DOE OSTI2020
Bi4Se3(BiSe)4 is Calaverite-like structured and crystallizes in the trigonal P-3m1 space group. The structure is two-dimensional and consists of three Bi4Se3 sheets oriented in the (0, 0, 1) direction and four BiSe sheets oriented in the (0, 0, 1) direction. In each Bi4Se3 sheet, there are four inequivalent Bi+1.75+ sites. In the first Bi+1.75+ site, Bi+1.75+ 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 three shorter (2.91 Å) and three longer (3.12 Å) Bi–Se bond lengths. In the second Bi+1.75+ site, Bi+1.75+ 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 three shorter (2.92 Å) and three longer (3.11 Å) Bi–Se bond lengths. In the third Bi+1.75+ site, Bi+1.75+ is bonded in a 3-coordinate geometry to three equivalent Se2- atoms. All Bi–Se bond lengths are 3.64 Å. In the fourth Bi+1.75+ site, Bi+1.75+ is bonded in a 3-coordinate geometry to three equivalent Se2- atoms. All Bi–Se bond lengths are 3.61 Å. There are three inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 3-coordinate geometry to six Bi+1.75+ atoms. In the second Se2- site, Se2- is bonded in a 3-coordinate geometry to six Bi+1.75+ atoms. In the third Se2- site, Se2- is bonded to six Bi+1.75+ atoms to form edge-sharing SeBi6 octahedra. In each BiSe sheet, there are three inequivalent Bi+1.75+ sites. In the first Bi+1.75+ site, Bi+1.75+ is bonded in a 3-coordinate geometry to three equivalent Se2- atoms. All Bi–Se bond lengths are 3.60 Å. In the second Bi+1.75+ site, Bi+1.75+ is bonded to six Se2- atoms to form a mixture of edge and corner-sharing BiSe6 octahedra. The corner-sharing octahedral tilt angles are 1°. There are three shorter (2.89 Å) and three longer (3.13 Å) Bi–Se bond lengths. In the third Bi+1.75+ site, Bi+1.75+ is bonded to six Se2- atoms to form a mixture of edge and corner-sharing BiSe6 octahedra. The corner-sharing octahedral tilt angles are 1°. There are three shorter (2.92 Å) and three longer (3.09 Å) Bi–Se bond lengths. There are three inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to six Bi+1.75+ atoms to form edge-sharing SeBi6 octahedra. In the second Se2- site, Se2- is bonded in a 6-coordinate geometry to six Bi+1.75+ atoms. In the third Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent Bi+1.75+ atoms.