Materials Data on Ba2Mg17 by Materials Project
Mg17Ba2 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Ba is bonded in a 7-coordinate geometry to nineteen Mg atoms. There are a spread of Ba–Mg bond distances ranging from 3.69–4.07 Å. There are four inequivalent Mg sites. In the first Mg site, Mg is bonded in a 10-coordinate geometry to two equivalent Ba and eight Mg atoms. There are a spread of Mg–Mg bond distances ranging from 3.06–3.28 Å. In the second Mg site, Mg is bonded to three equivalent Ba and nine Mg atoms to form MgBa3Mg9 cuboctahedra that share corners with fifteen MgBa3Mg9 cuboctahedra, edges with eight MgBa2Mg10 cuboctahedra, and faces with ten MgBa3Mg9 cuboctahedra. There are four shorter (3.08 Å) and one longer (3.29 Å) Mg–Mg bond lengths. In the third Mg site, Mg is bonded in a 8-coordinate geometry to one Ba and seven Mg atoms. There are one shorter (3.13 Å) and three longer (3.25 Å) Mg–Mg bond lengths. In the fourth Mg site, Mg is bonded to two equivalent Ba and ten Mg atoms to form a mixture of distorted face, edge, and corner-sharing MgBa2Mg10 cuboctahedra.