Usage

Rate Coefficients

Crane accepts rate coefficients in three formats: constant, function (denoted by brackets, {}), and tabulated (denoted by EEDF (file_name)).

An example of the usage of each is shown below.

 `species = 'e Ar* Ar+ Ar Ar2+'`
 `reaction_coefficient_format = 'rate'`
 `file_location = 'file_example'`

 `equation_variables = 'Te'`
 `sampling_variable = 'reduced_field'`
 `reactions = 'e + Ar -> e + e + Ar+          : EEDF (Ar_ionization.txt)`
              `Ar2+ + e -> Ar* + Ar           : {8.5e-7*((Te/1.5)*11600/300.0)^(-0.67)}`
              `Ar* + Ar* -> Ar2+ + e          : 6.0e-10'`

Tabulated Rate Coefficients

In the tabulated case, all rate coefficients should be stored in individual files. Crane will search for the file named in parenthesis in a location designated by the file_location input parameter. In this case, Crane will search for the file 'Ar_ionization.txt' in the file_example/ directory. If no file_location is provided, Crane will search in the same directory as the input file. A subset of Ar_ionization.txt is shown below. The left column is the reduced electric field value (E/N, in units of V m^2), and the right is the rate coefficient value in units of m^3/s:

1.0000e-22 0.0000e+00 4.3410e-22 0.0000e+00 7.6820e-22 0.0000e+00 1.1020e-21 0.0000e+00 1.4360e-21 0.0000e+00 1.7710e-21 3.4190e-15 2.1050e-21 5.0440e-15 2.4390e-21 6.7110e-15 2.7730e-21 8.3640e-15 3.1070e-21 9.9600e-15 3.4410e-21 1.1450e-14 3.7750e-21 1.2780e-14 4.1090e-21 1.3910e-14 4.4430e-21 1.4860e-14 4.7780e-21 1.5620e-14 5.1120e-21 1.6230e-14

Tabulated rate coefficients are assumed to be in a two column format separated by spaces or tabs. The first column should be reduced electric field or mean electron energy, and the second column should be the rate coefficient value. If using Crane alone as a 0D chemical reaction network solver, the variable used in the first column should be specified by the 'sampling_variable' input parameter. The provided sampling_variable should be an auxiliary or nonlinear variable in the input file. In this case, an auxiliary variable named 'reduced_field' is used. If using Zapdos, the sampling variable is assumed to be mean electron energy. No sampling_variable parameter is required.

Note: unit consistency is left to the user. If the rate coefficients are tabulated in terms of cm^3/s, the user should ensure that all rate coefficients, densities, and transport coefficients are in units of cm as well.

Cross Section Data

Crane does not currently include the capability of deriving rate coefficients from cross section data. The current method for using cross sections is utilizing Bolsig+, Bolos, or some equivalent electron energy distribution function solver to derive rate coefficients and electron transport coefficients from cross sections.

Description at the following link:

GEC_2018_crane_workshop