Ba10MgAs6(O12Cl)2 crystallizes in the monoclinic Pm space group. There are eight inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 9-coordinate geometry to one O(10), one O(11), one O(13), one O(14), one O(18), one O(3), one O(6), one O(7), and one O(9) atom. In the second Ba site, Ba(2) is bonded in a 7-coordinate geometry to one O(1), one O(12), one O(15), one O(17), one O(2), one O(4), and one O(8) atom. In the third Ba site, Ba(3) is bonded to one O(11), one O(2), two equivalent O(10), and two equivalent O(5) atoms to form distorted BaO6 pentagonal pyramids that share  a cornercorner with one As(1)O4 tetrahedra,  a cornercorner with one As(4)O4 tetrahedra, corners with two equivalent As(5)O4 tetrahedra, and  an edgeedge with one As(6)O4 tetrahedra. In the fourth Ba site, Ba(4) is bonded in a 5-coordinate geometry to one O(9), two equivalent O(1), and two equivalent O(13) atoms. In the fifth Ba site, Ba(5) is bonded in a 5-coordinate geometry to one O(18), two equivalent O(16), and two equivalent O(3) atoms. In the sixth Ba site, Ba(6) is bonded in a 5-coordinate geometry to one O(12), one O(14), one O(7), and two equivalent O(10) atoms. In the seventh Ba site, Ba(7) is bonded in a 5-coordinate geometry to one O(8), two equivalent O(13), and two equivalent O(16) atoms. In the eighth Ba site, Ba(8) is bonded in a 8-coordinate geometry to one O(4), one O(6), two equivalent O(3), two equivalent O(5), and two equivalent Cl(1) atoms. Mg(1) is bonded in a 4-coordinate geometry to two equivalent O(1) and two equivalent Cl(1) atoms. There are six inequivalent As sites. In the first As site, As(1) is bonded to one O(11), one O(15), and two equivalent O(13) atoms to form AsO4 tetrahedra that share  a cornercorner with one Ba(3)O6 pentagonal pyramid. In the second As site, As(2) is bonded in a distorted rectangular see-saw-like geometry to one O(4), one O(6), and two equivalent O(1) atoms. In the third As site, As(3) is bonded in a tetrahedral geometry to one O(12), one O(14), and two equivalent O(16) atoms. In the fourth As site, As(4) is bonded to one O(2), one O(9), and two equivalent O(3) atoms to form AsO4 tetrahedra that share  a cornercorner with one Ba(3)O6 pentagonal pyramid. In the fifth As site, As(5) is bonded to one O(7), one O(8), and two equivalent O(5) atoms to form AsO4 tetrahedra that share corners with two equivalent Ba(3)O6 pentagonal pyramids. In the sixth As site, As(6) is bonded to one O(17), one O(18), and two equivalent O(10) atoms to form AsO4 tetrahedra that share  an edgeedge with one Ba(3)O6 pentagonal pyramid. There are eighteen inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ba(2), one Ba(4), one Mg(1), and one As(2) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one Ba(3), two equivalent Ba(2), and one As(4) atom. In the third O site, O(3) is bonded in a 1-coordinate geometry to one Ba(1), one Ba(5), one Ba(8), and one As(4) atom. In the fourth O site, O(4) is bonded to one Ba(8), two equivalent Ba(2), and one As(2) atom to form distorted edge-sharing OBa3As tetrahedra. In the fifth O site, O(5) is bonded in a 1-coordinate geometry to one Ba(3), one Ba(8), and one As(5) atom. In the sixth O site, O(6) is bonded to one Ba(8), two equivalent Ba(1), and one As(2) atom to form a mixture of corner and edge-sharing OBa3As tetrahedra. In the seventh O site, O(7) is bonded in a distorted rectangular see-saw-like geometry to one Ba(6), two equivalent Ba(1), and one As(5) atom. In the eighth O site, O(8) is bonded to one Ba(7), two equivalent Ba(2), and one As(5) atom to form distorted edge-sharing OBa3As tetrahedra. In the ninth O site, O(9) is bonded to one Ba(4), two equivalent Ba(1), and one As(4) atom to form a mixture of distorted corner and edge-sharing OBa3As tetrahedra. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to one Ba(1), one Ba(3), one Ba(6), and one As(6) atom. In the eleventh O site, O(11) is bonded to one Ba(3), two equivalent Ba(1), and one As(1) atom to form a mixture of distorted corner and edge-sharing OBa3As tetrahedra. In the twelfth O site, O(12) is bonded to one Ba(6), two equivalent Ba(2), and one As(3) atom to form distorted edge-sharing OBa3As tetrahedra. In the thirteenth O site, O(13) is bonded in a 1-coordinate geometry to one Ba(1), one Ba(4), one Ba(7), and one As(1) atom. In the fourteenth O site, O(14) is bonded in a distorted rectangular see-saw-like geometry to one Ba(6), two equivalent Ba(1), and one As(3) atom. In the fifteenth O site, O(15) is bonded in a distorted single-bond geometry to two equivalent Ba(2) and one As(1) atom. In the sixteenth O site, O(16) is bonded in a 3-coordinate geometry to one Ba(5), one Ba(7), and one As(3) atom. In the seventeenth O site, O(17) is bonded in a 3-coordinate geometry to two equivalent Ba(2) and one As(6) atom. In the eighteenth O site, O(18) is bonded in a 4-coordinate geometry to one Ba(5), two equivalent Ba(1), and one As(6) atom. Cl(1) is bonded in a distorted single-bond geometry to one Ba(8) and one Mg(1) atom.
Ba10MgAs6(O12Cl)2 crystallizes in the monoclinic Pm space group. There are eight inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 9-coordinate geometry to one O(10), one O(11), one O(13), one O(14), one O(18), one O(3), one O(6), one O(7), and one O(9) atom. The Ba(1)-O(10) bond length is 3.10 Å. The Ba(1)-O(11) bond length is 2.83 Å. The Ba(1)-O(13) bond length is 3.38 Å. The Ba(1)-O(14) bond length is 2.76 Å. The Ba(1)-O(18) bond length is 2.81 Å. The Ba(1)-O(3) bond length is 3.15 Å. The Ba(1)-O(6) bond length is 2.64 Å. The Ba(1)-O(7) bond length is 2.84 Å. The Ba(1)-O(9) bond length is 2.76 Å. In the second Ba site, Ba(2) is bonded in a 7-coordinate geometry to one O(1), one O(12), one O(15), one O(17), one O(2), one O(4), and one O(8) atom. The Ba(2)-O(1) bond length is 2.67 Å. The Ba(2)-O(12) bond length is 2.79 Å. The Ba(2)-O(15) bond length is 2.92 Å. The Ba(2)-O(17) bond length is 2.81 Å. The Ba(2)-O(2) bond length is 2.95 Å. The Ba(2)-O(4) bond length is 2.74 Å. The Ba(2)-O(8) bond length is 2.81 Å. In the third Ba site, Ba(3) is bonded to one O(11), one O(2), two equivalent O(10), and two equivalent O(5) atoms to form distorted BaO6 pentagonal pyramids that share  a cornercorner with one As(1)O4 tetrahedra,  a cornercorner with one As(4)O4 tetrahedra, corners with two equivalent As(5)O4 tetrahedra, and  an edgeedge with one As(6)O4 tetrahedra. The Ba(3)-O(11) bond length is 2.66 Å. The Ba(3)-O(2) bond length is 2.92 Å. Both Ba(3)-O(10) bond lengths are 2.83 Å. Both Ba(3)-O(5) bond lengths are 2.66 Å. In the fourth Ba site, Ba(4) is bonded in a 5-coordinate geometry to one O(9), two equivalent O(1), and two equivalent O(13) atoms. The Ba(4)-O(9) bond length is 2.73 Å. Both Ba(4)-O(1) bond lengths are 2.67 Å. Both Ba(4)-O(13) bond lengths are 2.91 Å. In the fifth Ba site, Ba(5) is bonded in a 5-coordinate geometry to one O(18), two equivalent O(16), and two equivalent O(3) atoms. The Ba(5)-O(18) bond length is 2.56 Å. Both Ba(5)-O(16) bond lengths are 2.77 Å. Both Ba(5)-O(3) bond lengths are 2.92 Å. In the sixth Ba site, Ba(6) is bonded in a 5-coordinate geometry to one O(12), one O(14), one O(7), and two equivalent O(10) atoms. The Ba(6)-O(12) bond length is 2.78 Å. The Ba(6)-O(14) bond length is 2.75 Å. The Ba(6)-O(7) bond length is 2.79 Å. Both Ba(6)-O(10) bond lengths are 2.59 Å. In the seventh Ba site, Ba(7) is bonded in a 5-coordinate geometry to one O(8), two equivalent O(13), and two equivalent O(16) atoms. The Ba(7)-O(8) bond length is 2.61 Å. Both Ba(7)-O(13) bond lengths are 2.73 Å. Both Ba(7)-O(16) bond lengths are 2.78 Å. In the eighth Ba site, Ba(8) is bonded in a 8-coordinate geometry to one O(4), one O(6), two equivalent O(3), two equivalent O(5), and two equivalent Cl(1) atoms. The Ba(8)-O(4) bond length is 2.63 Å. The Ba(8)-O(6) bond length is 2.66 Å. Both Ba(8)-O(3) bond lengths are 2.73 Å. Both Ba(8)-O(5) bond lengths are 2.97 Å. Both Ba(8)-Cl(1) bond lengths are 3.49 Å. Mg(1) is bonded in a 4-coordinate geometry to two equivalent O(1) and two equivalent Cl(1) atoms. Both Mg(1)-O(1) bond lengths are 1.97 Å. Both Mg(1)-Cl(1) bond lengths are 2.57 Å. There are six inequivalent As sites. In the first As site, As(1) is bonded to one O(11), one O(15), and two equivalent O(13) atoms to form AsO4 tetrahedra that share  a cornercorner with one Ba(3)O6 pentagonal pyramid. The As(1)-O(11) bond length is 1.74 Å. The As(1)-O(15) bond length is 1.72 Å. Both As(1)-O(13) bond lengths are 1.74 Å. In the second As site, As(2) is bonded in a distorted rectangular see-saw-like geometry to one O(4), one O(6), and two equivalent O(1) atoms. The As(2)-O(4) bond length is 1.78 Å. The As(2)-O(6) bond length is 1.85 Å. Both As(2)-O(1) bond lengths are 2.14 Å. In the third As site, As(3) is bonded in a tetrahedral geometry to one O(12), one O(14), and two equivalent O(16) atoms. The As(3)-O(12) bond length is 1.74 Å. The As(3)-O(14) bond length is 1.73 Å. Both As(3)-O(16) bond lengths are 1.73 Å. In the fourth As site, As(4) is bonded to one O(2), one O(9), and two equivalent O(3) atoms to form AsO4 tetrahedra that share  a cornercorner with one Ba(3)O6 pentagonal pyramid. The As(4)-O(2) bond length is 1.73 Å. The As(4)-O(9) bond length is 1.74 Å. Both As(4)-O(3) bond lengths are 1.73 Å. In the fifth As site, As(5) is bonded to one O(7), one O(8), and two equivalent O(5) atoms to form AsO4 tetrahedra that share corners with two equivalent Ba(3)O6 pentagonal pyramids. The As(5)-O(7) bond length is 1.74 Å. The As(5)-O(8) bond length is 1.73 Å. Both As(5)-O(5) bond lengths are 1.72 Å. In the sixth As site, As(6) is bonded to one O(17), one O(18), and two equivalent O(10) atoms to form AsO4 tetrahedra that share  an edgeedge with one Ba(3)O6 pentagonal pyramid. The As(6)-O(17) bond length is 1.71 Å. The As(6)-O(18) bond length is 1.74 Å. Both As(6)-O(10) bond lengths are 1.73 Å. There are eighteen inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ba(2), one Ba(4), one Mg(1), and one As(2) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one Ba(3), two equivalent Ba(2), and one As(4) atom. In the third O site, O(3) is bonded in a 1-coordinate geometry to one Ba(1), one Ba(5), one Ba(8), and one As(4) atom. In the fourth O site, O(4) is bonded to one Ba(8), two equivalent Ba(2), and one As(2) atom to form distorted edge-sharing OBa3As tetrahedra. In the fifth O site, O(5) is bonded in a 1-coordinate geometry to one Ba(3), one Ba(8), and one As(5) atom. In the sixth O site, O(6) is bonded to one Ba(8), two equivalent Ba(1), and one As(2) atom to form a mixture of corner and edge-sharing OBa3As tetrahedra. In the seventh O site, O(7) is bonded in a distorted rectangular see-saw-like geometry to one Ba(6), two equivalent Ba(1), and one As(5) atom. In the eighth O site, O(8) is bonded to one Ba(7), two equivalent Ba(2), and one As(5) atom to form distorted edge-sharing OBa3As tetrahedra. In the ninth O site, O(9) is bonded to one Ba(4), two equivalent Ba(1), and one As(4) atom to form a mixture of distorted corner and edge-sharing OBa3As tetrahedra. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to one Ba(1), one Ba(3), one Ba(6), and one As(6) atom. In the eleventh O site, O(11) is bonded to one Ba(3), two equivalent Ba(1), and one As(1) atom to form a mixture of distorted corner and edge-sharing OBa3As tetrahedra. In the twelfth O site, O(12) is bonded to one Ba(6), two equivalent Ba(2), and one As(3) atom to form distorted edge-sharing OBa3As tetrahedra. In the thirteenth O site, O(13) is bonded in a 1-coordinate geometry to one Ba(1), one Ba(4), one Ba(7), and one As(1) atom. In the fourteenth O site, O(14) is bonded in a distorted rectangular see-saw-like geometry to one Ba(6), two equivalent Ba(1), and one As(3) atom. In the fifteenth O site, O(15) is bonded in a distorted single-bond geometry to two equivalent Ba(2) and one As(1) atom. In the sixteenth O site, O(16) is bonded in a 3-coordinate geometry to one Ba(5), one Ba(7), and one As(3) atom. In the seventeenth O site, O(17) is bonded in a 3-coordinate geometry to two equivalent Ba(2) and one As(6) atom. In the eighteenth O site, O(18) is bonded in a 4-coordinate geometry to one Ba(5), two equivalent Ba(1), and one As(6) atom. Cl(1) is bonded in a distorted single-bond geometry to one Ba(8) and one Mg(1) atom.