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Quantum Chemical Calculation of NMR for Tetramethylsilane (TMS)
Liao Xianwei,Liang Xiaoqin,Su Yu,Fan Zhijin
Author NameAffiliationE-mail
Liao Xianwei Department of ChemistrySichuan Normal University, Chengdu 610066 xuyuanxin@yahoo.com  
Liang Xiaoqin Department of ChemistrySichuan Normal University, Chengdu 610066  
Su Yu Teaching and Research Group of Chemistry, Northern Sichuan Medical College, Nanchang 637007  
Fan Zhijin State Key Laboratory of Elemental Organic Chemistry, Nankai University, Tiajin 300071  
Abstract:
The chemical shift δ is the most important parameter in analyzing NMR spectra. It is the relative value of the sample's shielding (σ-) related to the reference's shielding (σ-ref). The reference (standard) is usually tetramethylsilane (TMS) for 1H and 13C. In quantum chemistry ab initio calculation, it is necessary to calculate the absolute shielding (σref), which has been calculated by different levels of theory and methods. The calculated results are fundamentally consistent with the experimental values.
Key words:  NMR, Quantum chemistry, Shielding constant, Chemical shift, TMS
FundProject:国家自然科学基金资助(29874027)、四川省教委重点科研资助(1998-143)、南开大学元素有机化学国家重点实验室开放基金资助(第14期)项目.
TMS的NMR量子化学计算
廖显威*,梁晓琴,苏宇,范志金
摘要:
分别用HF/4-31G(Si=6-21G)、B3LYP/6-31G(D)、B3LYP/6-31G、HF/6-31G、MP2/6-31G(D)对TMS进行了结构优化,在此基础上,用Hartree-Fock、B3LYP理论水平下,分别用不同的基组6-31G、6-31++G(D,P)、6-311+G(2D,P)、6-311++G(D,P)进行NMR的计算;在MP2理论水平上,用STO-3G、3-21G、4-31G、6-31G、6-31G(D)、6-31++G(D,P)等基组进行NMR的计算.并用GAUSSION98程序所给出的四种计算NMR的方法:GIAO、IGAIM、CSGT、SINGLE GAUGE ORIGIN,分别在上述基础上进行了TMS的屏蔽值的计算.研究结果表明,就理论水平而言,DFT(B3LYP)比HF计算结果要好,而且基组越大,计算精度越高,但有一饱和基组存在.就计算方法而言,用GIAO有利于计算精度的提高.计算结果与实验值基本上吻合.
关键词:  NMR  量子化学  屏蔽常数  化学位移  TMS
DOI:10.1088/1674-0068/15/4/281-287
分类号: