+However, the trajectory of the carbon atom is no longer proceeding in the \hkl(1 1 0) plane.
+The orientation of the new dumbbell configuration is transformed from \hkl<0 0 -1> to \hkl<0 -1 0>.
+Again one bond is broken while another one is formed.
+As a last migration path, the defect is only changing its orientation.
+Thus, it is not responsible for long-range migration.
+The silicon dumbbell partner remains the same.
+The bond to the face-centered silicon atom at the bottom of the unit cell breaks and a new one is formed to the face-centered atom at the forefront of the unit cell.
+Todo: \hkl<1 1 0> to \hkl<1 0 0> and bond-centerd configuration (in progress).
+Todo: \hkl<1 1 0> to \hkl<0 -1 0> (rotation of the DB, in progress).
+Todo: Comparison with classical potential simulations or explanation to only focus on ab initio calculations.
+
+Since the starting and final structure, which are both local minima of the potential energy surface, are known, the aim is to find the minimum energy path from one local minimum to the other one.
+One method to find a minimum energy path is to move the diffusing atom stepwise from the starting to the final position and only allow relaxation in the plane perpendicular to the direction of the vector connecting its starting and final position.
+No constraints are applied to the remaining atoms in order to allow relaxation of the surrounding lattice.
+To prevent the remaining lattice to migrate according to the displacement of the defect an atom far away from the defect region is fixed in all three coordinate directions.
+However, it turned out, that this method tremendously failed applying it to the present migration pathways and structures.
+Abrupt changes in structure and free energy occured among relaxed structures of two successive displacement steps.
+For some structures even the expected final configurations were never obtained.
+Thus, the method mentioned above was adjusted adding further constraints in order to obtain smooth transitions, either in energy as well as structure is concerned.
+In this new method all atoms are stepwise displaced towards their final positions.
+Relaxation of each individual atom is only allowed in the plane perpendicular to the last individual displacement vector.
+The modifications used to add this feature to the VASP code and a short instruction on how to use it can be found in appendix \ref{app:patch_vasp}.
+Due to these constraints obtained activation energies can effectively be higher.
+Todo: To refine the migration barrier one has to find the saddle point structure and recalculate the free energy of this configuration with a reduced set of constraints.