Quasirelativistic theory for magnetic shielding constants. II. Gauge-including atomic orbitals and applications to molecules
Quasirelativistic theory for magnetic shielding constants. II. Gauge-including atomic orbitals and applications to molecules
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DOI：
10.1063/1.1528934
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发表时间：
2003-01-15
影响因子：
4.4
通讯作者：
Nakatsuji, H
中科院分区：
文献类型：
--
作者：
Fukuda, R;Hada, M;Nakatsuji, H
本文将基于Douglas-Kroll-Hess变换的磁屏蔽常数准相对论理论推广到含重元素的分子系统。规范，包括原子轨道方法是适应准相对论性哈密顿量，允许原点无关的计算。本理论适用于卤化氢的质子和卤素磁屏蔽常数和Hg-199磁屏蔽常数和二卤化汞和卤化甲基汞的化学位移。虽然磁相互作用项的相对论修正对质子磁屏蔽常数的影响很小，但这种修正是重卤素和汞的磁屏蔽常数的重原子移位的主要来源。相对论计算中汞屏蔽常数的基组依赖性很大，使用相对论方法优化的基函数来正确描述相对论效应非常重要。磁相互作用项的相对论修正对于汞和卤素的相对论效应强耦合的二卤化汞是非常重要的。如果没有这种修正，我们得到的结果是完全不正确的。二卤化汞的Hg-199化学位移来源于重卤素的自旋轨道相互作用。在卤化甲基汞中，重卤素的顺磁屏蔽项以及自旋轨道相互作用主导了Hg-199化学位移。(C)2003年，美国物理学会。
Quasirelativistic theory of magnetic shielding constants based on the Douglas-Kroll-Hess transformation of the magnetic potential presented in a previous paper is extended to molecular systems that contain heavy elements. The gauge-including atomic orbital method is adapted to the quasirelativistic Hamiltonian to allow origin-independent calculations. The present theory is applied to the proton and halogen magnetic shielding constants of hydrogen halides and the Hg-199 magnetic shielding constants and chemical shifts of mercury dihalides and methyl mercury halides. While the relativistic correction to the magnetic interaction term has little effect on the proton magnetic shielding constants, this correction is a dominant origin of the heavy atom shifts of the magnetic shielding constants of heavy halogens and mercury. The basis set-dependence of mercury shielding constants is quite large in the relativistic calculation; it is important to use the basis functions that are optimized by the relativistic method to properly describe the relativistic effect. The relativistic correction to the magnetic interaction term is quite important for mercury dihalides in which the relativistic effects from mercury and halogen are strongly coupled. Without this correction, we obtain quite incorrect results. The origin of the Hg-199 chemical shifts in mercury dihalides is the spin-orbit interaction from heavy halogens. In methyl mercury halides, the paramagnetic shielding term as well as the spin-orbit interaction from heavy halogens dominates the Hg-199 chemical shifts. (C) 2003 American Institute of Physics.