Materials Data on K2Bi8Se13 by Materials Project
K2Bi8Se13 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. K1+ is bonded in a 7-coordinate geometry to seven Se2- atoms. There are a spread of K–Se bond distances ranging from 3.35–3.62 Å. There are four inequivalent Bi3+ sites. In the first Bi3+ site, Bi3+ is bonded to six Se2- atoms to form a mixture of edge and corner-sharing BiSe6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Bi–Se bond distances ranging from 2.89–3.07 Å. In the second Bi3+ site, Bi3+ is bonded to five Se2- atoms to form distorted BiSe5 square pyramids that share corners with two equivalent BiSe6 octahedra and edges with four equivalent BiSe5 square pyramids. The corner-sharing octahedral tilt angles are 67°. There are a spread of Bi–Se bond distances ranging from 2.74–3.01 Å. In the third Bi3+ site, Bi3+ is bonded to six Se2- atoms to form BiSe6 octahedra that share corners with three BiSe6 octahedra, corners with two equivalent BiSe5 square pyramids, and edges with seven BiSe6 octahedra. The corner-sharing octahedra tilt angles range from 0–5°. There are a spread of Bi–Se bond distances ranging from 2.80–3.21 Å. In the fourth Bi3+ site, Bi3+ is bonded to six Se2- atoms to form a mixture of edge and corner-sharing BiSe6 octahedra. The corner-sharing octahedral tilt angles are 5°. There are a spread of Bi–Se bond distances ranging from 2.90–3.06 Å. There are seven inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 5-coordinate geometry to two equivalent K1+ and three Bi3+ atoms. In the second Se2- site, Se2- is bonded to six Bi3+ atoms to form SeBi6 octahedra that share corners with four equivalent SeK2Bi3 trigonal bipyramids, edges with two equivalent SeBi6 octahedra, edges with four equivalent SeBi5 square pyramids, and edges with six SeK2Bi3 trigonal bipyramids. In the third Se2- site, Se2- is bonded to one K1+ and three equivalent Bi3+ atoms to form distorted SeKBi3 trigonal pyramids that share corners with four SeK2Bi3 trigonal bipyramids, corners with two equivalent SeKBi3 trigonal pyramids, and edges with two equivalent SeKBi3 trigonal pyramids. In the fourth Se2- site, Se2- is bonded to five Bi3+ atoms to form SeBi5 square pyramids that share corners with three equivalent SeK2Bi3 trigonal bipyramids, edges with two equivalent SeBi6 octahedra, edges with two equivalent SeBi5 square pyramids, and edges with three SeK2Bi3 trigonal bipyramids. In the fifth Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent Bi3+ atoms. In the sixth Se2- site, Se2- is bonded to two equivalent K1+ and three Bi3+ atoms to form SeK2Bi3 trigonal bipyramids that share corners with three equivalent SeBi5 square pyramids, corners with four SeK2Bi3 trigonal bipyramids, corners with two equivalent SeKBi3 trigonal pyramids, edges with two equivalent SeBi6 octahedra, an edgeedge with one SeBi5 square pyramid, and edges with three SeK2Bi3 trigonal bipyramids. In the seventh Se2- site, Se2- is bonded to two equivalent K1+ and three Bi3+ atoms to form distorted SeK2Bi3 trigonal bipyramids that share corners with two equivalent SeBi6 octahedra, corners with two equivalent SeK2Bi3 trigonal bipyramids, corners with two equivalent SeKBi3 trigonal pyramids, an edgeedge with one SeBi6 octahedra, edges with two equivalent SeBi5 square pyramids, and edges with four SeK2Bi3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 3°.