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NiSi2 is Fluorite structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Ni is bonded in a body-centered cubic geometry to eight equivalent Si atoms. All Ni–Si bond lengths are 2.35 Å. Si is bonded to four equivalent Ni and six equivalent Si atoms to form a mixture of distorted corner, edge, and face-sharing SiSi6Ni4 tetrahedra. All Si–Si bond lengths are 2.72 Å.
Sc3(NiSi2)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are three inequivalent Sc2+ sites. In the first Sc2+ site, Sc2+ is bonded in a 7-coordinate geometry to seven Si2- atoms. There are a spread of Sc–Si bond distances ranging from 2.61–2.85 Å. In the second Sc2+ site, Sc2+ is bonded in a 8-coordinate geometry to eight Si2- atoms. There are a spread of Sc–Si bond distances ranging from 2.83–3.02 Å. In the third Sc2+ site, Sc2+ is bonded in a 6-coordinate geometry to seven Si2- atoms. There are a spread of Sc–Si bond distances ranging from 2.68–3.15 Å. There are two inequivalent Ni1+ sites. In the first Ni1+ site, Ni1+ is bonded to five Si2- atoms to form distorted NiSi5 square pyramids that share corners with two equivalent NiSi5 square pyramids, a cornercorner with one NiSi4 tetrahedra, and edges with two equivalent NiSi5 square pyramids. There are a spread of Ni–Si bond distances ranging from 2.33–2.42 Å. In the second Ni1+ site, Ni1+ is bonded to four Si2- atoms to form NiSi4 tetrahedra that share a cornercorner with one NiSi5 square pyramid, corners with two equivalent NiSi4 tetrahedra, and edges with two equivalent NiSi4 tetrahedra. There are a spread of Ni–Si bond distances ranging from 2.27–2.35 Å. There are four inequivalent Si2- sites. In the first Si2- site, Si2- is bonded in a 9-coordinate geometry to six Sc2+, two Ni1+, and one Si2- atom. The Si–Si bond length is 2.41 Å. In the second Si2- site, Si2- is bonded in a 1-coordinate geometry to four Sc2+, three equivalent Ni1+, and two equivalent Si2- atoms. Both Si–Si bond lengths are 2.54 Å. In the third Si2- site, Si2- is bonded in a 10-coordinate geometry to six Sc2+, three equivalent Ni1+, and one Si2- atom. The Si–Si bond length is 2.43 Å. In the fourth Si2- site, Si2- is bonded in a 9-coordinate geometry to six Sc2+, one Ni1+, and two Si2- atoms.
U2(NiSi2)3 crystallizes in the orthorhombic Cmmm space group. The structure is three-dimensional. U5+ is bonded in a 10-coordinate geometry to ten Si+2.67- atoms. There are a spread of U–Si bond distances ranging from 3.00–3.08 Å. There are two inequivalent Ni2+ sites. In the first Ni2+ site, Ni2+ is bonded in a 5-coordinate geometry to five Si+2.67- atoms. There are one shorter (2.25 Å) and four longer (2.29 Å) Ni–Si bond lengths. In the second Ni2+ site, Ni2+ is bonded in a body-centered cubic geometry to eight Si+2.67- atoms. All Ni–Si bond lengths are 2.36 Å. There are three inequivalent Si+2.67- sites. In the first Si+2.67- site, Si+2.67- is bonded in a 4-coordinate geometry to two equivalent U5+, four Ni2+, and five Si+2.67- atoms. There are one shorter (2.54 Å) and four longer (2.81 Å) Si–Si bond lengths. In the second Si+2.67- site, Si+2.67- is bonded in a 4-coordinate geometry to two equivalent U5+, four Ni2+, and five Si+2.67- atoms. The Si–Si bond length is 2.55 Å. In the third Si+2.67- site, Si+2.67- is bonded in a 9-coordinate geometry to six equivalent U5+, one Ni2+, and two equivalent Si+2.67- atoms. Both Si–Si bond lengths are 2.33 Å.