mg(1)-O(3) bond length is 2.29 Å. The Mg(1)-O(4) bond length is 2.00 Å. The Mg(1)-O(5) bond length is 2.03 Å. The Mg(1)-O(6) bond length is 2.08 Å. The Mg(1)-O(9) bond length is 2.02 Å. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(16), one O(5), one O(6), and one O(7) atom to form distorted FeO4 tetrahedra 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  a cornercorner with one Fe(4)O5 trigonal bipyramid. The Fe(1)-O(16) bond length is 2.04 Å. The Fe(1)-O(5) bond length is 2.22 Å. The Fe(1)-O(6) bond length is 2.01 Å. The Fe(1)-O(7) bond length is 1.97 Å. In the second Fe site, Fe(2) is bonded in a 5-coordinate geometry to one O(2), one O(3), one O(4), one O(7), and one O(9) atom. The Fe(2)-O(2) bond length is 1.97 Å. The Fe(2)-O(3) bond length is 2.07 Å. The Fe(2)-O(4) bond length is 2.14 Å. The Fe(2)-O(7) bond length is 2.30 Å. The Fe(2)-O(9) bond length is 2.39 Å. In the third Fe site, Fe(3) is bonded to one O(13), one O(14), one O(15), and one O(8) 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(3)-O(13) bond length is 1.87 Å. The Fe(3)-O(14) bond length is 1.92 Å. The Fe(3)-O(15) bond length is 1.90 Å. The Fe(3)-O(8) bond length is 1.88 Å. In the fourth Fe site, Fe(4) is bonded to one O(1), one O(10), one O(11), one O(12), and one O(16) atom to form distorted FeO5 trigonal bipyramids that share  a cornercorner with one Fe(1)O4 tetrahedra,  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one P(3)O4 tetrahedra,  a cornercorner with one P(4)O4 tetrahedra, and  an edgeedge with one P(4)O4 tetrahedra. The Fe(4)-O(1) bond length is 1.92 Å. The Fe(4)-O(10) bond length is 1.90 Å. The Fe(4)-O(11) bond length is 1.92 Å. The Fe(4)-O(12) bond length is 2.00 Å. The Fe(4)-O(16) bond length is 2.15 Å. There are four inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form PO4 tetrahedra that share corners with two equivalent Fe(1)O4 tetrahedra and  a cornercorner with one Fe(4)O5 trigonal bipyramid. The P(1)-O(1) bond length is 1.53 Å. The P(1)-O(3) bond length is 1.54 Å. The P(1)-O(5) bond length is 1.57 Å. The P(1)-O(6) bond length is 1.58 Å. In the second P site, P(2) is bonded to one O(2), one O(4), one O(7), and one O(8) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(1)O4 tetrahedra and  a cornercorner with one Fe(3)O4 tetrahedra. The P(2)-O(2) bond length is 1.53 Å. The P(2)-O(4) bond length is 1.56 Å. The P(2)-O(7) bond length is 1.55 Å. The P(2)-O(8) bond length is 1.55 Å. In the third P site, P(3) is bonded to one O(10), one O(13), one O(15), and one O(9) atom to form PO4 tetrahedra that share corners with two equivalent Fe(3)O4 tetrahedra and  a cornercorner with one Fe(4)O5 trigonal bipyramid. The P(3)-O(10) bond length is 1.54 Å. The P(3)-O(13) bond length is 1.56 Å. The P(3)-O(15) bond length is 1.55 Å. The P(3)-O(9) bond length is 1.54 Å. In the fourth P site, P(4) is bonded to one O(11), one O(12), one O(14), and one O(16) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(1)O4 tetrahedra,  a cornercorner with one Fe(3)O4 tetrahedra,  a cornercorner with one Fe(4)O5 trigonal bipyramid, and  an edgeedge with one Fe(4)O5 trigonal bipyramid. The P(4)-O(11) bond length is 1.53 Å. The P(4)-O(12) bond length is 1.54 Å. The P(4)-O(14) bond length is 1.56 Å. The P(4)-O(16) bond length is 1.58 Å. There are sixteen inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Fe(4) and one P(1) atom. In the second O site, O(2) is bonded in a water-like geometry to one Fe(2) and one P(2) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Mg(1), one Fe(2), and one P(1) atom. In the fourth O site, O(4) is bonded in a distorted T-shaped geometry to one Mg(1), one Fe(2), and one P(2) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Mg(1), one Fe(1), and one P(1) atom. In the sixth O site, O(6) is bonded in a distorted T-shaped geometry to one Mg(1), one Fe(1), and one P(1) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Fe(1), one Fe(2), and one P(2) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Fe(3) and one P(2) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to one Mg(1), one Fe(2), and one P(3) atom. In the tenth O site, O(10) is bonded in a bent 150 degrees geometry to one Fe(4) and one P(3) atom. In the eleventh O site, O(11) is bonded in a bent 150 degrees geometry to one Fe(4) and one P(4) atom. In the twelfth O site, O(12) is bonded in a water-like geometry to one Fe(4) and one P(4) atom. In the thirteenth O site, O(13) is bonded in a bent 120 degrees geometry to one Fe(3) and one P(3) atom. In the fourteenth O site, O(14) is bonded in a bent 120 degrees geometry to one Fe(3) and one P(4) atom. In the fifteenth O site, O(15) is bonded in a bent 120 degrees geometry to one Fe(3) and one P(3) atom. In the sixteenth O site, O(16) is bonded in a 3-coordinate geometry to one Fe(1), one Fe(4), and one P(4) atom.