Superatom-atom super-bonding in metallic clusters: a new look to the mystery of an Au20 pyramid.

Using the super valence bond model, a generalized chemical picture for the electronic shells of an Au-20 pyramid is given. It is found that Au-20 can be viewed to be a superatomic molecule, of which its superatomic 16c-16e core (T) is in (DS)-S-3 hybridization bonded with four vertical Au atoms for the molecule-like (TAu4) electronic shell-closure. Based on such a superatom-atom bonding model, TX4 (X = F, Cl, or Br) are predicted to be very stable. Such a superatom-atom T-Au/T-X bonding enriches the scope of chemistry.