DOE OSTI2020
NbNi9Al2 is Uranium Silicide-derived structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Nb is bonded to twelve Ni atoms to form NbNi12 cuboctahedra that share corners with four equivalent NbNi12 cuboctahedra, corners with eight equivalent AlNi12 cuboctahedra, edges with twenty-four NiAl4Ni8 cuboctahedra, faces with two equivalent AlNi12 cuboctahedra, faces with four equivalent NbNi12 cuboctahedra, and faces with twelve NiNb4Ni8 cuboctahedra. There are four shorter (2.56 Å) and eight longer (2.58 Å) Nb–Ni bond lengths. There are five inequivalent Ni sites. In the first Ni site, Ni is bonded to four equivalent Nb and eight equivalent Ni atoms to form NiNb4Ni8 cuboctahedra that share corners with twelve NiNb4Ni8 cuboctahedra, edges with eight equivalent AlNi12 cuboctahedra, edges with sixteen equivalent NiNb2Al2Ni8 cuboctahedra, faces with four equivalent NbNi12 cuboctahedra, and faces with fourteen NiNb4Ni8 cuboctahedra. All Ni–Ni bond lengths are 2.58 Å. In the second Ni site, Ni is bonded to eight Ni and four equivalent Al atoms to form NiAl4Ni8 cuboctahedra that share corners with twelve NiNb4Ni8 cuboctahedra, edges with four equivalent NbNi12 cuboctahedra, edges with four equivalent AlNi12 cuboctahedra, edges with sixteen NiNb2Al2Ni8 cuboctahedra, faces with four equivalent AlNi12 cuboctahedra, and faces with fourteen NiNb4Ni8 cuboctahedra. There are four shorter (2.51 Å) and four longer (2.52 Å) Ni–Ni bond lengths. All Ni–Al bond lengths are 2.56 Å. In the third Ni site, Ni is bonded to two equivalent Nb, eight Ni, and two equivalent Al atoms to form NiNb2Al2Ni8 cuboctahedra that share corners with twelve NiNb2Al2Ni8 cuboctahedra, edges with four equivalent NbNi12 cuboctahedra, edges with four equivalent AlNi12 cuboctahedra, edges with sixteen NiNb4Ni8 cuboctahedra, faces with two equivalent NbNi12 cuboctahedra, faces with two equivalent AlNi12 cuboctahedra, and faces with fourteen NiNb4Ni8 cuboctahedra. All Ni–Ni bond lengths are 2.56 Å. Both Ni–Al bond lengths are 2.54 Å. In the fourth Ni site, Ni is bonded to eight Ni and four equivalent Al atoms to form distorted NiAl4Ni8 cuboctahedra that share corners with twelve NiNb2Al2Ni8 cuboctahedra, edges with eight equivalent AlNi12 cuboctahedra, edges with sixteen NiAl4Ni8 cuboctahedra, faces with four equivalent AlNi12 cuboctahedra, and faces with fourteen NiAl4Ni8 cuboctahedra. All Ni–Ni bond lengths are 2.56 Å. All Ni–Al bond lengths are 2.48 Å. In the fifth Ni site, Ni is bonded to eight Ni and four equivalent Al atoms to form distorted NiAl4Ni8 cuboctahedra that share corners with twelve NiAl4Ni8 cuboctahedra, edges with eight equivalent AlNi12 cuboctahedra, edges with sixteen NiAl4Ni8 cuboctahedra, faces with four equivalent AlNi12 cuboctahedra, and faces with fourteen NiAl4Ni8 cuboctahedra. All Ni–Al bond lengths are 2.48 Å. Al is bonded to twelve Ni atoms to form AlNi12 cuboctahedra that share corners with four equivalent NbNi12 cuboctahedra, corners with eight equivalent AlNi12 cuboctahedra, edges with twenty-four NiNb4Ni8 cuboctahedra, a faceface with one NbNi12 cuboctahedra, faces with five equivalent AlNi12 cuboctahedra, and faces with twelve NiAl4Ni8 cuboctahedra.