KMgFe(PO4)2 crystallizes in the monoclinic P2_1/c space group. K(1) is bonded in a 8-coordinate geometry to one O(2), one O(3), one O(4), one O(7), two equivalent O(1), and two equivalent O(8) atoms. Mg(1) is bonded to one O(4), one O(6), two equivalent O(3), and two equivalent O(5) atoms to form MgO6 octahedra that share  a cornercorner with one P(2)O4 tetrahedra, corners with three equivalent P(1)O4 tetrahedra,  a cornercorner with one Fe(1)O5 trigonal bipyramid, edges with two equivalent Mg(1)O6 octahedra, and  an edgeedge with one P(2)O4 tetrahedra. Fe(1) is bonded to one O(1), one O(2), one O(6), one O(7), and one O(8) atom to form FeO5 trigonal bipyramids that share  a cornercorner with one Mg(1)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra, and corners with three equivalent P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 54°. There are two inequivalent P sites. In the first P site, 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 corners with three equivalent Mg(1)O6 octahedra and corners with two equivalent Fe(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 54-57°. In the second P site, P(2) is bonded to one O(5), one O(6), one O(7), and one O(8) atom to form PO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra, corners with three equivalent Fe(1)O5 trigonal bipyramids, and  an edgeedge with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles are 4°. There are eight inequivalent O sites. In the first O site, O(4) is bonded in a 3-coordinate geometry to one K(1), one Mg(1), and one P(1) atom. In the second O site, O(5) is bonded in a distorted T-shaped geometry to two equivalent Mg(1) and one P(2) atom. In the third O site, O(6) is bonded in a distorted trigonal planar geometry to one Mg(1), one Fe(1), and one P(2) atom. In the fourth O site, O(7) is bonded in a 3-coordinate geometry to one K(1), one Fe(1), and one P(2) atom. In the fifth O site, O(8) is bonded in a 2-coordinate geometry to two equivalent K(1), one Fe(1), and one P(2) atom. In the sixth O site, O(1) is bonded in a 2-coordinate geometry to two equivalent K(1), one Fe(1), and one P(1) atom. In the seventh O site, O(2) is bonded in a 2-coordinate geometry to one K(1), one Fe(1), and one P(1) atom. In the eighth O site, O(3) is bonded in a 3-coordinate geometry to one K(1), two equivalent Mg(1), and one P(1) atom.
KMgFe(PO4)2 crystallizes in the monoclinic P2_1/c space group. K(1) is bonded in a 8-coordinate geometry to one O(2), one O(3), one O(4), one O(7), two equivalent O(1), and two equivalent O(8) atoms. The K(1)-O(2) bond length is 2.88 Å. The K(1)-O(3) bond length is 3.01 Å. The K(1)-O(4) bond length is 2.88 Å. The K(1)-O(7) bond length is 2.89 Å. There is one shorter (2.80 Å) and one longer (3.14 Å) K(1)-O(1) bond length. There is one shorter (2.86 Å) and one longer (3.32 Å) K(1)-O(8) bond length. Mg(1) is bonded to one O(4), one O(6), two equivalent O(3), and two equivalent O(5) atoms to form MgO6 octahedra that share  a cornercorner with one P(2)O4 tetrahedra, corners with three equivalent P(1)O4 tetrahedra,  a cornercorner with one Fe(1)O5 trigonal bipyramid, edges with two equivalent Mg(1)O6 octahedra, and  an edgeedge with one P(2)O4 tetrahedra. The Mg(1)-O(4) bond length is 2.05 Å. The Mg(1)-O(6) bond length is 2.22 Å. There is one shorter (2.04 Å) and one longer (2.16 Å) Mg(1)-O(3) bond length. There is one shorter (2.07 Å) and one longer (2.26 Å) Mg(1)-O(5) bond length. Fe(1) is bonded to one O(1), one O(2), one O(6), one O(7), and one O(8) atom to form FeO5 trigonal bipyramids that share  a cornercorner with one Mg(1)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra, and corners with three equivalent P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 54°. The Fe(1)-O(1) bond length is 1.93 Å. The Fe(1)-O(2) bond length is 1.96 Å. The Fe(1)-O(6) bond length is 1.96 Å. The Fe(1)-O(7) bond length is 1.95 Å. The Fe(1)-O(8) bond length is 2.04 Å. There are two inequivalent P sites. In the first P site, 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 corners with three equivalent Mg(1)O6 octahedra and corners with two equivalent Fe(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 54-57°. The P(1)-O(1) bond length is 1.56 Å. The P(1)-O(2) bond length is 1.55 Å. The P(1)-O(3) bond length is 1.57 Å. The P(1)-O(4) bond length is 1.54 Å. In the second P site, P(2) is bonded to one O(5), one O(6), one O(7), and one O(8) atom to form PO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra, corners with three equivalent Fe(1)O5 trigonal bipyramids, and  an edgeedge with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles are 4°. The P(2)-O(5) bond length is 1.54 Å. The P(2)-O(6) bond length is 1.58 Å. The P(2)-O(7) bond length is 1.55 Å. The P(2)-O(8) bond length is 1.54 Å. There are eight inequivalent O sites. In the first O site, O(4) is bonded in a 3-coordinate geometry to one K(1), one Mg(1), and one P(1) atom. In the second O site, O(5) is bonded in a distorted T-shaped geometry to two equivalent Mg(1) and one P(2) atom. In the third O site, O(6) is bonded in a distorted trigonal planar geometry to one Mg(1), one Fe(1), and one P(2) atom. In the fourth O site, O(7) is bonded in a 3-coordinate geometry to one K(1), one Fe(1), and one P(2) atom. In the fifth O site, O(8) is bonded in a 2-coordinate geometry to two equivalent K(1), one Fe(1), and one P(2) atom. In the sixth O site, O(1) is bonded in a 2-coordinate geometry to two equivalent K(1), one Fe(1), and one P(1) atom. In the seventh O site, O(2) is bonded in a 2-coordinate geometry to one K(1), one Fe(1), and one P(1) atom. In the eighth O site, O(3) is bonded in a 3-coordinate geometry to one K(1), two equivalent Mg(1), and one P(1) atom.