MgTa2(FeO4)2 crystallizes in the monoclinic P2 space group. Mg(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form MgO6 octahedra that share corners with four equivalent Fe(2)O6 octahedra, edges with two equivalent Ta(1)O6 octahedra, edges with two equivalent Ta(2)O6 octahedra, and faces with two equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-54°. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form TaO6 octahedra that share corners with four equivalent Fe(1)O6 octahedra, corners with four equivalent Fe(2)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, and edges with two equivalent Ta(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-53°. In the second Ta site, Ta(2) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form TaO6 octahedra that share corners with four equivalent Fe(1)O6 octahedra, corners with four equivalent Fe(2)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, and edges with two equivalent Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-53°. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form distorted FeO6 octahedra that share corners with four equivalent Ta(1)O6 octahedra, corners with four equivalent Ta(2)O6 octahedra, edges with two equivalent Fe(2)O6 octahedra, and faces with two equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-52°. In the second Fe site, Fe(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form FeO6 octahedra that share corners with four equivalent Mg(1)O6 octahedra, corners with four equivalent Ta(1)O6 octahedra, corners with four equivalent Ta(2)O6 octahedra, and edges with two equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-54°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Ta(1), one Fe(1), and one Fe(2) atom. In the second O site, O(2) is bonded in a trigonal planar geometry to one Ta(1), one Ta(2), and one Fe(2) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Mg(1), one Ta(2), one Fe(1), and one Fe(2) atom. In the fourth O site, O(4) is bonded to one Mg(1), one Ta(1), one Ta(2), and one Fe(1) atom to form a mixture of distorted corner and edge-sharing OMgTa2Fe trigonal pyramids.
MgTa2(FeO4)2 crystallizes in the monoclinic P2 space group. Mg(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form MgO6 octahedra that share corners with four equivalent Fe(2)O6 octahedra, edges with two equivalent Ta(1)O6 octahedra, edges with two equivalent Ta(2)O6 octahedra, and faces with two equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-54°. Both Mg(1)-O(1) bond lengths are 2.03 Å. Both Mg(1)-O(3) bond lengths are 2.12 Å. Both Mg(1)-O(4) bond lengths are 2.05 Å. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form TaO6 octahedra that share corners with four equivalent Fe(1)O6 octahedra, corners with four equivalent Fe(2)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, and edges with two equivalent Ta(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-53°. Both Ta(1)-O(1) bond lengths are 1.93 Å. Both Ta(1)-O(2) bond lengths are 2.00 Å. Both Ta(1)-O(4) bond lengths are 2.15 Å. In the second Ta site, Ta(2) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form TaO6 octahedra that share corners with four equivalent Fe(1)O6 octahedra, corners with four equivalent Fe(2)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, and edges with two equivalent Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-53°. Both Ta(2)-O(2) bond lengths are 2.08 Å. Both Ta(2)-O(3) bond lengths are 1.96 Å. Both Ta(2)-O(4) bond lengths are 2.01 Å. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form distorted FeO6 octahedra that share corners with four equivalent Ta(1)O6 octahedra, corners with four equivalent Ta(2)O6 octahedra, edges with two equivalent Fe(2)O6 octahedra, and faces with two equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-52°. Both Fe(1)-O(1) bond lengths are 2.23 Å. Both Fe(1)-O(3) bond lengths are 2.13 Å. Both Fe(1)-O(4) bond lengths are 2.16 Å. In the second Fe site, Fe(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form FeO6 octahedra that share corners with four equivalent Mg(1)O6 octahedra, corners with four equivalent Ta(1)O6 octahedra, corners with four equivalent Ta(2)O6 octahedra, and edges with two equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 47-54°. Both Fe(2)-O(1) bond lengths are 2.24 Å. Both Fe(2)-O(2) bond lengths are 2.21 Å. Both Fe(2)-O(3) bond lengths are 2.35 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Ta(1), one Fe(1), and one Fe(2) atom. In the second O site, O(2) is bonded in a trigonal planar geometry to one Ta(1), one Ta(2), and one Fe(2) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Mg(1), one Ta(2), one Fe(1), and one Fe(2) atom. In the fourth O site, O(4) is bonded to one Mg(1), one Ta(1), one Ta(2), and one Fe(1) atom to form a mixture of distorted corner and edge-sharing OMgTa2Fe trigonal pyramids.