RELATIVISTIC EFFECTS OF P-BLOCK MOLECULES

Density functional calculations including relativistic as well as nonlocal exchange and correlation corrections have been performed on group 14 molecules MO, MH(4), MCl(4) (M = C, Si, Ge, Sn, Pb). Good bond lengths, and reasonable bond energies and force constants have been obtained. The dipole moments of the MO series are quite good, and d mu/dR of CO is close to the experimental results. Relativistic corrections are important for the heavier molecules (M = Ge, Sn, Pb). Fractional. relativistic changes of bond energies, bond lengths and force constants are nearly exactly proportional to Z(2) (Z: heavy nuclear charge). The origin of the relativistic changes has been analyzed: the change upon bond formation of the valence orbitals near the heavy nucleus is decisive.