Sun Shichao, Stetina Torin F, Zhang Tianyuan, Hu Hang, Valeev Edward F, Sun Qiming, Li Xiaosong
Department of Chemistry, University of Washington, Seattle, Washington 98195, United States.
Department of Chemistry, Virginia Tech, Blacksburg, Virginia 24061, United States.
J Chem Theory Comput. 2021 Jun 8;17(6):3388-3402. doi: 10.1021/acs.jctc.1c00137. Epub 2021 May 24.
Four-component Dirac-Hartree-Fock is an accurate mean-field method for treating molecular systems where relativistic effects are important. However, the computational cost and complexity of the two-electron interaction make this method less common, even though we can consider the Dirac-Hartree-Fock Hamiltonian the "ground truth" of the electronic structure, barring explicit quantum electrodynamical effects. Being able to calculate these effects is then vital to the design of lower scaling methods for accurate predictions in computational spectroscopy and properties of heavy element complexes that must include relativistic effects for even qualitative accuracy. In this work, we present a Pauli quaternion formalism of maximal component and spin separation for computing the Dirac-Coulomb-Gaunt Hartree-Fock ground state, with a minimal floating point operation count algorithm. This approach also allows one to explicitly separate different spin physics from the two-body interactions, such as spin-free, spin-orbit, and spin-spin contributions. Additionally, we use this formalism to examine relativistic trends in the periodic table and analyze the basis set dependence of atomic gold and gold dimer systems.
四分量狄拉克 - 哈特里 - 福克方法是一种精确的平均场方法，用于处理相对论效应显著的分子体系。然而，两电子相互作用的计算成本和复杂性使得该方法不太常用，尽管我们可以将狄拉克 - 哈特里 - 福克哈密顿量视为电子结构的“基本事实”，但不包括明确的量子电动力学效应。因此，能够计算这些效应对于设计低尺度方法至关重要，这些方法用于在计算光谱学以及必须包含相对论效应才能获得定性准确性的重元素配合物性质的精确预测中。在这项工作中，我们提出了一种用于计算狄拉克 - 库仑 - 冈特哈特里 - 福克基态的最大分量和自旋分离的泡利四元数形式，以及一种最小浮点运算计数算法。这种方法还允许人们从两体相互作用中明确分离出不同的自旋物理，例如无自旋、自旋 - 轨道和自旋 - 自旋贡献。此外，我们使用这种形式来研究元素周期表中的相对论趋势，并分析原子金和金二聚体体系对基组的依赖性。
