Gas-Phase Thermochemistry of Iron Oxides and Hydroxides: Portrait of a Super-Efficient Flame Suppressant

Abstract

In the search for non-ozone-depleting Halon (CF3Br) replacements, several metals, including iron, have been identified as super-efficient flame suppressants. Although some thermochemical data exist for the species that are thought to be most important in iron's flame chemistry, a more complete and accurate characterization of the thermochemistry of iron oxides, hydrides, and hydroxides is required to improve kinetic flame models. In this investigation predicted enthalpies (Δrxn ) and free energies (Δrxn ) of the reactions of several FeOxHy species in methane flames are reported. Heats of formation (Δf ) for the FeOxHy species of interest are also recommended. The hybrid B3LYP density-functional method and the CCSD(T) coupled-cluster method are employed in conjunction with a relativistic effective core potential on the iron center and a valence triple-ζ basis on all atoms in order to characterize the relative energetics of the important species.