Materials Data on Ba7Al4Ge9 by Materials Project
Ba7Al4Ge9 crystallizes in the orthorhombic Fmm2 space group. The structure is three-dimensional. there are three inequivalent Ba sites. In the first Ba site, Ba is bonded in a 7-coordinate geometry to two equivalent Al and seven Ge atoms. Both Ba–Al bond lengths are 3.60 Å. There are a spread of Ba–Ge bond distances ranging from 3.34–3.97 Å. In the second Ba site, Ba is bonded in a 8-coordinate geometry to three Al and eight Ge atoms. There are a spread of Ba–Al bond distances ranging from 3.57–3.83 Å. There are a spread of Ba–Ge bond distances ranging from 3.45–3.84 Å. In the third Ba site, Ba is bonded to four equivalent Al and eight Ge atoms to form a mixture of distorted edge and face-sharing BaAl4Ge8 cuboctahedra. There are two shorter (3.60 Å) and two longer (3.67 Å) Ba–Al bond lengths. There are a spread of Ba–Ge bond distances ranging from 3.57–3.78 Å. There are two inequivalent Al sites. In the first Al site, Al is bonded in a distorted trigonal planar geometry to six Ba and three Ge atoms. There are a spread of Al–Ge bond distances ranging from 2.48–2.52 Å. In the second Al site, Al is bonded in a 4-coordinate geometry to five Ba and four Ge atoms. There are a spread of Al–Ge bond distances ranging from 2.50–2.62 Å. There are five inequivalent Ge sites. In the first Ge site, Ge is bonded in a 1-coordinate geometry to seven Ba, one Al, and one Ge atom. The Ge–Ge bond length is 2.67 Å. In the second Ge site, Ge is bonded in a distorted single-bond geometry to six Ba, one Al, and one Ge atom. In the third Ge site, Ge is bonded in a 9-coordinate geometry to six Ba, two equivalent Al, and one Ge atom. The Ge–Ge bond length is 2.77 Å. In the fourth Ge site, Ge is bonded in a distorted water-like geometry to six Ba and two Al atoms. In the fifth Ge site, Ge is bonded in a 9-coordinate geometry to five Ba, two equivalent Al, and two equivalent Ge atoms.