This system has a very small QM subsystem (15 atoms) combined with a large MM subsystem (139,495 atoms). Therefore, it is expected that the QM/MM part plays a major role performance-wise. Results of BLYP-based CP-MD benchmarks are shown in Figure . As expected, QM/MM contributions are especially prominent here, where they take up to 82% of the time on a single node, as shown in Figure . Thanks to the efficient parallelization and excellent scaling of the QM/MM contributions computed by MiMiC, the time per time step can be brought down to approximately 0.45 seconds using 960 cores (see Fig. ). Further scaling is stalled due the small size of the FFT grid (240 3 ) and the small number of orbitals (16), which limits the benefits of task groups in CPMD. Moreover, there are issues due to the serial integrator that have been pointed out above and, in addition, the time spent on communication between CPMD and GROMACS is non-negligible at this core count. These bottlenecks appear mostly due to the small size of the QM part compared to the substantial extent of the MM subsystem. The detailed breakdown of the time spent computing each of the contributions at the scaling limit is shown in Figure .