DOE OSTI2020
CrNi15Al4 is Uranium Silicide-derived structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Cr is bonded to twelve Ni atoms to form CrNi12 cuboctahedra that share corners with four equivalent CrNi12 cuboctahedra, corners with eight equivalent AlNi12 cuboctahedra, edges with twenty-four NiAl2Cr2Ni8 cuboctahedra, faces with two equivalent AlNi12 cuboctahedra, faces with four equivalent CrNi12 cuboctahedra, and faces with twelve NiAl2Cr2Ni8 cuboctahedra. There are eight shorter (2.48 Å) and four longer (2.50 Å) Cr–Ni bond lengths. There are six inequivalent Ni sites. In the first Ni site, Ni is bonded to four equivalent Cr and eight equivalent Ni atoms to form NiCr4Ni8 cuboctahedra that share corners with twelve NiCr4Ni8 cuboctahedra, edges with eight equivalent AlNi12 cuboctahedra, edges with sixteen equivalent NiAl2Cr2Ni8 cuboctahedra, faces with four equivalent CrNi12 cuboctahedra, and faces with fourteen NiAl2Cr2Ni8 cuboctahedra. All Ni–Ni bond lengths are 2.48 Å. In the second Ni site, Ni is bonded to eight Ni and four equivalent Al atoms to form distorted NiAl4Ni8 cuboctahedra that share corners with twelve NiCr4Ni8 cuboctahedra, edges with four equivalent CrNi12 cuboctahedra, edges with four equivalent AlNi12 cuboctahedra, edges with sixteen NiAl2Cr2Ni8 cuboctahedra, faces with four equivalent AlNi12 cuboctahedra, and faces with fourteen NiCr4Ni8 cuboctahedra. There are four shorter (2.51 Å) and four longer (2.53 Å) Ni–Ni bond lengths. All Ni–Al bond lengths are 2.50 Å. In the third Ni site, Ni is bonded to eight Ni and four equivalent Al atoms to form NiAl4Ni8 cuboctahedra that share corners with twelve NiAl4Ni8 cuboctahedra, edges with eight 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 2.51 Å. All Ni–Al bond lengths are 2.50 Å. In the fourth Ni site, Ni is bonded to two equivalent Cr, eight Ni, and two equivalent Al atoms to form NiAl2Cr2Ni8 cuboctahedra that share corners with twelve NiAl2Cr2Ni8 cuboctahedra, edges with four equivalent CrNi12 cuboctahedra, edges with four equivalent AlNi12 cuboctahedra, edges with sixteen NiCr4Ni8 cuboctahedra, faces with two equivalent CrNi12 cuboctahedra, faces with two equivalent AlNi12 cuboctahedra, and faces with fourteen NiCr4Ni8 cuboctahedra. All Ni–Ni bond lengths are 2.50 Å. Both Ni–Al bond lengths are 2.55 Å. In the fifth Ni site, Ni is bonded to eight Ni and four Al atoms to form NiAl4Ni8 cuboctahedra that share corners with twelve NiAl2Cr2Ni8 cuboctahedra, edges with eight AlNi12 cuboctahedra, edges with sixteen NiAl4Ni8 cuboctahedra, faces with four AlNi12 cuboctahedra, and faces with fourteen NiAl4Ni8 cuboctahedra. All Ni–Ni bond lengths are 2.50 Å. There are two shorter (2.50 Å) and two longer (2.52 Å) Ni–Al bond lengths. In the sixth Ni site, Ni is bonded to eight Ni and four equivalent Al atoms to form 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–Ni bond lengths are 2.50 Å. All Ni–Al bond lengths are 2.51 Å. There are two inequivalent Al sites. In the first Al site, Al is bonded to twelve Ni atoms to form AlNi12 cuboctahedra that share corners with four equivalent CrNi12 cuboctahedra, corners with eight AlNi12 cuboctahedra, edges with twenty-four NiAl2Cr2Ni8 cuboctahedra, a faceface with one CrNi12 cuboctahedra, faces with five AlNi12 cuboctahedra, and faces with twelve NiAl4Ni8 cuboctahedra. In the second Al site, Al is bonded to twelve Ni atoms to form AlNi12 cuboctahedra that share corners with twelve AlNi12 cuboctahedra, edges with twenty-four NiAl4Ni8 cuboctahedra, faces with six AlNi12 cuboctahedra, and faces with twelve NiAl4Ni8 cuboctahedra.