Laboratory of Molecular Structure and Dynamics, Institute of Chemistry, Eötvös University , H-1518 Budapest 112, P.O. Box 32, Hungary.
J Phys Chem A. 2014 Jan 23;118(3):646-54. doi: 10.1021/jp411652u. Epub 2014 Jan 8.
We test the accuracy of various standard, explicitly correlated F12, and composite ab initio methods with different correlation consistent basis sets for high-dimensional potential energy surface (PES) developments, thereby providing a practical guidance for reaction dynamics studies. Relative potential energies are computed at 15 geometries covering the energy range and configuration space of chemical importance for each of the six prototypical polyatomic reactions, X + CH4 → HX + CH3 [X = F, O, Cl] and X(-) + CH3Y → Y(-) + CH3X [X/Y = F/F, OH/F, F/Cl]. The average accuracies of the Hartree-Fock and MP2 methods are 1500-8000 and 400-1000 cm(-1), respectively. The standard CCSD(T) method provides errors of 900-1400 and 250-450 cm(-1) with aug-cc-pVDZ and aug-cc-pVTZ basis sets, respectively. The explicitly correlated CCSD(T)-F12 method reduces the corresponding errors to about 200 and 100 cm(-1); thus, we recommend using the F12 methods for PES developments. For F12 computations, the cc-pVnZ-F12 [n = D and T] basis sets usually, but not always, perform better than the corresponding aug-cc-pVnZ bases. We do not find clear preference between the F12a and F12b methods for PES developments. Composite methods are advocated instead of standard CCSD(T) because for example, one can obtain CCSD(T)/aug-cc-pVnZ quality results on the expense of MP2/aug-cc-pVnZ [n = T and Q] computations. The post-CCSD(T), the core correlation, and the scalar relativistic effects are found to be ∼100, 80-130, and 10-50 cm(-1), respectively. The all-electron CCSD(T)/aug-cc-pCVnZ relative energies differ from the complete-basis-set limit by about 1000, 300, 100, and 50 cm(-1) for n = D, T, Q, and 5, respectively.
我们测试了各种标准、显式相关 F12 和从头计算方法在高维势能面（PES）开发中的准确性，这些方法使用不同的相关一致基组，从而为反应动力学研究提供了实际指导。在每个六原型多原子反应的能量范围和构型空间内的 15 个几何形状上计算相对势能，X + CH4 → HX + CH3 [X = F、O、Cl] 和 X(-) + CH3Y → Y(-) + CH3X [X/Y = F/F、OH/F、F/Cl]。HF 和 MP2 方法的平均精度分别为 1500-8000 和 400-1000 cm(-1)。标准 CCSD(T) 方法分别使用 aug-cc-pVDZ 和 aug-cc-pVTZ 基组，得到的误差为 900-1400 和 250-450 cm(-1)。显式相关 CCSD(T)-F12 方法将相应的误差降低到约 200 和 100 cm(-1)；因此，我们建议在 PES 开发中使用 F12 方法。对于 F12 计算，cc-pVnZ-F12 [n = D 和 T] 基组通常但并不总是优于相应的 aug-cc-pVnZ 基组。我们没有发现 F12a 和 F12b 方法在 PES 开发中的明显偏好。我们提倡使用组合方法而不是标准 CCSD(T)，因为例如，人们可以在牺牲 MP2/aug-cc-pVnZ [n = T 和 Q] 计算的代价下获得 CCSD(T)/aug-cc-pVnZ 质量结果。后 CCSD(T)、核心相关和标量相对论效应分别约为 100、80-130 和 10-50 cm(-1)。全电子 CCSD(T)/aug-cc-pCVnZ 相对能量与完全基组极限相差约 1000、300、100 和 50 cm(-1)，分别对应于 n = D、T、Q 和 5。
