DOE OSTI2020
Rb3Ta is alpha bismuth trifluoride 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 four equivalent Rb and four equivalent Ta atoms to form distorted RbRb4Ta4 cuboctahedra that share corners with eight equivalent TaRb12 cuboctahedra, corners with sixteen RbRb4Ta4 cuboctahedra, edges with four equivalent TaRb12 cuboctahedra, edges with sixteen RbRb4Ta4 cuboctahedra, and faces with six equivalent RbRb4Ta4 cuboctahedra. All Rb–Rb bond lengths are 4.19 Å. All Rb–Ta bond lengths are 4.19 Å. In the second Rb site, Rb is bonded to eight equivalent Rb and four equivalent Ta atoms to form RbRb8Ta4 cuboctahedra that share corners with eight equivalent TaRb12 cuboctahedra, corners with twenty RbRb4Ta4 cuboctahedra, edges with sixteen RbRb4Ta4 cuboctahedra, faces with four equivalent RbRb8Ta4 cuboctahedra, and faces with six equivalent TaRb12 cuboctahedra. All Rb–Ta bond lengths are 4.32 Å. Ta is bonded to twelve Rb atoms to form TaRb12 cuboctahedra that share corners with four equivalent TaRb12 cuboctahedra, corners with twenty-four RbRb4Ta4 cuboctahedra, edges with eight equivalent RbRb4Ta4 cuboctahedra, edges with eight equivalent TaRb12 cuboctahedra, faces with four equivalent TaRb12 cuboctahedra, and faces with six equivalent RbRb8Ta4 cuboctahedra.