where x 1 = x(a 0 , 0) and x 2 = x(0, a 0 ). In the description of the diffusion processes, the NN are taken into account. The resulting mesh structures for the respective diffusion mechanisms are given in Fig. . Nudged Elastic Band calculations were carried out using the developed reactive force field potential to determine the respective activation energies. From the vibration modes ν i of the initial and transition state, the pre-exponential factor k 0 was obtained following