Ba10MgAs6(O12Cl)2 crystallizes in the triclinic P1 space group. There are ten inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 8-coordinate geometry to one O(12), one O(15), one O(18), one O(24), 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 9-coordinate geometry to one O(13), one O(19), one O(2), one O(21), one O(22), one O(23), one O(4), one O(5), and one O(8) atom. In the third Ba site, Ba(3) is bonded in a 7-coordinate geometry to one O(10), one O(11), one O(12), one O(17), one O(18), one O(5), and one Cl(1) atom. In the fourth Ba site, Ba(4) is bonded in a 8-coordinate geometry to one O(1), one O(11), one O(13), one O(19), one O(2), one O(20), one O(4), and one O(8) atom. In the fifth Ba site, Ba(5) is bonded in a 7-coordinate geometry to one O(1), one O(14), one O(15), one O(2), one O(23), one O(9), and one Cl(1) atom. In the sixth Ba site, Ba(6) is bonded in a 9-coordinate geometry to one O(17), one O(19), one O(20), one O(21), one O(22), one O(24), one O(3), one Cl(1), and one Cl(2) atom. In the seventh Ba site, Ba(7) is bonded in a 7-coordinate geometry to one O(10), one O(13), one O(18), one O(21), one O(23), one O(7), and one Cl(2) atom. In the eighth Ba site, Ba(8) is bonded in a 8-coordinate geometry to one O(14), one O(15), one O(20), one O(22), one O(6), one O(8), one Cl(1), and one Cl(2) atom. In the ninth Ba site, Ba(9) is bonded in a 8-coordinate geometry to one O(10), one O(12), one O(14), one O(16), one O(24), one O(6), one O(7), and one O(9) atom. In the tenth Ba site, Ba(10) is bonded in a 7-coordinate geometry to one O(11), one O(16), one O(17), one O(3), one O(4), one O(5), and one Cl(2) atom. Mg(1) is bonded in a 3-coordinate geometry to one As(6), one O(1), one O(10), and one O(13) atom. There are six inequivalent As sites. In the first As site, As(1) is bonded in a tetrahedral geometry to one O(12), one O(14), one O(15), and one O(19) atom. In the second As site, As(2) is bonded in a tetrahedral geometry to one O(1), one O(23), one O(4), and one O(6) atom. In the third As site, As(3) is bonded in a tetrahedral geometry to one O(13), one O(16), one O(20), and one O(22) atom. In the fourth As site, As(4) is bonded in a tetrahedral geometry to one O(17), one O(2), one O(3), and one O(9) atom. In the fifth As site, As(5) is bonded in a tetrahedral geometry to one O(11), one O(5), one O(7), and one O(8) atom. In the sixth As site, As(6) is bonded in a 4-coordinate geometry to one Mg(1), one O(18), one O(21), and one O(24) atom. There are twenty-four inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ba(4), one Ba(5), one Mg(1), and one As(2) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Ba(2), one Ba(4), one Ba(5), and one As(4) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Ba(1), one Ba(10), one Ba(6), and one As(4) atom. In the fourth O site, O(4) is bonded in a distorted tetrahedral geometry to one Ba(10), one Ba(2), one Ba(4), and one As(2) atom. In the fifth O site, O(5) is bonded in a distorted single-bond geometry to one Ba(10), one Ba(2), one Ba(3), and one As(5) atom. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to one Ba(1), one Ba(8), one Ba(9), and one As(2) atom. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one Ba(1), one Ba(7), one Ba(9), and one As(5) atom. In the eighth O site, O(8) is bonded in a 4-coordinate geometry to one Ba(2), one Ba(4), one Ba(8), and one As(5) atom. In the ninth O site, O(9) is bonded to one Ba(1), one Ba(5), one Ba(9), and one As(4) atom to form distorted OBa3As tetrahedra that share  a cornercorner with one Cl(1)Ba4 trigonal pyramid and  an edgeedge with one O(12)Ba3As trigonal pyramid. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to one Ba(3), one Ba(7), one Ba(9), and one Mg(1) atom. In the eleventh O site, O(11) is bonded in a 4-coordinate geometry to one Ba(10), one Ba(3), one Ba(4), and one As(5) atom. In the twelfth O site, O(12) is bonded to one Ba(1), one Ba(3), one Ba(9), and one As(1) atom to form distorted OBa3As trigonal pyramids that share  a cornercorner with one Cl(1)Ba4 trigonal pyramid and  an edgeedge with one O(9)Ba3As tetrahedra. In the thirteenth O site, O(13) is bonded in a 2-coordinate geometry to one Ba(2), one Ba(4), one Ba(7), one Mg(1), and one As(3) atom. In the fourteenth O site, O(14) is bonded in a distorted single-bond geometry to one Ba(5), one Ba(8), one Ba(9), and one As(1) atom. In the fifteenth O site, O(15) is bonded in a 4-coordinate geometry to one Ba(1), one Ba(5), one Ba(8), and one As(1) atom. In the sixteenth O site, O(16) is bonded in a distorted trigonal non-coplanar geometry to one Ba(10), one Ba(9), and one As(3) atom. In the seventeenth O site, O(17) is bonded in a distorted single-bond geometry to one Ba(10), one Ba(3), one Ba(6), and one As(4) atom. In the eighteenth O site, O(18) is bonded in a 4-coordinate geometry to one Ba(1), one Ba(3), one Ba(7), and one As(6) atom. In the nineteenth O site, O(19) is bonded in a 4-coordinate geometry to one Ba(2), one Ba(4), one Ba(6), and one As(1) atom. In the twentieth O site, O(20) is bonded in a 4-coordinate geometry to one Ba(4), one Ba(6), one Ba(8), and one As(3) atom. In the twenty-first O site, O(21) is bonded in a 4-coordinate geometry to one Ba(2), one Ba(6), one Ba(7), and one As(6) atom. In the twenty-second O site, O(22) is bonded in a distorted single-bond geometry to one Ba(2), one Ba(6), one Ba(8), and one As(3) atom. In the twenty-third O site, O(23) is bonded in a distorted single-bond geometry to one Ba(2), one Ba(5), one Ba(7), and one As(2) atom. In the twenty-fourth O site, O(24) is bonded in a 4-coordinate geometry to one Ba(1), one Ba(6), one Ba(9), and one As(6) atom. There are two inequivalent Cl sites. In the first Cl site, Cl(1) is bonded to one Ba(3), one Ba(5), one Ba(6), and one Ba(8) atom to form distorted ClBa4 trigonal pyramids that share  a cornercorner with one O(9)Ba3As tetrahedra and  a cornercorner with one O(12)Ba3As trigonal pyramid. In the second Cl site, Cl(2) is bonded in a 4-coordinate geometry to one Ba(10), one Ba(6), one Ba(7), and one Ba(8) atom.
Ba10MgAs6(O12Cl)2 crystallizes in the triclinic P1 space group. There are ten inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 8-coordinate geometry to one O(12), one O(15), one O(18), one O(24), one O(3), one O(6), one O(7), and one O(9) atom. The Ba(1)-O(12) bond length is 2.82 Å. The Ba(1)-O(15) bond length is 2.93 Å. The Ba(1)-O(18) bond length is 2.91 Å. The Ba(1)-O(24) bond length is 2.75 Å. The Ba(1)-O(3) bond length is 2.99 Å. The Ba(1)-O(6) bond length is 3.03 Å. The Ba(1)-O(7) bond length is 2.69 Å. The Ba(1)-O(9) bond length is 2.76 Å. In the second Ba site, Ba(2) is bonded in a 9-coordinate geometry to one O(13), one O(19), one O(2), one O(21), one O(22), one O(23), one O(4), one O(5), and one O(8) atom. The Ba(2)-O(13) bond length is 2.95 Å. The Ba(2)-O(19) bond length is 2.79 Å. The Ba(2)-O(2) bond length is 2.71 Å. The Ba(2)-O(21) bond length is 2.66 Å. The Ba(2)-O(22) bond length is 2.80 Å. The Ba(2)-O(23) bond length is 3.42 Å. The Ba(2)-O(4) bond length is 2.79 Å. The Ba(2)-O(5) bond length is 3.20 Å. The Ba(2)-O(8) bond length is 2.77 Å. In the third Ba site, Ba(3) is bonded in a 7-coordinate geometry to one O(10), one O(11), one O(12), one O(17), one O(18), one O(5), and one Cl(1) atom. The Ba(3)-O(10) bond length is 2.65 Å. The Ba(3)-O(11) bond length is 2.77 Å. The Ba(3)-O(12) bond length is 2.65 Å. The Ba(3)-O(17) bond length is 2.97 Å. The Ba(3)-O(18) bond length is 2.73 Å. The Ba(3)-O(5) bond length is 3.21 Å. The Ba(3)-Cl(1) bond length is 3.07 Å. In the fourth Ba site, Ba(4) is bonded in a 8-coordinate geometry to one O(1), one O(11), one O(13), one O(19), one O(2), one O(20), one O(4), and one O(8) atom. The Ba(4)-O(1) bond length is 3.04 Å. The Ba(4)-O(11) bond length is 2.80 Å. The Ba(4)-O(13) bond length is 3.04 Å. The Ba(4)-O(19) bond length is 2.74 Å. The Ba(4)-O(2) bond length is 2.89 Å. The Ba(4)-O(20) bond length is 3.07 Å. The Ba(4)-O(4) bond length is 2.83 Å. The Ba(4)-O(8) bond length is 2.75 Å. In the fifth Ba site, Ba(5) is bonded in a 7-coordinate geometry to one O(1), one O(14), one O(15), one O(2), one O(23), one O(9), and one Cl(1) atom. The Ba(5)-O(1) bond length is 2.76 Å. The Ba(5)-O(14) bond length is 2.87 Å. The Ba(5)-O(15) bond length is 2.71 Å. The Ba(5)-O(2) bond length is 3.08 Å. The Ba(5)-O(23) bond length is 2.98 Å. The Ba(5)-O(9) bond length is 2.66 Å. The Ba(5)-Cl(1) bond length is 3.19 Å. In the sixth Ba site, Ba(6) is bonded in a 9-coordinate geometry to one O(17), one O(19), one O(20), one O(21), one O(22), one O(24), one O(3), one Cl(1), and one Cl(2) atom. The Ba(6)-O(17) bond length is 3.46 Å. The Ba(6)-O(19) bond length is 2.97 Å. The Ba(6)-O(20) bond length is 2.75 Å. The Ba(6)-O(21) bond length is 3.29 Å. The Ba(6)-O(22) bond length is 3.02 Å. The Ba(6)-O(24) bond length is 2.62 Å. The Ba(6)-O(3) bond length is 3.02 Å. The Ba(6)-Cl(1) bond length is 3.29 Å. The Ba(6)-Cl(2) bond length is 3.36 Å. In the seventh Ba site, Ba(7) is bonded in a 7-coordinate geometry to one O(10), one O(13), one O(18), one O(21), one O(23), one O(7), and one Cl(2) atom. The Ba(7)-O(10) bond length is 2.55 Å. The Ba(7)-O(13) bond length is 3.11 Å. The Ba(7)-O(18) bond length is 2.54 Å. The Ba(7)-O(21) bond length is 2.98 Å. The Ba(7)-O(23) bond length is 2.85 Å. The Ba(7)-O(7) bond length is 2.96 Å. The Ba(7)-Cl(2) bond length is 3.08 Å. In the eighth Ba site, Ba(8) is bonded in a 8-coordinate geometry to one O(14), one O(15), one O(20), one O(22), one O(6), one O(8), one Cl(1), and one Cl(2) atom. The Ba(8)-O(14) bond length is 2.90 Å. The Ba(8)-O(15) bond length is 2.89 Å. The Ba(8)-O(20) bond length is 2.92 Å. The Ba(8)-O(22) bond length is 2.88 Å. The Ba(8)-O(6) bond length is 3.08 Å. The Ba(8)-O(8) bond length is 2.64 Å. The Ba(8)-Cl(1) bond length is 3.28 Å. The Ba(8)-Cl(2) bond length is 3.31 Å. In the ninth Ba site, Ba(9) is bonded in a 8-coordinate geometry to one O(10), one O(12), one O(14), one O(16), one O(24), one O(6), one O(7), and one O(9) atom. The Ba(9)-O(10) bond length is 2.73 Å. The Ba(9)-O(12) bond length is 2.78 Å. The Ba(9)-O(14) bond length is 3.09 Å. The Ba(9)-O(16) bond length is 2.69 Å. The Ba(9)-O(24) bond length is 2.98 Å. The Ba(9)-O(6) bond length is 3.12 Å. The Ba(9)-O(7) bond length is 2.78 Å. The Ba(9)-O(9) bond length is 2.78 Å. In the tenth Ba site, Ba(10) is bonded in a 7-coordinate geometry to one O(11), one O(16), one O(17), one O(3), one O(4), one O(5), and one Cl(2) atom. The Ba(10)-O(11) bond length is 2.84 Å. The Ba(10)-O(16) bond length is 2.96 Å. The Ba(10)-O(17) bond length is 2.88 Å. The Ba(10)-O(3) bond length is 2.77 Å. The Ba(10)-O(4) bond length is 2.66 Å. The Ba(10)-O(5) bond length is 2.89 Å. The Ba(10)-Cl(2) bond length is 3.18 Å. Mg(1) is bonded in a 3-coordinate geometry to one As(6), one O(1), one O(10), and one O(13) atom. The Mg(1)-As(6) bond length is 2.57 Å. The Mg(1)-O(1) bond length is 2.00 Å. The Mg(1)-O(10) bond length is 1.90 Å. The Mg(1)-O(13) bond length is 2.04 Å. There are six inequivalent As sites. In the first As site, As(1) is bonded in a tetrahedral geometry to one O(12), one O(14), one O(15), and one O(19) atom. The As(1)-O(12) bond length is 1.72 Å. The As(1)-O(14) bond length is 1.72 Å. The As(1)-O(15) bond length is 1.74 Å. The As(1)-O(19) bond length is 1.73 Å. In the second As site, As(2) is bonded in a tetrahedral geometry to one O(1), one O(23), one O(4), and one O(6) atom. The As(2)-O(1) bond length is 1.77 Å. The As(2)-O(23) bond length is 1.73 Å. The As(2)-O(4) bond length is 1.72 Å. The As(2)-O(6) bond length is 1.71 Å. In the third As site, As(3) is bonded in a tetrahedral geometry to one O(13), one O(16), one O(20), and one O(22) atom. The As(3)-O(13) bond length is 1.77 Å. The As(3)-O(16) bond length is 1.72 Å. The As(3)-O(20) bond length is 1.73 Å. The As(3)-O(22) bond length is 1.72 Å. In the fourth As site, As(4) is bonded in a tetrahedral geometry to one O(17), one O(2), one O(3), and one O(9) atom. The As(4)-O(17) bond length is 1.71 Å. The As(4)-O(2) bond length is 1.75 Å. The As(4)-O(3) bond length is 1.74 Å. The As(4)-O(9) bond length is 1.74 Å. In the fifth As site, As(5) is bonded in a tetrahedral geometry to one O(11), one O(5), one O(7), and one O(8) atom. The As(5)-O(11) bond length is 1.74 Å. The As(5)-O(5) bond length is 1.71 Å. The As(5)-O(7) bond length is 1.72 Å. The As(5)-O(8) bond length is 1.74 Å. In the sixth As site, As(6) is bonded in a 4-coordinate geometry to one Mg(1), one O(18), one O(21), and one O(24) atom. The As(6)-O(18) bond length is 1.77 Å. The As(6)-O(21) bond length is 1.77 Å. The As(6)-O(24) bond length is 1.77 Å. There are twenty-four inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ba(4), one Ba(5), one Mg(1), and one As(2) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Ba(2), one Ba(4), one Ba(5), and one As(4) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Ba(1), one Ba(10), one Ba(6), and one As(4) atom. In the fourth O site, O(4) is bonded in a distorted tetrahedral geometry to one Ba(10), one Ba(2), one Ba(4), and one As(2) atom. In the fifth O site, O(5) is bonded in a distorted single-bond geometry to one Ba(10), one Ba(2), one Ba(3), and one As(5) atom. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to one Ba(1), one Ba(8), one Ba(9), and one As(2) atom. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one Ba(1), one Ba(7), one Ba(9), and one As(5) atom. In the eighth O site, O(8) is bonded in a 4-coordinate geometry to one Ba(2), one Ba(4), one Ba(8), and one As(5) atom. In the ninth O site, O(9) is bonded to one Ba(1), one Ba(5), one Ba(9), and one As(4) atom to form distorted OBa3As tetrahedra that share  a cornercorner with one Cl(1)Ba4 trigonal pyramid and  an edgeedge with one O(12)Ba3As trigonal pyramid. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to one Ba(3), one Ba(7), one Ba(9), and one Mg(1) atom. In the eleventh O site, O(11) is bonded in a 4-coordinate geometry to one Ba(10), one Ba(3), one Ba(4), and one As(5) atom. In the twelfth O site, O(12) is bonded to one Ba(1), one Ba(3), one Ba(9), and one As(1) atom to form distorted OBa3As trigonal pyramids that share  a cornercorner with one Cl(1)Ba4 trigonal pyramid and  an edgeedge with one O(9)Ba3As tetrahedra. In the thirteenth O site, O(13) is bonded in a 2-coordinate geometry to one Ba(2), one Ba(4), one Ba(7), one Mg(1), and one As(3) atom. In the fourteenth O site, O(14) is bonded in a distorted single-bond geometry to one Ba(5), one Ba(8), one Ba(9), and one As(1) atom. In the fifteenth O site, O(15) is bonded in a 4-coordinate geometry to one Ba(1), one Ba(5), one Ba(8), and one As(1) atom. In the sixteenth O site, O(16) is bonded in a distorted trigonal non-coplanar geometry to one Ba(10), one Ba(9), and one As(3) atom. In the seventeenth O site, O(17) is bonded in a distorted single-bond geometry to one Ba(10), one Ba(3), one Ba(6), and one As(4) atom. In the eighteenth O site, O(18) is bonded in a 4-coordinate geometry to one Ba(1), one Ba(3), one Ba(7), and one As(6) atom. In the nineteenth O site, O(19) is bonded in a 4-coordinate geometry to one Ba(2), one Ba(4), one Ba(6), and one As(1) atom. In the twentieth O site, O(20) is bonded in a 4-coordinate geometry to one Ba(4), one Ba(6), one Ba(8), and one As(3) atom. In the twenty-first O site, O(21) is bonded in a 4-coordinate geometry to one Ba(2), one Ba(6), one Ba(7), and one As(6) atom. In the twenty-second O site, O(22) is bonded in a distorted single-bond geometry to one Ba(2), one Ba(6), one Ba(8), and one As(3) atom. In the twenty-third O site, O(23) is bonded in a distorted single-bond geometry to one Ba(2), one Ba(5), one Ba(7), and one As(2) atom. In the twenty-fourth O site, O(24) is bonded in a 4-coordinate geometry to one Ba(1), one Ba(6), one Ba(9), and one As(6) atom. There are two inequivalent Cl sites. In the first Cl site, Cl(1) is bonded to one Ba(3), one Ba(5), one Ba(6), and one Ba(8) atom to form distorted ClBa4 trigonal pyramids that share  a cornercorner with one O(9)Ba3As tetrahedra and  a cornercorner with one O(12)Ba3As trigonal pyramid. In the second Cl site, Cl(2) is bonded in a 4-coordinate geometry to one Ba(10), one Ba(6), one Ba(7), and one Ba(8) atom.