Materials Data on Na3Eu2(SiSe3)2 by Materials Project
Na3Eu2(SiSe3)2 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a distorted square co-planar geometry to four equivalent Se atoms. All Na–Se bond lengths are 3.03 Å. In the second Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six Se atoms. There are a spread of Na–Se bond distances ranging from 3.03–3.14 Å. Eu+2.50+ is bonded to six Se atoms to form EuSe6 octahedra that share corners with six equivalent SiSiSe3 tetrahedra and edges with three equivalent EuSe6 octahedra. There are two shorter (3.09 Å) and four longer (3.10 Å) Eu–Se bond lengths. Si4- is bonded to one Si4- and three Se atoms to form distorted SiSiSe3 tetrahedra that share corners with six equivalent EuSe6 octahedra. The corner-sharing octahedral tilt angles are 76°. The Si–Si bond length is 2.36 Å. There are one shorter (2.35 Å) and two longer (2.36 Å) Si–Se bond lengths. There are two inequivalent Se sites. In the first Se site, Se is bonded in a 1-coordinate geometry to three Na1+, two equivalent Eu+2.50+, and one Si4- atom. In the second Se site, Se is bonded in a distorted single-bond geometry to two equivalent Na1+, two equivalent Eu+2.50+, and one Si4- atom.