Materials Data on Sr4GeAs4 by Materials Project
Sr4GeAs4 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 GeAs4 tetrahedra, edges with twelve SrAs6 octahedra, and a faceface with one GeAs4 tetrahedra. The corner-sharing octahedra tilt angles range from 13–16°. There are a spread of Sr–As bond distances ranging from 3.17–3.37 Å. In the second Sr2+ site, Sr2+ is bonded to six As3- atoms to form SrAs6 octahedra that share corners with six equivalent SrAs6 octahedra, corners with three equivalent GeAs4 tetrahedra, edges with twelve SrAs6 octahedra, and a faceface with one GeAs4 tetrahedra. The corner-sharing octahedra tilt angles range from 14–15°. There are three shorter (3.21 Å) and three longer (3.37 Å) Sr–As bond lengths. There are two inequivalent Ge4+ sites. In the first Ge4+ site, Ge4+ is bonded to four equivalent As3- atoms to form GeAs4 tetrahedra that share corners with twelve SrAs6 octahedra and faces with four equivalent SrAs6 octahedra. The corner-sharing octahedra tilt angles range from 49–54°. All Ge–As bond lengths are 2.48 Å. In the second Ge4+ site, Ge4+ is bonded to four equivalent As3- atoms to form GeAs4 tetrahedra that share corners with twelve equivalent SrAs6 octahedra and faces with four equivalent SrAs6 octahedra. The corner-sharing octahedral tilt angles are 54°. All Ge–As bond lengths are 2.47 Å. There are two inequivalent As3- sites. In the first As3- site, As3- is bonded to six Sr2+ and one Ge4+ atom to form a mixture of distorted edge, corner, and face-sharing AsSr6Ge pentagonal bipyramids. In the second As3- site, As3- is bonded to six Sr2+ and one Ge4+ atom to form a mixture of distorted edge, corner, and face-sharing AsSr6Ge pentagonal bipyramids.