@X@user.full_name@X@ @GMU: RbF has a face-centered cubic uni…

@X@user.full_name@X@ @GMU: RbF has a face-centered cubic unit cell in which the F- anions occupy corners and face centers, while the cations fit into the hole between adjacent anions. What is its density if the ionic radii of Rb+, F- ions are 154.2 pm and 136.0 pm, respectively?