DOE OSTI2020
MgLu2S4 crystallizes in the triclinic P-1 space group. The structure is two-dimensional and consists of one MgLu2S4 sheet oriented in the (0, 0, 1) direction. there are two inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four S2- atoms to form MgS4 tetrahedra that share a cornercorner with one MgS6 octahedra, corners with two equivalent LuS6 octahedra, and corners with six LuS4 tetrahedra. The corner-sharing octahedral tilt angles are 60°. There are a spread of Mg–S bond distances ranging from 2.44–2.48 Å. In the second Mg2+ site, Mg2+ is bonded to six S2- atoms to form MgS6 octahedra that share a cornercorner with one MgS4 tetrahedra, corners with five LuS4 tetrahedra, edges with two equivalent MgS6 octahedra, and edges with four equivalent LuS6 octahedra. There are a spread of Mg–S bond distances ranging from 2.68–2.73 Å. There are four inequivalent Lu3+ sites. In the first Lu3+ site, Lu3+ is bonded to four S2- atoms to form LuS4 tetrahedra that share a cornercorner with one LuS6 octahedra, corners with two equivalent MgS6 octahedra, corners with two equivalent MgS4 tetrahedra, and corners with four LuS4 tetrahedra. The corner-sharing octahedra tilt angles range from 59–61°. There are a spread of Lu–S bond distances ranging from 2.52–2.56 Å. In the second Lu3+ site, Lu3+ is bonded to six S2- atoms to form LuS6 octahedra that share corners with two equivalent MgS4 tetrahedra, corners with four LuS4 tetrahedra, edges with two equivalent LuS6 octahedra, and edges with four equivalent MgS6 octahedra. There are a spread of Lu–S bond distances ranging from 2.70–2.77 Å. In the third Lu3+ site, Lu3+ is bonded to four S2- atoms to form LuS4 tetrahedra that share a cornercorner with one LuS6 octahedra, corners with two equivalent MgS6 octahedra, corners with two equivalent MgS4 tetrahedra, and corners with four LuS4 tetrahedra. The corner-sharing octahedra tilt angles range from 59–63°. There are a spread of Lu–S bond distances ranging from 2.52–2.56 Å. In the fourth Lu3+ site, Lu3+ is bonded to four S2- atoms to form LuS4 tetrahedra that share a cornercorner with one MgS6 octahedra, corners with two equivalent LuS6 octahedra, corners with two equivalent MgS4 tetrahedra, and corners with four LuS4 tetrahedra. The corner-sharing octahedra tilt angles range from 59–62°. There are a spread of Lu–S bond distances ranging from 2.53–2.56 Å. There are eight inequivalent S2- sites. In the first S2- site, S2- is bonded to two equivalent Mg2+ and two Lu3+ atoms to form a mixture of distorted edge and corner-sharing SLu2Mg2 tetrahedra. In the second S2- site, S2- is bonded to two Mg2+ and two equivalent Lu3+ atoms to form distorted SLu2Mg2 tetrahedra that share corners with nine SLu2Mg2 tetrahedra and edges with three SLu3Mg tetrahedra. In the third S2- site, S2- is bonded in a trigonal non-coplanar geometry to one Mg2+ and two Lu3+ atoms. In the fourth S2- site, S2- is bonded in a trigonal non-coplanar geometry to three Lu3+ atoms. In the fifth S2- site, S2- is bonded in a trigonal non-coplanar geometry to one Mg2+ and two Lu3+ atoms. In the sixth S2- site, S2- is bonded in a trigonal non-coplanar geometry to one Mg2+ and two Lu3+ atoms. In the seventh S2- site, S2- is bonded to one Mg2+ and three Lu3+ atoms to form distorted SLu3Mg tetrahedra that share corners with nine SLu2Mg2 tetrahedra and edges with three SLu3Mg tetrahedra. In the eighth S2- site, S2- is bonded to two equivalent Mg2+ and two Lu3+ atoms to form distorted SLu2Mg2 tetrahedra that share corners with nine SLu2Mg2 tetrahedra and edges with three SLu3Mg tetrahedra.