DOE OSTI2020
Hf3C is Uranium Silicide-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent Hf sites. In the first Hf site, Hf is bonded to eight Hf and four equivalent C atoms to form distorted HfHf8C4 cuboctahedra that share corners with twelve equivalent HfHf8C4 cuboctahedra, edges with eight equivalent HfHf8C4 cuboctahedra, edges with eight equivalent CHf12 cuboctahedra, faces with four equivalent CHf12 cuboctahedra, and faces with ten equivalent HfHf8C4 cuboctahedra. There are four shorter (2.78 Å) and four longer (3.01 Å) Hf–Hf bond lengths. All Hf–C bond lengths are 3.01 Å. In the second Hf site, Hf is bonded in a square co-planar geometry to eight equivalent Hf and four equivalent C atoms. All Hf–C bond lengths are 2.78 Å. C is bonded to twelve Hf atoms to form CHf12 cuboctahedra that share corners with four equivalent CHf12 cuboctahedra, edges with eight equivalent CHf12 cuboctahedra, edges with sixteen equivalent HfHf8C4 cuboctahedra, faces with four equivalent CHf12 cuboctahedra, and faces with eight equivalent HfHf8C4 cuboctahedra.