Relativistic effects on homonuclear triel clusters

The theory of relativity cannot be neglected if structures and properties of compounds containing heavy elements are discussed. The assumption of a constant speed of light implicates an increase of the mass and thus of the momentum of the electrons, especially close to the nucleus, amounting to more than 20% for the heavy elements belonging to the groups 13 – 18. One of the consequences is a relative shift of the atomic orbital energies in comparison to the values obtained from non-relativistic calculations, thus stabilizing sand p-states and destabilizing dand f-states. The impact of this effect on the crystal chemistry and the properties of compounds containing heavy elements has been studied extensively in M. Jansen’s department during the last years. It was shown that the charge transfer between the components of intermetallic phases of the noble metals gold and platinum with alkaline or alkaline earth elements is rather large, leading to isolated and Zintl-like noble metal anions. Even intermetallic salts like Cs2Pt have been synthesized. The investigation of lead and bismuth compounds under high pressure resulted in the characterization of a variety of new phases associated with the inert pair effect, which is a consequence of the stabilization of the atomic s-states.