DOE OSTI2020
Ho4Ni13C4 crystallizes in the orthorhombic Cmmm space group. The structure is three-dimensional. there are two inequivalent Ho sites. In the first Ho site, Ho is bonded in a 5-coordinate geometry to eleven Ni and four equivalent C atoms. There are a spread of Ho–Ni bond distances ranging from 2.62–3.19 Å. All Ho–C bond lengths are 2.69 Å. In the second Ho site, Ho is bonded in a 6-coordinate geometry to fourteen Ni atoms. There are a spread of Ho–Ni bond distances ranging from 2.65–3.02 Å. There are five inequivalent Ni sites. In the first Ni site, Ni is bonded to four equivalent Ho and eight Ni atoms to form NiHo4Ni8 cuboctahedra that share corners with four equivalent CNi6 octahedra and faces with two equivalent NiHo4Ni8 cuboctahedra. The corner-sharing octahedral tilt angles are 34°. There are four shorter (2.40 Å) and four longer (2.49 Å) Ni–Ni bond lengths. In the second Ni site, Ni is bonded in a distorted bent 150 degrees geometry to four Ho and two C atoms. There is one shorter (1.88 Å) and one longer (1.90 Å) Ni–C bond length. In the third Ni site, Ni is bonded in a linear geometry to four Ho and two equivalent C atoms. Both Ni–C bond lengths are 1.92 Å. In the fourth Ni site, Ni is bonded in a single-bond geometry to four Ho, three Ni, and one C atom. Both Ni–Ni bond lengths are 2.41 Å. The Ni–C bond length is 1.86 Å. In the fifth Ni site, Ni is bonded in a 3-coordinate geometry to three Ho and six Ni atoms. There are two inequivalent C sites. In the first C site, C is bonded in a 7-coordinate geometry to four equivalent Ho, two equivalent Ni, and one C atom. The C–C bond length is 1.35 Å. In the second C site, C is bonded to six Ni atoms to form CNi6 octahedra that share corners with two equivalent NiHo4Ni8 cuboctahedra and corners with two equivalent CNi6 octahedra. The corner-sharing octahedral tilt angles are 0°.