Institut für Physikalische Chemie, Universität Mainz, D-55099 Mainz, Germany.
J Chem Phys. 2013 Aug 7;139(5):054105. doi: 10.1063/1.4816130.
A cost-effective treatment of scalar-relativistic effects on nuclear magnetic shieldings based on the spin-free exact-two-component theory in its one-electron variant (SFX2C-1e) is presented. The SFX2C-1e scheme gains its computational efficiency, in comparison to the four-component approach, from a focus on spin-free contributions and from the elimination of the small component. For the calculation of nuclear magnetic shieldings, the separation of spin-free and spin-dependent terms in the parent four-component theory is carried out here for the matrix representation of the Dirac equation in terms of a restricted-magnetically balanced gauge-including atomic orbital basis. The resulting spin-free four-component matrix elements required to calculate nuclear magnetic shieldings are then used to construct the corresponding SFX2C-1e Hamiltonian and its perturbed counterpart in the context of SFX2C-1e analytic derivative theory. To demonstrate the applicability of the approach, we report coupled-cluster calculations for prototypical problems such as the (17)O shieldings of transition-metal oxo complexes (MO4(2-), M = Cr, Mo, and W) and the (129)Xe shieldings of xenon fluorides (XeF2, XeF4, and XeF6).
提出了一种基于自旋自由精确双组分理论单电子变体（SFX2C-1e）的、对核磁共振屏蔽有成本效益的标量相对论效应处理方法。与四分量方法相比，SFX2C-1e 方案通过专注于无自旋贡献和消除小分量来提高计算效率。对于核磁共振屏蔽的计算，在此对母体四分量理论中的自旋自由和自旋相关项进行了分离，方法是使用受限磁平衡包含原子轨道基的狄拉克方程的矩阵表示。然后，使用所得的无自旋四分量矩阵元来构建相应的 SFX2C-1e 哈密顿量及其在 SFX2C-1e 解析导数理论背景下的受扰对应物。为了演示该方法的适用性，我们报告了协变簇计算，例如过渡金属氧络合物（MO4(2-), M = Cr、Mo 和 W）的（17）O 屏蔽和氙氟化物（XeF2、XeF4 和 XeF6）的（129）Xe 屏蔽的典型问题。
