DOE OSTI2020
VCoAl is Frank-Kasper $\mu$ Phase-derived structured and crystallizes in the monoclinic Pm space group. The structure is three-dimensional. there are four inequivalent V sites. In the first V site, V is bonded in a 6-coordinate geometry to six Co and six Al atoms. There are a spread of V–Co bond distances ranging from 2.25–2.40 Å. There are a spread of V–Al bond distances ranging from 2.74–2.83 Å. In the second V site, V is bonded in a 12-coordinate geometry to four V, two equivalent Co, and six Al atoms. There are a spread of V–V bond distances ranging from 2.29–2.52 Å. Both V–Co bond lengths are 2.48 Å. There are a spread of V–Al bond distances ranging from 2.81–2.93 Å. In the third V site, V is bonded in a 12-coordinate geometry to four V, two equivalent Co, and six Al atoms. There are one shorter (2.28 Å) and one longer (2.36 Å) V–V bond lengths. Both V–Co bond lengths are 2.47 Å. There are a spread of V–Al bond distances ranging from 2.82–2.93 Å. In the fourth V site, V is bonded in a 12-coordinate geometry to four V, two equivalent Co, and six Al atoms. Both V–Co bond lengths are 2.48 Å. There are two shorter (2.88 Å) and four longer (2.95 Å) V–Al bond lengths. There are three inequivalent Co sites. In the first Co site, Co is bonded to four V, two Co, and six Al atoms to form distorted CoAl6V4Co2 cuboctahedra that share corners with four CoAl6V2Co4 cuboctahedra, edges with six equivalent CoAl6V4Co2 cuboctahedra, and faces with eight CoAl6V4Co2 cuboctahedra. There are one shorter (2.47 Å) and one longer (2.48 Å) Co–Co bond lengths. There are a spread of Co–Al bond distances ranging from 2.65–2.82 Å. In the second Co site, Co is bonded to two equivalent V, four Co, and six Al atoms to form distorted CoAl6V2Co4 cuboctahedra that share corners with eight CoAl6V4Co2 cuboctahedra, edges with two equivalent CoAl6V2Co4 cuboctahedra, and faces with ten CoAl6V4Co2 cuboctahedra. There are one shorter (2.37 Å) and one longer (2.51 Å) Co–Co bond lengths. There are a spread of Co–Al bond distances ranging from 2.63–2.82 Å. In the third Co site, Co is bonded to two equivalent V, four Co, and six Al atoms to form distorted CoAl6V2Co4 cuboctahedra that share corners with eight CoAl6V4Co2 cuboctahedra, edges with two equivalent CoAl6V2Co4 cuboctahedra, and faces with ten CoAl6V4Co2 cuboctahedra. There are a spread of Co–Al bond distances ranging from 2.64–2.83 Å. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 7-coordinate geometry to five V, seven Co, and four Al atoms. There are a spread of Al–Al bond distances ranging from 2.81–2.93 Å. In the second Al site, Al is bonded in a 5-coordinate geometry to seven V, five Co, and three equivalent Al atoms.