BaCoAs2O7 crystallizes in the triclinic P-1 space group. Ba(1) is bonded in a 10-coordinate geometry to one O(3), one O(5), one O(6), two equivalent O(2), two equivalent O(7), and three equivalent O(1) atoms. Co(1) is bonded to one O(2), one O(5), one O(6), and two equivalent O(3) atoms to form CoO5 trigonal bipyramids that share corners with two equivalent As(2)O4 tetrahedra, corners with three equivalent As(1)O4 tetrahedra, and  an edgeedge with one Co(1)O5 trigonal bipyramid. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(3), one O(4), one O(5), and one O(7) atom to form AsO4 tetrahedra that share  a cornercorner with one As(2)O4 tetrahedra and corners with three equivalent Co(1)O5 trigonal bipyramids. In the second As site, As(2) is bonded to one O(1), one O(2), one O(4), and one O(6) atom to form AsO4 tetrahedra that share  a cornercorner with one As(1)O4 tetrahedra and corners with two equivalent Co(1)O5 trigonal bipyramids. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to three equivalent Ba(1) and one As(2) atom. In the second O site, O(2) is bonded in a 2-coordinate geometry to two equivalent Ba(1), one Co(1), and one As(2) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Ba(1), two equivalent Co(1), and one As(1) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one As(1) and one As(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Ba(1), one Co(1), and one As(1) atom. In the sixth O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Ba(1), one Co(1), and one As(2) atom. In the seventh O site, O(7) is bonded in a distorted single-bond geometry to two equivalent Ba(1) and one As(1) atom.
BaCoAs2O7 crystallizes in the triclinic P-1 space group. Ba(1) is bonded in a 10-coordinate geometry to one O(3), one O(5), one O(6), two equivalent O(2), two equivalent O(7), and three equivalent O(1) atoms. The Ba(1)-O(3) bond length is 3.00 Å. The Ba(1)-O(5) bond length is 2.87 Å. The Ba(1)-O(6) bond length is 3.06 Å. There is one shorter (2.87 Å) and one longer (3.20 Å) Ba(1)-O(2) bond length. There is one shorter (2.68 Å) and one longer (3.15 Å) Ba(1)-O(7) bond length. There are two shorter (2.88 Å) and one longer (3.05 Å) Ba(1)-O(1) bond length. Co(1) is bonded to one O(2), one O(5), one O(6), and two equivalent O(3) atoms to form CoO5 trigonal bipyramids that share corners with two equivalent As(2)O4 tetrahedra, corners with three equivalent As(1)O4 tetrahedra, and  an edgeedge with one Co(1)O5 trigonal bipyramid. The Co(1)-O(2) bond length is 2.06 Å. The Co(1)-O(5) bond length is 2.02 Å. The Co(1)-O(6) bond length is 2.05 Å. There is one shorter (2.05 Å) and one longer (2.23 Å) Co(1)-O(3) bond length. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(3), one O(4), one O(5), and one O(7) atom to form AsO4 tetrahedra that share  a cornercorner with one As(2)O4 tetrahedra and corners with three equivalent Co(1)O5 trigonal bipyramids. The As(1)-O(3) bond length is 1.75 Å. The As(1)-O(4) bond length is 1.79 Å. The As(1)-O(5) bond length is 1.71 Å. The As(1)-O(7) bond length is 1.67 Å. In the second As site, As(2) is bonded to one O(1), one O(2), one O(4), and one O(6) atom to form AsO4 tetrahedra that share  a cornercorner with one As(1)O4 tetrahedra and corners with two equivalent Co(1)O5 trigonal bipyramids. The As(2)-O(1) bond length is 1.69 Å. The As(2)-O(2) bond length is 1.72 Å. The As(2)-O(4) bond length is 1.80 Å. The As(2)-O(6) bond length is 1.71 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to three equivalent Ba(1) and one As(2) atom. In the second O site, O(2) is bonded in a 2-coordinate geometry to two equivalent Ba(1), one Co(1), and one As(2) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Ba(1), two equivalent Co(1), and one As(1) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one As(1) and one As(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Ba(1), one Co(1), and one As(1) atom. In the sixth O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Ba(1), one Co(1), and one As(2) atom. In the seventh O site, O(7) is bonded in a distorted single-bond geometry to two equivalent Ba(1) and one As(1) atom.