In CPMD, planes along the x-axis are distributed across MPI processes. Optimal scalability is in principle obtained with one plane per MPI process, as demonstrated in previous studies. We analyzed the scaling behaviour by varying the number of nodes and employing hybrid MPI/OpenMP parallelization. Different numbers of OpenMP threads were tested, and the corresponding number of MPI processes was adjusted accordingly (Table ). The scaling was evaluated based on the average time per time step, calculated over the initial 20 Born-Oppenhemier MD steps, using a Berendensen thermostat and a time step of 0.48 fs. As shown in Fig. , the best performance was achieved for 75 nodes and 5 OpenMP threads.