Virtually every Cantera simulation involves one or more phases of matter. Depending on the calculation being performed, it may be necessary to evaluate thermodynamic properties, transport properties, and/or homogeneous reaction rates for the phase(s) present. In problems with multiple phases, the properties of the interfaces between phases, and the heterogeneous reaction rates at these interfaces, may also be required.

Before the properties can be evaluated, each phase must be defined, meaning that the models to use to compute its properties and reaction rates must be specified, along with any parameters the models require. For example, a solid phase might be defined as being incompressible, with a specified density and composition. A gaseous phase for a combustion simulation might be defined as an ideal gas consisting of a mixture of many species that react with one another via a specified set of reactions.

For phases containing multiple species and reactions, a large amount of data is required to define the phase, since the contribution of each species to the thermodynamic and transport properties must be specified, and rate information must be given for each reaction. While this could be done directly in an application program, a better approach is put the phase and interface definitions in a text file that can be read by the application, so that a given phase model can be re-used for other simulations.

This guide describes how to write such files to define phases and interfaces for use in Cantera simulations. Section Working with Input Files contains a summary of some basic rules for writing input files, a discussion of how they are processed, and of how errors are handled. In Section Phases and their Interfaces, we will go over how to define phases and interfaces, including how to import species and reactions from external files. Then in Elements and Species and Reactions, we’ll look in depth at how to specify the component parts of phase and interface models—the elements, species, and reactions.