基于规范和DLPNO的G4（MP2）XK启发的复合波函数方法针对大型和化学多样性训练集进行参数化：它们是否比双杂交DFT更准确和/或更稳健？
Canonical and DLPNO-based G4(MP2)XK-inspired composite wavefunction methods parametrized against large and chemically diverse training sets: Are they more accurate and/or robust than double hybrid DFT?
摘要：
使用大型且化学多样的GMTKN 55基准作为训练集，用于参数化类似于G4（MP2）XK理论的复合波函数热化学方案（Chan等人，JCTC 2019，15，4478-4484）。即使在重新参数化后，GMTKN 55 WTMAD 2 G4（MP2）-XK的（加权平均绝对偏差，类型2）实际上劣于最好的梯级-4 DFT泛函wB 97 M-V。通过将MP2部分的基组增加到def 2-QZVPPD，我们能够以适度的成本大幅提高性能（如果进行RI-MP2近似），其中用于该G4（MP2）-XK-D方法的WTMAD 2现在与更好的5阶泛函相当（尽管成本更高）。然而，具有缩放的MP3/def 2-TZVPP中间步骤的三层方法导致G4（MP3）-D方法，其甚至显著优于最好的双杂交体wB 97 M（2）和revDSD-PBEP 86-D4。用三重zeta基组而不是分裂价基组评估CCSD（T）分量仅产生适度的进一步改进，这与计算成本的急剧增加不相称。G4（MP3）-D和G4（MP2）- XK-D分别比它们的对应物G4和G4（MP2）具有约40%的更好的WTMAD 2，具有相似或更低的计算成本：详细的比较表明，差异在于由于基组不完整性误差而导致的更大的分子。E2/ {T，Q}外推和CCSD（T）/def 2-TZVP步骤提供了仅用三个拟合参数的高精度G4-T方法。在MP2中使用KS轨道导致G4（MP3| KS）-D方法，该方法完全消除了CCSD（T）步骤，并且没有比标度MP3更昂贵的步骤;这表明了进一步改进双杂交密度泛函方法的途径。G4-T-DLPNO是一种在DLPNO-CCSD（T）级评估MP2后校正的变体，其精度接近G4-T，但适用于更大的系统。
英文摘要：
The large and chemically diverse GMTKN55 benchmark was used as a training set for parametrizing composite wave function thermochemistry protocols akin to G4(MP2)XK theory (Chan et al, JCTC 2019, 15, 4478-4484). Even after reparametrization, the GMTKN55 WTMAD2 (weighted mean absolute deviation, type 2) for G4(MP2)-XK is actually inferior to that of the best rung-4 DFT functional, wB97M-V. By increasing the basis set for the MP2 part to def2-QZVPPD, we were able to substantially improve performance at modest cost (if an RI-MP2 approximation is made), with WTMAD2 for this G4(MP2)-XK-D method now comparable to the better rung-5 functionals (albeit at greater cost). A three-tier approach with a scaled MP3/def2-TZVPP intermediate step, however, leads to a G4(MP3)-D method that is markedly superior to even the best double hybrids wB97M(2) and revDSD-PBEP86-D4. Evaluating the CCSD(T) component with a triple-zeta, rather than split-valence, basis set yields only a modest further improvement that is incommensurate with the drastic increase in computational cost. G4(MP3)-D and G4(MP2)- XK-D have about 40% better WTMAD2, at similar or lower computational cost, than their counterparts G4 and G4(MP2), respectively: detailed comparison reveals that the difference lies in larger molecules due to basis set incompleteness error. An E2/ {T,Q} extrapolation and a CCSD(T)/def2-TZVP step provided the G4-T method of high accuracy and with just three fitted parameters. Using KS orbitals in MP2 leads to the G4(MP3|KS)-D method, which entirely eliminates the CCSD(T) step and has no steps costlier than scaled MP3; this shows a path forward to further improvements in double-hybrid density functional methods. G4-T-DLPNO, a variant in which post-MP2 corrections are evaluated at the DLPNO- CCSD(T) level, achieves nearly the accuracy of G4-T but is applicable to much larger systems.
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