where ν 0 is the attempt frequency, or the number of attempted jumps within unit time, and includes both successful jumps that can lead to macroscopic diffusion and unsuccessful ones. ∆G m is the Gibbs free energy of activation, k B is the Boltzmann constant, T is the absolute temperature, ∆S m is the activation entropy, and ∆H m is the activation enthalpy (this is also called the activation energy or activation barrier and denoted E a ). Substituting ν in eq. 1, we obtain.