This website was designed to serve two purposes:
Note: this website was formerly called the NIST Polycyclic Aromatic Hydrocarbon Structure Index to correspond with SP922. The new, shorter name is more convenient for web presentation, especially on mobile and touchscreen devices, one major focus of the 2015 database update.
All data in this database is derived from quantum chemistry computations. Other data that is more accurate, particularly from experimental sources, may be available elsewhere.
This web site incorporates all of the structures found in SP922 plus a number of additional related structures. More structures may be added over time based on user needs and feedback as well as our own interests. In addition to the 2d structures which are included in SP922, 3d structures have been produced using density functional theory (DFT) optimizations. The 3d structures may be freely rotated using the JSMol viewer incorporated into this web page. Also, the 2d and 3d structures may be downloaded for further use.
A great deal of additional information is being made available in the 2015 release, much of it for the first time. Links to PubChem and ChemSpider are included. IR and UV/Vis spectra are plotted, and nucleus independent chemical shift (NICS) values can be displayed at selected points on a 3d model. A number of chemical properties are taken from the output of the quantum chemistry calculations. Other property data from the ZENO (transport properties) and the EPA EPI Suite codes are included.
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 — 5000 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. This information is also available in NIST Special Publication 1186: Thermodynamic Properties of Polycyclic Aromatic Hydrocarbons by Thomas C. Allison and Donald R. Burgess Jr.
If you have any feedback on this database, please direct you comments via email to Tom Allison at NIST, thomas (dot) allison (at) nist (dot) gov.