Materials Data on SrMg6Al by Materials Project
SrMg6Al crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. Sr is bonded to ten Mg and two equivalent Al atoms to form SrMg10Al2 cuboctahedra that share corners with four equivalent MgSr2Mg10 cuboctahedra, corners with six equivalent SrMg10Al2 cuboctahedra, edges with two equivalent MgSr2Mg10 cuboctahedra, faces with two equivalent SrMg10Al2 cuboctahedra, and faces with two equivalent MgSr2Mg10 cuboctahedra. There are a spread of Sr–Mg bond distances ranging from 3.31–3.42 Å. Both Sr–Al bond lengths are 3.27 Å. There are four inequivalent Mg sites. In the first Mg site, Mg is bonded in a 3-coordinate geometry to two equivalent Sr, seven Mg, and one Al atom. There are a spread of Mg–Mg bond distances ranging from 3.14–3.38 Å. The Mg–Al bond length is 3.12 Å. In the second Mg site, Mg is bonded in a 12-coordinate geometry to ten Mg and two equivalent Al atoms. There are two shorter (3.24 Å) and four longer (3.28 Å) Mg–Mg bond lengths. Both Mg–Al bond lengths are 3.40 Å. In the third Mg site, Mg is bonded in a 12-coordinate geometry to two equivalent Sr, six Mg, and two equivalent Al atoms. There are one shorter (3.28 Å) and one longer (3.45 Å) Mg–Mg bond lengths. Both Mg–Al bond lengths are 3.16 Å. In the fourth Mg site, Mg is bonded to two equivalent Sr and ten Mg atoms to form distorted MgSr2Mg10 cuboctahedra that share corners with four equivalent SrMg10Al2 cuboctahedra, corners with six equivalent MgSr2Mg10 cuboctahedra, edges with two equivalent SrMg10Al2 cuboctahedra, faces with two equivalent SrMg10Al2 cuboctahedra, and faces with two equivalent MgSr2Mg10 cuboctahedra. Al is bonded in a 8-coordinate geometry to two equivalent Sr and eight Mg atoms.