Pb5Te4Se is Caswellsilverite-like structured and crystallizes in the tetragonal I4/mmm space group. There are three inequivalent Pb sites. In the first Pb site, Pb(1) is bonded to one Te(1) and five equivalent Te(2) atoms to form PbTe6 octahedra that share  a cornercorner with one Pb(3)Te2Se4 octahedra,  a cornercorner with one Pb(2)Te5Se octahedra, corners with four equivalent Pb(1)Te6 octahedra, edges with four equivalent Pb(2)Te5Se octahedra, and edges with eight equivalent Pb(1)Te6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the second Pb site, Pb(2) is bonded to one Te(2), four equivalent Te(1), and one Se(1) atom to form PbTe5Se octahedra that share  a cornercorner with one Pb(1)Te6 octahedra, corners with five equivalent Pb(2)Te5Se octahedra, edges with four equivalent Pb(3)Te2Se4 octahedra, edges with four equivalent Pb(2)Te5Se octahedra, and edges with four equivalent Pb(1)Te6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. In the third Pb site, Pb(3) is bonded to two equivalent Te(1) and four equivalent Se(1) atoms to form PbTe2Se4 octahedra that share corners with two equivalent Pb(1)Te6 octahedra, corners with four equivalent Pb(3)Te2Se4 octahedra, edges with four equivalent Pb(3)Te2Se4 octahedra, and edges with eight equivalent Pb(2)Te5Se octahedra. The corner-sharing octahedra are not tilted. There are two inequivalent Te sites. In the first Te site, Te(1) is bonded to one Pb(1), one Pb(3), and four equivalent Pb(2) atoms to form TePb6 octahedra that share  a cornercorner with one Te(2)Pb6 octahedra, corners with five equivalent Te(1)Pb6 octahedra, edges with four equivalent Te(1)Pb6 octahedra, edges with four equivalent Te(2)Pb6 octahedra, and edges with four equivalent Se(1)Pb6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. In the second Te site, Te(2) is bonded to one Pb(2) and five equivalent Pb(1) atoms to form TePb6 octahedra that share  a cornercorner with one Te(1)Pb6 octahedra,  a cornercorner with one Se(1)Pb6 octahedra, corners with four equivalent Te(2)Pb6 octahedra, edges with four equivalent Te(1)Pb6 octahedra, and edges with eight equivalent Te(2)Pb6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. Se(1) is bonded to two equivalent Pb(2) and four equivalent Pb(3) atoms to form SePb6 octahedra that share corners with two equivalent Te(2)Pb6 octahedra, corners with four equivalent Se(1)Pb6 octahedra, edges with four equivalent Se(1)Pb6 octahedra, and edges with eight equivalent Te(1)Pb6 octahedra. The corner-sharing octahedra are not tilted.
Pb5Te4Se is Caswellsilverite-like structured and crystallizes in the tetragonal I4/mmm space group. There are three inequivalent Pb sites. In the first Pb site, Pb(1) is bonded to one Te(1) and five equivalent Te(2) atoms to form PbTe6 octahedra that share  a cornercorner with one Pb(3)Te2Se4 octahedra,  a cornercorner with one Pb(2)Te5Se octahedra, corners with four equivalent Pb(1)Te6 octahedra, edges with four equivalent Pb(2)Te5Se octahedra, and edges with eight equivalent Pb(1)Te6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. The Pb(1)-Te(1) bond length is 3.31 Å. There are four shorter (3.24 Å) and one longer (3.31 Å) Pb(1)-Te(2) bond length. In the second Pb site, Pb(2) is bonded to one Te(2), four equivalent Te(1), and one Se(1) atom to form PbTe5Se octahedra that share  a cornercorner with one Pb(1)Te6 octahedra, corners with five equivalent Pb(2)Te5Se octahedra, edges with four equivalent Pb(3)Te2Se4 octahedra, edges with four equivalent Pb(2)Te5Se octahedra, and edges with four equivalent Pb(1)Te6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. The Pb(2)-Te(2) bond length is 3.36 Å. All Pb(2)-Te(1) bond lengths are 3.24 Å. The Pb(2)-Se(1) bond length is 3.22 Å. In the third Pb site, Pb(3) is bonded to two equivalent Te(1) and four equivalent Se(1) atoms to form PbTe2Se4 octahedra that share corners with two equivalent Pb(1)Te6 octahedra, corners with four equivalent Pb(3)Te2Se4 octahedra, edges with four equivalent Pb(3)Te2Se4 octahedra, and edges with eight equivalent Pb(2)Te5Se octahedra. The corner-sharing octahedra are not tilted. Both Pb(3)-Te(1) bond lengths are 3.29 Å. All Pb(3)-Se(1) bond lengths are 3.24 Å. There are two inequivalent Te sites. In the first Te site, Te(1) is bonded to one Pb(1), one Pb(3), and four equivalent Pb(2) atoms to form TePb6 octahedra that share  a cornercorner with one Te(2)Pb6 octahedra, corners with five equivalent Te(1)Pb6 octahedra, edges with four equivalent Te(1)Pb6 octahedra, edges with four equivalent Te(2)Pb6 octahedra, and edges with four equivalent Se(1)Pb6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. In the second Te site, Te(2) is bonded to one Pb(2) and five equivalent Pb(1) atoms to form TePb6 octahedra that share  a cornercorner with one Te(1)Pb6 octahedra,  a cornercorner with one Se(1)Pb6 octahedra, corners with four equivalent Te(2)Pb6 octahedra, edges with four equivalent Te(1)Pb6 octahedra, and edges with eight equivalent Te(2)Pb6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. Se(1) is bonded to two equivalent Pb(2) and four equivalent Pb(3) atoms to form SePb6 octahedra that share corners with two equivalent Te(2)Pb6 octahedra, corners with four equivalent Se(1)Pb6 octahedra, edges with four equivalent Se(1)Pb6 octahedra, and edges with eight equivalent Te(1)Pb6 octahedra. The corner-sharing octahedra are not tilted.