Relativistic corrections of the electric field gradient in dihalogen molecules XY (X, Y = F, Cl, Br, I, At) within the linear response elimination of the small component formalism

Abstract

We analyze the performance of the linear response elimination of the small component (LRESC) scheme to describe the electric field gradient (EFG), in dihalogen molecular systems, and also to give insight of the relativistic corrections. LRESC shows a good performance, providing results close to four-component (4c) ones for molecules containing atoms belonging up to the fifth row of the Periodic Table. When heavier nuclei are involved the difference among LRESC and 4c values reaches up to 5%. The main relativistic correction represents 80% of the nonrelativistic part for the heaviest molecule. LRESC can be applied at Hartree–Fock as well as Density Functional Theory levels, therefore we also analyze correlation effects on EFG showing that relativity enhances correlation effects and both effects are not additive. As an application of LRESC method, nuclear quadrupole moment calculations of some halogen nuclei are also carried out and compared with the most recent data.