Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji-shi, Tokyo 192-0397, Japan.
J Chem Phys. 2010 May 7;132(17):174105. doi: 10.1063/1.3413529.
We presented a two-component relativistic quantum-chemical theory for magnetic shielding constants, which is based on the infinite-order Douglas-Kroll (IODK) transformation. Two-electron relativistic corrections were also generated using the IODK transformation, although negligibly small terms were discarded. The use of small-component basis functions was completely excluded from the present theory. We examined the combination of the levels of relativistic one- and two-electron terms and magnetic interaction terms using the first-order Foldy-Wouthuysen (FW1), the second-order Douglas-Kroll (DK2), and the infinite-order Douglas-Kroll (IODK) transformations, as well as the lowest-order (c(-2)) Breit-Pauli approximation. We calculated the magnetic shielding constants of several closed-shell atoms using the FW1, DK2, IODK, and Breit-Pauli Hamiltonians. The IODK Hamiltonian reproduced well the results calculated by the four-component Dirac-Fock-Coulomb theory: The maximum deviation is only about 2.2%. We found that the accuracy of the magnetic shielding constants is strongly affected by the relativistic treatments of one-electron magnetic interaction, while the effect of the two-component two-electron relativistic corrections is relatively small. We also discussed the picture change effect on magnetic operators.
我们提出了一种基于无穷阶 Douglas-Kroll（IODK）变换的双分量相对论量子化学磁屏蔽常数理论。尽管忽略了可以忽略的小项，但我们也使用 IODK 变换生成了双电子相对论修正。目前的理论完全排除了使用小分量基函数。我们使用一阶 Foldy-Wouthuysen（FW1）、二阶 Douglas-Kroll（DK2）和无穷阶 Douglas-Kroll（IODK）变换以及最低阶（c(-2)） Breit-Pauli 近似，研究了相对论单电子和双电子项以及磁相互作用项的组合。我们使用 FW1、DK2、IODK 和 Breit-Pauli 哈密顿量计算了几个闭壳层原子的磁屏蔽常数。IODK 哈密顿量很好地再现了四分量 Dirac-Fock-Coulomb 理论计算的结果：最大偏差仅约为 2.2%。我们发现，磁屏蔽常数的准确性强烈受到单电子磁相互作用的相对论处理的影响，而双分量双电子相对论修正的影响相对较小。我们还讨论了磁算符的图象变化效应。
