Karton Amir
School of Science and Technology, University of New England, Armidale, New South Wales 2351, Australia.
J Phys Chem A. 2025 Jun 26;129(25):5692-5699. doi: 10.1021/acs.jpca.5c02680. Epub 2025 Jun 12.
The Born-Oppenheimer (BO) approximation is fundamental to computational chemistry because it drastically simplifies the time-independent Schrödinger equation, making calculations for molecular systems computationally feasible. Accurate determination of the diagonal Born-Oppenheimer correction (DBOC) is essential for achieving benchmark accuracy in high-level thermochemical applications. Here, we establish the DBOC200HC database, consisting of 200 structurally diverse hydrocarbons with up to 18 carbon atoms (e.g., triamantane (CH)), including aliphatic, aromatic, antiaromatic, cyclic, noncyclic, and caged systems. Reference DBOCs are determined near the coupled-cluster singles and doubles complete basis set limit (CCSD/CBS) using additivity schemes based on HF/cc-pVQZ and CCSD/cc-pVnZ (n = D, T) calculations. Given the computational expense associated with CCSD/CBS calculations for large hydrocarbons, it is important to develop reliable yet computationally economical approximations. Several such approaches are assessed using the DBOC200HC database. While scaled Hartree-Fock methods offer limited improvement, methods incorporating first-order Møller-Plesset perturbation theory (MP1) perform significantly better. Specifically, calculating the DBOC at the MP1/cc-pVDZ level of theory and scaling the MP1 correlation component (Δ = - ) by an empirical factor of 1.5447 yields the best balance between accuracy (RMSD = 0.026 kJ/mol) and computational cost (practically the same cost as HF/cc-pVDZ). This exceptionally low RMSD suggests that highly accurate DBOCs for use in high-level thermochemical protocols can be obtained via the scaled MP1 approach, without resorting to computationally more demanding levels of theory such as MP2 or CCSD. To validate our results, we further test the empirical methods optimized over the DBOC200HC database on an independent database of 12 larger hydrocarbons, including systems like dodecahedrane (CH).
玻恩-奥本海默（BO）近似对于计算化学至关重要，因为它极大地简化了不含时薛定谔方程，使得分子体系的计算在计算上可行。准确确定对角玻恩-奥本海默校正（DBOC）对于在高级热化学应用中实现基准精度至关重要。在此，我们建立了DBOC200HC数据库，该数据库由200种结构多样的烃类组成，碳原子数最多为18个（例如金刚烷（CH）），包括脂肪族、芳香族、反芳香族、环状、非环状和笼状体系。参考DBOC是在耦合簇单双激发完全基组极限（CCSD/CBS）附近，使用基于HF/cc-pVQZ和CCSD/cc-pVnZ（n = D，T）计算的加和方案确定的。鉴于对于大型烃类进行CCSD/CBS计算的计算成本，开发可靠且计算经济的近似方法很重要。使用DBOC200HC数据库评估了几种此类方法。虽然缩放的哈特里-福克方法改进有限，但包含一阶莫勒-普莱塞特微扰理论（MP1）的方法表现明显更好。具体而言，在MP1/cc-pVDZ理论水平计算DBOC，并将MP1相关分量（Δ = - ）按经验因子1.5447缩放，可在精度（均方根偏差 = 0.026 kJ/mol）和计算成本（实际上与HF/cc-pVDZ成本相同）之间取得最佳平衡。这种极低的均方根偏差表明，通过缩放的MP1方法可以获得用于高级热化学协议的高精度DBOC，而无需诉诸计算要求更高的理论水平，如MP2或CCSD。为了验证我们的结果，我们在一个由12种更大烃类组成的独立数据库上进一步测试了在DBOC200HC数据库上优化的经验方法，该数据库包括十二面体烷（CH）等体系。
