Materials Data on K3NaSn3Se8 by Materials Project
K3NaSn3Se8 crystallizes in the tetragonal P4/nbm space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are four shorter (3.41 Å) and four longer (3.55 Å) K–Se bond lengths. In the second K1+ site, K1+ is bonded in a 8-coordinate geometry to eight equivalent Se2- atoms. All K–Se bond lengths are 3.68 Å. Na1+ is bonded to four equivalent Se2- atoms to form distorted NaSe4 tetrahedra that share edges with two equivalent SnSe4 tetrahedra. All Na–Se bond lengths are 2.96 Å. There are two inequivalent Sn4+ sites. In the first Sn4+ site, Sn4+ is bonded to four Se2- atoms to form SnSe4 tetrahedra that share an edgeedge with one NaSe4 tetrahedra and an edgeedge with one SnSe4 tetrahedra. There are two shorter (2.53 Å) and two longer (2.66 Å) Sn–Se bond lengths. In the second Sn4+ site, Sn4+ is bonded to four equivalent Se2- atoms to form edge-sharing SnSe4 tetrahedra. All Sn–Se bond lengths are 2.59 Å. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to two equivalent K1+ and two Sn4+ atoms to form a mixture of edge and corner-sharing SeK2Sn2 trigonal pyramids. In the second Se2- site, Se2- is bonded in a 6-coordinate geometry to four K1+, one Na1+, and one Sn4+ atom.