First, the model tries to predict where an atom would land on a surface and its rate at particular environmental conditions, such as temperature and vapor pressure. In order to land on a surface, atoms have to overcome the so-called activation energy barrier. The frequency of passing through the activation barrier can by calculated by the Arrhenius equation:
where A is the thermal frequency of molecular vibration,  is the activation energy, k is the Boltzmann constant and T is the absolute temperature.