The FAST-IAST theory introduced by O Brian and Myers (1985) and Moon and Tien (1987). The FAST IAST is a method to calculate the multicomponent adsorption equilibria. The used isotherm should have analytical possibility to calculate the spreading pressure .
For calculation insert the following parameters: number of components N, Langmuir constants for every component, gas pressure, fraction of every component.
The result is a matrix of adsorbed concentrations (check the dimensions of the used presure and Langmuir constants).