DOE OSTI2020
Rb3Ac is Uranium Silicide-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent Rb sites. In the first Rb site, Rb is bonded to eight Rb and four equivalent Ac atoms to form RbRb8Ac4 cuboctahedra that share corners with twelve equivalent RbRb8Ac4 cuboctahedra, edges with eight equivalent RbRb8Ac4 cuboctahedra, edges with eight equivalent AcRb12 cuboctahedra, faces with four equivalent AcRb12 cuboctahedra, and faces with ten equivalent RbRb8Ac4 cuboctahedra. There are four shorter (4.48 Å) and four longer (4.77 Å) Rb–Rb bond lengths. All Rb–Ac bond lengths are 4.77 Å. In the second Rb site, Rb is bonded in a distorted square co-planar geometry to eight equivalent Rb and four equivalent Ac atoms. All Rb–Ac bond lengths are 4.48 Å. Ac is bonded to twelve Rb atoms to form AcRb12 cuboctahedra that share corners with four equivalent AcRb12 cuboctahedra, edges with eight equivalent AcRb12 cuboctahedra, edges with sixteen equivalent RbRb8Ac4 cuboctahedra, faces with four equivalent AcRb12 cuboctahedra, and faces with eight equivalent RbRb8Ac4 cuboctahedra.