CaY2S4 crystallizes in the orthorhombic Pnma space group. Ca(1) is bonded to two equivalent S(2), two equivalent S(4), and three equivalent S(1) atoms to form distorted CaS7 pentagonal bipyramids that share corners with four equivalent Y(1)S6 octahedra, corners with four equivalent Y(2)S6 octahedra,  an edgeedge with one Y(1)S6 octahedra, edges with four equivalent Y(2)S6 octahedra, edges with two equivalent Ca(1)S7 pentagonal bipyramids, and faces with two equivalent Ca(1)S7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 13-68°. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded to one S(4), two equivalent S(2), and three equivalent S(3) atoms to form YS6 octahedra that share corners with three equivalent Y(2)S6 octahedra, corners with four equivalent Ca(1)S7 pentagonal bipyramids, edges with two equivalent Y(2)S6 octahedra, edges with four equivalent Y(1)S6 octahedra, and  an edgeedge with one Ca(1)S7 pentagonal bipyramid. The corner-sharing octahedral tilt angles range from 52-60°. In the second Y site, Y(2) is bonded to one S(2), one S(3), two equivalent S(1), and two equivalent S(4) atoms to form YS6 octahedra that share corners with three equivalent Y(1)S6 octahedra, corners with four equivalent Ca(1)S7 pentagonal bipyramids, edges with two equivalent Y(1)S6 octahedra, edges with two equivalent Y(2)S6 octahedra, and edges with four equivalent Ca(1)S7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 52-60°. There are four inequivalent S sites. In the first S site, S(1) is bonded to three equivalent Ca(1) and two equivalent Y(2) atoms to form SCa3Y2 square pyramids that share corners with two equivalent S(2)Ca2Y3 square pyramids, corners with six equivalent S(4)Ca2Y3 trigonal bipyramids, edges with three equivalent S(2)Ca2Y3 square pyramids, edges with four equivalent S(1)Ca3Y2 square pyramids, and edges with two equivalent S(4)Ca2Y3 trigonal bipyramids. In the second S site, S(2) is bonded to two equivalent Ca(1), one Y(2), and two equivalent Y(1) atoms to form SCa2Y3 square pyramids that share corners with two equivalent S(1)Ca3Y2 square pyramids, corners with two equivalent S(4)Ca2Y3 trigonal bipyramids, edges with two equivalent S(2)Ca2Y3 square pyramids, edges with three equivalent S(1)Ca3Y2 square pyramids, and edges with three equivalent S(4)Ca2Y3 trigonal bipyramids. In the third S site, S(3) is bonded in a rectangular see-saw-like geometry to one Y(2) and three equivalent Y(1) atoms. In the fourth S site, S(4) is bonded to two equivalent Ca(1), one Y(1), and two equivalent Y(2) atoms to form distorted SCa2Y3 trigonal bipyramids that share corners with two equivalent S(2)Ca2Y3 square pyramids, corners with six equivalent S(1)Ca3Y2 square pyramids, edges with two equivalent S(1)Ca3Y2 square pyramids, edges with three equivalent S(2)Ca2Y3 square pyramids, and edges with two equivalent S(4)Ca2Y3 trigonal bipyramids.
CaY2S4 crystallizes in the orthorhombic Pnma space group. Ca(1) is bonded to two equivalent S(2), two equivalent S(4), and three equivalent S(1) atoms to form distorted CaS7 pentagonal bipyramids that share corners with four equivalent Y(1)S6 octahedra, corners with four equivalent Y(2)S6 octahedra,  an edgeedge with one Y(1)S6 octahedra, edges with four equivalent Y(2)S6 octahedra, edges with two equivalent Ca(1)S7 pentagonal bipyramids, and faces with two equivalent Ca(1)S7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 13-68°. Both Ca(1)-S(2) bond lengths are 2.91 Å. Both Ca(1)-S(4) bond lengths are 3.04 Å. There are two shorter (2.88 Å) and one longer (2.93 Å) Ca(1)-S(1) bond length. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded to one S(4), two equivalent S(2), and three equivalent S(3) atoms to form YS6 octahedra that share corners with three equivalent Y(2)S6 octahedra, corners with four equivalent Ca(1)S7 pentagonal bipyramids, edges with two equivalent Y(2)S6 octahedra, edges with four equivalent Y(1)S6 octahedra, and  an edgeedge with one Ca(1)S7 pentagonal bipyramid. The corner-sharing octahedral tilt angles range from 52-60°. The Y(1)-S(4) bond length is 2.76 Å. Both Y(1)-S(2) bond lengths are 2.74 Å. There are two shorter (2.71 Å) and one longer (2.81 Å) Y(1)-S(3) bond length. In the second Y site, Y(2) is bonded to one S(2), one S(3), two equivalent S(1), and two equivalent S(4) atoms to form YS6 octahedra that share corners with three equivalent Y(1)S6 octahedra, corners with four equivalent Ca(1)S7 pentagonal bipyramids, edges with two equivalent Y(1)S6 octahedra, edges with two equivalent Y(2)S6 octahedra, and edges with four equivalent Ca(1)S7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 52-60°. The Y(2)-S(2) bond length is 2.74 Å. The Y(2)-S(3) bond length is 2.78 Å. Both Y(2)-S(1) bond lengths are 2.72 Å. Both Y(2)-S(4) bond lengths are 2.75 Å. There are four inequivalent S sites. In the first S site, S(1) is bonded to three equivalent Ca(1) and two equivalent Y(2) atoms to form SCa3Y2 square pyramids that share corners with two equivalent S(2)Ca2Y3 square pyramids, corners with six equivalent S(4)Ca2Y3 trigonal bipyramids, edges with three equivalent S(2)Ca2Y3 square pyramids, edges with four equivalent S(1)Ca3Y2 square pyramids, and edges with two equivalent S(4)Ca2Y3 trigonal bipyramids. In the second S site, S(2) is bonded to two equivalent Ca(1), one Y(2), and two equivalent Y(1) atoms to form SCa2Y3 square pyramids that share corners with two equivalent S(1)Ca3Y2 square pyramids, corners with two equivalent S(4)Ca2Y3 trigonal bipyramids, edges with two equivalent S(2)Ca2Y3 square pyramids, edges with three equivalent S(1)Ca3Y2 square pyramids, and edges with three equivalent S(4)Ca2Y3 trigonal bipyramids. In the third S site, S(3) is bonded in a rectangular see-saw-like geometry to one Y(2) and three equivalent Y(1) atoms. In the fourth S site, S(4) is bonded to two equivalent Ca(1), one Y(1), and two equivalent Y(2) atoms to form distorted SCa2Y3 trigonal bipyramids that share corners with two equivalent S(2)Ca2Y3 square pyramids, corners with six equivalent S(1)Ca3Y2 square pyramids, edges with two equivalent S(1)Ca3Y2 square pyramids, edges with three equivalent S(2)Ca2Y3 square pyramids, and edges with two equivalent S(4)Ca2Y3 trigonal bipyramids.