Department of Chemistry, Oakland University, Rochester, Michigan48309, United States.
Material Science and Engineering Department, University of Michigan, Ann Arbor, Michigan48109, United States.
J Phys Chem A. 2023 Jan 12;127(1):46-56. doi: 10.1021/acs.jpca.2c06039. Epub 2022 Dec 20.
We present a systematic study of electron-correlation and relativistic effects in diatomic molecular species of the heaviest halogen astatine (At) within relativistic single- and multireference coupled-cluster approaches and relativistic density functional theory. We establish revised reference ab initio data for the ground states of At, HAt, AtAu, and AtO using a highly accurate relativistic effective core potential model and in-house basis sets developed for accurate modeling of molecules with large spin-orbit effects. Spin-dependent relativistic effects on chemical bonding in the ground state are comparable to the binding energy or even exceed it in At. Electron-correlation effects near the equilibrium internuclear separation are mostly dynamical and can be adequately captured using single-reference CCSD(T). However, bond elongation in At and, especially, AtO results in rapid manifestation of its multireference character. While useful for evaluating the spin-orbit effects on the ground-state bonding and properties, the two-component density functional theory lacks predictive power, especially in combination with popular empirically adjusted exchange-correlation functionals. This drawback supports the necessity to develop new functionals for reliable quantum-chemical models of heavy-element compounds with strong relativistic effects.
我们在相对论单和多参考耦合簇方法和相对论密度泛函理论中对最重卤族元素砹（At）的双原子分子物种进行了电子相关和相对论效应的系统研究。我们使用高度精确的相对论有效核势模型和为准确模拟具有大自旋轨道效应的分子而开发的内部基组，为 At、HAt、AtAu 和 AtO 的基态建立了修订的参考从头算数据。在基态中，自旋相关的相对论效应对化学键的影响与结合能相当，甚至在 At 中超过了结合能。在平衡核间分离处的电子相关效应主要是动力学的，可以使用单参考 CCSD(T) 充分捕捉。然而，At 中的键伸长，特别是 AtO 中的键伸长导致其多参考特征迅速显现。虽然对于评估基态键合和性质的自旋轨道效应有用，但双组分密度泛函理论缺乏预测能力，特别是与流行的经验调整交换相关泛函结合使用时。这一缺点支持了为具有强相对论效应的重元素化合物的可靠量子化学模型开发新泛函的必要性。
