Franzke Yannick J, Holzer Christof, Mack Fabian
Fachbereich Chemie, Philipps-Universität Marburg, 35032 Marburg, Germany.
Institute of Theoretical Solid State Physics, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany.
J Chem Theory Comput. 2022 Feb 8;18(2):1030-1045. doi: 10.1021/acs.jctc.1c00999. Epub 2022 Jan 4.
We present the first steps to extend the Green's function method and the Bethe-Salpeter equation (BSE) to molecular response properties such as nuclear magnetic resonance (NMR) indirect spin-spin coupling constants. We discuss both a nonrelativistic one-component and a quasi-relativistic two-component formalism. The latter describes scalar-relativistic and spin-orbit effects and allows us to study heavy-element systems with reasonable accuracy. Efficiency is maintained by the application of the resolution of the identity approximation throughout. The performance is demonstrated using conventional central processing units (CPUs) and modern graphics processing units (GPUs) for molecules involving several thousand basis functions. Our results show that a large amount of Hartree-Fock exchange is vital to provide a sufficient Kohn-Sham starting point to compute the quasi-particle energies. As the -BSE approach is generally less accurate for triplet excitations or related properties such as the Fermi-contact interaction, the admixture of the Kohn-Sham correlation kernel through the contracted BSE (cBSE) method improves the results for NMR coupling constants. This leads to remarkable results when combined with the eigenvalue-only self-consistent variant (ev) and Becke's half and half functional (BH&HLYP) or the CAM-QTP family. The developed methodology is used to calculate the Karplus curve of tin molecules, illustrating its applicability to extended chemically relevant molecules. Here, the -cBSE method improves upon the chosen BH&HLYP Kohn-Sham starting points.
我们展示了将格林函数方法和贝塞耳-萨尔皮特方程（BSE）扩展到分子响应性质（如核磁共振（NMR）间接自旋-自旋耦合常数）的初步步骤。我们讨论了非相对论单组分和准相对论双组分形式体系。后者描述了标量相对论和自旋轨道效应，并使我们能够以合理的精度研究重元素体系。通过始终应用单位分解近似来保持效率。使用传统的中央处理器（CPU）和现代图形处理器（GPU）对涉及数千个基函数的分子进行了性能演示。我们的结果表明，大量的哈特里-福克交换对于提供足够的科恩-沙姆起始点来计算准粒子能量至关重要。由于BSE方法对于三重态激发或相关性质（如费米接触相互作用）通常不太准确，通过收缩BSE（cBSE）方法混合科恩-沙姆相关核可改善NMR耦合常数的结果。当与仅特征值自洽变体（ev）以及贝克半半泛函（BH&HLYP）或CAM-QTP族相结合时，这会产生显著的结果。所开发的方法用于计算锡分子的卡普拉斯曲线，说明了其对扩展的化学相关分子的适用性。在此，cBSE方法改进了所选的BH&HLYP科恩-沙姆起始点。
