4. Validation of the geometric model

Once the geometric model and the growth mechanism have been established, the model can be fully validated using the step-down method. Indeed, by performing a series of decays of a thermodynamic variable, temperature or partial pressure, at the same degree of advancement (or reaction time), and applying the equation (24) , different values of the ratio φ _after /φ _before can be obtained for different values of this variable. So, without the need for any additional model or assumption, variations in the surface reactivity of growth with one of the thermodynamic variables are determined to within a multiplicative factor. These same variations...