The majority of TIES simulations, 74 out of 103, are performed with NAMD. The remaining 29 pairs are studied with OpenMM . The two MD engines were used to take advantage of the architectures of different supercomputers. We use NAMD on CPU-based ARCHER2 () and SuperMUC-NG (), and use OpenMM on the GPU partition of Summit (). Our previous studies have shown that, for the same molecular systems, consistent free energies are obtained not only from different supercomputers using the same MD engine -NAMD in this case , but also from different MD engines on different supercomputers -NAMD running on CPUs and OpenMM or pmemdGTI running on GPUs.