In this section, we present benchmarks of the MiMiC-based QM/MM implementation using CPMD and GROMACS as the QM and MM engines, respectively, for a set of systems with different QM and MM subsystem sizes. We investigate the scalability using the parallelization strategies presented in Section 2.4, namely the low-level grid distributions using MPI, the higher-level task grouping scheme, and the fine-level OpenMP threading. Here it should be noted that when we in the following refer to task groups in CPMD, this corresponds to using the CP group implementation as presented in Ref. 9. We also include a comparison of timings and scaling performance to the existing tight-coupling QM/MM implementation in the CPMD program.