Materials Data on U4Cr7Si by Materials Project
U4Cr7Si crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. there are two inequivalent U sites. In the first U site, U is bonded in a 12-coordinate geometry to four U and twelve Cr atoms. There are one shorter (2.98 Å) and three longer (3.13 Å) U–U bond lengths. There are a spread of U–Cr bond distances ranging from 2.94–3.01 Å. In the second U site, U is bonded in a 12-coordinate geometry to four U, nine equivalent Cr, and three equivalent Si atoms. All U–U bond lengths are 3.11 Å. There are six shorter (2.93 Å) and three longer (2.96 Å) U–Cr bond lengths. All U–Si bond lengths are 2.97 Å. There are two inequivalent Cr sites. In the first Cr site, Cr is bonded to six U, five Cr, and one Si atom to form distorted CrU6Cr5Si cuboctahedra that share corners with two equivalent SiU6Cr6 cuboctahedra, corners with sixteen CrU6Cr5Si cuboctahedra, edges with six equivalent CrU6Cr5Si cuboctahedra, faces with three equivalent SiU6Cr6 cuboctahedra, and faces with fifteen CrU6Cr5Si cuboctahedra. There are a spread of Cr–Cr bond distances ranging from 2.48–2.56 Å. The Cr–Si bond length is 2.52 Å. In the second Cr site, Cr is bonded to six equivalent U and six equivalent Cr atoms to form CrU6Cr6 cuboctahedra that share corners with twelve equivalent CrU6Cr5Si cuboctahedra, edges with six equivalent CrU6Cr6 cuboctahedra, faces with two equivalent SiU6Cr6 cuboctahedra, and faces with eighteen equivalent CrU6Cr5Si cuboctahedra. Si is bonded to six equivalent U and six equivalent Cr atoms to form SiU6Cr6 cuboctahedra that share corners with twelve equivalent CrU6Cr5Si cuboctahedra, edges with six equivalent SiU6Cr6 cuboctahedra, and faces with twenty CrU6Cr6 cuboctahedra.