DOE OSTI2020
VCoSi crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. there are two inequivalent V2+ sites. In the first V2+ site, V2+ is bonded in a 5-coordinate geometry to five Si4- atoms. There are a spread of V–Si bond distances ranging from 2.66–2.74 Å. In the second V2+ site, V2+ is bonded in a 7-coordinate geometry to seven Si4- atoms. There are a spread of V–Si bond distances ranging from 2.68–2.73 Å. There are two inequivalent Co2+ sites. In the first Co2+ site, Co2+ is bonded in a distorted hexagonal planar geometry to two equivalent Co2+ and four Si4- atoms. Both Co–Co bond lengths are 2.37 Å. There are a spread of Co–Si bond distances ranging from 2.25–2.32 Å. In the second Co2+ site, Co2+ is bonded in a 6-coordinate geometry to four Co2+ and two equivalent Si4- atoms. There are one shorter (2.33 Å) and one longer (2.44 Å) Co–Co bond lengths. There are one shorter (2.28 Å) and one longer (2.40 Å) Co–Si bond lengths. There are three inequivalent Si4- sites. In the first Si4- site, Si4- is bonded to six V2+ and six Co2+ atoms to form SiV6Co6 cuboctahedra that share corners with fourteen SiV6Co6 cuboctahedra, edges with six SiV6Co6 cuboctahedra, and faces with four equivalent SiV6Co2Si4 cuboctahedra. In the second Si4- site, Si4- is bonded to six V2+, two equivalent Co2+, and four Si4- atoms to form SiV6Co2Si4 cuboctahedra that share corners with eight SiV6Co6 cuboctahedra, edges with two equivalent SiV6Co2Si4 cuboctahedra, and faces with ten SiV6Co6 cuboctahedra. There are a spread of Si–Si bond distances ranging from 2.29–2.44 Å. In the third Si4- site, Si4- is bonded to six V2+, two equivalent Co2+, and four equivalent Si4- atoms to form SiV6Co2Si4 cuboctahedra that share corners with six SiV6Co6 cuboctahedra, edges with six SiV6Co6 cuboctahedra, and faces with eight equivalent SiV6Co2Si4 cuboctahedra.