Institute of Physical Chemistry , Karlsruhe Institute of Technology (KIT) , Kaiserstraße 12 , 76131 Karlsruhe , Germany.
Institute of Nanotechnology , Karlsruhe Institute of Technology (KIT) , Hermann-von-Helmholtz-Platz 1 , 76344 Eggenstein-Leopoldshafen , Germany.
J Chem Theory Comput. 2019 Feb 12;15(2):1028-1043. doi: 10.1021/acs.jctc.8b01084. Epub 2019 Jan 28.
An efficient formulation of scalar-relativistic NMR shielding tensors based on (one-electron) spin-free exact two-component theory (X2C) is presented. It utilizes the diagonal local approximation to the unitary decoupling matrix (DLU), which we recently applied to analytical derivatives [ J. Chem. Phys. 2018 , 148 , 104110 ]. This allows for routine calculations of large molecules with heavy atoms. Here, the computation times of the NMR shielding tensors of all nuclei formally scale cubically with the size of the system, while memory demands increase quadratically. Efficiency is demonstrated for heavy-element clusters and organometallic complexes with more than 120 atoms and 3200 contracted basis functions. The accuracy of the DLU scheme is evaluated based on C, O, Si, Ge, Sn, Xe, W, and Pb NMR shielding constants and chemical shifts using different basis sets. The finite nucleus model is available throughout.
本文提出了一种基于（单电子）无自旋精确双分量理论（X2C）的标量相对论 NMR 屏蔽张量的有效公式。它利用了幺正去耦矩阵的对角局部近似（DLU），我们最近将其应用于解析导数[J. Chem. Phys. 2018, 148, 104110]。这允许对含有重原子的大分子进行常规计算。在这里，所有核的 NMR 屏蔽张量的计算时间与系统的大小呈立方关系，而内存需求呈平方关系。对于具有超过 120 个原子和 3200 个收缩基函数的重元素团簇和有机金属配合物，证明了该方法的效率。基于不同的基组，使用 C、O、Si、Ge、Sn、Xe、W 和 Pb 的 NMR 屏蔽常数和化学位移评估了 DLU 方案的准确性。整个模型都包含有限核模型。
