ErPS4 is Zircon-like structured and crystallizes in the tetragonal I4_1/acd space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 8-coordinate geometry to four equivalent S(1) and four equivalent S(2) atoms. In the second Er site, Er(2) is bonded to four equivalent S(1) and four equivalent S(2) atoms to form distorted ErS8 hexagonal bipyramids that share edges with four equivalent P(1)S4 tetrahedra. P(1) is bonded to two equivalent S(1) and two equivalent S(2) atoms to form PS4 tetrahedra that share edges with two equivalent Er(2)S8 hexagonal bipyramids. There are two inequivalent S sites. In the first S site, S(1) is bonded in a 3-coordinate geometry to one Er(1), one Er(2), and one P(1) atom. In the second S site, S(2) is bonded in a distorted T-shaped geometry to one Er(1), one Er(2), and one P(1) atom.
ErPS4 is Zircon-like structured and crystallizes in the tetragonal I4_1/acd space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 8-coordinate geometry to four equivalent S(1) and four equivalent S(2) atoms. All Er(1)-S(1) bond lengths are 2.99 Å. All Er(1)-S(2) bond lengths are 2.78 Å. In the second Er site, Er(2) is bonded to four equivalent S(1) and four equivalent S(2) atoms to form distorted ErS8 hexagonal bipyramids that share edges with four equivalent P(1)S4 tetrahedra. All Er(2)-S(1) bond lengths are 2.87 Å. All Er(2)-S(2) bond lengths are 2.88 Å. P(1) is bonded to two equivalent S(1) and two equivalent S(2) atoms to form PS4 tetrahedra that share edges with two equivalent Er(2)S8 hexagonal bipyramids. Both P(1)-S(1) bond lengths are 2.03 Å. Both P(1)-S(2) bond lengths are 2.03 Å. There are two inequivalent S sites. In the first S site, S(1) is bonded in a 3-coordinate geometry to one Er(1), one Er(2), and one P(1) atom. In the second S site, S(2) is bonded in a distorted T-shaped geometry to one Er(1), one Er(2), and one P(1) atom.