Fully Relativistic ab initio Dirac-Coulomb Calculations

For accurate calculations of the electronic structures of the heaviest elements and their compounds, where relativistic effects are of paramount importance, the usage of fully relativistic quantum chemical methods within 4component approximation is highly desirable. Such a usage encountered until recently difficulties for many electron systems with respect to the treatment of the electron correlation. Meanwhile, this problem has been tackled, and the latest version of the DIRAC package offers possibility of calculating the electronic structure of the heavy element compounds using the DC (Dirac-Coulomb) Hamiltonian and treating the electron correlation at various levels of theory including the most sophisticated, such as the Coupled Cluster Single Double (Triple) excitations [CCSD(T)] [1]. Meanwhile, optimal basis sets for the heaviest elements have also been developed [2]. In this work, we have made use of the recent developments in the DIRAC program and calculated atomic properties of Hg and element 112 at a very advanced level of theory. In the basis of the DC method lies the many-electron relativistic Dirac-Coulomb Hamiltonian