c , which are related to the rotational constants as B α = h 4πc I -1 α (α = a, b, c). Since the rotation is frozen during the simulation, we may assume, that the principal axes of the molecule do not deviate significantly from the initial positions. Therefore there is no need for a reorientation of the molecule with respect to the reference structure. This procedure is denoted as mean inverse inertia tensor unoriented (MIITU).