EuYb2S4 crystallizes in the tetragonal I-42d space group. Yb(1) is bonded to eight equivalent S(1) atoms to form distorted YbS8 hexagonal bipyramids that share corners with four equivalent Yb(1)S8 hexagonal bipyramids, corners with four equivalent Eu(1)S8 hexagonal bipyramids, edges with four equivalent Yb(1)S8 hexagonal bipyramids, faces with four equivalent Yb(1)S8 hexagonal bipyramids, and faces with four equivalent Eu(1)S8 hexagonal bipyramids. Eu(1) is bonded to eight equivalent S(1) atoms to form distorted EuS8 hexagonal bipyramids that share corners with eight equivalent Yb(1)S8 hexagonal bipyramids, edges with four equivalent Eu(1)S8 hexagonal bipyramids, and faces with eight equivalent Yb(1)S8 hexagonal bipyramids. S(1) is bonded to four equivalent Yb(1) and two equivalent Eu(1) atoms to form a mixture of distorted face, corner, and edge-sharing SYb4Eu2 octahedra. The corner-sharing octahedral tilt angles range from 14-51°.
EuYb2S4 crystallizes in the tetragonal I-42d space group. Yb(1) is bonded to eight equivalent S(1) atoms to form distorted YbS8 hexagonal bipyramids that share corners with four equivalent Yb(1)S8 hexagonal bipyramids, corners with four equivalent Eu(1)S8 hexagonal bipyramids, edges with four equivalent Yb(1)S8 hexagonal bipyramids, faces with four equivalent Yb(1)S8 hexagonal bipyramids, and faces with four equivalent Eu(1)S8 hexagonal bipyramids. There are two shorter (2.86 Å) and six longer (2.87 Å) Yb(1)-S(1) bond lengths. Eu(1) is bonded to eight equivalent S(1) atoms to form distorted EuS8 hexagonal bipyramids that share corners with eight equivalent Yb(1)S8 hexagonal bipyramids, edges with four equivalent Eu(1)S8 hexagonal bipyramids, and faces with eight equivalent Yb(1)S8 hexagonal bipyramids. There are four shorter (2.86 Å) and four longer (2.88 Å) Eu(1)-S(1) bond lengths. S(1) is bonded to four equivalent Yb(1) and two equivalent Eu(1) atoms to form a mixture of distorted face, corner, and edge-sharing SYb4Eu2 octahedra. The corner-sharing octahedral tilt angles range from 14-51°.