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

Abstract

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 qneg,avg 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.