Y3GaS6 crystallizes in the orthorhombic Cmc2_1 space group. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded to one S(3), two equivalent S(1), two equivalent S(2), and two equivalent S(4) atoms to form distorted YS7 pentagonal bipyramids that share corners with four equivalent Y(1)S7 pentagonal bipyramids, corners with three equivalent Ga(1)S4 tetrahedra, edges with two equivalent Y(1)S7 pentagonal bipyramids,  an edgeedge with one Ga(1)S4 tetrahedra, and  a faceface with one Y(1)S7 pentagonal bipyramid. In the second Y site, Y(2) is bonded in a 7-coordinate geometry to one S(3), two equivalent S(1), and four equivalent S(2) atoms. Ga(1) is bonded to one S(3), one S(4), and two equivalent S(1) atoms to form GaS4 tetrahedra that share corners with six equivalent Y(1)S7 pentagonal bipyramids and edges with two equivalent Y(1)S7 pentagonal bipyramids. There are four inequivalent S sites. In the first S site, S(1) is bonded in a rectangular see-saw-like geometry to one Y(2), two equivalent Y(1), and one Ga(1) atom. In the second S site, S(2) is bonded to two equivalent Y(1) and two equivalent Y(2) atoms to form SY4 tetrahedra that share corners with two equivalent S(2)Y4 tetrahedra, corners with four equivalent S(3)Y3Ga tetrahedra, corners with two equivalent S(4)Y4Ga trigonal bipyramids, edges with three equivalent S(2)Y4 tetrahedra, and  an edgeedge with one S(4)Y4Ga trigonal bipyramid. In the third S site, S(3) is bonded to one Y(2), two equivalent Y(1), and one Ga(1) atom to form distorted SY3Ga tetrahedra that share corners with eight equivalent S(2)Y4 tetrahedra,  a cornercorner with one S(4)Y4Ga trigonal bipyramid, and edges with two equivalent S(4)Y4Ga trigonal bipyramids. In the fourth S site, S(4) is bonded to four equivalent Y(1) and one Ga(1) atom to form distorted SY4Ga trigonal bipyramids that share  a cornercorner with one S(3)Y3Ga tetrahedra, corners with four equivalent S(2)Y4 tetrahedra, edges with two equivalent S(3)Y3Ga tetrahedra, edges with two equivalent S(2)Y4 tetrahedra, and edges with two equivalent S(4)Y4Ga trigonal bipyramids.
Y3GaS6 crystallizes in the orthorhombic Cmc2_1 space group. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded to one S(3), two equivalent S(1), two equivalent S(2), and two equivalent S(4) atoms to form distorted YS7 pentagonal bipyramids that share corners with four equivalent Y(1)S7 pentagonal bipyramids, corners with three equivalent Ga(1)S4 tetrahedra, edges with two equivalent Y(1)S7 pentagonal bipyramids,  an edgeedge with one Ga(1)S4 tetrahedra, and  a faceface with one Y(1)S7 pentagonal bipyramid. The Y(1)-S(3) bond length is 2.79 Å. There is one shorter (2.76 Å) and one longer (2.89 Å) Y(1)-S(1) bond length. There is one shorter (2.67 Å) and one longer (2.72 Å) Y(1)-S(2) bond length. Both Y(1)-S(4) bond lengths are 2.96 Å. In the second Y site, Y(2) is bonded in a 7-coordinate geometry to one S(3), two equivalent S(1), and four equivalent S(2) atoms. The Y(2)-S(3) bond length is 3.04 Å. Both Y(2)-S(1) bond lengths are 2.82 Å. There are two shorter (2.72 Å) and two longer (2.78 Å) Y(2)-S(2) bond lengths. Ga(1) is bonded to one S(3), one S(4), and two equivalent S(1) atoms to form GaS4 tetrahedra that share corners with six equivalent Y(1)S7 pentagonal bipyramids and edges with two equivalent Y(1)S7 pentagonal bipyramids. The Ga(1)-S(3) bond length is 2.26 Å. The Ga(1)-S(4) bond length is 2.32 Å. Both Ga(1)-S(1) bond lengths are 2.28 Å. There are four inequivalent S sites. In the first S site, S(1) is bonded in a rectangular see-saw-like geometry to one Y(2), two equivalent Y(1), and one Ga(1) atom. In the second S site, S(2) is bonded to two equivalent Y(1) and two equivalent Y(2) atoms to form SY4 tetrahedra that share corners with two equivalent S(2)Y4 tetrahedra, corners with four equivalent S(3)Y3Ga tetrahedra, corners with two equivalent S(4)Y4Ga trigonal bipyramids, edges with three equivalent S(2)Y4 tetrahedra, and  an edgeedge with one S(4)Y4Ga trigonal bipyramid. In the third S site, S(3) is bonded to one Y(2), two equivalent Y(1), and one Ga(1) atom to form distorted SY3Ga tetrahedra that share corners with eight equivalent S(2)Y4 tetrahedra,  a cornercorner with one S(4)Y4Ga trigonal bipyramid, and edges with two equivalent S(4)Y4Ga trigonal bipyramids. In the fourth S site, S(4) is bonded to four equivalent Y(1) and one Ga(1) atom to form distorted SY4Ga trigonal bipyramids that share  a cornercorner with one S(3)Y3Ga tetrahedra, corners with four equivalent S(2)Y4 tetrahedra, edges with two equivalent S(3)Y3Ga tetrahedra, edges with two equivalent S(2)Y4 tetrahedra, and edges with two equivalent S(4)Y4Ga trigonal bipyramids.