Relativistic calculations of electric field gradients using the Douglas–Kroll method

Abstract

In this work, the analytical evaluation of Douglas–Kroll (DK) transformed electric field gradient (EFG) integrals was implemented. This allowed us for the first time to perform fully analytical and picture-change consistent calculations of nuclear quadrupole coupling constants in the framework of the DK method. Only scalar relativistic effects were taken into consideration in the present work. The method was applied to the calculation on a series of molecules at both Hartree–Fock and density functional levels of theory. The results were compared to the so-called point charge nuclear quadrupole model (PCNQM) numerical method. The results showed that, for the set of compounds investigated, the second-order DK transformation of the EFG integrals plays only a minor role in comparison with the first-order terms.