Materials Data on Al2FeS4 by Materials Project
FeAl2S4 crystallizes in the trigonal R3m space group. The structure is two-dimensional and consists of three FeAl2S4 sheets oriented in the (0, 0, 1) direction. Fe2+ is bonded to four S2- atoms to form FeS4 tetrahedra that share corners with three equivalent AlS6 octahedra and corners with six equivalent FeS4 tetrahedra. The corner-sharing octahedral tilt angles are 60°. There are three shorter (2.24 Å) and one longer (2.38 Å) Fe–S bond lengths. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six S2- atoms to form AlS6 octahedra that share corners with three equivalent FeS4 tetrahedra, corners with three equivalent AlS4 tetrahedra, and edges with six equivalent AlS6 octahedra. There are three shorter (2.39 Å) and three longer (2.51 Å) Al–S bond lengths. In the second Al3+ site, Al3+ is bonded to four S2- atoms to form AlS4 tetrahedra that share corners with three equivalent AlS6 octahedra and corners with six equivalent AlS4 tetrahedra. The corner-sharing octahedral tilt angles are 56°. There are one shorter (2.24 Å) and three longer (2.29 Å) Al–S bond lengths. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded to one Fe2+ and three equivalent Al3+ atoms to form distorted corner-sharing SAl3Fe tetrahedra. In the second S2- site, S2- is bonded in a trigonal non-coplanar geometry to three equivalent Al3+ atoms. In the third S2- site, S2- is bonded in a trigonal non-coplanar geometry to three equivalent Fe2+ atoms. In the fourth S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to four Al3+ atoms.