Benchmark Thermochemistry of Polycyclic Aromatic Hydrocarbons

Area of Science:

• Computational Chemistry
• Physical Chemistry
• Quantum Chemistry

Background:

• Polycyclic Aromatic Hydrocarbons (PAHs) are crucial in various chemical processes.
• Accurate determination of their enthalpies of formation is essential for thermodynamic studies.
• Existing experimental data for larger PAHs is often limited or uncertain.

Purpose of the Study:

• To accurately calculate the standard enthalpies of formation for 30 PAHs.
• To establish reliable reference values for selected PAHs.
• To validate a cost-effective computational method for predicting PAH enthalpies.

Main Methods:

• Utilized the DLPNO-CCSD(T1)/CBS computational method.
• Employed isodesmic-type reactions with small, well-characterized reference species.
• Compared calculated values with available experimental data and other high-level calculations.

Main Results:

• Calculated enthalpies of formation for 30 PAHs with high accuracy.
• Recommended reference standard enthalpies of formation for 13 PAHs.
• Achieved agreement within 2 kJ/mol between calculated and experimental values for reference compounds.
• Demonstrated the accuracy of the DLPNO-CCSD(T)/CBS method for large PAHs like coronene.

Conclusions:

• The DLPNO-CCSD(T1)/CBS method with isodesmic reactions provides accurate enthalpies of formation for PAHs.
• The recommended reference values for 13 PAHs can serve as benchmarks for theoretical method development.
• This approach offers a reliable and cost-effective way to study large PAHs.