DOE OSTI2020
K2Ag4Se3 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to six Se2- atoms to form a mixture of edge, face, and corner-sharing KSe6 octahedra. The corner-sharing octahedra tilt angles range from 41–60°. There are a spread of K–Se bond distances ranging from 3.45–3.51 Å. In the second K1+ site, K1+ is bonded to six Se2- atoms to form a mixture of edge, face, and corner-sharing KSe6 octahedra. The corner-sharing octahedra tilt angles range from 41–60°. There are a spread of K–Se bond distances ranging from 3.33–3.49 Å. There are four inequivalent Ag1+ sites. In the first Ag1+ site, Ag1+ is bonded in a distorted trigonal non-coplanar geometry to three Se2- atoms. There are two shorter (2.68 Å) and one longer (2.74 Å) Ag–Se bond lengths. In the second Ag1+ site, Ag1+ is bonded in a 3-coordinate geometry to four Se2- atoms. There are a spread of Ag–Se bond distances ranging from 2.65–3.23 Å. In the third Ag1+ site, Ag1+ is bonded in a distorted trigonal non-coplanar geometry to three Se2- atoms. There are one shorter (2.67 Å) and two longer (2.80 Å) Ag–Se bond lengths. In the fourth Ag1+ site, Ag1+ is bonded in a distorted trigonal planar geometry to three Se2- atoms. There are two shorter (2.60 Å) and one longer (2.77 Å) Ag–Se bond lengths. There are three inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 7-coordinate geometry to four K1+ and four Ag1+ atoms. In the second Se2- site, Se2- is bonded in a 8-coordinate geometry to five K1+ and three Ag1+ atoms. In the third Se2- site, Se2- is bonded in a 9-coordinate geometry to three K1+ and six Ag1+ atoms.