The zero-barrier model is simply an Arrhenius model with zero activation energy (E a = 0), leading to a reaction rate coefficient that is constant with temperature. A modified Arrhenius model, where the pre-exponential factor is assumed to be proportional to the temperature to a power, was not considered here as it required to fit three parameters using only six data points. This model would have given high uncertainty on the different parameters and would be more subject to overfitting.