DOI: 10.17188/1746495
title: Materials Data on Sm2MgSe4 by Materials Project

description: MgSm2Se4 crystallizes in the triclinic P-1 space group. The structure is two-dimensional and consists of one MgSm2Se4 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 SmSe6 octahedra, and corners with six SmSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 58–61°. There are a spread of Mg–Se bond distances ranging from 2.58–2.61 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 SmSe4 tetrahedra, edges with two equivalent MgSe6 octahedra, and edges with four equivalent SmSe6 octahedra. There are a spread of Mg–Se bond distances ranging from 2.81–2.88 Å. There are four inequivalent Sm3+ sites. In the first Sm3+ site, Sm3+ is bonded to four Se2- atoms to form SmSe4 tetrahedra that share a cornercorner with one SmSe6 octahedra, corners with two equivalent MgSe6 octahedra, corners with two equivalent MgSe4 tetrahedra, and corners with four SmSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 58–64°. There are a spread of Sm–Se bond distances ranging from 2.76–2.80 Å. In the second Sm3+ site, Sm3+ is bonded to six Se2- atoms to form SmSe6 octahedra that share corners with two equivalent MgSe4 tetrahedra, corners with four SmSe4 tetrahedra, edges with two equivalent SmSe6 octahedra, and edges with four equivalent MgSe6 octahedra. There are a spread of Sm–Se bond distances ranging from 2.94–3.02 Å. In the third Sm3+ site, Sm3+ is bonded to four Se2- atoms to form SmSe4 tetrahedra that share a cornercorner with one SmSe6 octahedra, corners with two equivalent MgSe6 octahedra, corners with two equivalent MgSe4 tetrahedra, and corners with four SmSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 58–66°. There are a spread of Sm–Se bond distances ranging from 2.76–2.79 Å. In the fourth Sm3+ site, Sm3+ is bonded to four Se2- atoms to form SmSe4 tetrahedra that share a cornercorner with one MgSe6 octahedra, corners with two equivalent SmSe6 octahedra, corners with two equivalent MgSe4 tetrahedra, and corners with four SmSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 56–64°. There are two shorter (2.77 Å) and two longer (2.78 Å) Sm–Se bond lengths. There are eight inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to two equivalent Mg2+ and two Sm3+ atoms to form distorted SeSm2Mg2 tetrahedra that share corners with seven SeSm3Mg tetrahedra, corners with two equivalent SeSm2Mg2 trigonal pyramids, edges with two SeSm2Mg2 tetrahedra, and an edgeedge with one SeSm2Mg2 trigonal pyramid. In the second Se2- site, Se2- is bonded to two Mg2+ and two equivalent Sm3+ atoms to form distorted SeSm2Mg2 trigonal pyramids that share corners with nine SeSm2Mg2 tetrahedra, edges with two SeSm3Mg tetrahedra, and an edgeedge with one SeSm2Mg2 trigonal pyramid. In the third Se2- site, Se2- is bonded in a trigonal non-coplanar geometry to one Mg2+ and two Sm3+ atoms. In the fourth Se2- site, Se2- is bonded in a trigonal non-coplanar geometry to three Sm3+ atoms. In the fifth Se2- site, Se2- is bonded in a trigonal non-coplanar geometry to one Mg2+ and two Sm3+ atoms. In the sixth Se2- site, Se2- is bonded in a trigonal non-coplanar geometry to one Mg2+ and two Sm3+ atoms. In the seventh Se2- site, Se2- is bonded to one Mg2+ and three Sm3+ atoms to form distorted SeSm3Mg tetrahedra that share corners with six SeSm2Mg2 tetrahedra, corners with three equivalent SeSm2Mg2 trigonal pyramids, edges with two SeSm3Mg tetrahedra, and an edgeedge with one SeSm2Mg2 trigonal pyramid. In the eighth Se2- site, Se2- is bonded to two equivalent Mg2+ and two Sm3+ atoms to form distorted SeSm2Mg2 tetrahedra that share corners with five SeSm2Mg2 tetrahedra, corners with four equivalent SeSm2Mg2 trigonal pyramids, and edges with three SeSm3Mg tetrahedra.