Arrhenius-like reaction rate constant equations are calculated as follows:

\[ Ae^{(\frac{-E_a}{k_bT})}(\frac{T}{D})^B(1.0+E*P) \]

where \(A\) is the pre-exponential factor (# \((\mbox{cm}^{-3})^{-(n-1)}\mbox{s}^{-1}\)), \(n\) is the number of reactants, \(E_a\) is the activation energy (J), \(k_b\) is the Boltzmann constant (J/K), \(D\) (K), \(B\) (unitless) and \(E\) ( \(Pa^{-1}\)) are reaction parameters, \(T\) is the temperature (K), and \(P\) is the pressure (Pa). The first two terms are described in Finlayson-Pitts and Pitts (2000) [Finlayson-Pitts2000] . The final term is included to accomodate CMAQ EBI solver type 7 rate constants.

Input data for Arrhenius equations has the following format:

{
  "type" : "ARRHENIUS",
  "A" : 123.45,
  "Ea" : 123.45,
  "B"  : 1.3,
  "D"  : 300.0,
  "E"  : 0.6E-5,
  "time unit" : "MIN",
  "reactants" : {
    "spec1" : {},
    "spec2" : { "qty" : 2 },
    ...
  },
  "products" : {
    "spec3" : {},
    "spec4" : { "yield" : 0.65 },
    ...
  }
}

The key-value pairs reactants, and products are required. Reactants without a qty value are assumed to appear once in the reaction equation. Products without a specified yield are assumed to have a yield of 1.0.

Optionally, a parameter C may be included, and is taken to equal \(\frac{-E_a}{k_b}\). Note that either Ea or C may be included, but not both. When neither Ea or C are included, they are assumed to be 0.0. When A is not included, it is assumed to be 1.0, when D is not included, it is assumed to be 300.0 K, when B is not included, it is assumed to be 0.0, and when E is not included, it is assumed to be 0.0. The unit for time is assumed to be s, but inclusion of the optional key-value pair time unit = MIN can be used to indicate a rate with min as the time unit.