DOE OSTI2020
UIr2Si2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. U is bonded in a 8-coordinate geometry to eight Ir and eight Si atoms. There are four shorter (3.11 Å) and four longer (3.25 Å) U–Ir bond lengths. There are four shorter (3.14 Å) and four longer (3.17 Å) U–Si bond lengths. There are two inequivalent Ir sites. In the first Ir site, Ir is bonded in a 9-coordinate geometry to four equivalent U and five Si atoms. There are one shorter (2.35 Å) and four longer (2.41 Å) Ir–Si bond lengths. In the second Ir site, Ir is bonded to four equivalent U and four equivalent Si atoms to form distorted IrU4Si4 tetrahedra that share corners with twelve equivalent SiU4Ir4 tetrahedra, edges with two equivalent SiU4Ir4 tetrahedra, edges with four equivalent IrU4Si4 tetrahedra, and faces with four equivalent IrU4Si4 tetrahedra. All Ir–Si bond lengths are 2.44 Å. There are two inequivalent Si sites. In the first Si site, Si is bonded in a 9-coordinate geometry to four equivalent U and five Ir atoms. In the second Si site, Si is bonded to four equivalent U and four equivalent Ir atoms to form distorted SiU4Ir4 tetrahedra that share corners with twelve equivalent IrU4Si4 tetrahedra, edges with two equivalent IrU4Si4 tetrahedra, edges with four equivalent SiU4Ir4 tetrahedra, and faces with four equivalent SiU4Ir4 tetrahedra.