DOE OSTI2020
Sm2Co7 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Sm sites. In the first Sm site, Sm is bonded in a 12-coordinate geometry to twelve Co atoms. There are a spread of Sm–Co bond distances ranging from 2.90–3.16 Å. In the second Sm site, Sm is bonded in a 6-coordinate geometry to eighteen Co atoms. There are a spread of Sm–Co bond distances ranging from 2.90–3.25 Å. There are five inequivalent Co sites. In the first Co site, Co is bonded to six equivalent Sm and six equivalent Co atoms to form CoSm6Co6 cuboctahedra that share corners with twelve equivalent CoSm5Co7 cuboctahedra, edges with six equivalent CoSm6Co6 cuboctahedra, and faces with eighteen equivalent CoSm5Co7 cuboctahedra. All Co–Co bond lengths are 2.57 Å. In the second Co site, Co is bonded in a 12-coordinate geometry to three equivalent Sm and six Co atoms. There are three shorter (2.43 Å) and three longer (2.46 Å) Co–Co bond lengths. In the third Co site, Co is bonded in a 12-coordinate geometry to three equivalent Sm and six Co atoms. There are three shorter (2.44 Å) and three longer (2.46 Å) Co–Co bond lengths. In the fourth Co site, Co is bonded to four equivalent Sm and eight Co atoms to form CoSm4Co8 cuboctahedra that share corners with sixteen CoSm5Co7 cuboctahedra, edges with ten CoSm5Co7 cuboctahedra, and faces with ten CoSm4Co8 cuboctahedra. There are two shorter (2.50 Å) and two longer (2.52 Å) Co–Co bond lengths. In the fifth Co site, Co is bonded to five Sm and seven Co atoms to form distorted CoSm5Co7 cuboctahedra that share corners with seventeen CoSm6Co6 cuboctahedra, edges with eight CoSm4Co8 cuboctahedra, and faces with fourteen CoSm6Co6 cuboctahedra. There are two shorter (2.50 Å) and two longer (2.52 Å) Co–Co bond lengths.