DOI: 10.17188/1701658
title: Materials Data on Na4Mg(SiSe3)2 by Materials Project

description: Na4Mg(SiSe3)2 crystallizes in the monoclinic C2 space group. The structure is three-dimensional. there are four inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to six Se1- atoms to form NaSe6 octahedra that share corners with six NaSe6 octahedra, corners with two equivalent SiSiSe3 tetrahedra, edges with three equivalent MgSe6 octahedra, edges with six NaSe6 octahedra, and edges with two equivalent SiSiSe3 tetrahedra. The corner-sharing octahedra tilt angles range from 6–13°. There are a spread of Na–Se bond distances ranging from 3.00–3.08 Å. In the second Na1+ site, Na1+ is bonded to six Se1- atoms to form NaSe6 octahedra that share corners with two equivalent NaSe6 octahedra, corners with two equivalent MgSe6 octahedra, corners with six equivalent SiSiSe3 tetrahedra, edges with two equivalent MgSe6 octahedra, and edges with eight NaSe6 octahedra. The corner-sharing octahedra tilt angles range from 7–13°. There are a spread of Na–Se bond distances ranging from 3.03–3.17 Å. In the third Na1+ site, Na1+ is bonded to six Se1- atoms to form NaSe6 octahedra that share corners with two equivalent NaSe6 octahedra, corners with two equivalent MgSe6 octahedra, corners with two equivalent SiSiSe3 tetrahedra, edges with two equivalent MgSe6 octahedra, edges with eight NaSe6 octahedra, and edges with two equivalent SiSiSe3 tetrahedra. The corner-sharing octahedral tilt angles are 6°. There are a spread of Na–Se bond distances ranging from 2.94–3.10 Å. In the fourth Na1+ site, Na1+ is bonded to six Se1- atoms to form NaSe6 octahedra that share corners with two equivalent NaSe6 octahedra, corners with two equivalent MgSe6 octahedra, corners with six equivalent SiSiSe3 tetrahedra, edges with two equivalent MgSe6 octahedra, and edges with eight NaSe6 octahedra. The corner-sharing octahedra tilt angles range from 7–8°. There are a spread of Na–Se bond distances ranging from 2.97–3.18 Å. Mg2+ is bonded to six Se1- atoms to form MgSe6 octahedra that share corners with six NaSe6 octahedra, corners with two equivalent SiSiSe3 tetrahedra, edges with nine NaSe6 octahedra, and edges with two equivalent SiSiSe3 tetrahedra. The corner-sharing octahedra tilt angles range from 6–8°. There are a spread of Mg–Se bond distances ranging from 2.79–2.85 Å. Si is bonded to one Si and three Se1- atoms to form distorted SiSiSe3 tetrahedra that share a cornercorner with one MgSe6 octahedra, corners with three SeNa4MgSi octahedra, corners with eight NaSe6 octahedra, an edgeedge with one MgSe6 octahedra, and edges with two NaSe6 octahedra. The corner-sharing octahedra tilt angles range from 12–85°. The Si–Si bond length is 2.34 Å. There are two shorter (2.30 Å) and one longer (2.32 Å) Si–Se bond lengths. There are three inequivalent Se1- sites. In the first Se1- site, Se1- is bonded to four Na1+, one Mg2+, and one Si atom to form distorted SeNa4MgSi octahedra that share corners with seven SeNa4MgSi octahedra, a cornercorner with one SiSiSe3 tetrahedra, and edges with ten SeNa4MgSi octahedra. The corner-sharing octahedra tilt angles range from 3–89°. In the second Se1- site, Se1- is bonded to four Na1+, one Mg2+, and one Si atom to form SeNa4MgSi octahedra that share corners with seven SeNa4MgSi octahedra, a cornercorner with one SiSiSe3 tetrahedra, and edges with ten SeNa4MgSi octahedra. The corner-sharing octahedra tilt angles range from 3–89°. In the third Se1- site, Se1- is bonded to four Na1+, one Mg2+, and one Si atom to form SeNa4MgSi octahedra that share corners with seven SeNa4MgSi octahedra, a cornercorner with one SiSiSe3 tetrahedra, and edges with ten SeNa4MgSi octahedra. The corner-sharing octahedra tilt angles range from 3–88°.