DOE OSTI2020
EuNiSi3 crystallizes in the tetragonal I-4m2 space group. The structure is three-dimensional. Eu2+ is bonded to twelve Si+1.33- atoms to form EuSi12 cuboctahedra that share corners with eight equivalent EuSi12 cuboctahedra, corners with eight equivalent SiEu4Si4Ni4 cuboctahedra, edges with four equivalent EuSi12 cuboctahedra, edges with four equivalent SiEu4Si4Ni4 cuboctahedra, edges with eight equivalent NiSi8 tetrahedra, faces with four equivalent EuSi12 cuboctahedra, and faces with four equivalent NiSi8 tetrahedra. There are eight shorter (3.16 Å) and four longer (3.21 Å) Eu–Si bond lengths. Ni2+ is bonded to eight Si+1.33- atoms to form distorted NiSi8 tetrahedra that share corners with four equivalent NiSi8 tetrahedra, edges with four equivalent SiEu4Si4Ni4 cuboctahedra, edges with eight equivalent EuSi12 cuboctahedra, faces with four equivalent EuSi12 cuboctahedra, and faces with four equivalent NiSi8 tetrahedra. There are four shorter (2.40 Å) and four longer (2.92 Å) Ni–Si bond lengths. There are two inequivalent Si+1.33- sites. In the first Si+1.33- site, Si+1.33- is bonded in a 9-coordinate geometry to four equivalent Eu2+, two equivalent Ni2+, and three Si+1.33- atoms. There are two shorter (2.40 Å) and one longer (2.45 Å) Si–Si bond lengths. In the second Si+1.33- site, Si+1.33- is bonded to four equivalent Eu2+, four equivalent Ni2+, and four equivalent Si+1.33- atoms to form distorted SiEu4Si4Ni4 cuboctahedra that share corners with eight equivalent EuSi12 cuboctahedra, corners with twelve equivalent SiEu4Si4Ni4 cuboctahedra, edges with four equivalent EuSi12 cuboctahedra, edges with four equivalent NiSi8 tetrahedra, and faces with four equivalent SiEu4Si4Ni4 cuboctahedra.