Chemkin-II inputs
A. Miyoshi

Chemkin-II inputs

  This document describes the format of the chemkin-II input files.


Chemkin Interpreter input

  For the complete description of the Chemkin Interpreter input file, see the following document.
  • 'Chemkin-II: A Fortran Chemical Kinetics Package for the Analysis of Gas-Phase Chemical Kinetics,' R. J. Kee, F. M. Rupley, and J. A. Miller, Sandia Report, SAND89-8009B (1995).

Input-file structure

Elements block

  List all the elements contained in the species (that is, atoms and molecules) to be considered.   Place the symbols of elements delimited by a space (may be multiple spaces) or a line-feed between 'ELEMENTS' and 'END'.   For element symbols, either of upper, lower, or mixed case (e.g. 'AR' 'ar' or 'Ar') is allowed but it must be case-sensitively identical with that used in the thermodata.
  H O C N HE

Species block

  List all the species (atoms and molecules) to be considered. Similarly to the elements, place the names of the species delimited by spaces or a line-feed between 'SPECIES' and 'END'.
  The species name cannot exceed 16 charactors, and the first letter should not be numeric, '+', nor '='.   It does not need to be a chemcal formula such as CH4' or 'C2H6', but should be identical with the name in the therm.dat or thermo block. (For example, formyl radical in the default therm.dat is named as 'HCO', not 'CHO')
  When the chemical formula is not enough to identify the species, refer to The Chemkin Thermodynamic Data Base (SAND87-8215B). For example, there are three species with C3H4 chemcal formula in therm.dat. They are named as 'C3H4', 'C3H4C', and 'C3H4P' corresponding to allene, cyclopropene, and propyne, respectively.

Thermo block

  This block is an option.   When the all species in the Species Block are registered in the therm.dat, and if you choose to use them, this block can be skipped.
  Place the coefficients for thermodynamic functions in four-lines fixed-format per one species between 'THERMO' and 'END'.   The format is identical with that of therm.dat and refer to the Thermodata file (therm.dat) section for details.
  With Chemkin, thermodynamic data should be given for all the species considered. Since thermodynamic functions are required to calculate the rate constants for reverse reactions (See Reactions block) and the heat balance.   In an exceptional case, when no reverse reaction should be considered and the temperature change can be negligible (which may no be rare as the condition of the laboratory kinetic experiments ...), thermodynamic data is not necessary.   However, even for the isothermic calculation without any reversible reaction, Chemkin requests the thermodata.   In such a case, one may register dummy (may be totally inaccurate) thermodata to avoid the error of Chemikin.   For this case, do not modify the therm.dat with dummy data, but register it in here in the Thermo block.

Reactions block

  List reaction equations with rate parameters for the reactions to be considered in this block.   The 'REACTIONS' or 'END' statement should appear as an independent line, and one reaction should be described in a line.   A reaction should be described in the order of the reaction equation and rate parameters.

Reaction equation

Rate constants and unit

Reactions involving third-body

Senkin inputs

  For the complete description of the Senkin input file format, See the following document.
  • 'SENKIN: A Fortran Program for Predicting Homogeneous Gas Phase Chemical Kinetics with Sensitivity Analysis,' A. E. Lutz, R. J. Kee, and J. A. Miller, Sandia Report, SAND87-8248 (1995).

Sample input

Sensitivity option

Problem selection

The keywords below may be placed at any line between the problem selection keyword and 'END'.

Initial conditions

Integration control


MIX0D exntended options

ICEN options

CGME options

PRGV option

PRGT option

Senkin binary-CSV coverter input

Example input


CONC OUTPUT CONTROL (one or two line[s])


Rxn Contrib tool input


Thermodynamic data

  For the complete description of the thermodynamic data format, See the following document.
  • 'The Chemkin Thermodynamic Data Base,' R. J. Kee, F. M. Rupley, and J. A. Miller, Sandia Report, SAND87-8215B (1994).