In preparing GRI-Mech 3.0, thermodynamic sensitivities were computed for all targets. These apply in the calculations of all reverse rate coefficients in the mechanism, and thus to experimental conditions where partial equilibria obtain.

Target model computations were repeated with the a6 coefficients of the NASA polynomials (and hence H(298)/R) increased(+) and decreased(-) by 503.22K, i.e., the enthalpies are altered by +/-= 1 kcal/mole. The thermodynamic sensitivities graphed on the target pages are given by the formula:

where T is the temperature of the experiment. This corresponds to

(One may multiply the reported sensitivity by 1000/RT to obtain S' = d(logF)/d(logH) in kcal/mole units.)

Few targets show any significant sensitivity to the free energies (enthalpies) of the species, and considering our evaluations of the uncertainties (even for the radicals), the enthalpies are not chosen as optimization variables. The one exception is the HCN enthalpy, which was selected and varied as an optimization variable for the HCN oxidation targets NFR1, NFR2, NFR3, and NF7.