Materials Data on Sr5Mg19Ge12 by Materials Project

Sr5Mg19Ge12 crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. there are two inequivalent Sr sites. In the first Sr site, Sr is bonded in a 6-coordinate geometry to ten Mg and six Ge atoms. There are a spread of Sr–Mg bond distances ranging from 3.48–3.84 Å. There are four shorter (3.43 Å) and two longer (3.48 Å) Sr–Ge bond lengths. In the second Sr site, Sr is bonded in a 6-coordinate geometry to six equivalent Ge atoms. All Sr–Ge bond lengths are 3.41 Å. There are five inequivalent Mg sites. In the first Mg site, Mg is bonded in a 5-coordinate geometry to five Ge atoms. There are one shorter (2.85 Å) and four longer (3.14 Å) Mg–Ge bond lengths. In the second Mg site, Mg is bonded to two equivalent Sr and four Ge atoms to form MgSr2Ge4 tetrahedra that share corners with twelve MgSr2Ge4 tetrahedra, edges with two equivalent MgSrGe4 tetrahedra, and faces with four equivalent MgSr2Ge4 tetrahedra. There are two shorter (2.71 Å) and two longer (2.74 Å) Mg–Ge bond lengths. In the third Mg site, Mg is bonded to two equivalent Sr and four Ge atoms to form a mixture of edge, face, and corner-sharing MgSr2Ge4 tetrahedra. There are a spread of Mg–Ge bond distances ranging from 2.76–2.84 Å. In the fourth Mg site, Mg is bonded to one Sr and four Ge atoms to form MgSrGe4 tetrahedra that share corners with ten MgSr2Ge4 tetrahedra, edges with three MgSr2Ge4 tetrahedra, and faces with three MgSrGe4 tetrahedra. There are a spread of Mg–Ge bond distances ranging from 2.73–2.84 Å. In the fifth Mg site, Mg is bonded in a trigonal planar geometry to six equivalent Sr and three equivalent Ge atoms. All Mg–Ge bond lengths are 2.56 Å. There are three inequivalent Ge sites. In the first Ge site, Ge is bonded in a 9-coordinate geometry to two equivalent Sr and seven Mg atoms. In the second Ge site, Ge is bonded in a 9-coordinate geometry to four equivalent Sr and five Mg atoms. In the third Ge site, Ge is bonded in a 9-coordinate geometry to two equivalent Sr and seven Mg atoms.