Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA.
J Chem Phys. 2018 Apr 14;148(14):144108. doi: 10.1063/1.5023750.
An atomic mean-field (AMF) spin-orbit (SO) approach within exact two-component theory (X2C) is reported, thereby exploiting the exact decoupling scheme of X2C, the one-electron approximation for the scalar-relativistic contributions, the mean-field approximation for the treatment of the two-electron SO contribution, and the local nature of the SO interactions. The Hamiltonian of the proposed SOX2CAMF scheme comprises the one-electron X2C Hamiltonian, the instantaneous two-electron Coulomb interaction, and an AMF SO term derived from spherically averaged Dirac-Coulomb Hartree-Fock calculations of atoms; no molecular relativistic two-electron integrals are required. Benchmark calculations for bond lengths, harmonic frequencies, dipole moments, and electric-field gradients for a set of diatomic molecules containing elements across the periodic table show that the SOX2CAMF scheme offers a balanced treatment for SO and scalar-relativistic effects and appears to be a promising candidate for applications to heavy-element containing systems. SOX2CAMF coupled-cluster calculations of molecular properties for bismuth compounds (BiN, BiP, BiF, BiCl, and BiI) are also presented and compared with experimental results to further demonstrate the accuracy and applicability of the SOX2CAMF scheme.
本文报道了一种基于精确双组分理论（X2C）的原子平均场（AMF）自旋轨道（SO）方法，充分利用了 X2C 的精确解耦方案、标量相对论贡献的单电子近似、处理双电子 SO 贡献的平均场近似以及 SO 相互作用的局域性质。所提出的 SOX2CAMF 方案的哈密顿量包括单电子 X2C 哈密顿量、瞬时双电子库仑相互作用以及源自原子的球平均狄拉克-库仑哈特里-福克计算的 AMF SO 项；不需要分子相对论双电子积分。对于包含周期表中元素的一系列双原子分子的键长、谐振频率、偶极矩和电场梯度的基准计算表明，SOX2CAMF 方案为 SO 和标量相对论效应提供了平衡的处理，并且似乎是应用于含重元素系统的有前途的候选方案。还提出了铋化合物（BiN、BiP、BiF、BiCl 和 BiI）的 SOX2CAMF 耦合簇分子性质计算，并与实验结果进行了比较，进一步证明了 SOX2CAMF 方案的准确性和适用性。
