Materials Data on UNiC2 by Materials Project
UNiC2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. U6+ is bonded in a 5-coordinate geometry to five equivalent C4- atoms. There are one shorter (2.33 Å) and four longer (2.50 Å) U–C bond lengths. Ni2+ is bonded to four equivalent C4- atoms to form NiC4 tetrahedra that share corners with four equivalent CU5C octahedra, corners with four equivalent NiC4 tetrahedra, and edges with four equivalent NiC4 tetrahedra. The corner-sharing octahedral tilt angles are 55°. All Ni–C bond lengths are 2.13 Å. There are two inequivalent C4- sites. In the first C4- site, C4- is bonded in a 5-coordinate geometry to four equivalent Ni2+ and one C4- atom. The C–C bond length is 1.45 Å. In the second C4- site, C4- is bonded to five equivalent U6+ and one C4- atom to form CU5C octahedra that share corners with four equivalent CU5C octahedra, corners with four equivalent NiC4 tetrahedra, and edges with eight equivalent CU5C octahedra. The corner-sharing octahedral tilt angles are 14°.