With the advent of high performance computers new tools have become available to study grain boundary motion and related phenomena like recrystallization and grain growth. Already in the 1970s the structure and energy of low Σ grain boundaries had been computed and important information on the relaxed structure of coincidence boundaries was obtained (see Chapter 2) but the dynamics of grain boundaries could not be addressed with the computer power available at that time. Molecular-dynamics (MD) simulations are widely used to study the atomic-level behavior of GBs at ﬁnite temperatures. The method itself is nowadays well established in the ﬁeld of atomistic simulations. As early as the late 1950s  and early 1960s the ﬁrst MD simulations were performed and the basis of this method was established . During the following decades, reﬁnements of the MD method by introducing ﬁnite temperature thermostats [493, 494, 497, 498], progress in deriving sophisticated interatomic potentials [495, 496, 499] and extending the MD method by introducing the simulation box vectors as variables [500, 501] steadily increased the potential of the method.