DOE OSTI2020
U3Hg is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent U sites. In the first U site, U is bonded to eight U and four equivalent Hg atoms to form distorted UU8Hg4 cuboctahedra that share corners with twelve equivalent UU8Hg4 cuboctahedra, edges with eight equivalent HgU12 cuboctahedra, edges with sixteen UU8Hg4 cuboctahedra, faces with four equivalent HgU12 cuboctahedra, and faces with fourteen UU8Hg4 cuboctahedra. There are four shorter (3.12 Å) and four longer (3.18 Å) U–U bond lengths. All U–Hg bond lengths are 3.12 Å. In the second U site, U is bonded to eight equivalent U and four equivalent Hg atoms to form distorted UU8Hg4 cuboctahedra that share corners with four equivalent UU8Hg4 cuboctahedra, corners with eight equivalent HgU12 cuboctahedra, edges with twenty-four UU8Hg4 cuboctahedra, faces with six equivalent HgU12 cuboctahedra, and faces with twelve UU8Hg4 cuboctahedra. All U–Hg bond lengths are 3.18 Å. Hg is bonded to twelve U atoms to form HgU12 cuboctahedra that share corners with four equivalent HgU12 cuboctahedra, corners with eight equivalent UU8Hg4 cuboctahedra, edges with eight equivalent HgU12 cuboctahedra, edges with sixteen equivalent UU8Hg4 cuboctahedra, faces with four equivalent HgU12 cuboctahedra, and faces with fourteen UU8Hg4 cuboctahedra.