A test case with a single copy of the new Martini 3 cholesterol model in vacuum was added to the battery of single-point tests defined in the martini_openmm library 2 (). This test system for single-point calculations compares energies and forces extracted from simulations carried out with GROMACS version 2021.2 compiled in double precision and OpenMM version 7.5 in double precision mode with the "Reference" platform . The results for the total potential energy were considered to be in agreement, as the absolute error was less than 10 -3 kJ/mol and the relative error less than 10 -5 . As for the forces, they were also considered in agreement since all absolute errors after setting OpenMM forces on virtual sites to zero are within 10 -4 kJ/mol/nm, and all relative errors are less than 10 -5 . The cutoff values used in this study were selected to fall within the range of differences observed between the implementations of the same CHARMM force field in different simulation engines such as CHARMM, NAMD, and GROMACS , as discussed in the openmm_martini release . A further evaluation of the OpenMM implementation of the new cholesterol model was performed by simulating DPPC:CHOL and POPC:CHOL mixtures with increasing cholesterol concentrations, and the results compared with those obtained with GROMACS. These results will be discussed in a following section, however, both MD engine implementations yielded similar results.