Materials Data on Ba4GeAs4 by Materials Project
Ba4GeAs4 crystallizes in the cubic P-43n space group. The structure is three-dimensional. there are two inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded to six As3- atoms to form BaAs6 octahedra that share corners with six equivalent BaAs6 octahedra, corners with three equivalent GeAs4 tetrahedra, edges with twelve BaAs6 octahedra, and a faceface with one GeAs4 tetrahedra. The corner-sharing octahedra tilt angles range from 15–16°. There are three shorter (3.43 Å) and three longer (3.47 Å) Ba–As bond lengths. In the second Ba2+ site, Ba2+ is bonded to six As3- atoms to form BaAs6 octahedra that share corners with six BaAs6 octahedra, corners with three GeAs4 tetrahedra, edges with twelve BaAs6 octahedra, and a faceface with one GeAs4 tetrahedra. The corner-sharing octahedra tilt angles range from 15–18°. There are a spread of Ba–As bond distances ranging from 3.39–3.48 Å. 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 equivalent BaAs6 octahedra and faces with four equivalent BaAs6 octahedra. The corner-sharing octahedral tilt angles are 53°. All Ge–As bond lengths are 2.51 Å. In the second Ge4+ site, Ge4+ is bonded to four equivalent As3- atoms to form GeAs4 tetrahedra that share corners with twelve BaAs6 octahedra and faces with four equivalent BaAs6 octahedra. The corner-sharing octahedra tilt angles range from 49–52°. All Ge–As bond lengths are 2.52 Å. There are two inequivalent As3- sites. In the first As3- site, As3- is bonded to six Ba2+ and one Ge4+ atom to form a mixture of distorted edge, face, and corner-sharing AsBa6Ge pentagonal bipyramids. In the second As3- site, As3- is bonded to six Ba2+ and one Ge4+ atom to form a mixture of distorted edge, face, and corner-sharing AsBa6Ge pentagonal bipyramids.