Relativistic calculation of nuclear magnetic shielding tensor using the regular approximation to the normalized elimination of the small component. III. Introduction of gauge-including atomic orbitals and a finite-size nuclear model
Relativistic calculation of nuclear magnetic shielding tensor using the regular approximation to the normalized elimination of the small component. III. Introduction of gauge-including atomic orbitals and a finite-size nuclear model
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DOI：
10.1063/1.3028047
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发表时间：
2008-12-14
影响因子：
4.4
通讯作者：
Fukui, H.
中科院分区：
文献类型：
--
作者：
Hamaya, S.;Maeda, H.;Fukui, H.
采用小分量归一化消去法（SORA-NESC）的二阶正则近似，包含了度量算子的扰动项，对卤化氢中的核磁屏蔽张量进行了相对论性计算。该计算方案记为SORA-Met。SORA-Met计算得出各向异性，δ σ =sigma（平行）-sigma（垂直），对于太小的卤化氢中的卤素核。在NESC理论中，旋量的小分量通过算子sigma中心点pi U/2c与大分量结合，其中pi=p+A， U为非酉变换算子，c等于137.036 a.u.为光速。算子U依赖于导阶为c（-2）的矢量位势A（即系统中的磁扰动），而U的磁扰动项对导阶为c（-4）的系统的哈密顿算子和度规算子有贡献。结果表明，卤素核的δ σ较小与忽略了U-(0,U-1)微扰算子有关，U- (0,U-1)微扰算子与外磁场无关，与核磁偶极矩有关。本文还讨论了包括量规在内的原子轨道和有限尺寸核模型的引入。
The relativistic calculation of nuclear magnetic shielding tensors in hydrogen halides is performed using the second-order regular approximation to the normalized elimination of the small component (SORA-NESC) method with the inclusion of the perturbation terms from the metric operator. This computational scheme is denoted as SORA-Met. The SORA-Met calculation yields anisotropies, Delta sigma=sigma(parallel to)-sigma(perpendicular to), for the halogen nuclei in hydrogen halides that are too small. In the NESC theory, the small component of the spinor is combined to the large component via the operator sigma center dot pi U/2c, in which pi=p+A, U is a nonunitary transformation operator, and c congruent to 137.036 a.u. is the velocity of light. The operator U depends on the vector potential A (i.e., the magnetic perturbations in the system) with the leading order c(-2) and the magnetic perturbation terms of U contribute to the Hamiltonian and metric operators of the system in the leading order c(-4). It is shown that the small Delta sigma for halogen nuclei found in our previous studies is related to the neglect of the U-(0,U-1) perturbation operator of U, which is independent of the external magnetic field and of the first order with respect to the nuclear magnetic dipole moment. Introduction of gauge-including atomic orbitals and a finite-size nuclear model is also discussed.