Polycyclic aromatic hydrocarbons (PAHs) are key reference materials for the validation and parameterization of computationally cost-effective procedures such as density functional theory (DFT), semiempirical molecular orbital theory, and molecular mechanics. We obtain accurate heats of formation (ΔH_f,298) for 20 PAHs with up to 18 carbon atoms by means of the explicitly correlated W1-F12 thermochemical procedure. The heats of formation are obtained via atomization reactions and quasi-isodesmic reactions involving CH₄, C₂H₄, and C₆H₆ for which accurate experimental ΔH_f,298 values are available from the active thermochemical tables (ATcT) network. We show that for large PAHs, the differences between W1-F12 heats of formation obtained from atomization and quasi-isodesmic reactions increase with the size of the system and range between 1.7 (C₇H₈) and 8.9 (chrysene, C₁₈H₁₂) kJ mol^–1. This suggests that atomization reactions should be used with caution for obtaining heats of formation for medium-sized systems even when highly accurate thermochemical procedures (such as W1-F12 theory) are used. For eight PAH compounds (toluene, indene, acenaphthylene, biphenyl, diphenylmethane, anthracene, pyrene, and chrysene), our best theoretical values agree with the best experimental values to within ∼1 kJ mol^–1; for six additional systems (indane, naphthalene, biphenylene, acenaphthene, phenanthrene, and m-terphenyl), the agreement between theory and experiment is good with deviations ranging between 2 and 4 kJ mol^–1. However, for four systems (p-terphenyl, fluorene, pyracene, and pyracyclene), our best W1-F12 values suggest that the experimental ΔH_f,298 values should be revised by significant amounts ranging from 6.5 and 24.4 kJ mol^–1.

中文翻译：

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多环芳烃的准确形成热：从高水平的 Ab Initio 视角

多环芳烃 (PAH) 是验证和参数化计算成本效益程序的关键参考材料，例如密度泛函理论 (DFT)、半经验分子轨道理论和分子力学。我们通过明确关联的 W1-F12 热化学程序获得了多达 18 个碳原子的 20 种多环芳烃的准确形成热 (Δ H _f,298 )。生成热是通过涉及 CH ₄、C ₂ H ₄和 C ₆ H _{6 的}原子化反应和准等向反应获得的，其精确的实验Δ H _f,298值可从活动热化学表 (ATcT) 网络中获得。我们表明，对于大 PAH，从原子化和准等向反应获得的 W1-F12 形成热之间的差异随着系统的大小而增加，范围在 1.7 (C ₇ H ₈ ) 和 8.9 (chrysene, C ₁₈ H ₁₂ ) 千焦摩尔^–1. 这表明，即使使用高度准确的热化学程序（如 W1-F12 理论），也应谨慎使用雾化反应来获得中型系统的形成热。对于八种 PAH 化合物（甲苯、茚、苊、联苯、二苯甲烷、蒽、芘和芘），我们的最佳理论值与最佳实验值一致，在 ∼1 kJ mol ^–1以内；六个附加的系统（茚满，萘，亚联苯基，苊，菲，和米-三联苯），理论和实验之间的协议是与偏差2和千焦mol之间4测距良好^-1。然而，对于四个系统 ( p-三联苯、芴、并苯和吡喃环），我们最好的 W1-F12 值表明实验 Δ H _f,298值应该在 6.5 和 24.4 kJ mol ^–1范围内进行大量修正。