DOI: 10.17188/1717064
title: Materials Data on Tb2MgSe4 by Materials Project

description: MgTb2Se4 crystallizes in the triclinic P-1 space group. The structure is two-dimensional and consists of one MgTb2Se4 sheet oriented in the (0, 0, 1) direction. there are two inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four Se2- atoms to form MgSe4 tetrahedra that share a cornercorner with one MgSe6 octahedra, corners with two equivalent TbSe6 octahedra, and corners with six TbSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 58–61°. There are a spread of Mg–Se bond distances ranging from 2.57–2.61 Å. In the second Mg2+ site, Mg2+ is bonded to six Se2- atoms to form MgSe6 octahedra that share a cornercorner with one MgSe4 tetrahedra, corners with five TbSe4 tetrahedra, edges with two equivalent MgSe6 octahedra, and edges with four equivalent TbSe6 octahedra. There are a spread of Mg–Se bond distances ranging from 2.81–2.86 Å. There are four inequivalent Tb3+ sites. In the first Tb3+ site, Tb3+ is bonded to four Se2- atoms to form TbSe4 tetrahedra that share a cornercorner with one TbSe6 octahedra, corners with two equivalent MgSe6 octahedra, corners with two equivalent MgSe4 tetrahedra, and corners with four TbSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 58–62°. There are a spread of Tb–Se bond distances ranging from 2.71–2.75 Å. In the second Tb3+ site, Tb3+ is bonded to six Se2- atoms to form TbSe6 octahedra that share corners with two equivalent MgSe4 tetrahedra, corners with four TbSe4 tetrahedra, edges with two equivalent TbSe6 octahedra, and edges with four equivalent MgSe6 octahedra. There are a spread of Tb–Se bond distances ranging from 2.88–2.96 Å. In the third Tb3+ site, Tb3+ is bonded to four Se2- atoms to form TbSe4 tetrahedra that share a cornercorner with one TbSe6 octahedra, corners with two equivalent MgSe6 octahedra, corners with two equivalent MgSe4 tetrahedra, and corners with four TbSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 58–65°. There are a spread of Tb–Se bond distances ranging from 2.71–2.75 Å. In the fourth Tb3+ site, Tb3+ is bonded to four Se2- atoms to form TbSe4 tetrahedra that share a cornercorner with one MgSe6 octahedra, corners with two equivalent TbSe6 octahedra, corners with two equivalent MgSe4 tetrahedra, and corners with four TbSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 57–63°. There are a spread of Tb–Se bond distances ranging from 2.72–2.74 Å. There are eight inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to two equivalent Mg2+ and two Tb3+ atoms to form distorted SeTb2Mg2 tetrahedra that share corners with seven SeTb3Mg tetrahedra and edges with two SeTb2Mg2 tetrahedra. In the second Se2- site, Se2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two equivalent Tb3+ atoms. In the third Se2- site, Se2- is bonded in a trigonal non-coplanar geometry to one Mg2+ and two Tb3+ atoms. In the fourth Se2- site, Se2- is bonded in a trigonal non-coplanar geometry to three Tb3+ atoms. In the fifth Se2- site, Se2- is bonded in a trigonal non-coplanar geometry to one Mg2+ and two Tb3+ atoms. In the sixth Se2- site, Se2- is bonded in a trigonal non-coplanar geometry to one Mg2+ and two Tb3+ atoms. In the seventh Se2- site, Se2- is bonded to one Mg2+ and three Tb3+ atoms to form distorted SeTb3Mg tetrahedra that share corners with six SeTb2Mg2 tetrahedra and edges with two SeTb3Mg tetrahedra. In the eighth Se2- site, Se2- is bonded to two equivalent Mg2+ and two Tb3+ atoms to form distorted SeTb2Mg2 tetrahedra that share corners with five SeTb2Mg2 tetrahedra and edges with three SeTb3Mg tetrahedra.