Mg3(AsO4)2 crystallizes in the triclinic P1 space group. There are nine inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 5-coordinate geometry to one O(10), one O(2), one O(20), one O(3), and one O(6) atom. In the second Mg site, Mg(2) is bonded to one O(13), one O(22), one O(3), one O(6), and one O(8) atom to form distorted MgO5 trigonal bipyramids that share  a cornercorner with one O(5)Mg2AsO tetrahedra,  a cornercorner with one Mg(3)O5 trigonal bipyramid,  an edgeedge with one As(5)O6 octahedra, and  an edgeedge with one Mg(6)O5 trigonal bipyramid. In the third Mg site, Mg(3) is bonded to one O(11), one O(12), one O(16), one O(18), and one O(6) atom to form distorted corner-sharing MgO5 trigonal bipyramids. In the fourth Mg site, Mg(4) is bonded in a 7-coordinate geometry to one O(12), one O(14), one O(15), one O(17), one O(19), one O(21), and one O(9) atom. In the fifth Mg site, Mg(5) is bonded in a 6-coordinate geometry to one O(1), one O(11), one O(16), one O(24), one O(3), and one O(9) atom. In the sixth Mg site, Mg(6) is bonded to one O(10), one O(13), one O(23), one O(7), and one O(8) atom to form distorted MgO5 trigonal bipyramids that share  a cornercorner with one O(5)Mg2AsO tetrahedra,  a cornercorner with one O(16)Mg3O trigonal pyramid, and  an edgeedge with one Mg(2)O5 trigonal bipyramid. In the seventh Mg site, Mg(7) is bonded to one O(14), one O(17), one O(18), one O(2), and one O(20) atom to form distorted MgO5 tetrahedra that share  a cornercorner with one As(5)O6 octahedra and  a cornercorner with one Mg(3)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 10°. In the eighth Mg site, Mg(8) is bonded to one O(1), one O(15), one O(19), one O(24), and one O(5) atom to form distorted MgO5 tetrahedra that share  an edgeedge with one As(5)O6 octahedra. In the ninth Mg site, Mg(9) is bonded in a 5-coordinate geometry to one O(16), one O(17), one O(22), one O(23), one O(5), and one O(7) atom. There are six inequivalent As sites. In the first As site, As(1) is bonded in a distorted trigonal non-coplanar geometry to one O(10), one O(2), and one O(9) atom. In the second As site, As(2) is bonded in a distorted T-shaped geometry to one O(11), one O(19), and one O(4) atom. In the third As site, As(3) is bonded in a 3-coordinate geometry to one O(13), one O(18), and one O(20) atom. In the fourth As site, As(4) is bonded in a 4-coordinate geometry to one O(12), one O(2), one O(5), and one O(7) atom. In the fifth As site, As(5) is bonded to one O(1), one O(15), one O(20), one O(21), one O(22), and one O(3) atom to form distorted AsO6 octahedra that share  a cornercorner with one Mg(7)O5 tetrahedra,  a cornercorner with one O(17)Mg3O tetrahedra,  an edgeedge with one Mg(8)O5 tetrahedra, and  an edgeedge with one Mg(2)O5 trigonal bipyramid. In the sixth As site, As(6) is bonded in a distorted water-like geometry to one O(14), one O(23), and one O(24) atom. There are twenty-four inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Mg(5), one Mg(8), and one As(5) atom. In the second O site, O(2) is bonded to one Mg(1), one Mg(7), one As(1), and one As(4) atom to form distorted OMg2As2 tetrahedra that share  a cornercorner with one O(5)Mg2AsO tetrahedra,  a cornercorner with one O(17)Mg3O tetrahedra, and  a cornercorner with one O(3)Mg3As trigonal pyramid. In the third O site, O(3) is bonded to one Mg(1), one Mg(2), one Mg(5), and one As(5) atom to form OMg3As trigonal pyramids that share  a cornercorner with one O(2)Mg2As2 tetrahedra and  a cornercorner with one O(16)Mg3O trigonal pyramid. In the fourth O site, O(4) is bonded in a 1-coordinate geometry to one As(2) and one O(6) atom. In the fifth O site, O(5) is bonded to one Mg(8), one Mg(9), one As(4), and one O(8) atom to form distorted OMg2AsO tetrahedra that share  a cornercorner with one O(2)Mg2As2 tetrahedra,  a cornercorner with one O(17)Mg3O tetrahedra,  a cornercorner with one Mg(2)O5 trigonal bipyramid,  a cornercorner with one Mg(6)O5 trigonal bipyramid, and  a cornercorner with one O(16)Mg3O trigonal pyramid. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), and one O(4) atom. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one Mg(6), one Mg(9), one As(4), and one O(16) atom. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Mg(2), one Mg(6), and one O(5) atom. In the ninth O site, O(9) is bonded in a trigonal planar geometry to one Mg(4), one Mg(5), and one As(1) atom. In the tenth O site, O(10) is bonded in a trigonal planar geometry to one Mg(1), one Mg(6), and one As(1) atom. In the eleventh O site, O(11) is bonded in a distorted trigonal non-coplanar geometry to one Mg(3), one Mg(5), and one As(2) atom. In the twelfth O site, O(12) is bonded in a 2-coordinate geometry to one Mg(3), one Mg(4), and one As(4) atom. In the thirteenth O site, O(13) is bonded in a distorted trigonal planar geometry to one Mg(2), one Mg(6), and one As(3) atom. In the fourteenth O site, O(14) is bonded in a distorted T-shaped geometry to one Mg(4), one Mg(7), and one As(6) atom. In the fifteenth O site, O(15) is bonded in a 4-coordinate geometry to one Mg(4), one Mg(8), one As(5), and one O(24) atom. In the sixteenth O site, O(16) is bonded to one Mg(3), one Mg(5), one Mg(9), and one O(7) atom to form distorted OMg3O trigonal pyramids that share  a cornercorner with one O(5)Mg2AsO tetrahedra,  a cornercorner with one O(17)Mg3O tetrahedra,  a cornercorner with one Mg(6)O5 trigonal bipyramid, and  a cornercorner with one O(3)Mg3As trigonal pyramid. In the seventeenth O site, O(17) is bonded to one Mg(4), one Mg(7), one Mg(9), and one O(21) atom to form distorted OMg3O tetrahedra that share  a cornercorner with one As(5)O6 octahedra,  a cornercorner with one O(2)Mg2As2 tetrahedra,  a cornercorner with one O(5)Mg2AsO tetrahedra, and  a cornercorner with one O(16)Mg3O trigonal pyramid. The corner-sharing octahedral tilt angles are 69°. In the eighteenth O site, O(18) is bonded in a trigonal planar geometry to one Mg(3), one Mg(7), and one As(3) atom. In the nineteenth O site, O(19) is bonded in a trigonal non-coplanar geometry to one Mg(4), one Mg(8), and one As(2) atom. In the twentieth O site, O(20) is bonded in a 4-coordinate geometry to one Mg(1), one Mg(7), one As(3), and one As(5) atom. In the twenty-first O site, O(21) is bonded in a 3-coordinate geometry to one Mg(4), one As(5), and one O(17) atom. In the twenty-second O site, O(22) is bonded in a 3-coordinate geometry to one Mg(2), one Mg(9), and one As(5) atom. In the twenty-third O site, O(23) is bonded in a distorted trigonal planar geometry to one Mg(6), one Mg(9), and one As(6) atom. In the twenty-fourth O site, O(24) is bonded in a 4-coordinate geometry to one Mg(5), one Mg(8), one As(6), and one O(15) atom.
Mg3(AsO4)2 crystallizes in the triclinic P1 space group. There are nine inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 5-coordinate geometry to one O(10), one O(2), one O(20), one O(3), and one O(6) atom. The Mg(1)-O(10) bond length is 2.03 Å. The Mg(1)-O(2) bond length is 2.11 Å. The Mg(1)-O(20) bond length is 2.14 Å. The Mg(1)-O(3) bond length is 2.34 Å. The Mg(1)-O(6) bond length is 2.03 Å. In the second Mg site, Mg(2) is bonded to one O(13), one O(22), one O(3), one O(6), and one O(8) atom to form distorted MgO5 trigonal bipyramids that share  a cornercorner with one O(5)Mg2AsO tetrahedra,  a cornercorner with one Mg(3)O5 trigonal bipyramid,  an edgeedge with one As(5)O6 octahedra, and  an edgeedge with one Mg(6)O5 trigonal bipyramid. The Mg(2)-O(13) bond length is 2.09 Å. The Mg(2)-O(22) bond length is 2.16 Å. The Mg(2)-O(3) bond length is 2.01 Å. The Mg(2)-O(6) bond length is 2.08 Å. The Mg(2)-O(8) bond length is 2.09 Å. In the third Mg site, Mg(3) is bonded to one O(11), one O(12), one O(16), one O(18), and one O(6) atom to form distorted corner-sharing MgO5 trigonal bipyramids. The Mg(3)-O(11) bond length is 1.98 Å. The Mg(3)-O(12) bond length is 2.04 Å. The Mg(3)-O(16) bond length is 2.03 Å. The Mg(3)-O(18) bond length is 1.94 Å. The Mg(3)-O(6) bond length is 2.04 Å. In the fourth Mg site, Mg(4) is bonded in a 7-coordinate geometry to one O(12), one O(14), one O(15), one O(17), one O(19), one O(21), and one O(9) atom. The Mg(4)-O(12) bond length is 2.52 Å. The Mg(4)-O(14) bond length is 2.25 Å. The Mg(4)-O(15) bond length is 2.22 Å. The Mg(4)-O(17) bond length is 2.12 Å. The Mg(4)-O(19) bond length is 2.04 Å. The Mg(4)-O(21) bond length is 2.44 Å. The Mg(4)-O(9) bond length is 2.01 Å. In the fifth Mg site, Mg(5) is bonded in a 6-coordinate geometry to one O(1), one O(11), one O(16), one O(24), one O(3), and one O(9) atom. The Mg(5)-O(1) bond length is 2.19 Å. The Mg(5)-O(11) bond length is 2.21 Å. The Mg(5)-O(16) bond length is 2.53 Å. The Mg(5)-O(24) bond length is 2.23 Å. The Mg(5)-O(3) bond length is 2.20 Å. The Mg(5)-O(9) bond length is 2.13 Å. In the sixth Mg site, Mg(6) is bonded to one O(10), one O(13), one O(23), one O(7), and one O(8) atom to form distorted MgO5 trigonal bipyramids that share  a cornercorner with one O(5)Mg2AsO tetrahedra,  a cornercorner with one O(16)Mg3O trigonal pyramid, and  an edgeedge with one Mg(2)O5 trigonal bipyramid. The Mg(6)-O(10) bond length is 1.99 Å. The Mg(6)-O(13) bond length is 2.07 Å. The Mg(6)-O(23) bond length is 2.08 Å. The Mg(6)-O(7) bond length is 2.05 Å. The Mg(6)-O(8) bond length is 2.29 Å. In the seventh Mg site, Mg(7) is bonded to one O(14), one O(17), one O(18), one O(2), and one O(20) atom to form distorted MgO5 tetrahedra that share  a cornercorner with one As(5)O6 octahedra and  a cornercorner with one Mg(3)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 10°. The Mg(7)-O(14) bond length is 2.00 Å. The Mg(7)-O(17) bond length is 2.05 Å. The Mg(7)-O(18) bond length is 1.92 Å. The Mg(7)-O(2) bond length is 1.97 Å. The Mg(7)-O(20) bond length is 2.71 Å. In the eighth Mg site, Mg(8) is bonded to one O(1), one O(15), one O(19), one O(24), and one O(5) atom to form distorted MgO5 tetrahedra that share  an edgeedge with one As(5)O6 octahedra. The Mg(8)-O(1) bond length is 1.92 Å. The Mg(8)-O(15) bond length is 2.39 Å. The Mg(8)-O(19) bond length is 1.97 Å. The Mg(8)-O(24) bond length is 2.03 Å. The Mg(8)-O(5) bond length is 2.09 Å. In the ninth Mg site, Mg(9) is bonded in a 5-coordinate geometry to one O(16), one O(17), one O(22), one O(23), one O(5), and one O(7) atom. The Mg(9)-O(16) bond length is 2.04 Å. The Mg(9)-O(17) bond length is 2.17 Å. The Mg(9)-O(22) bond length is 1.94 Å. The Mg(9)-O(23) bond length is 2.15 Å. The Mg(9)-O(5) bond length is 2.13 Å. The Mg(9)-O(7) bond length is 2.51 Å. There are six inequivalent As sites. In the first As site, As(1) is bonded in a distorted trigonal non-coplanar geometry to one O(10), one O(2), and one O(9) atom. The As(1)-O(10) bond length is 1.81 Å. The As(1)-O(2) bond length is 1.85 Å. The As(1)-O(9) bond length is 1.79 Å. In the second As site, As(2) is bonded in a distorted T-shaped geometry to one O(11), one O(19), and one O(4) atom. The As(2)-O(11) bond length is 1.79 Å. The As(2)-O(19) bond length is 1.76 Å. The As(2)-O(4) bond length is 1.91 Å. In the third As site, As(3) is bonded in a 3-coordinate geometry to one O(13), one O(18), and one O(20) atom. The As(3)-O(13) bond length is 1.82 Å. The As(3)-O(18) bond length is 1.79 Å. The As(3)-O(20) bond length is 2.20 Å. In the fourth As site, As(4) is bonded in a 4-coordinate geometry to one O(12), one O(2), one O(5), and one O(7) atom. The As(4)-O(12) bond length is 1.72 Å. The As(4)-O(2) bond length is 2.36 Å. The As(4)-O(5) bond length is 2.31 Å. The As(4)-O(7) bond length is 2.04 Å. In the fifth As site, As(5) is bonded to one O(1), one O(15), one O(20), one O(21), one O(22), and one O(3) atom to form distorted AsO6 octahedra that share  a cornercorner with one Mg(7)O5 tetrahedra,  a cornercorner with one O(17)Mg3O tetrahedra,  an edgeedge with one Mg(8)O5 tetrahedra, and  an edgeedge with one Mg(2)O5 trigonal bipyramid. The As(5)-O(1) bond length is 1.82 Å. The As(5)-O(15) bond length is 2.25 Å. The As(5)-O(20) bond length is 1.85 Å. The As(5)-O(21) bond length is 1.96 Å. The As(5)-O(22) bond length is 1.82 Å. The As(5)-O(3) bond length is 1.85 Å. In the sixth As site, As(6) is bonded in a distorted water-like geometry to one O(14), one O(23), and one O(24) atom. The As(6)-O(14) bond length is 1.76 Å. The As(6)-O(23) bond length is 1.74 Å. The As(6)-O(24) bond length is 2.49 Å. There are twenty-four inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Mg(5), one Mg(8), and one As(5) atom. In the second O site, O(2) is bonded to one Mg(1), one Mg(7), one As(1), and one As(4) atom to form distorted OMg2As2 tetrahedra that share  a cornercorner with one O(5)Mg2AsO tetrahedra,  a cornercorner with one O(17)Mg3O tetrahedra, and  a cornercorner with one O(3)Mg3As trigonal pyramid. In the third O site, O(3) is bonded to one Mg(1), one Mg(2), one Mg(5), and one As(5) atom to form OMg3As trigonal pyramids that share  a cornercorner with one O(2)Mg2As2 tetrahedra and  a cornercorner with one O(16)Mg3O trigonal pyramid. In the fourth O site, O(4) is bonded in a 1-coordinate geometry to one As(2) and one O(6) atom. The O(4)-O(6) bond length is 1.50 Å. In the fifth O site, O(5) is bonded to one Mg(8), one Mg(9), one As(4), and one O(8) atom to form distorted OMg2AsO tetrahedra that share  a cornercorner with one O(2)Mg2As2 tetrahedra,  a cornercorner with one O(17)Mg3O tetrahedra,  a cornercorner with one Mg(2)O5 trigonal bipyramid,  a cornercorner with one Mg(6)O5 trigonal bipyramid, and  a cornercorner with one O(16)Mg3O trigonal pyramid. The O(5)-O(8) bond length is 1.50 Å. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), and one O(4) atom. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one Mg(6), one Mg(9), one As(4), and one O(16) atom. The O(7)-O(16) bond length is 1.50 Å. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Mg(2), one Mg(6), and one O(5) atom. In the ninth O site, O(9) is bonded in a trigonal planar geometry to one Mg(4), one Mg(5), and one As(1) atom. In the tenth O site, O(10) is bonded in a trigonal planar geometry to one Mg(1), one Mg(6), and one As(1) atom. In the eleventh O site, O(11) is bonded in a distorted trigonal non-coplanar geometry to one Mg(3), one Mg(5), and one As(2) atom. In the twelfth O site, O(12) is bonded in a 2-coordinate geometry to one Mg(3), one Mg(4), and one As(4) atom. In the thirteenth O site, O(13) is bonded in a distorted trigonal planar geometry to one Mg(2), one Mg(6), and one As(3) atom. In the fourteenth O site, O(14) is bonded in a distorted T-shaped geometry to one Mg(4), one Mg(7), and one As(6) atom. In the fifteenth O site, O(15) is bonded in a 4-coordinate geometry to one Mg(4), one Mg(8), one As(5), and one O(24) atom. The O(15)-O(24) bond length is 1.50 Å. In the sixteenth O site, O(16) is bonded to one Mg(3), one Mg(5), one Mg(9), and one O(7) atom to form distorted OMg3O trigonal pyramids that share  a cornercorner with one O(5)Mg2AsO tetrahedra,  a cornercorner with one O(17)Mg3O tetrahedra,  a cornercorner with one Mg(6)O5 trigonal bipyramid, and  a cornercorner with one O(3)Mg3As trigonal pyramid. In the seventeenth O site, O(17) is bonded to one Mg(4), one Mg(7), one Mg(9), and one O(21) atom to form distorted OMg3O tetrahedra that share  a cornercorner with one As(5)O6 octahedra,  a cornercorner with one O(2)Mg2As2 tetrahedra,  a cornercorner with one O(5)Mg2AsO tetrahedra, and  a cornercorner with one O(16)Mg3O trigonal pyramid. The corner-sharing octahedral tilt angles are 69°. The O(17)-O(21) bond length is 1.50 Å. In the eighteenth O site, O(18) is bonded in a trigonal planar geometry to one Mg(3), one Mg(7), and one As(3) atom. In the nineteenth O site, O(19) is bonded in a trigonal non-coplanar geometry to one Mg(4), one Mg(8), and one As(2) atom. In the twentieth O site, O(20) is bonded in a 4-coordinate geometry to one Mg(1), one Mg(7), one As(3), and one As(5) atom. In the twenty-first O site, O(21) is bonded in a 3-coordinate geometry to one Mg(4), one As(5), and one O(17) atom. In the twenty-second O site, O(22) is bonded in a 3-coordinate geometry to one Mg(2), one Mg(9), and one As(5) atom. In the twenty-third O site, O(23) is bonded in a distorted trigonal planar geometry to one Mg(6), one Mg(9), and one As(6) atom. In the twenty-fourth O site, O(24) is bonded in a 4-coordinate geometry to one Mg(5), one Mg(8), one As(6), and one O(15) atom.