Mn2As2O7 crystallizes in the triclinic P1 space group. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form distorted MnO6 pentagonal pyramids that share corners with three equivalent As(1)O4 tetrahedra, corners with three equivalent As(2)O4 tetrahedra, and edges with three equivalent Mn(2)O6 octahedra. In the second Mn site, Mn(2) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form distorted MnO6 octahedra that share corners with three equivalent As(1)O4 tetrahedra, corners with three equivalent As(2)O4 tetrahedra, and edges with three equivalent Mn(1)O6 pentagonal pyramids. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(1), one O(2), one O(5), and one O(7) atom to form AsO4 tetrahedra that share corners with three equivalent Mn(2)O6 octahedra, corners with three equivalent Mn(1)O6 pentagonal pyramids, and  a cornercorner with one As(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 44-61°. In the second As site, As(2) is bonded to one O(3), one O(4), one O(6), and one O(7) atom to form AsO4 tetrahedra that share corners with three equivalent Mn(2)O6 octahedra, corners with three equivalent Mn(1)O6 pentagonal pyramids, and  a cornercorner with one As(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 44-61°. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Mn(1), one Mn(2), and one As(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Mn(1), one Mn(2), and one As(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Mn(1), one Mn(2), and one As(2) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Mn(1), one Mn(2), and one As(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Mn(1), one Mn(2), and one As(1) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Mn(1), one Mn(2), and one As(2) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one As(1) and one As(2) atom.
Mn2As2O7 crystallizes in the triclinic P1 space group. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form distorted MnO6 pentagonal pyramids that share corners with three equivalent As(1)O4 tetrahedra, corners with three equivalent As(2)O4 tetrahedra, and edges with three equivalent Mn(2)O6 octahedra. The Mn(1)-O(1) bond length is 2.13 Å. The Mn(1)-O(2) bond length is 2.34 Å. The Mn(1)-O(3) bond length is 2.34 Å. The Mn(1)-O(4) bond length is 2.13 Å. The Mn(1)-O(5) bond length is 2.16 Å. The Mn(1)-O(6) bond length is 2.17 Å. In the second Mn site, Mn(2) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form distorted MnO6 octahedra that share corners with three equivalent As(1)O4 tetrahedra, corners with three equivalent As(2)O4 tetrahedra, and edges with three equivalent Mn(1)O6 pentagonal pyramids. The Mn(2)-O(1) bond length is 2.21 Å. The Mn(2)-O(2) bond length is 2.11 Å. The Mn(2)-O(3) bond length is 2.11 Å. The Mn(2)-O(4) bond length is 2.21 Å. The Mn(2)-O(5) bond length is 2.18 Å. The Mn(2)-O(6) bond length is 2.18 Å. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(1), one O(2), one O(5), and one O(7) atom to form AsO4 tetrahedra that share corners with three equivalent Mn(2)O6 octahedra, corners with three equivalent Mn(1)O6 pentagonal pyramids, and  a cornercorner with one As(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 44-61°. The As(1)-O(1) bond length is 1.69 Å. The As(1)-O(2) bond length is 1.68 Å. The As(1)-O(5) bond length is 1.69 Å. The As(1)-O(7) bond length is 1.74 Å. In the second As site, As(2) is bonded to one O(3), one O(4), one O(6), and one O(7) atom to form AsO4 tetrahedra that share corners with three equivalent Mn(2)O6 octahedra, corners with three equivalent Mn(1)O6 pentagonal pyramids, and  a cornercorner with one As(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 44-61°. The As(2)-O(3) bond length is 1.68 Å. The As(2)-O(4) bond length is 1.69 Å. The As(2)-O(6) bond length is 1.69 Å. The As(2)-O(7) bond length is 1.73 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Mn(1), one Mn(2), and one As(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Mn(1), one Mn(2), and one As(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Mn(1), one Mn(2), and one As(2) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Mn(1), one Mn(2), and one As(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Mn(1), one Mn(2), and one As(1) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Mn(1), one Mn(2), and one As(2) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one As(1) and one As(2) atom.