DOI: 10.17188/1689421
title: Materials Data on Tb9Al5Se21 by Materials Project

description: Tb9Al5Se21 crystallizes in the trigonal R3 space group. The structure is three-dimensional. there are six inequivalent Tb3+ sites. In the first Tb3+ site, Tb3+ is bonded in a 7-coordinate geometry to seven Se2- atoms. There are a spread of Tb–Se bond distances ranging from 2.90–3.13 Å. In the second Tb3+ site, Tb3+ is bonded in a 7-coordinate geometry to eight Se2- atoms. There are a spread of Tb–Se bond distances ranging from 2.88–3.55 Å. In the third Tb3+ site, Tb3+ is bonded to seven Se2- atoms to form distorted TbSe7 pentagonal bipyramids that share a cornercorner with one AlSe6 octahedra, corners with three TbSe7 pentagonal bipyramids, corners with two AlSe4 tetrahedra, an edgeedge with one AlSe6 octahedra, and an edgeedge with one AlSe4 tetrahedra. The corner-sharing octahedral tilt angles are 38°. There are a spread of Tb–Se bond distances ranging from 2.90–3.18 Å. In the fourth Tb3+ site, Tb3+ is bonded in a 7-coordinate geometry to seven Se2- atoms. There are a spread of Tb–Se bond distances ranging from 2.87–3.24 Å. In the fifth Tb3+ site, Tb3+ is bonded in a 7-coordinate geometry to eight Se2- atoms. There are a spread of Tb–Se bond distances ranging from 2.89–3.53 Å. In the sixth Tb3+ site, Tb3+ is bonded to seven Se2- atoms to form distorted TbSe7 pentagonal bipyramids that share a cornercorner with one AlSe6 octahedra, corners with three TbSe7 pentagonal bipyramids, corners with two AlSe4 tetrahedra, an edgeedge with one AlSe6 octahedra, and an edgeedge with one AlSe4 tetrahedra. The corner-sharing octahedral tilt angles are 38°. There are a spread of Tb–Se bond distances ranging from 2.91–3.08 Å. There are six inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four Se2- atoms to form AlSe4 tetrahedra that share corners with two TbSe7 pentagonal bipyramids and an edgeedge with one TbSe7 pentagonal bipyramid. There are a spread of Al–Se bond distances ranging from 2.38–2.40 Å. In the second Al3+ site, Al3+ is bonded to four Se2- atoms to form AlSe4 tetrahedra that share corners with two TbSe7 pentagonal bipyramids and an edgeedge with one TbSe7 pentagonal bipyramid. There are a spread of Al–Se bond distances ranging from 2.38–2.41 Å. In the third Al3+ site, Al3+ is bonded to six Se2- atoms to form AlSe6 octahedra that share corners with three equivalent TbSe7 pentagonal bipyramids and a faceface with one AlSe6 octahedra. There are three shorter (2.58 Å) and three longer (2.62 Å) Al–Se bond lengths. In the fourth Al3+ site, Al3+ is bonded to six Se2- atoms to form distorted AlSe6 octahedra that share edges with three equivalent TbSe7 pentagonal bipyramids and a faceface with one AlSe6 octahedra. There are three shorter (2.46 Å) and three longer (2.81 Å) Al–Se bond lengths. In the fifth Al3+ site, Al3+ is bonded to six Se2- atoms to form distorted AlSe6 octahedra that share edges with three equivalent TbSe7 pentagonal bipyramids and a faceface with one AlSe6 octahedra. There are three shorter (2.45 Å) and three longer (2.84 Å) Al–Se bond lengths. In the sixth Al3+ site, Al3+ is bonded to six Se2- atoms to form AlSe6 octahedra that share corners with three equivalent TbSe7 pentagonal bipyramids and a faceface with one AlSe6 octahedra. There are three shorter (2.57 Å) and three longer (2.62 Å) Al–Se bond lengths. There are fourteen inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to three Tb3+ and one Al3+ atom to form distorted SeTb3Al tetrahedra that share corners with three SeTb3Al2 square pyramids and corners with three SeTb3Al trigonal pyramids. In the second Se2- site, Se2- is bonded to three Tb3+ and one Al3+ atom to form distorted SeTb3Al tetrahedra that share corners with three SeTb3Al2 square pyramids and corners with three SeTb3Al trigonal pyramids. In the third Se2- site, Se2- is bonded in a 4-coordinate geometry to three Tb3+ and one Al3+ atom. In the fourth Se2- site, Se2- is bonded in a distorted rectangular see-saw-like geometry to three Tb3+ and one Al3+ atom. In the fifth Se2- site, Se2- is bonded in a distorted rectangular see-saw-like geometry to three Tb3+ and one Al3+ atom. In the sixth Se2- site, Se2- is bonded in a distorted rectangular see-saw-like geometry to three Tb3+ and one Al3+ atom. In the seventh Se2- site, Se2- is bonded in a distorted rectangular see-saw-like geometry to three Tb3+ and one Al3+ atom. In the eighth Se2- site, Se2- is bonded in a distorted rectangular see-saw-like geometry to three Tb3+ and one Al3+ atom. In the ninth Se2- site, Se2- is bonded in a 4-coordinate geometry to four Tb3+ and one Al3+ atom. In the tenth Se2- site, Se2- is bonded to three Tb3+ and two Al3+ atoms to form distorted SeTb3Al2 square pyramids that share corners with three SeTb3Al tetrahedra, a cornercorner with one SeTb3Al trigonal pyramid, edges with two equivalent SeTb3Al trigonal pyramids, and faces with two equivalent SeTb3Al2 square pyramids. In the eleventh Se2- site, Se2- is bonded to three Tb3+ and one Al3+ atom to form distorted SeTb3Al trigonal pyramids that share a cornercorner with one SeTb3Al2 square pyramid, corners with three SeTb3Al tetrahedra, edges with two equivalent SeTb3Al2 square pyramids, and edges with two equivalent SeTb3Al trigonal pyramids. In the twelfth Se2- site, Se2- is bonded to three Tb3+ and two Al3+ atoms to form distorted SeTb3Al2 square pyramids that share corners with three SeTb3Al tetrahedra, a cornercorner with one SeTb3Al trigonal pyramid, edges with two equivalent SeTb3Al trigonal pyramids, and faces with two equivalent SeTb3Al2 square pyramids. In the thirteenth Se2- site, Se2- is bonded to three Tb3+ and one Al3+ atom to form distorted SeTb3Al trigonal pyramids that share a cornercorner with one SeTb3Al2 square pyramid, corners with three SeTb3Al tetrahedra, edges with two equivalent SeTb3Al2 square pyramids, and edges with two equivalent SeTb3Al trigonal pyramids. In the fourteenth Se2- site, Se2- is bonded in a 4-coordinate geometry to four Tb3+ and one Al3+ atom.