BiAs2O7 crystallizes in the monoclinic P2_1/c space group. Bi(1) is bonded to one O(1), one O(2), one O(5), one O(6), and one O(7) atom to form BiO5 trigonal bipyramids that share corners with two equivalent As(1)O4 tetrahedra and corners with three equivalent As(2)O4 tetrahedra. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(2), one O(3), one O(4), and one O(6) atom to form AsO4 tetrahedra that share  a cornercorner with one As(2)O4 tetrahedra and corners with two equivalent Bi(1)O5 trigonal bipyramids. In the second As site, As(2) is bonded to one O(1), one O(4), one O(5), and one O(7) atom to form AsO4 tetrahedra that share  a cornercorner with one As(1)O4 tetrahedra and corners with three equivalent Bi(1)O5 trigonal bipyramids. There are seven inequivalent O sites. In the first O site, O(6) is bonded in a distorted bent 150 degrees geometry to one Bi(1) and one As(1) atom. In the second O site, O(7) is bonded in a bent 120 degrees geometry to one Bi(1) and one As(2) atom. In the third O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Bi(1) and one As(2) atom. In the fourth O site, O(2) is bonded in a distorted bent 120 degrees geometry to one Bi(1) and one As(1) atom. In the fifth O site, O(3) is bonded in a single-bond geometry to one As(1) atom. In the sixth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one As(1) and one As(2) atom. In the seventh O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Bi(1) and one As(2) atom.
BiAs2O7 crystallizes in the monoclinic P2_1/c space group. Bi(1) is bonded to one O(1), one O(2), one O(5), one O(6), and one O(7) atom to form BiO5 trigonal bipyramids that share corners with two equivalent As(1)O4 tetrahedra and corners with three equivalent As(2)O4 tetrahedra. The Bi(1)-O(1) bond length is 2.25 Å. The Bi(1)-O(2) bond length is 2.23 Å. The Bi(1)-O(5) bond length is 2.28 Å. The Bi(1)-O(6) bond length is 2.22 Å. The Bi(1)-O(7) bond length is 2.19 Å. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(2), one O(3), one O(4), and one O(6) atom to form AsO4 tetrahedra that share  a cornercorner with one As(2)O4 tetrahedra and corners with two equivalent Bi(1)O5 trigonal bipyramids. The As(1)-O(2) bond length is 1.74 Å. The As(1)-O(3) bond length is 1.66 Å. The As(1)-O(4) bond length is 1.83 Å. The As(1)-O(6) bond length is 1.73 Å. In the second As site, As(2) is bonded to one O(1), one O(4), one O(5), and one O(7) atom to form AsO4 tetrahedra that share  a cornercorner with one As(1)O4 tetrahedra and corners with three equivalent Bi(1)O5 trigonal bipyramids. The As(2)-O(1) bond length is 1.72 Å. The As(2)-O(4) bond length is 1.76 Å. The As(2)-O(5) bond length is 1.71 Å. The As(2)-O(7) bond length is 1.73 Å. There are seven inequivalent O sites. In the first O site, O(6) is bonded in a distorted bent 150 degrees geometry to one Bi(1) and one As(1) atom. In the second O site, O(7) is bonded in a bent 120 degrees geometry to one Bi(1) and one As(2) atom. In the third O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Bi(1) and one As(2) atom. In the fourth O site, O(2) is bonded in a distorted bent 120 degrees geometry to one Bi(1) and one As(1) atom. In the fifth O site, O(3) is bonded in a single-bond geometry to one As(1) atom. In the sixth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one As(1) and one As(2) atom. In the seventh O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Bi(1) and one As(2) atom.