Materials Data on La2MgSe4 by Materials Project

Abstract

MgLa2Se4 crystallizes in the triclinic P-1 space group. The structure is two-dimensional and consists of one MgLa2Se4 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 LaSe6 octahedra, and corners with six LaSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 59–64°. There are a spread of Mg–Se bond distances ranging from 2.56–2.62 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 LaSe4 tetrahedra, edges with two equivalent MgSe6 octahedra, and edges with four equivalent LaSe6 octahedra. There are a spread of Mg–Se bond distances ranging from 2.82–2.94 Å. There are four inequivalent La3+ sites. In the first La3+ site, La3+ is bonded to four Se2- atoms to form LaSe4 tetrahedra that share a cornercorner with one LaSe6 octahedra, corners with two equivalent MgSe6 octahedra, corners with two equivalent MgSe4 tetrahedra, and corners with four LaSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 58–65°. There are a spread of La–Se bond distances ranging from 2.83–2.88 Å. In the second La3+ site, La3+ is bonded to six Se2- atoms to form LaSe6 octahedra that share corners with two equivalent MgSe4 tetrahedra, corners with four LaSe4 tetrahedra, edges with two equivalent LaSe6 octahedra, and edges with four equivalent MgSe6 octahedra. There are a spread of La–Se bond distances ranging from 3.04–3.08 Å. In the third La3+ site, La3+ is bonded to four Se2- atoms to form LaSe4 tetrahedra that share a cornercorner with one LaSe6 octahedra, corners with two equivalent MgSe6 octahedra, corners with two equivalent MgSe4 tetrahedra, and corners with four LaSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 57–69°. There are one shorter (2.82 Å) and three longer (2.86 Å) La–Se bond lengths. In the fourth La3+ site, La3+ is bonded to four Se2- atoms to form LaSe4 tetrahedra that share a cornercorner with one MgSe6 octahedra, corners with two equivalent LaSe6 octahedra, corners with two equivalent MgSe4 tetrahedra, and corners with four LaSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 56–66°. There are a spread of La–Se bond distances ranging from 2.84–2.87 Å. There are eight inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to two equivalent Mg2+ and two La3+ atoms to form a mixture of distorted edge and corner-sharing SeLa2Mg2 tetrahedra. In the second Se2- site, Se2- is bonded to two Mg2+ and two equivalent La3+ atoms to form distorted SeLa2Mg2 tetrahedra that share corners with nine SeLa2Mg2 tetrahedra and edges with three SeLa3Mg tetrahedra. In the third Se2- site, Se2- is bonded in a trigonal non-coplanar geometry to one Mg2+ and two La3+ atoms. In the fourth Se2- site, Se2- is bonded in a trigonal non-coplanar geometry to three La3+ atoms. In the fifth Se2- site, Se2- is bonded in a trigonal non-coplanar geometry to one Mg2+ and two La3+ atoms. In the sixth Se2- site, Se2- is bonded in a trigonal non-coplanar geometry to one Mg2+ and two La3+ atoms. In the seventh Se2- site, Se2- is bonded to one Mg2+ and three La3+ atoms to form distorted SeLa3Mg tetrahedra that share corners with nine SeLa2Mg2 tetrahedra and edges with three SeLa3Mg tetrahedra. In the eighth Se2- site, Se2- is bonded to two equivalent Mg2+ and two La3+ atoms to form distorted SeLa2Mg2 tetrahedra that share corners with nine SeLa2Mg2 tetrahedra and edges with three SeLa3Mg tetrahedra.