Improved Electrostatic Embedding for Fragment-Based Chemical Shift Calculations in Molecular Crystals
Improved Electrostatic Embedding for Fragment-Based Chemical Shift Calculations in Molecular Crystals
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DOI：
10.1021/acs.jctc.7b00677
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发表时间：
2017-12-01
影响因子：
5.5
通讯作者：
Beran, Gregory J. O.
中科院分区：
文献类型：
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作者：
Hartman, Joshua D.;Balaji, Ashwin;Beran, Gregory J. O.
基于碎片的方法预测分子晶体中的核磁共振化学屏蔽张量具有很高的精度和计算效率。这种方法通常使用静电包埋来模拟结晶环境，并且结果的质量可能对包埋处理敏感。为了提高基于碎片的分子晶体性质计算的嵌入环境的质量，我们借鉴了嵌入离子方法的思想，引入了自洽极化的马德隆场效应。本文发展的Madelung势(SCRMP)模型的自洽复制构造了一个点电荷阵列，该阵列结合了自洽的晶格极化，并在涉及系统量子力学区域的所有原子位置再现了Madelung势。评估了使用SCRMP和密度泛函如PBE和PBE0对基于碎片和基于簇的H-1、C-13、N-14和O-17化学位移预测的性能。改进的嵌入模型导致了预测的O-17化学位移的实质性改进和N-15化学位移的轻微改进。最后，通过考察甘氨酸具有挑战性的伽马多晶型中两个氧化学位移的分配，验证了该模型的性能。总体而言，嵌入SCRMP的核磁共振化学位移预测与广泛使用的包括投影仪增强波(GIPAW)模型获得的预测相同或更准确。
Fragment-based methods predict nuclear magnetic resonance (NMR) chemical shielding tensors in molecular crystals with high accuracy and computational efficiency. Such methods typically employ electrostatic embedding to mimic the crystalline environment, and the quality of the results can be sensitive to the embedding treatment. To improve the quality of this embedding environment for fragment-based molecular crystal property calculations, we borrow ideas from the embedded ion method to incorporate self-consistently polarized Madelung field effects. The self-consistent reproduction of the Madelung potential (SCRMP) model developed here constructs an array of point charges that incorporates self-consistent lattice polarization and which reproduces the Madelung potential at all atomic sites involved in the quantum mechanical region of the system. The performance of fragment- and cluster-based H-1, C-13, N-14, and O-17 chemical shift predictions using SCRMP and density functionals like PBE and PBE0 are assessed. The improved embedding model results in substantial improvements in the predicted O-17 chemical shifts and modest improvements in the N-15 ones. Finally, the performance of the model is demonstrated by examining the assignment of the two oxygen chemical shifts in the challenging gamma-polymorph of glycine. Overall, the SCRMP-embedded NMR chemical shift predictions are on par with or more accurate than those obtained with the widely used gauge-including projector augmented wave (GIPAW) model.