Working With Input Files

As covered in the tutorials (Python and Matlab), all calculations in Cantera require an input file to describe the properties of the relevant phase(s) of matter.

The required input files can be provided via one of three methods:

  • Use one of the pre-existing input files provided with Cantera
  • Convert a pre-existing mechanism from Chemkin (CK) format to Cantera (CTI) format
  • Create your own CTI file, either from scratch (not recommended) or by editing an existing file

The first two options will suffice for a majority of Cantera users. Advanced users may, however, need to edit an existing CTI file in order to define additional species, reactions, or entirely new phases. Even if you need to create an entirely new CTI file, it is still advisable to start from an existing file, to cut down on syntax errors.

Whenever you edit a CTI file, it is highly advised that you begin by copying the existing file and saving it under a new name, before editing the new file. Editing a file under its original name can easily lead to errors, if one forgets that this file does not represent the original mechanism.

CTI files distributed with Cantera

Several reaction mechanism files in the CTI format are included in the Cantera distribution, including ones that model natural gas combustion (gri30.cti), high-temperature air (air.cti), a hydrogen/oxygen reaction mechanism (h2o2.cti), some pure fluids in the liquid-vapor region (liquidvapor.cti), and a few surface reaction mechanisms (such as ptcombust.cti, diamond.cti, etc.), among others. Under Windows, these files may be located in C:\Program Files\Cantera\data depending on how you installed Cantera and the options you specified. On a Unix/Linux/macOS machine, they are usually kept in the data subdirectory within the Cantera installation directory.

Please see the tutorials for Python and Matlab for instructions on how to import from these pre-existing files.

Converting or Creating New CTI Files

If you want to model a phase not available in the CTI files distributed with Cantera, you will need to either procure a new CTI file (there are a limited number of CTI files available on the web), or create a new one.

There are two primary options for creating a new CTI file:

Conversion from Chemkin
Convert a Chemkin-formatted (‘CK’) file to the CTI input format.
Create a new CTI file
Create a completely new mechanism, by defining new species, phases, and/or reactions.

Understanding CTI Syntax

For any of these options (adapting an external CTI file, converting from CK, or creating a new CTI file), it can be helpful to understand the CTI syntax requirements. Clearly, anyone writing directly in the CTI format must conform to these standards. However, even when importing an externally-provided CTI file or converting from CK format, understanding the CTI file syntax can help diagnose and correct any errors (although many/most of the CK conversion errors will be related to errors in the CK syntax formatting).

CTI Syntax Tutorial
This tutorial covers the details of the CTI format and its syntax