Mg3Sn3(AsO4)4 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 4-coordinate geometry to one O(1), one O(3), one O(4), one O(5), and one O(7) atom. In the second Mg site, Mg(2) is bonded to two equivalent O(2), two equivalent O(6), and two equivalent O(8) atoms to form MgO6 octahedra that share corners with two equivalent As(2)O4 tetrahedra and corners with four equivalent As(1)O4 tetrahedra. There are two inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a distorted pentagonal planar geometry to one O(1), one O(2), one O(4), one O(7), and one O(8) atom. In the second Sn site, Sn(2) is bonded in a 6-coordinate geometry to two equivalent O(4), two equivalent O(5), and two equivalent O(7) atoms. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(1), one O(4), one O(6), and one O(8) atom to form AsO4 tetrahedra that share corners with two equivalent Mg(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 25-59°. In the second As site, As(2) is bonded to one O(2), one O(3), one O(5), and one O(7) atom to form AsO4 tetrahedra that share  a cornercorner with one Mg(2)O6 octahedra. The corner-sharing octahedral tilt angles are 53°. There are eight inequivalent O sites. In the first O site, O(7) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Sn(1), one Sn(2), and one As(2) atom. In the second O site, O(8) is bonded in a 3-coordinate geometry to one Mg(2), one Sn(1), and one As(1) atom. In the third O site, O(1) is bonded in a 3-coordinate geometry to one Mg(1), one Sn(1), and one As(1) atom. In the fourth O site, O(2) is bonded in a 3-coordinate geometry to one Mg(2), one Sn(1), and one As(2) atom. In the fifth O site, O(3) is bonded in a bent 150 degrees geometry to one Mg(1) and one As(2) atom. In the sixth O site, O(4) is bonded in a 4-coordinate geometry to one Mg(1), one Sn(1), one Sn(2), and one As(1) atom. In the seventh O site, O(5) is bonded in a 3-coordinate geometry to one Mg(1), one Sn(2), and one As(2) atom. In the eighth O site, O(6) is bonded in a bent 150 degrees geometry to one Mg(2) and one As(1) atom.
Mg3Sn3(AsO4)4 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 4-coordinate geometry to one O(1), one O(3), one O(4), one O(5), and one O(7) atom. The Mg(1)-O(1) bond length is 2.07 Å. The Mg(1)-O(3) bond length is 1.94 Å. The Mg(1)-O(4) bond length is 2.61 Å. The Mg(1)-O(5) bond length is 2.05 Å. The Mg(1)-O(7) bond length is 2.14 Å. In the second Mg site, Mg(2) is bonded to two equivalent O(2), two equivalent O(6), and two equivalent O(8) atoms to form MgO6 octahedra that share corners with two equivalent As(2)O4 tetrahedra and corners with four equivalent As(1)O4 tetrahedra. Both Mg(2)-O(2) bond lengths are 2.15 Å. Both Mg(2)-O(6) bond lengths are 1.99 Å. Both Mg(2)-O(8) bond lengths are 2.40 Å. There are two inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a distorted pentagonal planar geometry to one O(1), one O(2), one O(4), one O(7), and one O(8) atom. The Sn(1)-O(1) bond length is 2.38 Å. The Sn(1)-O(2) bond length is 2.52 Å. The Sn(1)-O(4) bond length is 2.26 Å. The Sn(1)-O(7) bond length is 2.49 Å. The Sn(1)-O(8) bond length is 2.45 Å. In the second Sn site, Sn(2) is bonded in a 6-coordinate geometry to two equivalent O(4), two equivalent O(5), and two equivalent O(7) atoms. Both Sn(2)-O(4) bond lengths are 2.69 Å. Both Sn(2)-O(5) bond lengths are 2.44 Å. Both Sn(2)-O(7) bond lengths are 2.45 Å. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(1), one O(4), one O(6), and one O(8) atom to form AsO4 tetrahedra that share corners with two equivalent Mg(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 25-59°. The As(1)-O(1) bond length is 1.74 Å. The As(1)-O(4) bond length is 1.78 Å. The As(1)-O(6) bond length is 1.67 Å. The As(1)-O(8) bond length is 1.74 Å. In the second As site, As(2) is bonded to one O(2), one O(3), one O(5), and one O(7) atom to form AsO4 tetrahedra that share  a cornercorner with one Mg(2)O6 octahedra. The corner-sharing octahedral tilt angles are 53°. The As(2)-O(2) bond length is 1.71 Å. The As(2)-O(3) bond length is 1.68 Å. The As(2)-O(5) bond length is 1.73 Å. The As(2)-O(7) bond length is 1.77 Å. There are eight inequivalent O sites. In the first O site, O(7) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Sn(1), one Sn(2), and one As(2) atom. In the second O site, O(8) is bonded in a 3-coordinate geometry to one Mg(2), one Sn(1), and one As(1) atom. In the third O site, O(1) is bonded in a 3-coordinate geometry to one Mg(1), one Sn(1), and one As(1) atom. In the fourth O site, O(2) is bonded in a 3-coordinate geometry to one Mg(2), one Sn(1), and one As(2) atom. In the fifth O site, O(3) is bonded in a bent 150 degrees geometry to one Mg(1) and one As(2) atom. In the sixth O site, O(4) is bonded in a 4-coordinate geometry to one Mg(1), one Sn(1), one Sn(2), and one As(1) atom. In the seventh O site, O(5) is bonded in a 3-coordinate geometry to one Mg(1), one Sn(2), and one As(2) atom. In the eighth O site, O(6) is bonded in a bent 150 degrees geometry to one Mg(2) and one As(1) atom.