DOE OSTI2020
K9Co2S7 crystallizes in the cubic P2_13 space group. The structure is three-dimensional. there are five inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to five S2- atoms to form distorted KS5 square pyramids that share a cornercorner with one KS6 octahedra, corners with nine KS5 square pyramids, edges with four equivalent KS5 square pyramids, and a faceface with one KS6 octahedra. The corner-sharing octahedral tilt angles are 44°. There are a spread of K–S bond distances ranging from 3.02–3.40 Å. In the second K1+ site, K1+ is bonded in a 3-coordinate geometry to three equivalent S2- atoms. All K–S bond lengths are 3.23 Å. In the third K1+ site, K1+ is bonded to six S2- atoms to form a mixture of face and corner-sharing KS6 octahedra. There are three shorter (3.37 Å) and three longer (3.39 Å) K–S bond lengths. In the fourth K1+ site, K1+ is bonded to five S2- atoms to form distorted KS5 square pyramids that share a cornercorner with one KS6 octahedra, corners with nine KS5 square pyramids, edges with four equivalent KS5 square pyramids, and a faceface with one KS6 octahedra. The corner-sharing octahedral tilt angles are 44°. There are a spread of K–S bond distances ranging from 3.02–3.40 Å. In the fifth K1+ site, K1+ is bonded in a 3-coordinate geometry to three equivalent S2- atoms. All K–S bond lengths are 3.23 Å. There are two inequivalent Co+2.50+ sites. In the first Co+2.50+ site, Co+2.50+ is bonded in a trigonal planar geometry to three equivalent S2- atoms. All Co–S bond lengths are 2.19 Å. In the second Co+2.50+ site, Co+2.50+ is bonded in a trigonal planar geometry to three equivalent S2- atoms. All Co–S bond lengths are 2.19 Å. There are three inequivalent S2- sites. In the first S2- site, S2- is bonded in a 1-coordinate geometry to six K1+ and one Co+2.50+ atom. In the second S2- site, S2- is bonded in a 1-coordinate geometry to six K1+ and one Co+2.50+ atom. In the third S2- site, S2- is bonded in an octahedral geometry to six K1+ atoms.