DOE OSTI2020
Sr5Mg is beta-derived structured and crystallizes in the trigonal R32 space group. The structure is three-dimensional. there are four inequivalent Sr sites. In the first Sr site, Sr is bonded to ten Sr and two equivalent Mg atoms to form distorted SrSr10Mg2 cuboctahedra that share corners with eighteen SrSr10Mg2 cuboctahedra, edges with four equivalent MgSr12 cuboctahedra, edges with fourteen SrSr10Mg2 cuboctahedra, faces with four equivalent MgSr12 cuboctahedra, and faces with sixteen SrSr10Mg2 cuboctahedra. There are a spread of Sr–Sr bond distances ranging from 4.07–4.16 Å. Both Sr–Mg bond lengths are 4.14 Å. In the second Sr site, Sr is bonded to nine Sr and three equivalent Mg atoms to form distorted SrSr9Mg3 cuboctahedra that share corners with six equivalent MgSr12 cuboctahedra, corners with twelve equivalent SrSr9Mg3 cuboctahedra, edges with eighteen SrSr10Mg2 cuboctahedra, faces with four equivalent MgSr12 cuboctahedra, and faces with sixteen SrSr10Mg2 cuboctahedra. There are three shorter (4.10 Å) and one longer (4.16 Å) Sr–Sr bond lengths. All Sr–Mg bond lengths are 4.10 Å. In the third Sr site, Sr is bonded to ten Sr and two equivalent Mg atoms to form distorted SrSr10Mg2 cuboctahedra that share corners with eighteen SrSr10Mg2 cuboctahedra, edges with four equivalent MgSr12 cuboctahedra, edges with fourteen SrSr9Mg3 cuboctahedra, faces with four equivalent MgSr12 cuboctahedra, and faces with sixteen SrSr10Mg2 cuboctahedra. There are four shorter (4.07 Å) and two longer (4.15 Å) Sr–Sr bond lengths. Both Sr–Mg bond lengths are 4.14 Å. In the fourth Sr site, Sr is bonded to ten Sr and two equivalent Mg atoms to form distorted SrSr10Mg2 cuboctahedra that share corners with eighteen SrSr10Mg2 cuboctahedra, edges with four equivalent MgSr12 cuboctahedra, edges with fourteen SrSr9Mg3 cuboctahedra, faces with four equivalent MgSr12 cuboctahedra, and faces with sixteen SrSr10Mg2 cuboctahedra. There are a spread of Sr–Sr bond distances ranging from 4.07–4.16 Å. Both Sr–Mg bond lengths are 4.14 Å. Mg is bonded to twelve Sr atoms to form distorted MgSr12 cuboctahedra that share corners with six equivalent MgSr12 cuboctahedra, corners with twelve equivalent SrSr9Mg3 cuboctahedra, edges with six equivalent MgSr12 cuboctahedra, edges with twelve SrSr10Mg2 cuboctahedra, and faces with twenty SrSr10Mg2 cuboctahedra.