Ba2As2O7 crystallizes in the triclinic P-1 space group. There are four inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 8-coordinate geometry to one O(1), one O(14), one O(2), one O(3), one O(8), one O(9), and two equivalent O(11) atoms. In the second Ba site, Ba(2) is bonded in a 10-coordinate geometry to one O(1), one O(10), one O(11), one O(12), one O(2), one O(3), one O(4), one O(7), one O(8), and one O(9) atom. In the third Ba site, Ba(3) is bonded in a 8-coordinate geometry to one O(1), one O(10), one O(13), one O(14), one O(3), one O(5), one O(6), and one O(7) atom. In the fourth Ba site, Ba(4) is bonded in a 9-coordinate geometry to one O(10), one O(12), one O(14), one O(2), one O(6), one O(7), one O(8), and two equivalent O(5) atoms. There are four inequivalent As sites. In the first As site, As(1) is bonded to one O(10), one O(3), one O(4), and one O(9) atom to form corner-sharing AsO4 tetrahedra. In the second As site, As(2) is bonded to one O(11), one O(2), one O(4), and one O(8) atom to form corner-sharing AsO4 tetrahedra. In the third As site, As(3) is bonded to one O(1), one O(13), one O(14), and one O(6) atom to form corner-sharing AsO4 tetrahedra. In the fourth As site, As(4) is bonded to one O(12), one O(13), one O(5), and one O(7) atom to form corner-sharing AsO4 tetrahedra. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one Ba(1), one Ba(2), one Ba(3), and one As(3) atom. In the second O site, O(2) is bonded in a 1-coordinate geometry to one Ba(1), one Ba(2), one Ba(4), and one As(2) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Ba(1), one Ba(2), one Ba(3), and one As(1) atom. In the fourth O site, O(4) is bonded in a distorted bent 120 degrees geometry to one Ba(2), one As(1), and one As(2) atom. In the fifth O site, O(5) is bonded in a distorted single-bond geometry to one Ba(3), two equivalent Ba(4), and one As(4) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Ba(3), one Ba(4), and one As(3) atom. In the seventh O site, O(7) is bonded in a distorted single-bond geometry to one Ba(2), one Ba(3), one Ba(4), and one As(4) atom. In the eighth O site, O(8) is bonded in a distorted single-bond geometry to one Ba(1), one Ba(2), one Ba(4), and one As(2) atom. In the ninth O site, O(9) is bonded in a distorted trigonal planar geometry to one Ba(1), one Ba(2), and one As(1) atom. In the tenth O site, O(10) is bonded in a distorted single-bond geometry to one Ba(2), one Ba(3), one Ba(4), and one As(1) atom. In the eleventh O site, O(11) is bonded to one Ba(2), two equivalent Ba(1), and one As(2) atom to form distorted edge-sharing OBa3As tetrahedra. In the twelfth O site, O(12) is bonded in a distorted single-bond geometry to one Ba(2), one Ba(4), and one As(4) atom. In the thirteenth O site, O(13) is bonded in a distorted bent 120 degrees geometry to one Ba(3), one As(3), and one As(4) atom. In the fourteenth O site, O(14) is bonded in a distorted single-bond geometry to one Ba(1), one Ba(3), one Ba(4), and one As(3) atom.
Ba2As2O7 crystallizes in the triclinic P-1 space group. There are four inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 8-coordinate geometry to one O(1), one O(14), one O(2), one O(3), one O(8), one O(9), and two equivalent O(11) atoms. The Ba(1)-O(1) bond length is 2.74 Å. The Ba(1)-O(14) bond length is 2.95 Å. The Ba(1)-O(2) bond length is 2.67 Å. The Ba(1)-O(3) bond length is 2.86 Å. The Ba(1)-O(8) bond length is 3.14 Å. The Ba(1)-O(9) bond length is 2.68 Å. There is one shorter (2.69 Å) and one longer (2.75 Å) Ba(1)-O(11) bond length. In the second Ba site, Ba(2) is bonded in a 10-coordinate geometry to one O(1), one O(10), one O(11), one O(12), one O(2), one O(3), one O(4), one O(7), one O(8), and one O(9) atom. The Ba(2)-O(1) bond length is 3.38 Å. The Ba(2)-O(10) bond length is 2.81 Å. The Ba(2)-O(11) bond length is 2.77 Å. The Ba(2)-O(12) bond length is 3.26 Å. The Ba(2)-O(2) bond length is 3.38 Å. The Ba(2)-O(3) bond length is 2.77 Å. The Ba(2)-O(4) bond length is 2.95 Å. The Ba(2)-O(7) bond length is 2.73 Å. The Ba(2)-O(8) bond length is 2.84 Å. The Ba(2)-O(9) bond length is 2.72 Å. In the third Ba site, Ba(3) is bonded in a 8-coordinate geometry to one O(1), one O(10), one O(13), one O(14), one O(3), one O(5), one O(6), and one O(7) atom. The Ba(3)-O(1) bond length is 2.74 Å. The Ba(3)-O(10) bond length is 2.98 Å. The Ba(3)-O(13) bond length is 3.03 Å. The Ba(3)-O(14) bond length is 2.80 Å. The Ba(3)-O(3) bond length is 2.93 Å. The Ba(3)-O(5) bond length is 2.74 Å. The Ba(3)-O(6) bond length is 2.66 Å. The Ba(3)-O(7) bond length is 2.79 Å. In the fourth Ba site, Ba(4) is bonded in a 9-coordinate geometry to one O(10), one O(12), one O(14), one O(2), one O(6), one O(7), one O(8), and two equivalent O(5) atoms. The Ba(4)-O(10) bond length is 3.01 Å. The Ba(4)-O(12) bond length is 2.74 Å. The Ba(4)-O(14) bond length is 2.80 Å. The Ba(4)-O(2) bond length is 2.91 Å. The Ba(4)-O(6) bond length is 2.72 Å. The Ba(4)-O(7) bond length is 2.92 Å. The Ba(4)-O(8) bond length is 3.02 Å. There is one shorter (2.81 Å) and one longer (2.93 Å) Ba(4)-O(5) bond length. There are four inequivalent As sites. In the first As site, As(1) is bonded to one O(10), one O(3), one O(4), and one O(9) atom to form corner-sharing AsO4 tetrahedra. The As(1)-O(10) bond length is 1.69 Å. The As(1)-O(3) bond length is 1.68 Å. The As(1)-O(4) bond length is 1.81 Å. The As(1)-O(9) bond length is 1.66 Å. In the second As site, As(2) is bonded to one O(11), one O(2), one O(4), and one O(8) atom to form corner-sharing AsO4 tetrahedra. The As(2)-O(11) bond length is 1.69 Å. The As(2)-O(2) bond length is 1.67 Å. The As(2)-O(4) bond length is 1.79 Å. The As(2)-O(8) bond length is 1.68 Å. In the third As site, As(3) is bonded to one O(1), one O(13), one O(14), and one O(6) atom to form corner-sharing AsO4 tetrahedra. The As(3)-O(1) bond length is 1.68 Å. The As(3)-O(13) bond length is 1.80 Å. The As(3)-O(14) bond length is 1.69 Å. The As(3)-O(6) bond length is 1.67 Å. In the fourth As site, As(4) is bonded to one O(12), one O(13), one O(5), and one O(7) atom to form corner-sharing AsO4 tetrahedra. The As(4)-O(12) bond length is 1.67 Å. The As(4)-O(13) bond length is 1.79 Å. The As(4)-O(5) bond length is 1.69 Å. The As(4)-O(7) bond length is 1.69 Å. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one Ba(1), one Ba(2), one Ba(3), and one As(3) atom. In the second O site, O(2) is bonded in a 1-coordinate geometry to one Ba(1), one Ba(2), one Ba(4), and one As(2) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Ba(1), one Ba(2), one Ba(3), and one As(1) atom. In the fourth O site, O(4) is bonded in a distorted bent 120 degrees geometry to one Ba(2), one As(1), and one As(2) atom. In the fifth O site, O(5) is bonded in a distorted single-bond geometry to one Ba(3), two equivalent Ba(4), and one As(4) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Ba(3), one Ba(4), and one As(3) atom. In the seventh O site, O(7) is bonded in a distorted single-bond geometry to one Ba(2), one Ba(3), one Ba(4), and one As(4) atom. In the eighth O site, O(8) is bonded in a distorted single-bond geometry to one Ba(1), one Ba(2), one Ba(4), and one As(2) atom. In the ninth O site, O(9) is bonded in a distorted trigonal planar geometry to one Ba(1), one Ba(2), and one As(1) atom. In the tenth O site, O(10) is bonded in a distorted single-bond geometry to one Ba(2), one Ba(3), one Ba(4), and one As(1) atom. In the eleventh O site, O(11) is bonded to one Ba(2), two equivalent Ba(1), and one As(2) atom to form distorted edge-sharing OBa3As tetrahedra. In the twelfth O site, O(12) is bonded in a distorted single-bond geometry to one Ba(2), one Ba(4), and one As(4) atom. In the thirteenth O site, O(13) is bonded in a distorted bent 120 degrees geometry to one Ba(3), one As(3), and one As(4) atom. In the fourteenth O site, O(14) is bonded in a distorted single-bond geometry to one Ba(1), one Ba(3), one Ba(4), and one As(3) atom.