Ionization potentials of Zn, Cd, Hg and dipole polarizabilities of Zn+, Cd+, Hg+: correlation and relativistic effects

The ionization potentials (IPs) of the group IIB metals and the electric dipole polarizabilities of their positively charged ions were calculated using the relativistic one-component spin averaged Douglas–Kroll (DK) no pair approximation combined with the CCSD(T) treatment of the electron correlation. Ionization potentials 9.393 (9.394) eV for Zn and 8.941 (8.993) eV for Cd agree with experimental values (in parentheses) excellently and the IP for Hg, 10.362 (10.437) eV agrees with experiment reasonably well. The three factors that can affect the accuracy, i.e. basis set effects, electron correlation and relativistic effects, were carefully examined.