Accurate potential energy curves for the group 12 dimers Zn, Cd, and Hg.

Potential energy curves of the electronic ground states of the group 12 dimers Zn and Cd were computed at the CCSD(T) level of theory, including full triple corrections $$\Updelta$$T in the coupled-cluster procedure, and spin-orbit (SO) contributions from four-component coupled-cluster calculations, extrapolated to the complete basis set (CBS) limit. For Hg, the potential energy curve published recently (Pahl et al. in J Chem Phys 132:114301, ] is complemented in this work by non-relativistic calculations to quantify and discuss relativistic effects. We obtain very accurate fits of our CBS/CCSD(T) and CBS/CCSD(T)+ $$\Updelta$$T data points to an analytically simple and computationally efficient extended Lennard Jones form. For the CBS/CCSD(T)+ $$\Updelta$$T+SO curves, we obtain dissociation energies of D = 226 cm and D = 319 cm for Zn and Cd respectively, in very good agreement with recent theoretical calculations and experimental data. We also present equilibrium distances and rotational and vibrational spectroscopic constants to compare with available theoretical and experimental data. The results obtained for non-relativistically treated Hg continue nicely the trends with increasing atom number preset by Zn and Cd, confirming that indeed, relativistic effects account for the known peculiarities for the mercury dimer. [ABSTRACT FROM AUTHOR]