Formulas used to calculate kf

[wittregr]

What are the formulas used to calculate kf? Please add this information to the documentation for kf.out and include the units kf will have for each formula.

[MaxRCohen]

Hi @mbkumar, looks like we still need this information. Could you please add it where the documentation says "1. Adsorption reaction:" and "2. Surface reaction:"?

[skasiraj]

The formulas used for gas and surface reactions are implemented by Cantera using the Arrhenius and Modified-Arrhenius forms. If this information is consistent with your experience we can update the documentation and close this issue.

• For surface reaction without sticking coefficients it uses this expression. Here A, b, and E_a are the modified Arrhenius parameters. If activation energy is defined as coverage dependent then a_k, mk, Ek, are the coverage dependencies from species k. For pMuTT generated input I am not sure if we ever use this form. If we do not provide values for a_k. m_k and E_k, then they will be set to a default of 0 and the expression reduced to the typical modified Arrhenius form.
• For sticking type reactions this is the expression for the forward rate constant. Where gamma_tot is the total molar site density, m is the sum of all the surface reactant stoichiometric coefficients, and W is the molecular weight of the gas phase species
• The The unit system is (kmol, m, s). The actual units depend on the reaction order and the dimensionality (surface or bulk).

[MaxRCohen]

To confirm, is the surface reaction term A equal to (k_BT/h)(1/gamma_tot^(m-1))? k_B is the Boltzman constant, h is Planck's constant, and the other terms are the same as in the adsorption section. For the adsorption section, is the lower case gamma equal to the sticking coefficient? If so, then these formulas are consistent with what I know for Chemkin and should be included in the documentation. However, @wittregr should confirm the coverage dependent formulation for the surface reactions since I less familiar with it.