The surface kinetics input file lists the chemical reactions and rate parameters for the gas-surface and surface reactions occurring in the system of interest. There are a limited number of published reaction mechanisms involving surface chemistry, primarily in the fields of materials-processing and catalysis.

The Ansys Chemkin software allows surface reactions to be described at levels of complexity ranging from a single global reaction to detailed elementary reactions involving hundreds of steps. The use of lumped reactions is much more common in surface chemistry mechanisms than in gas-phase chemistry mechanisms. This reflects the much-smaller amount of fundamental kinetic data available for constructing reaction mechanisms. There is also less consensus in the community on how to describe surface species and reactions; a number of different naming conventions are in use. Surface reactions are generally not included in standard compilations of kinetic data.

Fundamental surface science studies, especially those done in ultra-high vacuum (UHV), can provide information on elementary reaction steps on surfaces such as adsorption or desorption rates. Although they generally do not include lists of reactions with rate constants, such studies provide valuable guidance in terms what constitutes a reasonable reaction rate, whether reactions show evidence of notable coverage dependencies, etc. The use of pairs of irreversible reactions can be advantageous when describing surface chemistry where experimental measurements may address the reaction in either direction. In contrast with surface reaction mechanisms involving detailed reactions, where some rates may be based on independent rate studies, reaction mechanisms composed of global reactions are derived primarily by fitting to experimental data.

The short supply of fundamental surface kinetics rate data means that those sections of reaction mechanisms include a relatively high percentage of estimated or fitted reaction rates. The sticking coefficient formulation in the Ansys Chemkin software facilitates estimating rates for gas-surface reactions.

For example, highly reactive "radical" species would be expected to have relatively high sticking coefficients (~0.001–1), while chemical species that are stable enough to ship in bottles would be expected to be much less reactive, with sticking coefficients in the 1 x 10^-9 – 1 x 10^-6 range.

Plasma simulations introduce additional complexities to the surface chemistry in the form of ion-assisted reactions and surface neutralization reactions. The subject of developing reaction mechanisms for plasma-surface interactions is included in the summary on plasma chemistry by Meeks and Ho [23].