PAH335 – A diverse database of highly accurate CCSD(T) isomerization energies of 335 polycyclic aromatic hydrocarbons

Abstract

<p>We obtain CCSD(T) isomerization energies for 335 polycyclic aromatic hydrocarbons by means of the G4(MP2) thermochemical protocol. We use this large and diverse dataset of isomerization energies for identifying a-priori indicators for energetic instability and benchmarking DFT and semiempirical methods. We find that dipole moments above 1.0 D, HOMO-LUMO gaps below 2.0 eV, and q<i>_neg,avg</i> values below –0.06 e indicate energetic instability. Surprisingly, the local density approximation SVWN5 method attains a mean absolute deviation (MAD) of merely 3.8 kJ/mol and outperforms many functionals from higher rungs of Jacob's Ladder. PBE0-D4 is the best performer with a MAD of 2.8 kJ/mol.</p>