Molecular relativistic calculations of the electric field gradients at the nuclei in the hydrogen halides

Abstract

Fully relativistic four-component self-consistent field and correlated calculations at the Mo "llerPlesset second-order perturbation theory level ͑MP2͒ have been performed for the monofluorides and mono-and trihydrides of lanthanum, lutetium, actinium, and lawrencium. The calculated spectroscopic constants are in good agreement with available experimental data. The calculated bond lengths have been compared with values from nonrelativistic calculations to give an estimate of the effect of relativity on the molecular lanthanide and actinide contraction. The calculated lanthanide contraction at the relativistic MP2 level is 0.12, 0.12, and 0.19 Å for the monohydrides, monofluorides, and trihydrides, respectively. The corresponding results for the actinides are 0.20, 0.15, and 0.28 Å, and we demonstrate that the larger size of the actinide contraction is a consequence of relativistic effects. Between 10% and 30% of the lanthanide contraction and between 40% and 50% of the actinide contraction is caused by relativity in these compounds.

Analytic high-order Douglas-Kroll-Hess electric field gradients

“…Steep functions of higher angular momentum hardly contribute to the electronic energy of the molecules under investigation, but they tend to diminish the expectation value of the EFG. This effect was also observed by Visscher et al 30 The basis sets used in Ref. 20 …”

“…21 smaller than those published by Neese et al, 21 Malkin et al, 20 and Visscher et al 30 This is likely to be due to the additional tight polarization functions in our work. Steep functions of higher angular momentum hardly contribute to the electronic energy of the molecules under investigation, but they tend to diminish the expectation value of the EFG.…”

“…Since only the electronic contribution to the EFG was published by Malkin et al, we have evaluated the missing nuclear contribution and complemented the original data set. In addition, we compare to the finite-field results of Visscher et al, 30 which depend on this numerical model but incorporate electron correlation effects. The corresponding data can be found in Table XI.…”

“…III were primarily generated to yield an accurate EFG close to the limit within the approximations involved, i.e., under neglect of spin-orbit coupling and using a single Slater determinant as an approximation for the wave function. They were not fully optimized with respect to the electronic energy, but they perform better with respect to the energy and EFG than the basis sets used in previous studies 21,30 on the halogen series.…”

Relativistic calculations of magnetic resonance parameters: background and some recent developments

“…Correspondingly, PC effects can be large for the EFG [77][78][79][80][81]. Selected examples are discussed in §8.…”