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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >NMR solvent shifts of acetonitrile from frozen density embedding calculations
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NMR solvent shifts of acetonitrile from frozen density embedding calculations

机译：冷冻密度嵌入计算得出乙腈的NMR溶剂位移

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摘要

We present a density functional theory (DFT) study of solvent effects on nuclear magnetic shielding parameters. As a test example we have focused on the sensitive nitrogen shift of acetonitrile immersed in a selected set of solvents, namely water, chloroform, and cyclohexane. To include the effect of the solvent environment in an accurate and efficient manner, we employed the frozen-density embedding (FDE) scheme. We have included up to 500 solvent molecules in the NMR computations and obtained the cluster geometries from a large set of conformations generated with molecular dynamics. For small solute-solvent clusters comparison of the FDE results with conventional supermolecular DFT calculations shows close agreement. For the large solute-solvent clusters the solvent shift values are compared with experimental data and with values obtained using continuum solvent models. For the water -> cyclohexane shift the obtained Value is in very good agreement with experiments. For the water -> chloroform NMR solvent shift the classical force field used in the molecular dynamics simulations is found to introduce an error. This error can be largely avoided by using geometries taken from Car-Parrinello molecular dynamics simulations.
机译：我们提出密度泛函理论（DFT）研究溶剂对核磁屏蔽参数的影响。作为测试示例，我们重点研究了浸入选定溶剂（即水，氯仿和环己烷）中的乙腈的灵敏氮转移。为了以准确有效的方式包括溶剂环境的影响，我们采用了冷冻密度嵌入（FDE）方案。我们在NMR计算中包括了多达500个溶剂分子，并从通过分子动力学生成的大量构象中获得了簇的几何形状。对于小的溶质-溶剂簇，FDE结果与常规超分子DFT计算的比较显示出紧密的一致性。对于较大的溶质-溶剂簇，将溶剂位移值与实验数据以及使用连续溶剂模型获得的值进行比较。对于水→环己烷的转化，获得的值与实验非常吻合。对于水→氯仿NMR溶剂位移，发现分子动力学模拟中使用的经典力场会引入误差。通过使用取自Car-Parrinello分子动力学模拟的几何形状，可以很大程度上避免此错误。

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