This work addresses the pathological behavior of the energetics of dimethyl sulfoxide and related sulfur-containing compounds by providing the computational benchmark energetics of R₂E₂ species, where R = H/CH₃ and E = O/S, with bent and pyramidal geometries using state-of-the-art methodologies. These 22 geometries were fully characterized with coupled-cluster with single, double, and perturbative triple excitations [CCSD(T)], second-order Møller–Plesset perturbation theory (MP2), and 22 density functional theory (DFT) methods with 8, 12, and 12, respectively, correlation consistent basis sets of double-, triple-, or quadruple-ζ quality. The relative energetics were determined at the MP2 and CCSD(T) complete basis set (CBS) limits using 17 basis sets up to sextuple-ζ and include augmented, tight-d, and core–valence correlation consistent basis sets. The relative energies of oxygen-/sulfur-containing compounds exhibit exceptionally slow convergence to the CBS limit with canonical methods as well as significant basis set dependence. CCSD(T) with quadruple-ζ basis sets can give qualitatively incorrect relative energies. Explicitly correlated MP2-F12 and CCSD(T)-F12 methods dramatically accelerate the convergence of the relative energies to the CBS limit for these problematic compounds. The F12 methods with a triple-ζ quality basis set give relative energies that deviate no more than 0.41 kcal mol⁻¹ from the benchmark CBS limit. The correlation consistent Composite Approach (ccCA), ccCA-TM (TM for transition metals), and G3B3 deviated by no more than 2 kcal mol⁻¹ from the benchmark CBS limits. Relative energies for oxygen-/sulfur-containing systems fully characterized with DFT are quite unreliable even with triple-ζ quality basis sets, and 13 out of 45 combinations fortuitously give a relative energy that is within 1 kcal mol⁻¹ on average from the benchmark CCSD(T) CBS limit for these systems.

中文翻译：

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DMSO 的奇特案例：CCSD(T)/CBS(aQ56+d) 基准和 DFT 研究

这项工作通过提供 R ₂ E ₂物种的计算基准能量学来解决二甲基亚砜和相关含硫化合物能量学的病理行为，其中 R = H/CH ₃和 E = O/S，使用最先进的方法具有弯曲和金字塔几何形状。这 22 种几何结构完全表征为具有单、双和微扰三重激发的耦合簇 [CCSD(T)]、二阶 Møller-Plesset 微扰理论 (MP2) 和 22 种密度泛函理论 (DFT) 方法，其中 8、图 12 和 12 分别是双、三或四倍 ζ 质量的相关一致基组。相对能量学是在 MP2 和 CCSD(T) 完整基组 (CBS) 限制下使用 17 个基组确定的，最高可达 sextuple-ζ，包括增强的、紧密的d，以及核价相关性一致的基组。使用经典方法以及显着的基组依赖性，含氧/硫化合物的相对能量表现出异常缓慢的收敛到 CBS 极限。带有四重ζ基组的CCSD(T)可能会给出定性不正确的相对能量。显式相关的 MP2-F12 和 CCSD(T)-F12 方法显着加速了这些有问题的化合物的相对能量收敛到 CBS 限制。具有三重 ζ 质量基组的 F12 方法给出的相对能量与基准 CBS 限制的偏差不超过 0.41 kcal mol ^-1。相关性一致的复合方法 (ccCA)、ccCA-TM（过渡金属的 TM）和 G3B3 偏差不超过 2 kcal mol ^-1来自基准 CBS 限制。用 DFT 完全表征的含氧/硫系统的相对能量即使使用三重 ζ 质量基组也相当不可靠，并且 45 种组合中有 13 种偶然给出的相对能量与基准平均相差在 1 kcal mol ^-1以内这些系统的 CCSD(T) CBS 限制。