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HfSi crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Hf4+ is bonded in a 7-coordinate geometry to seven equivalent Si4- atoms. There are a spread of Hf–Si bond distances ranging from 2.71–2.91 Å. Si4- is bonded in a 9-coordinate geometry to seven equivalent Hf4+ and two equivalent Si4- atoms. Both Si–Si bond lengths are 2.47 Å.
HfSi2 is Zirconium Disilicide structured and crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Hf is bonded in a 10-coordinate geometry to ten Si atoms. There are a spread of Hf–Si bond distances ranging from 2.70–2.96 Å. There are two inequivalent Si sites. In the first Si site, Si is bonded in a 8-coordinate geometry to six equivalent Hf and two equivalent Si atoms. Both Si–Si bond lengths are 2.42 Å. In the second Si site, Si is bonded in a 8-coordinate geometry to four equivalent Hf and four equivalent Si atoms. All Si–Si bond lengths are 2.60 Å.
Hf5Si3 crystallizes in the hexagonal P6_3/mcm space group. The structure is three-dimensional. there are two inequivalent Hf sites. In the first Hf site, Hf is bonded in a 5-coordinate geometry to five equivalent Si atoms. There are a spread of Hf–Si bond distances ranging from 2.71–2.96 Å. In the second Hf site, Hf is bonded in a 6-coordinate geometry to six equivalent Si atoms. All Hf–Si bond lengths are 2.80 Å. Si is bonded in a 9-coordinate geometry to nine Hf atoms.
Hf5Si4 crystallizes in the tetragonal P4_12_12 space group. The structure is three-dimensional. there are three inequivalent Hf sites. In the first Hf site, Hf is bonded to six Si atoms to form corner-sharing HfSi6 octahedra. The corner-sharing octahedral tilt angles are 53°. There are a spread of Hf–Si bond distances ranging from 2.71–2.84 Å. In the second Hf site, Hf is bonded in a 7-coordinate geometry to seven Si atoms. There are a spread of Hf–Si bond distances ranging from 2.73–3.09 Å. In the third Hf site, Hf is bonded in a 6-coordinate geometry to six Si atoms. There are a spread of Hf–Si bond distances ranging from 2.61–2.76 Å. There are two inequivalent Si sites. In the first Si site, Si is bonded in a 9-coordinate geometry to eight Hf and one Si atom. The Si–Si bond length is 2.50 Å. In the second Si site, Si is bonded in a 9-coordinate geometry to eight Hf and one Si atom.
Hf3Si2 crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. there are two inequivalent Hf sites. In the first Hf site, Hf is bonded in a 6-coordinate geometry to six equivalent Si atoms. There are two shorter (2.73 Å) and four longer (2.80 Å) Hf–Si bond lengths. In the second Hf site, Hf is bonded in a square co-planar geometry to four equivalent Si atoms. All Hf–Si bond lengths are 2.78 Å. Si is bonded in a 9-coordinate geometry to eight Hf and one Si atom. The Si–Si bond length is 2.46 Å.
Hf2Si is Khatyrkite structured and crystallizes in the tetragonal I4/mcm space group. The structure is three-dimensional. Hf is bonded in a 4-coordinate geometry to four equivalent Si atoms. All Hf–Si bond lengths are 2.80 Å. Si is bonded in a 10-coordinate geometry to eight equivalent Hf and two equivalent Si atoms. Both Si–Si bond lengths are 2.60 Å.
Hf3Si is Uranium Silicide-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Hf is bonded to eight equivalent Hf and four equivalent Si atoms to form distorted HfHf8Si4 cuboctahedra that share corners with four equivalent SiHf12 cuboctahedra, corners with fourteen equivalent HfHf8Si4 cuboctahedra, edges with six equivalent SiHf12 cuboctahedra, edges with twelve equivalent HfHf8Si4 cuboctahedra, faces with four equivalent SiHf12 cuboctahedra, and faces with sixteen equivalent HfHf8Si4 cuboctahedra. There are a spread of Hf–Hf bond distances ranging from 2.96–3.11 Å. There are two shorter (2.98 Å) and two longer (3.03 Å) Hf–Si bond lengths. Si is bonded to twelve equivalent Hf atoms to form SiHf12 cuboctahedra that share corners with six equivalent SiHf12 cuboctahedra, corners with twelve equivalent HfHf8Si4 cuboctahedra, edges with eighteen equivalent HfHf8Si4 cuboctahedra, faces with eight equivalent SiHf12 cuboctahedra, and faces with twelve equivalent HfHf8Si4 cuboctahedra.