thermNASA reference manual

The program expects control information in the file control_inp.ext specified on the command line. The full file name (including extension) must be typed. The following keywords can be placed in the control input to specify the list of temperatures, thermodata file name and formats, reactants and products of reaction, and rate constants for the forward reaction.

Comments

Any text from # or ! to the end of line in the control input is ignored as comments.

# thermEquil input for the reaction of A + B = C + D
! -- this is also a comment --

List of Temperatures

The control input file may contain any combination of the following three types of temperature specifications;

tempRange T_start T_end T_step
tempRecipRange numer start end step
tempList T_1 T_2 T_3 ...

See the reference manual for thermRead for details.

Reactants and Products

The control input file should specify the target reaction by the names of reactant species and product species via:

reactants reactant_1, reactant_2, ...
products product_1, product_2, ...

The reactant_1, reactant_1, ... are the names of reactants and product_1, product_1, ... are the names of products registered in the thermodata file. The inputs, 'thermodata', 'reactants', and 'products' can be placed in any order in the control input file.

Rate Constants for the Forward Reaction

This optional input beginning with 'forward_k' can be used to set the forward rate constants and requests the program to calculate the rate constants for the corresponding reverse reaction by using the equilibrium constants.

forward_k conc_unit energy_unit A n Ea

The conc_unit set the concentration unit used for the forward and/or reverse rate constants, if necessary, and must be either of 'mol/cm3' or 'molecule/cm3'. The energy_unit set the unit of activation energy, and must be either of 'cal/mol' or 'kelvin'. The remaining arguments, A, n, and Ea are the parameters A, n, and E_a for the modified Arrhenius expression of the forward rate constant, k_f = A Tⁿ exp(−E_a / RT).

Sample Control Input

The sample control input file ctr_eqonl.inp contains only three lines as shown below.

thermodata dataNOx.dat
reactants NO NO O2
products NO2 NO2

This is an example of minimal input. For this case, the default temperature list ('tempRang 300. 1500. 100.') will be used and calculation of reverse rate constants will not be performed.

More sophisticated sample control input file ctr_equil.inp contains temperature specifications and forward rate constant input as:

# sample control input for thermEquil

tempList 298.15
tempRecipRange 10000 11 33 1
tempRange 1000 2300 100
tempRange 2400 4800 200
tempRange 5000 6000 500

thermodata dataNOx.dat

reactants NO NO O2
products NO2 NO2

forward_k mol/cm3 cal/mol 1.19678e+09 0 -1053.22

The comment parts beginning with '#' and '!' as well as blank lines are ignored.

The results are written to a csv-format file, control_inp.csv. The output ctr_eqonl.csv from ctr_eqonl.inp looks like below. Since forward rate constant is not given, only the changes in the dimensionless thermodynamic functions, ΔH/RT, ΔS/R, ΔG/RT and the equilibrium constants, K_p and K_c are calculated. It should be noted that the concentration equilibrium constants are always reported in two concentration units (mol cm⁻³ and molecule cm⁻³). As a results, for the case of the reaction with the same number of reactants and products, the same dimensionless numbers will be reported at three columns (Kp/- and two Kc/- columns).

The contents of the output ctr_equil.csv from ctr_equil.inp are shown below. The forward rate constants (k_f) specified by the Arrhenius expression as well as the reverse rate constants (k_r) calculated from the forward ones and equilibrium constants are reported.