High order relativistic corrections on the electric field gradient within the LRESC formalism

J. J. AUCAR; A. F. MALDONADO; J. I. MELO

JOURNAL OF CHEMICAL PHYSICS

AMER INST PHYSICS

Año: 2022 vol. 157 p. 244105 - 244114

0021-9606

In this work we present relativistic corrections to the electric field gradient (EFG) given by the Linear Response Elimination of the Small Component (LRESC) scheme at 1/c2 order and including for the first time spin-dependent (SD) corrections at 1/c4 order. We show that these new terms improve the performance of LRESC as results with this methodology are very close to those calculated at four-component Dirac-Hartree-Fock (4c-DHF) level. We assess the new corrections in BrY and AtY di-halogen (Y = F, Cl, Br, I, At) and XZY bi-linear molecules (Z = Zn, Cd, Hg; X,Y = F, Cl, Br, I, At). At 4c-DHF level, we analyse the contributions coming from the large and small components of therelativistic 4c wave function to the electronic part of EFG and compare them with the LRESC corrections to find their electronic origin. For HgX2 (X = Cl, Br, I) subset, when the SD correcting terms are included, LRESC calculations match very well with 4c-DHF ones and those from the literature, with differences less than 1% for molecules containing up to three heavy atoms. We show that LRESC gives accurate values of EFG allowing the analysis of the electronic origin of relativistic effects in terms of well known nonrelativistic operators.