DOE OSTI2019
HfWSi crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. there are two inequivalent Hf sites. In the first Hf site, Hf is bonded in a 12-coordinate geometry to five W and seven Si atoms. There are a spread of Hf–W bond distances ranging from 3.07–3.09 Å. There are a spread of Hf–Si bond distances ranging from 3.05–3.12 Å. In the second Hf site, Hf is bonded in a 12-coordinate geometry to seven W and five Si atoms. There are a spread of Hf–W bond distances ranging from 3.05–3.10 Å. There are a spread of Hf–Si bond distances ranging from 2.98–3.13 Å. There are three inequivalent W sites. In the first W site, W is bonded to six Hf and six Si atoms to form WHf6Si6 cuboctahedra that share corners with four equivalent SiHf6Si2W4 cuboctahedra, corners with fourteen WHf6Si6 cuboctahedra, edges with six WHf6Si2W4 cuboctahedra, faces with four equivalent WHf6Si2W4 cuboctahedra, and faces with six equivalent SiHf6Si2W4 cuboctahedra. There are a spread of W–Si bond distances ranging from 2.55–2.64 Å. In the second W site, W is bonded to six Hf, four W, and two equivalent Si atoms to form distorted WHf6Si2W4 cuboctahedra that share corners with four equivalent SiHf6Si2W4 cuboctahedra, corners with eight WHf6Si2W4 cuboctahedra, edges with two equivalent WHf6Si2W4 cuboctahedra, faces with six equivalent SiHf6Si2W4 cuboctahedra, and faces with ten WHf6Si6 cuboctahedra. There are a spread of W–W bond distances ranging from 2.57–2.70 Å. Both W–Si bond lengths are 2.61 Å. In the third W site, W is bonded to six Hf, four equivalent W, and two equivalent Si atoms to form distorted WHf6Si2W4 cuboctahedra that share corners with four equivalent SiHf6Si2W4 cuboctahedra, corners with six WHf6Si6 cuboctahedra, edges with six WHf6Si2W4 cuboctahedra, faces with six equivalent SiHf6Si2W4 cuboctahedra, and faces with eight equivalent WHf6Si2W4 cuboctahedra. Both W–Si bond lengths are 2.63 Å. There are two inequivalent Si sites. In the first Si site, Si is bonded to six Hf, four W, and two equivalent Si atoms to form distorted SiHf6Si2W4 cuboctahedra that share corners with eight WHf6Si6 cuboctahedra, edges with six equivalent SiHf6Si2W4 cuboctahedra, faces with two equivalent SiHf6Si2W4 cuboctahedra, and faces with twelve WHf6Si6 cuboctahedra. Both Si–Si bond lengths are 2.73 Å. In the second Si site, Si is bonded in a 12-coordinate geometry to six Hf, two equivalent W, and four Si atoms. There are one shorter (2.46 Å) and one longer (2.85 Å) Si–Si bond lengths.