Iuliucci Robbie J, Hartman Joshua D, Beran Gregory J O
Department of Chemistry, Washington and Jefferson College, Washington, Pennsylvania 15301 United States.
Department of Chemistry, University of California, Riverside, California 92521 United States.
J Phys Chem A. 2023 Mar 30;127(12):2846-2858. doi: 10.1021/acs.jpca.2c07657. Epub 2023 Mar 20.
predictions of chemical shifts and electric field gradient (EFG) tensor components are frequently used to help interpret solid-state nuclear magnetic resonance (NMR) experiments. Typically, these predictions employ density functional theory (DFT) with generalized gradient approximation (GGA) functionals, though hybrid functionals have been shown to improve accuracy relative to experiment. Here, the performance of a dozen models beyond the GGA approximation are examined for the prediction of solid-state NMR observables, including meta-GGA, hybrid, and double-hybrid density functionals and second-order Møller-Plesset perturbation theory (MP2). These models are tested on organic molecular crystal data sets containing 169 experimental C and N chemical shifts and 114 O and N EFG tensor components. To make these calculations affordable, gauge-including projector augmented wave (GIPAW) Perdew-Burke-Ernzerhof (PBE) calculations with periodic boundary conditions are combined with a local intramolecular correction computed at the higher level of theory. Within the context of typical NMR property calculations performed on a static, DFT-optimized crystal structure, the benchmarking finds that the double-hybrid DFT functionals produce errors versus experiment that are no smaller than those of hybrid functionals in the best cases, and they can be larger. MP2 errors versus experiment are even bigger. Overall, no practical advantages are found for using any of the tested double-hybrid functionals or MP2 to predict experimental solid-state NMR chemical shifts and EFG tensor components for routine organic crystals, especially given the higher computational cost of those methods. This finding likely reflects error cancellation benefiting the hybrid functionals. Improving the accuracy of the predicted chemical shifts and EFG tensors relative to experiment would probably require more robust treatments of the crystal structures, their dynamics, and other factors.
化学位移和电场梯度（EFG）张量分量的预测经常用于帮助解释固态核磁共振（NMR）实验。通常，这些预测采用具有广义梯度近似（GGA）泛函的密度泛函理论（DFT），不过已表明杂化泛函相对于实验可提高准确性。在此，研究了十几种超出GGA近似的模型对固态NMR可观测量的预测性能，包括元GGA、杂化和双杂化密度泛函以及二阶Møller-Plesset微扰理论（MP2）。这些模型在包含169个实验C和N化学位移以及114个O和N EFG张量分量的有机分子晶体数据集上进行测试。为了使这些计算可行，将具有周期性边界条件的含规范投影增强波（GIPAW）Perdew-Burke-Ernzerhof（PBE）计算与在更高理论水平计算的局部分子内校正相结合。在对静态、DFT优化的晶体结构进行的典型NMR性质计算的背景下，基准测试发现，双杂化DFT泛函与实验相比产生的误差在最佳情况下并不比杂化泛函的误差小，甚至可能更大。MP2与实验的误差甚至更大。总体而言，对于预测常规有机晶体的实验固态NMR化学位移和EFG张量分量，使用任何测试的双杂化泛函或MP2都没有实际优势，特别是考虑到这些方法的计算成本更高。这一发现可能反映了误差抵消对杂化泛函有利。相对于实验提高预测化学位移和EFG张量的准确性可能需要对晶体结构、其动力学和其他因素进行更稳健的处理。
