CaYb2S4 crystallizes in the orthorhombic Pnma space group. Ca(1) is bonded in a 6-coordinate geometry to one S(4), two equivalent S(1), two equivalent S(2), and three equivalent S(3) atoms. There are two inequivalent Yb sites. In the first Yb site, Yb(1) is bonded to one S(1), two equivalent S(2), and three equivalent S(4) atoms to form distorted YbS6 octahedra that share corners with two equivalent S(1)Ca2Yb3S octahedra, corners with three equivalent Yb(2)S6 octahedra, edges with two equivalent Yb(2)S6 octahedra, and edges with four equivalent Yb(1)S6 octahedra. The corner-sharing octahedral tilt angles range from 50-87°. In the second Yb site, Yb(2) is bonded to one S(2), one S(4), two equivalent S(1), and two equivalent S(3) atoms to form distorted YbS6 octahedra that share  a cornercorner with one S(1)Ca2Yb3S octahedra, corners with three equivalent Yb(1)S6 octahedra, edges with two equivalent Yb(1)S6 octahedra, and edges with two equivalent Yb(2)S6 octahedra. The corner-sharing octahedral tilt angles range from 47-87°. There are four inequivalent S sites. In the first S site, S(1) is bonded to two equivalent Ca(1), one Yb(1), two equivalent Yb(2), and one S(2) atom to form SCa2Yb3S octahedra that share  a cornercorner with one Yb(2)S6 octahedra, corners with two equivalent Yb(1)S6 octahedra, corners with six equivalent S(3)Ca3Yb2 square pyramids, corners with three equivalent S(4)CaYb4 trigonal bipyramids, edges with two equivalent S(1)Ca2Yb3S octahedra, edges with two equivalent S(3)Ca3Yb2 square pyramids, and edges with two equivalent S(4)CaYb4 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 47-65°. In the second S site, S(2) is bonded in a 6-coordinate geometry to two equivalent Ca(1), one Yb(2), two equivalent Yb(1), and one S(1) atom. In the third S site, S(3) is bonded to three equivalent Ca(1) and two equivalent Yb(2) atoms to form distorted SCa3Yb2 square pyramids that share corners with six equivalent S(1)Ca2Yb3S octahedra,  a cornercorner with one S(4)CaYb4 trigonal bipyramid, edges with two equivalent S(1)Ca2Yb3S octahedra, edges with four equivalent S(3)Ca3Yb2 square pyramids, and edges with two equivalent S(4)CaYb4 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 10-62°. In the fourth S site, S(4) is bonded to one Ca(1), one Yb(2), and three equivalent Yb(1) atoms to form SCaYb4 trigonal bipyramids that share corners with three equivalent S(1)Ca2Yb3S octahedra,  a cornercorner with one S(3)Ca3Yb2 square pyramid, corners with two equivalent S(4)CaYb4 trigonal bipyramids, edges with two equivalent S(1)Ca2Yb3S octahedra, edges with two equivalent S(3)Ca3Yb2 square pyramids, and edges with two equivalent S(4)CaYb4 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 5-74°.
CaYb2S4 crystallizes in the orthorhombic Pnma space group. Ca(1) is bonded in a 6-coordinate geometry to one S(4), two equivalent S(1), two equivalent S(2), and three equivalent S(3) atoms. The Ca(1)-S(4) bond length is 3.00 Å. Both Ca(1)-S(1) bond lengths are 3.01 Å. Both Ca(1)-S(2) bond lengths are 3.39 Å. There is one shorter (2.71 Å) and two longer (2.84 Å) Ca(1)-S(3) bond lengths. There are two inequivalent Yb sites. In the first Yb site, Yb(1) is bonded to one S(1), two equivalent S(2), and three equivalent S(4) atoms to form distorted YbS6 octahedra that share corners with two equivalent S(1)Ca2Yb3S octahedra, corners with three equivalent Yb(2)S6 octahedra, edges with two equivalent Yb(2)S6 octahedra, and edges with four equivalent Yb(1)S6 octahedra. The corner-sharing octahedral tilt angles range from 50-87°. The Yb(1)-S(1) bond length is 3.37 Å. Both Yb(1)-S(2) bond lengths are 2.93 Å. All Yb(1)-S(4) bond lengths are 2.71 Å. In the second Yb site, Yb(2) is bonded to one S(2), one S(4), two equivalent S(1), and two equivalent S(3) atoms to form distorted YbS6 octahedra that share  a cornercorner with one S(1)Ca2Yb3S octahedra, corners with three equivalent Yb(1)S6 octahedra, edges with two equivalent Yb(1)S6 octahedra, and edges with two equivalent Yb(2)S6 octahedra. The corner-sharing octahedral tilt angles range from 47-87°. The Yb(2)-S(2) bond length is 3.18 Å. The Yb(2)-S(4) bond length is 2.74 Å. Both Yb(2)-S(1) bond lengths are 2.98 Å. Both Yb(2)-S(3) bond lengths are 2.70 Å. There are four inequivalent S sites. In the first S site, S(1) is bonded to two equivalent Ca(1), one Yb(1), two equivalent Yb(2), and one S(2) atom to form SCa2Yb3S octahedra that share  a cornercorner with one Yb(2)S6 octahedra, corners with two equivalent Yb(1)S6 octahedra, corners with six equivalent S(3)Ca3Yb2 square pyramids, corners with three equivalent S(4)CaYb4 trigonal bipyramids, edges with two equivalent S(1)Ca2Yb3S octahedra, edges with two equivalent S(3)Ca3Yb2 square pyramids, and edges with two equivalent S(4)CaYb4 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 47-65°. The S(1)-S(2) bond length is 2.14 Å. In the second S site, S(2) is bonded in a 6-coordinate geometry to two equivalent Ca(1), one Yb(2), two equivalent Yb(1), and one S(1) atom. In the third S site, S(3) is bonded to three equivalent Ca(1) and two equivalent Yb(2) atoms to form distorted SCa3Yb2 square pyramids that share corners with six equivalent S(1)Ca2Yb3S octahedra,  a cornercorner with one S(4)CaYb4 trigonal bipyramid, edges with two equivalent S(1)Ca2Yb3S octahedra, edges with four equivalent S(3)Ca3Yb2 square pyramids, and edges with two equivalent S(4)CaYb4 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 10-62°. In the fourth S site, S(4) is bonded to one Ca(1), one Yb(2), and three equivalent Yb(1) atoms to form SCaYb4 trigonal bipyramids that share corners with three equivalent S(1)Ca2Yb3S octahedra,  a cornercorner with one S(3)Ca3Yb2 square pyramid, corners with two equivalent S(4)CaYb4 trigonal bipyramids, edges with two equivalent S(1)Ca2Yb3S octahedra, edges with two equivalent S(3)Ca3Yb2 square pyramids, and edges with two equivalent S(4)CaYb4 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 5-74°.