Bruder Florian, Franzke Yannick J, Weigend Florian
Fachbereich Chemie, Philipps-Universität Marburg, 35032 Marburg, Germany.
J Phys Chem A. 2022 Aug 4;126(30):5050-5069. doi: 10.1021/acs.jpca.2c03579. Epub 2022 Jul 20.
The temperature-dependent Fermi-contact and pseudocontact terms are important contributions to the paramagnetic NMR shielding tensor. Herein, we augment the scalar-relativistic (local) exact two-component (X2C) framework with spin-orbit perturbation theory including the screened nuclear spin-orbit correction for the EPR hyperfine coupling and tensor to compute these temperature-dependent terms. The accuracy of this perturbative ansatz is assessed with the self-consistent spin-orbit two-component and four-component treatments serving as reference. This shows that the Fermi-contact and pseudocontact interaction is sufficiently described for paramagnetic NMR shifts; however, larger deviations are found for the EPR spectra and the principle components of the EPR properties of heavy elements. The impact of the perturbative treatment is further compared to that of the density functional approximation and the basis set. Large-scale calculations are routinely possible with the multipole-accelerated resolution of the identity approximation and the seminumerical exchange approximation, as shown for [CeTiO(OiPr)(salicylate)].
与温度相关的费米接触项和赝接触项是顺磁核磁共振屏蔽张量的重要贡献。在此，我们用自旋轨道微扰理论扩充标量相对论（局部）精确二分量（X2C）框架，该理论包括用于电子顺磁共振超精细耦合和张量的屏蔽核自旋轨道校正，以计算这些与温度相关的项。以自洽自旋轨道二分量和四分量处理作为参考来评估这种微扰假设的准确性。这表明对于顺磁核磁共振位移，费米接触和赝接触相互作用得到了充分描述；然而，对于电子顺磁共振谱和重元素电子顺磁共振性质的主分量，发现了较大偏差。进一步将微扰处理的影响与密度泛函近似和基组的影响进行了比较。如对[CeTiO(OiPr)(水杨酸盐)]所示，使用恒等式近似的多极加速分辨率和半数值交换近似，常规地进行大规模计算是可能的。
