Aucar I Agustín, Giménez Carlos A, Aucar Gustavo A
Instituto de Modelado e Innovación Tecnológica, CONICET, Departamento de Física - Facultad de Ciencias Exactas y Naturales, UNNE Av. Libertad 5460, W3404AAS Corrientes Argentina
RSC Adv. 2018 Jun 4;8(36):20234-20249. doi: 10.1039/c8ra03948h. eCollection 2018 May 30.
The nuclear charge distribution effects (NChDE) on two response properties, the NMR magnetic shielding ( ) and the nuclear spin-rotation (SR) constants ( ), are analyzed. We do it employing point-like and Gaussian-like models for describing the nuclear charge density of three linear molecules: HBr, HI and HAt. According to our results, both properties are sensitive to the NChDE. We show that the NChDE are almost completely relativistic, , they nearly vanish in the non-relativistic limit of both properties. We calculated the NChDE on and , and analyzed the differences between them in terms of a relativistic relation between these two properties. Using that relation we found that the electronic core mechanisms are the main ones for the NChDE on the shielding of nuclei of both, molecules and free atoms. The NChDE are smaller on SR constants than on shieldings. Nevertheless, within the relativistic polarization propagator formalism at the RPA level of approach they are very important for SR constants of nuclei in heavy-atom-containing compounds. Astatine in HAt has the largest influence: = -9.95 kHz for a point-like model and -50.10 kHz for a Gaussian-like model. Correlation effects must be included and we do it using different DFT schemes. The PBE0 functional gives results that are closest to experiments for Br and I, though the LDA gives the closest for hydrogen. The value of the SR constant of At is reduced among 350 kHz and 500 kHz from its RPA value, when different and usual functionals are applied. Given that the NChDE on and are mostly relativistic in their origin, these effects are also dependent on electron correlation. They have also a nonvanishing dependence with the Gaunt electron-electron interactions.
分析了核电荷分布效应（NChDE）对两种响应特性的影响，即核磁共振磁屏蔽（ ）和核自旋-旋转（SR）常数（ ）。我们采用点状和类高斯模型来描述三种线性分子HBr、HI和HAt的核电荷密度，以此进行分析。根据我们的结果，这两种特性对NChDE都很敏感。我们表明，NChDE几乎完全是相对论性的，也就是说，在这两种特性的非相对论极限中它们几乎消失。我们计算了 和 上的NChDE，并根据这两种特性之间的相对论关系分析了它们之间的差异。利用该关系我们发现，电子核心机制是分子和自由原子中原子核屏蔽的NChDE的主要机制。NChDE对SR常数的影响比对屏蔽的影响小。然而，在RPA近似水平的相对论极化传播子形式体系内，它们对含重原子化合物中原子核的SR常数非常重要。HAt中的砹影响最大：点状模型下 = -9.95 kHz，类高斯模型下为 -50.10 kHz。必须包括相关效应，我们使用不同的密度泛函理论（DFT）方案来进行。PBE0泛函给出的结果最接近Br和I的实验值，不过LDA泛函给出的结果最接近氢的实验值。当应用不同的常用泛函时，At的SR常数的值从其RPA值降低到350 kHz至500 kHz之间。鉴于 和 上的NChDE在起源上大多是相对论性的，这些效应也依赖于电子关联。它们还与冈特电子-电子相互作用有非零依赖关系。
