MgY4S7 crystallizes in the monoclinic Cm space group. Mg(1) is bonded to one S(1), one S(5), two equivalent S(2), and two equivalent S(7) atoms to form MgS6 octahedra that share  a cornercorner with one Y(3)S6 octahedra, corners with two equivalent Y(4)S6 octahedra, edges with two equivalent Mg(1)S6 octahedra, and edges with three equivalent Y(4)S6 octahedra. The corner-sharing octahedral tilt angles range from 3-55°. There are four inequivalent Y sites. In the first Y site, Y(1) is bonded in a 7-coordinate geometry to one S(4), two equivalent S(2), two equivalent S(3), and two equivalent S(5) atoms. In the second Y site, Y(2) is bonded in a 7-coordinate geometry to one S(3), two equivalent S(1), two equivalent S(4), and two equivalent S(6) atoms. In the third Y site, Y(3) is bonded to one S(5), one S(6), two equivalent S(3), and two equivalent S(4) atoms to form YS6 octahedra that share  a cornercorner with one Mg(1)S6 octahedra,  a cornercorner with one Y(4)S6 octahedra, and edges with two equivalent Y(3)S6 octahedra. The corner-sharing octahedral tilt angles range from 52-55°. In the fourth Y site, Y(4) is bonded to one S(2), one S(6), two equivalent S(1), and two equivalent S(7) atoms to form YS6 octahedra that share  a cornercorner with one Y(3)S6 octahedra, corners with two equivalent Mg(1)S6 octahedra, edges with two equivalent Y(4)S6 octahedra, and edges with three equivalent Mg(1)S6 octahedra. The corner-sharing octahedral tilt angles range from 3-52°. There are seven inequivalent S sites. In the first S site, S(1) is bonded to one Mg(1), two equivalent Y(2), and two equivalent Y(4) atoms to form SY4Mg trigonal bipyramids that share  a cornercorner with one S(5)Y3Mg tetrahedra, corners with four equivalent S(6)Y4 tetrahedra, corners with two equivalent S(3)Y5 trigonal bipyramids, corners with two equivalent S(4)Y5 trigonal bipyramids,  an edgeedge with one S(6)Y4 tetrahedra,  an edgeedge with one S(4)Y5 trigonal bipyramid, edges with two equivalent S(2)Y3Mg2 trigonal bipyramids, and edges with two equivalent S(1)Y4Mg trigonal bipyramids. In the second S site, S(2) is bonded to two equivalent Mg(1), one Y(4), and two equivalent Y(1) atoms to form SY3Mg2 trigonal bipyramids that share  a cornercorner with one S(6)Y4 tetrahedra, corners with four equivalent S(5)Y3Mg tetrahedra, corners with two equivalent S(3)Y5 trigonal bipyramids, corners with two equivalent S(4)Y5 trigonal bipyramids,  an edgeedge with one S(5)Y3Mg tetrahedra,  an edgeedge with one S(3)Y5 trigonal bipyramid, edges with two equivalent S(2)Y3Mg2 trigonal bipyramids, and edges with two equivalent S(1)Y4Mg trigonal bipyramids. In the third S site, S(3) is bonded to one Y(2), two equivalent Y(1), and two equivalent Y(3) atoms to form distorted SY5 trigonal bipyramids that share corners with four equivalent S(5)Y3Mg tetrahedra, corners with two equivalent S(2)Y3Mg2 trigonal bipyramids, corners with two equivalent S(1)Y4Mg trigonal bipyramids, corners with two equivalent S(4)Y5 trigonal bipyramids,  an edgeedge with one S(5)Y3Mg tetrahedra, edges with two equivalent S(6)Y4 tetrahedra,  an edgeedge with one S(2)Y3Mg2 trigonal bipyramid, edges with two equivalent S(3)Y5 trigonal bipyramids, and edges with three equivalent S(4)Y5 trigonal bipyramids. In the fourth S site, S(4) is bonded to one Y(1), two equivalent Y(2), and two equivalent Y(3) atoms to form distorted SY5 trigonal bipyramids that share corners with four equivalent S(6)Y4 tetrahedra, corners with two equivalent S(2)Y3Mg2 trigonal bipyramids, corners with two equivalent S(1)Y4Mg trigonal bipyramids, corners with two equivalent S(3)Y5 trigonal bipyramids,  an edgeedge with one S(6)Y4 tetrahedra, edges with two equivalent S(5)Y3Mg tetrahedra,  an edgeedge with one S(1)Y4Mg trigonal bipyramid, edges with two equivalent S(4)Y5 trigonal bipyramids, and edges with three equivalent S(3)Y5 trigonal bipyramids. In the fifth S site, S(5) is bonded to one Mg(1), one Y(3), and two equivalent Y(1) atoms to form distorted SY3Mg tetrahedra that share  a cornercorner with one S(6)Y4 tetrahedra, corners with two equivalent S(5)Y3Mg tetrahedra,  a cornercorner with one S(1)Y4Mg trigonal bipyramid, corners with four equivalent S(2)Y3Mg2 trigonal bipyramids, corners with four equivalent S(3)Y5 trigonal bipyramids,  an edgeedge with one S(2)Y3Mg2 trigonal bipyramid,  an edgeedge with one S(3)Y5 trigonal bipyramid, and edges with two equivalent S(4)Y5 trigonal bipyramids. In the sixth S site, S(6) is bonded to one Y(3), one Y(4), and two equivalent Y(2) atoms to form SY4 tetrahedra that share  a cornercorner with one S(5)Y3Mg tetrahedra, corners with two equivalent S(6)Y4 tetrahedra,  a cornercorner with one S(2)Y3Mg2 trigonal bipyramid, corners with four equivalent S(1)Y4Mg trigonal bipyramids, corners with four equivalent S(4)Y5 trigonal bipyramids,  an edgeedge with one S(1)Y4Mg trigonal bipyramid,  an edgeedge with one S(4)Y5 trigonal bipyramid, and edges with two equivalent S(3)Y5 trigonal bipyramids. In the seventh S site, S(7) is bonded in a rectangular see-saw-like geometry to two equivalent Mg(1) and two equivalent Y(4) atoms.
MgY4S7 crystallizes in the monoclinic Cm space group. Mg(1) is bonded to one S(1), one S(5), two equivalent S(2), and two equivalent S(7) atoms to form MgS6 octahedra that share  a cornercorner with one Y(3)S6 octahedra, corners with two equivalent Y(4)S6 octahedra, edges with two equivalent Mg(1)S6 octahedra, and edges with three equivalent Y(4)S6 octahedra. The corner-sharing octahedral tilt angles range from 3-55°. The Mg(1)-S(1) bond length is 2.69 Å. The Mg(1)-S(5) bond length is 2.55 Å. Both Mg(1)-S(2) bond lengths are 2.66 Å. Both Mg(1)-S(7) bond lengths are 2.63 Å. There are four inequivalent Y sites. In the first Y site, Y(1) is bonded in a 7-coordinate geometry to one S(4), two equivalent S(2), two equivalent S(3), and two equivalent S(5) atoms. The Y(1)-S(4) bond length is 3.07 Å. Both Y(1)-S(2) bond lengths are 2.87 Å. Both Y(1)-S(3) bond lengths are 2.91 Å. Both Y(1)-S(5) bond lengths are 2.72 Å. In the second Y site, Y(2) is bonded in a 7-coordinate geometry to one S(3), two equivalent S(1), two equivalent S(4), and two equivalent S(6) atoms. The Y(2)-S(3) bond length is 2.99 Å. Both Y(2)-S(1) bond lengths are 2.91 Å. Both Y(2)-S(4) bond lengths are 2.88 Å. Both Y(2)-S(6) bond lengths are 2.71 Å. In the third Y site, Y(3) is bonded to one S(5), one S(6), two equivalent S(3), and two equivalent S(4) atoms to form YS6 octahedra that share  a cornercorner with one Mg(1)S6 octahedra,  a cornercorner with one Y(4)S6 octahedra, and edges with two equivalent Y(3)S6 octahedra. The corner-sharing octahedral tilt angles range from 52-55°. The Y(3)-S(5) bond length is 2.67 Å. The Y(3)-S(6) bond length is 2.69 Å. Both Y(3)-S(3) bond lengths are 2.74 Å. Both Y(3)-S(4) bond lengths are 2.73 Å. In the fourth Y site, Y(4) is bonded to one S(2), one S(6), two equivalent S(1), and two equivalent S(7) atoms to form YS6 octahedra that share  a cornercorner with one Y(3)S6 octahedra, corners with two equivalent Mg(1)S6 octahedra, edges with two equivalent Y(4)S6 octahedra, and edges with three equivalent Mg(1)S6 octahedra. The corner-sharing octahedral tilt angles range from 3-52°. The Y(4)-S(2) bond length is 2.72 Å. The Y(4)-S(6) bond length is 2.72 Å. Both Y(4)-S(1) bond lengths are 2.78 Å. Both Y(4)-S(7) bond lengths are 2.67 Å. There are seven inequivalent S sites. In the first S site, S(1) is bonded to one Mg(1), two equivalent Y(2), and two equivalent Y(4) atoms to form SY4Mg trigonal bipyramids that share  a cornercorner with one S(5)Y3Mg tetrahedra, corners with four equivalent S(6)Y4 tetrahedra, corners with two equivalent S(3)Y5 trigonal bipyramids, corners with two equivalent S(4)Y5 trigonal bipyramids,  an edgeedge with one S(6)Y4 tetrahedra,  an edgeedge with one S(4)Y5 trigonal bipyramid, edges with two equivalent S(2)Y3Mg2 trigonal bipyramids, and edges with two equivalent S(1)Y4Mg trigonal bipyramids. In the second S site, S(2) is bonded to two equivalent Mg(1), one Y(4), and two equivalent Y(1) atoms to form SY3Mg2 trigonal bipyramids that share  a cornercorner with one S(6)Y4 tetrahedra, corners with four equivalent S(5)Y3Mg tetrahedra, corners with two equivalent S(3)Y5 trigonal bipyramids, corners with two equivalent S(4)Y5 trigonal bipyramids,  an edgeedge with one S(5)Y3Mg tetrahedra,  an edgeedge with one S(3)Y5 trigonal bipyramid, edges with two equivalent S(2)Y3Mg2 trigonal bipyramids, and edges with two equivalent S(1)Y4Mg trigonal bipyramids. In the third S site, S(3) is bonded to one Y(2), two equivalent Y(1), and two equivalent Y(3) atoms to form distorted SY5 trigonal bipyramids that share corners with four equivalent S(5)Y3Mg tetrahedra, corners with two equivalent S(2)Y3Mg2 trigonal bipyramids, corners with two equivalent S(1)Y4Mg trigonal bipyramids, corners with two equivalent S(4)Y5 trigonal bipyramids,  an edgeedge with one S(5)Y3Mg tetrahedra, edges with two equivalent S(6)Y4 tetrahedra,  an edgeedge with one S(2)Y3Mg2 trigonal bipyramid, edges with two equivalent S(3)Y5 trigonal bipyramids, and edges with three equivalent S(4)Y5 trigonal bipyramids. In the fourth S site, S(4) is bonded to one Y(1), two equivalent Y(2), and two equivalent Y(3) atoms to form distorted SY5 trigonal bipyramids that share corners with four equivalent S(6)Y4 tetrahedra, corners with two equivalent S(2)Y3Mg2 trigonal bipyramids, corners with two equivalent S(1)Y4Mg trigonal bipyramids, corners with two equivalent S(3)Y5 trigonal bipyramids,  an edgeedge with one S(6)Y4 tetrahedra, edges with two equivalent S(5)Y3Mg tetrahedra,  an edgeedge with one S(1)Y4Mg trigonal bipyramid, edges with two equivalent S(4)Y5 trigonal bipyramids, and edges with three equivalent S(3)Y5 trigonal bipyramids. In the fifth S site, S(5) is bonded to one Mg(1), one Y(3), and two equivalent Y(1) atoms to form distorted SY3Mg tetrahedra that share  a cornercorner with one S(6)Y4 tetrahedra, corners with two equivalent S(5)Y3Mg tetrahedra,  a cornercorner with one S(1)Y4Mg trigonal bipyramid, corners with four equivalent S(2)Y3Mg2 trigonal bipyramids, corners with four equivalent S(3)Y5 trigonal bipyramids,  an edgeedge with one S(2)Y3Mg2 trigonal bipyramid,  an edgeedge with one S(3)Y5 trigonal bipyramid, and edges with two equivalent S(4)Y5 trigonal bipyramids. In the sixth S site, S(6) is bonded to one Y(3), one Y(4), and two equivalent Y(2) atoms to form SY4 tetrahedra that share  a cornercorner with one S(5)Y3Mg tetrahedra, corners with two equivalent S(6)Y4 tetrahedra,  a cornercorner with one S(2)Y3Mg2 trigonal bipyramid, corners with four equivalent S(1)Y4Mg trigonal bipyramids, corners with four equivalent S(4)Y5 trigonal bipyramids,  an edgeedge with one S(1)Y4Mg trigonal bipyramid,  an edgeedge with one S(4)Y5 trigonal bipyramid, and edges with two equivalent S(3)Y5 trigonal bipyramids. In the seventh S site, S(7) is bonded in a rectangular see-saw-like geometry to two equivalent Mg(1) and two equivalent Y(4) atoms.