Entirely different surface reaction mechanisms (that is, with different surface and bulk phases and species, and different surface reactions) can be specified in the same Surface Kinetics input file through the use of multiple materials. At the beginning of each separate portion of the input file corresponding to a given material, the user may include a line with the keyword MATERIAL followed by an optional slash-delimited material name. If no name for the material is supplied, a default name, MATERIALn, will be substituted, where n is the number of the material (for example, MATERIAL2 for the second material given in an input file).