Fe2Cu(AsO7)2 crystallizes in the monoclinic P2_1/c space group. Fe(1) is bonded to one O(2), one O(4), two equivalent O(1), and two equivalent O(5) atoms to form FeO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with four equivalent As(1)O4 tetrahedra, and  an edgeedge with one Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles are 47°. Cu(1) is bonded in a 4-coordinate geometry to two equivalent O(3) and two equivalent O(7) atoms. As(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form AsO4 tetrahedra that share corners with four equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 54-64°. There are seven inequivalent O sites. In the first O site, O(7) is bonded in a bent 120 degrees geometry to one Cu(1) and one O(6) atom. In the second O site, O(1) is bonded in a trigonal planar geometry to two equivalent Fe(1) and one As(1) atom. In the third O site, O(2) is bonded in a bent 120 degrees geometry to one Fe(1) and one As(1) atom. In the fourth O site, O(3) is bonded in a bent 120 degrees geometry to one Cu(1) and one As(1) atom. In the fifth O site, O(4) is bonded in a bent 120 degrees geometry to one Fe(1) and one As(1) atom. In the sixth O site, O(5) is bonded in a distorted bent 120 degrees geometry to two equivalent Fe(1) atoms. In the seventh O site, O(6) is bonded in a distorted single-bond geometry to one O(7) atom.
Fe2Cu(AsO7)2 crystallizes in the monoclinic P2_1/c space group. Fe(1) is bonded to one O(2), one O(4), two equivalent O(1), and two equivalent O(5) atoms to form FeO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with four equivalent As(1)O4 tetrahedra, and  an edgeedge with one Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles are 47°. The Fe(1)-O(2) bond length is 1.96 Å. The Fe(1)-O(4) bond length is 1.99 Å. There is one shorter (2.10 Å) and one longer (2.13 Å) Fe(1)-O(1) bond length. There is one shorter (1.84 Å) and one longer (1.94 Å) Fe(1)-O(5) bond length. Cu(1) is bonded in a 4-coordinate geometry to two equivalent O(3) and two equivalent O(7) atoms. Both Cu(1)-O(3) bond lengths are 1.82 Å. Both Cu(1)-O(7) bond lengths are 2.32 Å. As(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form AsO4 tetrahedra that share corners with four equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 54-64°. The As(1)-O(1) bond length is 1.75 Å. The As(1)-O(2) bond length is 1.72 Å. The As(1)-O(3) bond length is 1.73 Å. The As(1)-O(4) bond length is 1.72 Å. There are seven inequivalent O sites. In the first O site, O(7) is bonded in a bent 120 degrees geometry to one Cu(1) and one O(6) atom. The O(7)-O(6) bond length is 1.23 Å. In the second O site, O(1) is bonded in a trigonal planar geometry to two equivalent Fe(1) and one As(1) atom. In the third O site, O(2) is bonded in a bent 120 degrees geometry to one Fe(1) and one As(1) atom. In the fourth O site, O(3) is bonded in a bent 120 degrees geometry to one Cu(1) and one As(1) atom. In the fifth O site, O(4) is bonded in a bent 120 degrees geometry to one Fe(1) and one As(1) atom. In the sixth O site, O(5) is bonded in a distorted bent 120 degrees geometry to two equivalent Fe(1) atoms. In the seventh O site, O(6) is bonded in a distorted single-bond geometry to one O(7) atom.