DOE OSTI2019
Mg149Ac is alpha Samarium-derived structured and crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. there are twenty-seven inequivalent Mg sites. In the first Mg site, Mg is bonded to twelve Mg atoms to form MgMg12 cuboctahedra that share corners with eighteen MgAcMg11 cuboctahedra, edges with eighteen MgMg12 cuboctahedra, and faces with twenty MgMg12 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.18–3.21 Å. In the second Mg site, Mg is bonded to twelve Mg atoms to form MgMg12 cuboctahedra that share corners with eighteen MgMg12 cuboctahedra, an edgeedge with one AcMg12 cuboctahedra, edges with seventeen MgMg12 cuboctahedra, and faces with twenty MgMg12 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.18–3.23 Å. In the third Mg site, Mg is bonded to eleven Mg and one Ac atom to form distorted MgAcMg11 cuboctahedra that share corners with eighteen MgMg12 cuboctahedra, edges with eighteen MgMg12 cuboctahedra, a faceface with one AcMg12 cuboctahedra, and faces with nineteen MgMg12 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.09–3.46 Å. The Mg–Ac bond length is 3.36 Å. In the fourth Mg site, Mg is bonded to twelve Mg atoms to form MgMg12 cuboctahedra that share a cornercorner with one AcMg12 cuboctahedra, corners with seventeen MgMg12 cuboctahedra, edges with eighteen MgMg12 cuboctahedra, and faces with twenty MgMg12 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.15–3.22 Å. In the fifth Mg site, Mg is bonded to twelve Mg atoms to form MgMg12 cuboctahedra that share corners with eighteen MgMg12 cuboctahedra, an edgeedge with one AcMg12 cuboctahedra, edges with seventeen MgMg12 cuboctahedra, and faces with twenty MgMg12 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.15–3.23 Å. In the sixth Mg site, Mg is bonded to twelve Mg atoms to form a mixture of edge, corner, and face-sharing MgMg12 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.18–3.22 Å. In the seventh Mg site, Mg is bonded to twelve Mg atoms to form MgMg12 cuboctahedra that share corners with eighteen MgMg12 cuboctahedra, edges with eighteen MgMg12 cuboctahedra, a faceface with one AcMg12 cuboctahedra, and faces with nineteen MgMg12 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.16–3.26 Å. In the eighth Mg site, Mg is bonded to twelve Mg atoms to form a mixture of edge, corner, and face-sharing MgMg12 cuboctahedra. There are three shorter (3.20 Å) and six longer (3.22 Å) Mg–Mg bond lengths. In the ninth Mg site, Mg is bonded to twelve Mg atoms to form a mixture of edge, corner, and face-sharing MgMg12 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.19–3.25 Å. In the tenth Mg site, Mg is bonded to twelve Mg atoms to form a mixture of edge, corner, and face-sharing MgMg12 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.18–3.21 Å. In the eleventh Mg site, Mg is bonded to twelve Mg atoms to form a mixture of edge, corner, and face-sharing MgMg12 cuboctahedra. There are two shorter (3.16 Å) and three longer (3.19 Å) Mg–Mg bond lengths. In the twelfth Mg site, Mg is bonded to twelve Mg atoms to form MgMg12 cuboctahedra that share corners with eighteen MgMg12 cuboctahedra, an edgeedge with one AcMg12 cuboctahedra, edges with seventeen MgMg12 cuboctahedra, and faces with twenty MgMg12 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.17–3.22 Å. In the thirteenth Mg site, Mg is bonded to eleven Mg and one Ac atom to form distorted MgAcMg11 cuboctahedra that share corners with eighteen MgMg12 cuboctahedra, edges with eighteen MgMg12 cuboctahedra, a faceface with one AcMg12 cuboctahedra, and faces with nineteen MgMg12 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.10–3.38 Å. The Mg–Ac bond length is 3.36 Å. In the fourteenth Mg site, Mg is bonded to twelve Mg atoms to form a mixture of edge, corner, and face-sharing MgMg12 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.19–3.21 Å. In the fifteenth Mg site, Mg is bonded to twelve Mg atoms to form a mixture of edge, corner, and face-sharing MgMg12 cuboctahedra. There are two shorter (3.20 Å) and five longer (3.21 Å) Mg–Mg bond lengths. In the sixteenth Mg site, Mg is bonded to twelve Mg atoms to form a mixture of edge, corner, and face-sharing MgMg12 cuboctahedra. There are three shorter (3.20 Å) and six longer (3.21 Å) Mg–Mg bond lengths. In the seventeenth Mg site, Mg is bonded to twelve Mg atoms to form a mixture of edge, corner, and face-sharing MgMg12 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.19–3.22 Å. In the eighteenth Mg site, Mg is bonded to twelve Mg atoms to form a mixture of edge, corner, and face-sharing MgMg12 cuboctahedra. There are three shorter (3.19 Å) and two longer (3.21 Å) Mg–Mg bond lengths. In the nineteenth Mg site, Mg is bonded to twelve Mg atoms to form MgMg12 cuboctahedra that share corners with eighteen MgMg12 cuboctahedra, edges with eighteen MgMg12 cuboctahedra, a faceface with one AcMg12 cuboctahedra, and faces with nineteen MgMg12 cuboctahedra. There are three shorter (3.19 Å) and six longer (3.23 Å) Mg–Mg bond lengths. In the twentieth Mg site, Mg is bonded to twelve Mg atoms to form MgMg12 cuboctahedra that share a cornercorner with one AcMg12 cuboctahedra, corners with seventeen MgMg12 cuboctahedra, edges with eighteen MgMg12 cuboctahedra, and faces with twenty MgMg12 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.18–3.24 Å. In the twenty-first Mg site, Mg is bonded to twelve Mg atoms to form a mixture of edge, corner, and face-sharing MgMg12 cuboctahedra. There are four shorter (3.21 Å) and two longer (3.22 Å) Mg–Mg bond lengths. In the twenty-second Mg site, Mg is bonded to twelve Mg atoms to form a mixture of edge, corner, and face-sharing MgMg12 cuboctahedra. There are two shorter (3.20 Å) and two longer (3.22 Å) Mg–Mg bond lengths. In the twenty-third Mg site, Mg is bonded to twelve Mg atoms to form a mixture of edge, corner, and face-sharing MgMg12 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.18–3.22 Å. In the twenty-fourth Mg site, Mg is bonded to twelve Mg atoms to form a mixture of edge, corner, and face-sharing MgMg12 cuboctahedra. In the twenty-fifth Mg site, Mg is bonded to twelve Mg atoms to form a mixture of edge, corner, and face-sharing MgMg12 cuboctahedra. There are two shorter (3.20 Å) and one longer (3.21 Å) Mg–Mg bond lengths. In the twenty-sixth Mg site, Mg is bonded to twelve Mg atoms to form a mixture of edge, corner, and face-sharing MgMg12 cuboctahedra. Both Mg–Mg bond lengths are 3.21 Å. In the twenty-seventh Mg site, Mg is bonded to twelve Mg atoms to form a mixture of edge, corner, and face-sharing MgMg12 cuboctahedra. Both Mg–Mg bond lengths are 3.20 Å. Ac is bonded to twelve Mg atoms to form AcMg12 cuboctahedra that share corners with eighteen MgMg12 cuboctahedra, edges with eighteen MgMg12 cuboctahedra, and faces with twenty MgMg12 cuboctahedra.