Materials Data on La5TlSe8 by Materials Project
La5TlSe8 crystallizes in the tetragonal I-4 space group. The structure is three-dimensional. there are two inequivalent La3+ sites. In the first La3+ site, La3+ is bonded to eight Se2- atoms to form distorted LaSe8 hexagonal bipyramids that share corners with two equivalent TlSe8 hexagonal bipyramids, corners with six LaSe8 hexagonal bipyramids, edges with four equivalent LaSe8 hexagonal bipyramids, faces with two equivalent TlSe8 hexagonal bipyramids, and faces with six LaSe8 hexagonal bipyramids. There are a spread of La–Se bond distances ranging from 3.02–3.34 Å. In the second La3+ site, La3+ is bonded to eight Se2- atoms to form distorted LaSe8 hexagonal bipyramids that share corners with eight equivalent LaSe8 hexagonal bipyramids, edges with four equivalent TlSe8 hexagonal bipyramids, and faces with eight equivalent LaSe8 hexagonal bipyramids. There are four shorter (3.07 Å) and four longer (3.20 Å) La–Se bond lengths. Tl1+ is bonded to eight Se2- atoms to form distorted TlSe8 hexagonal bipyramids that share corners with eight equivalent LaSe8 hexagonal bipyramids, edges with four equivalent LaSe8 hexagonal bipyramids, and faces with eight equivalent LaSe8 hexagonal bipyramids. There are four shorter (3.22 Å) and four longer (3.36 Å) Tl–Se bond lengths. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 6-coordinate geometry to five La3+ and one Tl1+ atom. In the second Se2- site, Se2- is bonded to five La3+ and one Tl1+ atom to form a mixture of distorted face, edge, and corner-sharing SeLa5Tl octahedra. The corner-sharing octahedra tilt angles range from 16–48°.