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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Benchmarking Compound Methods (CBS-QB3, CBS-APNO, G3, G4, W1BD) against the Active Thermochemical Tables: A Litmus Test for Cost-Effective Molecular Formation Enthalpies
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Benchmarking Compound Methods (CBS-QB3, CBS-APNO, G3, G4, W1BD) against the Active Thermochemical Tables: A Litmus Test for Cost-Effective Molecular Formation Enthalpies

机译：对照有效热化学表的基准化合物方法（CBS-QB3，CBS-APNO，G3，G4，W1BD）：对成本有效的分子形成焓的石蕊试验

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The theoretical atomization energies of some 45 CxHyOz molecules present in the Active Thermochemical Tables compilation and of particular interest to the combustion chemistry community have been computed using five composite model chemistries as titled, The species contain between 1-8 "heavy" atoms, and a few are conformationally diverse with up to nine conformers. The enthalpies of formation at 0 and 298.15 K are then derived via the atomization method and compared against the recommended values. In general, there is very good agreement between our averaged computed values and those in the ATcT; those for 1,3-cydopentadiene exceptionally differ considerably, and we show from isodesmic reactions that the true value for 1,3-cyclopentadiene is closer to 134 kJ mol(-1) than the reported 101 kJ mol(-1). If one is restricted to using a single method, statistical measures indicate that the best methods are in the rank order G3 approximate to G4 > W1BD > CBS-APNO > CBS-QB3. The CBS-x methods do on average predict Delta H-f(circle minus)(298.15 K) within approximate to 5 kJ mol(-1) but are prone to occasional lapses. There are statistical advantages to be gained from using a number of methods in tandem, and all possible combinations have been tested. We find that the average formation enthalpy coming from using CBS-APNO/G4, CBS-APNO/G3, and G3/G4 show lower mean signed and mean unsigned errors, and lower standard and root-mean-squared deviations, than any of these methods in isolation. Combining these methods also leads to the added benefit of providing an uncertainty rooted in the chemical species under investigation, hi general, CBS-APNO and W1BD tend to underestimate the formation enthalpies of target species, whereas CBS-QB3, G3, and G4 have a tendency to overestimate the same. Thus, combining CBS-APNO with a G3/G4 combination leads to an improvement in all statistical measures of accuracy and precision, predicting the ATcT values to within 0.14 +/- 4.21 kJ mol(-1), thus rivalling "chemical accuracy" (+/- 4.184 kJ mol(-1)) without the excessive cost associated with higher-level methods such as W1BD.
机译：活性热化学表格编辑中存在的以及燃烧化学界特别感兴趣的约45个CxHyOz分子的理论雾化能，是通过使用五个标题为的复合模型化学来计算的，该物质包含1至8个“重”原子，并且几乎没有构象多样性，最多有9个构象体。然后通过雾化方法得出0和298.15 K下的形成焓，并与推荐值进行比较。通常，我们的平均计算值与ATcT中的计算值之间有很好的一致性; 1,3-环戊二烯的那些相差极大，我们从等渗反应中发现，1,3-环戊二烯的真实值比所报道的101 kJ mol（-1）更接近134 kJ mol（-1）。如果仅限于使用一种方法，则统计指标表明最佳方法的排名顺序为G3，近似于G4> W1BD> CBS-APNO> CBS-QB3。 CBS-x方法确实平均预测Delta H-f（圆减去）（298.15 K）在大约5 kJ mol（-1）范围内，但容易偶尔出现误差。串联使用多种方法可以获得统计上的优势，并且已经测试了所有可能的组合。我们发现，与任何其他方法相比，使用CBS-APNO / G4，CBS-APNO / G3和G3 / G4产生的平均形成焓显示出更低的平均有符号误差和平均无符号误差，以及更低的标准偏差和均方根偏差孤立的方法。结合使用这些方法还可以带来额外的好处，即可以提供一种根源于所研究化学物种的不确定性。一般而言，CBS-APNO和W1BD往往低估了目标物种的形成焓，而CBS-QB3，G3和G4具有倾向于高估相同的趋势。因此，将CBS-APNO与G3 / G4组合相结合可提高准确性和精确度的所有统计量，预测ATcT值在0.14 +/- 4.21 kJ mol（-1）之内，从而可与“化学准确性”相媲美（ +/- 4.184 kJ mol（-1）），而不会产生与W1BD等高级方法相关的过多成本。

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