论文标题
评估标量相对论对卤素键合的影响和$σ$ - 孔特性的评估
Assessment of Scalar Relativistic Effects on Halogen Bonding and $σ$-Hole Properties
论文作者
论文摘要
卤素键（X键）是卤素原子与电子供体之间的非共价相互作用。通常，它通过卤素原子（所谓的$σ$孔）的正静电电位区域合理化。 X键强度随所涉及的卤素的原子数增加，因此对于较重的卤素，相对论的影响成为人们关注的问题。这对X键合复合物的量子化学描述构成了挑战。为了量化标量相对论效应（SRE）对相互作用能量和$σ$ - 孔特性，我们以几个X键合复合物及其卤代单体的完整基集限制进行了高度准确的耦合群集计算。 SRE与基集的效果相当。非层次论的计算通常将吸引力分别低于5％或23％，分别为溴化和碘化的复合物。违反直觉，对于无SRE的计算，键临界点处的电子密度比相对论的计算更大。 SRES产生较小，更平坦的$σ$孔。最后，我们在基础集中强调了弥漫函数的重要性，并为使用伪电势的基础集提供了定量论证，作为更严格的Douglas-kroll-kroll-Hess相对论理论的负担得起的替代方案。
Halogen bond (X-bond) is a noncovalent interaction between a halogen atom and an electron donor. It is often rationalized by a region of the positive electrostatic potential on the halogen atom, so-called $σ$-hole. The X-bond strength increases with the atomic number of the halogen involved, thus for heavier halogens, relativistic effects become of concern. This poses a challenge for the quantum chemical description of X-bonded complexes. To quantify scalar relativistic effects (SREs) on the interaction energies and $σ$-hole properties, we have performed highly accurate coupled-cluster calculations at the complete basis set limit of several X-bonded complexes and their halogenated monomers. The SREs turned to be comparable in magnitude to the effect of basis set. The nonrelativistic calculations typically underestimate the attraction by up to 5% or 23% for brominated and iodinated complexes, respectively. Counter-intuitively, the electron densities at the bond critical points are larger for SRE-free calculations than for the relativistic ones. SREs yield smaller, flatter, and more positive $σ$-holes. Finally, we highlight the importance of diffuse functions in the basis sets and provide quantitative arguments for using basis sets with pseudopotentials as an affordable alternative to a more rigorous Douglas-Kroll-Hess relativistic theory.
