Materials Data on Sr4SiAs4 by Materials Project
Sr4SiAs4 crystallizes in the cubic P-43n space group. The structure is three-dimensional. there are two inequivalent Sr2+ sites. In the first Sr2+ site, Sr2+ is bonded to six As3- atoms to form distorted SrAs6 octahedra that share corners with six SrAs6 octahedra, corners with three SiAs4 tetrahedra, edges with twelve SrAs6 octahedra, and a faceface with one SiAs4 tetrahedra. The corner-sharing octahedra tilt angles range from 14–18°. There are a spread of Sr–As bond distances ranging from 3.18–3.33 Å. In the second Sr2+ site, Sr2+ is bonded to six As3- atoms to form distorted SrAs6 octahedra that share corners with six equivalent SrAs6 octahedra, corners with three equivalent SiAs4 tetrahedra, edges with twelve SrAs6 octahedra, and a faceface with one SiAs4 tetrahedra. The corner-sharing octahedra tilt angles range from 15–17°. There are three shorter (3.22 Å) and three longer (3.32 Å) Sr–As bond lengths. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four equivalent As3- atoms to form SiAs4 tetrahedra that share corners with twelve SrAs6 octahedra and faces with four equivalent SrAs6 octahedra. The corner-sharing octahedra tilt angles range from 48–53°. All Si–As bond lengths are 2.40 Å. In the second Si4+ site, Si4+ is bonded to four equivalent As3- atoms to form SiAs4 tetrahedra that share corners with twelve equivalent SrAs6 octahedra and faces with four equivalent SrAs6 octahedra. The corner-sharing octahedral tilt angles are 53°. All Si–As bond lengths are 2.39 Å. There are two inequivalent As3- sites. In the first As3- site, As3- is bonded in a 7-coordinate geometry to six Sr2+ and one Si4+ atom. In the second As3- site, As3- is bonded in a 7-coordinate geometry to six Sr2+ and one Si4+ atom.