This website was designed to serve two purposes: 1) serve as a modern replacement for the original web site serving the content of NIST Special Publication 922: Polycyclic Aromatic Hydrocarbon Structure Index 2) serve thermochemical data derived in the publication 'First Principles Prediction of Enthalpies of Formation for Polycyclic Aromatic Hydrocarbons and Derivatives,' Thomas C. Allison and Donald R. Burgess Jr., manuscript in preparation. Using procedures fully described in the publication referenced above, the enthalpy of formation has been derived and is available on this website in the temperature range 0 - 6000 K. These data are computed from the results of an energy-extrapolated B3LYP/cc-pVDZ optimization and frequency calculation. The enthalpy of formation is computed within the ideal gas, rigid rotor, harmonic oscillator approximation, and an empirical correction based on a chemical group scheme is applied. Please see the literature citation for details.