where T is the temperature, and k B is the Boltzmann constant. The pre-exponential factor k 0,i is estimated based on the harmonic transition state theory from the vibration modes at the initial state (IS) and transition state (IS) of process i. This assumption is only valid as long as the IS does not differ much from the TS. Due to the substantial entropy reduction at the deposition of a species from the gas phase onto a metal surface, the reaction rate for non-activated adsorption processes k ad is more accurately calculated by k ad n,B (T, p) = Sn,B (T )