论文标题
对核磁屏蔽的空间贡献
Spatial contributions to nuclear magnetic shieldings
论文作者
论文摘要
我们开发了一种用于计算，分析和可视化核磁屏蔽密度的方法，这些密度是通过生物 - 避免关系从电流密度计算的。可以通过BECKE分区方案在我们的框架内估算对核磁屏蔽常数的原子贡献。新功能已在GIMIC程序中实施，并在此工作中应用于苯苯（c $ _6 $ _6 $ H $ _6 $）和cyclobutadiene（C $ _4 $ h $ _4 $ _4 $ _4 $）的$^1 $ h和$^1 $ h和$^{13} $ c核磁性屏蔽。新方法允许目视检查正（屏蔽）和负（降低）对单个核的核磁屏蔽常数的贡献，这是迄今尚未轻松完成的。对屏蔽密度的分析表明，垂直电流密度通量既可以产生屏蔽剂也产生了势不可及的贡献，因为屏蔽或防止弹药取决于相对于研究核的电流密度通量的方向，而不是屏蔽型。磁屏蔽的BECKE分配表明，磁屏蔽贡献主要来自研究的原子及其最近的邻居，从而证实了核磁屏蔽的局部特征。
We develop a methodology for calculating, analyzing and visualizing nuclear magnetic shielding densities, which are calculated from the current density via the Biot-Savart relation. Atomic contributions to nuclear magnetic shielding constants can be estimated within our framework with a Becke partitioning scheme. The new features have been implemented in the GIMIC program and are applied in this work to the study of the $^1$H and $^{13}$C nuclear magnetic shieldings in benzene (C$_6$H$_6$) and cyclobutadiene (C$_4$H$_4$). The new methodology allows a visual inspection of the spatial origins of the positive (shielding) and negative (deshielding) contributions to the nuclear magnetic shielding constant of a single nucleus, something which has not been hitherto easily accomplished. Analysis of the shielding densities shows that diatropic and paratropic current-density fluxes yield both shielding as well as deshielding contributions, as the shielding or deshielding is determined by the direction of the current-density flux with respect to the studied nucleus instead of the tropicity. Becke partitioning of the magnetic shieldings shows that the magnetic shielding contributions mainly originate from the studied atom and its nearest neighbors, confirming the localized character of nuclear magnetic shieldings.
